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Species settings in combustion

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Old   April 28, 2020, 08:02
Default Species settings in combustion
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Koo How Boon
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Hi, there.
I am currently doing the premixed combustion in bunsen burner.
I have applied the reduced mechanism of Grimech 3.0 in my system.
Fluent always set the remaining species as N2, for example: I set my coflow inlet with pure nitrogen so I no need to put the mole fraction value in the boundary condition of coflow.
For my pressure outlet, I cannot put 0.209(mole fraction) for O2 because it implies that only 0.209 of O2 and 0.791 of N2 will extract from the system. However, if I didn't put anything on pressure outlet, it seems like my outlet condition will become a region with pure nitrogen.
My question is: What kind of species should I put on the pressure outlet region?
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Old   April 28, 2020, 11:54
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The species fraction at the outlet is determined by Fluent depending on the reactions or mixing inside the domain. The value that user specifies at the outlet is used only in case of flow reversal at the outlet. Otherwise, it has no effect. So, specify realistic values but do not worry much about it.

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Old   April 28, 2020, 11:57
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Thanks for your clarification
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