NASA Technical Memorandum 106844

AIAA-95-6097

t t4 -_z_ffz010

?_ /Y

Numerical Study of Contaminant Effects onCombustion of Hydrogen, Ethane andMethane in Air

H.T. Lai

NYMA, Inc.

Engineering Services DivisionBrook Park, Ohio

and

S.R. Thomas

National Aeronautics and Space AdministrationLewis Research Center

Cleveland, Ohio

Prepared for theSixth International Aerospace Plane and Hypersonics Conference

sponsored by the American Institute of Aeronautics and Astronautics

Chattanooga, Tennessee, April 10-14, 1995

.___/ (NASA-TM-I06844) NUMERICAL STUDY

OF CONTAMINANT EFFECTS ON

COMBUSTION OF HYDROGEN, ETHANE, AND

METHANE IN AIR (NASA. Lewis

N_ionalAerona_icsand Research Center) 14 pSpaoeAdministr_ion

G3/Z8

N95-22114

Unclas

0042010

https://ntrs.nasa.gov/search.jsp?R=19950015697 2018-06-18T11:25:19+00:00Z

Numerical Study of Contaminant Effects on

Combustion of Hydrogen, Ethane and Methane in Air

H. T. Lai*

NYMA, Inc.Brook Park, Ohio 44142

and

S. R. Thomast

NASA Lewis Research Center

Cleveland, Ohio 44135

ABSTRACT

A numerical study was performed to assess the ef-

fects of vitiated air on the chemical kinetics of hydro-

gen, ethane, and methane combustion with air. A series

of calculations in static reacting systems was performed,where the initial temperature was specified and reactions

occurred at constant pressure. Three different types of

test flow contaminants were considered: NO, H20, and a

combination of HsO and CO2. These contaminants are

present in the test flows of facilities used for hypersonic

propulsion testing. The results were computed using a de-

tailed reaction mechanism and are presented in terms of

ignition and reaction times. Calculations were made for a

wide range of contaminant concentrations, temperatures

and pressures. The results indicate a pronounced kinetic

effect over a range of temperatures, especially with NO

contamination and, to a lesser degree, with H20 contam-

ination. In all cases studied, COs remained kinetically

inert, but had a thermodynamic effect on results by act-

ing as a third body. The largest effect is observed with

combustion using hydrogen fuel, less effect is seen with

combustion of ethane, and little effect of contaminants isshown with methane combustion.

INTRODUCTION

When providing the proper facility stagnation con-

ditions for testing supersonic combustors in ground-based

facilities, it is necessary to heat air to an enthalpy level

that matches the flight conditions. Typical heating tech-

niques used to generate this high enthalpy include electric

arcs, combustion of hydrogen or methane fuels in air with

oxygen replenishment, or storage heaters. The use of an

electric arc heater results in air dissociation and the gen-eration of significant amounts of nitrogen oxides, as well

as a depletion in the net level of oxygen below 21% by

volume. In combustion heaters, the flow constituents are

*Research Engineer, Member AIAAt Research Engineer

a function of the fuel used; for example, with a hydrogenburner HsO is a primary contaminant, or with a methane

heater a combination of both HsO and COs are the pri-

mary contaminants. Figures 1, 2 and 3 present the molefractions of the constituents in the test gas as a func-

tion of total temperature (and corresponding simulated

Mach number) for each of the heater types considered

in this study. Due to the presence of these test flowcontaminants, the combustion characteristics in a ram-

jet or scramjet engine can potentially be different thanresults obtained in clean air or actual flight. It is there-

fore important to understand these contamination effects

to properly interpret the test data obtained in ground

based experiments. The thermodynamic conditions of the

air flow passing through a ramjet or scramjet combustor

vary significantly across the flowpath due to the different

flight Mach numbers, varying amounts of compression,

the presence of flow separations, and combustion of fuel.

Prior to any combustion of fuel, and with no heat loss,

the local static temperature is a function of flight Mach

number and local Mach number as depicted in Fig. 4.

The local static pressure depends on the facility supply

pressure, local Mach number, and total pressure losses

through compression. For ramjet or scramjet engine sys-

tems tested in existing facilities at simulated Mach 5 to

7, the static pressure in the combustor typically ranges

up to about 5 atmospheres, and there are regions of low

pressure due to flow expansion through the nozzle. For

the flow through a scramjet combustor the residence time

is less than 1 millisecond; and for most geometries the

actual times will be significantly less. Ignition and reac-tion of the fuel and air must take place in less than this

time for performance to be attained in an engine. Theseranges of relevant temperatures and pressures, and max-

imum allowable ignition/reaction times provide a prelim-inary basis to assess the potential impact of the test flow

contaminants on ramjet/scramjet performance. In orderto accurately assess these effects on a specific configura-

tion a more detailed (two and three dimensional) analysiswould be conducted.

