ASME Early Career Technical Journal 2011 ASME Early Career Technical Conference, ASME ECTC November 4 – 5, Atlanta, Georgia USA

DEVELOPMENT AND TESTING OF A DIAMOND BRAIDED EYE SPLICE

Caitlin Plunket, Austin Yuill, and David Branscomb, M.S. Auburn University Auburn, Alabama, USA

Chad Rodekohr, PhD Presbyterian College Clinton, South Carolina, USA

ABSTRACT To make ropes more useable, many people add knots. A rope with a conventional eye splice termination is said to lose However, knots cause the rope to lose much of its strength. ten percent of its original strength [1]. The purpose of this This loss of strength is due to a more concentrated area of strain research was to determine if an eye splice produced on a [3]. A special kind of knot that allows the rope to retain more of braiding machine would be subject to the same loss in strength its strength is the splice. Splices make a more permanent encountered in conventional splices. Braided rope made at the fastening than knots and spread the stress through a larger area same speed and braid angle is compared to a braided eye splice. than a knot [3]. Yet, commonly used splices do not allow the The spliced ropes were made with sixteen Vectran® yarns rope to retain all of its original strength. around a cotton core. The splices were tested on a mechanical For example, a commonly used splice known as a testing machine and each splice compared to a rope made with buried eye splice is made by threading the free end of a rope the same specifications. Many designs were attempted back through the middle [1]. As the rope is pushed through including jamming the braid and allowing the splice to itself, an eye is formed. When this splice is under tension, the incorporate two to five revolutions (helical interlacements) after rope and splice act like a Chinese finger trap. This means that the splice was made. The braids in the jammed state were the rope acts like the finger trap and gets tighter under tension observed to fail within the spliced region. The splices preventing the splice or “finger” from being pulled out [1]. The consisting of two revolutions pulled out of the rope while being buried eye splice yields a breaking strength of ninety percent of tested. However, splicesincluding three revolutions with the the rope’s ultimate strength [1]. braiding point constantly pulled back proved to be a best design The purpose of this experimental work was to prove among those tested. The average loss of strength of this design that a braided spliced rope could maintain the strength of rope ranged from six to nine percent demonstrating an improvement made to the same specifications. The braided eye splice is in tensile properties over the conventional eye splice compared to the rope strength of an unaltered braided rope. It termination. The tensile failure of these splices does not occur is believed that a rope with a splice can lose up to ten percent of in the spliced section suggesting that full rope strength is its original strength [1]. This experiment proved that, if made maintained. Furthermore, the tensile failure is believed to be a correctly, a spliced rope can maintain the rope strength. holding defect, as it is observed to occur on the capstan holding the free end of the rope. VECTRAN ® SYNTHETIC ROPE The fiber used to make the braided eye splices was INTRODUCTION Vectran® which is a multifilament yarn spun from liquid Rope has many uses today from materials handling crystal polymer [4]. “Pound for pound Vectran® fiber is five and marine to aerospace to sports. Evidence of short handmade times stronger than steel and ten times stronger than aluminum ropes dates back to prehistoric cultures [2]. These early ropes [4].” The unique properties of Vectran ® such as high strength, were made by twisting natural fibers. However as the shipping high abrasion resistance, minimal moisture absorption, and high and marine industry expanded, longer and stronger ropes were impact resistance would allow for a more versatile and durable needed [2]. Eventually, ropes came to be made from higher splice. quality materials such as nylon and polyester. Today, some ropes are still twisted, but many are braided.

ASME 2011 Early Career Technical Journal - Vol. 10 99

Table 1.Typical ropes are made from Nylon and Polyester. Vectran® is a good substitute as it has unique and desirable qualities as shown in this table. Properties Vectran® Nylon Polyester Tensile 3200 MPa 400-870 450-850MPa Strength MPa Elongation 3.3-3.7% 18-45% 25% at Break Melting >400 °C 160-260 252-292 °C Point °C Water 0.2% 3.8% 0.2-0.5% Absorption Figure 2. The diamond braid used during this experiment. Density 1.4 g/cm3 1.15 g/cm3 1.38 g/cm3 In a diamond braid, the yarns go over one and under adjacent yarns. In a regular braid, the yarns go over two and under two. Table 1 compares Vectran® to Nylon and Polyester which are commonly used for making ropes. The table shows The braiding point of the splice is determined by the that Vectran® has the most desirable qualities one would want distance from the braiding machine (see Figure 3). The braid when manufacturing a spliced rope like high tensile strength angle is determined by the carrier speed and the take up speed and a low percentage of elongation at break. as shown in the equation below:

!!!! BRAID ARCHITECTURE ∝= 2!"#$!% ! Biaxial braid is the most basic and common form of where n is the carrier speed (the speed of the braiding two-dimensional (2-D) braided structures, composed of yarns machine), v is the take up speed, and Dm is the diameter of the interlacing in opposite directions. Among biaxial architectures, mandrel or core [6].The further the braiding point is from the various repeating patterns may be produced (see Figure 2). machine, the smaller the braid angle is (see Figures 4 and 5). Terminology of these patterns depends on industry and The braiding point is said to be in a jammed state or “jammed” application as textile and composite industries use different when the diameter of the braid will decrease no more as seen in names [5]. The most common repeat patterns are 1/1, 2/2, and Figure 4 [7]. In other words, the braided structure is under 3/3, where each yarn traverses according to the pattern sufficient tension that no other crimp exchange occurs. Crimp description over and under adjacent yarns [5]. The repeating exchange is the process by which a system of interlaced yarns pattern is determined by which carriers are utilized during the reaches equilibrium when under tension [7]. In this experiment, braiding operation. For the splices produced in this work, a it was found that the highest strength results were experienced sixteen-yarn, diamond braid was used. The bobbin carriers by the specimens with a braiding point that was “pulled back” (Packages) used to create this braid are seen in Figure 1. In a about two feet from the braiding machine. This suggests that diamond braid, each yarn travels over and under adjacent yarns the location where the braiding (interlacing) began did not start in the repeating pattern (see Figure 2). until the yarns were two feet from the braiding machine as shown in Figure 3.

Figure 3. When the braiding point is pulled back, the braid angle increases in size. When the braiding point is Figure 1. This figure shows the bobbin carrier jammed, the braid angle is as small as possible allowing configuration (Packages) on the braiding machine. The no more room for the diameter to decrease. red and yellow circles are loaded in order to produce a sixteen-yarn, diamond braid.

ASME 2011 Early Career Technical Journal - Vol. 10 100

Figure 4. The braid angle of a splice in a jammed state is very large causing the braid to be very tight.

Figure 5. The braid angle of a splice that is not jammed is smaller than that of one in a jammed state causing the braid to be more open, and it allows more room for the braid to elongate under tension.

IMPACT OF WORK Splices are a way to terminate the end of a rope and make a useful connection to do work. They can be used for sports, towing, and tethers as well as in many other engineering Figure 6. Braiding machine and speed controlled take-up applications. This experiment explored the strength of a novel machine during manufacturing [9]. splice and proved that a spliced rope can maintain more than ninety percent of the strength as compared to un-spliced rope. The new, braided splice explored in this paper is incorporated into the rope using a braiding machine. This design allows for a stronger splice which is unable to be pulled out under tension. Under testing, the braided splice design that was found to yield the highest strength never failed within the spliced region. A stronger splice made from rope means that they can be used for heavier loads, and they would not have to be replaced as often because they would be more durable.

EXPERIMENTAL DETAILS

The experiment was carried out using a custom- designed servo-actuated take-up machine attached to a Wardwell Horizontal 32 carrier braiding machine (Figure 6). A desktop computer was used for the motion control (Figure 7). Figure 7. The experimental take-up machine motion The speed-controlled take-up machine of Figure 7 control system, including (top row, left to right) computer, replaced the geared capstan originally designed for the braiding motion control card/breakout board, encoder on braiding machine. It is a 3 axis computer controlled take-up system, machine shaft, (second row) servo-amplifier, DC servo- including two brushless DC servo motors, and one AC Servo motor, (third row) DC servo-amplifier, DC servo-motor. Motor, and braiding machine shaft mounted encoder, (third row) DC servo-amplifier, DC [8]. LabVIEW 8.2 custom motion control programs, a personal computer with 4 axis motion control card, a universal motion interface [8]. The motion controller provides fully programmable motion control for up to four independent or coordinated axes of motion. Three computer controlled servo- axes include the capstan, variable pitch traverse, and spool allow for precision in sample manufacture.

ASME 2011 Early Career Technical Journal - Vol. 10 101

MANUFACTURING The splices were manufactured using a Wardwell Horizontal 32 carrier braiding machine with a computer controlled take-up system. However, part of the manufacturing process requires a manual operation. When making the splice, the thimble is held in place as shown in Figure 9, and the rope is wound onto the seventeenth bobbin.

Figure 10. The number of revolutions within the splice are determined by how many revolutions the seventeenth bobbin makes around the braiding machine.

The splices were made by braiding sixteen Vectran® yarns around a cotton core. The braids were made using sixteen bobbins in the form of a diamond braid. One foot of braided rope was made before it was wound on a seventeenth bobbin which rotated clockwise around the braiding machine, see Figure 9 for detail. Figure 8 shows how a thimble was placed where the eye of the splice would be to ensure a uniform eye size before the rope was wound back onto seventeenth the bobbin. The number of revolutions the bobbin made around the Figure 8. A thimble is used to manufacture splices with braiding machine equaled the number of revolutions in the uniformly sized eyes. splice. Figure 10 illustrates how a splice would look with one, two, three, or four revolutions. Once the desired number of revolutions was reached, the rope from the bobbin was cut about an inch from the end of the splice, and the seventeenth bobbin was removed. Then, the braiding process continued to produce approximately four feet to ensure enough length for testing. After each set of splices was made, using the same material and machine parameters “plain” rope was made for the comparison tests. This rope was also tested to find its maximum load, and the test results were compared to that of the spliced ropes.

DESIGN PROCESS The first step in the experiment was determining how many revolutions are required to produce a stable splice and prevent slipping while tested. The next step was determining whether or not the braid in the splice and the rope should be made with the braiding point jammed (braids in jammed state are inherently stable) or pulled back.

Figure 9. In order to braid the splice back into the rope, it is attached to a seventeenth bobbin on the braiding machine. This seventeenth bobbin is removed once the desired number of revolutions is achieved.

Figure 11. The jammed two revolution splices consistently failed at the end of the splice due to the jamming. Because of the jamming, the splice was unable to elongate any further and failed where the jamming ended.

ASME 2011 Early Career Technical Journal - Vol. 10 102

The first set of tests used splices with two revolutions. The braiding point of the splice was jammed, and the braiding point of the rope was pulled back. The samples in this group failed at the end of the splice like in Figure 11 because of the jamming. These resulted in a 22.5 percent loss of strength. Another set of two-revolution splices were made with the braiding point pulled back for the splice and the braid, but these splices pulled out during testing. Next, one three-revolution splice, one four-revolution splice, and one five-revolution splice were made with the braiding point continually pulled back to see how many revolutions were needed to keep the splice from pulling out. The three-revolution braid proved to be approximately as strong as the four or five revolution splices. A few more sets of the three-revolution splices were made with the same specifications and tested. The three-revolution splices proved to be the best design for a strong splice.

TESTING All of the splices and the “plain” ropes for comparison were tested with the Instron® model 5565 mechanical testing Figure 13.Testing setup on the Instron® for the “plain” machine. A five kilo-Newton load cell was used, and the rope. Both ends of this rope are wrapped around an specimens were pulled with a crosshead speed of twelve inches upper capstan and a lower capstan. per minute. Figure 12 shows how the splices were loaded onto the Instron®. The plain rope was loaded in a similar way except RESULTS AND DISCUSSIONS there was another capstan to hold it from the top instead of a The jammed splices consistently failed in the jammed pin as shown in Figure 13. portion of the splice due to high stress within the braid. The two-revolution splices with the braiding point pulled back always pulled out during testing. The three-revolution braid held the same strength as the four-revolution and five- revolution splices. Therefore, the three-revolution splice with the braiding point pulled back proved to be the best option for a functional splice according to the results of this experiment.

Table 2. Each set of splices was compared to a set of un- spliced or “plain” rope to find the percentage of strength lost. Splice Set #1 Set #2 Set #3 Specimen Maximum Maximum Maximum Load (lbf) Load (lbf) Load (lbf)

1 726.54 774.07 734.80

2 751.11 712.61 777.49

3 688.88 670.56 751.55

Figure 12. Testing set up on Instron ®. The braided 4 695.10 733.62 752.64 splice is connected to the load cell using a shear pin which is held to the machine by a small cap. The free end was held at the bottom of the machine by a capstan 5 713.80 672.43 645.70 which the rope was wrapped around at least two times. Mean 715.09 712.66 732.44

ASME 2011 Early Career Technical Journal - Vol. 10 103

However, the loss of strength did not come from Rope Set #1 Set #2 Set #3 failure within the splice. The specimens consistently failed at a Specimen Maximum Maximum Maximum point of tangency to the capstan and the load cell as can be seen Load (lbf) Load (lbf) Load (lbf) in Figure 14. The failure at this point was due to a sharp edge on the capstan which the rope was in contact with during 1 773.18 787.44 787.44 testing.

CONCLUSION 2 807.75 779.51 779.51 This paper explores the tensile strength and failure of braided splices. It proves that braided splices can be stronger 3 787.58 814.73 814.73 than previous assumptions that they cause the rope to lose ten percent of its original strength [1]. Many methods in braiding 4 784.06 776.62 776.62 were tested such as jamming the braid and different numbers of revolutions of the splice in the braid. The minimum number of 5 676.49 757.04 757.04 revolutions for a functional splice turned out to be three, and there could be no jamming in the splice or braid because it would cause breakage under stress. The percentage differences Mean 765.81 783.07 783.07 between each splice and rope sample never exceeded nine percent. However, the failures did not occur in the spliced Table 2 shows the maximum load achieved while region. testing each set of spliced rope and “plain” rope. Taking the mean of each set allows for the percent difference to be REFERENCES calculated. The equation below shows the formula for finding [1] Hartter, J., 2004, “Investigation of Synthetic Rope End percent difference: Connections and Terminations in Timber Harvesting ! − ! Applications,” Ph. D. thesis, Oregon State University, !"#$"%& !"##$%$&'$ = ! ! ×100 Corvallis, OR. . 5 !! + !! [2] “Guide to Rope Engineering, Design, and Use: Volume 1,” where E1 and E2 represent the maximum average loads of the Sterling Rope, Scarborough, ME. Accessed 12 October 2011. spliced rope and the “plain” rope. Set #1 of the splices and [3] Blanford, P.W. 2006. Rope Splicing. Brown Son and ropes yielded a 6.85 % difference in maximum load. Set #2 Ferguson Limited. yielded a 9.41% difference in maximum load, and set #3 [4] Fiber, Vectran. LCP Fiber Manufacturer| Synthetic Cable yielded a 6.68% difference in maximum load. Solutions.Web.15Sept.2011.http://www.vectranfiber.com/Hom e.aspx [5] Adanure, S. 1995. Wellington Sears Handbook of Industrial Textiles. Lancaster, Pennsylvania: Technomic Publishing Company, Inc. p 133-136. [6] Long, A. 2005. Design and Manufacture of Textile Composites. Abington Hall, Abington: Woodhead Publishing. [7] Ko, F., Pastore, C., and Head, A. 1989. Handbook of Industrial Braiding. Covington KY: Atkins and Pearce. [8] Branscomb, B. and Beale, D. 2011. “Fault Detection in Braiding Utilizing Low-Cost USB Machine Vision.”The Journal of the Textile Instsitute 102 (2011). [9] Branscomb, D., Beale, D., Brougthon, R., “Application of Machine Vision Techniques for Fault Diagnostics and System Examination of braid” Proceedings of the ASME 2010 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2010August 15-18, 2010, Montreal, Quebec, Canada

Figure 14. The splices consistently failed at this tangent point to the capstan and not within the splices themselves.

ASME 2011 Early Career Technical Journal - Vol. 10 104 ASME Early Career Technical Journal 2011 ASME Early Career Technical Conference, ASME ECTC November 4 – 5, Atlanta, Georgia USA

EFFECT OF WELDING PARAMETERS ON METALLURGICAL TRANSFORMATIONS OF ALUMINIUM ALLOY 7005

Reeta Wattal Sunil Pandey Department of Mechanical Engineering Sant Longowal Institute of Engineering and Technology Delhi Technological University Longowal, District Sangrur Delhi-110042, INDIA Punjab, INDIA

ABSTRACT alloying, cold working, heat treatment or a combination of The mechanical properties of welded structure are these. Wide variety of aluminium alloys have been developed, subjected to metallurgical transformations, which take place as amongst which Al-Zn-Mg alloys with Zn from 3.0 - 7.5% and a consequence of heating and cooling cycles connected with designated by 7xxx series, are known for high strength and are the welding process. The study of microstructure of alloys of choice in military, aerospace and transportation weldments and microstructure study is considered to be industries. The Al–Zn–Mg alloy has wide acceptance in complete when it is followed by microhardness survey. The fabrication of light weight structures requiring a high strength- study of microhardness in different zones is essential as the to-weight ratio, such as storage tanks of space rockets, correlation between microstructure and microhardness helps in transportable bridge girders and railway transport systems. confirming the analysis of results. This survey also gives an GMAW is considered to be an ideal process for joining indication about the soundness and mechanical properties of aluminium plates in thickness above 3 mm. the weldments, which might be expected from the welds The heat-treatable aluminium alloys provide good produced under different set of welding parameters. Extensive strength and toughness in engineering applications while microhardness of the weld zone was carried out to determine maintaining the low density and corrosion resistance of the possible phase presence responsible for variation in aluminum. These attributes allow the heat-treatable alloys to hardness. Microstructures were examined for all the be used in a wide variety of applications [6]. The strength of specimens and the entire surface was carefully scanned for heat-treatable aluminium alloy weldments is influenced by identifying typical microstructural changes. Optical rate of heat input to the workpiece during welding. Heat of photomicrographs were taken in three zones – weld metal, welding produces changes in the properties of the parent metal fusion/HAZ and base metal at various magnifications. Effect adjacent to the weld. These changes occur due to heat during of heat flow on different zones of weldment was studied. The welding and are a function of factors such as preheating, joint extent of porosity, the development of columnar dendritic configuration, type of backup and hold down, welding structure and the rosettes gave indications of heat flow and the process, heat input per pass, time interval between passes, gases entrapped during solidification of the weld metal. The welding sequence and dimensions of parts being welded. present work describes the effect of welding parameters such The heat input rate is one of the most important as the wire feed rate (W), arc voltage (V), contact tube to work variables in fusion welding. It governs heating rates, cooling distance (N), welding speed (S) and gas flow rate (G) on rates and weld pool size. The higher the heat input per unit metallurgical transformations of aluminium alloy 7005. length the lower the cooling rate and larger the weld pool size. Grain size in heat affected zone and in the weld metal are also Keywords: Metallurgical Transformations, Microhardness, influenced by heat input rate .High heat input and low cooling Microstructure, Weldment, Optical Photomicrographs, rate result in coarse grain structure and consequently impart Dendritic, Rosettes, Aluminium Alloy 7005 low hardness, less tensile strength, yield strength and ductile weldment. Thus microstructure of a weldment is the result of INTRODUCTION heating and cooling cycle, which in turn is directly related to Commercially available aluminium alloys can be the welding process and the material being welded. classified into three categories viz.; pure aluminium and non The microstructures developed in the weld metal heat-treatable alloys, medium strength heat-treatable alloys, and heat affected zone of fusion welding process can and high strength heat-treatable alloys [1]. In general, pure significantly affect the soundness and properties of resultant aluminium due to its low strength does not have applications weld [7-8].Properties of a welded structure have an important for fabricating many structures but is preferred for production bearing on metallurgical changes introduced by welding. The of special chemical plants, long-term storage containers in properties of a weld joint can be improved only by improving view of its excellent resistance to chemical attack, and its microstructure. Ease of oxidation and high thermal electrical bus bars [2-5]. Pure aluminium has a face centered conductivity of aluminium can result in oxide entrapment and cubic crystal structure. It is ductile and has very low strength lack of fusion. Excessive heat can result in a wide and softer in the annealed condition. The metal is strengthened by heat affected zone (HAZ) with low strength. In view of direct

ASME 2011 Early Career Technical Journal - Vol. 10 105

relationship between the weld defects and mechanical high solubility and it forms gas pores upon solidification due properties on one hand and microstructure on the other, it is to decrease in solubility. Consequently, the rejection of the gas essential to study microstructure and microhardness in various during solidification causes the supersaturaton of the liquid to zones of weldment in order to gain insight in to the effects of such an extent that bubbles of hydrogen are formed in the the process parameters on it. liquid. These bubbles create porosity in the weldments. Heat treatments that increase the strength and Excessive hydrogen porosity can severely reduce the strength, hardness of aluminium alloys utilize the mechanism of ductility as well as the fatigue resistance of aluminium welds. precipitation hardening. Precipitation hardening is the process From the literature survey [13-27], it is evident that detailed by which hardening of an alloy is caused by the precipitation study of microhardness along with microstructure under of a constituent from a supersaturated solid solution by heating various welding conditions is essential in order to achieve to some elevated temperature. The precipitation mechanism defect free weldment. requires alloying elements with appreciable solid solubility in The objective of this paper was to study the effect of aluminium at elevated temperatures, but with limited welding parameters on metallurgical transformations of solubility at lower temperatures [9].The strength of heat- aluminium alloy 7005. treatable aluminium alloys is obtained by solution treatment followed by quenching and then ageing, either at room METHODOLOGY temperature or, more usually, at elevated temperature. During Design of experiments the ageing treatment, the hardness and tensile strength increase Statistical designing of experiments based on because of precipitation and the formation of locally strained factorial techniques, reduce costs and provide the required regions associated with the formation of clusters of solute information about the main and interaction effects of welding atoms: Guinier-Preston zones. Heating at temperatures higher parameters on the response. Factorial design is a standard than the optimum value for age hardening results in overaging, statistical tool to investigate the effects of a number of the Guinier-Preston zones dissolve, precipitates increase in parameters on the response or output parameter. It involves size, and the matrix is softened [1]. simultaneously studying of more than one parameter or so- Since heat-treatable alloys are strengthened by called factor, each at two or more levels. The treatments precipitation hardening treatment, they respond to the heat of consist of all the combinations that can be formed from the welding. This response is more complex than those in non- different parameters [28-30].The two level full factorial design heat treatable alloys [10]. Metallurgical changes in these would require 25  32experimental runs for five parameters. alloys vary with distance from the weld interface. The welded However, for the sake of saving experimental and processing joint is a composite of all the parts involved in welding and time and resources, a quarter fractional factorial design of comprises the weld metal, the heat-affected zone and the 52 unaffected base metal. 2  8 weld runs was selected and all the five welding During pulsed-current GMA welding of the Al-Zn- parameters were investigated simultaneously by confounding Mg alloy, the variation in pulse parameters affects the the main effects with the interaction effects. The technique microstructure, chemical composition and porosity content of also quantified the two-parameter interaction effects. The the weld, which may influence its tensile and fatigue insight in to the interaction effects is not possible with the properties. During welding of these alloys, the zinc pickup in conventional experimental approach of varying one at a time the weld deposit, due to dilution of the base material, makes it keeping all other constants. precipitation hardenable, which plays a significant role in Selection of two levels governing the mechanical properties of the weld [11]. It has The judicious selection of direct parameters along also been reported that pulsed current multipass GMA welding with their extreme range having effects on the weld bead of thick Al-Zn-Mg alloy section improves the fatigue life of geometry was the next step in achieving the desired objective. the weld compared to the welds produced by continuous Determining extreme range of parameters and all possible current GMA welding [12].The speed of welding has a extreme combinations was based on maintaining equilibrium significant effect upon the mechanical properties of arc welds between welding wire feed rate and burn-off rate along with in heat-treatable alloys. High welding speed contributes to low good weld bead appearance and configurations. The limits of heat input and a narrow heat-affected zone. Increase in speed the welding parameters were selected on the basis of extensive also reduces the possibility of grain boundary precipitation, trial runs. The two levels selected provided weld beads with overaging, grain growth or a combination of these. acceptable profiles and were also free from the visual defects. The other factors which hamper the mechanical Parameters were coded as (+1) and (-1) or simply (+) and (-) properties of welds are the porosity formation in aluminium corresponding to the high and low levels for the ease of welds. The porosity occurs when hydrogen gas is entrapped recording and processing of the data using (1). Parameters with during solidification. The solubility of hydrogen is much their levels are given in Table 1. higher in liquid aluminium than in solid aluminium. Hydrogen is absorbed into the molten pool during welding because of its

