THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS Three Perk Avenue, New York, N.Y. 10016-5990 99-GT-56
The Society shall not be responsible for statements or opinions advanced In papers or discussion at meetings of the Society or of its Divisions or Sedans, or printed in its publications. Discussion Is printed only if the paper is published In an ASME Journal. Authorization to photocopy for internal or personal use is granted to libraries and other users registered with the Copyright Clearance Center ICCO provided 53/article is paid to CCC, 222 Rosewood Dr., Danvers, MA 01923. Requests for special permission or bulk reproduction should be ad- dressed to the ASME Technical Publishing Department. Copyright 0 1999 by AS's& All Rights Reserved Printed In U.S.A. Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1999/78590/V002T02A008/4218087/v002t02a008-99-gt-056.pdf by guest on 27 September 2021 HYDROGEN DONORS: THERMAL STABILIZERS FOR JP-8+100 AT HIGH TEMPERATURES 11111,10111111111 Edwin Corporan and Donald K. Minus Air Force Research Laboratory Propulsion Directorate Wright-Patterson Air Force Base, Ohio 45433-7103
ABSTRACT temperatures (-150 °C) to prevent the formation of carbon The effectiveness of hydrogen donor compounds as deposits. Thus, there is a need to develop fuels with high additives to reduce pyrolytic deposition in JP-8+100 at high thermal stability (capability) characteristics in order to handle the temperatures was assessed. Decalin and 1,2,3,4 expected increased heat loads. Thermal stability, as defined tetrahydroquinoline (THQ) were added to JP-8+100 at 0.5% here, is the resistance of the fuel to decompose and form (decalin only), 1.0 and 2.5% w/w concentrations and tested in a undesirable carbon deposits. These deposits will foul fuel flow reactor at a fuel exit temperature of 600 °C at 5.2 MPa. system components such as heat exchangers, valves, and Measurements of carbon deposits along the tube and gas nozzles and will be detrimental to aircraft performance. Fuel chromatography/mass spectrometry (GC/MS) analysis of the thermal decomposition (carbon deposition) occurs by two major stressed and unstressed liquid fuel were used to assess processes, thermal oxidative and pyrolytic. Thermal oxidative effectiveness of the additive, and the degree of fuel (or autoxidative) deposits occur when the fuel reacts with decomposition. Additionally, liquid-to-gas conversion was dissolved oxygen present in the fuel (-70 ppm), and begin at determined, and the composition of the gas was determined via temperatures around 150°C for conventional fuels. Pyrolytic GC. Experimental results show significant reductions in deposits occur when the fuel itself begins to thermally pyrolytic deposition in JP-8+100 with the additives relative to decompose at temperatures above 450°C. An additive package the baseline fuel. Tests with decalin showed negligible effects has been developed to significantly reduce the production of on thermal oxidative deposits, while THQ produced significant thermal oxidative deposits in JP-8 (Heneghan et al., 1996). JP- increases in thermal oxidative deposits. The effects of the 8 with the thermal stability package, known as JP-8+100, offers additives on fuel thermal decomposition and conversion rates a 55°C increase in allowable bulk maximum temperature, and are also discussed. increases heat sink capacity by 50% over conventional JP-8. The thermal stability package in JP-8+100 has been very INTRODUCTION effective in suppressing autoxidative deposits. However, for The Air Force Research Laboratory's Fuels Branch fuels operating at higher temperatures, i.e. > 450 °C, pyrolytic (AFRUPRSF), of the Propulsion Directorate has recently deposits become a significant problem. A series of compounds established a program to develop the fundamental technologies known as hydrogen donors have been investigated as which support the development of 'controlled' chemically suppressors of pyrolytic degradation of n-alkanes in static reacting fuels for application to existing and future air and reactors (Yoon et al., 1996, Song et al., 1994). These space vehicles (Maurice et al., 1999). The ultimate goal of this compounds donate hydrogen atoms to alkyl radicals formed program is to develop fuels that effectively meet fuel handling during the thermal decomposition of the parent fuel to yield and combustor needs for advanced propulsion systems. It is more stable molecules, thereby reducing further decomposition. clearly recognized that as propulsion system capabilities for Stabilization of the very reactive alkyl radicals via hydrogen manned and unmanned aircraft increase, the thermal loads abstraction inhibits radical decomposition, cyclization, imposed on combustors, airframe and other subsystems aromatization, and condensation reactions that subsequently become of major concern. Fuel is currently used as the primary form pyrolytic carbon deposits (Song et al., 1992). Several means for direct or indirect cooling of avionics and aircraft compounds were identified as effective thermal stabilizers in mechanical systems for military aircraft. The heat sink of reducing the thermal decomposition of the alkane sample in conventional liquid hydrocarbon fuels is limited to moderate static reactors. Recently, several of these additives were
Presented at the International Gas Turbine & Aeroengine Congress & Exhthition IndianapoEs, Indiana — June 7-June 10, 1999 investigated in a flow reactor as thermal stabilizers to reduce hydrocarbons, and then installed in the furnace. The reactor is pyrolytic deposition in JP-8 (Corporan and Minus, 1998). Two of initially purged with nitrogen to displace the oxygen in the the additives, 1,2,3,4 tetrahydroquinoline (THQ) and decalin, system and provide an inert environment. The fuel flow is demonstrated very high potential as thermal stabilizers in initiated and the pressure is regulated with the back pressure reducing both thermal decomposition and pyrolytic deposits in control valve to the desired testing pressures. The furnace is JP-8 at high temperatures. THQ was the more effective of the turned on, and the temperature adjusted to the test exit fuel two, however, it also increased thermal oxidative deposition. By temperature. Minor adjustments are made to the back pressure contrast, only moderate increases in autoxidative deposits were valve during the run to maintain a relatively constant pressure
observed with decalin. throughout the test. The liquid products are collected for Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1999/78590/V002T02A008/4218087/v002t02a008-99-gt-056.pdf by guest on 27 September 2021 The present effort assesses the potential of THQ and chemical analysis two hours after the desired fuel temperature decalin to suppress the formation of pyrolytic deposits in JP-8+ is achieved, and the percent liquid-to-gas conversion, is 100 at 600°C. It also provides insight into the synergy between determined as: the thermal oxidative suppressing package, and the hydrogen donor compounds to mitigate both pyrolytic and oxidative % conversion = Vol. flow inlet - Vol. flow exit X 100 deposits. Vol. flow inlet
EXPERIMENTAL Liquid samples are analyzed using a Hewlett Packard The experimental apparatus consists primarily of a fuel 5890/5971 GC/MS. The percent change in n-C10 - n-C15 reservoir, fuel pump, reactor tube, a furnace and a fuel cooler. alkanes and Cr - Cg alkyl benzenes is determined with the The fuel is pumped through the system at a relatively constant GC/MS trace of the liquid samples using the selected ion volumetric rate with a SSI high performance liquid monitoring (SIM) mode with mass ions of 57 and 91 for the chromatography (HPLC) pump. A 0.5 pm sintered filter is used alkanes and substituted benzenes respectively. Due to the to remove any small particulate in the fuel before entering the complexity of the fuel sample, the concentration change of each system. The fuel flow rate is measured with a MAX positive component is approximated semi-quantitatively based on the displacement flow meter. A needle valve, installed downstream peak areas rather than