NASA Technical Memorandum 103177

AIAA-90-2319

Fuel-Rich Catalytic Combustion-A Fuel

Processor for High-Speed Propulsion

Theodore A. Brabbs

Sverdrup Technology, Inc.

Lewis Research Center Group

Brook Park, Ohio

and

R. James Rollbuhler and Erwin A. Lezberg

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio

Prepared for the

26th Joint Propulsion Conference

cosponsored by the AIAA, SAE, ASME, and ASEE

Orlando, Florida, July 16-18, 1990

FUEL-RICH CATALYTIC COMBUSTION - A FUEL PROCESSOR FOR HIGH-SPEED PROPULSION

Theodore A. Brabbs

Sverdrup Technology, Inc.

Lewis Research Center Group

Brook Park, Ohio 44142

and

R. _ames Rollbuhler and Erwin A. Lezberg

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135

I..O

t.O

!

INTRODUCTION

In a previous publication (ref. 1), results were presented for the fuelrich catalytic combustion of iso-octane (equivalence ratios of 4.0 to 8.0).

In addition to producing a very reactive and soot-free fuel with temperatures

up to 1200 K, the process was shown to upgrade the structure of the fuel by the

formation of hydrogen and smaller hydrocarbons. It also produced a cleaner

burning fuel by removing some of the fuel carbon from the soot formation chain.

With fuel-rich catalytic combustion as the first stage of a two-stage combustion system, these enhanced fuel properties can be utilized by both high

speed engines, where tine for ignition and complete combustion is limited, and

engines where emission of thermal NOx is critical. Two-stage combustion has

been shown to be effective for NOx reduction in stationary burners where residence times are long enough to burn up any soot formed in the first stage.

Such residence times are not available in aircraft engines. Thus, the sootfree nature of the present process is critical for high-speed engines. Hustal

and Sonju (ref. 2) studied the lower flammability limit of hydrocarbons as a

function of temperature and showed that the limit goes to zero at about 1473 K.

It is estimated that the maximum temperature for the gases produced from fuelrich catalytic combustion is probably 1350 K which is the threshold temperature

for the formation of soot (ref. 3). Thus, the high temperature produced by

this process enables one to use fuel-lean combustion in a second stage as a

technique for controlling the combustion temperature and the formation of thermal NOx .

Success of this concept will be highly dependent on the ability to apply

it to practical and co_nonly used aircraft fuels, such as Jet-A and Jp-4. This

paper will describe the successful application of fuel-rich catalytic combustion to Jet-A, a multicomponent fuel used in gas turbine combustors. The further objective of ongoing investigations will be to then apply the concept to a

staged combustor where approximately 6 to 8 percent of the engine airflow is

diverted to the catalyt:Lc combustion (fuel preparation) stage and then utilizing a high-speed mixing device to mix the partially reacted gaseous fuel with

the remainder of the cornbustion air. Since the temperature and residence time

of the process can be well controlled, it is expected that the second stage of

the combustion process _vill also be soot-free and produce a minimal amount of

thermal NOx.
The experimental results presented in this study were obtained from two

test facilities; I, a small bench scale flow tube reactor (fig. 1) which had

an airflow of about 23 kg/hr and II, a scaled up version (fig. 2) with an airflow rate of 900 to 1400 kg/hr.

TEST FACILITY I - EXPERIMENTAL APPARATUS AND PROCEDURES

The catalytic flow tube reactor has been described in reference 1 and the

present fuel injector in reference 4. The fuel used for this work is specified

by ASTM Jet-A turbine fuel designation. This is a multicomponent kerosene type

fuel commonly used in gas turbine engines. Jet-A with a H/C ratio of 1.92 has

an autoignition temperature of 533 K and contains 15 percent aromatic and

I percent olefin hydrocarbons. The fuel was metered to the reactor from a

pressurized fuel tank. Flow rates measured with a calibrated turbine flow

meter varied from 150 to 220 cm3/min, depending upon the equivalence ratio

desired.

Standard procedures were followed for each run. These included a warm-up

of at least 90 min with hot nitrogen followed by an additional warm-up of 30 to

50 min at the desired test conditions. This procedure assured steady-state

temperatures in the reactor.

