N O T I C E

THIS DOCUMENT HAS BEEN REPRODUCED FROM MICROFICHE. ALTHOUGH IT IS RECOGNIZED THAT CERTAIN PORTIONS ARE ILLEGIBLE, IT IS BEING RELEASED IN THE INTEREST OF MAKING AVAILABLE AS MUCH INFORMATION AS POSSIBLE I 4 NASA Technical Memorandum 82788

NASA Research Activities in Aeropropuision

N82-1bQE4 (Na,A-TM- m ,!7db ) NASA HESkAHCH A ,-T1V1T1kJ IN AEKOPRUNUL:iION j4ASA) 30 p HC A03 /Mr A01 CSCL 11L UUC138 G3/07 U88U5

John F. McCarthy, Jr. and Richard J. Weber Lewis Research Center Cleveland, Ohio

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Prepared for the Twenty-fourth Israel Annual Conference on Aviation 8n(,' Astronautics Tel Aviv, Israel, February 17-18, 1982 t 4 ^6 1r X031 w tic.tiN, od`

RV%SA ^ NASA RESEARCH AL'TIVITIES IN AEROPROPOLSION

John F. McCarthy, Jr.* and Richard J. Weber

National Aeronautics and Space Administration Lewis Research Center Cleveland, Ohio U.S.A.

Abstract located in Cleveland,,Ohio, on the shore of We Erie, is responsible for aeropropulsion (as well NASA is a civilian agency of the U.S. govern- as related ground and space power). As shown in ment, responsible for advancing technologies re- the aerial photograph of Fig. 3, this is a very lated to air transportation. This paper describes substantial installation. The replacement value a sampling of the work at NASA's Lewis Research of our facilities is over 1-1/2 billion dollars; Center aimed at improved aircraft propulsion sys- our staff of 2700 engineers, scientists, and sup- W tems. Particularly stressed are efforts related port personnel has an annual research budget for to reduced noise and fuel consumption of subsonic aeropropulsion of about 125 million dollars. transports. Generic work in specific disciplines Some of our major test facilities are large, high- are reviewed including computational analysis, altitude engine test chambers (Fig. 4), several materials, structures, controls, diagnostics, Dirge subsonic and supersonic wind tunnels that alternative fuels, and high-speed propellers. can operate continuously with a running engine Prospects for variable-cycle engines are also within them (Figs. 5 and 6), and noise teat stands discussed. (Fig. 7).

