THERMAL STABILITY of HIGH TEMPERATURE FUELS ■ 111111111111,111111111111 Tim Edwards USAF Wright Laboratory Wright Patterson AFB, Ohio

THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS 345 E. 47th St„ New York, N.Y. 10017 97-GT-143

The Society shall not be responsible for statements or opinions advanced inpapers or thscussio- n at meetings of the Society or of its Divisions or Sections, or printed in its publications. Discussion is printed only it the piper is published in an ASME Journal. Authorization to photocopy material for internal or personal use under circumstance not falling within the fair use rprovisionsof the Copyright Act is granted by ASME to libraries and other users registered with the Copyright Clearance Center (CCC) Transactional Reporting Service provided that the base fee of $0.30 per page is paid directly to the CCC, 27 Congress Street Salem MA 01970. Requests for special permiesion or balk reproduction should be addressed to the ASME Technical Publishing Department Copyright 0 1997 by ASME All Rights Reserved . Printed in U.S.A Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1997/78699/V002T06A014/2409024/v002t06a014-97-gt-143.pdf by guest on 28 September 2021 THERMAL STABILITY OF HIGH TEMPERATURE FUELS ■ 111111111111,111111111111 Tim Edwards USAF Wright Laboratory Wright Patterson AFB, Ohio

Joseph V. Atria Fuel Science Department Pennsylvania State University University Park, PA

ABSTRACT temperature of the fuel, two types of deposits are found: thermal-oxidative and pyrolytic. Thermal-oxidative deposits This paper describes recent results of AF- result from fuel reactions with the dissolved oxygen in fuel sponsored research in the thermal stability of high (-70 ppm), and begin to occur at temperatures on the order temperature fuels. At temperatures of 550 'C (1000 'F) of 150 'C (300 'F). The thermal-oxidative stability of jet and above, both thermal -oxidative and pyrolytic deposition fuels has been the subject of much study [7]. Pyrolytic are important. A brief discussion of deposition deposits occur at higher temperatures (-500 'C or higher characteristics and mitigation measures is presented. depending upon residence time), and result from thermal cracking reactions in the fuel. In a given test (or fuel INTRODUCTION system), both types of deposits can occur. For example, the surface deposits in a test where flowing fuel is heated This paper discusses the thermal stability of high to -1200 'F (650 'C) in a stainless steel tube are shown in temperature hydrocarbon fuels for air-breathing vehicles. Figure 1. This type of behavior (non-monotonic deposition For this application, high temperature is defined as a vs temperature) is often observed in high temperature fuel temperature on the order of 550 'C (1000 'F) and above. thermal stability tests, although the explanation for this The fuels in these vehicles are driven to these behavior varies [7-12]. We believe the thermal-oxidative temperatures through their use as a coolant. Several deposition reaches a peak and then decreases because of aircraft and/or engine development programs require high complete consumption of the dissolved oxygen [12,15]. temperature fuels. In general, these applications fall into Note that thermal-oxidative deposition is essentially two major classes: eliminated by fuel deoxygenation. (1) More efficient or higher performance gas turbine At temperatures above approximately 480 'C (900 engines. Efficiency and performance gains are obtained by 'F) in flowing systems, the fuel begins to experience increasing the temperatures and pressures in the engine thermal cracking and other reactions of the base [1,2], resulting in higher heat loads rejected into the fuel. hydrocarbons. When these reactions are . deliberate (2) Hypersonic hydrocarbon-fueled vehicles, where the (because of the extension of the heat absorbing capability maximum speed of these vehicles is limited by the cooling of the fuel), the fuel is termed "endothermic" [4-6]. Whether (heat sink) capacity of the hydrocarbon fuel [3,4]. deliberate or not, thermal reactions of the bulk fuel often The thermal stability of the fuel is usually lead to deposition on surfaces. In non-isothermal tests, as characterized by the amount of deposits that a . given fuel illustrated in Figure 1, pyrolytic deposition is often forms at a given temperature in a given test device. correlated with the maximum fuel or wall temperature Translated to the vehicle, a thermally stable fuel would achieved. create fewer deposits in the fuel system than an unstable For a high temperature fuel system, the fuel would fuel. Deposits can be created on heat exchanger surfaces, pass through a series of heat exchangers, pumps, and filters, injectors, and control valves. Depending upon the control devices. Thermal-oxidative deposits could be a