Various studies 1-6 have explored the effect of NO,

HsO, and COs contaminants on combustion processes,

primarily with hydrogen fuel with application to hyper-

sonic propulsion systems. These included both experi-

mentalandcomputationalstudies; a general trend fromthese works is that HsO and CO_ have a minimal influ-

ence on the kinetics of hydrogen-air combustion while NO

serves to reduce both ignition and reaction times. The

range of temperatures and pressure investigated and the

data base with fuels other than hydrogen are limited.

The objective of the present paper is to provide anassessment of the effect of NO, H20 and a combination

of H20 and COs on combustion of various fuels includ-

ing hydrogen, ethane and methane with air. The com-

putations were performed for a static system at constant

pressure, covering a broad range of initial temperatures,pressures, and chemical concentrations.

NUMERICAL METHOD

The results discussed herein are computed using theLewis General Chemical Kinetics and Sensitivity Anal-

ysis (LSENS) program 7-9, developed at NASA Lewis.

Any detailed reaction mechanism describing homoge-neous, gas-phase elementary reactions can be incorpo-

rated in the LSENS code. This is an important considera-

tion in the study of the possible effects of facility contam-

ination, since a global model may not be available and a

reduced mechanism may be insufficient. The numerical

integration method is derived from a general multi-step

scheme using an implicit backward difference formulation

designed to solve stiff systems of differential equations en-

countered in the analytical analysis of combustion. The

time-accurate results are computed to provide the impor-

tant trends of the contamination effects to guide both

future experiments and three-dimensional computations.

In this paper, two reaction models provided with

the LSENS code are employed. The first is a hydrogen/air

model consisting of 37 reactions involving 16 species. The

second is a comprehensive hydrocarbon/air model having133 reactions and 39 species. Description of these two

models with their chemical reaction equations and the

corresponding rate coefficients can be found in Ref. [9]. Incomputing the hydrogen combustion, the hydrogen model

allows faster computational time due to a lesser number

of reactions and species.

IGNITION AND REACTION TIME

COMPUTATIONS

The static model represents a combustor where air

or vitiated air and fuel are premixed and allowed to re-

act spontaneously. A typical temperature history is il-

lustrated as in Fig. 5, for three different stoichiometric

mixtures. Ignition and reaction are depicted by a rapid

increase to an equilibrium temperature from an initial

state. The ignition delay is the time required for the

mixture temperature to increase 5% of the equilibrium

temperature rise. Reaction time is defined as the time

increment between 5% and 95% of this temperature rise.

The ignition delay time can vary considerably depend-

ing on the the mixture composition. Flow contamination

can promote, impede, or even prevent ignition and reac-

tion. For the case outlined in Fig. 5, the presence of

CO2 and H20 results in a significant increase in ignitiontime. In all cases studied with clean air or with CO2

and H20 as contaminants the initial mole fraction of Oswas maintained at 21%. For other cases where NO was

a contaminant species, oxygen was considered depleted

from dissociation. Representative mixture compositionsfor these cases with NO contaminant are outlined in tableI.

H2 COMBUSTION

Calculation of ignition and reaction times has beencomputed for hydrogen combustion with different levels

of NO at four different pressures, 0.1, 1, 10 and 100 at-

mospheres, and initial temperatures of 800, 900, 1000,

1100 and 1200 °K. The results are shown in Figs. 6-9. Both ignition and reaction times decrease for low NOconcentration then increase with increased NO concen-

tration at lower temperature but are relatively insensitive

to NO variation at high temperature. The effect of NO

is generally pronounced within a temperature range fora prescribed pressure. At 0.1 atmosphere the difference

from clean-air results is minimal at all initial tempera-

tures. At 1 and 10 atmospheres, presence of NO can

results in a two order of magnitude reduction in ignition

and reaction times. At 100 atmospheres, the effect of NO

decreases, but is present over the complete temperature

range. There is a consistent increase in both ignition and

reaction times for large concentrations of NO.

The influence of NO on hydrogen-air combustion ispresent because NO directly affects the reaction rates.

It promotes chain-branching reactions when the level of

NO is low, and becomes active in three-body terminationreactions when NO is abundant 1,2, leading to a reduction

or an increase in ignition and reaction times, respectively.

Ignition and reaction times for hydrogen combustion

with HsO contamination are presented in Figs. 10-13 for

a similar range of pressures and temperatures. It is gener-ally observed that H20 has a small influence on the com-

bustion process. Effects are observed at 0.1 atmosphere

for the lowest temperature indicating a considerable delay

or absence in ignition for increasing H20 concentration.The reaction times remain unaffected in mixtures when

ignition was accomplished. In all, the temperature range

in which kinetic rates vary with pressure are confined to

a more narrow range as compared to the case of NO con-tamination.

The H20 contaminant is a relatively inactive species

and is involved predominantly in third-body reactions.

2

At particulartemperaturesandpressures, where thesethird-body reactions become important, the presence of

H20 can affect the overall kinetic characteristics. For

other conditions, H20 contributes primarily to changesin the thermodynamic properties of the mixture. One

specific thermodynamic effect is the reduction of equilib-

rium temperature due to the high heat capacity of H20.