After the reactor reached a steady-state temperature, start-up was initiated by adding fuel to the hot nitrogen. To ensure that the equivalence ratio

in the reactor was always beyond the rich limit of combustion, the flow system

was designed to permit switching the gas from nitrogen to air without interrupting the flow. By adjustment of the regulated pressure of the two gases,

the fuel-air equivalence ratio could be established with hot nitrogen and then

switched to air. In this way the catalyst never experienced stoichiometric

burning. Shutdown was accomplished by reversing the process. A calibrated

strain gauge flow meter measured the airflow which was kept constant at about

0.3 std m3/min. The pressure at the inlet to the catalyst bed was maintained

at about 160 kPa.

The catalyst used in these experiments was a 2:1 mixture by weight of

palladium/platinum applied to cordierite honeycomb substrates coated with alumina washcoat. Three catalyst configurations were used in the study.

Gas samples were drawn from the reactor from a probe located 17.8 cm downstream of the catalyst bed, corresponding to about 20 msec of gas phase reaction time. The sampling system and procedure has been previously described

(ref. 1). The gaseous combustion products were analyzed by gas chromatography

with thermal conductivity and flame ionization detectors. Three columns were

used for the separation of the gas components: (1) washed Molecular sieve,

(2) Spherocarb, and (3) Porapak R.

RESULTS

Jet-A fuel was studied over the equivalence ratio range 4.8 to 7.8

(F/A = 0.331 to 0.538) with combustion temperatures ranging from 1200 to 1060 K

(2160 to 1900 °R). Flashback and spontaneous ignition of the fuel were not a

problem for the test conditions used in the present study. In prior tests with
a different fuel injector, the fuel autoignited ahead of the catalyst and the

gases observed throug[ the windows 7.6 cm downstream of the catalyst were completely opaque indicating large amounts of soot. With a fuel injector designed

to better atomize the fuel, autoignition did not occur and the reaction products

were completely transparent. Thus the soot-free nature of the process was

demonstrated by the observation of a completely transparent reaction product.

The reaction temperature was measured 3.8 cm downstream of the catalyst

bed with a shielded closed-end thermocouple. Figure 3 is a plot of the measured reaction temperature versus equivalence ratio. These measured temperatures were compared with combustion temperatures calculated by assuming that

soot was or was not a product. The equilibrium calculations were performed

with the NASA Lewis Research Center equilibrium program (ref. 5), which contains thermodynamic data for about 140 C-H-O-N species. This large data base

was important because the no-soot calculated reaction temperatures depend not

only on the initial conditions of the reactants (equivalence ratio and temperature), but also on whi,3h species could be considered reaction products. The

temperatures predicted by the two calculations (soot/no-soot) differ by about

150 K, and as can be seen, the measured reactor centerline temperature agreed

well with the no-soot line. This is the same behavior observed in the study of

the catalytic combustion of iso-octane (fig. 3) and shows that the no-soot calculation is a good method for predicting the combustion temperature.

Table I shows a comparison of the reaction products, temperatures, and

equivalence ratios for one of the catalyst configurations used in this study.

The products are divided into two groups to show the fuel-processing character

of the preburner. Group 1 contains H2, 02, N2, and all C1 and C2 carbon containing compounds while group 2 contains the larger hydrocarbons. The analysis

shows that the breakdown of Jet-A is very similar to that found for iso-octane

with the exception of hydrogen and aromatics. The smaller hydrogen concentrations is probably due to the lower hydrogen-to-carbon ratio of the Jet-A fuel.

Although Jet-A had an initial aromatic content of about 15 percent, less than

1 percent benzene and toluene was measured in the reaction products.

The carbon-atom balance across the catalyst bed was calculated from the

measured reaction products. Changes in the number of moles of gas due to chemical reaction were accounted for by using nitrogen as a reference gas and balancing the carbon-nitrogen ratio across the catalyst bed. One molecule of

Jet-A was assumed to contain 12 carbon atoms. Figure 4 is a plot of the percentage of the initial fuel carbon found in the product gases as a function of

the equivalence ratio. Unlike the iso-octane study, we were unable to account

for all of the fuel carbon of Jet-A with the gaseous products, since some of

the fuel carbon was condensed in the ice bath cold trap along with the water.

Calculations show that the loss of as little as 0.5 percent of a C9 compound in

the cold trap would acc:)unt for the missing carbon. Three catalyst configurations were studied and they clearly show that excess catalyst does not improve

the carbon atom balance.

