Studies of the turbulent burning velocity

Abstract

A laminar flamelet model of pre-mixed turbulent combustion is described in which a characteristic length scale L̂ y controls the flamelet surface-to-volume ratio. An analysis, based on the Bray-Moss-Libby model of turbulent combustion, leads to the conclusion that L̂ y /l is proportional to the ratio of the laminar burning velocity to the turbulence velocity u' , where l is the integral length scale of the turbulence. A fractal flame model and an analysis of experimental time series data both support this conclusion. Several different theories for the turbulent burning velocity are shown to be equivalent to each other and to be generalizations of the classical theory of Kolmogorov, Petrovski & Piskonov. A method of characteristics analysis confirms the resulting expression. This expression, containing only one disposable constant which must be of order unity, is compared with a published correlation of a large amount of experimental data. This leads to an experimental determination of the ratio of effective to true laminar burning velocities, as a function of Karlovitz number, which shows satisfactory agreement with results of strained laminar flame calculations.