Thanks for the response, wcao! I was specifically referring to the non-adiabatic premixed combustion mechanism. Just to confirm, the non-adiabatic premixed combustion mechanism uses the same PDF calculations as the partially-premixed combustion mechanism? This would make sense based on what I see in the data. Neglecting radiation, the mixture fraction of the premixed combustion mechanism is constant and, anecdotally, the unburnt properties appear to be constant throughout the model as well. I appreciate the assist.