Hi everyone,

I am a user of Fluent 6.3. I want to use a non-premixed combustion model with equilibrium chemistry. According to Fluent manual to calculate the mean mixture fraction for the considered species i need to know the distribution of those species in the mixture fraction space. I am starting with combustion and im not very good in chemistry. I know how to calculate the equilibrium constant and find the molar mass fraction of each species for certain temperature and pressure, but i dont know how to transform those information into the mixture fraction space. Could anybody give me some suggestions how to do this.

Thanks for your help, Peter

You are doing wrong. The first thing you have to do is to build the PDF (probabilistic density function) that way you will get the mean mixture fraction for the considered species.

Hey Pablo,

According to Fluent manual, mean mixture fraction for the species can be calculated from:

fi_bar = integral ( PDF(f) x fi(f) )df eq 15.2-16

so to get the mean mixture fraction you need to integrate the product of pdf and fi(f). This fi(f) suppose to come from equilibrium chemistry, but i am not quite sure how it is defined in Fluent.

Thanks for your answer, Peter