ASME 2011 Early Career Technical Journal - Vol. 10 106

Microhardness Studies Hardness plays a significant role in determining the XX …..(1) jn j0 X j  characteristics of a metal and an alloy and quite often the J j results of such measurements can be a deciding factor to accept or reject the weldment. Since heat-affected zone is Xj = Coded value of the parameter diffusion-controlled and thermally dependent, the extent of the Xjn = Natural value of the parameter heat-affected zone is determined by measuring the Xj0 = Natural value of the basic level microhardness across this zone [6]. Hence, the study of Jj = Variation interval microhardness in different zones is essential as the correlation j = Number of the Parameter between microstructure and microhardness helps in confirming the analysis of results. This survey also gives an Table1.Welding parameters and limits indication about the soundness and mechanical properties of the weldments, which might be expected from the welds Parameter Units Limits produced under different set of welding parameters. Extensive Low (-1) High (+1) microhardness of the weld zone was carried out to determine Welding wire feed rate(W) m/min. 6.0 7.5 the possible phase presence responsible for variation in Arc voltage (V) Volts 26.0 32.0 hardness. Contact tube to work mm 15 20 Microstructure Studies distance (N) Microstructures were examined for all the specimens and the entire surface was carefully scanned for Welding speed (S) cm/min. 27 36 identifying typical microstructural changes. Optical Gas flow rate (G) l/min 20 25 photomicrographs were taken in three zones – weld metal, fusion/HAZ and base metal at various magnifications. Effect Development of a design matrix of heat flow on different zones of weldment was studied. The experiments are conducted for all possible Typical micrographs of grain growth, fusion boundaries in combinations of the parameter levels and these combinations welds were also included. These photographs are very useful when written in the form of a table, where the rows and helpful in studying the complex heat flow pattern in correspond to different trials and the column to the levels of different zones of weldment. The extent of porosity, the the parameters, form a design matrix. In order to determine the development of columnar dendritic structure and the rosettes effect of five parameters, a two level full factorial design gave indications of heat flow and the gases entrapped during solidification of the weld metal. would require thirty two trials 25  32. Such a large number of experiments would have been time consuming and costly, EXPERIMENTATION therefore a quarter fractional factorial design of eight weld The „Bead on plate‟ technique was employed for runs was selected. The design matrix developed is given in depositing the weld beads on mm plates using Table-2.The design matrix so evolved satisfied all the 25015010 properties like symmetry relative to the centre of experiment, a mechanized welding station. A three phase constant potential normalization, orthogonality and rotatibility [31]. full wave rectifier unit designed for gas metal arc welding process with a current capacity of 425 A at 60% duty cycle and an open circuit voltage of 12-48 volts was employed. AlMg5 Table 2. Design matrix. S. No. W V N S G welding filler wire of 1.6 mm ø with argon shielding was used. The test pieces prepared for bead geometry and shape 1 + + + + + relationships were polished using the usual metallurgical polishing techniques adopted for aluminium and its alloys. The 2 - + + - - specimens were emery polished on five emery papers followed 3 + - + - - by fine polishing using Alumina Grade 1 and 3. Well-polished test pieces were etched for microstructure and microhardness 4 - - + + + studies using Graff /Sargent reagent [20].The etchant was made fresh and used at room temperature. The polished specimens 5 + + - + - were immersed and agitated mildly for 50 seconds in Graff /Sargent reagent. It was followed by second etching in Keller‟s 6 - + - - + reagent for 10 seconds. Finally the specimens were rinsed in tap 7 + - - - + water and dried up by a hot air blower, which further developed the structure. 8 - - - + - Microhardness values of all the specimens were determined using Leica make fully automatic microhardness hardness tester with a 50g load in vertical and horizontal

ASME 2011 Early Career Technical Journal - Vol. 10 107

directions, i.e. one along the vertical axis of the weld bead and Vertical the second along the horizontal axis parallel and close to the WM HAZ 180 surface of the plate starting from the centre line of the weld. BM Microhardness was measured at an interval of 0.5 mm in the 160 weld zone, 0.1mm in the HAZ and at an interval of 0.5mm in 140 120 the base metal. Photomicrographs depicting the microstructure WM of all the welded specimens were taken for detailed analysis 100 80 with magnifications varying from 100X to 500X. load50g VHN, 60 HAZ RESULTS 40 BM Samples corresponding to the eight rows of the design 20 0 matrix were cut, polished, metallurgically polished and etched. 0 1 2 3 4 5 6 7 8 9 The etched samples were subjected to microhardness surveys. Distance from weld centre line, mm The complete history of samples related to the eight rows of the design matrix for vertical and horizontal directions are given in Figure 1. Microhardness survey for a specimen along the Table 3 and Table 4 respectively. The microhardness survey vertical direction with maximum penetration with a heat related to the conditions resulting in highest weld bead input of 1430 J/mm (Design matrix Row 3). penetration and maximum heat input both for vertical and horizontal direction are given in Figure 1 to Figure 4 respectively. The microhardness survey of the unwelded base Horizontal WM metal is given in Figure 5. 180 HAZ

BM Table 3. Details of microhardness survey for rows of the 160 140

design matrix in a vertical direction Row Avg. Max. Min. Std. Heat No. of 120 WM HV HV HV Deviation input Indentations 100

J/mm load 50g VHN, 80 1 129 160 105 3.96 1421 20 60 HAZ 2 117 163 88.9 7.19 1578 14 BM 40 3 129 157 98.3 3.47 1430 19 20 4 121 165 102 6.26 927 14 0 5 108 147 63.0 5.12 1421 18 0 1 2 3 4 5 6

6 125 156 88.5 6.52 1575 16 Distance from weld centre line, mm

7 123 156 107 3.19 1343 22 Figure 2. Microhardness survey for a specimen along the 8 106 153 86.3 6.17 907 16 horizontal direction with maximum penetration with a heat input of 1430 J/mm (Design matrix Row-3).

Table 4. Details of microhardness survey for rows of the

design matrix in a horizontal direction. Vertical WM Row Avg. Max. Min. Std. Heat No. of HAZ 180 HV HV HV Deviation input Indentations BM 160 J/mm 140

1 127 164 106 5.82 1421 13 120 2 110 157 84.1 4.25 1578 16 100 WM 3 132 160 85.8 4.8 1430 16 80 4 140 162 103 5.51 927 16 60 5 127 172 99.3 5.35 1421 16 VHN, 50g load 40 HAZ BM 6 130 157 86.2 5.38 1575 15 20 7 132 166 98.2 4.49 1343 20 0 0 1 2 3 4 5 6 7 8 9 8 121 143 88 7.47 907 11 Distance from weld centre line, mm Figure 3. Microhardness survey for a specimen along the vertical direction with maximum heat input 1578 J/mm (Design matrix Row-2).

ASME 2011 Early Career Technical Journal - Vol. 10 108

Horizontal WM Weld metal HAZ and dendritic 180 BM columnar structure 160

140 Fusion zone and 120 epitaxial gain 100 WM growth

80 VHN, load 50g 60

40 HAZ 20 BM HAZ and coarse grain 0 0 1 2 3 4 5 6 7 8 Distance from weld centre, mm Figure 4. Microhardness survey for a specimen along the horizontal direction with maximum heat input 1578 J/mm (Design matrix Row-2).

Base Metal BM Unaffected parent 180 metal

160

140 Figure 6. Microstructure showing various zones of a WM 120 weldment for a specimen with maximum penetration

100 along with heat input of 1430 J/mm (Design matrix Row-

VHN, 50g load 50g VHN, 3). 80

60

40 HAZ BM Equiaxed 20 structure Rosette

0 0 2 4 6 8 10 12

Distance, mm Microhardness indentation Figure 5. Microhardness survey for base metal. Weld metal and columnar dendritic The samples were microscopically examined and it structure was found that microstructure of all the three weld zones was columnar dendritic and almost similar. Therefore only few typical microstructures were included in the paper. These were related to conditions resulting in highest weld bead penetration, Figure 6, Lowest and highest heat input, Figures 7 and 8, and the Heat affected unwelded base metal (7005-T6), Figure 9. zone and coarse grains

Base metal

Figure7. Photo micrograph showing rosettes and Microhardness indentation for a specimen with minimum heat input 907 J/mm (Design matrixRow-8).

ASME 2011 Early Career Technical Journal - Vol. 10 109

temperature was very much higher than the solutionising Dendritic columnar temperature of this alloy might have caused dissolving of grains precipitates and subsequent slow cooling might have produced the condition for  phase to precipitate at preferred location such as grain boundaries, thus producing the annealed structure. This is indicated by fall in microhardness values in all the three zones as compared to the overall microhardness values of unwelded base metal. Since the microhardness trend for the remaining rows

HAZ of the design matrix was almost similar, thus it was felt not to include microhardness charts for the remaining rows of the design matrix. Microhardness Profile along the Vertical Axis The profiles in this direction were also characterized Fusion boundary zone by the trend similar to that in the vertical direction. The weld and epitaxial grain growth metal hardness is lower than the heat affected zone and base Base metal hardness. The average value of hardness in the horizontal metal direction was slightly more than the vertical direction. This could be due to the fact that the cooling rate along horizontal direction Figure 8 Photo micrograph showing microstructure of a is much more than along the vertical direction. Since aluminium specimen with maximum heat input 1578 J/mm (Design has high thermal conductivity, thus conduction loss in vertical matrix Row-2). direction is less as compared to horizontal direction where conduction, convection and radiation losses are more, which would have resulted in higher cooling rate. Microstructure study The photomicrograph in the Figure 6shows the microstructures of the sample belonging to the Row-3 of the design matrix at a magnification of 200X. The spherical particles are possibly of MgZn2, which is the principle soluble phase as reported in the literature elsewhere. The microstructure developed epitaxially from the heat affected zone to columnar dendritic with equiaxed grains towards the middle of the weld bead. The presence of columnar dendritic structure indicated lower G/R ratio. Where „G‟ is the temperature gradient in the direction of solidification and „R‟ is the rate of advance of solidification front. The presence of equiaxed grains towards the middle of the weld bead is the indication of high value (GR)-1/2 resulting in nucleation of dendrites at a point. Heat affected zone, is a recrystallized alloy on account of reaching temperature much higher than the temperature of recrystallization for aluminium alloy 7005. Thus the grains are coarser in size. On the contrary, in the base Figure9.Photo micrograph showing the microstructure of metal the elongated grains are in the rolling direction having the unwelded base metal aluminium alloy 7005-T6. finer grains.

The photomicrograph in Figures 7 and 8 are for the ANALYSIS OF RESULTS conditions of lowest and highest heat input. The microstructure Microhardness Profile along the Vertical Axis is very similar to one described above. However, there are some From the Figure 1 to 4, it is clear that the interesting observations. The width of the fusion zone is higher microhardness of the weld zone was lower than the parent for the higher heat input. Figure 7 shows the formation of a unwelded metal. The hardness of the base metal was found to be typical rosette probably in an interdendritic network of Al- greater than the heat affected zone and the weld metal. The Mg Al eutectic in an overall matrix of aluminium solid solution. decrease in hardness may be due to over aging of alloys in the 2 3 The rosettes are attributed to eutectic melting in the present case weld metal, where the alloys might have over aged and it could be due to reverse heat flow from the weld metal agglomerated into larger particles. This region, where decrease in deposited subsequently. hardness was noticed, might have reached temperatures above the solutionising temperature. During welding the arc

ASME 2011 Early Career Technical Journal - Vol. 10 110

CONCLUSIONS 10. Howard, E. Boyer., and Timothy, L. Gall., 1985,“ASM 1. The parametric window developed in the form of a Metals Handbook,” Desk Edition, ASM International, design matrix allowed 907 J/mm to 1578 J/mm of Metals Park, Ohio, pp. 28-78 to 28-83. heat input in the eight specimens belonging to the 11. Potluri, N. B., Ghosh, P. K., Gupta, P. C., and Reddy, Y. corresponding rows of the design matrix. S., 1996,“Studies on weld metal characteristics and their 2. All the weldments showed columnar dendritic influence on tensile and fatigue properties of pulsed structure developing epitaxially from the fusion zone. current GMA welded Al-Zn-Mg alloy,” Welding Journal, This is the indication of lower G/R ratio. 75(2), pp. 62s-70s. 3. All the weldments showed the presence of equiaxed 12. Hussain, H. M., Ghosh, P. K., Gupta, P. C., and Potluri, N. grains towards the upper middle of the composite B., 1996,“Properties of pulsed current multi pass GMA metal. This is an indication of high value of (GR)-1/2 welded Al-Zn-Mg alloy,” Welding Journal, pp. 209s-215s. resulting in nucleation of dendrites at a point. 13. Hatch, John E., 1984,“Aluminium Properties and Physical 4. All the weldments showed decreased micro- Metallurgy,”American Society for Metals, USA, pp. 134- hardness profiles indicating annealing (softening) 199. of the structure probably due to the coarsening of 14. Udin, Funk., and Wulf., 1954,“Welding for precipitates due to the slow cooling. Engineers,”John Wiley & Sons, pp. 280-285. 5. In some cases rosettes were observed in the 15. Mondolfo, L. F., 1970,“Structures of Al-Zn-Mg alloy,” composite metal indicating eutectic melting by Metallurgical Reviews, (153), pp. 95. secondary heat flow. 16. Kearns, W. H, 1982,“Metals and their weldability,” AWS 6. The parametric window developed almost ensured Welding Handbook, Eighth Edition, Vol.4, pp. 370-375. composite metal with practically nil or very low 17. Cross, C. E., Grong, O., Liu, S., and Capes, J. F., 1986, scattered porosity. Generally this otherwise is very “Metallography and welding process control,” Applied difficult to achieve. Metallography, pp. 197-210. 18. Sinha, Anil Kumar., 2003,“Physical Metallurgy Hand REFERENCES Book,” Mc Graw Hill, pp.3.105-3.114. 19. Yunjia, H., Frost, R. H., Olson, D. L., and Edwards, G. R., 1. Lancaster, J. F., 1993, “Metallurgy of Welding,” Chapman 1989,“Grain refinement of aluminium weld metal,” & Hall, London, Fifth Edition, pp. 311. Welding Journal, pp. 280s-289s. 2. Blewett, R.V., and Black, S., 1963, “Aluminium for 20. Mills, Kathleen. 1985, “Metallography and chemical and process plant,” British Welding Journal, Microstructures of Aluminium Alloys,” Metals 10(4), pp. 124-131. Handbook, Ninth Edition, Vol.9, pp. 351-388. ASM 3. Mizuno, H., and Nagaoka, H., 1981, “Application of International, Materials Park, Ohio. aluminium alloys to large welded structures in Japan,” 21. Huang, C., and Kou, S., 2001, “Partially melted zone in Colloquium on Aluminium and its alloys in Welding aluminium welds, Solute segregation and mechanical Construction, Porto (Portugal), IIW, Paper IV. behavior,” Welding Journal, 80(1), pp. 9s-17s. 4. Davis, J. R., 1987,“Corrosion of Aluminium and 22. Huang,C., and Kou, S., 2002,“Liquation mechanism in Aluminium Alloys,” Metals Handbook, ASM multi-component aluminium alloys during welding,” International, Metals Park, Ohio, Ninth Edition, Vol.13, Welding Journal, 81(10), pp. 211s-222s. pp. 583-609. 23. Huang, C., and Kou, S., 2003, “Liquation cracking in 5. Benjamin, D., 1979, “Properties and Selection-Non- partial penetration aluminium welds, Effect of Ferrous Alloys and Pure Metals,” Metals Handbook, ASM penetration, oscillation and back filling,” Welding International, Metals Park, Ohio, Ninth Edition, Vol.2, pp. Journal, 82(7), pp.184s-194s. 233-236. 24. Cao, G., and Kou, S., 2005,“Liquation cracking in full 6. Davis, J.R., 1994, “Aluminium and Aluminium penetration Al-Si welds,” Welding Journal, pp. 63s-71s. Alloys,”ASM Speciality Handbook, ASM 25. Howden, D. G., 1971, “Porosity formation in aluminium International, Materials Park, Ohio, pp. 376-419. weldments,” Welding Journal, pp. 113. 7. Esterling, K. E., 1983, “Introduction to the Physical 26. Gaofeng, Fu.,Fuquan, Tian., Hong, Wang., 2006,“Studies Metallurgy of Welding,” Butterworth and Company. on softening of heat-affected zone pulsed-current GMA 8. Kou, S., 2003, “Welding metallurgy,” John Wiley& Sons, welded Al–Zn–Mg alloy,” Journal of Materials Processing Inter science Publication, pp. 20, 239. Technology, 180, pp. 216-220. 9. David, Le Roy Olson., Thomas, A. Siewart., Stephen Liu., 27. Ceschini, L., Boromei, I.,Minak , G., Morri , A., Tarterini, and Glen, R. Edwards., 1993,“Welding, Brazing and F., 2007,“Effect of friction stir welding on microstructure, Soldering,” ASM Handbook, ASM International, tensile and fatigue properties of the AA7005/10 USA,Vol.6, pp. 528-536. vol.%Al2O3p composite,” Composites Science and Technology, 67, pp. 605-615.

ASME 2011 Early Career Technical Journal - Vol. 10 111

28. Montgomery, D. C., 1984, “Design and Analysis of Experiments,” Wiley, New York. 29. Wattal, Reeta., and Pandey Sunil., 2007,“Prediction of weld bead geometry in GMAW of aluminium alloy 7005,” Global Conference on Production and Industrial Engineering, National Institute of Technology, Jalandhar, March 22-24, Paper No.327. 30. Pandey, Sunil., 2004, “Welding current and melting Rates in semiautomatic arc welding processes: A New Approach,” Australian Welding Journal, 34-42. 31. Adler, Yu. P., Markova, E. V., and Granovsky, Yu. V. 1975. “The Design of Experiments to find Optimal Conditions,” Moscow, Mir Publishers.

ASME 2011 Early Career Technical Journal - Vol. 10 112 ASME Early Career Technical Journal 2011 ASME Early Career Technical Conference, ASME ECTC November 4 – 5, Atlanta, Georgia USA

DEVELOPMENT OF A MODULAR COMPANION ROBOT FOR THE ELDERLY

Jaime Mudrich, Andres Pacheco, Leonardo Ampie, Sabri Tosunoglu Florida International University Department of Mechanical and Materials Engineering Miami, Florida, U.S.A.

ABSTRACT This challenging conflict is illustrated by the following The goal of this project is to explore mechanisms that statistical data: The 2010 MetLife Market Survey of Nursing could be incorporated into the G.E.N.A.I. modular elderly Home, Assisted Living, Adult Day Services, and Home Care assistance robot that would enable it to support its elderly Costs reports an average annual cost for living in a nursing consumer [1]. With today’s trend for advances in health care, home to be approximately $40,000 per year [2]. The Employee people are living much longer than before. Increasing age is Benefit Research Institute reports an average annual income of typically accompanied by increasing health care costs. To persons aged 65 and over to be $28,778 [3]. This means that on alleviate some of this stress, an autonomous elderly assistance average, nursing homes are simply too expensive for the elderly robot has been prototyped. This work explores several or that an external financial contribution is required. The former mechanisms to enable the robot to shadow the consumer and case requires that assisted living be stricken as a solution to concludes that triangulation via color-based cameras would be dependency in old age. The latter case imposes stresses on the optimal solution for the G.E.N.A.I. application. The cameras either the government or loved ones. This is undesirable. were not obtainable over the short scope of the project and so a Another solution is hiring a registered nurse to make house triangulation system using ultrasound transceivers was visits. House visits include several types of services and employed instead. Testing is performed and while determination therapies. Some examples of these therapies include of distance to the target is accurate, the direction carries an occupational therapy, speech therapy, physical therapy, running error to the point of being unacceptable. The study reevaluates errands, and social services. This approach eliminates the need the method of calculation and switches from exact triangulation for the elderly to trade their home in for an assisted living to a different system that closely approximates direction. Upon facility. It also reduces the amount of time required from loved completion of testing, the “following” mechanism is ones for extra help. But at what expense? The National incorporated into the G.E.N.A.I. robot with very successful Clearinghouse for Long-Term Care Information reports that the results. The robot locates its target and maintains a desirable average cost for a “home health aide” in the U.S., as of 2009, is distance for effective service. Modularity is illustrated by $21 per hour [4]. Assuming one hour of assistance for five days integrating both a blood pressure diagnostic accessory and a every week over the course of one year, the elderly squanders medication organization accessory into the G.E.N.A.I. robot via approximately 19% of their annual income on health services. universal “discs”. Upon realization that complete autonomy This is a better solution, financially, than an assisted living lacks essential flexibility, a voice interface is implemented. facility and it is less demanding on the care givers of the elderly. Finally, an ultrasound array proximity system is explored. However, it is still very expensive and in many cases Modularity is emphasized and continued “geriatric engineering” unsatisfactory or unavailable. is promoted. This research’s proposed solution to the increasing health care need is automated assistance. This option is already in INTRODUCTION development for a hospital setting [5,6]. A follower, modular As medicine rapidly improves, so does the life expectancy companion robot was designed and prototyped with the pupose of our population. This means that we will have a larger and of alleviating the medical service demand. G.E.N.A.I. is an larger population of people who are steadily becoming less and acronym that stands for General Elderly Nursing and Assistant less capable of caring for them. There are a multitude of options Instrument. Many of the regular tasks required by the elderly or that address this problem. The dominant contemporary solutions disabled people can be performed completely by a mechanical are nursing homes for the elderly, and registered nurses that device [7]. Housing these mechanical devices in an automated make house calls. The greatest complication with both of these robot can eliminate the necessity for extra human assistance. solutions is the expense put forth to acquire these services. Robots can be designed and programmed to perform an infinite amount of tasks. This versatility allows for the robot solution to

ASME 2011 Early Career Technical Journal - Vol. 10 113 be applied to almost any unique disability-related challenge. For mass of the robot. By concentrating the mass of the robot close example, consider a person whose disability prevents them from to the ground, it immediately becomes more resistant to knocks. climbing a set of stairs. This person can opt to “rent” a To achieve this resistance, the heaviest component of the robot, registered nurse for the steep rates mentioned previously, or the battery, was placed at the very bottom of the platform, only instead a robot can aid in the task for no cost (after initial one inch from the bottom of its wheels. Additionally, a base was purchase) [8]. Robots are not cheap. Most elderly assistive purchased that was much heavier than required. Figure 1 technology comes with a respectable price tag. For example, illustrates the base. The direct current motors had plenty of consider power wheelchairs. The cost for these machines torque to spare and so some of it was traded for additional seldom dips below $1,000. However, the freedom gained by the reliability. A second preventative measure was to limit the investment more than justifies the expense. Furthermore, these possible vertical distance at which a knock could occur. Tipping mobility devices are quite often funded by the government as to is a result of unbalanced moments. Moment has a direct limit the out of pocket contribution from the user. We believe relationship to the product of applied force and perpendicular that robotic assistance can be equally, if not more, liberating for distance from the point of consideration. While the force from a the user than the power wheelchair. Costs will be comparable, if knock cannot be controlled, the maximum distance at which that not less. And over time as the elderly population increases, cost force can be applied is controllable. The G.E.N.A.I. companion of care will increase and perhaps the government will become robot was designed to be as short as possible while still being interested in funding these sorts of devices as well. In the event functional. In the worst case, the force will be applied at the that there is no government assistance, the cost of the robot over very top of the body. By reducing the robots height, the severity time is still less than a registered nurse or housing in an assisted of the resulting moment is lessened and so tipping is further living facility. resisted. Constrained by functionality and reliability, the robot exhibits a height of approximately two feet. MOBILITY Mobility is a critical component of the proposed G.E.N.A.I. elderly companion robot. To effectively assist the consumer, the robot must be able to efficiently navigate through different types of household configurations. Additionally, G.E.N.A.I. must be able to account for unpredictable obstructions, such as a person or a furniture rearrangement. Such constraints demand a versatile platform design. The platform must be fast enough to keep up with the consumer, taking into account the time required for readjustments. Agility is also critical to the platform, as the robot will be required to change direction frequently. Finally, the geometry of the platform must be considerate of snag prevention.

