NASA Technical Memorandum 104423AIAA - 91- 2463

Fuel-Rich, Catalytic ReactionExperimental Results

R. James RollbuhlerLewis Research CenterCleveland, Ohio

Prepared for the27th Joint Propulsion Conferencecosponsored by the AIAA, SAE, ASME, and ASEESacramento, California, June 24-27, 1991

NASA

https://ntrs.nasa.gov/search.jsp?R=19910014890 2020-03-13T00:30:06+00:00Z

FUEL-RICH, CATALYTIC REACTION EXPERIMENTAL RESULTS

Jim RollbuhlerNational Aeronautics and Space Administration

Lewis Research CenterCleveland, Ohio 44135

SUMMARY

An experimental investigation has been conducted involving the partialoxidation reaction of a fuel-rich gaseous mixture of fuel and air in a cata-lyst containing reactor. The fuel used was Jet-A and it was vaporized in ahot air stream before being introduced into the catalytic reactor. There waslimited air in the mixture, the fuel to air equivalence ratio was 3.5 to 7.5,so that only a partial breakdown and oxidation reaction of the fuel couldoccur. The reactor discharge gases were at a maximum temperature of about1375 K and contained high concentrations of hydrogen (5 to 10 vol %), carbonmonoxide (10 to 15 vol %), and light and heavy end hydrocarbons. The nitrogenoxide concentration was very low, possibly because of hydrogen reduction.Various ceramic catalyst mounting techniques were developed to maintainphysical integrity of the monolith pieces over the sequence of test cycles.

INTRODUCTION

A key issue in the development of the next generation high-speed civiltransport is environmental acceptability. Of particular concern is that thenitrogen oxide (NO x ) emissions, from the aircraft gas turbine engines oper-ating at high altitudes do not have detrimental effects on the Earth shieldingstratospheric ozone layer. This concern has led to significant developmentefforts in atmospheric modeling, combustion analysis, and testing of variouscombustor concepts that favor low NO combustion.

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A concept of interest is staged combustion. A simplified explanation ofthis is to have two distinct reaction regions in a combustor, one to initiatea fuel-air reaction and a second to complete the combustion process. The goalis to achieve the overall process with only minimum reaction occurring atstoichiometric conditions where the maximum concentration of NO would bexformed. This is shown in figure 1, which is a generalized plot of reactiontemperature and NO x concentration as a function of the fuel to air or equiv-alence ratio (ER). Ideally, the fuel and input air begin reacting in afuel-rich concentration, i.e., to the right of the fuel-air stoichiometricconcentration point in figure 1. Because of insufficient combustion air atthe fuel-rich ER, the vaporized fuel will only partially react. The partiallyoxidized fuel-air mixture is then quickly mixed with additional air such thata fuel-lean concentration condition results, at which condition the combustionof the fuel is carried to completion. The key factor is quick and completemixing of the partially reacted fuel-air mixture with more air so that thereis not enough dwell time for stoichiometric combustion to occur.

The program described in this report concerns the first stage reactionmechanisms required to vaporize and partially react a liquid hydrocarbon fuel(i.e., Jet-A) with hot incoming combustion air. The technique used to bringabout the partial reaction was exposure of the fuel-air mix to a catalyst.The catalyst will initiate a controlled reaction at low threshold temperatures

and in theory it has an unlimited life. Previous work involving partialoxidation using catalysts here at NASA Lewis Research Center is reported inreference 1.

This program tested a number of different catalyst types and materialconfigurations. This report details efforts using ceramic, monolith, sub-strate material that has been commercially coated with platinum or palladiumactive compounds. Steady-state testing was done with these catalysts over arange of combustion air flows, incoming air temperatures, and fuel to airratios (ER); all in a flame tube type test reactor. Detailed diagnostic meas-urements were made of the overall catalyst reactor performance, including theproduct discharge gas composition and changing gas temperatures.

In the near future the results of this program will be incorporated intoa two stage combustor to be tested here at NASA Lewis.

TEST FACILITY

This program was carried out in the combustion research laboratory, cell23, at NASA Lewis. A schematic of the test facility is shown in figure 2.

In order to simulate compressor or ram combustion air coming into acombustor at high temperatures, the rig input air was passed through acounter-flow, high temperature heat exchanger. The exchanger was designed toheat up to 1.0 kg/sec of air to a maximum temperature of 1250 K. This isaccomplished with a single pass of the air through a slowly rotating, porousceramic wheel. As the wheel rotates, it passes through a burner exhaust gasstream in an adjoining chamber separated from the air flow passage chamber bygas seals on the rotating wheel surfaces. The portion of the wheel heated inthe exhaust gas stream proceeds to rotate into the air passage chamber wherethe flow-through air removes the wheel heat as the wheel again enters the hotexhaust gas chamber. By varying the hot exhaust gas temperature and/or thewheel rotation speed, different air flow rates can be heated to differenttemperatures.