Presented at the International Gas Turbine Sr Aeroengine Congress Sr Exhibition Orlando, Florida — June 2-June 5,1997

problem for lower temperature heat exchangers and Thermal-Oxidative Deposition ("Foulinol components, e.g., airframe heat exchangers and fuel controls and pumps. Pyrolytic deposits might be found in The thermal-oxidative behavior of fuels has been the hottest heat exchangers and in injectors. Note that in the subject of a great deal of research over the past 40 any given fuel system component, the fuel temperature and years [7]. In aircraft, where general practice limits fuel pressure will vary throughout a vehicle's mission. It is temperatures to 160 t (325 'F), the dissolved oxygen in conceivable that a heat exchanger, for example, would be air-saturated fuel (-70 ppm) is generally only partially subject to thermal-oxidative fouling during one part of a

consumed. As temperatures exceed -370 "C (700 'F), Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1997/78699/V002T06A014/2409024/v002t06a014-97-gt-143.pdf by guest on 28 September 2021 mission and pyrolytic coking during another part of the however, the oxygen is completely consumed for any flight. physically realistic residence time. Thus, all of the high For gas turbines, the most challenging parts of the temperature fuels described in this paper were tested under mission from a fuel cooling standpoint are "idle descent" conditions of complete oxygen. consumption. This (low fuel flow, hot engine) and ground idle (low fuel flow, simplifies the study of the thermal-oxidative stability of fuels low cooling air flow). Acceleration and high speed cruise because many different tests give similar results for a given usually involve relatively high fuel (coolant) flows, resulting fuel under conditions of complete oxygen consumption [14]. in relatively low fuel temperatures. For advanced engines Our study of thermal-oxidative fouling in high-temperature where the fuel may be used to cool hot structures, the most fuels has two major goals: (1) understanding the challenging part of the mission may be where the engine is mechanisms of thermal-oxidative fouling, as a function of hottest. For the scramjet, the most thermally challenging temperature, residence time, heating rate, and other part of the mission is the cruise portion, where static variables, and (2) assessing mitigation measures to control temperatures are high and fuel flows are lower than during or eliminate this type of fouling. acceleration.

20000 g ji —2— deoxygenated fuel. 7 lv test

ion.

deposition: air saturated fuel, 20 hrs it

--e— Sir 54ItUMW fuel. 7 his os 15000

800 . ' 1 X 10" dep ama. 20 hrs Jet A's ./.

7004 face r ./.9 8000 10000 —0—Jet A 2827 6004 su -43--Jet A-1 2747 ive C

t —0—Jet A 2926 •

x Jet A 2980 5004 6000 2 ida — x 5000 4—JPTS 2976

ture, -co JP-7 2818 400 4 l o era

rma JPTS 4000 "P mp

3004 he

0 T Te em 2004 10 20 30 50 2000 0 Test time, hr 100 4 Figure 2. Surface deposition as a function of test 0 0 time for 12 mUmin tests. 0 20 40 60 80 100 120 Distance along tube, cm The deposition rate in tests like those illustrated in Figure 1 is determined by running a series of tests of Figure 1. Typical surface deposition test results. Air- varying test times, then plotting the total thermal-oxidative saturated Jet A 3084, 33 mUmin, 7 hrs, 69 atm. deposition (as measured by carbon bumoff) as a function of test time, as illustrated in Figure 2 for various fuels at a This paper describes recent Wright Laboratory- given flow rate. The slope of the deposition vs test time sponsored research into the characteristics of and line gives the deposition rate (gg/hr), which is usually mitigation of deposition from high temperature fuels. divided by the fuel flow rate (g/hr) to yield a deposition rate Thermal-oxidative and pyrolytic deposition will be in ppm (as shown in Table 1). Note that appreciable discussed separately, although the oxidative reactions can induction times appear, where the deposition initially is not affect the pyrolytic reactions since the oxidative reactions measurable. If consideration of this induction time is occur first [13]. neglected, the calculation of deposition rates may be significantly affected. Figure 2 shows the relative deposition rates for Jet A (JP-8) type fuels, as well as rates for the more thermally stable JPTS and JP-7 fuels. Surface