the absolute amounts (per calibration of the pump, is adjusted to dampen the pressure fluctuations curves). The peak area of each component in the stressed inherent in the reciprocating pump. The fuel passes through the sample is reduced by the fraction of liquid converted to gas to reactor, which consists of a 3.18 mm OD, 1.40 mm ID, 107 cm account for the reduction in the liquid product. The gas samples long 316 stainless steel tube. The reactor tube is enclosed in a are analyzed using a Hewlett Packard 5890 GC equipped with a Lindbergh fumace where the fuel is heated to about 600 °C exit thermal conductivity detector (TCD) for hydrogen analysis and a bulk temperature. The heated fuel is cooled and partially flame ionization detector (FID) for CI-C6 alkane and alkene condensed in a water-cooled section, and filtered through a 2.0 analysis. um sintered filter to capture the solid carbon products. The two- After test completion the reactor tube is removed from the phase fuel products are directed to the facility's vent hood and furnace, cut into 5.08 cm sections, rinsed with heptane, and fuel drain. The fuel pressure is regulated to approximately 5.2 dried for a minimum of two hours in a vacuum furnace. The MPa with a needle valve (back pressure valve) installed tube samples are subsequently analyzed for carbon deposition downstream of fuel cooler. Liquid and gaseous samples are in a LECO RC-412 Multiphase Carbon Determinator. collected at the vent hood for off-line analysis. Gas samples are collected in bags and analyzed by GC, and liquid samples Fuel Additives are analyzed by GC/MS. The densities of the unstressed and Pyrolytic alkane degradation proceeds through a free stressed liquid are determined by weighing a measured volume radical initiated and propagated mechanism (Rice, 1933). This of the sample on a laboratory scale. Temperature thermal degradation is initiated by cleavage of a carbon-carbon measurements on the tube surface are made every 17.8 cm bond then continues through the abstraction of atoms from using spot welded K-type thermocouples. The fuel bulk exit additional fuel species. A series of compounds termed temperature is measured with a 1/8 inch K-type thermocouple hydrogen donors have shown potential in increasing the thermal inserted in the flow at the reactor exit. A second thermocouple stability of n-alkanes (Yoon et al., 1996, Song et al., 1994). The installed approximately 5.0 cm downstream of the first one compounds behave as radical quenchers through the donation provides a redundant measurement. Fuel pressures are of hydrogen atoms to the reactive fuel radicals. By donating measured at the reactor inlet and just upstream of the back hydrogen atoms, the additives become radical species, which pressure valve with Bourdon-tube type pressure gauges. Flow are subsequently converted into stable reaction products by meter and temperature data are collected on a 486 DX4-100 donating additional hydrogen atoms. Displayed in Fig. 1 are personal computer for real time display and post-test analysis. proposed mechanisms for the additives considered in this study, Fuel blends are made by mixing neat JP-8, [commercial THQ and decalin. Jet A (designated POSE 3219) with the °standard° additives (an icing inhibitor, corrosion inhibitor/lubricity enhancer and an anti- RESULTS static inhibitor)], and the BETZ SPEC AID 8Q462 package Fuel was stressed in the reactor tube to a final temperature (-250 ppm) to obtain JP-8+100. Subsequently JP-8+100 is of 600°C flowing at 12 ml/min at 5.2 MPa for six hours. The mixed with decalin or THQ at the concentrations of interest. additives were evaluated in JP-8+100 in 0.5% (decalin only), Decalin and THQ are at 98% purity, and the concentration of 1.0% and 2.5% w/w concentrations. Experiments for each test decalin is approximately 44% cis- I 56% trans-. The reactor condition were repeated at least twice to verify reproducibility of tube is rinsed with acetone to remove any residual the results. Reactor surface temperatures varied from 275°C at
2 a. 1,2.3.4 Tetrahydroquinoline (THQ)