The equilibrium temperature is always lower than the fi-

nal temperature achieved with clean air.

The influence of the H20 and CO2 contaminant

mixture is depicted in Figs. 14-17. A very similar varia-

tion in ignition and reaction times is observed with COs

addition as compared with H20 alone, suggesting no sig-nificant contribution by CO2 to the kinetic rates. Except

for the results at 800 °K and 0.1 atmosphere where com-

bustion cannot be obtained at high H_O and COs con-

tamination, the ignition and reaction times show smallsensitivity with respect to H20 and COs concentration

even up to 30% of the mixture's total composition. The

results show that COs does not have a significant kinetic

effect on hydrogen-air combustion over the present range

of temperatures, pressures and concentrations. The rea-

son for this is that COs is a stable species, which par-

ticipates only in third-body reactions, with a low third-

body collisional efficiency in most of the reactions. The

presence of CO2 still contributes thermodynamically by

causing an additional reduction in the equilibrium tem-

perature, below that of the combustion with H20, in allcases studied.

C2H6 COMBUSTION

Ignition and reaction times are shown in Figs. 18-

21. Ignition could not be achieved for mixtures at 800 °K

for all pressures. Thus the results are presented for tem-

perature of 900 °K and above. Contamination with NO

generally results in the same trend observed with hydro-

gen combustion, which is characterized by a reduction in

the ignition and reaction times over some range of tem-

peratures and concentrations.

The main contribution of NO is to enhance ignition.

Figure 18 demonstrates this characteristic since the cleanair mixture did not ignite at 900 °K but a small amount

of NO (1 to 1.5 %) resulted in ignition. Increasing NOconcentration beyond 1.5%, the mixture again failed to

ignite. The presence of NO tends to decrease ignition

time, particularly at lower levels of NO. The reaction time

tends to increase slightly or remains insensitive to the

presence of NO.

Ignition and reaction times varying with pressureat various temperatures for mixtures with 20% H20 con-

tamination are shown in Fig. 22 for ethane combustion.The effect is minimal and largest at low temperature and

pressure. For other level of H20 concentration, the vari-

ations similarly show very little difference.

The effect of CO2 and H20 contamination on ethane

combustion is illustrated in Fig. 23, and shows a variation

nearly identical to the results with H20 contamination

alone. There is a small increase in reaction times. As pre-

viously observed with hydrogen combustion, ethane-air-

H_O mixtures are kinetically unaffected by the presence

of COs. The effect of COs is thermodynamic due to its

large molecular weight and high heat capacity. In general,

ethane combustion is insensitive to H20 and CO2 contam-

ination, even at substantial levels of concentration, as was

for the case for hydrogen combustion.

CH4 COMBUSTION

Calculated ignition and reaction times

for methane/air combustion with NO contamination are

presented in Figs. 24-27. Methane does not easily ignitein air especially at low temperature and pressure and, in

cases where combustion can be obtained, it takes a consid-

erable time for the methane-air mixture to reach ignition

and equilibrium. The overall chemical kinetics of methanecombustion with NO contamination exhibits a character-

istic opposite to what has been observed for hydrogen

and ethane fuels. In a methane-air mixture, the effect

of NO is to increase ignition and reaction times, causing

combustion delay or no reaction. In Fig. 24, the clean-air

mixture reacts at 1100 °K, but vitiated mixtures with any

amount of NO do not at this temperature. Similarly at

100 atmospheres, Fig. 27, combustion can be achieved at

900 °K with 0 and 0.1% of NO, but mixtures with higher

NO concentration do not ignite. Changes in ignition and

reaction times are generally observed with small NO con-centration then remain constant as the level of NO is

increased. The changes appear somewhat insensitive to

variations in pressure and temperature. The variations

however are smaller in magnitude than in cases of com-

bustion with hydrogen or ethane fuel where a strongerinfluence of NO contamination is observed.

Ignition and reaction times for methane combustion

are depicted in Fig. 28 with 20% ltgO, and in Fig. 29 with20% H20 and 10% CO2. These results show virtually no

effect of flow contamination (H20 or a combination of

H20 and CO2) on the ignition time, and small influenceon the reaction time.

RESULT SUMMARY

The ignition and reaction time results for the series

of cases calculated in this study provide some general in-

sight to the potential effects of test flow contaminants on

ramjet/scramjet engine performance.

The results with hydrogen fuel show that the pres-

ence of NO, particularly at less than 1%, tends to promote

ignition and reaction within the range of flow conditions

predicted in scramjet combustors. The results for ethane

3

fuelwith NO as a testflow contaminant show some en- 2

hancement of ignitionand reaction,particularlyat NO

levelsup to 1% and statictemperature up to 1000 °K.

The resultsfor methane fuelwith NO as a contaminant

show a slightincreasein ignitionand reactiontimes. For 3

many of the conditionscalculatedwith ethane fueland

most conditionswith methane fuel,the ignitionand re-

action times are above 1 to 10 milliseconds.For these

conditionsan ignition/reactionaid such as a pilottorch 4

or injectionofanother (fasterreacting)ignitorgas would

be required.