The fuel processing character of the process can be seen in figure 5,

where the fraction of the fuel carbon in C1, C2, and C3 molecules is plotted

as a function of the equivalence ratio. At an equivalence ratio of 4.6, about

80 percent of the fuel carbon is in C1, C2, and C3 molecules. Excess catalyst

has no effect on the amount of carbon in this group.
TESTFACILITY II

Preliminary data from the larger reactor will be used to determine the

catalyst loading requirements and the effect of higher inlet air temperatures.

Test conditions; changing mass flow rates, inlet combustion air temperatures,

and fuel-to-air equivalence ratio (E.R.), are run in a matrix test fashion.

The initial catalyst tested consisted of 15.2-cm diameter monolithic cell

ceramic disks which had been coated with a proprietary platinum base catalyst

material. The disks were 2.5 cm thick and four of them were closely stacked

together in series in the test unit. The first two disks had 100 equal size

cell passages per square inch of disk surface; the last two disks had 200 cells

per square inch.

The catalyst unit was tested by flowing a known mixture of hot air and

vaporized fuel through the catalyst disks until equilibrium temperature, pressure, and composition conditions were obtained. Generally this was after about

5 min of flow and the results reported herein are from the 4 to 5 min portion

of such testing.

Gas temperatures before and after the catalyst bed were measured with sets

of 12 circumferentially spaced thermocouples whose sensing tips were about 5 cm

from the gas flow centerline. The thermocouple arrays were 10 cm upstream and

downstream of the catalyst bed. At the lO-cm downstream location, a gas sampiing probe was used to continuously withdraw a sample for chemical composition

analysis.

Test results for 11 tests are presented in table II. Tests 1 to 5 were

conducted at identical airflow rates and input temperatures over a range of

(E.R.) from 4.7 to 7.0. The gas temperatures at the different measuring sites

as well as the gas composition, in terms of percent are presented as a function

of E.R. Nitric oxide concentrations were under 10 ppm over the entire E.R.

range. Tests numbered 6 to 8 had the same input air temperature as 1 to 5, but

25 and 50 percent greater mass flow rates, respectively.

The variation of measured combustion gas temperatures as a function of

changing equivalence ratios (E.R.) is presented in figure 6 along with the calculated lines (soot/no-soot). As can be seen the data are in agreement with

the no-soot line for E.R.'s below 5.0 but depart significantly as the fuel mass

flow (E.R.) is increased. This behavior suggests that the active surface area

in the catalyst bed is not large enough to realize complete combustion. Experiments are being conducted with catalyst beds two to three times larger than

that used in the present tests.

The constituents (hydrogen and carbon monoxide) in the combustion products

from both facilities are presented in figure 7. Although insufficient catalyst

surface area was indicated for the large reactor, the emission levels were relatively close in value to those measured with the small reactor. In addition

they show the same trend as a function of equivalence ratio. A comparison of

the measured combustion temperatures for the two rigs can be shown to be quite

similar, suggesting that these species concentration are strongly dependent

upon the reaction temperature rather than completeness of reaction. Additional

testing is required to verify this suggestion.
Although we have not been able to duplicate test results from the small

reactor, we have produced a high-temperature fuel containing large amounts of

hydrogen and carbon monoxide. The balance of the fuel is completely vaporized

and in various stages of pyrolysis and oxidation. Visual observations indicate

that there is no soot present. Additional experiments are required to clarify

the differences from the small reactor results.

SUMMARY OF RESULTS

Fuel-rich catalytic combustion of Jet-A fuel was studied over the equivalence ratio range 4.7 to 7.8, which yielded combustion temperatures of 1250 to

1060 K. The process was soot-free and the gaseous products were similar to

those obtained in the iso-octane study. A carbon atom balance across the catalyst bed calculated for the gaseous products accounted for about 70 to 90 percent of the fuel carbon; the balance was condensed as a liquid in the cold

trap. It was shown that 52 to 77 percent of the fuel carbon was C1, C2, and

C3 molecules. This study demonstrated the viability of using fuel-rich catalytic combustion as a technique for preheating a practical fuel to very high

temperatures.