2 deposition rates correlates well with JFTOT breakpoint, as 500 .C), then the deposition rate at the higher flow rates does filter deposition with the exception of JP-7. would appear to have been reduced compared to the lower flow rates. In reality, the deposition is shifted to higher In a number of tests with widely varying flow rates temperatures as the flow rate increases. This is a simple and complete oxygen consumption, it was found that the consequence of temperature-dependent kinetics. Tests deposition rate (in ppm) was relatively constant. Note that with differing tube diameters were also performed at a fixed the deposition rate expressed in ug/ce-hr (an often-used flow rate. In lower flow rate (-1 mUmin) tests, Jones found unit) would not be constant, but would increase as flow rate the deposition rate dropped as tube diameter increased, Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1997/78699/V002T06A014/2409024/v002t06a014-97-gt-143.pdf by guest on 28 September 2021 increases. The data are shown in Table 2. It is important implying that some part of the deposition process is to understand that the oxygen is completely consumed in diffusion-controlled [15]. As shown in Table 2, the results all of these tests. Note the high wall temperatures at the don't show a clear trend with increasing tube diameter at deposition peak location for the high flow rate tests. If higher flow rates. these tests had been run to a fixed wall temperature (say

Table 1 - Thermal-oxidative deposition rates for tests with complete oxygen consumption. 12 mUmin, 69 atm, 1.4 mm 10 316 SS.

Fuel processing JFTOT total sulfur, induction surface filter breakpt, ppm time, hrs deposition, deposition, C ppm ppm Jet A 2827 straight run 282 763 2 1.6 0.5 Jet A 2980 Merox 288 614 n/a 1.2 (est.) 0.2 Jet A 2926 hydrotreated (?) 288 524 2 1.2 0.1 Jet A-1 2747 hydrotreated 332 37 2 0.8 0.1 JPTS 2976 highly processed 427 o 12 0.12 0.08 JP-7 2818 highly processed n/a o 20 0.07 1.2

Table 2 - Thermal-oxidative deposition rates for complete oxygen consumption tests. Jet A 2926, 69 atm (45 atm for 102,195 mUmin), fuel outlet temperature 480 'C (430 'C @ 102 mUmin, 385'C @ 195 mUmin).

flow rate, furnace tubing res. time to Pe at Tw at fuel T surface mUmin temp., 'C ID, mm dep pk, dep. dep pk, (calc) 4) deposi- sec peak 'C dep. pk, 'C tion, ppm 12 535 7.0 73 110 330 202 1.0 12 560 4.6 31 140 327 199 0.6 12 640 22 5.6 350 377 225 1.2 12 660 1.4 3.5 680 369 246 1.2 33 920 1.4 1 1850 455 222 1.2 102 1200 1.4 0.4(est) (14000) 640 (370) 1.1 195 1200 1.4 0.5(est) (27000) 586 (370) 1.1

Mitioation Measures for Thermal-Oxidative Fouling exposed to air, picking up -70 ppm of dissolved oxygen at sea level. A chemical deoxygenation scheme would use a Many mitigation measures have been studied for reactive additive species to react with the dissolved oxygen thermal-oxidative fouling. In general, these measures fall before the fuel does [22]. One possibility, triphenyl into three categories: fuel deoxygenation, fuel additives, phosphine, originally suggested by Beaver [17], was and surface modification. As shown in Figure 1, fuel studied at WL [18]. It was found• that many other deoxygenation has been found to be very effective in undesirable fuel-additive reactions occurred as the fuel was reducing thermal-oxidative deposition [7,8,16]. heated, preventing the additive from acting purely as an Unfortunately, a flight-weight system for performing fuel oxygen scavenger. This is probably not surprising, deoxygenation has not been developed [22]. Fuel tanks for considering the wide variety of chemical species and aircraft are usually vented to equalize pressure as the functionality present in Jet A/JP-8 type fuels. aircraft climbs and descends. Thus, the fuel is usually