The resultswith hydrogen fuel and eitherH_O or

the combination of H20 and CO2 as contaminants show

a slightincreasein ignitiontimes,but the overalleffects 5

are minimal. The resultswith both ethane and methane

fuelsand eitherH20 or the combination H_O and CO2 as

contaminants show minimal effectsofthese contaminants

on the ignitionand reactiontimes. As explained before,

for many of the conditionscalculatedthe ignitionand 6

reactiontimes exceed 1 to 10 millisecondsand a pilot

torch or a highly reactiveignitorgas would be required

to obtain combustion in an engine. 7

CONCLUDING REMARKS

This study has been conducted to explore the ki-

neticeffectof testflow contamination in airon the com-

bustion of hydrogen, ethane, and methane fuels. The

resultsshow that the presence of NO as a contaminant

could yield an enhancement of scramjet engine perfor-

mance during Mach 5 to 7 testing.The presence of H20

and CO2 did not substantiallyeffectthe ignitionand re-

actionkineticsfor most of the casesstudied. For many

of these cases,however, the ignitionand reactiontimes

were too high to allow combustion in a ramjet or scram-

jet engine,and an ignitionaid such as pilottorch or a

highly reactiveignitorgas would be required to achieve

combustion. For these cases (which particularlyinvolve

hydrocarbon fuels)unpiloted engine performance would

not be achievableand, toassessthe effectsofflowcontam-

ination,additionalcalculationswhich includea candidate

pilotgas should be accomplished. The overallresultsof

thisstudy show a potentialfor flow contaminant effects,

but experimental data is needed to isolate these effects.

Future computational efforts will include two and three

dimensional analysis to explore test flow contaminant ef-

fects on specific configurations.

Laster, W. R., and Sojka, P. E., "Autoignition of H2-

Air: the Effect of NOx Addition," :J. Propulsion, Vol.

5, No. 4, 1989, pp. 385-390.

Brabbs, T. A., Lezberg, E. A., and Bittker, D. A.,

"Hydrogen Oxidation Mechanism with Applications

to (1) the Chaperon Efficiency of Carbon Dioxide and

(2) Vitiated Air Testing," NASA TM-100186, 1987.

Rogers, R. C., "Effects of Test Facility Contaminants

on Supersonic Hydrogen-Air Diffusion Flames," Pre-

sented at the 23rd JANNAF Combustion Meeting,

Hampton, VA, Oct. 20-24, 1986.

Erickson,W. D., and Klich,G. F.,"AnalyticalChem-

icalKinetic Study of the Effectof Carbon Dioxide

and Water Vapor on Hydrogen-Air Constant-Pressure

Combustion," NASA TN D-5768, 1970.

Srinivasan, S., and Erickson, W. D., "Influence of

Test-Gas on Mixing and Combustion at Mach 7 Flight

Conditions," AIAA-94-2816, 1994.

Radhakrishnan, K., "LSENS, A General Chemical Ki-

netics and Sensitivity Analysis Code for Gas-Phase

Reactions, Part I: Theory and Numerical Procedures,"

NASA RP-1328, 1994.

l_dhakrishnan, K., and Bittker, D. A., "LSENS, A

General Chemical Kinetics and Sensitivity Analysis

Code for Gas-Phase Reactions, Part II: Code Descrip-

tion and Usage," NASA RP-1329, 1994.

Bittker,D. A., and Radhakrishnan, K., "LSENS, A

General Chemical Kinetics and SensitivityAnalysis

Code for Gas-Phase Reactions, Part III:Illustrative

Test Problems," NASA RP-1330, 1994.

NO H2 O2 N20.000 0.2958 0.1479 0.5563

0.005 0.2958 0.1454 0.5538

0.010 0.2958 0.1429 0.5513

0.020 0.2958 0.1379 0.5463

0.030 0.2958 0.1329 0.5413

0.045 0.2958 0.1254 0.5338

Table I: Mole fractions for hydrogen-air mixtureswith NO contamination.

REFERENCES

1 Slack, M., and Grillo, A., "Investigation of Hydrogen-

Air Ignition Sensitized by Nitric Oxide and by Nitro-

gen Dioxide," NASA CR-2986, 1977.

4

0.0.5,0

0.040

g___ 0.030

=_o 0.020

0.010

0.000 J

1 OOO 15100 20100 2500

TOTAL TEMPERATURE. KI I i I5 6 7 8

FLIGHT MACI"-I NUMBER

;OOO

Fig. 1 Nitric oxide in electric arc-heated test facilities.

1.00

0.50

zom- 0.20o<

-J 0.10O:}

0.05

I I

-------..__.__

0 2

I

N2

0.02 I i t

600 1000 1400 1800

TOTAL TEMPERATURE, K

L I I I

5 4 5 6 7

FLIGHT MACH NUMBER

Fig. 2 Flow vitiates in H2 combustion-heatedtest facilities.