The rig test section is immediately downstream of the heat exchanger hotcombustor air outlet. The liquid test fuel is injected into the hot airstream using a fuel-air multi-orifice atomizing injector unit. The introducedfuel was at ambient temperature and its flowrate was determined by the fuelpump output pressure selected.

The fuel-air mixture then flowed through theand was then cooled and discharged from the systemonly interested in investigating the first-stage,the product gases were vented to the atmosphere.high concentrations of hydrocarbons, hydrogen, andcompletely combusted in a flare burner at the endthe atmosphere downwind of the discharge stack didlevel of pollution.

instrumented test reactor. Since this program wasfuel-rich reaction process,Because the gases containedcarbon monoxide they wereof the vent stack. Tests ofnot indicate any measurable

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TEST SECTION

The test section used in this program consist of a number of internallyinsulated stainless steel pipe sections bolted together in series. Easybuildup and teardown of the pieces simplified the installation of catalystpieces and post-test inspection of the internal components. The test sectionis shown schematically in figure 3.

The hot combustion air, flowing out of the facility heat exchanger,enters the test section at the upper left in figure 3. The air then flowsthrough a 19 port, air blast, nozzle unit where the liquid hydrocarbon testfuel is introduced. The air flowrate has been set at a value between 0.2 and0.5 kg/sec and is at a temperature of approximately 820, 930, or 1050 K. Thefuel is sprayed through 1 mm orifices, one at each of the 19 ports in thenozzle unit. The fuel flowrate is varied in discrete quantities between 0.03and 0.30 kg/sec to obtain the desired test fuel to air ratio. Each of thefuel injection orifices is surrounded by a space through which cooling air isinjected to prevent the fuel from carbonizing in the orifice passages. Thisis a concern because the entire nozzle unit is being heated by the combustionair flow up to 1050 K. The cooling air flow is about 25 g/sec and this quan-tity is included in the overall air mass being used to calculate the ER. Thefuel may enter the nozzle unit as a liquid but at injection into the hot air,its state is a function of the heat transfer from the hot air to the nozzlemass to the fuel stream. The fuel pressure drop is monitored as a function offlow rate to determine if passage blockage is occurring and during thisprogram this did not occur.

After the fuel and air mix in the nozzle unit, there is a residencevolume about three pipe diameters long before the gas mixture enters thecatalytic reactor section. In this residence volume the fuel droplets have achance to absorb heat from the air and vaporize. The residence or dwell timein the vaporization section is 12 to 19 msec depending on the mass flowrate.By measuring the temperature drop of the fuel-air mixture in this volume, itis possible to determine the extent of fuel vaporization and subsequentheatup. The temperatures are measured at several locations in this residencevolume using shielded thermocouple rakes.

The catalyst reaction portion of the test section can accommodate up toabout 25 cm of 15 cm diameter catalyst material. The material has been in theform of monolithic ceramic or metallic discs which are between 25 and 75 mm inthickness. The discs look like honeycomb material with from 4 to 100 axialflow-through passages per square centimeter of disc face surface. When thereaction section was made with discs with space between them, thermocoupleswere inserted into the void gas space.

After the reactor section, about two pipe diameters further downstream,is a cross-sectional area containing 12 thermocouples and a gas samplingprobe. The thermocouples are equally spaced around the circumference fordetermining the reactor product gas temperature pattern.

Downstream of the thermocouple/gas sample probe area, are two observationwindows on either side of the exhaust gas duct. A video camera televises thegas flow and a digital temperature meter visible through the opposite window.The temperature reading is that of the gases flowing by the windows. The viewgives an indication of any burning carbon particles in the gas stream.

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Further downstream is a flow restriction that is used to maintain adesired back pressure in the test section. The reactor pressure is 125 to175 kPa depending on the gas mass flowrate. The gas pressure drop throughthe reactor is between 4 and 8 percent. The gases after flowing through therestriction are essentially at ambient pressure. At this point water spray isused to reduce the exhaust stream gas temperature before the flow is vented.

TEST CATALYSTS

The catalysts tested were obtained from commercial sources in the form of15 cm diameter monolithic discs. Specified were the disc thickness, discdiameter, number of flow-through passages per square centimeter of disc sur-face, but not the catalyst formulation or technique of application to theceramic surfaces. These latter details are usually proprietary to each ven-dor. The catalyst pieces reported on in this paper were obtained from theAllied-Signal Company, Industrial Catalyst Division.

Previous testing had resulted in success in using reactor disc piecesmade from nickel foil. The foil had been crimped and then rolled into a discshape such that gases would flow between the crimps and adjacent wrappedaround layers. One such disc was used in conjunction with some of the ceramicdiscs - either upstream or downstream of the ceramic pieces.

