Study on the preferential diffusion effects in premixed turbulent flame by direct numerical simulation

Direct numerical simulation of turbulent flame propagation was carried out in two-dimensional space. Preferential diffusion in the turbulent propagating flame was investigated in this study. Modified equation of reaction rate was proposed in order to take into account the local change of equivalence ratio caused by preferential diffusion. Diffusion coefficient of fuel was varied artificially keeping the other mixture properties constant to examine the effect of preferential diffusion alone. Preferential diffusion occurred even in the strong turbulent and reacting field if the coefficient of fuel was different from that of oxygen. Mass flux of the high diffusivity component into the flame increased in the convex flame area to the unburned region. Mass flux of the low diffusivity component decreases in this area. Local change of equivalence ratio was observed in the turbulent propagating flame regardless of the initial equivalence ratio. Mixture became rich or lean locally according to the curvature of the flame front in the vicinity of the flame.