To guarantee that G.E.N.A.I. will be able to stay near the Figure 1. Platform base consumer, the platform was designed with the capacity to move at a maximum speed of twice the average walking rate. Two A second mode of mechanical failure is becoming common options for robotic propulsion are servomotors and “snagged” by household obstructions and thus immobilized. If direct current motors. Direct current motors are simple, careful consideration isn’t taken, collision between the powerful mechanisms, but require additional components for geometry of the robotic platform and geometries of other them to be useful to a microcontroller. Servomotors are more objects may result in the two locking themselves to one another. microcontroller friendly, but are significantly more expensive There are essentially two ways to prevent such interference. The for the same power. After careful economic analysis, the direct first is to perform in-home consultations to minimize the current motors proved friendlier to the robot’s affordability. The potential of household configurations from resisting the selected motors were capable of traveling four feet in one functionality of the robot. This is costly and impractical for the second with no load. Such speed was well over the necessary desired “out-of-the-box” use of the G.E.N.A.I. robot. The load and so an engineering assumption was made that it would second option is to attempt to prevent collision and to optimize be able to keep up with the consumer, while carrying a the geometry of the body and base so that they are resistant to significant payload. the various possible obstructions typically found in the As an elderly companion, the G.E.N.A.I. robot is very household. This option is much more cost-efficient and in tune likely to collect a great deal of responsibility and so must be with the goals for the companion robot. Collision prevention is reliable. There are several mechanical modes of failure that achieved via ultrasonic proximity sensors. This technology and were considered in the design of the robotic platform. The first its implementation will be expanded upon later. Several of these is the potential of the robot to be knocked on its side. different geometries for the platform base were considered. Preventative measures were taken by carefully distributing the

ASME 2011 Early Career Technical Journal - Vol. 10 114 Amongst these were rectangular, triangular, and circular. The considered as a future expansion. On the contrary, the worst circular base was the best choice, owed to its absence of any situation is the robot colliding with various objects and losing edges. The body of the robot was designed to be cylindrical for line-of-sight with the consumer. This situation obviously would the same reason. Without edges, the likelihood of G.E.N.A.I. to not inspire the consumer with confidence, nor would it allow be caught on sharp corners is drastically reduced. Another the platform to stay within the desired proximity of the preventative measure is wheel positioning. External wheels will consumer. The research conducted provided a solution between easily catch on wall corners or table legs. To remedy this threat, these two extremes. the drive wheels were placed on the perimeter of the base, but To accomplish efficient object avoidance behavior, an array inset via custom grooves in the base. Passive wheels were of five ultrasound proximity sensors was employed. One of the chosen that were short enough to fit underneath the platform sensors was placed on the front center of the robot, six inches and not be exposed to any stimuli outside of the platform above the platform base. The others were placed at the same perimeter. The completed base is depicted in Figure 1. height, on the same side, thirty degrees from one another, distributed symmetrically about the central sensor. Having a OBJECT AVOIDANCE collection of sensors provided a better picture for the robot as to One of the greatest challenges pertaining to the G.E.N.A.I. what its surroundings looked like. Planes were created via companion robot is smooth passage across the household. The interpolation between data from adjacent sensors. These planes challenge is found in the numerous unknowns related to the allowed the microcontroller to estimate where it would be able configuration of an individual’s home. It is impossible to know to pass the object. By executing this estimation from a short the geometry of the consumer’s household. As such, the robotic distance away, the platform was able to plan a more efficient platform must be equipped with enough sensors and logic to trajectory to help keep up with the consumer. Figure 2, below, adapt to the more general cases. Typical collision avoidance illustrates the configuration of the sensors as well as a basic systems are comprised of “time-of-flight” ultrasonic or expression of the data collection from a general object. electromagnetic proximity sensors, as well as a comparative logic that helps to paint for the robot a picture of its environment. This is also the case for the G.E.N.A.I. elderly companion robot. The best technology to use for household object detection turned out to be ultrasound. The most cost-efficient, commercially available choices were ultrasound or infrared. Infrared offers better accuracy than ultrasound, but has a very narrow beam. To effectively detect impending collisions, the wide ultrasound beam is preferable. Ultrasound easily acknowledges thin objects that infrared would miss, such as table legs.

Typical ultrasound proximity sensors use a “time-of-flight” Figure 2. Object avoidance schematic logic to figure the distance between the sensor and the next object in front of it. The sensor will first emit an ultrasonic Without an object avoidance system, G.E.N.A.I. would pulse. The sensor then waits for the pulse to ricochet off of the merely locate the consumer signal and chart a direct path to that next object in front of it and return. The sensor counts the time signal. With the ultrasound array system, G.E.N.A.I. used the that passes between emission and reception. This time is halved consumer signal coupled with the environmental data it (to account for the return trip) and then multiplied by the speed gathered, to plot a more efficient path, keeping it a step ahead of sound at standard temperature and pressure to finally of its less capable predecessor. Again, the best solution would calculate the distance between the sensor and the next object in be a mapping system that would be less dependent on the front of it. robot’s sensory. Additionally, infrared packages exist in which a Due to the potential liabilities created by the services that single sensor will sweep across one hundred eighty degrees, the G.E.N.A.I. companion robot provides, it must be especially collecting high-resolution environmental data. This of course is savvy in all of its functions. Efficient obstacle detection and far more expensive, but ought to be considered after the avoidance is critical because of its contribution to the robot’s prototype stage. mobility. The ideal situation for object avoidance would be for the robot to store a map of the household in its memory. Such a NAVIGATION SYSTEM map would prevent the robot from having to constantly take Household navigation is the single most challenging aspect inventory of its surroundings and instead allow it to spend more of the companion robot design. The difficulty lies in the many time following the consumer. This situation would require unknown variables pertaining to target recognition. A few costly memory expansion and the involvement of an examples of these variables include line-of-sight obstructions, experienced programmer. At this stage, such an option is only

ASME 2011 Early Career Technical Journal - Vol. 10 115 electromagnetic interference, and multiple targets. Numerous right ultrasound data are denoted as “d1” and “d2”, respectively, systems have been examined and compared. For the purpose of and finally, “L”, represents the distance between the two prototyping, the researchers opted to employ triangulation via triangulation ultrasound sensors. ultrasonic transceivers. What follows is an explanation of the These values are passed to the mobility mechanism, finally concept being used and its application. allowing the robot to move towards the elderly target. The logic ULTRASOUND TRIANGULATION map, shown in Figure 4, is a symbolic representation of the To localize the target, two ultrasound sensors were microcontroller behavior. mounted on the front of the robot at a known distance from one another [9]. The consumer carries an ultrasound emitter on their person. When the signal strikes the robot, each sensor determines the angle at which the signal is coming from with respect to the frame connecting them. With these two angles, and the distance between the sensors known, the microcontroller can determine the coordinates of the signal relative to a frame fixed to the robot. Figure 3, below, illustrates the concept behind this technology.

Figure 3. Graphical representation of triangulation Figure 4. Logic map for platform mobility

CONTROLLER SOFTWARE DEVELOPMENT MODULARITY The controller programming is what gives the robot life and The primary goal for the G.E.N.A.I. robot was to develop a allows it to make decisions. For the design project at hand, the robotic platform capable of satisfying a substantial variety of study required a program that could effectively collect elderly needs. One possibility for accomplishing this was to environmental data from the ultrasound sensors and process that stock the robot very densely with a large quantity of data. Once the data was processed, the robot had awareness of mechanisms directed towards the most general complications in its environment and the location of the person whom it was to the every day life of the elderly. Upon deliberation, it was follow. Finally, the microcontroller, with this information, was concluded that such a method might lead to extra, unused able to command the mobility components to shorten the gap components on the robot. Each individual has unique challenges between the robot and the target elderly consumer. and so the “general” design may not be sufficient. To the The microcontroller first attempts to determine where the contrary, it may contain more features than required and so the consumer is relative to the robotic platform. To accomplish this, design would not be cost-efficient for the consumer. For these the aforementioned ultrasound triangulation is employed. Each reasons, the “general” design was exchanged for a of two triangulation ultrasound transceivers takes a turn customizable, modular design. calculating the distance to the consumer. After this information A modular design for this application is desirable because is obtained, the following equations are used to determine the of the great diversity in day-to-day complications for the relative position of the elderly consumer with respect to the elderly. For the consumer, a modular design means an initial G.E.N.A.I. platform. purchase of a standard robotic platform. The platform contains the components that offer the robot the most potential for Equation 1 achieving a multitude of tasks. Examples of these components are the mechanisms that enable mobility, the object-avoidance components, and a navigational system. Mobility is required to Equation 2 remedy the decreasing mobility of the aged consumers. The companion robot can offer very little, statically. Object where (xR, yR) is the relative location of the consumer in a avoidance is required as a supplement to mobility. A household coordinate system fixed to the G.E.N.A.I. platform. The left and navigational system is critical and could also be said to

ASME 2011 Early Career Technical Journal - Vol. 10 116 supplement the mobility of the robot. With mobility the opening to the tray. Figure 5, below, depicts the conceptual components, the robot may be able to move, but it will not be model and prototyped medication control module. able to figure out where to go, e.g., towards the consumer, or a recharge station. These standard components give G.E.N.A.I. the capacity to perform a majority of the services provided by a home nurse. Purchasing the standard G.E.N.A.I. platform is like purchasing a drill. It affords you great torques and rotation speeds, but is essentially worth nothing without drill bits to transmit that power. The drill bits in this case are the accessories that will connect G.E.N.A.I. to the consumer through the unique services they provide. Some of the potential tasks considered that would motivate an accessory are medication control, alerts and reminders, at-home doctor Figure 5. Conceptual design for medication dispensing appointments via video chat, diagnostics, and so on. To date, the actualized accessories are medication control, voice VOICE INTERFACE interface, and early stages of diagnostics. A completely autonomous design for the G.E.N.A.I. robot was desirable, but its consideration yielded too many MEDICATION CONTROL complicated circumstances. It was quickly realized that One of the more feasible accessories to construct, and also effective autonomy would require employing a team of one of the best to exemplify the potential of the G.E.N.A.I. programmers. Instead, a human interface was introduced as robot, was medication control. It is very common that aged another accessory for the G.E.N.A.I. platform. Such an citizens will rely on a multitude of medication to combat accessory allowed more flexibility to the governing algorithms deficiencies resulting from old age. Most of these medications of the platform and so would be able to serve the consumer are required to be taken on different days and different times. more effectively. Unlike the medication organizer, this As such, medication scheduling can become rather complicated. accessory could not be fabricated so easily. The solution was A remedy to this complication can be found in commonplace provided in the form of the Parallax Say It module [10]. The organizers with pill compartments, ranging from morning to Say It module identifies verbal commands and through night and from Sunday to Saturday. Some are available with programming can be related to the actions of the G.E.N.A.I. scheduled alarms to assist the consumer in remembering to take robot. The module comes with PC software that allows the the appropriate medication. One drawback for these systems is programmer to create different words within the module limited range. The medication might be completely organized, memory for it to recognize. The user then calibrates that word and alarms set at the appropriate time, but an alarm may not be to the spoken command. The code affiliated with the new audible across the home (or even in the next room for that commands are then generated and exported to the same format matter). In this very real circumstance, the G.E.N.A.I. used by the governing microcontroller. companion robot provides a remedy. At its roots, G.E.N.A.I. is a One of the motivators for the voice interface was the household navigation follower robot. Ideally, it will always be situation where the user requires temporary privacy, such as in in close proximity to the consumer where he or she will easily the restroom. Under the normal logic of the robot, it was notice any kind of notification provided by the medication supposed to continuously follow the consumer, unless the organizer. consumer was within a certain range of the robot. That included For prototyping, a simple, seven-compartment tray was following right into the restroom as well. It would not be fabricated and mounted on a one hundred eighty degree uncommon for the consumer to prefer that the robot wait servomotor. The servo and tray were then mounted on a twelve- outside during this time. To accommodate this preference, the inch disc that fit into the top of the robot body and rested on voice interface was employed. A command called “wait” was several supports installed around its inner diameter. (The created and linked to a subroutine. The subroutine waits ten twelve-inch disc represents the universal mounting system for seconds, allowing the consumer to shut the bathroom door, and all of the accessories.) The prototype medication organizer was then activates a motion detector that contains the doorway in its also equipped with a buzzer and LED that were wired through sensory cone. The robot was required to patiently wait where it the ceiling of the robot where they were easily heard and seen, was when the command was given until the motion detector respectively. At the appropriate time and date, the tray would sensor was fired, indicating the door opening once more. turn to reveal the scheduled medication. The LED would flash Another example of the usefulness of the voice interface and the buzzer would sound, reminding the consumer that it was was the situation where the robot blocks the consumer’s line of time for their medication. After a time interval, the tray would sight. This situation can easily occur as the consumer is walking conceal the previously exposed compartment and instead block past his or her television set to have a seat. If the path to the seat is between the seat and television, it is quite possible that the

ASME 2011 Early Career Technical Journal - Vol. 10 117 robot will end up resting right in front of the television. To the considering that it is an invasive measurement, it was shied robot’s understanding, it is doing exactly what it is supposed to away from (for now) as a potential liability. In future work it do. To the user, this is clearly not what the robot should be will be desirable to include a data acquisition system that can doing. Fortunately, with the Say It module, the user can simply collect the blood pressure measurements and then wirelessly call out “Move!” and follow it with a direction to get the robot communicate that data to the consumer’s physician. out of the way. Another case where the “Move!” command This accessory very clearly and powerfully illustrates the might prove useful is if the robot is blocking a tight passageway. immense benefits of the G.E.N.A.I. robot. What should also be Without the voice command module, the G.E.N.A.I. robot taken from this example is the fact that the diagnostic system is can still operate and make use of the other accessories that the merely an accessory. It is not included in the standard, universal consumer may choose to integrate. However, it is clear that robotic platform. What this means is that if you happen to be a having such control would be a desirable improvement over diabetic, then this accessory is perfect for you and you should complete autonomy. Point being, that the modularity of the purchase one. If you are not diabetic, then there is no reason to robot allows the consumer to purchase those accessories that fit have this feature and so the consumer is spared the expense. their budget and needs, at their discretion. Modularity is key to the success of such technology.

BLOOD PRESSURE DIAGNOSTICS DISCUSSION The final accessory exhibited over the course of the The researchers believe that they have successfully research was a blood pressure diagnostic device. The device prototyped a modular elderly assistance robot. G.E.N.A.I. is was store-bought and merely positioned within the robot. The capable of following an ultrasonic signal through an controls for the device were mounted on the standard twelve- environment laced with random obstructions, simulating a real inch disk and made accessible for the consumer. The cuff and household situation. The test environment was not nearly as tube used to collect the blood pressure was hidden within the complex as a consumer’s home could be, but still served as a body of the robot, accessible through a door in the back. Figure successful proof of concept. The mechanism for following the 6, below, illustrates the blood pressure module. consumer (ultrasound) is with many pitfalls, but again serves well as a proof of concept. The researchers are confident that additional temporal and financial investment will easily remedy such pitfalls. Figure 7 illustrates the completed prototype.

Figure 6. Blood pressure diagnostic module

Very often people are required to perform their own diagnostics at home and then report that data to their doctors. For example, in the case of diabetes, sufferers of diabetes very frequently are required to measure their own glucose levels and Figure 7. Robot body concept (left) and prototype (right) blood pressure levels. Collecting these measurements requires a Modularity is illustrated via interchangeable accessories in pair of machines, typically stored in one place. When time the form of an automatic pill manager as well as a blood comes to take these measurements, the diabetic must stop what pressure diagnostic device. The intent of this research was to they’re doing, go to this location, take the measurements, and introduce a novel concept of modular elderly assistance and then return once again. inspire future development. The researchers feel that they were To facilitate the meticulous measurements, the blood successful in achieving this goal, in that the benefits of the pressure accessory was integrated into the G.E.N.A.I. robot. modular design are obvious. Consumers are given the ability to Instead of having to return back to the location of machine customize the G.E.N.A.I. platform as required to maximize the storage, the consumer can simply turn to the G.E.N.A.I. robot economy of their investment. that is standing right next to them. The back door is opened, the Future work will integrate the accessories into the body of cuff is pulled out, and then the machine is turned on. It was very the robot better than the initial prototype. Additional accessories desirable to also implement a glucose-measuring device, but

ASME 2011 Early Career Technical Journal - Vol. 10 118 will also be designed and integrated to further illustrate the versatility and necessity of a modular companion robot. Furthermore, alternative localization systems should be investigated to replace the ultrasound system; environmental sensors with wireless communication may prove fruitful. A robust household layout mapping system would be beneficial to the mobility of the platform and should be invested in.

ACKNOWLEDGMENTS The authors would like to cordially thank the Ronald E. McNair Post Baccalaureate Achievement Program for supporting the development of the G.E.N.A.I. modular companion robot for the elderly.

REFERENCES [1] Ampie, L., Mudrich, J., Pacheco, A., & Tosunoglu, S. (2011) G.E.N.A.I. Companion Robot. Florida Conference on Recent Advances in Robotics. Gainesville, Florida [2] MetLife Mature Market Institute. (2010). Market Survey of Long-Term Care Costs. Connecticut. [3] Employee Benefit Research Institute “EBRI”. (2008). Income of the Elderly Population Age 65 and Over. Retrieved August 13, 2011, from www.ebri.org/pdf/notespdf/ EBRI_Notes_06-June10.Inc-Eld_COBRA.pdf [4] National Clearinghouse for Long-Term Care Information “NCLTCI”. (2009). Costs of Care. Retrieved July 15, 2011, from http://www.longtermcare.gov/LTC/Main_Site/Paying/ Costs/Index.aspx. [5] Pollack, M., Engberg, S., Thrun, S., et al. (2002). Pearl: A Mobile Robotic Assistant for the Elderly. AAAI Workshop on Automation as Eldercare. [6] Baltus, G., et al. (2000). Towards Personal Service Robots for the Elderly. Carnegie Mellon University. Retrieved September 12, 2011, from http://www.cs.cmu.edu/~nursebot [7] Guth, J. (2002). High Tech Medicine and Robotics. Retrieved September 13, 2011, from http://jhguth1942.tripod.com/scitechnews/id9.html [8] Chen, C., Liao, T., & Pham, H. (2010) On Climbing Winding Stairs for a Robotic Wheelchair. World Academy of Science, Engineering and Technology. 299-304 [9] Jimenez, A.R. and Seco, F. (2005) Ultrasonic Localization Methods for Accurate Positioning. Madrid: Consejo Superior de Ivestigaciones Cientificas. [10] Parallax “Say It” Module. Parallax 2011 catalog #30080

ASME 2011 Early Career Technical Journal - Vol. 10 119 ASME Early Career Technical Journal 2011 ASME Early Career Technical Conference, ASME ECTC November 4 – 5, Atlanta, Georgia USA

THE DESIGN AND VALIDATION OF WAVERIDERS DERIVED FROM AXISYMMETRIC FLOWFIELDS

Nastassja Dasque and Frederick Ferguson North Carolina A&T State University Greensboro, North Carolina, USA [email protected]

ABSTRACT favored. Later, Bowcutt [2] showed not only that waverider In the present paper, waverider configurations are configurations supported the Kuchemann findings, but that generated by specifying an arbitrary conical shockwave, and a viscous optimized waverider configurations can potentially out- corresponding leading edge. The inverse design approach makes perform the blended body aircraft configurations and thus break use of a numerical tool that is based on a semi-analytical the Kuchemann‟s „L/D barrier‟. Bowcutt‟s findings were later approach for solving the Euler equations. Engineering details supported by others [3 and 4], as demonstrated in the associated with the inverse design procedure are summarized illustration depicted in Figure 2. herein. In the waverider design space, the aerodynamic figure of merits such as the lift-to-drag ratio, L/D, and the volumetric efficiency, Veff, are considered functions of both the conical shockwaves angles; theta, , and beta, ß, and the leading edge curves that are carved on the shockwaves. The design method yields practical vehicle shapes with acceptable volumetric efficiencies and high L/Ds. Further, the design method is computationally efficient and permits rapid parametric studies. Several viscous optimized waverider configurations were derived and their aerothermodynamic performance analyzed with AFRL-WPAB CFD research code AVUS. This paper focuses on the validation of the aerodynamic performance of the configurations that were derived from the inverse waverider design procedure.