Six configurations were tested and are shown in a schematic axial cross-sectional view in figure 4. Configurations 3 and 5 used platinum based cata-lyst applied to the ceramic surfaces; the other configurations had palladiumbased catalyst on the surfaces. The nickel foil disc was installed 1.2 cmafter the ceramic pieces for configurations 3 and 15 cm before the ceramicpieces in configuration 5. Configurations 4 and 6 were tested with only cer-amic pieces. Configuration 4 had 2.5 cm spaces or voids between the piecesand configuration 6 had the pieces pressed together. Configurations 12 and 14made use of discs twice as thick as the previously used pieces. In additionconfiguration 12 had a nickel foil disc 5.5 cm downstream of the ceramic.Configuration 14 consisted of three double thick pieces made of a foamedceramic material.

Initially the catalyst discs were sized to slide into the reactor sectionwith a tight fit. Metallic clamping rings were installed upstream and down-stream to make sure the pieces did not move. After suffering physical deg-radation of the ceramic pieces using this technique, a better method waseventually determined for cushioning the pieces from the reactor wall and fromeach other. This made use of high temperature ceramic cloth tape and roping.An example of this latter mounting technique is shown in figure 5. The tapehas been wrapped around each disc outer edge several times to fill any voidspace between the disc and the reactor wall. The ceramic roping is placed ina single wrap on the outer edge to insure the ceramic pieces do not touch eachother when pressed into the reactor.

TEST INSTRUMENTATION

Gas temperatures and pressures were measured before and after the fuel-air mixing nozzle; before, in, and after the catalyst reactor; and in thedownstream exhaust and vent system. These temperatures and pressures, along

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with calculated fuel and air flowrates, are visually displayed in the testfacility control room and are recorded for later computational determinationof the desired result parameters.

A video display is presented in the control room showing the test riginternal reactor discharge gas flow stream. This display is recorded. A cellexterior video camera is used for overall scanning of the test facilityincluding the exhaust gas burnoff flare.

During testing the reactor product gases are continuously sampled. Inthis program, the sample gases being the result of a fuel-rich reaction, havecharacteristics completely different from those obtained from a more conven-tional lean burn combustion reaction. Lean-burn product gases usually havehigh carbon dioxide and water contents whereas rich-burn products are high incarbon monoxide and hydrogen. This meant a different set of gas analyzerswere required for the fuel-rich testing. These consisted of high concentra-tion measuring nondispersive infrared carbon monoxide and hydrocarbon analyz-ers, a low concentration nondispersive infrared carbon dioxide analyzer, a lowrange chemiluminescent nitrogen oxides analyzer, a low range electrochemicaloxygen measuring analyzer, and a thermal conductivity hydrogen analyzer. Eachanalyzer was zeroed and calibrated with known concentration span gases eachtest day.

A problem with sampling fuel-rich reaction gases is that any hydrogenand/or carbon monoxide in the gases tend to reduce nitrogen oxides, in thesame sample, to nitrogen and water (ref. 2). This is especially likely tohappen with hot gases (>450 K) in contact with stainless steel, nickel, orcopper (ref. 3).

The average gas temperature was under 1375 K and this was achieved bycontrolling the fuel to air ratio. This was done to safeguard the catalystmaterial from spalling, sintering, or oxidizing. With this low temperatureproduct gas it was possible to sample through uncooled probes made of varioushigh temperature materials. The sample gas coming through the probe wasquick-quenched immediately and passed through a gas cooler to bring itstemperature down to 280 K. At that temperature not only were any reactionsquenched but any unreacted hydrocarbons and water were condensed. In thisprogram the condensibles were not analyzed, but in previous work (ref. 4) theywere determined to be hydrocarbons of the C6+ groupings and amounted to lessthan 10 percent of the gas stream.

The program test results were obtained from testing six catalyst configu-rations over a matrix test pattern consisting of mass flowrate, input airtemperature, and the fuel to air ratio (ER). Test input conditions andsteady-state operating results are presented in Table 1 for each of the sixconfigurations. For comparison purposes, only those tests conducted at aninput air temperature of approximately 920 K are presented; in addition, testswere carried out using 810 and 1050 K input air.

_The tests were conducted at steady-state input conditions for 4 to 10 mindurations. Usually a minimum of 4 min was needed to get stable gas analysisresults. Typical test data are presented in figure 6. For a series of testsusing the configuration 3 reactor, the gas temperatures, averages values for aparticular location at a given time, and the gas sample analysis, for hydro-gen, carbon monoxide, carbon dioxide, and light-end hydrocarbons, for the four

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tests shown are presented as functions of operating time. Not shown is thetime between individual tests. The input air flowrate was about 0.32 kg/secand 930 K for all four tests; the fuel to air ratio was varied from one testto the next: 4.3, 4.7, 5.1, and 5.6 ER.

Figure 6 shows that as the ER increased, the precatalyst gas averagetemperature dropped with increased fuel flow. Likewise the gas temperaturesbetween the catalyst discs also decreased. Temperature 1 is the gas tempera-ture between disc 1 and 2, temperature 2 is the gas temperature between disk 2and 3, etc. The gas temperature downstream of the reactor, the average of 12thermocouple valves, is labeled "AC" and is generally lower than temperature 4which is immediately after the fourth and final catalyst piece. This drop intemperature can be attributed to thermal energy loss to the test sectionwalls.