Introduction Systems Technology

Progress in aviation, dating from the Wright The focused research activities at NASA/Lewis brothers on through today, has been largely paced address the specific needs of all of the major by the performance of the propulsion system. classes of aircraft (Fig. 8). Rather than attempt This paper will describe the role of the National to discuss our work in all categories, this sec- Aeronautics and Space Administration (NASA) and tion will concentrate on the subject of subsonic its efforts toward improved powerplants. transports as an example, with only brief mention NASA vp S established as an independent, later of some other classes. civilian, government agency in 1958, charged by The principal concerns related to large com- Congress with the responsibility for advancing the mercial transports in recent years have been in technologieF necessary for improved air transpor- the areas of environmental acceptability and fuel tation (in addition to the space activities that consumption (Fig. 9). The problem of exhaust are more popularly recognized), Actually our emissions eventually was recognized to be rather aeronautics role is an uninterrupted continuation minor relative to other, non-aircraft pollution of the work of our predecessor agency, the sources, and diminished in public awareness once National Advisory Committee for Aeronautics new combustor technolog y eliminated visible (NACA), which dates back to 1915. smoke. However, the noise and fuel problems are In contrast to our space activities, where not so easily solved. NASA is an operating agency that actually procures and controls space vehicles, our aeronautics re- Noise Reduction sponsibilities are much more limited. Through a combination of research conducted within our own Anyone who lives or works near e, large air- facilities plus contracts with industry or univer- port is very conscious of the airplane noise prob- sities, we attempt to make available the techno- lem. Airport neighbors are becoming increasingly logies that will be required for safer and more sensitive and militant about the intrustion of efficient aircraft. Emphasis is placed on the noise into their lives. In response, more and long-term, high-risk topics that industry is not more airports are be-.n!& forced to limit the un- able to undertake on its own. As a program ap- constrained use. of their facilities. As shown in proaches the point of technical readiness, we Fig. 10, over a ten-year period the number of air- withdraw, leaving it to private companies to carry ports that impose some type of operational con- out product design, development, and production. straint (e.g., preferential runways or flight Within the specific area of propulsion our paths) hAs doubled, Additionally there has been a efforts are organized into two parallel, mutually striking increase in the imposition of out-right supportive categories (Fig, 1); (1) a broad, on- curfews. going generic research program in engine compo It is fortunate that technology has been able nents, overall systems problems, and related basic to offer some major reductions in engine source sciences, and (2) a focused program that responds noise over the years to help alleviate this prob- to the specific needs and characteristics of par- lem (Fig. 10. 1 The early engines were ticular vehicle types. Examples of both cate- extremely noisy. Introduction of the first- gories will be described in this paper. generation low-bypass- (JT3D, JT8D) and NASA's aeronautical rea•larch is conducted the moire-recent high-bypass-ratio engines (JT9D, through a number of laboratories or field centers CF6, RB 211) substantially reduced the tore ex- that ,re dispersed around the United States haust velocity and the associated jet noise. How- (Fig. %;), Of these, the Lewis Research Center, ever, the fan generated a new source of noise, and only strenuous efforts in fan machinery noise sup- *Director, Lewis Research Center. pression (e.g., blade spacing, reduced tip speed, wail treatment) have permitted the total noise to 0 Trenched compressor - an abradable mh;te- decrease as shown. rial is applied to the compressor casing Nnd is cut away or notched by the tips Fuel Consumption of the blades, so that running clear- ances are reduced and tip losses The fuel normally constitutes the single minimized. heaviest portion of a long-range airplane. Con- Stang fairing - the covering over the sequently the performance of the airplane is very thrust reverser mechanism is redesigned sensitive to engine fuel consumption, and reduc- to creata less aerodynamic drag. tion in this parameter has always been a goal of Turbine ACC - active clearance control the engine designer. Thus, very substantial im- reduce tip clearances provements in specific fuel consumption have been Turbine roundness - improved mechanical accomplished during the thirty years of commercial design and material selection reduces jet flight (Fig. 12). However, a new stimulus case distortion during throttle toward a more energy-efficient engine arose in the transients 1970'x. The 1973 oil embargo awoke still- continuing concern about the long-term avail- Energy efficient engine. - The effort ability of petroleum-based fuel. And, even when directed toward an entirely new, advanced available, a ten-fold cost increase (Fig. 13) has io known as the E 3 program. It, too, is prin- greatly increased the operating cost of aircraft cipally a contracted activity with PfiW and GE, and threatened the survival of many si+;lines. with in-house research support to help advance the The NASA response to this crisis, vtarting necessary component technologies. After an ini- in the mid-1970's, had three principal *1ements tial period of analysis and component work, this (Fig. 10. 2 First was a near-term effort to program is now entering a phase of large-scale relieve the immediate problem through modest hardware experimentation and technology valida- improvements in the existing fleet of engines; a tion. The E 3 goals (top of Fig. 16) in fuel five-percent saving in fuel consumption was the saving, economy, and environmental acceptability goal here. Second was an all-new engine design, thus far seem to be achievable. The sources of incorporating advanced technologies that would be the fuel benefit are indicated at the bottom of available in the mid-1980'x, with a potential fuel the figure. Discrete component improvements are saving of as much as 18 percent. The third cle- the major contributor. A more advanced cycle ment was a search for unconventional. still- (.higher pressure ratio and bypass ratio) is impor- longer-term concepts, that might be suv- antially tant, and is feasible largely because of those better than even the advanced turbofan. The re- same component advances. Forced mixing of the sult of this search was the advanced , core and bypass streams is another significant with a potential fuel saving of more than factor. 30 percent, The two E 3 designs are rasher similar. Engine component improvement (ECI) program. - Both have on overall pressure xatio '%OPR) of about The ECI program was performed throng~ contracts 37 and a bypass ratio (BPR) of nearly 7. The with Pratt b Whitney Aircraft Company and the maximum turbine inlet temperature at sea-level General Electric Compan , who manufacture the bulk takeoff (T, SLTO) is 100°-200° F higher than in of the engines in the present U.S. commercial today's engines. An example of the aggressive fleet. This program is now completed and resulted component technology is GE's compressor pressure in identifying practical means for improving the ratio of 23 in only 10 stages, with a polytropLc three major engines in current service by 4-6 per- efficiency of over 90 percent. Active clearance cent (Fig. 15). Some of these techniques are control is used on both the compressor and turbine. economically practical to retrofit; others will be Advanced turboprop. - The fuel savings ut ; lized in future production models. promised by E3 are the result mostly of improved In the JT8D engine, for example, Pratt b thermodynamic efficiency of the core. An entirely Whitney is already providing an improved outer air different approach is suggested in Fig. 17, which seal for the high-pressure turbine plus a more- shows propulsive efficiency, that is, the effi- effectively-cooled blade with bleed air discharged cie*.cy with which core work is converted into use- at the root. These two turbine changes reduce the ful propulsive force on the airplane. Note that specific fuel consumption (SFC) by about two per- the available back in the 1950's were cent. It is estimated that the corresponding very efficient. Their replacement by pure jet fleet fuel saving during the remaining lifetime of devices was not because of better efficiency but this engine type will be 880 million gallons. because of such things as higher speed and produc- Another aspect of the ECI program involved tivity, higher altitude for smoother, all-weather obtaining an understanding of the causes of engine capability, etc. In our quest for ways to improve deterioration during service and determining ways beyond the E 3 level of performance, we projected to lessen or recover this decrement. As an illus- that modern technology would offer anew genera- tration of the importance of this problem, it has tion of propellers that again gave the high been found that the JT9D engine, after 3000 flight. propulsive efficiency of the past but without cycles, typically worsens in SFC by about three sacrificing the high speed and high altitu^e we percent. Normal maintenance of hot-section parts enjoy in modern airliners. retrieves about one percent of this deteriora- How this improvement is to be achieved will tion. Work under the ECI program has found that be discussed in the second part of this paper. If cost-effective refurbishment of cold-section parts we accept the attainment of high propeller effi- can regain another 1 to 1-1/2 percent. Addition- ciency for the time being, the impact on airplane ally it appears that the unscheduled engine re - fuel saving is shown in Fig. 18. Depending on the moval rate is cut in half by this refurnishment. range, an advanced turboprop should provide 15-20 Most of the other items noted on Fig. 15 are percent fuel saving compared to an equal-core - self-explanatory. Some that are not so obvious are technology turbofan. The potential reward for explained below: pursuing this approach is indeed great.