INTRODUCTION The waverider is a conceptual vehicle designed to operate Figure 1. Flight Mach Number and Aircraft Shape in the hypersonic flight regime, generally greater than speeds of Mach 5. A basic feature of all in-flight hypersonic vehicles is the creation of relatively strong shockwaves emanating from their leading edges. Associated with the flowfields behind these shockwaves are severe aerothermodynamics, propulsion system integration and aeroelastic design problems. This feature is characteristic of both ballistic and lifting vehicles, so in either case the relationship between shockwave shape and vehicle shape is of fundamental importance to effective vehicle design. After a thorough review of flight vehicle performance over a range of Mach numbers, Kuchemann established an „L/D barrier‟ and the associated aircraft configurations that perform best within this barrier [1]. Kuchemann demonstrated in Figure 1 that at high Mach numbers in order to maximize aircraft performance, blended body configurations with tightly integrated forebodies, propulsion and nozzle afterbodies are Figure 2. The Kuchemann “L/D” barrier [3]

ASME 2011 Early Career Technical Journal - Vol. 10 120 DESIGN METHODOLOGY r1, j  f (x1, j ), x1, j1  x1, j x (1) A waverider is constructed from streamlines of a hypersonic The independent variable, x, is defined in the interval (a, b), flowfield so that its generated shock is bounded by the lower where x = (b - a)/N. Each point numbered j; for j = 1, N + 1 surface. The design process described in this paper is based on and i = 1, represents the beginning of a streamline on the work done [5, 6 and 7], which is built on the following two shockwave. In addition, a line described by i, for i = const, will axioms: First, two imaginary streamlines are assumed to be called a data line. The flow variables and their respective emanate from each point on the shock surface. One represents a partial derivatives at each point on a given data line must be freestream streamline that is processed by the shock and found. This information is used in a Taylor series expansion to another, which remains undisturbed, as shown in Figure 3. Any predict the flow parameters on a new data line some distance dx curve described on the generating shockwave will be called a and dr downstream in the flowfield. However, the increments, leading edge. Each leading edge in turn generates two stream dx and x, represent two different intervals, the first being an surfaces, namely, an upper freestream surface and a lower increment in the development of the flowfield and the second, an compression surface. Secondly, the inviscid surfaces are increment along the shockwave. In this study, dx is chosen to be replaced by a solid wall without any interference to the outer half of x. flowfield. Using these axioms, the generation of a particular Figure 4 is an illustration of the numerical process. The configuration becomes a matter of choosing appropriate leading first data line, along which the flowfield information is known, is edges on an assumed shockwave. immediately after the shockwave, and can be represented by the

shockwave itself for the sake of simplification. The objective of the numerical process thereafter is to develop a new data line some distance dx and dr downstream. In general, the increment, dx, may be chosen as a constant value throughout the flowfield.

Figure 3. Illustration of Waverider Construction

FLOWFIELD GENERATION An integral part of the waverider design is the flowfield information behind a shockwave of interest, as the waverider is a product of its environment. The methodology developed [5-7] is used to generate conical hypersonic flowfields from which waveriders are carved. This design method is applicable to two- dimensional, axisymmetric and generalized three-dimensional flowfields. In an effort to describe this tool without undue complexity, a complete analysis is given here of the flowfield Figure 4. Illustration of Marching Process generated by an arbitrary axisymmetric shockwave. All numerical processes will be described in a cylindrical However, the increment, dr, must be calculated at each grid coordinate frame of reference, namely, x, r and , where the x point. The new flowfield parameters: u, v, p and  are evaluated axis is aligned with the free stream velocity vector. The flow as per the Taylor series expansion formulation as follows using φ variables are the properties of the flowfield, namely u, v, p and to represent any flowfield property: where u and v the cylindrical velocity components in the x and r directions respectively,  is the density and p the pressure.   i1, j  i, j  dx  dri, j (2) Given Mach number, flight altitude with known freestream x r properties, and a shockwave shape in the form of equation 1, the flowfield parameters behind the shock can be calculated [4]. The partial derivatives come as result of the solution to the Euler equations coupled with directional derivatives [5]. The

ASME 2011 Early Career Technical Journal - Vol. 10 121 solution, illustrated by equation 3, yields N streamlines, s, with known flow parameters at discrete points along the streamline.

  s (x , r ,u , v , P ,  ) 1 j  N 1 i  N  j 1 (3) i, j j i i i i i i

WAVERIDER SHAPE GENERATION Once the flowfield is constructed and the streamlines are determined, a three-dimensional waverider configuration can be created. In the case of an axisymmetric flowfield, the third dimension is introduced by the waverider shape angle, j. Therefore, the shape of the waverider is defined in cylindrical coordinates, x, r, and , where the x-axis is along the Figure 7. Completed Waverider Forebody waverider‟s length. The shape angle,  is defined by choosing a base plane curve, as shown in Figure 5, with j = 1, N +1. Once DERIVED WAVERIDER EXAMPLES a base curve is chosen, a set of shape angles is found and the Two developed waveriders, a flat top waverider and a flat waverider shape is carved from the conical flowfield, as shown bottom waverider, are offered as examples. For illustrative in Figures 6 and 7. purposes, the base parameters used to construct the flat top In fact, a large class of 3-Dimensional shapes can be created waverider, shown in Figure 8, and the flat bottom waverider, with the appropriate sets of waverider shape angles. Twenty- shown in Figure 9, are described as follows: three different waverider shapes have been created using the present method. Each one used the same x and r coordinates.  ru   rl  However, each had its own unique set of shape angles.  N 1,1   N 1,1   j  arccos (4)  j  arccos (5)  ru   rl   N 1, j   N 1, j 

Figure 8. Flat Top Waverider Developed using Eq 4

. Figure 5. Base Plane

Figure 9. Flat Bottom Waverider Developed using Eq. 5

In a similar manner, configurations composing of desired features of the „flat top and flat bottom‟ waveriders can also be Figure 6. Conical Flowfield and Base Curve derived, illustrated in Fig 10.

ASME 2011 Early Career Technical Journal - Vol. 10 122 given by Bowcutt [2]. This relationship is expressed as a function of the edge Mach number, Me, in the following manner:

4 2.641 logRes  6.421exp1.209 10 Me  (14)

where Res is the transition Reynolds Number. In this research, the transition region was not considered; rather a transition point separates the laminar and turbulent flow regimes.

Figure 10. Hypersonic Vehicle Derived Waverider CODE VALIDATION

In order for the results of any code to be meaningful, they must be validated. To validate this code, the results are LOCAL SKIN FRICTION COEFFICIENT AND SHEAR compared to two independent waverider generation codes STRESS CALCULATIONS developed by others [3 and 5]. Validation studies were The skin friction coefficient distribution along the conducted at a Mach number of 6, a waverider length of 1 m, streamlines that form the waverider configuration is evaluated and an axisymmetric shockwave angle of 16° for a Flat Top using the Reference Temperature Method [3, 4]. For laminar waverider at sea level. The results are compared favorably flow, the local skin friction and Reynolds number are defined as: having an average of 3% error for waverider performance and

1 2 geometric characteristics. 0.664  T  vs   Re  The flow variables and viscous properties computed are c f    (6) s (7) Res  T   highly dependent on the streamline geometry, and computed independently of the waverider shape. However, they represent where v∞, µ∞ and ρ∞ are freestream quantities, and s is the local the aerodynamic properties found along the upper and lower distance measured from the leading edge. The reference streamlines of potential waveriders. For example, Figure 11 temperature T’ and the coefficient of viscosity are also shows the shear stress distribution in the lower and upper calculated as follows: surfaces with a Mach number of 10, waverider length of 10 m, and a shockwave angle of 16°. The behavior of the shear stress  is as expected, with the shear stress in the lower surface being T 2  T    T  1.0  0.32M  0.58 w 1 (8)    (9) much higher than that in the upper. Also, this shows that most T  T        T  of the waverider is in the turbulent region, which is also expected. where M∞ is the freestream Mach number and Tw is the wall temperature. The exponent ω used in Equation 6 is the exponent in the approximate viscosity variation relationship defined in Equation 9. A value of = 0.75 was used in this work as performed by Corda [3]. For turbulent flow, the local skin friction and the turbulent Reynolds number are evaluated as:

0.0592 v s c   f 0.2 (10) Res  (11) Res   where the quantities ρ‟ and µ‟ are evaluated at the reference temperature defined in Equation 5. The local shear stress and the dynamic pressure at the edge are defined as: Figure 11. Shear Stress Distribution on Flat Top Lower Surface 1 2   c f  qe (12) qe   Ve (13) 2 The analysis of the code developed indicated that each waverider achieved acceptable L/D characteristic that was close The effects of boundary layer transition on the skin friction to the Kuchemann „L/D barrier‟ at Mach numbers below 10. coefficient and the shear stress are incorporated in equations (6 - However, the waveriders out-performed the Kuchemann „L/D 13). Boundary layer transition is predicted using the correlation barrier‟ for Mach numbers of 10 and higher. Figure 12 shows how the Flat Bottom, Lower Circular Arc, and Bat Wing

ASME 2011 Early Career Technical Journal - Vol. 10 123 waveriders compares to the Kuchemann Barrier. The Kuchemann Barrier, illustrated in Figure 12, is compared to the performance of the waveriders generated in this analysis. Results show that the waveriders performed best at the high Mach Numbers.

Figure 14. Waverider Computational Grid

CFD results of the waverider generation study are illustrated in Figures 15 – 17. The results represents the Euler solution produced by the AFRL-WPAB research code AVUS for a Mach 6 waverider. The Mach 6 configuration was chosen for Figure 12. Lift Over Drag Comparison simulation studies because of limitations of solution stability at larger Mach numbers. Figure 15 shows that the Mach is fairly uniform within the shock layer. Figure 16 shows the pressure CFD RESULTS distribution at the base plane. The pressure within the shock CFD analysis was also employed on a developed waverider. layer shows a semi-axisymmetric flowfield, this is due to the For such evaluation, the waverider design code was modified to small blunting of the waverider configuration. Figure 17 shows generate hypersonic vehicle configurations with the appropriate that the shock is bounded by the lower surface. The weak shock computational grids. Once a waverider geometry is generated, seen at the upper surface is also due to the blunting effect. an option is available to allow for the following scenarios: (a) Nonetheless, the results confirm that the waverider external data generation in STL format for further CAD processing, refer flowfield are confirming the predictions of the waverider code. to Fig. 13, and (b) a structured grid generated in Plot3D format, as highlighted in Fig. 14. The grid incorporates the use of grid clustering techniques at the surface of the waverider as needed for viscous CFD studies.

Figure 13. Waverider in STL Format

Figure 15. Waverider Exit Plane Mach Number

ASME 2011 Early Career Technical Journal - Vol. 10 124 REFERENCES [1] Kuchemann, D., 1978, The Aerodynamic Design of Aircraft. Oxford, Pergamon. [2] Bowcutt, Kevin G., Anderson, John D., Jr., and Capriotti, Diego., 1987, “Viscous Optimized Hypersonic Waveriders, ” AIAA Paper 87-0272. [3] Corda, Stephen and Anderson, John D., Jr., 1988, “Viscous Optimized Waveriders Designed from Axisymmetric Flowfields,” AIAA Paper 88-0369. [4] Anderson, John D. Jr., 2000, Introduction to Flight, 4th ed. Boston: McGraw-Hill, pp. 622-626 and 681-707. [5] Ferguson, Frederick, 1993, Ph. D Dissertation, Department of Aerospace Engineering, University of Maryland, College Park, Maryland, UM-AERO-93-5. [6] Ferguson, Frederick, et al., 1995, “A Design Method for the Construction of Hypersonic Vehicle Configurations,” AIAA 95- 6009, Chattanooga, TN, April 3-7. Figure 16. Waverider Exit Plane Pressure Field [7] Ferguson, Frederick, and John D. Anderson, Jr., 1993, “Expanding the Waverider Design Space Using General Supersonic and Hypersonic Generating Flows”, AIAA 93-0505, Reno, NV, January 11-14.

Figure 17. Waverider External Pressure Field

CONCLUSIONS The design methodology herein can be used in the conceptual design phase of any hypersonic vehicle. The presented work shows its capabilities of constructing and analyzing waverider configurations. All waveriders were carved from the same flowfield, using the same freestream conditions. However, they differ in shapes because they were constructed from different waverider shape angles. The derived waverider examples reinforce the fact that a wide class of waverider shapes can be constructed by using this method. Also, each waverider achieved L/D that stayed close to the Kuchemann Barrier, sometimes even crossing it. CFD studies have also reaffirmed the capability of the methodology to produce waveriders by reproducing a similar flowfield from which the waverider is derived.

ASME 2011 Early Career Technical Journal - Vol. 10 125 ASME Early Career Technical Journal 2011 ASME Early Career Technical Conference, ASME ECTC November 4 – 5, Atlanta, Georgia USA

EXPERIMENTAL TESTING AND POTENTIAL IMPROVEMENTS OF A PERISTALTIC CRAWLER FOR PIPELINE UNPLUGGING

Jose Matos Sabri Tosunoglu Florida International University Florida International University Department of Mechanical Engineering Department of Mechanical Engineering Miami, FL, United States Miami, FL, United States

ABSTRACT however all have met with limited success. The main reason is that these unplugging methods lose effectiveness as the This paper details the assembly of the first prototype of and distance to the plug in the pipeline increases. A crawler can proposed modifications for an innovative unplugging avert this issue by going up to the plug and applying abrasive technology for high level waste (HLW) pipelines on the DOE techniques directly on the plug. The first two prototype Hanford site. This technology, a crawler which moves by crawlers have proven that a nozzle fed by a conventional peristaltic motions, was developed by the Applied Research pressure washer is quite effective at this task. The first Center (ARC) at Florida International University. The prototype was able to destroy a 1.5’ sludge type plug. The environment within Hanford pipelines provides major design second crawler used a stronger pressure washer machine and challenges not only in the form of radioactivity but also sizing nozzle to destroy a “saltcake” plug- the result of a sludge type constraints. Hanford site provided pipeline sizing information plug drying out over time and becoming solid. The main that consists of Victaulic© brand 3” inner diameter pipes and challenge comes in developing a crawler that can make it to the 90° elbows with a 4.25” turning radius. For the benefit of the plug and survive the levels of radiation in the pipeline. reader, background information on the theoretical development is provided and the general design process has been outlined. MOTIVATION The main focus of this development is centered on the construction of the first prototype. The first prototype served as There are many technologies available for unplugging of pipes. proof of concept for the design and method of locomotion of In many industries, it is possible to unplug pipes by simply the crawler. Upon completion of this project, ARC proceeded putting solvents or other chemical agents into the affected pipe. with a second prototype. This second prototype was made of This is not a desirable solution for the Hanford pipelines as radiation hardened materials but did not prove flexible enough these chemicals would simply become extra waste once to maneuver through elbows found in the test bed. A new contaminated in the pipeline. The chemistries of Hanford waste crawler is being proposed with the goal of creating a device that are varied due to the different processes for plutonium will be agile and flexible, yet strong and radiation-hardened enrichment that were used on the site in the past. This makes such that it can survive within Hanford pipelines. the wastes difficult to characterize and it would not be ideal to add solvents to the pipes and add even further chemistries. INTRODUCTION Water is already present in the Hanford waste and the site has an evaporator facility for removing water. This opens the door The DOE Hanford site has approximately 53 million gallons of for technologies that use water for performing unplugging. high level radioactive waste spread about 177 underground Mechanical means of unplugging pipes are also acceptable. The tanks. 149 of these tanks are older single-shell units, some of main issue is that these technologies lose effectiveness over which have been known to leak. For this reason, the waste from large distances. these tanks is transferred to 28 double shell tanks via transfer lines with the ultimate goal of sending the waste to a treatment The Applied Research Center at FIU has tested such plant where the waste will be vitrified. Once within the technologies in the past. Some of these technologies include the treatment plant, the waste must still move throughout a system Harben Jet by Harben Inc., the Aqua Miser by Carolina of pipes. This presents a challenge because the waste is in Equipment & Supply, a wave erosion device by NuVision slurry form and the solids often settle out and clog the Engineering Inc., and a bladed device by Ridgid Tool Company pipelines. Many unplugging technologies have been developed, [2]. These technologies all had specific advantages but none

ASME 2011 Early Career Technical Journal - Vol. 10 126 proved satisfactory when tested in a large scale pipeline built clear elbows. The configuration of the blades does not allow by the Applied Research Center. them to clean out an entire plug within the 3 inch pipes tested and they break when used against harder plugs. Another issue is The Harben Jet and the Aqua Miser are similar technologies that its range is limited by its 150 ft metal rod [2]. which consist of a trailer with a water tank and a hose mounted to them. Self-propelled nozzles with forward and rearward The failure of these technologies clearly establishes the need facing jets are mounted on the ends of both hoses. The Harben for a device that can bring the unplugging tool directly to the Jet has a provision to vibrate the hose so that it shakes its way plug and hold it in place. A pneumatic crawler can do this by around elbows in the pipe and it pumps out water at 4,000 psi. crawling directly up to a plug and affixing itself to the walls of This technology did not prove effective against harder, saltcake the pipe. Large distances do not present a problem for a crawler type plugs and it uses a large amount of water [2]. As its name provided the body of the crawler can withstand large pressures suggests, the Aqua Miser uses a lower volume of water than the which it uses to generate pulling force. A properly designed Harben Jet and it pumps water out at a pressure of 40,000 psi. crawler will be capable of managing many elbows and will be However, there is no vibration system for the hose so this hose capable of reaching plugs in a shorter amount of time than a becomes stuck after two elbows or after moving forth 200 ft. It self-propelled nozzle. Unlike wave erosion techniques, a nozzle would also prove to be ineffective against saltcake plugs fed by a pressure washer can destroy a three foot long plug because there is nothing to fix the nozzle in place in front of the within minutes. A nozzle by itself however, cannot be plug. This means the nozzle will simply move backward under controlled and there is no provision to stop it from moving back the force of its own jet [2]. The Harben Jet and Aqua Miser are under the force of its own blast. A crawler solves these shown in Figure 1. problems by holding the nozzle firmly in place and allowing for changes in angle through cycling of the crawler.

SYSTEM DESCRIPTION AND DESIGN

System Description There are a few main considerations in designing a crawler to meet the Hanford pipeline requirements. The crawler moves forward by inflating and deflating the three air cavities on its body. The front and rear cavities are used to anchor the crawler to the walls of the pipe. The central cavity is used to move the crawler forward. A schematic of these cavities is presented in Figure 2.

Figure 2. General Air Cavity Layout [1]

The general sequence of motion used by this crawler design consists of four steps. In the first step, pressure is sent to the

Figure 1. Harben Jet (top) and Aqua Miser [3] rear balloon which will expand to grab the pipe wall. Pressure is then sent to the bellows in center which expands and moves The wave erosion device by NuVision Engineering Inc. creates the front rim forward. The front balloon is then pressurized a vacuum in the pipe before the plug and then fills the pipe with such that it grabs the pipe wall as well. A vacuum is then drawn water. Some air is left trapped between the plug and the water. from the rear rim such that the rear balloon deflates. Once the The system uses pulsations to create waves in this air gap to rear balloon is deflated, the bellows is deflated in the same erode the plugs. This method is quite slow and is ineffective manner. This moves the rear rim forward and completes one over longer pipelines as it becomes more difficult to create the cycle of motion. From here, the cycle is repeated, creating a needed vacuum [2]. forward motion comparable to that of a worm. These air cavities are fed by a tether consisting of multiple air lines. The Ridgid’s unplugging technology consists of a metal rod with pressurization sequence may be observed in Figure 3. blades on the ends. The metal rod is flexible which allows it to

ASME 2011 Early Career Technical Journal - Vol. 10 127

Figure 5. Fitment Validation of Optimized Rim [4]

The distance the crawler can travel will partially be determined by how much tether it can pull. This particular detail is determined by how much force the crawler exerts when it moves forward. This force is in turn dependent on the pressure the bellows is inflated to. This force can be determined theoretically using equation 1: Figure 3. Finite Element Model of Pressurization Sequence [1] !"#$% = !"#$$%"# ∗ !"#$ (1) Kinematics The area between the inner and outer bellows is determined by Analyses were carried out in order to verify that the crawler subtracting the cross sectional area of the inner bellows from could meet the limitations imposed by the pipeline. Computer that of the outer. The inflation pressure of the bellows is then Aided Design/ Finite Element software was used to perform multiplied by the resulting cross sectional area. Hanford pipes these analyses before the actual prototypes were built. One area are not to exceed 300 psi. However, this does not mean that a of importance is ensuring that the crawler physically fits within crawler within them would be limited to this pressure. Using 2 the pipeline. The outer diameter of the bodies was selected in 300 psi for pressure and 0.869 in for area as benchmarks, the order to do so and the resulting rim designs were run through a above equation yields a theoretical pulling force of 260.7 lbs. model of the Hanford elbows to test if they fit. The initial The feed hoses used for the first prototype weighed 15 lbs per design for the rims was able to pass through; however, it was every 100 ft of line when together. This means that this crawler observed that the angles at which it passed would lead to the could theoretically crawl 1738 feet. In a real situation the bellows becoming stuck. Figure 4 illustrates the problem. distance would be shorter due to friction imposed by the elbows and pipe surface on the tether.

Another point of interest is the speed of the crawler. Although Hanford schedules would allow for a crawler to take weeks to reach a plug and destroy it, ideally this would not be necessary. In theory, speed is determined by how much distance a crawler travels when expanded and by the time it takes to contract or expand the bellows. The time needed to expand or contract the bellows is determined by the flow rates of air within its feed lines. If a crawler does not provide the desired speed, it can be improved by using a compressor and vacuum pumps that can provide a higher cfm and by increasing the inner diameter of the lines used to feed the crawler. The other area where speed Figure 4. Fitment Validation of Original Rim [4] can be gained is in the collapse ratio of the bellows. Simply put,

the distance the crawler travels in one cycle is equivalent to the

difference between is length when collapsed and its length This finding led to an optimal new design for the rims which is when expanded. For example, a bellows with a collapse ratio of smaller in both length and diameter. The new design was tested 9:1 will travel forward 8 inches during each cycle. Any in the same manner as the original to verify that the problem improvement in either of these parameters can be used to had been resolved. Figure 5 presents the result of size increase the speed of a crawler [4]. optimization on the crawler rims.

It should be noted that the length of the bellows plays another important role. The length of the bellows is an important consideration when traveling through elbows. The longer the

ASME 2011 Early Career Technical Journal - Vol. 10 128 bellows, the less rigid it will be, allowing it to pass an elbow without trouble. A short analysis of the elbows the crawler will have to maneuver makes it possible to determine the minimum length required of the bellows.

The Hanford elbows have a 4.25” turning radius. Using the equation for arc length, ! = !", where S is the arc length, r is the radius and θ is the angle being considered in radians, these 90° elbows have an arc length of approximately 6.68”. The bellows cannot be shorter than this or else both rims of the crawler, which are rigid, would end up in the elbow at the same time. This would cause the crawler to wedge into the elbow and become a plug itself. However, this failure may be avoided simply by selecting a bellows, which is longer than the arc length of the elbows.

