Burke—Schumann Flame with Streamwise and Preferential Diffusion

The classical diffusion flame model of Burke and Schumann is extended to include the effects of both streamwise and preferential diffusion. The study first identifies a Lewis-number-weighted coupling function as the proper one to use in formulations involving non-unity Lewis numbers. A perturbation technique is then developed for the realistic situation of near-unity Lewis number flows. Results show that, depending on the effective Lewis numbers of fuel and oxidizer, the flame temperature may vary either monotonically or non-monotonically along the flame sheet, and thereby suggesting the possibilities of tip opening, and tip intensification, as well as partial and complete flame blow-off.