F Camnuter Airplanes blade* of s high- speed compressor. Very good agreement is found with the calculated velocity The pr+ ceding discussion has involved the Cnntours shown on the left side of the figure. type of airplane normally operated by major U.S. trunk airlinaa, 1.a., large, high speed ( Hach num- Nat, isri_,,ia1s bar, 0.8), Ions rarga ( average domestic stage length, 700 milas 'o. Recent deregulation of the The demanding stresses and tamparatures airline industry his given those companias greater within an , coupled with the to- freedom to revise their route structures. In par- quirements for light weight and long life, pose ticular theta is a tondancy to withdraw from unique challenges to the materials researchers. closely spaced, light-traffic city pairs that are Tremendous advances in material copabilitiol have ill-suited to their equipment, In their stead is been accomplished in the past, and imaginative now a rapidly growing group of small airlinaa, which approaches promise still further progress. + As can more efficiently service these markets. These one example (Fig. 2G), non-metallic+ and com- so-called commuter airlines share with their large posites are now being evaluated for introduction cousins a desire for low note* and reduced fuel no into service o pHR polyimide, a Lewis development, consumption, taut their airplane ads are quite appears very attractive as the matrix material in difforantt stap^- lengths are short (about soma c.saposite applications in the cool parts of 100 miles), which reduces the importance of high the engine. It has a temperature capability of speed; hence, their typical propulsion system is a 600 • F, Composites have abright future for modest speed turboprop (Hach number, O.G-O.U). achieving significant increases in component dur- Pas*anger load to rather small, perhaps 30-50 at ability, reducing weight, and ultimately ongino most. They have leas need (and Iasi ability to coat. pay tot) sophisticated engines and airframes. In the hot section of the engine, singla In order to address the needs of this type of crystal suparalloys are just starting to be user, NASA has a Small Transport Airplane Tochoo- Applied . A probable next stop beyond that in- logy ($TAT) program. This program is still in r.cb volves directionally structured materials, such as initial, exploratory study phased Advanced fiber-roinforcemant or oxide dispersion (Fig. airframa configurations are being considered at 25). Now coating techniques will retard corrosion our other field canters (Fig. 19). At Lewis we and oxidation, and can even provide thermal insu- have been assessing, with the halp of the small- lation. Uncooled caramic blades are still beyond engine manufacturers, the potential improvements our grasp, but more modest usage of ceramics in that foresdoable adv4ncad-component technologies nearer at hand. Intensive work is underway on will Afford (Fig. 20). Vary significant benefits ceramic shrouds to seal the gas path at the tur- appear attainable in fuel usa g e, operating cost, bine blade tips. This al pne has a potential to reliability, and noise. reduce fuel consumption by 2 to a parcant. A now concern that has surfaced in the mate- Component Research and Technology rials field involves the cost and availability of vital elements that are used in high-temperature A broad variety of research and technology alloys (Fig. 26). Particularly critical are activities are conducted at Lewis in the various chromium, tantalum, cobalt, and Columbium. These generic component diaciplinea (Fig. 21). A number elements have experienced tremendous price in- of tMose will he discussed in this portion of the creases in recont years. Furthermore, they are paper, vith particular emphasis on those aspects largely imported and subject to disrupted avail- relevant to the subsonic transports considered ability in times of political unrest. A new Carliar. activity is, therefore, being initiated at Lewis called Conservation of Strategic HateriAls Computationasl andim An alvticalm Re search (COSAH). 5 'This is a multi-pronged effort, (1) A near-term goal is to reduce reliance on in the past much of the programs in aero- these alemonts in currant, high-usage alloys propulsion was achieved through axperimantation through substitution of lass criticalelemental and empirical correlations. llowovar, as pictured (2) improved process technology (such as net-shape in Fig. 22, ravolutionsry change in an almost and tailored-structvre processing) to reduce rasaArch techniques is now occurring. Vastly more waste, and (3) development of now alloys based powerful computers are paro4 sting the analytical on materials highly available in the U.S, As A investigation of phanomona that were formerly too longer-term goal. comi)lax to treat except oxpoximantally. Analysis of problems in structures, fluid mechanics, and En g ine Structures Research combustion, both steady state and dynamic, is new becoming it discipline in its own right, In com- Related to materials research, but treated bination with benchmark and validation axperi- as a separate discipline, is the issue of how best ments, improved understanding of the underlying to design the various engine components within physics will enable us to more rationally design the capabilities of the available materials componanta in the future. (Fig. 27). This field treats such topics as An important aidto gonarating confidence in structural dynamics, fatigue and life prediction, the computational results is an aver-incroaa ng fracture mechanics, and composite structure design. ability to ssak.a proeiae experimental measure- A specific now program in this area is called mants. One important now tool for detailed Hot Section Technology (HOST). The intent of this complicated flow fields is the laser mapping of program is to improve our understanding of all tha dopplor volocimater. This Instrument can be em- factors that influence the durability of the hot ployed for accurate, non-intrusive measurements of parts of the engine (combustor, turbine blades and flow velocities within ducts and even within vanes). This long-term program will address im- rotating blade row *. For example, Fig. 23 dis- proved instrumentation, advanced thermal and plays the *assured velocities between the rotor fluid-flow analysis, and advanced structural/life