H • H + R • + R • —11■• RH + H RH +
H H Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1999/78590/V002T02A008/4218087/v002t02a008-99-gt-056.pdf by guest on 27 September 2021 Nf + R • + RH 41— RH
OuiNOLINE
b. Decalin
Fig. 1 Proposed Hydrogen Donation Mechanisms for THQ and Decalin
17.8 cm from the tube inlet to approximately 650°C at the tube (300 - 450°C). An increase in deposition is seen at a fuel exit. Fuel temperatures along the reactor were estimated temperature of 450°C at which pyrolytic (thermal cracking) assuming constant surface heat flux and using thermodynamic reactions begin to occur. As expected, the highest pyrolytic properties computed with the NIST SUPERTRAPP program deposits occur at the tube section that experiences the highest (Ely and Huber. 1990) for a surrogate of hydrocarbons to temperature. simulate P-8 (Heneghan et al., 1993). The flow Reynolds Carbon deposition on the reactor surface in ppm is shown numbers varied from 175 at the inlet to 7300 at the tube exit. in Fig. 3. The deposition is determined by dividing the carbon The fuel residence time in the reactor, determined using the deposit weight (ug) (sum of five largest measurements in conservation of mass equation and fuel properties from regime) by the total amount of fuel used (g). As shown, decalin SUPERTRAPP, was approximately four seconds. Reduction in significantly reduced pyrolytic deposits (-50%) at 1.0% w/w pyrolytic deposition was used as criterion for effectiveness of concentration. Negligible differences in pyrolytic deposits were the additive as a thermal stabilizer. Note, that previous work observed at 2.5% and 0.5% w/w concentrations. Thus, an has shown that fuels with low propensity to cracking (which optimum concentration of decalin is required to effectively may imply higher thermal stability), may also form higher suppress pyrolyfic carbon formation in JP-8+100. This pyrolytic deposits (Edwards and Atria, 1995). behavior is not yet fully understood. Further studies in a system which focuses on the elemental chemistry of the fuel, Carbon Deposition e.g. System for Thermal Diagnostic Studies (STDS) (Maurice et The carbon deposition along the reactor tube for the al, 1998), are needed to increase the understanding into the baseline fuel and fuels with additives is shown in Fig. 2. The effects of decalin on the decomposition of the parent fuel. deposits plotted for each fuel blend are mean values of THQ, the most effective hydrogen donor additive in replicated tests (±10% uncertainty). As shown, the thermal reducing pyrolytic deposition in JP-8 (Corporan and Minus, oxidative and pyrolytic regions can be easily. identified. The fuel 1998), also suppressed total pyrolytic deposition in JP-8+100. begins to react with oxygen at a fuel temperature of Reductions of 20% and 30% were obtained with THQ at 2.5% approximately 150°C to produce thermal oxidative deposits. and 1.0% w/w concentrations respectively. THQ, however, also The deposits peak at about 240 °C and most of the oxygen in increased thermal oxidative deposition (5-6 times) relative to the fuel is consumed at a fuel temperature of 300 - 340 'C after the baseline JP-8+100. These results corroborate previous which there is very little deposition in the intermediate regime work by Penn State University researchers which showed that
3 1000 650 -13- BASELINE -A- DECALIN 0.5% -600 900 + DECALIN 1.0% • -X- DECALIN 2.5% • -550 - ID- THQ 1.0% 800 - THQ 2.5% - -500
700 - -450 calcutated fuel temperature ,- Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1999/78590/V002T02A008/4218087/v002t02a008-99-gt-056.pdf by guest on 27 September 2021
) —11• -400 ug
( 600 ion it 500 s dep os
bon 400 - • Car 44 Aclative 300 __-200 • Pyralyta -150 200 - -100
-50
0 0 10 20 30 40 50 60 70 80 90 100 110 Distance along reactor (cm)
Fig. 2 Carbon Deposition Curves
0.900 JP8+100 LH Decalin 0.5% 0.600 - Decalin 1% ODecalin 2.5% . _.._ _._ . EssTHQ 1.0% .THQ 2.5% 0.700 -
0.600 —
0.500 - IO. g 'r. 0.400 - - g o. ° 0 . _. 0.300 - \------\ r
• i \N___.____ . ,
„.„ );106.