Preliminary results from the scaled up version of the catalytic combustor

produced a high-temperature fuel containing large amounts of hydrogen and carbon monoxide. The balance of the fuel was completely vaporized and in various

stages of pyrolysis and oxidation. Visual observations indicate that there was

no soot present.

REFERENCES

1. Brabbs, T.A. and Olson, S.L., "Fuel-Rich Catalytic Combustion: A Soot

Free Technique for In Situ Hydrogen-Like Enrichment," NASA TP-2498, 1985.

2. Hustad, J.E. and Sonju, O.K., "Experimental Studies of Lower Flammability

Limits of Gases and Mixtures of Gases at Elevated Temperatures," Combustion

and Flame, Vol. 71, Mar. 1988, pp. 283-294.

3. Gomez, A., Littman, M.G., and Glassman, I., "Comparative Study of Soot Formation on the Centerline of Axisymmetric Laminar Diffusion Flames: Fuel

and Temperature Effects," Combustion and Flame, Vol. 70, Nov. 1987,

pp. 225-241.

4. Gracia-Salcedo, C._., Brabbs, T.A., and McBride, B.J., "Experimental Verification of the Thermodynamic Properties for a Jet-A Fuel," NASA TM-101475,

1988.

5. Gordon, S. and McBride, B.J., "Computer Program for Calculation of Complex

Chemical Equilibriam Compositions, Rocket Performance, Incident and

Reflected Shocks, _nd Chapman-Jouguet Detonations," NASA SP-273, 1976.
TABLE I. - GASEOUS REACTION PRODUCTS

Catalyst surface area - 2067 cm2

Reaction temperature, K 1228 1213 1202 1190 1166 1146 1124 1107 1083

Equivalence ratio 4.60 4.76 4.91 5.02 5.25 5.68 6,16 6.52 7.07

Fuel flow, g .iol/min 0.580 0.602 0.623 0.646 0.757 0.823 0.895 0.958 1.037

Airflow, g tool/mix 10.68 10.73 10.76 10.89 12.22 12.28 12.32 12.46 12.44

Residence time, msec 20.6 20.4 20.8 20.5 19.8 20,2 20.3 21.0 22.0

Pressure, kPa

Upstream 156.7 156.0 156.4 155.8 160.3 159.7 159.0 159.2 159.4

Downstream 156.4 155.8 156.2 155.7 159,7 159.3 158.8 159.2 158.5

&P across bed 0.3 0.2 0.2 O.l 0.6 0.4 0.2 0.0 0.9

Temperature, K

Preheated air 799 799 800 800 800 801 801 803 803

Fuel 302 302 301 301 304 303 303 302 301

Group I:

Hydrogen 7.70 7.23 6.83 6.26 5.58 4.76 3.92 3.43 2.83

Oxygen 0.89 0.91 0.96 0.99 1.05 1.03 1.13 1.22 1.40

Nitrogen 59.76 58.85 59.68 59.05 59.90 60.43 59.80 61.68 63.15

Carbon monoxide 16.84 16.47 15.94 15.74 15.02 13.89 12.39 11.96 10.94

Carbon dioxide 2.21 2.18 2.20 2.27 2.29 2.61 2.93 3.23 3.49

Methane 5.34 5,34 5.41 5.32 4.91 4.58 4.03 3.71 3.32

Acetylene 1.134 1.DO0 0.877 0,731 0.360 0.237 0,151 0,124 0,076

Ethylene 5.34 5.81 6.53 6.56 7.02 7.57 7.37 7.61 6.76

Ethane 0.09 0.13 0.16 0.21 0.38 0.47 0.55 0.64 0.59

Total Croup 1 99.30 97.92 98.59 97.13 96.51 95.58 92.27 93,60 92.56

Croup 2:

Propylene 0.17 0.25 0.32 0.47 1.23 1.77 2.23 2.44

C3 hydrocarbons 0.133 0.155 0.171 0.189 0.191 0.162 0.075 0.058

C4 hydrocarbons 0.17 0.21 0.25 0.32 0.74 1.14 1.45 1.59

C5 hydrocarbons 0.04 0.05 0.06 0.07 0.16 0.28 0.44 0.56

C6 hydrocarbons 0.002 0.003 0.003 O.O00 0.004 0.026 0.066 0.11

Benzene 0.48 0.47 0.53 0.50 0.43 0.42 0.38 0.34

Toluene 0.22 0.23 0.31 0.29 0.27 0.31 0.31 0.32

C7 hydrocarbons 0.000 0.000 0.000 O.OOO 0.000 0.005 0.015 0.027

Styrene 0.040 0.040 0.063 0.043 0.030 0.011 0.017 0.011

C8 hydrocarbons 0.021 0.023 0.033 0.025 0.038 0.029 0.056 0.061

Total Croup 2 1.28 1.43 1.74 1.91 3.09 4.15 5.04 5.52

Total Groups 1 and 2 100.58 99.35 100.33 99.04 99.60 99.73 97.31 99.12

TABLE II. - PRELIMINARY TEST RESULTS

[Platinum based catalyst test unit; Jet-A.]

Parameters

Equivalence ratio

Reaction temperature, K

COlllbus l lnbus | i 01| ili r

Flow tale, kgmlhr

Temperature, I(

C(_buslion produt:ts, vol. %

llydrogen

Ca rbon mouox i de

Carbon dioxide

Oxygen

Test number

l 2 3 4 5 6 7 7 9 10 11

4.7 4.9 5.7 6.7 7.0 4.4 5.2 5.8 4,5 4.9 5.2

1248 1194 1137 1074 1044 1239 1134 1074 1181 1112 1047

949 989 969 966 994 1175 1137 1169 1369 1378 1358

947 943 946 944 945 936 937 939 909 908 910

8.2 7.0 5.7

13.9 13.4 11.2

2.5 3.1 3.4

0.8 0.8 1.2

3.6 2.8 8.3 6.1 4.4 7.0 3.5 2.3

8.8 8.0 11.9 12.7 10.7 13.1 9.1 6.3

4.0 4.2 3.8 4.4 5.2 4.1 3.6 3.2

2.3 3.1 ................... 2.4 4.3

6
FUEL rFUEL

(298 K)7 I INJECTOR CATALYST7

HOT AIR I T/C-_ _ rT/C

I i I

(800 K) / J I

--+r----1 --" ' I

VELOCITY = 4 t_'s [

F GAS

_SAMPLE

I

_ I.D. = 5 CM

SI

LOBSERVATION

WINDOW

FIGURE I. - SMALl BENCH SCALE APPARATUS (TEST FACILTIY I) WITH AN AIR MASS FLOW OF 23 Kg/HR.

800 - 10'.50K

CCW'iBUSTION AIR

900 - 11400KglIR

._ _ATOMINZ ING AIR

_-- _'\VI .,-FUELVAPORIZATION SECTION

/\ _i /.(,_'_,_w_"/ / GAS VELOCITY APPROXIMATELY 10 - 20 METER/SEC

_A,':..:._|_.c:,c'L_--.-.r_,' .,-CATALYST TEST PIECES

"_1 .i_._) /_. / 25 Mm4THICK MONDLITHDISCS

_ _"//P'_ -.-GASS.L,_PRO_

IEST FUEL HOT GAS

_'_A_J_._-._ _ .'.._ \'_.\'_n_.-,."'r" TEMPERATURE

20.3 CM /_ /__'_l_1_"_,_'_le_\.\_:'_Y_JJREADOUT

STEEL PIPE-" l,_u..}O_ ," I] "_J_IJ

TELEVISION _tC/ t _ll "

CAI4ERA _ HOT EXHAUST GASES

FIGURE 2. LARGE TEST FACILITY IT WITH AIR MASS FLOWRATES OF 900 - 1400 KO/HR,
1250

1200

1150

1100

1050

1000

95O

2

1200

11511

1100

11)51)

95O

-- _, CSA = 1978 CM2

^ _ CALCULATED- NO SOOT

""

I I I I I

(a) I SO-OCTA_.

_.. 0 CSA = 2067 cJ,t2

___ {7 CSA = 2q79 c._2

_ _ CALCULATED- NO SOOT

'-' CALCULATED- SOOT

"_',,

I I I I I

5 6 7 8 9

EQUIVALENCE RATIO

(b) JET-A.

