Abstract
The structure and extinction of quasi-one-dimensional diffusion flames with general Lewis numbers for both fuel and oxidizer are analyzed using large activation energy asymptotics for the model problems of spherically symmetric droplet combustion, counterflow combustion, and stagnation point combustion over a condensed fuel. General matching and jump conditions up to the first order of expansion are derived. It is shown that by suitably redefining certain parameters the structure equations for all cases can be brought to the same form as that of Liñán so that his numerically generated extinction Damköhler number correlation can be readily used. Combining this with our own numerical result of the reactant leakage correlation, the extinguishability of a given system can be assessed. The present extinction criterion with general Lewis numbers also provides improved accuracy in the determination of overall kinetic constants through correlation of experimental extinction data.