2200

I

7.4

I .O0

0.50

zo_- 0.20o<

_, 0.10O

0.05

0.02

1000

0 2

C02 /

t 1 I I I

1200 1400 1600 1800 2000 2200

TOTAL TEMPERATURE, K

5 6 7 7.4

FLIGHT MACH NUMBER

Fig. 3 Flow vitiates in CH4 combustion-heatedtest facilities.

1600

1300

D

w1000

700

4OO

M.= 7(T=2200 K)

M.=6(

M.=5(_

I I I

2.0 2.5 3.0

Mla_:.l

Fig. 4 Static temperature variation withlocal Mach number.

2900

[ _ _ CLEAN AiR

CO _,--e--a3 G £_-,_ ....... "-_-] ...... 6 ....

150 250 350 450

TIME, /._

Fig. 5 Temperature profiles for hydrogen

combustion at 1 atmosphere and 1000 ° K.

x 2400

_J

w__ 1900 I

W

1400

i

900 '_

50

5

10 -1 I0-1

10 .2

uJ"

Z 10

zo-- 10-4

C O 0 0

[] [] [] O

k. A A & ,&

) O 0 0 0

C_

D

0 O

T= 800 K[3"'£] T= 900

T= 1000T=1100

H T- 1200i

4

I0 -2

LJ

z 10 -3

<

_ 10-4

10 -5 = T = 10 -5 i ,

0 1 2 3 5 0 1 2

_. NO _= NO

a) b)

0

T= 800 KT= 900T=IO00

<3--_ T=1100H T= 1200

I I

3 4

Fig.6 Ignition,a),and reaction,b),timesvs NO compositionsforhydrogenfuelat 0.Iatmosphere.

10 -1 10-1

10-2

F--Z I0-3

o

zo-- 10-4

10 -2

LJ

10_30

<

N 10-4

'_ _ T. 800K'_ G---El T= 900 rA"T _ T= 1000 I

) / _-.._ T= 1100 _]

> " ^ 0 0 _^ 0v v

1 2 3 4

% NO

a)

10 -5 10-5

0 5 0

_ E1

In

z

T= 800 KT= 90OT=IO00

_,_ T= 1100H T= 1200

1 2 3 4

g NO

b)Fig.7 Ignition,a),and reaction,b),timesvsNO compositionsforhydrogenfuel1 atmosphere.

10-1 ....

r-

z 10 .3

_o ,

"" 10 -4 /I _ T= 800 KT= 900

T= 1000

I0-51 _ , , i

5 0 I 2 3 4 5

% NO

b)

10-1 f ....

10-2

10-3 _

10 -4 _K

_ T=1100I0 -5 = , ,

0 1 2 3 4

_. NO

a)Fig.8 Ignition,a),and reaction,b),timesvs NO compositionsforhydrogenfuelat I0atmospheres.

I°-IL ' _=---__-8ooK I°-I

Z 10-3 L_ -- _ Z 10--3 L

-- 10-4 )e__._;&__._._ ,,n, 10-4, 10- ,0 1 2 3 4 5 0 1 2 3 4 5

% NO % NO

a) b)Fig. 9 Ignition, a), and reaction, b), times vs NO compositions for hydrogen fuel at 100 atmospheres.

6

10 -1

10-2

f...Z 10-3

--_ 10-4

13E3 []

.A A A

"CO 0

[]

A

O

,_(

T= 800[9---E] T= 900

T=1000_ T=1100

T=1200

T= 800 K(3'_E3 T= gO0

1"=1000T=1100T=1200

10 -5i i i i i I i L

0 4 8 12 16 20 4 8 12 16

% H20 % H20

a) b)

10 -1

m 10 2 rJ,,.

i.-z 10 -3g

_ lO-4

10 .5

0

Fig. 10 Ignition, a), and reaction, b), times vs H20 compositions for hydrogen fuel at 0.1 atmosphere.

10-1 _T- 900 KT=IO00T=1100

10 -2 1 _ T=1200

i 10_3

10 -4

10-5

z_o

5<

W

CO O 0

i i I i

4 8 12 16 20

% H20

a)

10 -1

10-2

10 -3

10 -4

10-5

0

T= SO0 K(3-'-El T= 900

T=IO00_---_ T= 1100

T= 1200

/

CC 0 0

10 -2

_J

:_- [] D [] D

_ 10_30

10-5 __ _0

0 4 8

% H20

a)

T= 900 K[3.--'E3 T= 1000

T=1100T=1200

10-5i i

12 16 20

Fig. 11 Ignition, a), and reaction, b), times vs H20 compositions for hydrogen fuel 1 atmosphere.

10 -1 10 -1 ,T= 800 K

m 10 -2

uJ-

z 10 -3

i-

,.<,r,, 10-4

OO O

T= go0T= 1000

,_.--.-_ T= 1100

i . _ J t

4 8 12 16 20

% H20

b)Fig. 12

10 -1

10-2 I

10-3Z

Z

-- 10-4

10-5

LC O

r-i 0

.* :,.

