An approach to the theoretical description of turbulent jet diffusion flames—Part I: Combustion model and calculation

Abstract

The microscopic structure of the reaction zone in turbulent diffusion flames may be considered to be composed of numerous flame sheets, each of which behaves like a laminar diffusion flame. Wohlenberg [1] has proposed a combustion model for turbulent diffusion flames with the basic premise being that a large part of the macroscopic effects of turbulence on the reaction rate are accounted for by the increase in reaction interface extension due to the turbulence. Starting from this model, the authors proposed a model by attaching importance to the stretching of the reaction interface and the molecular diffusion of reactants, and introduced an equation giving the local reaction rate for turbulent diffusion flames. A function B involved in this equation expresses the effect of turbulence upon the reaction rate and is correlated with the local turbulent Reynolds number. The equation of local reaction rate was used as a source term of the conservation equations on turbulent diffusion flames. Using the GEMIX 4 program developed for boundary layers by Patankar and Spalding [2], numerical calculations were conducted on two coaxial jet diffusion flames of hydrogen and propane. A reasonably good agreement was found with the experimental results, e.g., flame shape, temperature distribution and coexistence of reactants.