2d axisymmetry problem
 

hi everybody!
i've modeled a microburner as a channel with a temperature gradient on its wall and get a result.then i try to model it in axisymmetric form with the same temperature gradient,but i don't have any flame in this form.Does anyone know why this is happening?

the fuel is methane and it burns in stoiciometric values with pure oxygen and the temperature varies between 300 to 1300K.

thanks in advance