O0

Ignition, a), and reaction, b), times vs H_O compositions for hydrogen fuel at 10 atmospheres.

O O ' 10-1 'T= BOO

[3---D T= 900 I-z_k-'---_ T = 1000 m 10 -2

O-_ T=1100 _.-

IO-3L-

icc o on- 10-4

0 O _' []

l10-5

[]

i i i i i i i i

4 8 12 16 20 0 4 8 12 16

% H20 % H20

a) b)Fig. 13 Ignition, a), and reaction, b), times vs fI20 compositions for hydrogen fuel at 100 atmospheres.

C"----(DT= 800 K13"---E]T= 900

2O

2O

2O

i i i i

4 8 12 16

_. H20

b)

m

i--

z

o(_9

10 -1

10-2

10 -3

10 -4

10-5

m o

. ,5 A

' 0 0

rl

A

0

e--e T= 800{3--El T= 900

T= 1000'O--_ T=1100H T= 1200

i i i

15 20 25

T, H20+C02

a)

i0-I

m

F-Z

10-2

10-3

10 -4

10-5

0

r A

T= 800 K[3--E3 T= 900

T= 1000<_._ T= 1100

T=1200

i i l i I i i

5 10 30 5 10 15 20 25 30

Z, H20+C02

b)Fig. 14 Ignition, a), and reaction, b), times vs 1t20 and C02 compositions for hydrogen fuel at 0.1 atmosphere.

10-1' e---eT=9OOK 10-1 _ E_T= 800 K =1ooo 9001"=1100 _ T= 1000

10-2 _ T= 1200 10-2 _ T= 1100_ _ H T= 1200

Z 10-3L // _-Z 10 -3

s_o _ __ °-4 m ._-'-'/10 -4- _ 1 --

A A A0 0 0

10 -5 n i = n t 10 -5 i I n i ,

0 5 10 15 20 25 30 0 5 I0 15 20 25 30

7. H20+C02 _. H20+C02

a) b)Fig. 15 Ignition, a), and reaction, b), times vs H20 and CO2 compositions for hydrogen fuel 1 atmosphere.

i10-1 10-1 O--'e T= 800 K

T= 900) o o o _ T= 1000

10-2 (_--e T= 900 K '_'--'_ T=1100{3--E]T=1000 m 10 -2 r O O OIn

T=1100 L,J"_ T=1200 "_:E

-- ---43 [] []10 -3 z 10 -3

o --o O O 0-- I--I--

_o _ _ I°- 410 .4

10 -5 ,,,-...'/_ _ --

' _ ' 2'50 5 10 15 20 25 30 5 10 15 20 30H20+CO2 _, H20+C02

a) h)Fig.16 Ignition,a),and reaction,b),timesvs H20 and CO2 compositionsforhydrogenfuelat I0atmospheres.

10 -1 10 -1

') 0 0 0

T= 800T= go0 _ T= 800 K

,..., 10-2 Z_"_T=1000 ,z, 10 -2 13_-tDT= 900

I..,J" ._.---_ T= 1100 L,J"

10 .3 z 10 -3o_ 0 0 0-- CD

--_ _ 10 -410 -4

0 0 0 [] [] []

10 -5 10 .5i | i i i i i l + i

0 5 10 15 20 25 30 0 5 10 15 20 25 30T, H20+C02 Z H20+CO2

a) b)Fig. 17 Ignition, a), and reaction, b), times vs H20 and CO2 compositions for hydrogen fuel at 100 atmospheres.

8

z 10-3

-- 10-4 _-

10-5t

0 I

-"- A A A

e---eT=lO00 K[3._E]T=1100A----_T=1200

10 -1

10 -2

z 10 -3o_

N 10-4

C-_-'OT:IO00 K[3---£3T=1100_.'_&T:1200

, L 10 -5 t , , ,

2 3 4 5 0 1 2 3 4

NO _ NO

a) b)Fig. 18 Ignition, a), and reaction, b), times vs NO compositions for ethane fuel at 0.1 atmosphere.

10 -1 10-1

O._eT=lO00 K

[3'--'E]T=1100.,_,_-_T=1200

,., 10 -2

z 10 -3

_ 10-4

/6 8 o

-_0 0 [] 0 0 F_

C_'-_T=IO00 K13.---E]T=1100z_l._T=1200

10 -2tn

L,J"

10_3o

_ 10-4

10 -5 , , , , 10 -5 = , , ,

0 1 2 3 4 5 0 1 2 3 4

% NO % NO

a) b)Fig. 19 Ignition, a), and reaction, b), times vs NO compositions for ethane fuel 1 atmosphere.

T==IO00 K

m--_T.:11oozo

10 -1

10-2

10-3

10 -4

10-5

e---.eT=1000 K

13._E]T=1100Z_r-.._T=1200

.....--4D 0 C

10 -1

-

i ,_,, l i i i i L

1 2 3 4 1 2 ..3 4

% NO % NO

a) b)

10 -2

_E

_- 0-3z 1

z

--- 10-4

10 -5

10 -I

10-2!_n

2:10-3

_o

zo-- 10-4

Fig. 20 Ignition, a), and reaction, b), times vs NO compositions for ethane fuel at 10 atmospheres.