As the ER was increased, the figure 6 hydrogen and carbon monoxide dataindicates decreasing concentrations. The hydrocarbons (reported as methane)and carbon dioxide tended to increase. Least stable in response were theoxygen and NO x data which were very low and had low response on the instru-ments being used.

Results: Thermal Performance

The chief objective of this first stage combustion process was to producea combustible gaseous product that can be easily mixed with sufficient combus-tion air to bring about complete combustion at a fuel lean second stage con-dition. If there is enough residence or dwell time in the first stage setup,the liquid fuel can be vaporized with the incoming hot air, but at the expenseof a temperature drop due to the vaporization process. The goal of this pro-gram was to not only vaporize the fuel and completely mix it with input airbut to also bring about some degree of reaction so as to recover some of thethermal energy lost during vaporization. Hopefully, this can be accomplishedby passing the vaporized fuel and air through a catalyst reactor.

The increase in thermal energy, in terms of the reactor discharge gastemperature rise over the input air temperature, is presented in figure 7.The rise is an average temperature for each of the six tested configurationsas a function of the test ER. Test conditions were at a nominal fuel-air massflow of 0.3 to 0.6 kg/sec and 920 K input air temperature. The temperaturespread for a given configuration at a given ER, was about ±25 K. Testing wasdone over a range of ER's limited to maximum outlet gas temperatures of 1375 Kor minimum stable operation.

Figure 7 results indicate that the platinum based catalyst material, plusa nickel disc, had the highest overall temperature gain between the input andoutput gas temperatures over the tested ER. Many of the palladium based cata-lyst configurations had a positive gain in temperature only at the lower ER'stested; at high ER's the gases never recovered back to the input air tempera-ture after going through fuel vaporization. There was some gas temperaturerise in going through the reactor but not enough to overcome the mass tempera-ture drop in vaporizing the liquid fuel.

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The drop in the fuel and air mixture temperature during the fuel vapor-ization phase is presented in figure 8 as a function of the ER. The tem-perature drop increases as the quantity of fuel in the mix increases. Forconfigurations 3, 4, 5, and 6, and the same operating conditions, the drop wasabout the same at a given ER; the variation being about ±10 percent. However,configurations 12 and 14 had vaporization temperature drops much greater thanconfigurations that utilized catalyst discs only half as thick. Conjecture isthat in using the thicker discs there is less heat transfer from the down-stream reaction region to the upstream disc face where input fuel and air cancome in contact with the catalyst surface. Also with the thicker discs thereis a greater pressure drop and more reason for the upstream gases to be stag-nant before flowing through the catalyst piece passages. The thinner discs,with less flow resistance, have increased turbulence in the flow passages andin the voids before and after each disc. This would encourage heat transferand reaction occurring closer to the upstream catalyst face.

The overall temperature rise shown in figure 7 includes increases in themass gas temperatures while flowing through the catalyst ceramic material,plus, in the case of configurtations 3, 5, and 14, through the nickel discpieces. The mass temperature rise through only the catalyst ceramic portionof each configuration is shown in figure 9 as a function of the ER. Theplatinum based catalyst (configuration 3) and the palladium based catalyst(configuration 4) appear to have about the same temperature rises between anER of 4 and 6.

The configuration mounting technique appears to have an influence on masstemperature rise. Configurations 3, 4 and 14 were mounted with spacingbetween the individual ceramic discs, whereas configurations 5, 6, and 12 hadthe ceramic discs as close together as possible. The spacing between thediscs apparently allows the gases exiting one disc to intermix and homoge-nously, and uniformly, react together before flowing into the passages of thenext downstream disc. On the other hand, those discs packed tightly togethertend to direct the mass flow through an almost continuous ceramic passagewhere most of the reaction can only be heterogeneous on the catalyst surfaces.

The loading factor, i.e., the optimum mass flowrate per active catalystsurface area, was highest with configuration 4 where it ranged from 0.03 to0.05 g/sec/cmZ . It appears, as shown in figure 9, that the greatest reactionactivity was at a mass flowrate of about 450 g/sec and flowrates greater orsmaller than this resulted in lower overall temperature rises.

The temperature pattern of the reaction gases flowing out of the reactoralso revealed a trend that was influenced by the type of catalyst beingtested. The temperatures of the reactor discharge gases from the six testconfigurations are presented in figure 10 for tests conducted at similarconditions. These are circumferential gas temperatures measured at steady-state operating conditions. The average value of each set is presented alongwith the high and low variations among the given set. With the platinumcontaining catalyst the variation was +15 and -14 K for configuration 3 and+54 -and -32 K for configuration 5. For the palladium containing catalystconfigurations the gas temperature variations were as high as +419 and as lowas -460 K (configuration 6); the biggest variations being for configurationswith the catalyst discs stacked close together.

