Verification

Equilibrium Properties

Comparison with a commonly used NASA equilibrium program CEA2 (Chemical Equilibrium and Applications 2) is performed for following test cases:

Parameter	Case #1	Case #2	Case #3	Case #4	Case #5
Chamber pressure, MPa	10	10	5	1	1
Oxidizer	LOX	LOX	N2O4	–	–
Fuel	LH2	RP-1	UDMH	N2H4	H2O2 (80%)
O/F	6.0	2.6	2.6	–	–

Comparisons for Case #1

Mole fractions:	Thermodynamic properties:
Species CEA2 RPA δ, % H 0.03107 0.03107(22) 0.0 H2 0.24803 0.24802(93) 0.0 H2O 0.67294 0.67294(23) 0.0 H2O2 0.00001 0.00001(26) 0.0 HO2 0.00003 0.00003(28) 0.0 O 0.00285 0.00285(11) 0.0 O2 0.00297 0.00297(14) 0.0 OH 0.04209 0.04208(81) 0.0	Parameter CEA2 RPA δ, % Temperature, K 3523.79 3523.79(2) 0.0 Enthalpy, kJ/kg -986.31 -986.30(8) 0.0 Entropy, kJ/(kg K) 17.613(2) 17.613 0.0 M, 1/n 13.513 13.513 0.0 Cp, kJ/(kg K) 8.2367 8.2367 0.0 γ 1.1425 1.1425 0.0 Sonic velocity, m/s 1574.0 1573.9(50) 0.0 ρ, kg/m3 4.612 4.612 0.0

Download Case #1 configuration file:	for RPA
	for CEA2

Comparisons for Case #2

Mole fractions:

Thermodynamic properties:

Species CEA2 RPA δ, % CO 0.31521 0.31521(14) 0.0 CO2 0.15383 0.15383(04) 0.0 COOH 0.00003 0.00002(73) 0.0 H 0.02686 0.02686(31) 0.0 H2 0.07954 0.07953(53) 0.0 H2O 0.33329 0.33329(25) 0.0 H2O2 0.00002 0.00001(88) 0.0 HCHO 0.00000 0.00000(11) 0.0 HCO 0.00004 0.00003(54) 0.0 HCOOH 0.00000 0.00000(41) 0.0 HO2 0.00011 0.00011(39) 0.0 O 0.01119 0.01119(34) 0.0 O2 0.01785 0.01785(26) 0.0 O3 0.00000 0.00000(01) 0.0 OH 0.06202 0.06202(05) 0.0

Parameter CEA2 RPA δ, % Temperature, K 3723.63 3723.63(4) 0.0 Enthalpy, kJ/kg -784.21 -784.2(06) 0.0 Entropy, kJ/(kg K) 11.127(5) 11.127 0.0 M, 1/n 23.603 23.603 0.0 Cp, kJ/(kg K) 6.026(3) 6.026 0.0 γ 1.1392 1.1392 0.0 Sonic velocity, m/s 1222.4 1222.4(29) 0.0 ρ, kg/m3 7.6236 7.6237 0.001

Download Case #2 configuration file:	for RPA
	for CEA2

Comparisons for Case #3

Mole fractions:

Thermodynamic properties:

Species CEA2 RPA δ, % CO 0.12784 0.12783(55) 0.0 CO2 0.08961 0.08961(06) 0.0 COOH 0.00001 0.00000(56) 0.0 H 0.01602 0.01601(60) 0.0 H2 0.06066 0.06066(30) 0.0 H2O 0.34503 0.34502(96) 0.0 H2O2 0.00001 0.00000(83) 0.0 HCHO 0.00000 0.00000(02) 0.0 HCN 0.00000 0.00000(03) 0.0 HCO 0.00001 0.00000(55) 0.0 HCOOH 0.00000 0.00000(08) 0.0 HNCO 0.00000 0.00000(05) 0.0 HNO 0.00001 0.00001(00) 0.0 HNO2 0.00000 0.00000(17) 0.0 HO2 0.00005 0.00005(11) 0.0 N 0.00001 0.00000(99) 0.0 N2 0.28780 0.28780(32) 0.0 N2O 0.00000 0.00000(28) 0.0 NCO 0.00000 0.00000(01) 0.0 NH 0.00000 0.00000(47) 0.0 NH2 0.00000 0.00000(26) 0.0 NH3 0.00000 0.00000(22) 0.0 NO 0.01110 0.01110(11) 0.0 NO2 0.00001 0.00000(91) 0.0 O 0.00610 0.00609(54) 0.0 O2 0.01340 0.01340(48) 0.0 OH 0.04233 0.04232(55) 0.0

Parameter CEA2 RPA δ, % Temperature, K 3392.31 3392.31(3) 0.0 Enthalpy, kJ/kg 88.271 88.271 0.0 Entropy, kJ/(kg K) 11.149(3) 11.149 0.0 M, 1/n 23.524 23.524 0.0 Cp, kJ/(kg K) 5.2960 5.296 0.0 γ 1.1385 1.1385 0.0 Sonic velocity, m/s 1168.4 1168.3(58) 0.0 ρ, kg/m3 4.1701 4.1702 0.002

Download Case #3 configuration file:	for RPA
	for CEA2

Comparisons for Case #4

Mole fractions:	Thermodynamic properties:
Species CEA2 RPA δ, % H2 0.66274 0.66273(76) 0.0 N2 0.33255 0.33254(75) 0.0 NH3 0.00471 0.00471(49) 0.0	Parameter CEA2 RPA δ, % Temperature, K 873.49 873.49(3) 0.0 Enthalpy, kJ/kg 1572.16 1572.149 0.0007 Entropy, kJ/(kg K) 15.784(2) 15.784 0.0 M, 1/n 10.732 10.732 0.0 Cp, kJ/(kg K) 3.054(0) 3.054 0.0 γ 1.3642 1.3642 0.0 Sonic velocity, m/s 960.8 960.8(21) 0.0 ρ, kg/m3 1.4777 1.4777 0.0

Download Case #4 configuration file:	for RPA
	for CEA2

Comparisons for Case #5

Mole fractions:	Thermodynamic properties:
Species CEA2 RPA δ, % H2O 0.74645 0.74645(36) 0.0 O2 0.25355 0.25354(64) 0.0	Parameter CEA2 RPA δ, % Temperature, K 784.47 784.46(7) 0.0 Enthalpy, kJ/kg -7589.64 -7589.608 0.0004 Entropy, kJ/(kg K) 9.819(7) 9.820 0.0 M, 1/n 21.561 21.561 0.0 Cp, kJ/(kg K) 1.7296 1.7296 0.0 γ 1.2869 1.2869 0.0 Sonic velocity, m/s 624.0 623.9(49) 0.0 ρ, kg/m3 3.3056 3.3056 0.0

Download Case #5 configuration file:	for RPA
	for CEA2

Conclusion

A perfect agreement is obtained between the CEA2 and PRA programs. Any percent differences in parameter values are in at least the third decimal place and are negligible. The maximum relative difference is 0.002% occurring for Case #3.

Engine Performance

In order to verify the accuracity of engine performance prediction, the program was executed with settings for a number of existing liquid propellant rocket engines.

See Examples to learn more about results of comparison.

Last modified: May 22, 2011