3 The most effective means for reducing thermal- pvrolvtic Deposition ("Coking, oxidative fouling appears to be the use of detergent/dispersant/metal deactivator additives [19]. There is a large body of literature on thermal These additives have demonstrated reductions in cracking of hydrocarbons (e.g., [23]). However, aircraft fuels at high temperatures experience a number of deposition in JP-8 fuels to JPTS levels with the addition of differences from typical industrial conditions. Industrial additive packages at the 100 ppm concentration level [19]. cracking typically occurs at near-atmospheric pressure with Two detergent/dispersant additives were found to be steam-diluted hydrocarbons in large (>2.5 cm (1 inch) ID) Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1997/78699/V002T06A014/2409024/v002t06a014-97-gt-143.pdf by guest on 28 September 2021 effective at high temperatures, as shown in Table 3 [14]. tubes. In contrast, typical aircraft fuel system pressures are Reductions in surface deposition approached 90% for the 35-70 atm (500-1000 psi), the fuel is undiluted, and the Betz 80405 additive, which is undergoing flight tests [19]. passage size is much smaller [24,25]. Thus, it might be The effect of the additives on deposition on a 2 gm filter anticipated that high temperature fuels might show some downstream of the test section was more variable, differences in behavior from industrial experience. In especially for the Mobil additive. particular, coking rates might be expected to be higher in aircraft fuel systems because of the higher hydrocarbon Table 3. Thermal-oxidative deposition results with concentration and the higher surface/volume ratio. additives. Conditions: 12 mUmin, 21 hrs, fuel outlet Pyrolytic deposition from aircraft fuels begins occur at fuel temperatures on the order of 500 'C, T-480 'C, air-saturated fuels, 69 atm. Betz 80405 depending upon residence time. In general, this type of added at 100 mg/L, Mobil MCP-1750 added at 300 deposition appears to be directly related to thermal mg/L. cracking of the fuel. Hydrocarbons crack at various rates depending upon their structure, with paraffins and Fuel additive surface filter dep., isoparaffins being the least stable to cracking, followed by dep., ttg IA cycloparaffins (naphthenes) and aromatics. We have avoided the use of -thermal stability" in this context, since Jet A 2827 none 17633 5970 thermal stability in this paper is used to denote the stability Jet A 2827 80405 2224 2225 relative to deposit formation. This is another illustration that care must be taken with the terms 'thermal stability" and Jet A 2827 MCP-1750 5029 31480 "coking", since they are often used to describe different Jet A 2980 none 8328 2805 things. In addition to the propensity to crack, we have Jet A 2980 80405 953 903 found that some fuel structures are more prone to coking Jet A 2980 ' MCP-1750 1937 2100 than others. Thus, the coking potential of various fuels at a Jet A 2926 none 8917 1935 given temperature consists of two parameters: (1) the Jet A 2926 80405 1601 1555 amount of cracking of the fuel, and (2) the tendency of a Jet A 2926 MCP-1750 2369 1339 fuel to form deposits once cracking has occurred. It is easy JPTS 2976 none 639 1167 to imagine a situation where a fuel that is stable to cracking might form significant deposits once it does begin to crack. This fuel should then be limited to conditions where A surface coating of the silica-type (Silcosteek6) cracking does not occur. For example, JP-7 and JP-8 fuels was also studied at high temperatures and found to be are mostly paraffinic, and crack much more at a given ineffective at reducing thermal-oxidative fouling, aside from temperature than decalin, a naphthene. However, decalin an increase in induction time [20]. This observation is tends to form more pyrolytic deposits than JP-7 and JP-8 at consistent with lower temperature tests, where surface a given temperature, despite the lower amount of cracking. coatings were found to change the oxygen consumption Thus, decalin could have a lower use temperature than JP- kinetics (slow the oxygen consumption), but not 7 or 8, despite its greater stability to cracking. The pyrolytic significantly reduce the overall level of deposition under and thermal-oxidative deposition for several fuels at a maximum fuel temperature of 650 'C (1200 'F) is illustrated conditions of complete oxygen consumption [21]. Note that in Figure 3. The difficulties of using the term 'thermal a delay in oxygen consumption would reduce deposition stability" in this context are evident. under conditions of partial oxygen consumption, but at high Although there is much less information available temperatures (e.g., 370 'C and above) where the oxygen for pyrolytic deposition than for thermal-oxidative consumption is complete, such a slowing would not affect deposition, some generalizations can be made. For a total deposition. In other words, the Silcosteele coating given fuel at a given flow rate (or given residence time), the might shift the oxidative deposition peak in Figure 1 level of deposition is roughly exponential in temperature, as downstream slightly, but the deposition would remain shown in Figure 4. The effect of residence time and roughly the same. cracking is less clear, although comparing the 20% cracking points in Figure 4 indicates that there is a