In the case of both prototypes developed, the length of the bellows selected was 12”; almost double the length of the elbow, which allows for the front rim of the crawler to exit the elbow well before the rear rim can enter it.

Stress Considerations and FEA Analysis

The crawler must be able to grip the walls of the pipe with a certain force in order to avoid slipping under the weight it pulls and in smooth sections in the pipe. The anchoring is a result of the linear relationship between normal force imposed by the balloon on the inside of the pipe and the friction force that results as related by equation 2: Figure 6. Anchor Force Modeling: Anchor Force vs. Pressure (top); Necessary Wall Thickness in Inches [1] !ƒ ≤ µ!! (2) These balloons were also modeled at the 300 psi inflation where Fƒ is the force due to friction, µ is the coefficient of said pressure within the restraint of a three inch inner diameter pipe. friction, and Fn is the normal force acting between the surfaces. It was found that the balloons would see a maximum von Mises This force will also aid in allowing the crawler to go further as stress of 1008 psi. The rubber balloons used in prototype I have excess slippage would result in the device not being capable of an ultimate strength of 2175 psi and the polyurethane ones in continuing forward. prototype II have an ultimate strength of 5511 psi. In either case, the ultimate strength of the materials is well above the An FEA model of the system was built using Abaqus software level of stress imposed by the operating conditions [1]. [1] in order to determine how thick the balloons would have to be in order to withstand the pressure necessary to provide the desired traction. At a balloon pressure of 300 psi, it was found that the balloons could anchor a 600 lb load and would need a wall thickness of 0.38 inches in order to survive. Figure 6 displays these results.

Figure 7. Stress on Balloons [1]

ASME 2011 Early Career Technical Journal - Vol. 10 129 It is important to note that some variations in friction factor are A further point on the crawler where stress is a concern is the to be expected within Hanford pipelines. The friction factors support for the unplugging tool. The tether of the crawler is between the crawler and the various surfaces in the pipelines affixed at this point. A finite element analysis was performed in are difficult to calculate. At the lowest end of the friction order to optimize the tool support to where it could sustain the spectrum, the crawler may have to move through sections of necessary loads. This was performed in CosmoWorks and pipe that have slight sludge buildup on the walls. At the other Ansys for comparison purposes. In either case, the study was end of the spectrum, the highest friction the crawler may performed with several mesh sizes; the mesh size being experience will be in sections of pipe where the waste has dried decreased successively until the results converged The initial along the walls and formed rough saltcake surfaces. The waste support design was loaded with a 50 lb force and restrained at in every Hanford tank is unique, work is currently being done the area of the rims that holds the balloons. It was found that to characterize the various wastes and determine their specific the support would have a factor of safety of 0.61 under this chemical compositions. However, the general properties of load. plugs that have formed in the past have been studied well enough that the development of the above mentioned simulants This result was unsatisfactory; leading to further optimization was possible. This creates an avenue for modeling the surfaces of the design so that it would support a higher load and have a experienced as common substances which are comparable. higher factor of safety. The design was modified and retested until the final factor of safety reached a value of 5.2 under a When fully dried out, sludge can have a surface roughness load of 350 lbs. The final design obtained through this process comparable to that of concrete. Unlike mud, the friction factors was imported into Ansys in order to check this result. Ansys of concrete against various materials are well characterized. provided a minimum factor of safety value of 6.8. The results The crawler’s balloons are made of rubber and the generally for maximum stresses and displacements were also similar accepted friction factor between rubber and concrete varies between the two programs; this is displayed in Table 1. from 0.6 to 0.85. These values reduce to a range of 0.45 to 0.75 between rubber and concrete which is wet [6]. These surfaces will provide the best possible traction for the crawler and pose Table 1. Comparison of Results from CosmoWorks and Ansys no impediment to its motion. Traction will be most difficult to obtain in pipes that have sludge on the walls.

Sludge buildup on pipe walls may consist of varying types of sludge, comprised of various chemical compositions. Friction factors may vary considerably, but on average can be modeled as wet clay. However, knowing this still does not answer what the friction factors may be as wet clay varies considerably and there are not commonly accepted values for friction between this material and other surfaces. This is where testing becomes important. It should be noted that the pipeline used as a test bed for both crawler prototypes consists of clear plastic pipe. This pipe has a much smoother surface than the steel pipes used in Hanford. Particularly when wet or coated in sludge, these pipes will have a friction factor which is much lower than what is possible within Hanford’s aging steel pipes. In tests it was found that even when the crawler’s balloons were coated in sludge, the crawler would not lose traction. This is because the balloons were designed to expand to a diameter of 6”- double that of the pipe ID. When the balloons inflate, they rid themselves of some sludge. The pressure they generate against the pipe wall helps to displace sludge, creating a firm hold on the pipe. As stated above, the force of friction is equal to the coefficient of friction of the surfaces in question multiplied by the normal force, so the higher the normal force the crawler Figure 8. Refining of Mesh Size in CosmoWorks generates, the greater the grip it has on the pipe wall. This is another reason that using a material that can handle the stress of the highest allowable inflation pressure is necessary; because the pressure will determine the normal force of the balloon against the pipe wall and allow for traction to be obtained even when the friction factors are rather low.

ASME 2011 Early Career Technical Journal - Vol. 10 130 that the crawler is designed for are made of steel and have a 3 inch inner diameter. There are various components in these pipes, like 45 and 90° elbows having long and short radii. The most difficult to maneuver are the short radius 90° elbows which have a 4.25 inch turning radius [1]. As such, a proper test bed for the crawler need only have these 90° elbows in order to verify that the crawler can maneuver through the Hanford pipelines. Using clear pipes for the test bed allows for the motion of the crawler to be studied and also provides further validation because these clear plastic pipes are much smoother than steel pipes. This makes it harder for a crawler to obtain traction in the pipe and a crawler that can move through these without slippage can do the same within Hanford pipelines.

Figure 9. Stress Analysis in Ansys (top) and CosmoWorks [4]

BENCHMARKS Figure 10. Abaqus Model of Elbow Maneuver [1] In order for a pipe crawler to successfully accomplish the task of unplugging Hanford pipelines it must manage to survive The final benchmark for a successful crawler is that it must be three challenges. These challenges consist of being capable of capable of destroying the types of plugs that it may come up surviving the levels of radioactivity in the pipeline, being able against. In order to test this, it is necessary to create these plugs to physically move through the pipeline and its various elbows, and test the crawler’s unplugging tools against it.DOE has and finally being capable of destroying any kind of plug that it commissioned many studies regarding characterization of the comes up against. various tank wastes and the types of plugs that they can form. The first challenge can be met by careful material selection and As a result, Pacific Northwest National Laboratory has been design. There are many materials, mostly metals, which will able to formulate various simulants which can be used to create survive in radioactive environments. A material commonly test plugs that have the physical properties of the actual plugs. used for components that come into contact with waste is grade The dissolution rates, solubility, and mechanical strength of 316 Stainless Steel. It can be left in contact with waste and will these simulants have been studied extensively [7] and it is not not break down from the radioactivity nor corrode due to the necessary to perform these studies in order to test a crawler. chemicals in the waste. This material is ideal for the rims on This presents a further advantage as technologies can be either end of the crawler. However, it is not ideal for the validated using these simulants without need to perform the bellows in between the rims as it does not provide enough testing within a hot cell. This also bypasses the need to go flexibility. Nonmetals like polyurethane and Kevlar are a better through the various levels of approval necessary for testing a fit as they are flexible and have been found to survive in device on actual radioactive plugs. radioactive environments [6]. There are three categories of plugs to be found within Hanford The pneumatic design of the crawler is another feature that will pipelines and a category of simulants to model each [7]. Sludge allow it to survive the radioactivity. An electronic robot with plugs are considered the most common plug in Hanford motors and circuits would not have been able to do so as pipelines. These plugs are simulated using Bentonite Clay. As conventional circuits undergo failure when placed in a these plugs dry, they form partially solidified plugs that are radioactive field. There are radiation hardened electronic known as hardpan plugs. Over time, the plugs will continue to components; however these are much larger than conventional dry and when completely dried out and solidified, they are electronics. A crawler made with such components would not known as saltcake plugs. This last category is the hardest type have met the size constraints imposed by the pipelines. of plug and it is the most difficult to destroy. These plugs are It is not necessary to stress that being able to maneuver through simulated by Sodium Aluminum Silicate [7]. Generally, when Hanford pipelines is a very important benchmark. The pipes one of these plugs has formed the only option is to cut out the

ASME 2011 Early Career Technical Journal - Vol. 10 131 section of pipe that it is lodged in and replace it with new pipe. would remain in the same location in the pipe. This situation No unplugging technology has been capable of removing one cannot be avoided altogether. Even with a hollow crawler, a of these plugs in the past [2]. pressure washer will flow water into the chamber in front of the crawler faster than the hollow center will evacuate it. The PROTOTYPE I pressure washer used for these tests can flow up to 2.5 gpm at a pressure of 2600 psi. The central tunnel of the crawler is a In order to validate the theory of the peristaltic crawler, an passive evacuation passage which could never approach this. initial prototype was built. This first crawler consisted of rubber The flow rate through the central passage can be modified by inner and outer bellows and aluminum rims on either end. The changing the diameter of this central channel; however the inner and outer bellows create an air cavity between themselves dimensional constraints of the crawler limit this inner diameter which is filled or vacuumed in order to expand or contract the to a maximum of 1 inch. Even at this maximum diameter, body of the crawler. Simultaneously, this allows for the center testing has shown that the flow rate of the pressure washer of the crawler to be hollow such that waste flows through this exceeds the flow rate of the crawler’s center. channel during unplugging. The aluminum rims each had a rubber sleeve (balloon) over them which were held down by Knowing this, one may be led to question why the hollow CV joint clamps on both ends. Air cavities drilled into the rims center has been included altogether. However, this hollow allowed air to flow from an input fitting to the sleeves in order center serves three very important purposes. The first purpose to fill them. An image of the first prototype crawler can be seen the hollow center serves is that of reducing the pressure in Figure 11. generated in the chamber between the crawler and the plug. If the pressure in this chamber gets too high, it may dislodge the plug from the pipe walls and cause it to move further down the pipe. This is not desirable because the plug could simply become a problem in another portion of the pipeline. The amount of pressure required to dislodge a plug in this manner varies greatly depending upon the hardness of the plug and how well it has adhered to the pipe wall. This pressure is difficult to quantify and there is no way to know beforehand what that pressure level is for every single plug that may be encountered. For this reason, the hollow center is used to reduce how much pressure can be generated and full evacuations are still Figure 11. Prototype I [1] performed. The pressure washer was chosen with the idea of completely dissolving a plug such that it becomes waste water In order to perform unplugging, a bracket was installed on the and can be flushed down the pipeline and this procedure makes front rim of the crawler in order to hold a pressure washer it possible. The second purpose the hollow center serves is that nozzle. The hose from the nozzle to the washer machine ran it reduces the amount of times which the full evacuation through the hollow center of the crawler and did not interfere procedure must be performed. This cuts down on the amount of with the crawler’s motion. The air lines were attached to the time which is spent on an unplugging operation. Over a series washer line in the rear so that they would also be pulled when of five trials, the average time recorded for unplugging 1.5” the front of the crawler moved forward. foot Bentonite plugs was 30 minutes. Four full evacuations were needed over the course of each unplugging operation. It is At this point it is necessary to explain the decision to make the possible that this number could have doubled with a non hollow center of the crawler have a hollow passage. Removing waste crawler, increasing the unplugging to time to an hour. The final flow through the device is not a requirement for successful reason that the central passage of the crawler is hollow has to operation. It is rather an advantageous feature incorporated into do with simplifying the overall design. The line for the pressure the crawler. When the crawler begins an unplugging operation, washer travels through this passage to the front of the crawler it is anchored at both ends by its balloons for maximum where it is needed. If the crawler did not have this hollow adhesion to the pipe. The idea is to keep the crawler from passage, it would be necessary to find a way to seal the ends of moving back under the force generated by the pressure washer. the crawler where the pressure washer line passes. Though not In order to remove waste water from the chamber formed in impossible, this would increase the complexity of the device between a crawler which is not hollow and the plug, an somewhat as well as creating a possible failure by providing a emptying procedure must be followed. This procedure consists place for air to leak out if one of these seals were to fail. of stopping the water flow and deflating the front balloon, allowing waste water to flow around the crawler to the rear These considerations aided the first prototype in achieving most balloon, re-inflating the front balloon and then deflating the of the required benchmarks. This crawler proved to be quite rear. This would allow for water to move rearward of the successful, being capable of maneuvering its way through the crawler in a peristaltic motion. Simultaneously, the crawler 90° elbows and climbing through a smooth, slippery pipe

ASME 2011 Early Career Technical Journal - Vol. 10 132 quickly, even when the pipe was vertical or completely submerged. However, it was not without its faults. This prototype had durability issues, the clamps would chew into the sleeves over time causing them to lose air pressure and leaks would form around the bellows. Precise assembly was required in order to ensure that the crawler would survive prolonged use. The maximum inflation pressure of the bellows was 30 psi; any amount over this would cause the bellows to leak [4]. Figure 12. Prototype II

Despite these drawbacks, this prototype was built specifically These achievements did not come without some drawbacks. for proof of concept and in order to discover any possible Although the new bellows was stronger, it was also much faults. Prototype I was put through speed, pull- force, elbow stiffer. This meant that more time was required in order to maneuverability, and complete test bed testing. The findings compress and expand the bellows, making the second prototype from this prototype allowed for the design of a newer, more much slower than its predecessor. The stiff new bellows also fault- tolerant design. created problems in maneuvering through elbows. This issue was so severe that Prototype II was unable to crawl through PROTOTYPE II regulation Hanford elbows and different ones had to be used on the test bed in order to complete testing. The new polyurethane Using the lessons learned from the original crawler prototype, a sleeves also presented an issue because of their thickness. They second generation prototype was built at ARC with the did not expand as much as the rubber sleeves and did not intention of improving durability [3]. It was also decided to use provide as firm a hold on the pipe walls. This led to the crawler materials that could survive within a radioactive environment. slipping on occasion. This is not desirable as it can slow down A set of grade 316 stainless steel, hydro-formed bellows with the forward motion of the crawler and cause it to move flanged ends were obtained for this purpose. The inner and backwards during unplugging operations. This crawler showed outer bellow flanges were machined such that they would fit that further optimization was needed and a new design would together onto flat end caps. These caps were then welded on, have to be made- one which would combine the benefits of making the inner and outer bellows into one unit. The caps both earlier prototypes whilst not sharing their weaknesses. were also drilled to accommodate air lines. Two holes were drilled and tapped in each such that bolts could be used to hold FUTURE DESIGN down the rims as opposed to the old method of clamping them on. Shorter rims were built and a set of hemispherical metal In order to create a crawler that can meet all of the required pieces were added to each rim after assembly in order to aid the criteria, it is necessary to test bellows made from various crawler in passing through elbows. The front hemisphere had a materials. However, the possible materials are quite limited in bracket for holding the washer nozzle. New polyurethane that not all materials can survive in the presence of sleeves were added to each rim and held down by stronger radioactivity. There are metals such as grade 316 Stainless clamps than the ones used previously. Steel which can survive, however they do not provide the necessary flexibility. It may be possible to overcome this by These changes resulted in a much more durable crawler which designing the bellows in such a way that multiple sections of did not develop air leaks over prolonged use. Figure 12 displays metal can collapse onto one another while maintaining a seal; the second generation prototype. Assembly of the crawler was however the most straight forward approach is to use non- simplified considerably as the bellows were simply bolted on to metals. Many studies have been performed in order to identify the rims with gaskets in between to seal the air. A brand new such materials. Hanford Standards document TFC-ENG-STD- vacuum pump with a stronger vacuum force and a tank for 34 details selection of non-metals in contact with tank waste. vacuum was added and helped to compress the stiffer metal Table 2 on the following page is taken directly from this bellows. This new bellows could be inflated to 100 psi, document. allowing the new crawler to have a much greater pulling force. This is important because the pulling force generated by the crawler determines the length of tether it can pull through a pipeline, i.e. how far it can travel. Prototype II was able to crawl through vertical and submerged pipes just as well as Prototype I. Also, with its new pressure washer machine and nozzle, the second prototype was able to destroy a 3’ saltcake plug, a feat which no previous unplugging technology had achieved [3].

ASME 2011 Early Career Technical Journal - Vol. 10 133 crawler is a time consuming process. These balloons need to Table 2. Acceptable Non-metals [6] have a smaller wall thickness than the second prototype but Listed Acceptable Materials larger than that of the first. The idea is to have a balloon that Ethylene propylene (EP), ethylene-propylene will inflate more than that of the second prototype’s whilst rubber (EPR), ethylene-propylene-diene monomer being more puncture resistant than the first’s. It may be (EPDM)1 desirable to make these from Kevlar as well. A conceptual Teflon1 , Teflon with 50% 316 SS (PTFE, TFE) image of the new design is shown in Figure 13. Viton1 A (fluoro copolymer) Kynar1, Kynar with EPR O-ring (PVDF) Tefzel1 (ETFE) Buna-N (Nitrile) Ultra-high molecular weight polyethylene (UHMWPE) 1 Graphite (Grafoil ) Polyether Ether Ketone (PEEK) Figure 13. Final Conceptual Design Kelvar1 (aramid) Noryl1 – copolymer PPO and PS A good deal of testing will be necessary to validate the new Blue-gard 1 3000 and 3700 gaskets materials and design. Much like the first two prototypes, the new design will be subjected to crawling through a test bed, Of these materials, Kevlar is of highest interest. Kevlar can be performing unplugging operations, performing pull force tests, woven into various forms and made air tight. A custom shaped and crawling through pipes full of water. Unlike the first two Kevlar bellows could be a potential solution for the newest prototypes, it will also be tested on a large scale test bed crawler design. Kevlar strands that have been impregnated with consisting of the same type of steel pipes that are found on the epoxy resin have a tensile strength of 3600 MPa or 525,000 psi Hanford site. The Applied Research Center at FIU has plans to [8] which would make it ideal for this application. It is often build a pipeline in excess of a thousand feet in length in the used in applications that require penetration resistance such as field of the Engineering Campus. The new crawler will have to bullet and knife proof vests. The proper weave of Kevlar in a maneuver its way through this much larger pipeline to find and bellows could result in a bellows that is flexible yet resists destroy a plug penetration and can be inflated to pressures in excess of 100 psi. These steel pipes will not allow for the operator to know when the plug has been reached, unlike the clear pipes of the test bed. Beside material selection, design will play a role in the success This will present an opportunity for testing methods of of the new crawler. It will be necessary to form the chosen verifying when a plug has been reached. This last consideration materials such that they serve the desired purpose. The second is of importance because the unplugging cannot take place design improved on some of the weaknesses of the original by unless the crawler is near the plug. There are several ways in not using clamps to hold the bellows to the body. However, it which the location of the plug can be found. One option is to lost flexibility due to its metal bellows, a weakness the first use a camera or sensor on the front of the crawler. These design did not have. The newest design should consist of a electronic components will have to be radiation hardened. flexible bellows with metal flanges on the ends. This will allow There may be commercially available components that are for an air tight seal between the bellows and rims and a simple radiation hardened while still allowing for the crawler to fit bolt on assembly like the second crawler prototype. within the pipes. It may also be possible to find a conventional Simultaneously it will have the flexibility and therefore the camera that can survive long enough for one unplugging speed and cornering capability of the first design. It would be operation. ThermoFisher Company tested one of their ccd preferable to have a bellow that is naturally collapsed and can cameras in a 300 Gy/hr radioactive field and found that it expand. The reason for this is that the pressure from a would survive for one hour [4]. Hanford pipelines have a th compressor can be much greater in absolute magnitude than the radioactive field that is only 1/30 of this level of radioactivity. negative pressure from a vacuum. The crawler always expands Ideally, electronics should be avoided altogether. An inspection faster than it contracts as a result of this. A naturally collapsed device may be placed into the pipeline before the crawler to bellow would help the vacuum to create the contraction as it measure the distance to the plug. The crawler can then be naturally retracts into this position. allowed to crawl the necessary distance, as measured by an encoder on its reel, before beginning the unplugging. It would be ideal to also design and build custom bolt-down clamps that hold the balloons against the rims of the crawler such that they can be added more quickly. The clamps used on the first two prototypes are effective but assembling them to the

ASME 2011 Early Career Technical Journal - Vol. 10 134 REFERENCES CONCLUSION [1] Pribanic, T., Gokaltun, S., McDaniel, D., Varona, J. To prevent the spread of radioactive material into neighboring Awwad, A. Roelant, D. “Summary of Conceptual Designs for soil and ground water around the Hanford site, the DOE must Two Pipeline Unplugging Methods,” ARC Progress Report , move millions of gallons of waste into double shell tanks. September 2009. There have been several instances where plugs form in the [2] Roelant, D., McDaniel, D., Varona, J., Gokaltun, S., Patel, pipelines that are used for carrying out these operations. Due to R., Awwad, A. “Evaluation of Innovative High-Level Waste the fact that the currently available unplugging technologies Pipeline Unplugging Technologies,” ARC Year-End Report, have not been effective, it is necessary to create a technology March 2009. which is. [3] Pribanic, T., McDaniel, D., Varona, J. Awwad, A. There are many crawlers used for process piping in industry, “Evaluation and Development of Innovative High-Level Waste generally for the purposes of pipeline inspection. The peristaltic Pipeline Unplugging Technologies (Peristaltic Crawler),” April crawler for radioactive pipeline unplugging can do more than 2011. inspect a pipe. It carries a pressurized nozzle that can be used to [4]Matos, J., Lee B., Brian P. “Peristaltic Crawler for the destroy a plug. The crawler can maneuver its way through 90° Removal of Radioactive Plugs,” B.S. Thesis, Department of elbows and up vertical sections of pipe. The final design will be Mechanical and Materials Engineering, Florida International made of radiation hardened material that will survive the University, 2010. radioactivity experienced during the entire unplugging [5] “Coefficient of Friction Reference Table - Engineer's operation. This crawler will be most effective for waste Handbook,” Mechanical Engineering Design Guide Engineer’s treatment and processing plants as the pipelines there stretch a Handbook. Web. 5 Nov. 2011. few hundred feet as opposed to several miles. By eliminating . simple, robust, and fault tolerant without worry for the effects [6] “Standard for the Selection of Non-Metallic Materials in of radiation upon it. The pneumatic design also allows the Contact with Tank Waste,” U.S. Department of Energy, Tech. crawler to operate in pipes that are full of water; it is air tight No. TFC-ENG-STD-34, Rev. A, Richland, Washington, 2011. which also means it is water tight. This crawler will be capable [7] Powell, M.R., Golcar, G.R., Geeting, J.G.H. “Retrieval of surviving within Hanford’s pipelines and able to unplug Process Development and Enhancements Waste Simulant them. Composition and Defensibility,” Pacific Northwest National Laboratory, U.S. Department of Energy, September 1997. ACKNOWLEDGMENTS [8] “KEVLAR Aramid Fiber,” Technical Guide,DuPont Corporation, Tech. No. H-77848 4/00. Richmond, Virginia, The authors would like to acknowledge DOE Fellowship undated. program mentor Tomas Pribanic for providing the idea and proof-of-concept for the peristaltic crawler. Many thanks are also extended to Mr. Lee Brady, a colleague and team member who participated in the development of the two crawler prototypes and without whose help this would not have been possible. The authors would also like to thank the DOE Fellows Workforce Initiative and the FIU Applied Research Center for providing the introduction to the Hanford site and its problems along with some of the funding which was needed to develop prototype I.