hL_ analysis Aethods. A comprehensive test program .1-851 TF34, and F-100 in airframes such as the will help validate the analytical models and life- T-38 # 7-5, and V-15 have been initiated. A cur- prediction tools that will be developed. r(snt program involving the A-10/TF34 TENS has been An example of the type of problem to be underway for several years and shows great promise treated is given in Fig. 28. It is essential in for reducing maintenance costs and enhancing the design of cooled turbine blades to be able to operational utility.6 accurately calculate the local heat transfer rates The concept of TENS is shown in Fig. 32. along the surfaces. Small errors can result in Data from both airframe and engine sensors are inadequate cooling, excessive metal tempersturee, collected, stored, and processed by modern elec- and drastic reductions in blado life. The sketch tronics onboard the aircraft. These data then at the left pictures the very complicated three- feed a pilot display and a data collection unit. dimensional, non-steady flow phenomena that must The display gives the pilot routine status and be accurately modeled. The graph at the right alerts him to out-of-tolerance conditions. The shows the results of using two available theoreti- data collection unit is portable and can be cal techniques for predicting the chord-wise directly plugged into a diagnostic console for variation of heat transfer coefficient, account- shop maintenance at the operational unit, as well ing for the transition from laminar to turbulent as providing inputs to appropriate management flow. The experimental results, indicated by the information systems. squares, fail to confirm the theories by a wide The various levels of OCM have been defined discrepancy. This illustrates the challenges that in Ref. 7, and are listed below. Note that level this program will address. 1 is the simplest, and more complicated levels correspond to higher numbers. Controls 1. Simplest fl;i,ght-line Co - No Go fnforma- The early gas turbine engines were all con- tion, e.g., event recording such as limit trolled by hydromechanical devices. As engines exceedence, over temperature, or high+ become more and more complex and controls are vibrations. required to serve more functions, the hydro- 2 Flight-line usage recording including mechanical approach becomes less practical cycle and time counting, combined with (Fig. 29). Electronic coutrois are clearly the established thresholds for maintenance next step, and are just starting to see use in action. limited, back-up roles, The problem is largely 3. Flight-line fault tree analysis to predict one of reliability (Fig. 30). As long as there the time to correct deteriorating overall were only a few control variables, the hydro- performance; e.g., fix by wash, trim, or mechanical system was acceptable: But with carry out other ,maintenance actions. greater number of variables, only the electronic 4. Jet Engine Intermediate Maintenance (JEIM) system is able to cope. Fortunately, progress in inspection, fault tree analysis and re- improved reliability has bean substantial, and place components, e.g., faulty core and there seems little doubt that they will be able to assembly of consistent life remaining satisfy the requirements of even the most sophis- engine. ticated future engines, including eventually a 5. Depot level trending to predict major close interaction with the complete airplane and overhaul, parts consumption, diagnose and flight path. Full-authority digital electronic replace modules, and life limit management. control (FADEC) has now been demonstrated on vari- 6. JEIM diagnose and replace module. ous engines such as the F100 (Fig. 31), and will appear on all future civil and military engines as Present technology is available to go to ap- the industry acquires sufficient confidence in proximately level 4 above. If level b could be this new technology. accomplished in a reliable fashion, considerable Another advanced technology category involves monies could be saved and operational capability digital-compatible sensors and actuators. As could be enhanced for both military and commercial indicated in the figure, we anticipate extensive applications. The U.S. Air Force has taken the use of fiber optics, which has inherent advantages initiative in pursuing the research and technology of simplicity, low weight, and passivity, as well required, and the NASA Lewis Research Center is as compatibility with the digital computer. just now embarking on appropriate projects to assist the Air Force and to provide the research Turbine Engine Monitoring Systems (TEMS) and technology base for commercial applications. The most challenging tasks include sensor develop- Another area where considerable progress is ment for reliable performance under extreme en- being made is that of engine diagnostics, commonly vironmental conditions, minimizing the number referred to as Turbine Engine Monitoring Systems of measurements required consistent with good (TENS). This development has been precipitated by results, interpreting data by analytical or the concept of On Condition Maintenance (OCM), empirical means, reliable fault isolation, and where the military is attempting to structure trending. Progress in these very important areas maintenance programs for engines around need could be of great benefit for future economical rather than around engine flight hours. To imple- aircraft operations. ment OCM it is necessary to know and to be able to predict with reasonable accuracy the health of the Alternative Fuels engine and to isolate required maintenance actions down to the module level for field implementation. Redesign of future engines for lower fuel Both the military forces and the commercial consumption has already been discussed. Another airlines have adop ed various degrees of engine aspect to this problem involves the type of fuel diagnostics into their operations. Perhaps the that will be available to be burned in future most ambitious program is being pursued by the Air engines (Fig. 33). At the present the aviation Force where programs involving engines such as the industry is totally dependent upon petroleum as a source of jet fuel. Furthermore, only a limited •rge-scale acoustic and performance testing, both fraction of each barrel of crude oil can be in wind tunnels and ;tn flight. readily converted by distillation into jet fuel A variety of a!M ernative analytical methods with its tightly specified properties. In the are being explored 41Lbr better understanding of future it is highly likely that other fractions of these high speed, highly loaded propellers. A the barrel may have to be utilized wfth a con- comparison of the predicted performance between sequent increase in production cost. Thin will two recently developed theories and experiment is create pressure to modify and relax the specifica- shown in Fig. 36# both anal)-sea are of the curved tions for jet fuel. Additionally, entirely dif- lifting line type, but only the UTRC (United Tech- ferent sources for fg ssil fuel, may ultimately be nology Research Center) approach recognizes the developed, such as shale and syncrude produced actual shape of the spinner and nacelle. The more from coal. Jet fuel derived from these sources complicated theory does better in following radial might have to differ considerably from today's variations (right side of the figure) but is specifications to be economically feasible. actually poorer in predicting overall efficiency NASA has an effort underway to synthesise and power coeffici-ant. Work is in progress to samples of these possible future jet fuels and to improve these analyses and other, more-elaborate characterize their properties. It is probable approaches. that they will be higher in aromatic content, freeze more readily, and have poorer thermal Variable-Cycle Engines stability. A related activity is, then, to study the impact of these broad-specification fuels on A very interesting new area has been develop- the design and performance of the engine and air- ing in propulsion during the past few years that plane systems. As one example, higher aromatics falls under the general title of variable-cycle have reduced hydrogen content, which tends to engines. This refers to the fact that present increase combustor linertemperature and hurt aircraft engines are basically optimized for a durability. This is illustrated in Fig. 34, which single flight condition However, there are new chows the radiation energy and flame temperature aircraft in the offing that generate unique of conventional jet fuel as compared to an experi- demands for engine versitility. That ie, these mental fuel having about two-percent lower hydro- vehicles will operate in very different speed or gen content. As shown at the left of the figure, altitude regions during a single flight. What the principal difficulty is due to the formation is then desired in the propulsion system is an of fine carbon particles or soot in the combustion ability to modify its operating characteristics to products. The soot persists in the secondary and beat suit each region of flight. Several examples tertiary combustion zones of the test combustor, of these vehicles and associated variable engine and poses a major liner cooling problem. concepts will be presented. A different type of problem is that higher fuel freezing point will hurt fuel pumpability High-Speed Rotorcraft after prolonged exposure of fuel tanks to the chill of high-altitude flight. Study of how to Figure 37 pictures an advanced helicopter. handle these types of problems will alow a balance The so-called "X-wing" rotates in the usual fash- to be struck with fuel cost and availability as ion for vertical lift. Later in flight the rotor affected by different fuel spncifications.8 is stopped and serves as a fixed wing. Forward thrust is provided by turbofan engines, and the High-Speed Propellers top speed capability is about 400 knots. Bleed air from the engines is discharged through leading The great appeal of a high-speed turboprop and trailing edge slots in the rotor blades to engine has already been described, based on the achieve good lift and drag characteristics. presumption that a suitable propeller could be The straightforward apptoach to powering such achieved. A major effort has been mounted by NASA an aircraft ifs to use turboshaft engines to drive to investigate the many technological problems the rotor anti then later to use turbofans for for- that exist for such a device. Figure 35 shows the ward flight. An alternative approach is to use a type of propeller that is evolving from this pro- single engine core for both purposes, alternately gram. It differs considerably from conventional gearing the shaft output to the rotor or to a designs. In order to achieve high-altitude capa- fan. An experimental program is now underway at bility without excessive diameter, many blades are NASA to investigate this type of system, which is necessary. For good efficiency at high flight usually termed a convertible engine. A modified speed, the blades are very thin and are swept. TF-34 engine is being tested. The unique features Flow blockage near the hub is controlled through involve the shafting, gears and clutches, and careful shaping of the spinner and nacelle. The variable inlet and exit guide vanes on the fan. unusual blade shapes will require advanced fabri- Additionally studies are being made o f alterna- cation techniques to assure structural dynamic tive, less conventional ways of achieving the stability and light weight. Other problems that desired convertibility. The benefit of the con- must be solved involve high-horsepower reduction vertible system lies in the weight saving from gears, noise+ and airframe aerodynamic using one, rather than two sets of engines in the interactions. aircraft. A number of alternative designs have been tested in small scale thus far, with very promis- Vertical Takeoff and Landing (VTOL) ing results. Propulsive efficiencies in the order of the 80-percent goal have been measured in the Another type of aircraft with vertical take- wind tunnel at Mach number 0.8. One model was off capability uses jets instead of rotors installed atop the fuselage of a JetStar airplane (Fig. 38). Because there is no rotor, a VTOL and flight tested for noise. Preliminary results airplane can fl,l much faster, even supersonically are that the measured noise was 10 dB less than if desired„ Because of the high power require- expected. We hope soon to be ready to conduct ments of this type of vehicle, it is very desir-

