Fluent Real Gas Model

Saha S · January 31, 2019, 23:36

Hello
I am trying to do supercritical combustion (250 bar) in Fluet Species Transport with reaction module. I have imported chemkin mechanism and inserted critical properties of each species. Now when I run the simulation, the console spits out the error that: only liquid solution is possible. But according to Fluet User Manual, once real gas model is selected, fluent does not recognize the saturation condition, by default it takes the mixture as a vapor condition. I am not sure what is causing the issue here.

LuckyTran · February 1, 2019, 11:45

It means that during the iteration process, you ended up at a state that put you in the liquid region. If you're truly super-critical then you should never be near this region anyway so you can interpret it as if your case has diverged.

Quote:

Originally Posted by Saha S

But according to Fluet User Manual, once real gas model is selected, fluent does not recognize the saturation condition, by default it takes the mixture as a vapor condition. I am not sure what is causing the issue here.

Where and in what context? And which Real Gas model? The NIST real gas model for example can be used in liquid or vapor but not the two-phase (liquid-vapor mixture region).

Saha S · February 1, 2019, 16:26

I am using Peng Robinson real gas model. I have two stream (fuel+water and oxygen) coming in the reactor at a pressure of 250 bar and 700K. None of my species has critical condition greater than that. So Fluent by default should treat them as vapor, right?

LuckyTran · February 3, 2019, 01:03

Okay but during calculation (iteration) the temperature and pressure can drop to who knows what and then you can end up with that warning.

Saha S · February 5, 2019, 17:36

Quote:

Originally Posted by LuckyTran

Okay but during calculation (iteration) the temperature and pressure can drop to who knows what and then you can end up with that warning.

Probably, but thats unlikely. because the reaction takes the temperature very high.should be fall something below saturation temp. Most importantly, ANSYS Fluent manual is saying that for real gas model they do not account for saturation point at all. Then there would be no question of having anything liquid!

LuckyTran · February 6, 2019, 10:16

You don't need to guess probably yes/no. You also don't need to think about whether it is ethical or not. Just look at your simulation results and see if the temperature/pressure is too low.

January 31, 2019, 23:36	Fluent Real Gas Model	#1
Saha S New Member Join Date: Jan 2016 Posts: 13 Rep Power: 10	Hello I am trying to do supercritical combustion (250 bar) in Fluet Species Transport with reaction module. I have imported chemkin mechanism and inserted critical properties of each species. Now when I run the simulation, the console spits out the error that: only liquid solution is possible. But according to Fluet User Manual, once real gas model is selected, fluent does not recognize the saturation condition, by default it takes the mixture as a vapor condition. I am not sure what is causing the issue here.

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February 1, 2019, 16:26		#3
Saha S New Member Join Date: Jan 2016 Posts: 13 Rep Power: 10	I am using Peng Robinson real gas model. I have two stream (fuel+water and oxygen) coming in the reactor at a pressure of 250 bar and 700K. None of my species has critical condition greater than that. So Fluent by default should treat them as vapor, right?

February 3, 2019, 01:03		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	Okay but during calculation (iteration) the temperature and pressure can drop to who knows what and then you can end up with that warning.

February 6, 2019, 10:16		#6
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	You don't need to guess probably yes/no. You also don't need to think about whether it is ethical or not. Just look at your simulation results and see if the temperature/pressure is too low.