, tc. 0.000 ,,,„ti,4 P yrolytic Oxidative Type Deposition
Fig. 3 Pyrolytic and Oxidative Deposition in JP-8+100 at 600°C THQ was susceptible to autoxidation at lower temperatures appearance, no appreciable differences were observed (Coleman et al, 1998). They attribute this behavior to the between stressed and unstressed liquid fuels' densities. As chemical and structural characteristics that make THQ an expected, reductions in the additives concentrations as well as effective hydrogen donor compound. This increase in the reaction products for decalin and THQ, naphthalene and autoxidative deposits has been observed previously in flow quinoline respectively, were observed in the stressed liquid reactor tests with JP-8/THQ blends (Corporan and Minus, samples. Analysis of the stressed JP-8+100/decalin fuel 1998), however, the deposition increase is considerably more showed reductions in both cis- and trans-decalin components. pronounced in JP-8+100. Considering the high reactivity of A higher thermal stability of the trans-decalin compared to cis-
THQ, it is possible that hydrogen atoms may have capped the decalin was apparent based on the concentration change for Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1999/78590/V002T02A008/4218087/v002t02a008-99-gt-056.pdf by guest on 27 September 2021 alkyl peroxy radicals (formed by the fuel alkyl radicals and each of the isomers in the stressed sample. The higher molecular oxygen) inhibiting the thermal stabilizing reactions of concentration change of cis-decalin may imply that the '1+100" antioxidant compound. Also, as proposed by effectiveness of decalin as a pyrolytic suppressor could be Coleman and colleagues (Coleman et al., 1998), reactions of attributed more to the cis-isomer since it was more active. THQ radicals with molecular oxygen to form alkyl peroxy However, the higher molecular stability of the trans-isomer may radicals, and consequently hydroperoxides and oxy radicals, be needed to provide the thermal stability required at these high may undergo a variety of reactions to yield oxidation products temperatures. These results concur with recent studies of (autoxidative deposits). It is noteworthy that the amounts of stressed cis- and trans-decalin mixtures in static reactors in autoxidative deposits in JP-8 and JP-8+100 with THQ are which reductions in cis-decalin concentrations, and higher comparable, thus, in the presence of THQ the autoxidative thermal stability of the trans-decalin isomer were observed (Yu benefits of the "100 additive package in JP-8+100 are and Eser, 1998). Their results also showed increases in trans- negated. decalin concentrations due to isomerization reactions. Since in the present effort the concentration of trans-decalin decreased Gaseous and Liouid Products in the stressed sample, it was impossible to determine if The liquid and gaseous products of the thermally cracked isomerization of cis- to trans-decalin actually occurred. fuel were analyzed to assess the degree of thermal Nevertheless, in order to determine the thermal stability decomposition of the fuel, and to attempt to correlate fuel characteristics of each isomer and how these affect fuel thermal thermal decomposition with the pyrolytic deposition produced. A decomposition and pyrolytic carbon formation in jet fuels, typical gas sample composition for the gaseous products of individual assessment of each compound in a flow reactor is thermally cracked JP-8+100 is shown in Table 1. The molar needed. composition of the gas was approximately 60% alkanes, 36% Liquid-to-gas conversion rates of 4.5 to 5.0% were alkenes and -4% hydrogen. It was observed that the observed for the