_. li able to be able to vary the tharacteristics of the 'couple of years. Other candidate concepts have engine between takeoff and cruise. also been studied. One approach, illustrated at the bottom of khe figure, is called a tandem fan. 9 In an Concluding Remarks ,otherwise conventional turbofan engine with a two- stage fan, the fan stages are separated by an Depsite the growing maturity of many areas of unusual long Distance. Air-flow entering the aeropropulsion technology, the continuing pres- first fan stage is discharged downward through an sures for improvements ill efficiency and the needs auxiliary nozzle. Aseparate airstream feeds the of new varieties of aircraft are being met by second stage through a second inlet located at the innovative advances in engine components and over- top of the nacelle. This stream emerges at the 11 propulsion systems. The diverse research rear of the engine in the normal fashion, being activities of NASA in both vehicle-focused systems deflected downwards for vertical takeoff. This and generic disciplines will support further major layout o sentially doubles the bypass ratio with progress toward more effective air transportation little increase in frontal area. (The special in the tcmdng years. problems inherent ir. theca auxiliary inlets end nozzles are now being investigated at Lewis.) In References a high-speed application of this device the auxil- iary inlet and nozzle are closed, and air passes 1. Feiler, Charles E.; et al.; Noise Reduction. sequentially through the two fans. This device Aeropropulsion 1979, NASA CP-2092, 1979, can, therefore, vary from ahigh-bypass-ratio, pp. 85-128. low-pressure-ratio turbofan (desirable for la-4- 2. Noted, Donald L.; et al.; Advanced Subsonic speed operation) to a low- bypass high-pressure Transport Propulsion. NASA TM-82696, 1981. engine (desirable for high-speed flight). Another VTOL variable concept is illustrated 3. Smith, C. E.; et al.: Propulsion System Study at the top of Fig. 38. In the Remote Augmented for Small Transport Aircraft Technology Lift System (RALS), a large amount of air is bled (STAT), (R80AEGO68 General Electric Co.; from behind the first fan stage, ducted forward, NASA Contract NAS3-21996.)' NASA CR-165330, heated in a burner, and discharged downward for 1981, lift, Later in flight all the air flows rearward 4. Signorelli, Robert A.; et al.; Materials and through the engine in the usual manner, Although Structure Technology. Aeropropulsion 1979, not shown in the sketch, a large number of NASA CP-2092, 1979. variable-geometry features are also incorporated 5. Stephens, Joseph R.: NASA's Activities in within ?he entire engine in order to achieve good the Conservation of Strategic Aerospace Mate- performance throughout the flight spectrum. rials, NASA TH- 81617, 1980. 6. Christophel, Robert C.: A-10/TF34 Turbine Supersonic Transport Engine Monitoring System (TEMS). Aircraft Engine Diagnostics, NASA CP-2190, 1981. A civilian supersonic transport places great 7. Covert, E. E.; et al.: Turbine Engine demands on the propulsion system. Low noise at Monitoring Systems. USAF Scientifc Advisory takeoff and good subsonic capability usually re- Board Report, to be published by Headquarters quires a high-bypass-ratio engine similar to the USAr Scientific Advisory Board, HQ USAF/NB, previously discussed E 3 . Howeve., the essen- Hashington, D.C. 20330. tial, good supersonic capability is best provided 8. Aircraft Research and Technology for Future by a turbojet-type of device, One variable-cycle Fuels. NASA CP-2146, 1980. concept that has been suggested for thin applica- 9. Luidens, Roger W.; Turney, G. E.; and Allen, tion is pictured in Fig 39. It is basically a J.: Comparison of Two Parallel/Series Flow duct-burning turbofan. 10 The ability to in- Turbofan Propulsion Concepts for Supersonic dependently vary the exhaust temperatures of the V/STOL. NASA TM-82743, 1981. two streams, coupled with some airflow variability 10. Hunt, R. B.; et al.; Noise and Economic Study provided by variable-geometry components, allows for Supersonic Cruise Airplane Research. this engine to satisfy the varying needs of the (PWA-5701-22, Pratt 6 Whitney Aircraft Croup; airplane. Performance, acoustics, and exhaust NASA Contract NAS3-22111.) NASA CR-165423, emissions of this concept have been investigated 1981. with large-scale engine hardware within the past 1