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Another interesting temperature was that measured in the gas stream justbefore the pressure restriction; this was about 10 pipe diameters downstreamof the catalyst reactor. For most of the tests the gas temperature leveledout at about 1250 to 1350 K, even for those tests where the reactor dischargegas temperatures were about 1000 K. This would indicate that homogeneous gasreactions were occurring in the flow stream volume after the reactor.

Therefore, the importance of the catalytic reactor is initiating a heter-ogeneous reaction which, given additional residence time downstream of thereactor, will result in continuing homogeneous reactions before additional airis mixed into the mass for subsequently second stage combustion. The problemwith reactor configurations having wide variations in exit gas temperature isthat some portions of the mass flow are going through the reactor without evenundergoing any heterogeneous reaction and other portions are over-reacting inthe catalyst and bringing about over temperature catalyst destruction (e.g.,configurations 12 and 14).

Results: Emission Characteristics

The gas sampling for emission determination is done using a center linegas stream probe to remove about 5 L/min of reaction gas continuously duringany test sequence. After sampling the gas sample is cooled to ambient temper-ature to remove the heavy-end hydrocarbon products and the remaining gas issubdivided into portions passed through the individual component gasanalyzers.

The nitrogen oxides (NO x ) in the reactor discharge gas stream are pre-sented in figure 11 for the tested catalyst configurations. They arepresented as a function of the gas stream average temperature which is afunction of the operating ER. There is much scatter in the data because ofthe low values being at the minimum measuring capabilities of the analyzer.The general trend appears to be a maximum NO

x concentration of 14 ppm which

corresponds to an emission index value of about 0.08 g/kg fuel consumed.There appears to be a trend for the NOx concentration to peak at an operatingtemperature of 1100 to 1200 K, especially at the higher mass flowrates. Thismight be indicative of a reduction of NO at higher temperatures where thereis a greater concentration of hydrogen and carbon monoxide to react with theNO

x . As the reaction temperature decreases, so does the hydrogen and carbonmonoxide concentrations allowing more of the NOx to proceed downstreamunreacted. At temperatures of less than 1100 K there is less tendency for theair stream nitrogen to be oxidized to NO .

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The concentration of the gas stream carbon monoxide (CO) is presented infigure 12 for the various configurations, again as a function of the reactiongas temperatures. There is scatter in the data, but if only the configura-tion 3 data is examined, the CO concentration increases from about 5 vol % at1200 K to about 8 vol % at a 1400 K gas stream temperature. These measuredconcentrations are much lower than theoretical calculations (22 to 26 vol %)for Jet-A and air reacting at these indicated operating conditions. TedBrabbs in doing similar testing in a lab bench rig (ref. 4) obtained CO con-centrations about twice that shown in figure 12.

The concentration of hydrogen (H z ) in the reactor product gases is pre-sented for the tested configurations in figure 13 as a function of the gas

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stream temperature. Most of the data values are for configurations 3 and 5.As the gas temperature increased from 1100 to 1400 K, the configuration 5 HZ

concentration went from about 5 to 10 vol %; for configuration 3 the HZ

concentration went from 3 to 9 vol %. Both configurations had essentially thesame ceramic catalysts but 3 had the nickel disc downstream of the ceramicpieces and 5 had the nickel disc upstream of the ceramic pieces. It ispossible that configuration 3 product H Z is being used to reduce the oxidecoating on the nickel disc surfaces. To check this, nickel discs alone weretested at similar operating conditions and the results, shown in figure 13,show a marked reduction of H z production for similar operating conditions.

Results: Catalyst Physical Degradation

A problem using the ceramic disc catalysts has been the physical integ-rity of the monolithic material. Initial problems had to do with disc crack-ing with thermal cycling operation. This is illustrated in figure 14 wherefour 25-mm thick ceramic monolith discs are shown in their original receivedstate and then at the conclusion of their test program. Each of the discs hascracked into various size segments and only the compactness of the configura-tion kept the discs together through the testing sequence. Sudden cooling-down of the reactor at the conclusion of a given test day also contributed tothe high stress factors that would crack the monolithic structure. Afterseveral trial and error approaches, it was found that cushioning the discswith high temperature ceramic cloth tape and rope relieved this problem as isshown in figure 5.

