Film Cooling in a Combustion Chamber

egkw34 · January 10, 2017, 08:56

Dear all,

I am trying to model fluid film cooling in a combustion chamber. I have used the fluid film model with evaporation in Star-CCM+. However, when looking at the results of the simulation, there is no drastic change in the film density to show that it has changed to a gas, despite the film temperature having exceeded boiling point.

Is there a set of models that can consider this, so as to provide a better indication of the film temperature and heat transfer downstream of where film evaporation has supposedly taken place?

me3840 · January 20, 2017, 02:35

I'm not sure it's density you want to be looking at. The wall film will only hold the condensed phase, so it's density should mostly be constant. You want to look at the film thickness.

egkw34 · January 20, 2017, 09:44

I wanted to look at density because of the mixing with the combustion flow, i wanted to see if the fluid film would be overcomed from the combustion flow and the temperature at the wall.

When i did the simulation i assumed that the model would capture that aspect as well, but it did not.

me3840 · January 20, 2017, 10:48

I would take a look at the fluid film model's theory in the user guide. You're assuming things it doesn't do. It is not capable of 'mixing' of any sort, the film model only models the film. If some process happens to remove mass from it, then that's the last thing it sees. Any mixing would happen outside the fluid film.

I'm not sure what you mean by overcome, though.

egkw34 · January 23, 2017, 07:36

Could you please view the two attached images? I think it will better clarify one of the issues

me3840 · January 23, 2017, 15:55

Is there any volume fraction of the methanol vapor in the main domain at all? You are suggesting none of it is evaporating, let's see if that's true.

egkw34 · January 26, 2017, 06:59

You were right! Thank you!

January 10, 2017, 08:56	Film Cooling in a Combustion Chamber	#1
egkw34 New Member Join Date: Jan 2017 Posts: 10 Rep Power: 9	Dear all, I am trying to model fluid film cooling in a combustion chamber. I have used the fluid film model with evaporation in Star-CCM+. However, when looking at the results of the simulation, there is no drastic change in the film density to show that it has changed to a gas, despite the film temperature having exceeded boiling point. Is there a set of models that can consider this, so as to provide a better indication of the film temperature and heat transfer downstream of where film evaporation has supposedly taken place?

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January 20, 2017, 02:35		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	I'm not sure it's density you want to be looking at. The wall film will only hold the condensed phase, so it's density should mostly be constant. You want to look at the film thickness.

January 20, 2017, 09:44		#3
egkw34 New Member Join Date: Jan 2017 Posts: 10 Rep Power: 9	I wanted to look at density because of the mixing with the combustion flow, i wanted to see if the fluid film would be overcomed from the combustion flow and the temperature at the wall. When i did the simulation i assumed that the model would capture that aspect as well, but it did not.

January 20, 2017, 10:48		#4
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	I would take a look at the fluid film model's theory in the user guide. You're assuming things it doesn't do. It is not capable of 'mixing' of any sort, the film model only models the film. If some process happens to remove mass from it, then that's the last thing it sees. Any mixing would happen outside the fluid film. I'm not sure what you mean by overcome, though.

January 23, 2017, 15:55		#6
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	Is there any volume fraction of the methanol vapor in the main domain at all? You are suggesting none of it is evaporating, let's see if that's true.

January 26, 2017, 06:59		#7
egkw34 New Member Join Date: Jan 2017 Posts: 10 Rep Power: 9	You were right! Thank you!