baseline and fuel with additives These results composition of the gas was unaffected by the additive or the differ considerably with those for JP-8 in which significant conversion rate. These results agree with previous experiments reductions in conversion were observed for the fuels with the with JP-8 (Corporan and Minus, 1998). additives. It is noteworthy that the effects of the additives on pyrolytic deposition and conversion were more pronounced for Table 1 Typical Composition of Thermally Cracked JP-8 than for JP-8+100 (Corporan and Minus, 1998). However, JP4+100 Gaseous Product not surprisingly, the thermal oxidative deposition was considerably lower with JP-8+100. It appears that the thermal Component Mole Percent stability (BETZ) package in JP-8+100 affects the chemical kinetics behavior of JP-8 by generating a different radical pool Hydrogen 4.12 in the thermal oxidative and intermediate temperature regimes. Methane 21.04 The new species appear to subsequently alter the pyrolytic Ethylene 11.04 regime kinetics and the production of deposits. Differences in Ethane 18.37 pyrolytic deposition between deoxygenated (nitrogen sparged), and oxygen saturated jet fuels have been observed previously Propylene 15.8 (Edwards et al. 1994, 1995), supporting the hypothesis that Propane 14.46 oxidative reactions in the lower temperature regimes alter the Butene 8.17 fuel chemical kinetics, i.e. carbon deposition, in the pyrolytic regime. Butane 4.09 The reduction in C15 - C15 n-alkanes (based on GC area Pentene 1.26 counts) for the stressed fuels is shown in Fig. 4. A reduction in Pentane 0.94 the longer chain n-alkanes occurred as a result of cracking into Hexene 0.48 smaller aliphatic species and hydrogen. These larger alkane molecules tend to break down more readily to form radicals and Hexane 0.24 lighter compounds, which explains the observed increase in decomposition of the n-alkane species as the carbon number increased. Generally, the additives increased the thermal Visual inspection of the stressed liquid sample showed a decomposition of the fuel relative to the baseline sample as yellow color for the JP-8+100 and JP-8+100/decalin fuels, and evidenced by the larger reduction in the higher order n-alkanes. light red for the JP-8+100fTHQ in comparison with the clear Despite the observed increase in thermal decomposition of the color of the unstressed sample. Despite distinctions in physical fuel, the pyrolytic deposition decreased in most cases. Pyrolytic
5
60.0% NJP8+100 83 Decalin 0.5% ....,0 50.0% - (2) Decalin 1.0% _____ .. _
Bil Decalin 2.5% Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1999/78590/V002T02A008/4218087/v002t02a008-99-gt-056.pdf by guest on 27 September 2021 silTHO 1.0% irr. • . 40.0%- EITHQ 2.5% ._. _ .._ _ -- 1. friN I:: r .:. EAfh 4 ei ...... ;,,... j t
t iiii it"? ..11 ,...” .. :V ni, \ Hi% r;,S• i -E- MMeall 4 ii ,..z, • ...... „TA. N E iria fQii :::"; sol .i, ma/ ...-. is+,-, • .../ii-, _ LI, ::: '' \ ;:: 0 20.0% ::' -4. mn •"" En 54. \ :: W4 a est .1 En - 1: k9 1/4 11: Nr---' :, :. . d " -.". 44 './... na MO i.,, ,1/4 : ===...... MM.' C MI In. 4:-4 a: ... It.4 = sae 4,.., = Elm ... i21/ik... a ... „ _ ...... ,,,...:..„..=. ii. le = N.,., Itrys_no ,"e:.• ■ t., . .. 11-4 ea -.-j :: .(1. ra is: ;-.3 = ens 44,2 -= " •24, aml .2;\ CM 41 = IL K. = 1.• R.- V' tiVS1/4 ie. Va■ = ;I: :cr. Z''S5 ■ 7=- IL '....k e2- .14. = a me% :10k.,•B N— -• own •4i. a"- 21. 6-.,.....' -- " .11 ff• ::: Zji -M- :: 6.1* = • . t., .- 0 r - ::: .0 _= Fti. R. .. pi -=- is: c ff--, =_ •• ?.. = Ill Sij =•-.2. it s• : P.t-irlt. .,' n':: 1 ...MU rx, ::, d r = 11 r,.;,' =:-&-.. . . -..; ... ,.... a- 11:4:7? E.- ,.. 4 ?...a & .r.. o.oss ilia..S--- - ILIMP-4.&E" ::- Amts...N--- li: A • K‘B. n•C10 n-C11 n-C12 n-C13 n-C14 n•C15 Sp•ele
