Large eddy simulations of the Darmstadt turbulent stratified flame series

Abstract

Large-eddy simulations of the Darmstadt turbulent stratified flame (TSF) burner are presented. The TSF burner is operated under a wide variety of conditions. A case without stratification or shear, and one with stratification but no shear, are considered for validation purposes. A combined mixture fraction and reaction progress variable approach is used, with the reaction rate modelled by a fractal flame wrinkling flame surface density model, where the laminar flame speed is obtained as a function of the mixture fraction. The simulation results and the suitability of the modelling approach are verified and validated through comparison of mean and variance of axial and radial velocity, temperature and mixture fraction with experimental data. The effects of stratification on the flame flow field are then studied by comparing the two reactive simulations, and studying the impact of the cross-scalar dissipation rate term. Finally, the occurrence of potential back- or front-supported stratification is examined through statistical analysis of the flame normal directions. The modelling approach employed was found to produce very good predictions of the TSF burner, with both back- and front-supported stratification modes occurring, the former being considerably more likely.