Abstract
Conventional conserved scalar and presumed pdf methods have been widely used in prediction of non-premixed turbulent flames1, where a Lewis number of unity and fast chemical reaction rate are assumed, leading to a flame sheet structure, and where flow strain effects on the flame structure are also ignored. The effect of strain rate on a flame is of considerable technological interest and of fundamental importance. It has been established theoretically that straining a laminar premixed flame can reduce its burning velocity to the point of extinction2 and this also has been demonstrated experimentally3. Such strain effects on a laminar counter-flow diffusion flame have been extensively investigated experimentally and by numerical simulation4. It has been found that laminar diffusion flame structure strongly depends on stretch due to flow strain rate. Large strain rates may result in flame extinction, possibly leading to ignition delay in high speed flow. In the case of hydrogen-air flames, the Lewis number departs from unity due to the high diffusivity of hydrogen, and the effect of non-unity Lewis number may contribute to the energy redistribution, due to the molecular diffusion of heat and mass, which is usually ignored in the simulation of non-premixed turbulent combustion.
Published Version
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