Another problem, evident with the thicker discs, was localized hot spotsor over-temperature regions inside or on the end surfaces of the catalystdisc. These hot spots have high enough temperatures to melt and/or vaporizethe ceramic substrate. This is exemplified by a photograph, figure 15, ofconfiguration 14 foamed ceramic test discs. The photograph shows the down-stream end of each disc. The discs were about 2 cm apart in the test rig.The second disc had a localized hot region that destroyed or melted a portionof the ceramic foam. The melted ceramic and catalyst deposited on theupstream face of the third disc. With partial flow blockage in the thirddisc, it had hot spots which resulted in end melting. What with deposits andvoids in the discs the gas flow through the reactor was uneven and the gastemperature distribution fluctuated even more. A similar situation occurredwith the configuration 12 reactor. It too consisted of 55-mm thick discs. Ahot region occurred between the two discs which melted the catalyst and cer-amic such that it flowed downstream. The weakened second disc broke apart.The pieces of the broken disc, solidified melted catalyst, and ceramic clothdisc wrap lodged on the upstream side of the nickel disc. This resulted inoverheating of portions of the nickel foil and it melted. What was left ofthe nickel foil disc after testing had soot deposits on the downstream face.This was the only situation during the test program that soot, or carbondeposits, were observed on the test pieces. It does not appear that simplyincreasing the thickness of the catalyst containing discs will give improvedresults.

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CONCLUSIONS

The test program results indicate the following:

1. For the flowrates of fuel and air tested, a hot stream of combustiblegases can be produced when using either platinum based or a palladium basedceramic monolith reactor.

2. A sustained reaction was attained at input air temperatures greaterthan 900 K at reactor loading levels of approximately 0.03 to -0.05 gfuel/sec/cmz of active catalyst surface.

3. The reactor output gases contained about 50 percent of the theoret-ical hydrogen and carbon monoxide for the attained gas temperature levels andvery low quantities of NO .

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4. The technique used to mount the ceramic catalyst pieces in thereactor as well as the sizing of the pieces is critical in order to maintainphysical integrity of the unit.

REFERENCES

1. Brabbs, T.A.; Rollbuhler, R.J.; and Lezberg, E.A.: Fuel-Rich CatalyticCombustion - A Fuel Processor for High Speed Propulsion. NASA TM-103177,1990.

2. Samuelsen, G.S.; and Harman, J.N.: Chemical Transformations of NitrogenOxides When Sampling Combustion Products. Univ. of Calif.-Irvine, J. AirPollution Control, vol. 27, no. 7, July 1976, pp. 648-655.

3. England, C.; Houseman, J.; and Teixeira, D.P.: Sampling Nitric Oxide FromCombustion Gases. Combust. Flame, vol. 20, June 1973, pp. 439-442.

4. Brabbs, T.A.; and Gracia-Salcedo, C.: Fuel Rich Catalytic Combustion UsingJet-A Fuel. NASA TM-101975, 1989.

5. Jones, R.E., et al.: Combustion Gas Properties I-ASTM Jet-A Fuel and DryAir. NASA TP-2359, 1984.

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13

Jet Afuel ^ ►r{`

Rotatinghot ceramicwheel

rt/^ • ,

Test air .- Flow^o l meter

Exhaust Flowgases \ --meter

^^1.

` Hot^^ test

sectionTestfuel

`Heat inletexchanger

unit

100

2750 —F-Second Reaction90 >

2500 1 stage ! temperature 80 ,c

@ 2250 reaction 70 0a^ Y / 1

E 2000

1

I 60 .N

E12

1750 ! 1

!First stage 50 Y

v 1500^^

rea lion 40 ° QE^'

1250^ itrogen 1 ^^ 30ro 1000 /oxide 1 1 Mixing, of first age 20 00 750 / emission I reaction products with --

L 500 i index X^ additional air 10 2

~ 0250

0 .2 .4 .6 .8 1.0 1.2 2 3 4 5 6 7Equivalence ratio

Figure 1.—Reaction of jet-A fuel with 860 Kair (ref.: NASA TP 2359 and LeRC cal-culations by C.B. Salcedo).

Features:

• Combustor test air flows up to 1 kgm/sec• Air temperatures from ambient to 1250 K• Air pressures from 1-10 atm

Liquid or gaseous fuel flows• Can flow a variety of fuels• Rapid change capability of above parameters• Gaseous emissions determination• Exhaust gases clean-up system• On-line date acquisition system

To roof-top gasclean-up system

Exhaustgases

MufflerHeater air

Flowmeter

iBurner .

Controlvalve

Figure 2.—High temperature transient facility, cell 23 C.R.L.

14

800 - 1050 Kcombustion air

Atomizing air

Fuel vaporization section

Fuel + air / n ^ Catalyst test piecesmixing nozzle (15 cm diam discs)unit

-r Gas sample probeHot gas

Test temperaturefuel readout

Television camera Hot exhaust gases

Figure 3.—Fuel-rich, catalytic reaction program hot test section.