Fig. 4 Reduction of C10 -C15 n-alkanes relative to unstressed sample
deposits, however, may be more strongly influenced by the to the baseline fuel without any adverse effects on the thermal production of aromatic species in the thermal cracking process oxidative deposition. THQ produced moderate reductions in than by the degree of decomposition of the major components pyrolytic deposits; however, it increased the thermal oxidative in the fuel. The formation of benzene and polycyclic aromatic deposits by up to a factor of six at a 2.5 % w/w concentration. It hydrocarbons (PAHls) can occur via decomposition of aromatic was observed that the additives had negligible effects on liquid- and aliphatic species in the parent fuel, and through to-gas conversions and gas sample composition. subsequent molecular growth (Maurice et al., 1998). It is Analysis of the liquid sample shows that the additives generally accepted that the formation and growth of solids increased the thermal decomposition of the fuel as evidenced during pyrolytic degradation of jet fuels are widely linked to by the increased change in n-alitanes relative to baseline fuel. benzene and PAH formation (Song et al., 1992). Analysis of Surprisingly, this increase in decomposition was accompanied aromatic components in the stressed sample is shown in Fig. 5. by a reduction in pyrolytic deposition. These results imply that As shown, significant increases in benzene, and CI - C2 alkyl pyrolytic deposits may be more strongly influenced by the benzene species, and substantial reductions in Cg - Cg alkyl production of aromatic species in the thermal cracking process benzenes were observed relative to the unstressed sample. In rather than the degree of decomposition of the major addition, slight reductions in benzene and CI - C2 alkyl benzene components in the fuel. Liquid sample analyses show components were observed for the fuels with additives significant increases in benzene, and CI - C2 alkyl benzene compared to the stressed baseline fuel These results imply species, and substantial reductions in Cg - C6 alkyl benzenes that the hydrogen abstraction from hydrogen donor compounds relative to the unstressed sample. In addition, measurable may indeed inhibit cyclization reactions and subsequent reductions in benzene and Ci - C2 alkyl benzene components formation of solid particulate. It's noteworthy that the hydrogen were observed for the fuels with additives compared to the donors appear to have minimal effects in the chemical kinetics baseline stressed fuel. The reduction in benzene species of Cg - C6 alkyl benzenes since negligible changes were implies that hydrogen donor compounds may indeed inhibit observed between the fuels with and without additives. cyclization reactions that subsequently form solid particulate. This effort supports the Air Force Research Laboratory's SUMMARY AND CONCLUSIONS Fuels Branch (AFRLJPRSF) 'Controlled" Chemically Reacting The effectiveness of hydrogen donor compounds, decalin Fuels program which develops fundamental technologies for and 1,2,3,4 tetrahydroquinoline (THQ), as thermal stabilizers for fuels used in existing and future air and space vehicles. Future JP-8+100 was assessed. Results show that decalin at 1.0 % work will assess the performance of decalin at 1.0% whv w/w concentration, reduced pyrolytic deposits by 50% relative concentration in JP-8+100 in a large-scale reactor system at
6 0.45 OJP8+100 unstressed
0,4 • JP8+100 stressed III THO 2.5% 0.35 CS5THQ 1.0%
