premixed combustion

Bücherknopf · July 6, 2016, 07:26

Hello guys,

I´m trying to run a premixed combustion. But I have following problem: I dont understand what the "unburnt gas" setting mean?
In my case I want to inject 100% CH4(=fuel). That means, that the initial fuel fraction has to be 0% or something near 0%.
Now if I set CH4=1 in the "unburnt gas" setting (because I think here I set the fuel composition) my screen shows me, that my chamber is filled with CH4=1. Why does the fuel mass fraction shows me a different picture than the mass fraction of CH4?

Can somebody explain to me, what this Fluid Stream Manager>"unburnt gas" setting mean and also how I can fix my simulation?
I´m glad about every suggestion?

marmot · July 7, 2016, 03:35

combustion is not my field but I believe it is good to check the manual for the definition of fuel mass fraction and mass fraction, you also have N2 or O2 in the system as well correct this could explain differences you see.

perhaps running through the tutorial Coherent Flame Model, Premixed Propane would help.

Bücherknopf · July 7, 2016, 04:37

Thank you for your reply. (again

)

I already did the tutorials and also searched in the user guide for "unburnt gas", but all the things that I find dont help me properly.

Also I know that I have O2 and N2 in the system, but my fuel is at the begining 100% CH4. But if I do this like it's done in the tutorial the fuel fraction scene doesnt show me the same picture as the CH4-fraction scene.

July 6, 2016, 07:26	premixed combustion	#1
Bücherknopf New Member Join Date: May 2016 Posts: 17 Rep Power: 9	Hello guys, I´m trying to run a premixed combustion. But I have following problem: I dont understand what the "unburnt gas" setting mean? In my case I want to inject 100% CH4(=fuel). That means, that the initial fuel fraction has to be 0% or something near 0%. Now if I set CH4=1 in the "unburnt gas" setting (because I think here I set the fuel composition) my screen shows me, that my chamber is filled with CH4=1. Why does the fuel mass fraction shows me a different picture than the mass fraction of CH4? Can somebody explain to me, what this Fluid Stream Manager>"unburnt gas" setting mean and also how I can fix my simulation? I´m glad about every suggestion?

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July 7, 2016, 03:35		#2
marmot Senior Member kevin alun Join Date: Sep 2011 Location: Germany Posts: 106 Rep Power: 14	combustion is not my field but I believe it is good to check the manual for the definition of fuel mass fraction and mass fraction, you also have N2 or O2 in the system as well correct this could explain differences you see. perhaps running through the tutorial Coherent Flame Model, Premixed Propane would help.

July 7, 2016, 04:37		#3
Bücherknopf New Member Join Date: May 2016 Posts: 17 Rep Power: 9	Thank you for your reply. (again ) I already did the tutorials and also searched in the user guide for "unburnt gas", but all the things that I find dont help me properly. Also I know that I have O2 and N2 in the system, but my fuel is at the begining 100% CH4. But if I do this like it's done in the tutorial the fuel fraction scene doesnt show me the same picture as the CH4-fraction scene.