A Study on Retardation of Laminar Flame Extinction due to Locally Controlled Stretch Rate

Turbulent diffusion flame is supposed to be composed of a lot of laminar diffusion flamelets. To understand extinction processes of the flamelet, counterflow diffusion flame has been used. It was well known that the extinction strongly depends on stretch rate. But recently, it became to be known that the extinction limit was influenced by convection flow along the flamelet. Numerical computations of laminar counterflow diffusion flames have been conducted. It has been clarified that there are two types of extinction. One is intermittent extinction, and the other is perfect extinction. Extinction occurs slightly in downstream where local stretch rate is the largest. The maximum local stretch rate is much larger than extinction limit of flat flame. We investigated the effects of covection flow along the flamelet and clarified how much the extinction limit changes.