Modeling Turbulent Transient Combustion

An analytical study has been performed to investigate the use of a one-dimensional combustion model for transient premixed flames under conditions similar to those occurring in a sparkignition internal combustion engine. The model consists of the numerical integration of the basic conservation equations for mass, momentum, energy, and species with the effects of turbulence modeled by the use of a turbulent diffusivity. In order to evaluate the effects of some of the assumptions and identify the significant parameters, a simplified system consisting of constant volume adiabatic combustion was considered. With simple chemical kinetics and constant turbulent diffusivity, there are three parameters in the problem: a non-dimensional speed of sound, a non-dimensional temperature rise due to combustion, and a Damkohler parameter relating diffusion and chemical reaction rate effects. Two types of flames were modeled, a flat flame in linear coordinates and a cylindrical flame. The effects of boundary conditions and numerical parameters were investigated. The calculated results for the cylindrical flame were compared to literature data for similar conditions.