4 residence time influence on pyrolytic coking levels above and beyond the influence associated with conversion or 10 4 cracking level. Thus, deposition increases with increases in temperature (conversion) for a fixed residence time; PSU batch reactor residence time E 103 (20 % conversion) deposition decreases with increasing temperature for a 0 150 min fixed conversion level. In other words, if the heat loads on - -a-- 1 min a vehicle require a certain level of fuel conversion, it —4-0.02 min Jet A fuel appears that deposition is minimized by reducing residence Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1997/78699/V002T06A014/2409024/v002t06a014-97-gt-143.pdf by guest on 28 September 2021 time. Firm relationships between coking and temperature/residence time are not possible from this data due to the non-isothermality of the test. 2016 carealon Three distinct types of pyrolytic coke deposits laminar flow s have been identified in the literature based upon their morphology: filamentous, amorphous, and graphitic [29-34]. E An amalgamation of several literature mechanisms for the various types of coking is shown in Figure 5. This mechanism is based on near-atmospheric pressure 2 turbulent flow applications, such as ethylene furnaces. We have identified filamentous and amorphous carbon for the first 10'3 time under high pressure fuel system conditions [28,36,37]. 400 450 500 550 600 650 700 750 Examples of filamentous and amorphous carbon are shown Fuel temperature, "C in Figures 6 and 7. We are trying to identify the high pressure conditions which control the formation of the various types of coke deposits. Filamentous carbon is the Figure 4. The relationship between pyrolytic most deleterious form of coke, since it involves the removal deposition (coking) and maximum fuel temperature in of small pieces of the metal surface, weakening the batch [38] and flowing tests. Solid symbols represent material and reducing ductility. This type of coking is 20% conversion. predominant at 650 'C (1200 'F) under steam cracking conditions [30]. In two-hour tests with 760 'C (1400 'F) surface temperatures, it was found that very little initial hydrocarbon filamentous carbon was formed from high pressure jet fuels on typical superalloys [36). No weakening of the thin (0.4 f.r.r mm/0.015-inch wall thickness) superalloy tubes was found. f.r.r lighter hydrocarbons —0- products (gases) a • TOtal thermal rattan heavier hydrocarbons S 7 f.r.r = free • Maximum pyrolytic deposition radical reactions; f.r.r? 1 surface carbon can grow by addition of fluid phase radicals

p alosatumte0 fuel% cyclized intermediates

p 5 mated to -650 'C (1200 7). 740 'C (1360 'F) wetted wan T. -25% cracking ion, (6% for decafin). 33 enLintin. CS atm polymerization

osit 4 1 coaation

dep high molecular weight p. tars 3 hydrocarbons face r

Su 2 -surface? f.r.r 1 I bulk particulates surface carbon (filamentous) surface carbon 0 LLI- ant I Jul A Jet A Jet A JPTS &mot NMI! domain (amorphous) 2026 3084 2827 2976 2810 DSO 13 Figure 5. Coking mechanism adapted from Trimm Figure 3. Cracking from several fuels in a flow [34], Baker [29-32], and Albright [33]. reactor with a residence time of 1-2 seconds.

5 Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1997/78699/V002T06A014/2409024/v002t06a014-97-gt-143.pdf by guest on 28 September 2021

Figure 6. SEM of carbon deposits. 590 °C decalin, 700 psi, laminar flow, 304 SS, 5 hrs.

Figure 7. SEM of carbon deposits. 760 °C wall, 650 °C JP-7, 1000 psi, turbulent flow, Inc° 617, 2 hrs. Mitigation Measures for Pyrolvtic Coking I.8 IC/ 600 We have studied several mitigation measures for 1.4 10' pyrolytic coking. Among the general approaches examined 500 were fuel deoxygenation, additives, and surface treatments. 12 101 P Note the similarity to the mitigation approaches for thermal- 0 oxidative fouling. However, pyrolytic behavior is quite 400 lye

different from thermal-oxidative behavior. For example, Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1997/78699/V002T06A014/2409024/v002t06a014-97-gt-143.pdf by guest on 28 September 2021 8003 o fuel deoxygenation often increases pyrolytic deposition 300 0

