I think the activation energy was approximately 51 MJ. I've gone through that user guide. As you said, premixed combustion model doesn't calculate the species' mass fractions. I'm not concerned about the species. I'm trying to observe the flame front. The C-equation gave me a more jet spread and the Enhanced Coherent Flame Model (ECFM) didn't predict the flame front location properly. So, I moved to the Finite Rate/ Eddy Dissipation model. For this model, I should consider the species' mass/mole fractions.