15

Active catalyticsurface area,

®®®^®®®®° sq cm1 31Catalyst configuration 3 15 15 Nickel

25 mm thick ceramic discs—cell cell cell foil --- 7249 for ceramic discsplatinum base catalyst cm2 cm2 om2 disc 8160 for nickel disc

Catalyst configuration 4 15 15 31 3125 mm thick ceramic discs — —cell cell cell cell--- 10320 for ceramic discspalladium base catalyst cm2 cm2 cm2 cm2

Catalyst configuration 526 mm thick ceramic discs ^—

Nickel 15 15 31 31foil --- cell - cell - cell- cell --

8160 for nickel disc

platinum base catalyst disc cm2 cm2 cm 2 cm2 10320 for ceramic discs

U ®L1 EJ ® ®®

Last disc had no catalyst on it ---I

®19F9F9RFI®Catalyst configuration 6 15 15 31 31 3125 mm thick ceramic discs cell cell cell cell cell-- 10320 for ceramic discspalladium base catalyst cm2cm2cm2cm2cm2

®EjLI®®®®

Catalyst configuration 1255 mm thick ceramic discs —

- 62cell

62cell

Nickel— foil -- 21948 for ceramic discs

palladium base catalyst cm2 cm2 disc 8160 for nickel disc

Catalyst configuration 1455 mm thick ceramic discs _ Foam Foam Foam ?for foamed ceramicfoamed format mat'I marl marlpalladium base catalyst

Figure 4.—Test program catalytic reactor configurations. Mounted in a 15.3 cm diam duct

16

Ceramic discs with ceramictape wrapped around theirouter diameter; ceramicroping between the discs

Figure 5.—Fuel-rich catalytic reaction test program disc mountingtechnique.

Catalyst configuration 3

PC = Average pre-catalyst gas temperature1 = Average gas temperature after catalyst disc #12 = Average gas temperature after catalyst disc #23 = Average gas temperature after catalyst disc #34 = Average gas temperature after catalyst disc #4AC = Average after reactor gas temperature

Test A Test B Test C Test D419 g/s mass 430 g/s mass 431 g/s mass 444 g/s mass

925 K Tair 928 K Tair 931 K Tair 922 K Tair153.8 KPa 154.4 KPa 149.0 KPa 144.8 KPa

4.3 ER 4.7 ER 5.1 ER 5.6 ER4ACH2321

LHCCO

t

PC~•CO2

OI 2 4 6

4

AC 43 AC

3

?H 2 21LHC- LHC

CO H2

UPC

CO

1

^ CO2^—PCO2

L^J L{ I I I

0 2 4 6 0 2 4 6

Time. min

110X103

q 100

9C 90 aLHC 80

12 70 0

CO 60 N

H2 50 wf CO2 40

PC 30t °1 1

0 2 4 6

1500

1400

1300

Y 1200

1100

m 1000

E 900

800

700

600

500

Figure 6.—Fuel-rich, catalytic test program typical output data asa function of test time.

17

300Ya)

2 200NaEa)

a 100

0

600

500 number

3

400

-100

700

1

-200 ' I I I 1 '

3 4 5 6 7 8Equivalence ratio

Figure 7.—Fuel-rich, catalytic reaction test programoverall temperature change from input air temper-ature to reactor exhaust. Data from 0.40 kgm/secmass flow, 920 K input air temperature.

-200

r Theoretical fuel + airmixture temperature

I-300 I

^ I

m ConfigurationCL e numberEa -400 13 4 5'--

1412

-5003 4 5 6 7

Equivalence ratioFigure 8.— Gas temperature drop from that of input air

temperature to entering the catalytic reactor. Data from0.40 kgm mass flow/sec; input air temperature nominal920 K.

14

200

100

12

3 4 5 6 7Equivalence ratio

Figure 9.—Fuel-rich, catalytic reaction program rise ingas temperature across the ceramic catalyst pieces.Data from 0.40 kgm mass flow/sec; input air temper-ature nominal 920 K.

600

500

Y6 400N

27ro

`mE 300

18

Configuration 3

1391

1383 1390

1366 1387

1371 1377

1362 1372

1370 1369

1368

Average = 1376 K (+15/-14)

Configuration 4

1226

1331 1056

1242 1125

1327 1068

1212 1059

1332 1274

1099

Average = 1216 K (+116/-160)

Configuration 5

1221

1247 1207

1293 1209

1248

1218 1276

1239

Average = 1293 K (+54/-32)

Configuration 6 Configuration 12 Configuration 14

937 - -

1446 733 1159 - 879 -

961 1312 1256 1259 1171 1160

987 787 1236 1229 946 1127

1423 992 951 1215 992 1004

588 1422 1123 - 1105 1011

987 1207 1136

Average = 1047 K (+419/-460) Average = 1182 K (+77/-231) Average = 1053 K (+118/-174)

Figure 10.—Circumferential gas temperatures downstream of the catalyst reactor typical test data foreach tested configuration. Nominal flow rate of 0.4 kgm/sec; 935 K input air; 4.2 ER. View lookingdownstream. All temperatures measured approximately 4 cm from the duct centerline.

Configurationnumber

O 3

q 4A 5O 6V 12

16O 200-299• 300-399 gms/sec mass flowO 400-499O 500-599

14

012 G

♦0

a 10n O

-oX0

8

OAc 0(D

00

0

06

Z ^ v v ^ o4

^ y 0^

2 A lY

0'1 1 1 1 1

1050 1100 1150 1200 1250 1300 1350 1400

Reaction gas temperature, K

Figure 11.—Nitrogen oxides (NOx) concentration in thereaction gases. Input air temperature nominally 920 K.