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Figure 1. - Aeronautical propulsion.

AMES LEWIS • ROTORCHAFT • PROPULSION • V TOL • STOL

DAY L.I%vv LEY • FLIGHT • SUBSONIC and SUPERSONIC CTOL • HIGH PERFORMANCE AIRCRAfiT • GENERAL /AVIATION I..r

Figure 2. - Roles of NASA aeronautics field centers. ORIGINAL PAGE BLACK AMA WHITE PHOTOGRAPH

Figure 3. - Le-vis Research Center, Cleveland, Ohio.

Figure 4. - PSL 3&4.

t ORIGINAL PAGE BLACK AND WHITE PHOTOGRAPH

TEST SECTION TEST WOE LOFT x LOFT. AFROUYNAhK —CLOSED LOOP x 4OFT. LONG PROPUl SOON —OPEN LOOP 2 1^t r 4 ^ '

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MACH NO.: 2.0 to 3.5 ALTITUDE: 50,000 to 150.000FT. TUNNEL PRESSURE: 200 to 5000 LB/FIT TEMPERATURE. 15(e to 600OF DRIVE MOTORS 250,000 HP Figure 5. - 10x10 SWT.

Figure 6. - 80 and 9x15.

^^11 ORIGINAL PAGE BLACK AND WHITE P140TOGRAPH

Figure ). - jCGAT enqine on VLF.