[13,20,26]. Thus, It appears that the oxidation products act 6003 ? as a deposit suppresser, at least for pure hydrocarbons. 200 Researchers in the Penn State Materials Science 4000 Department have looked at a number of high temperature 100 pyrolysis-suppressing additives in batch reactors at 450 "C 2000 [27]. The most effective additives in reducing both 0 0 conversion and deposition were benzyl alcohol and tetra- 0 20 40 60 80 103 120 hydro quinoline (TH0). At the -2.5% additive level, these Distance along tube,cm. hydrogen-donating are effective in reducing deposition (but Figure 9. Deposition profile comparing uncoated to not cracking/conversion) in a flow reactor as shown in Silcostee16-coated stainless steel tubes [28]. Figure 8 [26]. It would be preferable to use additives that were effective at lower concentration--those additives have SUMMARY not yet been found. The most effective means of preventing pyrolytic In general, the mechanism of thermal-oxidative coking was found to be the use of inert coatings on the fouling is fairly well understood. Detergent/dispersant metal tube surfaces [28]. These types of coatings have additives, often in combination with a metal deactivator, been found to be effective for industrial applications [29,35]. offer the best means for minimizing thermal-oxidative As shown in Figure 9, a deposited silica coating fouling. In contrast, the mechanism of pyrolytic coking is (Silcostee10) is very effective at preventing coking. The less well understood under aircraft conditions, especially as coating apparently acts as a barrier to the formation of it relates to the various forms of surface carbon catalytic (filamentous) carbon, as is seen industrially in (filamentous, amorphous, graphitic). The most effective steam cracking [23,29]. Earlier Air Force results showing means of minimizing pyrolytic coking appears to be inert that the Silcosteel coating was ineffective in reducing (e.g., silica) surface coatings. pyrolytic fouling [20] were apparently due to the use of the thinner 450 A coating. A strong dependence on coating ACKNOWLEDGMENTS thickness is shown in Figure 9 [28,37]. 8000 - Cracking, Vol% to Gas This work was funded by the Air Force Office of 600 Scientific Research and Wright Laboratory. Penn State Norpar-13 12 -7000 Tetralin 13 research was funded by the Air Force through the U. S. 500 14 Department of Energy, Pittsburgh Energy Technology Norpar-13 -6000 TIT 9 Center. 0a 400 woo Tetralin 0 REFERENCES rt; / 4000 '8 3 300 - I t [1]. Valenti, M., 'Upgrading jet turbine technology,' - 3000 z I Mechanical Engineering, pp. 56-60, Dec. 1995. / 4 . [2]. Steinetz, B. M., Hendricks, R. C., "Engine Seal I aroe - 2000 Technology Requirements to Meet NASA's Advanced 1 Subsonic Technology Goals," Journal of Propulsion and -1000 Power, Vol. 12, No. 4, pp. 786, 1996. 1HO [3]. Heiser, W. H., Pratt, D. T., Hypersonic Airbreathing Propulsion, AIAA Education Series, AIAA, 0 20 40 60 80 100 120 Washington, DC, 1994, pp. 507-510. Distance along tube, cm. [4]. Lander, H., Nixon, A. C., 'Endothermic Fuels for Hypersonic Vehicles,' Journal of Aircraft, Vol. 8, No. 4, pp. Figure 8. Deposition profile of Norpar 13 with 2.5 200-207, 1971. wt% thermal stabilizers added [26]. 12 mUmin, 5 hrs, [5]. Sobel, D. R., and Spadaccini, L. J., 'Hydrocarbon 700 psi. .Fuel Cooling Technologies for Advanced Propulsion," ASME-95-GT-226, June 1995.

