steady or unsteady equation?

Harry Qiu

Hi, Mr. or Mrs.:

It may be a fundamental question, while I really don't know.

I'm modeling laminar premixed combustion of methane-air, but I always get poor reaction front result or even sometimes the flame "extinct". So can you tell me which one of the steady or unsteady equation is more apropriate for the laminar premixed combustion of methane-air? if the unsteady one is better, then what time step should be specified?

thank you very much.

Sincerely yours, Harry.