FIGURE 3. - CORPARISON OF RE.ASUREDREACTION _RATURES WITH CALCULATED EQUILIBRIUR TEMPERATURES

(WITH AND WITHOUT SOOT) FOR ISO-OCTANE AND JET-A.

i

|

1oo

80

6o

qO

20 --

o

q.5

CSA,

CM2

0 2067

1-1 2q79

3028

1 I I I I I

S.O 5.5 G.O 6.5 7.0 7.5

EQUIVALENCE RATIO

FIGURE q. - PERCENT OF FUEL CARBON FOUND IN GASEOUS

SAMPLES AS A FUNCTION OF EQUIVALENCE RATIO.
=

L.J _J

_-E

z

i;,,=,

Cu

100 --

80

60

40

20 m

m

CSA,

CM2

0 2O67

6"1 2q79

3028

o I I I I I I

q.5 5.0 5.5 G.O 6.5 7.0 7,5

EQUIVALENCE _ATIO

FIGURE 5. - PERCENT OF FUEL CAI;BON FOUND IN C I, C2 AND

C 3 COMPOUNDS AS A FUNCTION Of EQUIVALENCE RATIO.

1300

1250

1200

i 1150

1100

@.

IO_O

1000

950

9OO

CALCULAT IONS

-- NO SOOT

SOOT

I I I i

5 6 7 8

EQUIVALENCE RATIO

FIGURE 6. - COf_PARISON OF MEASURED REACTION TEMPERATURES WITH CALCULATED EOUILIBRIUM TEMPERATURES AS

A FUNCTION OF EQUIVALENCE RATIO IN TEST FACILITY If.

20

18

16

14

_ 12

N lO

_ 8

o_ 6

O• HYDROGEN

011 CARBON MONOXIDE

2--

o f I I I I 1 I I

4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0

EQUIVALENCE RATIO

FIGURE 7. - COMPARISON OF THE EMISSIONS (HYDROGEN AND

CARBON MONOXIDE) FOR THE TWO TEST FACILITIES. OPEN

SYMBOLS ARE FOR TEST FACILITY I AND CLOSED ONES ARE

FOR TEST FACILITY II.

9
Report Documentation Page Nalional Aeronautics and

Space AdmJnistrahon

1. Report No. NASA TM-103177 2. Government Accession No. 3. Recipient's Catalog No.

A[AA-90-2 319

4. Title and Subtitle 5. Report Date

Fuel-Rich Catalytic Combustion--A Fuel Processor for High-Speed Propulsion

7. Author(s)

Theodore A. Brabbs, R. James Rollbuhler, and Erwin A. Lezberg

6. Performing Organization Code

8. Performing Organization Report No.

E-5555

9. Performing Organization Name and Address

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135-3191

12. Sponsoring Agency Name and Address

National Aeronautics and Space Administration

Washington, D.C. 20546-0001

10. Work Unit No.

505-62-3 l

11. Contract or Grant No.

13. Type of Report and Period Covered

Technical Memorandum

t4. Sponsoring Agency Code

15. Supplementary Notes

Prepared for the 26th Joint Propulsion Conference cosponsored by the AIAA, SAE, ASME, and ASEE, Orlando,

Florida, July 16-18, 1990. Theodore A. Brabbs, Sverdrup Technology, Inc., Lewis Research Center Group,

2001 Aerospace Parkway, Brook Park, Ohio 44142.

16. Abstract

Fuel-rich catalytic combustion of Jet-A fuel was studied over the equivalence ratio range 4.7 to 7.8, which

yielded combustion temperatures of 1250 to 1060 K. The process was soot-free and the gaseous products were

similar to those obtained in the iso-octane study. A carbon atom balance across the catalyst bed calculated for the

gaseous products accounted for about 70 to 90 percent of the fuel carbon; the balance was condensed as a liquid

in the cold trap. It was shown that 52 to 77 percent of the fuel carbon was Ct, C2, and C 3 molecules. This study

demonstrated the viability of using fuel-rich catalytic combustion as a technique for preheating a practical fuel to

very high temperatures. Preliminary results from the scaled up version of the catalytic combustor produced a

high-temperature fuel containing large amounts of hydrogen and carbon monoxide. The balance of the fuel was

completely vaporized and in various stages of pyrolysis and oxidation. Visual observations indicate that there was

no soot present.

17. Key Words (Suggested by Author(s))

Catalytic combustion; Jet-A fuels; Fuel-rich

combustion; Soot-free combustion; NOx

reduction; High-temperature fuel

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Unclassified - Unlimited

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