Non premixed combustion - combustion chamber pressure

Gadders · January 13, 2020, 22:13

Hi.

Have scoured this forum and the web but am still yet to find a satisfactory answer to my problem.

I'm working on a model of propene and nitrous oxide combustion in a small rocket combustion chamber. I have experimental data for mass flow rates and pressures (chamber and injectors) which I am using for inlet BCs and validation.

Others have written that the operating pressure should be the combustion chamber pressure, and so I have applied the value from my experimental data. Inlets are mass flow inlets, 300k and the outlet is a pressure outlet set to near vacuum with respect to the operating pressure.

The model produces sensible temperatures (combustion occurs), but the combustion chamber pressure is completely wrong (only 50000 Pa above exit, whereas it should be 500000).

Can anybody provide some suggestions as to what might be going on here?

Other info;
k-e realizable
adiabatic
RFL: 0.1 (stoichiometric mixture fraction is 0.096)
no of species: 20

Thanks,
Phil.

LuckyTran · January 14, 2020, 14:03

You might have a completely cold flow. Check your temperature field and make sure it looks like a combustion chamber and is not just a nozzle.

If that's not it. Then your BC's are wrong or your geometry is the wrong scale.

Gadders · January 14, 2020, 15:28

As I said before, the temperature in the combustion chamber is sensible (max around 3000K) - so definitely not cold and the dimensions of the model are correct.

My BCs are from experimental data and I have triple checked them.

January 13, 2020, 22:13	Non premixed combustion - combustion chamber pressure	#1
Gadders New Member Phil Gadsby Join Date: Sep 2015 Posts: 8 Rep Power: 11	Hi. Have scoured this forum and the web but am still yet to find a satisfactory answer to my problem. I'm working on a model of propene and nitrous oxide combustion in a small rocket combustion chamber. I have experimental data for mass flow rates and pressures (chamber and injectors) which I am using for inlet BCs and validation. Others have written that the operating pressure should be the combustion chamber pressure, and so I have applied the value from my experimental data. Inlets are mass flow inlets, 300k and the outlet is a pressure outlet set to near vacuum with respect to the operating pressure. The model produces sensible temperatures (combustion occurs), but the combustion chamber pressure is completely wrong (only 50000 Pa above exit, whereas it should be 500000). Can anybody provide some suggestions as to what might be going on here? Other info; k-e realizable adiabatic RFL: 0.1 (stoichiometric mixture fraction is 0.096) no of species: 20 Thanks, Phil.

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January 14, 2020, 14:03		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	You might have a completely cold flow. Check your temperature field and make sure it looks like a combustion chamber and is not just a nozzle. If that's not it. Then your BC's are wrong or your geometry is the wrong scale.

January 14, 2020, 15:28		#3
Gadders New Member Phil Gadsby Join Date: Sep 2015 Posts: 8 Rep Power: 11	As I said before, the temperature in the combustion chamber is sensible (max around 3000K) - so definitely not cold and the dimensions of the model are correct. My BCs are from experimental data and I have triple checked them.