ASME 2011 Early Career Technical Journal - Vol. 10 135 ASME Early Career Technical Journal 2011 ASME Early Career Technical Conference, ASME ECTC November 4 – 5, Atlanta, Georgia USA

A STUDY OF TISSUE STRAINS INDUCED IN AIRWAYS DUE TO MECHANICAL VENTILATION

Trenicka Rolle, Research Assistant

Dr. Ramana Pidaparti, Professor

Department of Mechanical & Nuclear Engineering

Virginia Commonwealth University

Richmond, VA, USA

ABSTRACT comprise of four components that include: volutrauma, A previous study on the stress/strain environment in the barotraumas, biotrauma and atelectrauma. Techniques to reduce airway tissues performed by Pidaparti and Koombua [1] used a VALI include applications of PEEP (positive end expiratory computational analysis in order to determine the strain pressure), patient positioning, low volume and pressure distribution in each layer of the airway wall. In this study two controlled ventilation [4]. types of airway tissue properties were used, a homogenous and Predisposition to the aforementioned conditions is brought heterogeneous model. They were able to estimate the strain about by the heterogeneous lung mechanics when the patient levels induced within the tissue as a result of the study. The suffers from ARDS or ALI results in the functional capacity of particular behavior modeled was that of linear orthotropic. This the diseased lung becoming reduced [5]. The symptoms of study extends the work by performing computational analysis ARDS and VALI originate in cell-level responses to mechanical using the heterogeneous property with a non-linear and linear loads including stress failure of the epithelial cell membranes isotropic analysis of the airways. The results yielded strains that and cell detachment from the basement membrane as well as were lesser for the non-linear analysis compared to those strains variety of mechano-transduction processes. These symptoms produced within the linear analysis. Whereas stresses produced lead to alveolar flooding which mediates additional lung injury in the non-linear analysis were larger than those produced in the through two mechanisms which include overdistension of the linear analysis. For the non-linear analysis the highest strain remaining aerated alveoli and the reopening of fluid filled distributions were found within the mucosa layer whereas the airways via bubble propagation [2]. The negative effects of lower strain distributions were found in the cartilage layer. mechanical ventilation are shown below in Figure 1.

INTRODUCTION Mechanical Ventilation is a tool that is used in order to assist patients with decreased lung function; such examples include acute respiratory distress syndrome (ARDS), lung injury, disease and paralysis. Specifically, a patient is unable to adequately remove CO2 and maintain appropriate levels of O2 in the arterial blood. The goal of mechanical ventilation is to decrease the work of breathing, increase alveolar ventilation, maintain arterial blood gas values within normal range and improve the distribution of inspired gases. The use of mechanical ventilation may very well be short term or long term but is dependent upon the underlying disorder. Nevertheless, long term use of mechanical ventilation also presents several problems. Resulting from ventilators are injurious mechanical forces that exacerbate the existing lung trauma. These mechanical forces are typically applied to lung epithelial cells and can cause cell necrosis, further barrier disruption and upregulation of inflammatory pathways. These Figure 1. Negative Effects of Mechanical Ventilation. responses lead to additional lung injury known as ventilator- associated lung injury (VALI) or ventilator induced lung injury The lung is a network of branched airways. It branches (VILI) [2]. from the bronchi to bronchioles, specifically terminal VALI is characterized by an increase in static and dynamic bronchioles to respiratory bronchioles to alveolar ducts and lung elastance and tissue resistance [3]. VALI is thought to finally reaches the alveoli where gas exchange of oxygen and

ASME 2011 Early Career Technical Journal - Vol. 10 136 3 carbon dioxide take place. The bronchiole trees are classified Ī1= I1 / √J (2) by generations and by two ordering schemes. Generations count downward from a stem branch, with each child branch one Strain- energy density function: generation higher than its parent. The trachea is classified as 2 generation 1. In this particular study the tissue modeled is with W = µ (Ī1 – 3) + 1 (J – 1) (3) regards to generations 3, 4 and 5. 2 d This study seeks to analyze the stresses and strains induced In using a hyperelastic Neo Hookean model, the isochoric on lung tissue with non-linear properties as well as linear strain-energy density function is defined as: isotropic properties, specifically at each layer as a result of mechanical ventilation. Nevertheless, the main focus is placed ψiso (Ī1) = C10(Ī1 – 3) (4) upon the non-linear analysis. The tissue was characterized using a hyperelastic neo Hookean material model. Where C10 is the stress-like material property and Ī1 is the trace Computational modeling and analysis were performed using the of the right Cauchy Green tensor C. C10 is also defined as µ/2. programs of SolidWorks to generate the model and ANSYS to µ is the shear modulus and based on data from the study of carry out quantitative and graphical analysis of the model. The Trabelsi [10], the value of C10 was found to be 0.56 MPa and tissue model is taken from the organ level and is an initial phase therefore used in this study. of shifting down the lung tree and performing such analysis in order to determine the stress strain environment of alveoli From equation (1) the d term is also defined as K/2. K under mechanical ventilation. With such results it is the goal to represents the bulk modulus, whereas d represents the interpret these results in order to provide tools/methods to incompressibility parameter. Incompressibility of a material is medical professionals that would aid in the reduction and its ability to resist compacting when a load is applied. It can be prevention of VALI. manipulated mathematically. Specifically for finite element modeling in order to attain incompressibility a penalty M ATERI AL M ODEL (hydrostatic) term [last term in equation (1)] in strain energy It has been proved and is now well understood that soft (stress) formulation has to be introduced to enforce the biological tissues are heterogeneous, non-linear, anisotropic and incompressible condition of J = 1. This normally requires the viscoelastic [6]. Biological tissue has a composite structure and selection of a large number for the penalty coefficient (bulk its mechanical properties result from the interactions between modulus). its constituents. Many of these tissues are reinforced by one or The relation of Poisson's ratio and bulk modulus is derived more fiber families, usually consisting of collagen and/or below. By evaluating the derivative of uniaxial stress with elastin. Although the behavior of these tissues is often time- and respect to uniaxial strain at λU =1, the Young's modulus at zero rate-dependent, they can effectively be modeled by assuming strain takes the form, that they are in a ‘preconditioned state’ in which the behavior may be represented as hyperelastic [7]. E= 6(C10+C01) (5) Hyperelasticity is a constitutive model of an ideal elastic material. The behavior of a hyperelastic materials states that a As a result, the bulk modulus, K, can be written as a material behaves elastically even at large deformations. This is function of shear modulus and the Poisson's ratio. The formula possible as a result of the material storing energy used to is, deform it as strain energy. This strain energy is then released upon release of the applied load. These specific types of K = 2(1 – 2*ν) / (C10 – C01) (6) materials are defined by a Helmholtz free-energy function, ψ, [where d = K/2] which describes how the strain energy is stored. There are various hyperelastic models and specifically for this study the The terms of µ and d are of particular importance because in Neo Hookean model was used. It is the simplest of the performing finite element analysis on the tissue model using the hyperelastic models and the lung tissue herein is modeled as an hyperelastic Neo Hookean material model, ANSYS requires the incompressible Neo Hookean material. input of µ and d. Provided that the principle stretches at any deformation states of a material point are λ1, λ2 and λ3, the strain invariants COMPUTATIONAL METHOD are defined as: 3D Geometry. The lung tissue within the airways is considered to be of a heterogeneous material composed of 2 2 2 I1 = λ1 + λ2 + λ3 (1) several layers. These layers include the cartilage layer, smooth J = λ1λ2λ3 muscle layer and submucosa. Figure 2 illustrates the airway tissue model used within this study. The model is a When the volumetric strain is eliminated, the deviatoric representation of that by Kamm [8] as used in the study of strain invariants are written as: Pidaparti and Koombua [1] and details about this and material properties can be found in ref [1]. The thickness of each layer

ASME 2011 Early Career Technical Journal - Vol. 10 137 was obtained from the histological section of the airway tissue therefore calculated as 1.12 MPa. Equations 3 - 6 were those [1]. Table 1 gives the thickness for each airway wall layer as used to calculate parameters for the non-linear analysis. The well as the number of elements and nodes used within the material incompressibility parameter d was calculated to be analysis. 2.14e-8. Both µ and d serve as inputs into the Neo-Hookean option in ANSYS. The second analysis performed was the Table 1. Geometrical Properties of Tissue Model linear analysis in which linear isotropic material model was Airway Wall Layer Thickness (mm) used. This particular property required 2 parameters which Cartilage 240 included E and ν. The Young’s modulus used was calculated Smooth Muscle 115 from equation (7) and was found to be 120 kPa in the Submucosa 55 longitudinal direction and 78 kPa in the circumferential Number of Nodes Linear -233160 direction. This value was previously calculated from the study Non-linear - 31920 of Pidaparti and Koombua [1] and therefore used again. Number of Elements Linear – 159,984 Nevertheless, these values were averaged to attain one elastic Non-linear – 172,283 modulus that would be used in the linear analysis, 99 kPa. For the non-linear analysis the elements were defined using SOLID 185 in ANSYS software and then meshed. The model was meshed at the volumes using tetrahedral shaped elements. On the other hand, for the linear isotropic analysis the elements Cartilage Layer were defined using SOLID 45 in ANSYS and meshed using hexahedral shaped elements.

Table 2. Material Properties of each layer in airway wall tissue. Airway Wall Layer Young’s Modulus (kPa) Mucosa [11] Circumferential 80 Longitudinal 150 Smooth Muscle with Circumferential 75 Cartilage [12] Smooth Mucosa Layer Longitudinal 75 Muscle Layer The Young’s Modulus values from Table 2 were used as inputs

Figure 2. Tissue Analysis Model for equation 7.

E = νmucosaEmucosa+νSMESM +νcartilageEcartilage (7)

The boundary conditions for the model included the use of airway displacements at the organ level at the end of inhalation with 60 L/min constant flow waveform. At the walls of the model all velocity components are zeroed in order to enforce no slip condition. In addition the walls are assumed to be rigid for this study.

RESULTS AND DISCUSSION Non-linear Analysis of Tissue Model. The results for the normal and shear strains and the shear stress for each layer in the tissue were obtained using the non-linear material model. These are briefly described below. Figure 3. Non-linear Finite Element Model of Airway Figures 4 and 5 shows the stress and strain distributions in Tissue the nonlinear analysis and comparison between non-linear and linear analysis. Computational Modeling and Boundary Conditions. The geometry was meshed in the commercially available software ANSYS. A finite element method (FEM) approach was used in order to solve equations. For the FEM analysis the tissue was modeled firstly as a non-linear material with a hyperelastic behavior [9], using the Neo -Hookean material model option. Since C10 is defined to be 0.56 MPa µ is

ASME 2011 Early Career Technical Journal - Vol. 10 138 Non-Linear Analysis of Tissue Comparison of Non-linear and Linear Tissue Strains Strains 4 2 3.5 1.8 3 1.6 1.4 2.5 Cartilage Layer Normal Strain (NL) (%) 1.2 2 1 Normal Strain (L) (%) Smooth Muscle 1.5 Layer 0.8 Shear Strain (NL) (%) Mucosa Layer 1 0.6 Shear Strain (L) (%) 0.4 0.5

0.2 0 0 Cartilage Smooth Mucosa Layer Muscle Layer Normal Strain (%) Shear Strain (%) Layer

Figure 4a: Bar Chart displaying strain results for the non- Figure 5a: Bar Chart displaying comparative analysis of linear analysis various strains for the non-linear and linear analysis.

Non-linear Analysis of Tissue Stress Comparison of Non-linear and 2.50E-02 Linear Tissue Stress

2.00E-02 2.50E-02 2.00E-02 1.50E-02 1.50E-02 1.00E-02 1.00E-02 Shear Stress (NL) 5.00E-03 Shear Stress (MPa) 5.00E-03 MPa Shear Stress (L) 0.00E+00 0.00E+00 MPa

Figure 4b: Bar Chart displaying stress results for the non- Figure 5b: Bar Chart displaying comparative analysis of linear analysis stress results for the non-linear and linear analysis.

ASME 2011 Early Career Technical Journal - Vol. 10 139 Typical shear strain distributions in the mucosa layer are shown each other. The strains in the cartilage layer were smaller in figures 6 and 7. compared to the smooth muscle and mucosa layer. The greatest normal and shear strain values occurred within the mucosa layer. The largest shear stresses were present in the mucosa layer as well. Stiffness in each layer varies and so the strains produce would therefore vary. The mucosa layer is the layer that has the greatest contact with the fluid and air therefore; it would be more so affected by the forces produced that result in the stresses and strains on the tissue. Consequently the results attained are appropriate for this particular analysis. Comparatively the nonlinear analysis produced lesser strains than the linear analysis. However the shear stresses produced within the non-linear analysis were greater than those produced in the linear analysis. Specifically the maximum shear stress for the non-linear analysis occurred within the mucosa layer with a value of 0.02 MPa whereas the maximum shear stress attained in the linear analysis was 1.3e-3 MPa. Figures 6 and 7 illustrate the shear strains produced within the smooth Figure 6: Shear strain distributions in the smooth muscle muscle layer. Examining the model itself it can be seen that in layer for the linear analysis figure 5 the maximum shear strain covers a very small area of that particular layer. On the other hand, the maximum shear strain in figure 6 has a greater distribution in the non-linear analysis. Although the value of the shear strain in the linear analysis is greater than that of the non-linear it is clear that this specific tissue layer in the non-linear analysis deforms more easily. This is true for non-linear behavior especially in the case of soft biological tissue. The main differences between a non-linear and linear analysis are derived from the term stiffness. In terms of this specific study in relation to both models, the tissue within the non-linear analysis is less stiff. Therefore, when a load is applied the tissue will deform to a greater extent. How stiff the model is a result of the geometry, material properties and restraints (boundary conditions). In the linear analysis the tissue is able to retain its stiffness irrespective of the load and Figure 7: Shear strain distributions in the smooth muscle boundary conditions, whereas in the non-linear analysis the layer for the non-linear analysis tissue is stressed and therefore deforms but it stores the energy as strain energy. Hence for the non-linear analysis, the tissue The mechanical behavior of lung tissue is not simply a undergoes higher stresses but the strains are lesser as a result of reflection of the properties of its constituents and in fact bears strain energy being stored so as the load is continually applied little resemblance to the behavior of the individual proteins, to the tissue it continues to absorb the load energy and store it fibers, cells, and fluids of which it is composed [13]. In fact the while experiencing minuscule strains. gross tissue mechanics arise principally from the way in which the components are arranged with respect to each other and CONCLUSIONS how they interact. Furthermore the relationships between these The objective of this study was to perform a non-linear and constituents are numerous and highly non-linear. Therefore it linear analysis in order to determine the tissue strains produced was important to perform a non-linear analysis of the tissue in the airways as a result of mechanical ventilations. model in order to attain a more accurate understanding of the Mechanical ventilation is used when lung function is greatly strains induced. The strains produced as a result of mechanical decreased and requires assistance. Nevertheless, the use of ventilation have the greatest impact on the tissue of the alveoli; mechanical ventilation on a long term basis can cause adverse therefore the analysis takes into consideration the airway walls affects in parenchymal structures of the lung. The lung of the alveoli and the tissue therein. parenchyma is a sponge-like network of alveolated ducts and The strains induced within each layer in the non-linear sacs in which neighboring alveoli share thin, flat walls and a analysis were smaller than those produced in the linear common flow source [15]. These structures undergo pressures analysis. However, in terms of the non-linear analysis alone, that result in volume changes (strains). The strains induced can the strains induced within each layer were quite different from greatly damage the tissue leading to shearing and swelling of

ASME 2011 Early Career Technical Journal - Vol. 10 140 the tissue. This presents major problems in that there are S.N., 2009,“Image-Based Finite Element Modeling of Alveolar secondary responses to such tissue injury. More specifically, Epithelial Cell Injury During Airway Reopening,” J. Appl. the release of inflammatory mediators from lung tissue creates Physiol. 106, pp. 221-232. a cascade of events leading to necrosis of cells and the [3]Ingenito, E. P., and Mark, L., and Davison, B., 1994, activation of neutrophils which ultimately bring about multi- “Effects of Acute Lung Injury on Dynamic Tissue Properties”, system organ Failure (MSOF). J. Appl. Physiol., 77(6), pp. 2689–2697. The biomechanical properties of connective tissues play [4] Cooper, S. J., 2004, “Methods to Prevent Ventilator- fundamental roles in the functioning of almost every organ and Associated Lung Injury: A Summary” Intensive and Critical are critical determinants of how mechanical forces acting on the Care Nursing, 20, pp. 358-365. body/organ produce physical changes at the cellular level [14]. [5] Comerford, A., and Forster, C., and Wall, W. A., 2010, The mechanical forces applied to lung tissue as a result of “Structured Tree Impedance Outflow Boundary Conditions for mechanical ventilation do affect the mechanical properties of 3D Lung Simulations,” J. Biomech Eng., 132(8), pp.081002 the lung and as a result affect the overall function of the lung. (10 pages) Therefore, knowledge of the stress/strain environment induced [6] Fung, Y.C., Biomechanics: Mechanical Properties of Living within the tissues is important to determining how cells are Tissues. second. Springer-Verlag, New York (1993) affected as a result and in particular cells at the alveolar level. [7] Weiss, J.A., and Maker, B.N., and Govindjee, S., 1996, The mechanics of lung tissue exhibit non-linear behavior “Finite Element Implementation of Incompressible, therefore in using a heterogeneous tissue model that was Transversely Isotropic Hyperelasticity”. Comput. Methods characterized by non-linear elastic behavior was studied. The Appl. Mech. Engrg., 135, pp. 107-128. study employed the use of ANSYS to perform a finite element [8]Kamm, R. D., 1999, “Airway Wall Mechanics” Annual analysis. A non-linear simulation was performed using a Review of Biomedical Engineering, 1(1), pp. 47-72. hyperelastic Neo-Hookean material model. The results from the [9] Weichert, L., and Metzke, R., and Wall, W. A., 2009, analysis showed that the strains induced were lower in the non- “Modeling the Mechanical Behavior of Lung Tissue at the linear model when compared to the linear model. This study Microlevel,” J. Engr Mech., 135(5), 434-438. showed that non-linear behavior is characteristic of the lung [10] Trabelsi, O., and Palomar, A. P., and López-villalobos, J. tissue and each layer behaves differently when introduced to L., and Ginel, A., and Doblaré, M., 2010, “Experimental the same loads and boundary conditions in simulation. In order Characterization and Constitutive Modeling of the Mechanical to improve this study it is important to perform a finite element Behavior of the Human Trachea,” Medical Engineering & analysis that takes into consideration a fluid structure Physics., 32(1), 76-82 interaction because the strains induced are not simply structural [11] Yamada H, 1970. “Mechanical Properties of Respiratory but result from the gas-liquid interface at the airway walls. In and Digestive Organs and Tissues”. In: Evans F G (ed.), addition the lungs are a large structure and much of the forces Strength of Biological Materials. Williams & Wilkins, are also found on the surface, therefore when analyzing the Baltimore, MD, p. 145. alveolar tissue within the lungs and assessing strains it’s [12] Jiang H and Stephens N L, 1990. “Contractile properties important to introduce surface loads that account for the surface of bronchial smooth muscle with and without cartilage”. forces on the lungs. Journal of Applied Physiology 69, 120-126. [13] Suki, B., and Bates, J. H. T., 2011, “Lung Tissue ACKNOWLEDGEMENT: The authors thank the National Mechanics as an Emergent Phenomenon” J. Appl Physiol., Science Foundation for supporting this work through a grant 110, 1111-1118. CMMI-0969062. [14] Faffe, D. S., and Zin, W. A., 2009, “Lung Parenchymal Mechanics in Health and Disease”. Physiol Rev 89: 759–775. REFERENCES [15] Dailey, H.L., and Ghadiali, S.N., 2007, “Fluid Structure [1] Pidaparti, R., and Koombua, K., 2011, “Tissue Strains Analysis of Microparticle Transport in Deformable Pulmonary Induced in Airways Due to Mechanical Ventilation,” Molecular Alveoli,” Journal of Aerosol Science., 38, pp. 269-288. & Cellular Biomechanics (MCB), 8(2), pp. 149-68. [2] Dailey, H.L., and Ricles, L.M., Yalcon, H.C., and Ghadiali,

ASME 2011 Early Career Technical Journal - Vol. 10 141 ASME Early Career Technical Journal 2011 ASME Early Career Technical Conference, ASME ECTC November 4 – 5, Atlanta, Georgia USA

OCEAN WAVE ENERGY GENERATOR

Francis S. Fernandez Bader Ale Florida International University Florida International University Miami, Florida, USA Miami, Florida, USA

Alfonso Parra Sabri Tosunoglu Florida International University Florida International University Miami, Florida, USA Miami, Florida, USA

ABSTRACT quickly becomes imperative that alternatives be developed to the point that they become viable and readily available for all Fossil fuels have been a popular source of energy for a people and societies to use. The team considers harnessing and long time. Some of the more prominent drawbacks are its finite using ocean wave energy which can potentially and in the long life and toxic byproducts. Newer technologies have risen to run alleviate the current dependence on conventional fuels. solve this problem. Currently, technologies being researched include devices to harness solar and wind energy. Existing LITERATURE SURVEY wave-generating units are usually around 12 feet high and are designed with the intent of operating in active wave-rich waters Traditional sources of energy have helped propel the with average wave heights of 8 to 10 ft. These units can world’s economy and technology in insurmountable ways. produce as much as 10 kW of power. Along with a smaller- Some of the greatest advancements are not only due to fossil scale design this team explores cost-effective alternatives which fuels, but also greatly depend on them. Additionally, there are could potentially allow smaller buoys to produce less power in serious challenges and consequences associated with their use coasts averaging 2-to-6-foot-high waves. The project also puts such as pollution, ecological disasters, and addicting economic, to use basic laws of electromagnetism, such as Faraday’s Law political and social dependences. Research and development is of Induction and Ampere’s Law. being made on fields related to the advancement of alternative fuel options. These fields extend to solar, wind, electric, bio- INTRODUCTION fuel, and most recently, ocean wave energy [3].

