Asymptotic and numerical study of diffusion flames with variable Lewis number and finite rate chemistry

We use an asymptotic method (from Linan [12]) to derive analytical expressions for the profiles of all thermodynamic and chemical quantities of a diffusion flame with variable density, nonuniform Lewis number and finite rate chemistry, and for different configurations (unsteady unstrained, steady strained and unsteady strained flames). The accuracy of results is checked using numerical simulations with the same chemical and transport models. These results are then used to quantify the effects of finite rate chemistry and different Lewis numbers on the flame structure. In particular, we show that the adiabatic flame temperature is not always a monotone function of the Lewis numbers, and we give simple expressions to predict the total heat release when the fuel and oxidizer Lewis numbers are different.