FLAME BROADENING AND ITS IMPACT ON THE APPARENT LEWIS NUMBER IN PREMIXED TURBULENT REACTING FLOWS

The effect of turbulent scales smaller than the laminar flame thicknes s on the laminar flame structure for flames with Lewis number (Le) dif ferent from the unity is considered. It is recognized that in this cas e the apparent Lewis number (Le) in the reaction zone differs from it s laminar value. This is due to spatial seperation between temperature and deficient reactant concentration profiles inherent in the laminar flames with Le not equal 1. Small turbulent vortices are shown to fur ther move these profiles apart in the broadened reaction zone. This re sults in further deviation of the Lewis number from unity. The apparen t Lewis number is shown to be dependent also on the ratio between the laminar dame thickness and the Kolmogorov length scale, i.e. Le = Le* (Le, delta/eta).