FOCUSED ACTIVITIES

Figure 8. - Aero propulsion - vehicle specific. ENVIRONMENT REDUCE NOISE n REDUCE EMISSIONS

ENERGY M/REDUCE FUEL CONSUMPTION NACCELERATE USE OF BROAD PROPERTY FUELS

Figure 9. Aeronautical propulsion - major areas of current national need,

160 AIRPORTS WITH NOISE CONSTRAINTS 155 v/ 120 r 1 80 0 80 aw m CURFEWS z 40

Q ^ 1965 1973 l YEAR Figure 10. - Nolse constraints at major world airports,

ORIGINAL PA %"3E

R I ACK AND W HITE PHOTOGRAPH

LEVI 1 to ....am ^)) )11' '"111 ,614T TRAIN II iS

110

I

Hl AVV TIIAMC 1I ^

^J

90

LMI" 400U RADIO OA TV

t 1 1 t ^ ys^ 1950 1960 11970 1900 1M0 YEAR

Figure 11. - Aircraft noise reduction.

FIRST COMMERCIAL 100 ^^^

90 LOW BYPASS RATIO TURBOFANS

AILATIVII ^ ` wtcw C "^L HIGH BYPASS RATIO TURBOFANS % 70

ENERGY EFFICIENT 50 ENGINE

1950 19m 1970 1980 1990 "PA w/AOOUCI D figure 12. - Improvement). in turhofan !uel efficiency.

ORIGINAL PAGE WACK AND WHITE PrIOTOGRAPH

140 KIEL RlEL 120 OTHER ^O^THER DINECT OPERATING 1 00 1973 COSTS 19751 NOfWG Ft? 100 DOME 3 tK OIfAAfiONJ FUEL PRICE 80

GALLON 80 INTERNA i IONAL

40 DOMESTIC

TO

0 . . 1973 1975 1977 1979 1981 1983 «• YEAR SOURCE CA&

Figure 13. - U. S. airline let fuel prices.

ADVANCED TURBOPROP

m ENERGY EFFICIENT ENGINE

ENGINE COMPONENT IMPROVEMENT

E hmmEhmmahm l 1 low 1985 1990 _ YEAR

Figure 14. - Energy efficient propulsion technology.

1

ORIGINAL PAGETOC' QaPH BLACK AND WHITE F . ^

Figure 15. - Engine component improvement IECD fuel savings.

BENEFITS OF E' y

REFERENCE ENWHE I ENERGY EFFICIENT ENGINE 18% FUEL SAVINGS OPP 26 30OPA 3E 3F EPA 4 3 S 3 5.4% DOC ,7EtNlCTION EPA e E E E T IKTOI 2300 24001 T IKTO) 2ASO 2SW'F ENVIRONMENTAL ACCEYTANLITY

SOURCES OF FUEL SAVINGS

IMPROVED COMPONENTS IMPROVED CYCLE

• ADVANCED A 1100YNAMWIL • HIGHER PRESSURE RATIO

• ACTIVE CLEARANCE CONTROL • HIGHER BYPASS RATIO

• REDUCED OAS PATH LEAKAGE • HIGHER TEM ►EPATUAFt. • HIGHER TEMPERATURE MATERIALS • AEDUCED COOLING

i

IMPROVED NACELLE INSTALLATION MIXED FLOW EXHAUST CO.91-12610

; igure 16. HIGH BYPASS 100 TURBOFAN TURBOPROP 90 1950'S ADVANCED TURBOPROP 1 80

70 ELECTRA—' G0

50 .5 .6 .7 ,8 19 CRUISE MACH NQ Figure 17. - Installed propulsive efficiency at cruise,

30 ^k

4

1 0 — TAKEOFF & CRUISE FUEL DESCENT DOMINATED DOMINATED

0 2000 4000 6000 DESIGN RANGE, NM

Figure 18. • Relative to turbofan-powered aircraft with same level of core technology,

i ORIGINAL PAGE RI ACK AMP WRITE PHOTOGRAPH

I iyur e 14. A •lvanced (uomader airplane.

PROPELLERS ENGINE COMPONENTS

1 MM/•AfOfIW! •

\ ` ^ y^ ^ ^TURfa1N1 COMOUSTUR

t ^\ /' U! MtaOA •^

T .^ / C(NITIIOI AND ACCfsso111f6 1

*APROVfMFNT y K/1!f!tT1 ^ , ♦ ""Mee it f•\ $tat MIS Al TV An TO NMUT !1 n% 11K toll ♦ tKHW 011 MASWSS lt"Y"AM ISM\ MIIAKffr / WPVIWANlRT CD I?W (V onm 111'1 IIMe !W

I iqure Al 'tat prow lsion technology. 1

ORIGINAL PAGE S JA CK A"Jn ►1/N1IE P 11 0T( RA6f`H

I- Figure 21. Aeronautical propulsion

.- WT1N"L Comm"T10N COU/UST011 Moorts"a M1M !U 4 I figure 22. - Computational and analytical research. ORIGINAL PAGE BLACK AND WN1TE P140TOGRAPH

ROTATION 00 j sK /xf V

QT24

Il(M

CALCULATED

Fiqure 23. - Calculated and measured velocity contours.

F iqure 14. PAN poi aide compw ate engint, t omponents. ORIGINAL PAGE BLACK AND WHITE PHOTOGRAPH

TViiBIN^ CUMPVNtNT'i Flu" ReINFORCEO /UP911ALLOY fl1RSINE SLAMS Ox10E

CERAMIC TURSIME All SHROUDS

Figure :S. - Materials for higher temperature turbine components.