10-1 e._eT=lO00 KC _ 13--'E3T=1100,_'--"_T=1200

T=IO00 K[3-.--E] T=1100

T=1200

10-5 i i i i

0 1 2 3 4 5

NO

a)

10 -2

-32:10

o.<

10 -4

10 -5

o i i r2 3 4

% NO

b)Fig. 21 Ignition, a), and reaction, b), times vs NO compositions for ethane fuel at 100 atmospheres.

9

g3

Z

oI--

(D

ID

LJ

l--

Z

oI--

O

10.0000

1.0000

0.1000

0.0100

0.0010

I

Cleon AirE]---D H20 Vitioted Air

"'''-..

""'_°_...

100 J i

I _ Cleon Air

10 -1 D_ D--IE1H20 Vitioted Air

_- 10-2 .... "'"'-. =

g

%.

n- 10 4 '.'_T=1100 K

10 -5

0.1

0.0001 B i I I

0. I 1.0 I 0.0 00.0 1.0 I 0.0

P, otm P, otm

a) b)Fig. 22 H_O contaminant effect on ignition, a), and reaction, b), times in ethane combustion.

00.0

10.0000

1.0000

0.1000

0.0100

0.0010

0.0001

0.t

I I

Cleon AirE}--E]H20-C02 Vitioted Air

I .... .. []

I I

1.0 10.0 00.0

P, otto

100 I l

-I10

LE 10 -2

Z

o

_ 10 -3W

10 -4

10 -5

0.1

G---£ Cleon AirE_--FIH20-CO2 Vitioted Air

1T=12ooKI 1 I

1.0 10.0 100.0

P, otm

a) b)

Fig. 23 H20 and CO2 contaminant effect on ignition, a), and reaction, b), times in ethane combustion.

10

1.0000

0.o01o

0.0001

0

0.1000

LJ

z 0.0100g

z

z 0.0100

0.oo10

o. o

z 0.0100

z

0.0010

LJ

z 0.01000p-z

(,.9

O_-eT=1300 K

o c 1.0000

= 0.1000

0.01000

0.0010

;1 6 6 rl`5 ,5 -"- ,",

C---eT:llOOKI3---E]T=1200_T=1300

L , , 0.0001 , L ,1 2 3 4 5 0 1 2 3 4

NO _ NO

a) b)Fig. 24 Ignition, a), and reaction, b), times vs NO compositions for methane fuel at 0.1 atmosphere.

1.0000 _ 0 C) • • 0 1.0000 / e) _ m _ u(

0.1000 _ O [] D [] [] _ 0.1000 " riB---[] [] [] [] []

/T=1200 K _-. _ ,,5 .'k .t,. p,.

T=1300 z 0.0100

C-o,..5 e--eT=1100KE_E] T= 1200rr 0.0010 _ T=1300

0.0001 = , , L 0.0001 _ I .i ,

I 2 3 4 0 I 2 3 4

NO _ NO

a) b)Fig. 25 Ignition, a), and reaction, b), times vs NO compositions for methane fuel 1 atmosphere.

_.oooo_ ..... 1.oooo_ ....

o.1ooo _.c_. D [] [] [] [] _, 0.1000 • /B [] [] [] [] []

:-0.0100! a . _ _ a ao /

e--e T=1100 K _ _ O 0 0 0 0G---El T= 1200 LLI r"o.oolo cr'--eT=IO00KT=1300

I3._E3 T= 1100T= 1200T=1300

0.0001 , , , , 0.0001 , , .

1 2 3 4 5 1 2 3 4NO _ NO

a) b)

Fig. 26 Ignition, a), and reaction, b), times vs NO compositions for methane fuel at 10 atmospheres.

1.0000 ,..,// 1.00001 e_,e'T- _oo x '

la_ _ T= 1100_ T- 1200

0.1000 _ [] [3 D D | _ T-_SO00.1000_- J_-----_ [] m [] RF

& 2. A A _

0 0 0 0 0 ___,:,Z0.0100_ A &. .A ;%

° o o0.0010 _ T=IO00 K r_ 0.oo10

[3_-E3 T=I 1ooT=1200 )i( _ _ _"T= L_O0

0.0001 0.0001 I_ , ,_I I I I I I

0 1 2 3 4 5 0 1 2 3 4% NO % NO

a) b)Fig. 27 Ignition, a), and reaction, b), times vs NO compositions for methane fuel at 100 atmospheres.

11

go

b--

Z

o

O

tD

_3

g

o

Z

o

100.000 I i

Cleon AirD--F'IH20 Vitiated Air

,0.000

1.ooo

;...-.%

0.1 1.0 10.0 00.0

P, atm

a)

gO

Z

oI--

hir_

I0.0000 l ,

E_ --C'--_ CHI2e_viAl rote d Ak

1.0000 _.

ii oli0.0001 B T

0.1 1.0 10.0 100.0

P, atm

b)Fig. 28 H20 contaminant effect on ignition, a), and reaction, b), times in methane combustion.