\'‘ Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1999/78590/V002T02A008/4218087/v002t02a008-99-gt-056.pdf by guest on 27 September 2021 €1Decalin 0.5% 0.3 ..p \ Decalin 1.0% • 0.25 ' a Decalin 2.5% '1
0.15 - \ 0.1 N_ \
\ r.47o c N \ 0.05 \ \*/ cf:/ c2.■ '%1 1111M \ QA, Banana Toluene C2 benzene C3 benzene C4 benzene C5 benzene CS banana compound
Fig. 5 Benzene species in stressed and unstressed liquid products higher residence times (10-20 seconds) and longer run periods Edwards, T., Liberia, P.: The Thermal-Oxidative Stability of (12-24 hrs). Bench scale testing will continue with the Fuels at 480°C (900°F), ACS Petroleum Chem. Div. Preprints, individual evaluation of cis- and trans-decalin isomers, and Vol. 39, No. 1, pp. 86-91, 1994. other hydrogen donor additives (e.g. decahydroquinoline, cyclodecane). Studies will be pursued in a system that focuses Ely, J.F., Huber, M.L.: NIST Standard Reference Database 4 — on the elemental chemistry of the fuel to increase the NIST Thermophysical Properties of Hydrocarbon Mixtures, understanding of the effects of hydrogen donor compounds on 1990. fuel decomposition • chemistry, and elucidate the pathways leading to pyrolytic deposition mitigation. Heneghan, S.F., Locklear, S.L., Geiger, D.L., Anderson, S.D. and Schulz, W.D.: Static Tests of Jet Fuel Thermal and ACKNOWLEDGMENTS Oxidative Stability, AIAA J. of Propulsion and Power, Vol. 9, No. This work was funded by the Air Force Office of Scientific 1, pp. 5-9, 1993. Research (AFOSR) and the Air Force Research Laboratory (AFRL). The authors gratefully acknowledge Dr. Lourdes Heneghan, S.P., Zabamick,S., Balla!, DR. Harrison III, W.E.: Maurice for her helpful discussions on fuel chemical kinetics. JP-8+100: The Development of High Thermal Stability Jet Fuel, AIM 96-0403, Reno, NV,1996. REFERENCES Coleman, M.M., Sobkowiak, M., Feamley, S.P., Song, C.: Maurice, L.Q., Edwards, T.J., Striebich, R.C.: Formation of Hydrogen Donors as High Temperature (>400°C) Stabilizers for Cyclic Compounds in the Fuel Systems of Hydrocarbon Fueled Jet Fuels-A Dilemma, ACS Petroleum Chem. Div. Preprints,Vol. High Speed Vehicles, AIM 98-3534, Cleveland, OH 1998. 43, No. 3, pp. 353-356, 1998. Maurice, L.Q., Edwards,T., Corporan, E., Minus, D., Mantz, R., Corporan, E., Minus, D.K.: Assessment of Radical Stabilizing Striebich, R.C., Sidhu, S., Graham J., Hitch, B., Wickham D., Additives For JP-8 Fuel, AIAA 98-3996, Cleveland, OH 1998. Karpuk M.: Controlled Chemically Reacting Fuels: a New Edwards, T., Atria, J.: Deposition from High Temperature Jet Beginning, XIV ISABE International Symposium on Airbreathing Fuels, ACS Petroleum Chem. Div. Preprints, Vol. 40, No. 4, pp. Engines. 1999, In publication. 649-654, 1995.
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Song, C., Peng, Y., Jiang, H., Schobert, H.H.: On the Mechanisms of PAH and Solid Formation During Thermal Degradation of Jet Fuels, ACS Petroleum Chemistry Division Preprints, Vol. 37(2), pp. 484-492, 1992.
Song, C.; Lai, W-C.; Schobert, H. H.; Hydrogen-Transferring
Pyrolysis of Long-Chain Manes and Thermal Stability Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1999/78590/V002T02A008/4218087/v002t02a008-99-gt-056.pdf by guest on 27 September 2021 Improvement of Jet Fuels by Hydrogen Donors. Ind. Eng. Chem. Res., 33(3), 548-557 1994.
Yoon, EM., Selvaraj, L., Song, C., Stallman, J.B., Coleman, MM.: High-Temperature Stabilizers for Jet Fuels and Similar Hydrocarbon Mixtures. 1. Comparative Studies of Hydrogen Donors, Energy & Fuels, Vol 10, pp. 806-811,1996.
Yu, J.; Eser, S.: Thermal Decomposition of Jet Fuel Model Compounds under Near-Critical and Supercritical Conditions. 2. Decalin and Tetralin, Ind. Eng. Chem. Res. 4603-4604, 37, 1998.