19

Configurationnumber

10 O 3q 4A 5 G

9 O 6V 12O 200-299• 300-399 ms/sec mass flow8 0 400-499 g G

o G 500-599 0m

y OX 0o0 QOE 6 Wc 00 00 5 OV • v

Figure 14.—Honey-comb ceramic material catalyst reaction units4 before and after testing.

31050 1100 1150 1200 1250 1300 1350 1400

Reaction gas temperature, K

Figure 12.—Carbon monoxide concentration in the reactiongases; input air temperature nominally 920 K.

Configurationnumber

O 3q 40 5

10 O 6 0v 12Q N

90 300-399• 400-499 gms/sec mass flow0 500-599

8—0 (3

/Configur 070•

0O6 1c

0)

5

onguraton3p4

p A Nickel disc only

3

11050 1100 1150 1200 1250 1300 1350 1400

Reaction gas temperature, K

Figure 13.—Hydrogen concentration in the reaction gas;input air temperature nominal 920 K.

Figure 15.—Downstream side of catalyst configuration 14 foamedceramic pieces. Post run destruction from localized thermalexcess.

A catalytic reactor using either platinum based, or palladiumbased, catalyst is a dependable source of hot combustiblegases over a range of fuel-rich input conditions.

• A sustained reaction can be initiated and maintained when theinput air temperature is greater than 900 K and the catalystloading is about .03-.05 grams of fuel and air/sec/sq cm ofcatalyst surface.

The product gases from such a fuel-rich oxidation reaction arevery low in nitrogen oxides.

• A technique has been developed for mounting the ceramiccatalysts to minimize thermal shock destruction.

Figure 16.—Program conclusions.

Catalytic / First stagereactor / product gas

High Enginetemperature ,

^^^= f^^h^^ exhaustinput air

I / 1

L— Liquid L Mixing L Second stagehydrocarbon zone combustionfuel

Figure 17.—Two stage, catalytic initiated, combustor concept.

21

NASANational Aeronautics and Report Documentation PageSpace Administration

1. Report No. NASA TM —104423 2 Government Accession No. 3. Recipient's Catalog No.

AIAA - 91- 2463

4. Title and Subtitle 5. Report Date

Fuel-Rich, Catalytic Reaction Experimental Results

6. Performing Organization Code

7. Author(s) 8. Performing Organization Report No.

R. James Rollbuhler E -6256

10. Work Unit No.

537-01-119. Performing Organization Name and Address

11. Contract or Grant No.National Aeronautics and Space AdministrationLewis Research CenterCleveland, Ohio 44135 - 3191

13. Type of Report and Period Covered

Technical Memorandum12. Sponsoring Agency Name and Address

National Aeronautics and Space Administration14. Sponsoring Agency CodeWashington, D.C. 20546 - 0001

15. Supplementary Notes

Prepared for the 27th Joint Propulsion Conference cosponsored by the AIAA, SAE, ASME, and ASEE, Sacramento,California. June 24 -27, 1991. Responsible person, R. James Rollbuhler, (216) 433 - 3391.

16. Abstract

Future aeropropulsion gas turbine combustion requirements call for operating at very high inlet temperatures, pres-sures, and large temperature rises. At the same time, the combustion process is to have minimum pollution effects onthe environment. Aircraft gas turbine engines utilize liquid hydrocarbon fuels which are difficult to uniformly atomizeand mix with combustion air. An approach for minimizing fuel related problems is to transform the liquid fuel into agaseous form prior to the completion of the combustion process. Experimentally obtained results are presented forvaporizing and partially oxidizing a liquid hydrocarbon fuel into burnable gaseous components. The presentedexperimental data show that 1200-1300k reaction product gas, rich in hydrogen, carbon monoxide, and light-endhydrocarbons, is formed when flowing 0.3 - 0.6 fuel to air mixtures through a catalyst reactor. The reaction tempera-tures were kept low enough that nitrogen oxides and carbon particles (soot) did not form. Results are reported for testsusing different catalyst types and configurations, mass flowrates, input temperatures, and fuel to air ratios.

17. Key Words (Suggested by Author(s)) 18. Distribution Statement

Hydrocarbon combustion; Jet engine combustion; Unclassified - UnlimitedCombustion reactions; Combustion reaction products; Subject Category 07Catalysts activation

19. Security Classif. (of the report) 20. Security Classif. (of this page) 21. No. of pages 22. Price'

Unclassified Unclassified 11 A03

NASA FORM 1828 OCT 86 *For sale by the National Technical Information Service, Springfield, Virginia 22161

FOURTH CLASS MAIL

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Postage and Fees PaidNational Aeronautics arSpace AdministrationNASA 451

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