Combustion LH2 with excess LO2 in pre-burner

[EYAGGELOS TSICHLAS]

Hi guys!

I am mechanical engineer and I make an article about the subject of  my thesis. I have designed two pumps for LH2 and LO2 in my thesis and I want to design the turbine in order to add it in the article. I have calculated the power (Kw) of the turbine including the  hydraulic losses of the pumps, the turbine and the mechanical losses of the gearbox. General, I can adjust all variables automatically by excel in case of false . But I face a problem about the way of calculating  enthalpy(h), temperature(T), specific heat capacity (Cp,Cv), pressure(P), kinematic viscosity(v), thermal conductivity(λ), the ration γ and density (ρ) of  exhaust gases in pre-burner. The cycle of rocket engine is open cycle with gas generator (pre-burner). I have set a small amount of fuel to burn with excess oxygen. The amount of hydrogen is adjusted based on the power of the tourbine and the amount of oxygen is adjusted manually. Below is the chemical equation for pre-burner combustion: xH2 +((x/2)+y)O2 -> xH2O + yO2. What formulas and parameters should I put in excel to automatically calculate the sizes (h,Cp,v,T,P....) after combustion in pre-burner? I have found some formulas of NASA for combustion LH2/LO2 but for burner LRE , not pre-burner. Also I don't know if I should put and others parametres for examble production of other products (Η2Ο2). I haven't designed the pre-burner yet. I am just designing the turbopump system and I want to start the design of the  turbine with a predetermined mixture of exhaust gases at the inlet. 

A solution I found recently are some NASA curves that calculate the Cp/R ratio for a certain temperature. This way I can also calculate the rest of the quantities with sums and averages. But I don't know if this approach is correct because I will start with an inlet temperature and make calculations assuming ideal combustion. Should I do it with an energy balance? Can anyone guide me or help me find additional formulas? Can any experienced researcher or professional on this field help me?

The fluids are cryogenic state. Βelow the table with the properties of the fluids :

 

properties	LH2	LO2
ν(mm2/s)	0,22917	0,27
ρ(m3/kg)	73,723	1223
Τ(Κ)	18	73
Pv (Pa) (vapor pressure)	49204	10810
Cp (J/(kgK)	8514	1678
λ(W/mK)	0,10319	0,1753

CFD analysis results showed that I have a total pressure of 198bar for LH2 and 124,6bar for LO2 at the pump outlet.

 

 

 

 

 

 

 

 

 

[magnemoe]

I say don't go oxygen rich, yes Soviet did it but they went full flow so they did not need to run it very hot, same with the space shuttle using hydrogen but its not practical with RP1. Raptor does this on both lines who is insane. 
Else using hydrogen you want to go hydrogen rich if the trust is not critical as the hot hydrogen gives lots of ISP. 

[EYAGGELOS TSICHLAS]

Thank you very much for your information! I have seen what you mentioned. However, I found this excess oxygen tactic from a turbo engine book. It is in Greek. I'll fix it. Do you have any idea about how to calculate the properties of the exhaust gases?