100.000

10.000

1.000

0.100

0.010

I I

G---_ Clean AirE}--FIH20-C02 Vitiated Air

0.001 I I 0.0001

0.1 1.0 10.0 100.0 0.

P, etm

10.0000

1.0000

gO

0.1000

Z

o

0.0100

0.0010

I I

Clean AirI_--E3H20-CO2 Vitiated Air

I 1

1.0 10.0 100.0

P, otm

a) b)Fig. 29 H_O and COs contaminant effect on ignition, a), and reaction, b), times in methane combustion.

12

Form ApprovedREPORT DOCUMENTATION PAGE OMBNo.0704-0188

Publicreporting burdenlot thi coitecli_ of information_ estimated.Io averageI hourp_. r.espons+e.including+the tim lot revi+_m+'.n.+g++in.s.ttu.ctior_, learching existing +<:W+_+soum_._.gatheringandrnaJntakllngthe dataneeded,andcomplel.nng.an.drevmwlngthecollecbono( imocmatton.:_enocon'ln'Wntsregatomgtins.ouroeno_0mato0¢anyomer_a_S_l_.....mtin+collectionol Informmlon.Includingsuggestionslot reducingthusburden,toWashingtonHeadquarl.e,'sSe_rvces.Dlreclora.teforlnlo(matnofl.Ol=er'_tH_.._ Reports.1215_nemonDavisHighway,Suite1204,Arlmgton.VA222024302.andto Ihe Offce o(Managementand Buoget.PaperworkP(eouctK>nI-'rojec_(0704-0188),WaShington,ix.; _J.

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

February 1995 Technical Memorandum5. FUNDING NUMBERS4. TITLE AND SUBTITLE

Numerical Study of Contaminant Effects on Combustion of Hydrogen, Ethaneand Methane in Air

6. AUTHOR(S)

H.T. LaJand S_. Thomas

7. PERFORMINGORGANIZATIONNAME(S)ANDADDRESSEES)

National Aeronautics and Space AdministrationLewis Research Center

Cleveland, Ohio 44135-3191

9. SPONSORING/MONITORINGAGENCYNAME(S)ANDADDRESS(ES)

National Aeronautics and Space AdministrationWashington, D.C. 20546-0001

WU-505--62-52

8. PERFORMING ORGANIZATIONREPORT NUMBER

E-9409

10. SPONSORING/MONITORINGAGENCY REPORT NUMBER

NASA TM- 106844AIAA-95--6097

11. SUPPLEMENTARYNOTES

Prepared for the Sixth International Aerospace Plane and Hypersonics Conference sponsored by the American Institute ofAeronautics and Astronautics, Chattanooga, Tennessee, April 10-14, 1995. H.T. Lai, NYMA, Inc., Engineering Services

Division, 2001 Aerospace Parkway, Brook Park, Ohio 44142 (work funded by NASA Contract NAS3-27186); S.R.Thomas, NASALewis Research Center. Responsible person, S_R. Thomas, organzzation code 2701, (216) 433-8713.

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Unclassified -Unlimited

Subject Categories 20, 28, and 34

This publication is available from the NASA Center for Aerospace Information, (301)621--0390.

13. ABSTRACT (Maximum 200 words)

A numerical study was performed to assess the effects of vitiated air on the chemical kinetics of hydrogen, ethane, andmethane combustion with air. A series of calculations in static reacting systems was performed, where the initial tempera-tare was specified and reactions occurred at constant pressure. Three different types of test flow contaminants were

considered: NO, 1-120,and a combination of 1-120and CO 2. These contaminants are present in the test flows of facilitiesused for hypersonic propulsion testing. The results were computed using a detailed reaction mechanism and are presentedin terms of ignition and reaction times. Calculations were made for a wide range of contaminant concentrations, tempera-tares and pressures. The results indicate a pronounced kinetic effect over a range of temperatures, especially with NO

contamination and, to a lesser degree, with H20 contamination. In all cases studied, CO 2 remained kinetically inert, buthad a thermodynamic effect on results by acting as a third body. The largest effect is observed with combustion usinghydrogen fuel, less effect is seen with combustion of ethane, and little effect of contaminants is shown with methanecombustion.

14. SUBJECT TERMS

Contaminants; Hydrogen; Methane; Ethane; Ignition time delay; Reaction time;

Scramjet; Combustor

17. SECURITY CLASSIFICATIONOF REPORT

Unclassified

NSN 7540-01-280-5500

18. SECURITY CLASSIFICATIONOF THIS PAGE

Unclassified

19. SECURITY CLASSIFICATIONOF ABSTRACT

Unclassified

15. NUMBER OF PAGES14

16. PRICE CODE

A0320. LIMITATION OF AB:_ HACT

Standard Form 298 (Rev. 2-89)Prescribedby ANSI Std. Z39-18298-102