The harnessing of energy is one of the most critical challenges at the forefront of all of humanity’s concerns. It affects societies in almost all aspects including economic, political, military, and technological venues. In recent years renewable energy has become a pressing matter for the latest generation of engineers and researchers. They are confronted with the responsibility of designing environmentally safe products which require less conventional energy or that run on cleaner renewable fuel. This team’s design project is a commitment to further realize these efforts by researching and developing current ocean wave energy technology for the Figure 1 - Components of a Water Wave [6] benefit of all humanity. One of the goals is to achieve the development of small buoy units that are capable of harnessing Figure 1 shows the components that make up a standard energy from ocean waves specific to low-wave-height coastal ocean wave. The approaches used in the development of wave areas such as Florida and Georgia. technology are float or pitching devices, oscillating water columns, and wave surge or focusing devices. Additional Among other alternatives there have been advancements considerations need to be made, such as how far off-shore promoting the use of solar, electrical, bio-fuel, and wind energy. should actual structures stand. The closer to land, the easier it But in order to keep up with the demands of today more becomes to maintain and service these devices. While the progress is needed. Fossil fuels will not last indefinitely and it further away these structures can provide a greater potential for

ASME 2011 Early Career Technical Journal - Vol. 10 142 energy collection. Near-shore devices are generally situated between 30 and 75 feet away from land. A long-standing benefit of wave energy generation includes the ability to produce essentially free energy and requires no additional fuel to operate. Additionally, the costs to maintain energy-generating buoys are on the low end. Also, depending on the location, it can be a major contributor of renewable energy. There are also disadvantages which include the cost it takes to develop worthwhile technology. The variable nature of wave frequency and height also makes the energy- transfer rates unpredictable. It can also disrupt or alter marine life in the vicinity. Deciding how and where these structures will be most beneficial becomes a critical part of the decision- making process. Figure 3 - Magnetic Induction Wave Energy Design [2]

Another technological concept is developed by SIE-CAT which employs a system of buoys configured in a linear fashion to compress air and eventually lead it to a main reservoir tank at the bottom of the ocean. Each buoy is attached to a cylinder and is used to pressurize the air that is being sucked in through an intake valve at the surface. With the help of the undulating behavior of waves the buoy rises to the crest of the wave, creating a partial vacuum in the cylinder. The wave eventually lowers the buoy once it reaches the trough. This is similar to the behavior of an internal combustion engine. Each consecutive Figure 2 - U.S. and FL Coastline Wave Heights (7/24/11) [7] buoy, compressing the air ever so slightly is further compressed The main challenge when making considerations by successive buoys. The final pressure buildup in the reservoir pertaining to wave-harnessing is how these waves affect and tank can then be used to power a turbine to generate electricity. interact with the local environment. In this case, there is the Figure 4 below illustrates a simplified representation on how incorporation of unique features added which would allow an the technology works [4]. existing working design to become more efficient in harnessing less-powerful waves in states such as Florida. The east coast of the United States is the weaker of the coasts when it comes to wave height and strengths, thus smaller and more energy- sensitive design alternatives are preferred. Figure 2 provides a recent snapshot of the wave heights (in feet) for the United States and Florida coastlines, respectively.

EXISTING TECHNOLOGY

There are many designs which prove to be very promising for a research project of this scope. One popular design alternative initially developed in Oregon State University (OSU) primarily involves the use of Faraday’s Law of Induction. The end design is large, bulky, and efficient which enables it to fully take advantage of the wave heights readily available in the western coast of the U.S. Figure 3 shows a conceptual schematic outlining the main features of a wave Figure 4 - SIECAT Compressed Air Energy Design [4] park. OSU’s project is comprised of a multidisciplinary There are other devices known as Pelamis Wave Energy research team that works closely with the Oregon Department Converters which work by making use of cylindrical pontoons of Energy [2]. that are able to float and move about hinge joints such as those illustrated in Figure 5. The Pelamis converters have an energy output rating of approximately 15 kW/m per year. They have also been noted for their performance, cost, design, and overall

ASME 2011 Early Career Technical Journal - Vol. 10 143 efficiency [1]. The Pelamis generators are currently located in However, it allows the engineering team to construct and Edinburgh, Scotland and Povoa de Varzim, Portugal. evaluate parameters critical to the success of the project.

The primary components of the wave power buoy are solenoid, neodymium magnet, and float. The solenoid is designed approximately 1 ft in length and 5 inches in diameter. Two magnets are mated to form one magnet 4 inches in diameter and 4 inches in length. The industry field strength is rated in terms of a hybrid N42-N52. At the surface (2 inches from the center) the magnetic field strength is rated at approximately 2,500 Gauss. At 4 inches from the center the magnetic field rating is approximately 700 Gauss. Magnetic field ratings are usually obtained empirically (through experimentation). However, the mathematical model is based on the equation

Figure 5 - Pelamis Wave Energy Converter [8] ∙=0 (1)

PROPOSED DESIGN In this equation B is the magnetic field and s represents the

closed surface area of the system. Using empirical methods the Two prototypes are considered for the final design. Mass- strengths are determined by extrapolation using the results from producing a product facilitates and in most cases, justifies the Figure 7. high cost of the development and design of molds. In the case of this project, purchasing a mold at a high cost for the production of a single prototype does not justify its price. Field Strength vs Length However, it must be noted that if this team’s product were put 6000 into high volume production the thought process would be 5000 different. Therefore a distinction must be made between the 4000 conceptual prototype, the prototype that would be designed with the intention of mass-production and high durability in 3000 mind, and the modified prototype, or the low-cost alternative 2000 At Surface (4- in Diameter) designed to survive project testing and experimental analysis. A 1000 comparison between both prototypes is shown in Figure 6. As 0 can be noted there are visual differences that set both models 01234 Magnetic Field (Gauss) apart. However, in terms of actual components they remain Length of Magnet (in) very closely related. Figure 7 - N42 Magnetic Field Strength at Surface Area It should be noted that at the surface the magnetic field strength decreases with increasing length of the magnet while at a distance outside of the magnetic surface the field actually increases with increasing length of the magnet. Figure 8 shows the relationship between magnetic field strength and increasing magnet length 2” away from the surface of the 4” diameter magnet.

Figure 6 - Proposed Conceptual and Modified Prototypes For the conceptual design the float is approximately 2 feet in diameter and constructed from industrial insulation The designs mainly differ in areas where it becomes Styrofoam and nylon. The surface finish is protected with extremely expensive and difficult to manufacture parts. The fiberglass resin in order to increase its durability. The case conceptual prototype is the ideology and thought process used containing the magnetic core is anchored from the bottom to in developing a quality product able to withstand long-term the sea floor and thus, remains relatively stationary. The environmental hostilities of the ocean. Its parts and solenoid is attached to the float and as waves produce a functionalities are analyzed without experimental testing. The difference in height relative to the core it is free to move in a modified prototype is built based on readily available vertical fashion. The change in magnetic field relative to the alternatives which jeopardize the life and durability of the buoy. solenoid is what causes a flow of current in the solenoid. This

ASME 2011 Early Career Technical Journal - Vol. 10 144 current will then travel outside the solenoid through a secured kilowatts per meter and horsepower per ft. As noted earlier, water-proof outlet and into a battery located nearby. these values represent only the amount of power that could potentially be harnessed by technologically feasible means. As science advances the efficiency with which this power can be Field Strength vs Length harnessed is improved.

700 600 Table 1 - Power Potential per Wave Height 500 400 4"-Diameter, 2 Wave Height Wave Power Power 300 Inches From (m) Height (ft) (kW/m) (hp/ft) 200 Surface 1 0 0 0 0.0 100 0 2 0.5 1.5 1 0.4 Magnetic Field (Gauss) 01234 3 1 3 4 1.8 Length of Magnet (in) 4 1.5 4.5 9 4.0 Figure 8 - N42 Magnetic Field Strength 2” from Surface 5 2 6 16 7.1 6 2.5 7.5 25 11.2 PROPOSED DESIGN 7 3 9 36 16.1 Ideally the capture of wave energy is desired in offshore 8 3.5 10.5 49 21.9 locations, where it is not only more productive, but can also be 9 4 12 64 28.6 technologically feasible. Even though wave energy can be considered a form of continuous source since it is constantly Additionally, by using equation (2) it is possible to develop being generated it is also highly variable. This is not to say that a graphic interpretation illustrating the amount of power that is the output cannot be accurately predicted, as with the help of potentially generated versus the wave height. In the graph meteorological advances it has become scientifically and shown in Figure 9 periods of 7, 8, and 9 seconds are used in reliably possible to determine the size and intensity of ocean order to draw a comparison between the power generation and waves within monitored coasts [5]. wave height differentiated by the length of time it takes The equation most often employed to determine the between wave crests. However, it should be noted that the amount of power generated by coastal waves is given by period can be adjusted depending on the location of the wave energy-generating device. As previously mentioned, the = (2) intensity and frequency of waves in the western coast are much 64 more pronounced.

In this equation, P is the generated power. The variable ρ is the density of seawater, 1,025 kg/m3. The variable H represents the 80 wave height, in meters. Variable T is the length period of the wave, in seconds. Finally, g is the gravitational acceleration, 9.8 70 2 m/s . Equation (2) can be reduced to the following. 60

50 ≈0.5 (3) At 8 s Period 40 At 7 s Period

(kW/m) 30 Knowing that a few miles off the coast of Florida the At 9 s Period waves reach an average of approximately 3 ft. (~1 m) with a 20 period of approximately 8 seconds, equation (3) yields 4 kW 10

per meter or 1.79 hp per foot of Florida coastline. It should be per Meter Coastline Power Potential noted that this is the potential power and that the amount 0 0246 harnessed, depending on the method used, can be substantially Wave Height (m) less. Additionally, in coasts where the wave heights are much higher, such as in the western coast of the United States, the Figure 9 - Power Potential vs. Wave Height power potential can be as high as 16 hp per foot of coastline.

Table 1 shows a comparison between the wave heights in both, meters and feet, and the potential power generated in

ASME 2011 Early Career Technical Journal - Vol. 10 145 BUOY DESIGN AND ANALYSIS

Engineering evaluations are performed before the construction and testing of the modified prototype. These analyses entail the relevant mechanical engineering theories that help drive the overall success of the research and design project. For all finite element tests a mesh size of approximately 0.5 inches is used. Figure 10 contains additional details and properties specific to the mesh size. Figure 11 - Magnet and Solenoid Case Temperature Gradient Distribution (1 BTU) The deflection temperatures of schedule-40 PVC are illustrated in Table 2. The average oceanic temperature near the coast of Miami Beach, Florida is 78 °F, with the yearly temperatures fluctuating between 71 and 86 °F. Considering the heat factor alone, PVC is able to withstand these temperatures all year round since the load on the buoy due to the buoyancy effect does not exceed 40 lbs. These values do not take into consideration the tidal and rip current effects that add to the buoy load.

Table 2 - Deflection Temperatures of Schedule-40 PVC

Deflection Pressure (psi) Temperature (°F)

66 167

Figure 10 - System Element Properties 246 125 The engineering analyses were mostly performed using SolidWorks and ANSYS software and included the following: ELECTROMAGNETIC ANALYSIS • Thermal • Electromagnetic • Fluid Mechanics • Kinematic • Buoyancy • Fatigue The current produced in an environment such as the ocean • Dynamic • Force and Stress • Coastal and with the equipment being used is of the alternating type (AC). This is important because in order to produce useful Some of these evaluations are outlined in the following energy the buoy requires that the AC current is converted into sections of this report. To see a complete report of all these DC with one of the many available market products. Since the studies contact Florida International University, Mechanical team’s goal is to generate 12 volts, the current quantity has not and Materials Engineering Department, or Francis S. Fernandez been set as one of the primary objectives. at [email protected]. The calculations for the magnetic field analysis are managed by using Ampere’s Law, equation (4): THERMAL ANALYSIS = (4) In terms of thermal properties PVC is a poor conductor of heat and thus, the analysis and results are consistently monotonous. The results for the magnet and solenoid case Since testing magnetic fields require experimental analyses temperature gradient distributions are shown in Figure 11. application software aids in determining the values of magnetic fields at different distances from a given magnet. In this case a magnetic calculator is used provided by the manufacturer of the magnet. Imported magnets are rigorously tested to match the results predicted by field-calculating software. For example, a magnetic field strength of 2743 Gauss is recorded at the surface for a magnet of grade N42 and dimensions 4” (diameter) and 3” (length).

ASME 2011 Early Career Technical Journal - Vol. 10 146

As shown in Figure 12, the magnetic strength decreases The density can now be found by using the relationship from 2743 Gauss to 613.3 Gauss when the distance is increased from 0 (at the surface) to 2 inches from the surface (4 inches 0.826 = = from the center of the magnet). This is a significant decrease 0.571 (9) that would have a tremendous impact on results when designing = 1.447 / a buoy that must allow for a medium (water) to flow through it. The density of seawater is ≈ 1.988 / (10)

When comparing this value to the density of the magnet case it is observed that the density of water is greater than that of the case. Therefore, if fully submerged the magnet case floats.

PROTOTYPE CONSTRUCTION

The team first tests the prototype under a controlled environment. The buoy is taken to one of the team member’s house pool. This way the size of the waves and frequency can Figure 12 - Magnetic Strength 2 Inches from the Surface be controlled. The buoy is safely monitored and minor BUOYANCY ANALYSIS adjustments are made accordingly. The buoy is also taken to be tested in the ocean. Figure 13 shows the team preparing to Ensuring that the system remains buoyant is critical to the deploy the buoy at Biscayne Bay, Florida. success of the buoy. The main components, the magnet case and solenoid case, are analyzed and tested for buoyancy. The equation for the buoyancy force is

= . = = (5)

For equation (5) ρ is the density of the submerged mass, g is the gravitational acceleration, and V is the volume displaced by the submerged mass. This equation is also known as Archimedes’s Principle. In order to calculate the buoyancy of the magnetic case, the volume is determined by using

0.375 = = 5.17 = 0.571 (6) Figure 13 – From Left: Dr. Tansel, Alfonso, Bader, Francis 4 4

The buoy results are given in terms of voltage and current For equation (6) V is the volume, D is the diameter of the pipe, output. Additionally, the wave frequency is adjusted to simulate and L is the length of the pipe. The gravitational acceleration ocean water conditions. Buoyancy and ability to stand are constant is given as monitored and analyzed.

= 32.2 (7)

Also, the mass of the submerged body is needed. In this case this can be found by weighing the body and dividing the result by the gravitational constant

26.6 = = = 0.826 (8) 32.2 / Figure 14 - 2011 Biscayne Bay Buoy Launch

ASME 2011 Early Career Technical Journal - Vol. 10 147 The energy output during the bay testing was less than 3 environments with low wave heights, such as the eastern coast volts for all results recorded. However, had the buoy been of the United States. properly positioned and anchored at the correct level the voltage could have been more in line with the results obtained It is important that research is made with interdisciplinary from the pool, where the buoy was properly anchored and teams, including expert areas in electrical engineering and positioned. Once the tests are completed the team heads back to marine sciences. The success of follow-up work requires that shore. The original intent was to generate 5 W with a larger such teams maintain technical communication so that the magnet. The results of these tests are listed in Table 3. The performance of power buoys is maximized. average power generation is approximately 0.093 Watts. ACKNOWLEDGEMENTS

Table 3 - Prototype Test Results The team acknowledges and thanks the following persons and organizations for their contribution to this project: Voltage (V) Current (mA) • Dr. Ibrahim Tansel 1 2 1.8 • Rick Zicarelli 2 3 0.575 • International Hurricane Research Center (IHRC) • National Oceanic and Atmospheric Administration 3 12 1.36 (NOAA) 4 3 0.557 REFERENCES 5 10 1.087 6 12 1.891 [1] Bedard, R., Hagerman, G., Previsic, M., Siddiqui, O., Thresher, R., & Ram, B, 2005, Final Summary Report, 7 11 1.02 Project Definition Study, Offshore Wave Power Feasibility 8 10 1.61 Demonstration Project. EPRI Global. [2] Brekken, T., & von Jouanne, A., 2008, Overview of Wave 9 10 0.752 Energy Activities at Oregon State University. Oregon State University. 10 8 0.93 [3] Elwood, D., Yim, S., Amon, E., von Jouanne, A., & Brekken, T. (n.d.), 2008, Experimental force CONCLUSION characterization and numerical modeling of a taut-moored dual-body wave energy conversion system. Journal of This research highlights the benefits that current Offshore Mechanics and Arctic Engineering , 132. technologies are able to bring into mainstream along with new [4] SIE-CAT, 2010, The energy of the future is here. One wave challenges that are presented. One of the main focuses is to at a time. Retrieved July 24, 2011, from www.wave- encourage the use of renewable resources that are currently energy-accumulator.com: http://www.wave-energy- available and in abundance. This team remains hopeful that accumulator.com. further studies and developments are made in the fields of wave [5] U.S. Department of the Interior, 2006, OCS Alternative energy harnessing in the future. FIU’s team construction and Energy and Alternate Use Programmatic EIS Information testing of the prototype proves that there is plenty of room for Center. Retrieved 2011, from www.ocsenergy.anl.gov: improvement in the energy field. Examples of future work http://www.ocsenergy.anl.gov/documents/docs/OCS_EIS_ required include automatic depth adjusters to account for tidal WhitePaper_Wave.pdf. effects and minimization of environmental hazards to and from [6] Adhikary, K., 2010, Environmental Systems. the buoy system. [7] NOAA. National Digital Forecast Database, 2011, NDFD Graphics. The overall goal, research the generation of energy through [8] Pelamis Wave Energy Converter, 2009, Changing Ideas: natural means, such as undulation of ocean waves, has been Pelamis-Wave-Energy-Converter/Electricity. accomplished with mixed success. The overall experimentation of energy production is low. And indeed much more work is needed to further advance the research in this area. However, the theory is sound and with future tweaks and improvements it is possible to generate a significant proportion of energy in this manner. In order to continue building on this research, it is recommended that the buoy be able to efficiently operate in

ASME 2011 Early Career Technical Journal - Vol. 10 148 ASME Early Career Technical Journal 2011 ASME Early Career Technical Conference, ASME ECTC November 4 – 5, Atlanta, Georgia USA

AN EXPERIMENTAL STUDY OF SMALL-SIZED CONICAL SPOUTED BEDS

Mandeep Sharma, Matthew Lousteau and Ingmar Schoegl Department of Mechanical Engineering, Louisiana State University Baton Rouge, LA, USA.

ABSTRACT This paper investigates the hydrodynamic behavior of a small, laboratory scale, conical spouted bed (CSB) by considering the effect of specific system parameters (stagnated bed height, particle size and inlet diameter) on minimum spouting velocity (ums)o, stable operating pressure drop (∆Pms) and maximum pressure drop (∆PM). Experimental results show fair agreement with correlations for (ums)o available in existing literature. Using experimental data, an alternative correlation for minimum spouting velocity is developed. Improvements of Figure 1. Spouting regimes and particle states for different inlet prediction quality are attributed to the inclusion of an additional velocities in the conical contactor [5]: fixed bed (a), stable non-dimensional geometry parameter relating particle diameter spouting operation (b), transition regime (c), and jet spouting (d). to inlet diameter, which is absent from most, previously published correlations. Available experimental data for (ums)o Spouting operation in spouted beds can be subdivided into from tests with small sized CSBs using different particle sizes, several spouting regimes, which are illustrated in Figure 1 inlet diameters and static bed heights show excellent agreement [5].For low inlet flow velocities, the bed remains fixed (Fig. with the proposed correlation. 1a). An increase of the gas velocity above a threshold value establishes stable spouting operation (Fig. 1b). Once INTRODUCTION established, spouting operation continues even below the initial Mathur and Gishler initially introduced spouted beds in 1954 as threshold due to a hysteresis effect. A second, lower threshold is an alternative method for drying moist wheat grains [1]. Since found by decreasing the inlet velocity until the internal spout then, spouted beds have been used extensively for drying of collapses, which determines the ‘minimum spouting velocity’ various granular materials and coating of particles. Spouted bed (ums) o. At high gas velocities, annular and spout zones become reactors are suitable for the treatment of material of wide progressively less pronounced (Fig. 1c), before they can no particle size distribution, irregular shape and high moisture longer be differentiated in jet spouting (Fig. 1d). content [2]. Moreover, spouted beds have been used for the Knowledge of the minimum spouting velocity (ums) is of combustion of solid and heavy liquid fuels [3]. It has also been fundamental importance in the design and operation of spouted proven that conical spouted beds (CSBs) have potential for the beds. The minimum spouting velocity is the minimum gas flash pyrolysis of sawdust and the pyrolysis of plastic wastes velocity needed to maintain spouting operation. Although CSBs and scrap tires [4]. have been actively studied for more than five decades, there is The term ‘spouted bed’ originates from the characteristic still considerable uncertainty about the method of estimating ‘spout’ that is created by a gas jet entering through a central minimum spouting velocity (ums) [6]. The majority of the inlet at the bottom of a conical bed of particles (Figure 1). The papers published by previous authors [7] - [12], as summarized jet entrains particles, which are carried through the central by Bi H. T. [13], are based on the results of model experiments, spout, forming a ‘fountain’ before being deposited in an annular where the effect of a single parameter on the minimum spouting region. This mechanism creates a regular circulation pattern of velocity was determined. Although the correlations as proposed particles through the bed. Thus, spouted beds can be classified by these authors are based on limited data, they did provide as a special case within the larger category of fluidized beds. some guidance for the design of large beds.

