I am simulating a combustion proces. I am using a 4-step methane combustion model (Jones/Lindstedt) with the following species: Ch4/O2/CO2/CO/H2O/N2

I read in the fluent manual: ################################################## ##### The order of the species in the Selected Species list is very important. FLUENT considers the last species in the list to be the bulk species. You should therefore be careful to retain the most abundant species (by mass) as the last species when you add species to or delete species from a mixture material. ################################################## #####

So, what will be the correct order for the species? ED/FR is working, but EDC isn't. Thats the problem.

I don't thing, the order of the species will affect your calculation. The only condition is that, the species in abundant should be at the last. so the order you have mentioned here, Ch4/O2/CO2/CO/H2O/N2 will be ok.