[Federer83]

Hi all,

I would like to ask you some help on the following topic: how to set up supercritical mixing and combustion between LH2 and LO2 in a combustion chamber.

The aim is to replicate the results of the following paper with a very standard approach (i.e. standard models available in fluent)
https://www.researchgate.net/publica...ing_a_CFD_code)

The operating point is:

LH2:
T= 287K
mdot=0.07kg/s
LO2:
T= 100K
mdot=0.1kg/s
pc=60bar


Thanks in advance for your help,

Fab

[LuckyTran]

I would suggest to not overthink it. It's not that fancy. Just run species transport with a non-premixed or partially premixed combustion model. Rocket science isn't hard.

[Federer83]

Thanks for your answer. Yes I did it as you suggest but combustion temperature is overpredicted. However, at those temperatures and pressure the propellants are at supercritical conditions and not gas. Any suggestion?

[rewol]

OK here are some points and suggestions.

* Temperature overprediction is normal if you utilize 1 or 2-step reaction mechanism (which is suitable for EDM) for combustion. I suggest you perform your simulations with different combustion models too, such NON-PREMIXED or EDC, where temperatures will be considerably lower.

* As mentioned in the paper you linked, high-pressure corrected thermophysical properties must be added. You should write an UDF for those.

* You can use real-gas EOS already given in FLUENT but make sure you use van der Waals mixing rules.

* You can perform NON-PREMIXED combustion for initial solution and switch back to EDC later.

* If you are going to use steady / EDM, make sure you solve with ideal gas assumption first for initial solution then switch to real gas.

Good luck.

[LuckyTran]

The supercritical state is a state of matter. If it's a fluid (which it is) it's all the same nonetheless.

Originally Posted by Federer83

Thanks for your answer. Yes I did it as you suggest but combustion temperature is overpredicted. However, at those temperatures and pressure the propellants are at supercritical conditions and not gas. Any suggestion?

No where in Navier-Stokes is there a flag that cares whether it is solid/liquid/gas/plasma/tachyons. The state of the fluid doesn't matter. It's a fluid. Period.

Again, don't overthink it!


Where it does matter that they are supercritical is what happens in the mixing process of two supercritical fluids. You're not ready for this. You can revisit it once you're more comfortable with the simulation part and you actually come up with a new physical model (which you don't have yet).