7 [6]. lanovski, L. S., "Endothermic Fuels for Hypersonic [25]. Beal, E. J., Hardy, D. R., Burnett, J. C., "Results Aviation," Symposium on Fuels and Combustion and Evaluation of a Jet Fuel Thermal Stability Flow Device Technology for Advanced Aircraft Engines, AGARD-CP- Which Employs Direct Gravimetdc Analysis of Both Surface 536, pp. 44-1 to 44-8, Sept. 1993. and Fuel Insoluble Deposits," 4th International Conference [7]. Hazlett, R. N. Thermal Oxidation Stability of on Stability and Handling of Liquid Fuels, Orlando, FL, Nov. Aviation Turbine Fuels, ASTM Monograph 1, American 1991, DOE/CONF-911102, pp. 245-259. Society for Testing and Materials, Philadelphia, PA, 1991. [26]. Atria, J. V., Edwards, T., 'High Temperature [8]. Taylor, W.F., "Deposit Formation from Cracking and Deposition Behavior of an n-Alkane Mixture,'

Deoxygenated Hydrocarbons. 1. General Features," Ind. ACS Petroleum Chem. Div. Preprints, Vol. 41(2), pp. 498- Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1997/78699/V002T06A014/2409024/v002t06a014-97-gt-143.pdf by guest on 28 September 2021 Eng. Chem. Prod. Res. Dev., Vol 13(2), pp. 133-138, 1974. 501, 1996. [9]. Marteney, P. J.; Spadaccini, L. J. "Thermal [27]. Yoon, E. M., Selvaraj, L., Song, C., Stallman, J. Decomposition of Aircraft Fuel". Journal of Eng. for Gas B., Coleman, M. M., "High-Temperature Stabilizers for Jet Turbines and Power (ASME Transactions) 1986, 108, 648. Fuels and Similar Hydrocarbon Mixtures. 1. Comparative [10]. TeVelde, J. A.; Glickstein, M. R. 'Heat Transfer Studies of Hydrogen Donors," Energy and Fuels, Vol. 10, and Thermal Stability of Alternative Aircraft Fuels, Vol. l". pp. 806-811, 1996. NAPC Report NAPC-PE-87C, Nov. 1983, AD A137 404. [28]. Atria, J. V., Cermignani, W., Schobert, H. H., WI]. Hazlett, R. N.; Hall, J. M.; and Matson, M. "Nature of High Temperature Deposits from n-Alkanes in "Reactions of Aerated n-Dodecane Liquid Flowing Over Flow Reactor Tubes,' ACS Petroleum Chemistry Division Heated Metal Tubes". Ind. Eng. Chem. Prod. Res. Dev. Preprints, Vol. 41(2), pp. 493-497, 1996. 1977, 16, 171-177. [29]. Baker, R. T., K, Yates, D. J. C., Dumesic, J. A., [12). Edwards, T., Zabarnick, S., "Supercritical Fuel "Filamentous Carbon Formation over Iron Surfaces" pp. 1- Deposition Mechanisms,' Industrial and Engineering 21 in Coke Formation on Metal Surfaces, Albright and Chemistry Research Vol 32 3117-3122, 1993. Baker, eds., ACS Symp. Ser 202, 1982. [13]. Edwards, T., Liberio, P. D., "The Relationship [30]. Baker, R. T. K., "Coking Problems Associated with Between Oxidation and Pyrolysis in Fuels Heated to 590 'C Hydrocarbon Conversion Processes, ACS Fuel Chemistry (1100 'F)," ACS Petroleum Chemistry Division Preprints, Division Preprints, Vol. 41(2), 521-524, 1996. Vol. 39, No. 1, pp 92-96, March 1994. [31]. Baker, R. T. K., "Catalytic Growth of Carbon [141. Edwards, T., Krieger, J., "The Thermal Stability of Filaments," Carbon, Vol. 27, No. 3, 315-323, 1989. Fuels at 480 'C. Effect of Test Time, Flow Rate, and [32]. Baker, R. T. K., and Harris, P. S., "The Formation Additives," ASME 95-GT-68, ASME Turbo Expo '95, of Filamentous Carbon," Chemistry and Physics of Carbon, Houston, TX, June 5-9, 1995. P. L. Walker, ed., Vol. 14, 83-165, 1978. [15]. Jones, E. G., Balster, W., Pickard, J. M., "Surface [33]. Albright, L. F., Marek, J. C., 'Mechanistic Model Fouling in Aviation Fuels: An Isothermal Chemical Study," for Formation of Coke in Pyrolysis Units Producing J. Eng. Gas Tur. and Power, Vol. 118, pp. 286-291, 1996. Ethylene," Ind. Eng. Chem. Res., Vol. 27, 755-759, 1988. [16]. Edwards, T., Liberio, P., "The Thermal-Oxidative [34]. Trimm, D. 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