-^IdrIN CA - CNII0MKM1 FOR C O N MU MON A[bN T ANC[ TA -TAN? At UM FOR O n IOA TION Af SIS I ANCE CO•COBAtY f011 N16N bTHf NOTN CO COL UMSIUM

CHSIOMCUIM COBALT CNNOMIUM pU M

COLUMBIUM COBALT UM MK'E MCMAS&' SUPPLY DSMUPTIONS

1983 NEW START (PROPOSED) LFAMFM ALLOWS AL MANATI MATIMIALS TAILORCO COMPONENTS LOW WASTV PROCESMS

Figure ?b. - Conservation of strategic materials. ORIGINAL PACE FICACK AND WHITE PHOTOGRAPH NACELLE TURBINE VANF. CONTAINMENT and BLAD[,& ► RING FAN fRAME / FAN B `ES _ ^`

vw 4

STRUCTURAL STRUCTURAL FATIGUE/CREEP/ FRACTURE COMPOSITE Ar.ANALYSIS DYNAMICS LIEF PREDICTION MECHANICS STRUCTURES Figure 77. - Engine structures research.

TURBINE HEAT TRANSFER DEVELOPMENT OF APPROPRIATE

HEAT TRANSFER SCHEMES AND BOUNDARY UYIR IRANSMON EFFECTS FLOW DEVELOPMENT ROUTINES WILL WILL PROVIDE MORE ACCURATE BOUNDARY CONDITIONS TO STRUCTURAL ANALYSTS. m 0 ROTOR FILM FLOW

U.AIIAD, w CAM WMAU R ► " Y RA urraM w, 1.". dig r ~ MMMDA" (ayl 40(. ^vllotlr lA h. no" N.Iq Sill" Kt oft" \;cuAllANC1 MAIN' nl IIIl"411I 0

D • A A A a ow" 14111110 r „^ , ea rw V^ toMS Lana1`' rrt+ vats LAM

Figure 28. - Turbine engine hot section technology. L..-w.

1

ORIGINAL PACE BLACK AND WHITE PHOTOGRAF l i

VV VARIABLE CYCLE mm ^" [NQIMf S 10 ►IrDRawlt^u►MICAt NUMBER OF C ONTROL,I.ED VARIABLES s `N1►

ILECTROMC, WOITAL N 1 1 19so 1960 1970 1900 1990 200 YEAR

Figur Engine, controls evolution

I

PROJECTED ELECTRONIC 0 TECHNOLO(IY RELATIVE MEAN TIME CURRENT ELECTRONIC TECNNOIOpY BETWEEN RAILURES 1 `'"--^.

1970 ELECTRONIC HYDROMECMANICAL TECHNOLOGY

0i 0 1.0 2.0 3.0 RELATIVE NUMBER OF FUNCTIONS um

f igure u. Liv tromp cintroi r rli it) i Iity. ORIGINAL PAGE BLACK AND WHITE PHOTOGRAPH

.4 il

Figu; a 31. - Electronics and applied physics.

MANAGEMENT INFORMATION SYSTEM

1 DATA i COLLECTOR i

^J^ CONTROLS DIAGNOSTIC PILOT ~'--- DISPLAY DISPLAYS INPUT

ELECTRONIC ENGINE SENSOR PROCESSOR INPUT

FLIGHT ' a« 1.11 DATA !;gPUT Figure 32. - Turbine engine monitoring system concept.

ORIGINAL PA,:F BLACK AND WHITE PHQtO;R' 'J

Figure 33. - Alternative ti els R&T.

REAM PRIMARY SECONDARY nRIlARV PAM 70001 70001 7DNI CQ I1VM 20

C AIN LOW NVDROGEN p LOW HYDROGEN C01hE1IN1 I Lill CONILNI full S.S .YD

wlc i IItM7 fr 1 l AAA1 nMPI RA RAO AOfANI TURF, ME ENE NEW ft

ISpD 0 L

Ffgura 34. - Effect o; fuel type on itrme radiation. ORIGINAL PAGE BLACK AND WHITE P' 10TOr.RAPH

Figure 35. Advanced turboprop propulsion system.

tz

1.

V) ui so (Eli) PI dop 'IN3101:U300 H3M0d 1VIN3W313

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'ADN31013J3 IN3HVddV dO 'IN3101M,, 3 Mod ORIGINAL PAGE BLACK AND WHITE FH0T0GrAf)N

PVAO ...''o' CONVERTIBLE Em"t _ IIIIIIIIIIIIIIIF PROPUL SAN SYSTEM

, A kw

Figure 31. - Advanced high speed rotorcraft. ORIGINAL PAGE BLACK AND WHITE PHOTOGRAPH 1

YE LLJ Cr-

Z 4 LL 2 uj a 0 z rr

9 'A T 9D OL 0

LL

w II- I

1114 0 M 4 LLJ I-- 0 2 1 x ORIGINAL PAGE RLACK AND WHITE PHOTOGRAPH

;^ACy wool

41^

VAIIIARE IAN WTORI LOW INSSMNS REVERSER tow IOISSIONS DUCT #MR COANIKILAR OLIN 1WR

Figure 39. Variable stream control engine.