ASME 2011 Early Career Technical Journal - Vol. 10 149 Table 1. Range of parameters used in the present analysis Parameters Symbol Range Units Diameter of particle dp 0.483, 1.092 mm Diameter of inlet air pipe Do 3.302, 4.572, 6.35, 9.525 mm Diameter of the upper part of the cone Dc 63.5 mm Diameter of the lower part of the cone Di 3.302, 4.572, 6.35, 9.525 mm Diameter of column Dc 63.5, 69.85 mm Height of the cone Hc 50.8, 58.53, 61.57, 114.55, 115.6 mm Cone angle γ 30, 60 degree Stagnated height of bed Ho 10 – 50, 13.81 – 32.82, 35.20 – 65.23 mm Minimum spouting velocity at Do (uo)ms 2.96 – 61.93 m/s Reynolds number at minimum spouting (Reo)ms 93.84 – 4433.73 - Archimedes number Ar 15885 – 183577 - 3 Density of particles ρp 3960 kg/m Density of air ρ 1.184 kg/m3 -5 Figure 2. Spouted Bed Viscosity of air µ 1.81 x 10 Pa.s Geometry Bed voidage at stagnated bed height εo 0.707 – 0.896 -

With a column diameter of 63.5 mm, the spouted bed used for of bed material was loaded into the conical contactor from the this study is significantly smaller than the experimental setups top of the cylindrical column. Prior to recording data, the used in the available literature. In order to evaluate the charge was vigorously moved by the inlet air supply at a applicability and accuracy of existing correlations for small velocity at which no entrainment was observed. A uniform bed sized conical spouted beds, predictions of these correlations are was obtained when the air flow was abruptly stopped, after compared with experimental results; and effects of stagnated which the stagnant bed height was recorded. Experiments were bed height, particle size, and inlet diameter are analyzed. conducted by incrementally increasing the velocity of air, in each instance allowing sufficient time to reach a steady state EXPERIMENTAL APPARATUS before rotameter and manometer readings were recorded. The Figure 2 illustrates the geometry of the conical spouted bed, flow rate of gas was gradually increased until steady spouting where geometric parameters, physical properties and operating operation was established, after which the flow rate was conditions are listed in Table 1. A schematic for the gradually decreased to a minimum value where a slight experimental setup is shown in Figure 3. reduction in flow rate caused the spout to collapse, which Compressed air at 293.15K was passed through a marked the minimum spouting velocity (ums)o. The same receiving manifold, silica desiccant, and manual control valve process was repeated for different stagnant bed heights, particle before entering the conical contactor. The gas inlet is located at sizes and inlet diameters of the spouted bed. Using up to four the bottom of a conical contactor manufactured using a 3D trials per test, results proved to be highly repeatable, yielding printer, where inlet diameters were 6.35 mm, 4.572 mm and identical results for typical velocity increments of 0.4-0.8 m/s. 3.302 mm, respectively. The upper part of the setup is formed by a transparent plexiglass cylindrical column with a diameter of 63.5 mm. Aluminum oxide particles with two different mean diameters (0.483 mm and 1.092 mm) were used as bed material. The stagnated bed heights ranged between 10 mm and 65.27mm.In preliminary testing, two conical contactors with cone angles of 30° and 60° were evaluated. While minimum spouting velocities were found to be lower for the 30° cone, spouting operation was found to be unstable. This observation is in agreement with published results suggesting optimum CSB cone angles between 40o and 60o [14]. All results reported in the present study were obtained for a 60° cone angle. Air flow rates were metered with two rotameters, one for fine adjustments (0-150 correlated reading) and the other for coarse adjustments (0-4 SCFM direct reading). Two pressure taps, one downstream of a porous plug acting as the distributor at the bottom of the particle bed, and the other above the top of the bed, were used to measure pressure drop with a 16 inch Figure 3. Schematic of experimental set-up: (1) air manifold, (2) water column U-tube manometer. air filter (3), control valve, (4/5) rotameters, (6) air inlet pipe, (7/8) Experiments were performed by following standard pressure taps at bed inlet and outlet, (9) U-tube manometer, (10) procedure as documented in literature [15]. A weighed charge conical contactor, (11) bed material, and (12) cylindrical column.

ASME 2011 Early Career Technical Journal - Vol. 10 150

Figure 4.Typical pressure drops for different spouting regimes. Figure 5.Evolution of pressure drop for decreasing inlet velocity.

RESULTS AND DISCUSSION

EVOLUTION OF SPOUTINGREGIMES

The evolution of pressure drop for decreasing inlet air flow velocity is illustrated in Figure 4 [16]. The minimum spouting velocity (ums)o is correlated to the steep pressure increase at the transition from spouted bed to fixed bed, which in Fig. 4 is located at (ums)o equals to 6.99 m/s. Additional results of interest are pressure drop at stable spouting operating (∆Pms), and maximum pressure drop (∆PM) across the fixed bed. Figure 5 shows pressure drop vs. air inlet velocity for stagnated bed heights Ho ranging between 0.01 m and 0.05 m. The overall trends of the pressure drop curves are similar to the schematic shown in Figure 4. Results reveal that both minimum spouting velocity and maximum pressure drop increase with increasing stagnated bed height. Figure 6. Effects of inlet diameter Do and particle size dp on EFFECT OF STAGNATED BED HEIGHT, AIR INLET minimum spouting velocity (ums)o DIAMETER AND PARTICLE SIZE ON MINIMUM SPOUTING VELOCITY (ums )o increases for increasing particle size (dp), whereas it Figure 6 shows an overview of experimental results from a decreases for increasing inlet diameter (Do). Results are in o 60 conical spouted bed for six data sets, defined by a test agreement with previous experimental work of Olazar [4, 12], o matrix with two particle mean diameters (0.483 mm and 1.092 Bi H. T. [13, 17]. Preliminary testing with a cone angle of 30 mm) and three inlet diameters (6.35 mm, 4.572 mm and 3.302 suggested that the minimum spouting velocity decreases with mm). The minimum spouting velocity (ums)o shows a linear decreasing cone angle, which is in agreement with published increase with increasing stagnated bed height (Ho). Moreover, experimental work by Bi. H. T. [13, 17] and Olazar et al. [4]. Table 2. Summary of operating parameters used previously and in the present study

Particle size Source D (mm) D (mm) D (mm) ϒ (deg) H (mm) H /D (mm) 0 c i o 0 0

3.41 ~ 10.35 Markowski [10] 5.6 ~ 300 300 ~ 1100 5.6 ~ 300 37 3.36 ~ 690 0.6 ~ 2.3 Olazar [12] 0.95 - 25 30 ~ 60 360 60 28 ~ 45 70 ~ 300 0.33 ~ 6.67 Bi et al. [13] 1.16 12.7 ~ 25.4 65 ~ 95.8 38.1 30 ~ 60 80 ~ 335 3.15 ~ 26.38 Choi [18] 2.1 ~ 2.8 21 ~ 35 240 ~ 450 38 60 240 ~ 400 6.86 ~ 19.05 Present Study 0.483, 1.092 3.3 ~ 9.525 63.5 ~ 70 3.3 ~ 9.525 30 ~ 60 10 ~ 65 3.03 ~ 6.82

ASME 2011 Early Career Technical Journal - Vol. 10 151

Figure 7a. Comparison of experiments and correlations for Figure 7b. Comparison of predicted (ums)o with experimental minimum spouting velocity (ums)o at varying stagnated bed heights. data; best performing correlations align with the diagonal line.

Table 3 Summary of correlations [13, 19] for calculating (ums)o

Source Correlation Eqn. Markowski (1983) ( ) = 0.028 . ( ) . ( ) . (1) 0 57 0 48 . 1 27 . . . Choi (1992) ( 푚푠) 표= 2 0.147 표 표 푐 표 ( ) ( ) (2) 푅푒 퐴푟 퐻 ⁄퐷 0 477퐷 ⁄퐷 0 61 Gorshtein (1964) ( ) = 0.174 . [1 + 2 tan( 2) ( )] . tan( 02508) . 0 243 (3) 푢푚푠 표 � 푔퐻표 �휌푝 − 휌⁄휌� �푑푝⁄퐷푐� 퐻표⁄퐷푐 퐷표⁄퐷푐 Mukhlenov (1965) ( ) = 3.32 .0 5( ) tan( 2) . 0 25 −1 25 (4) 푅푒푚푠 표 퐴푟 훾⁄ 퐻표⁄퐷표 훾⁄ .0 33 . 0 55. Tsvik et al. (1967) ( 푚푠)표 = 0.4 ( 표 )표 tan( 2) (5) 푅푒 퐴푟 퐻 ⁄퐷 훾⁄ Olazar et al. (1992) ( ) = 0.126 0 52 . ( 1)24. tan( 20)42 . d > 1 mm (6) 푅푒푚푠 표 퐴푟 퐻표⁄퐷표 훾⁄ p Olazar et al. (1996) ( ) = 0.126 0.5 ( )1 68. tan( 2)−0 57. , d ≤ 1 mm (7) 푅푒푚푠 표 퐴푟 퐷푏⁄퐷표 훾⁄ p Bi et al. (1997) (for 0 39 1 68 −0 57 (푅푒푚푠)표 = [0.30 퐴푟0.27 퐷(푏⁄퐷표 ) ] 훾(⁄ )[( ) + ( ) + 1]/3 (8) Db/Do ≥1.66) 2 2 푅푒푚푠 표 − ⁄ 퐷푏⁄퐷표 �퐴푟 퐷푏⁄퐷표 퐷푏⁄퐷표 퐷푏⁄퐷표 EVALU ATION OF CORRELATIONS FOR MINIMUM correlations display similar trends corresponding to SPOUTING VELOCITY experimental observations, predicted values differ significantly. Most of the correlations available in the literature [13, 19] are While some correlations appear to perform well for this based on results from conical spouted beds that are significantly particular data set, it will be shown that the performance of the larger than the system investigated in this study. Table 2 correlations is not independent of the data, i.e. none of the presents bed geometry and particle size for comparable studies available correlations perform well for all available data. [10, 12, 13, 18]. Furthermore, Table 3 lists eight correlations In order to better illustrate the performance of individual predicting (ums)o in CSBs. correlations, Figure 7b plots predicted (ums)o as a function of Equations (1) and (2) given in Table 3 include the column experimental (ums)o for the same data as shown in Figure 7a. diameter Dc as a parameter. These equations are reported to Each of the symbols represents predictions from a specific work well for large beds, while having limitations when used correlation, which is plotted versus data points obtained from for small beds [13]. Equations (3) through (8) do not include Dc experiments. In theory, predictions should match experimental and are suitable for both small size and large size CSBs, data, i.e. the best performing correlations will align with the although their accuracy needs further verification [13]. diagonal line. Data points below the diagonal reveal Figure 7a shows an overview of predictions from the six correlations that under-predict, whereas data points above the best performing correlations compared to experimental results diagonal correspond to correlations that over-predict. In obtained for an inlet diameter of 6.35 mm, a particle diameter particular, the correlation by Bi, et al. (Eq. 8) over-predicts by a of 0.483 mm and various stagnated bed heights. While all relative error (RE) up to 159.4%, whereas the correlation by Olazar (Eqns. 6 and 7) under-predicts by a RE of -54.5%. In

ASME 2011 Early Career Technical Journal - Vol. 10 152

(a) (b)

(c) (d) Figure 8.Comparison of predictions from selected correlations: (a) Gorshtein, et al., (b) Mukhlenov, et al., (c) Tsvik, et al., and (d) Choi, et al.. compari son, results from correlations proposed by Gorshtein expected. On close inspection, a comparison of minimum (Eq. 3) and Mukhlenov (Eq. 4) appear to perform reasonably spouting velocities for the two different particle sizes reveals well, whereas Choi (Eq. 2) and Tsvik (Eq. 5) suggest significant that predictions for small particles tend to be higher than for over-predictions. large particles; in addition, results show a significant impact of Figure 7 illustrates only one out of a total of six data sets the inlet diameter, with larger diameters predicting higher taken for this study, where in the following, the overall values. While this effect is most obvious in Figs. 8b and 8c, it is performance of each of the individual correlations listed in significantly reduced in the correlation by Choi, et al. (Fig. Table 3 is assessed for all available data sets. Similar to Figure 8d/Eq. 2). The improved performance is attributed to the choice 7b, predicted (ums)o are plotted as a function of experimental of a different set of non-dimensional parameters in comparison (ums)o; instead of plotting predictions from multiple correlations to other correlations; all other equations are dependent on the for one single data set, predictions from a single data Archimedes number, which ties particle size and density correlation are plotted for all available multiple data sets. information into a single non-dimensional parameter as A detailed analysis reveals that all of the correlations in Table 3consistently show relative errors (RE) in excess of 50% = 3 (9) for selected data points. Figure 8 illustrates that analyses using 푔푑푝 휌�휌푝−휌� In particular, the ratio of exponents2 of d and in the all available data sets reveal distinct differences with respect to 퐴푟 휇 p p results suggested by Figure 7, which were obtained for a single Archimedes number is 3, assuming p , whereas it is about data set. In particular, Figs. 8a/b show that correlations that 1.28 in Eq. 2. Thus, the poor performance of 휌available performed well previously tend to under-predict, whereas Figs. correlations is attributed to an incomplete휌 ⨠휌 set of non- 8c/d indicate that other correlations perform better than dimensional parameter that separates the particles size dp from

ASME 2011 Early Career Technical Journal - Vol. 10 153

Figure 9. Plot for predictions from correlation (10) for different Figure 10. Effects of Ho and Do on stable pressure drops (left operating parameters. plot) and maximum pressure drops (right plot). the Archimedes number Ar, which is corroborated by studies by CSBs [11, 16]. Correlations for ΔPM perform poorly, which is Olazar, et al. [4, 12], who proposed separate exponents of Ar attributed to large pressure drops that are significantly impacted for different particle sizes (Eq. 6/7). by inlet design, pressure tap locations and initial state of the In general, the minimum spouting velocity depends on the bed. While correlations for ΔPms show better results, a satisfactory analysis of their performance goes beyond the geometry of the system defined by stagnated bed height (Ho), particle size (d ), inlet diameter (D ), cone angle (ϒ), column scope of the present study. p o diameter (D ), and property data for gas and particles. As long c CONCLUSIONS as the bed stays entirely in the conical section, results do not Conical spouted beds (CSBs) are widely used in drying, depend on Dc [16]. As all data were obtained for a single cone coating, and granulation with the objective of modifying angle, the only parameters affecting the results are Ho, dp, Do and property data. A multi-variable regression for physiochemical properties and appearance of particles, e.g. cosmetics, seeds, fertilizers, candy, and drugs. In addition, experimentally evaluated Reynolds number (Rems)o based on CSBs are used for catalytic polymerization, and have potential the non-dimensional parameters Ar, Ho/Do, and dp/Do yields uses in combustion and/or gasification of heavy liquid fuels and

. solid waste materials (biomass, plastics and tires). Minimum ( ) ( ) . ( ) . = 717.26 (10) spouting velocity and pressure drop over the bed are major 1 23 0 08 0 85 parameters for a spouted bed system, which are used for sizing 푅푒푚푠 표 퐴푟 퐻표⁄퐷표 �푑푝⁄퐷표� Figure 9 illustrates that correlation results show excellent of bed dimensions and selection of auxiliary equipment. agreement with all available data obtained for varying inlet This study presents results for the hydrodynamic behavior diameters and alumina particle sizes. It is noted that additional of a laboratory scale conical spouted bed. In experiments, tests with particles of different densities and spouted beds with minimum spouting velocity (ums)o, pressure drop under stable different cone angles are required for the development of a spouting operating ΔPms and maximum pressure drop ΔPM were universally applicable correlation for small sized conical determined for varying stagnated bed heights (Ho). A test spouted beds. matrix with three different inlet diameters (Do) and two mean

alumina particle sizes (dp) yielded six data sets. Experimental MAXIMUM PRESSURE DROP M AND STABLE ΔP results verified that (ums)o increases with increasing dp and PRESSURE DROP ms ΔP increasing Ho, whereas it decreases for increasing Do. In experiments, both peak pressure drop and stable pressure A comparison of experimental data to results from drop increased with increasing stagnated bed height H , o correlations for (ums)o that are available in literature revealed whereas they increased with decreasing inlet air diameters as that, while trends were predicted correctly, values showed can be seen in Figure 10. Both pressure drops, ΔPM and ΔPms, significant deviations. All available correlations showed were also observed to be higher for larger particle size than relative errors (RE) in excess of 50% for at least one out of the forsmaller particle sizes. six available data sets. An analysis of the results revealed that Stable operating pressure drop ΔPms and maximum predicted values appear to be dependent on the particle size and pressure drop ΔPM have been studied by several researchers, inlet diameter, which indicates an insufficient number of who developed correlations for predicting pressure drops in

ASME 2011 Early Career Technical Journal - Vol. 10 154 dimensionless parameters in existing correlation. As an of Fuel-Rich Mixtures in a Spouted Bed Combustor,” J. alternative, a simple empirical correlation for (ums)o was fitted Combust. Flame, 72, pp. 235-239. to the six available experimental data sets taken for this study, [4] Olazar, M., Aguado, R., Jose, M. J. S., Alvarez, S., Bolbao, where an additional non-dimensional parameter relating J., 2006, “Minimum spouting velocity for the pyrolysis of scrap particle size to inlet diameter was included. While additional tires with sand in conical spouted beds,” J. Powder Technology tests using varying particle densities and cone angles are 165, pp. 128- 132. required for the development of a universally applicable [5] Jose, M. J. S., Alvarez, S., Salazar, A. O., Morales, A. and correlation for small sized conical spouted beds, results from Bilbao, J., 2006, “Treatment of Cork Wastes in a Conical the new correlation show a drastic improvement of prediction Spouted Bed Reactor,” Berkeley Electronic Press, Int. J. Chem. quality. Predicted values show excellent agreement for all Reactor Eng., 6, pp. 1-11. available experimental data with varying inlet diameters, [6] Aravinth, S., and Murugesan, T., 1997, “A General particle sizes and stagnated bed heights. Correlation for the Minimum Spouting Velocity,” Springer- Verlag J. Bioprocess Engineering, 16, pp. 289-293. ACKNOWLEDGEMENT [7] Kmiec, A., 1977, “Expansion of Solid-Gas Spouted Beds,” This material is based upon work supported by the Chem. Eng. J., 13, pp. 143-147. Louisiana State University Council on Research Faculty [8] Gorshtein, A. E., Mukhlenov, I.P., 1964, “Hydraulic Research Grant Program. Resistance of a Fluidized Bed in a Cyclone Without a Grate. Critical Gas Rate Corresponding to the Beginning of Jet NOMENCLATURE Formation,” Zh. Prikl. Khim. (Leningrad), 37(9), pp. 1887– 1893. Ar = g 3 2, Archimedes number [9] Goltsiker, A.D., 1967, Doctoral Dissertation, Lensovet Technology Institute, Leningrad. Db = 푝+ 2 tan( 2), top diameter of the 푑 휌 �휌푝 − 휌��휇 [10] Markowski, A. and Kaminski, W., 1983, “Hydrodynamic stagnated bed, m Characteristics of Jet Spouted Beds,” Can. J. Chem. Eng. 61, 퐷표 퐻표 훾⁄ Dc Diameter of the upper part of the cone, m pp. 377–381. Di Diameter of the lower part of the cone, m [11] Wan-Fyong, F., Romankov, P. G., Rashkovskaya, N. B., Do Diameter of the air flow inlet, m 1969, “Research on Hydrodynamics of the Spouting Bed,” Zh. dp Diameter of fine particles, m 2 Prikl. Khim, 42(3), pp. 609–617. g Accelaration due to gravity, m/s [12] Olazar, M., Sanjose, M.J, Aguayo, A.T., Arnades, J.M., Hc Height of the cone, m Bilbao, J., 1992, “Stable Operation Conditions for Gas-Solid Ho Height of stagnated bed of particles, m Contact Regimes in Conical Spouted Beds,” Ind. Eng. Chem. ΔPM Maximum pressure drop across the bed, Pa Res. 31, pp. 1784–1792. ΔPms Stable or spouting pressure drop across the bed, Pa [13] Bi, H. T., Chaouki, A. J., and Legros, R., 1997, “Minimum (Rems)o = ( ) / , Reynolds number during Spouting Velocity of Conical Spouted Beds,” Can. J. Chem. minimum spouting velocity at the air inlet diameter Eng., 75, pp. 460-465. 휌 푢푚푠 표푑푝 휇 (ums)o Minimum spouting velocity referred to Do, m/s [14] Wang, Z., Bi, H. T., Lim, C. J. and Su, P., 2004, “Determination of Minimum Spouting Velocities in GREEK LETTERS Conical Spouted Beds,” Can. J. Chem. Eng., 82, pp. 11-19. [15] Epstein, N., Lim, C.J., Mathur, K.B., 1978, “Data and 3 ρ Density of air, Kg/m Models for Flow Distribution and Pressure Drop in Spouted 3 ρp Density of solid particles, Kg/m Beds,” Can. J. Chem. Eng., 56, pp. 436–447. µ Viscosity of air, Kg/m/s [16] Jose, M. J. S., Olazar, M., Aguayo, A. T., Arandes, J. M., εo Bed voigage during stagnated bed height and Bilbao, J., 1993, “Expansion of Spouted Beds in Conical Υ Cone angle, radians Contactors,” J. Chem. Eng., pp. 45-52. [17] Bi, H. T., 2004, “A discussion on minimum spout velocity and jet penetration length,” Can. J. Chem. Eng. J., 82, pp. 4-10. REFERENCES [18] Choi, M. and Meisen, A., 1992, “Hydrodynamics of Shallow Conical Spouted Beds,” Can. J. Chem. Eng., pp. 916- [1] Epstein, N., and Grace, J. R., 2011, Spouted and Spout- 924. Fluid Beds, Cambridge University Press, Cambridge, UK [19] Epstein, N., and Grace, J. R., 2011, Spouted and Spout- Chap. 1, pp. 1-14. Fluid Beds, Cambridge University Press, Cambridge, UK [2] Cui, H and Grace, J. R., 2008, “Spouting of Biomass Chap. 5, pp. 82-101. Particles: A Review,” J. Bio resource Tech., 99, pp. 4008–4020. [3] Weinberg, F. J., Bartleet, T. G., Carleton, F. B., Rimbotti, P., Brophy, J. H. and Manning, R. P., 1988, “Partial Oxidation

ASME 2011 Early Career Technical Journal - Vol. 10 155

ASME 2011 Early Career Technical Journal - Vol. 10 156 AUTHOR INDEX

ALE, BADER 142 PIDAPARTI, RAMANA 136 ALI, MOHAMMED 1 PLUNKET, CAITLIN 99 ALWUQAYAN, WUQAYAN 87 POROSEVA, SVETLANA V. 27 AMARCHINTA, HEMANTH 6 RANKIN, AEREL J. 27 AMPIE, LEONARDO 113 RAYEGAN, RAMBOD 78 ARGAW, YACOB M. 73 RODEKOHR, CHAD 99 AZAM, KHIZAR 53 ROLLE, TRENICKA 136 BRANSCOMB, DAVID 99 SAVSANI, POONAM V. 14 CHOI, SEUNG-KYUM 6 SAVSANI, VIMAL J. 14 DASQUE, NASTASSJA 120 SAYYED, RIAZ AKBER 53 FERGUSON, FREDERICK 120 SCHOEGL, INGMAR 149 FERNANDEZ, FRANCIS S. 142 SHAKOOR, ABDUL 53 HEWLIN, Jr., RODWARD L. 39 SHARMA, MANDEEP 149 HOVSAPIAN, ROB O. 27 STONE, THOMAS M. 6 IBRAHIM, ESSAM A. 1 TADEPALLI, TEZESWI P. 33 JEFFERSON, GAIL D. 22 TAO, YONG X. 78 KHALID, ADEEL 60 TOSUNOGLU, SABRI 87, 113, 126,142 KIZITO, JOHN P. 39, 45, 68, 73 WATTAL, REETA 105 KONADU, KWABENA A. 91 WHELTON, ANDREW J. 22 LOUSTEAU, MATTHEW 149 YI, SUN 91 MANTENA, P. RAJU 33 YUILL, AUSTIN 99 MATOS, JOSE 126 McDONALD, ERIN E. 22 MEHMOOD, ARSHAD 53 MUDRICH, JAIME 113

MUHAMMAD, IBRAHEEM R. 45 NGUYEN, TINH 22

OPOKU, RICHARD 68 PACHECO, ANDRES 113 PANDEY, SUNIL 105 PARRA, ALFONSO 142

ASME 2011 Early Career Technical Journal - Vol. 10 157

ISBN 978-1-4507-9223-3

ASME 2011 Early Career Technical Journal - Vol. 10 158