Local Quenching Due to Flame Stretch and Non-Premixed Turbulent Combustion

Abstract

A turbulent non-premixed burning mixture is considered at a state close to extinction. The turbulent flame is conceived as an ensemble of thin laminar diffusion flamelets that are highly distorted and stretched such that they may be quenched locally. The structure of the laminar diffusion flamelets is analysed in the limit of a large activation energy and the results of Linan's analysis of counterflow diffusion flames are used to derive the quenching condition. This condition is expressed by an instantaneous scalar dissipation rate. Statistics of the scalar dissipation rate are discussed on the basis of Kolmogoroff's third hypothesis. Extinction condition of the whole turbulent flame are derived on the basis of the percolation theory.