Mean Mixture Fraction

eseller · July 14, 2009, 14:55

I am using the non-premixed combustion model in Fluent and have generated a PDF Table ... It is an uni-element injector with an OFO (oxygen-fuel-oxygen) configuration. I am confused about the inputs for the mean mixture fraction (MMF) in the fuel and oxidizer boundary condition. Right now I have the MMF for fuel set to 1.0 and the oxidizer set to 0; when should these be varied and what is the impact? Also, in my initial conditions, the MMF is set to 0, is this correct? I was also under the impression that the temperature given in the initial values acts as the igniter for combustion, does anyone have any data supporting cryogenic propellants (methane and oxygen) on what this temperature should be set to?

One last thing, how can I define only one reaction using the non-premixed combustion model w/ PDF Table? And am I able to define the mechanism ... specify a two-step reaction?

Thank you, your help is very much appreciated!

--E

homeros · September 23, 2023, 12:42

MMF = 1 means there is only fuel on that region and MMF = 0 means there is only oxidizer on that region. And after combustion MMF should be zero if you dont have another combustion at downstream. I dont exactly know the other questions that you have written.

July 14, 2009, 14:55	Mean Mixture Fraction	#1
eseller New Member Erik Sellers Join Date: Jul 2009 Posts: 10 Rep Power: 17	I am using the non-premixed combustion model in Fluent and have generated a PDF Table ... It is an uni-element injector with an OFO (oxygen-fuel-oxygen) configuration. I am confused about the inputs for the mean mixture fraction (MMF) in the fuel and oxidizer boundary condition. Right now I have the MMF for fuel set to 1.0 and the oxidizer set to 0; when should these be varied and what is the impact? Also, in my initial conditions, the MMF is set to 0, is this correct? I was also under the impression that the temperature given in the initial values acts as the igniter for combustion, does anyone have any data supporting cryogenic propellants (methane and oxygen) on what this temperature should be set to? One last thing, how can I define only one reaction using the non-premixed combustion model w/ PDF Table? And am I able to define the mechanism ... specify a two-step reaction? Thank you, your help is very much appreciated! --E

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September 23, 2023, 12:42		#2
homeros New Member can Join Date: Aug 2023 Posts: 5 Rep Power: 3	MMF = 1 means there is only fuel on that region and MMF = 0 means there is only oxidizer on that region. And after combustion MMF should be zero if you dont have another combustion at downstream. I dont exactly know the other questions that you have written.