Large-Eddy Simulation of a Turbulent Lifted Flame in a Vitiated Co-Flow

Large-eddy simulation (LES) of a lifted flame in a vitiated co-flow has been performed using an unsteady flamelet/progress variable (UFPV) model. This model is an extension to the steady flamelet/progress variable approach, and describes the transient autoignition process of the lifted flame through the unsteady flamelet model. The particular advan-tage of this model is that it eliminates the flamelet time scale, and all thermochemical quantities are parameterized by mixture fraction, reaction progress parameter, and stoi-chiometric scalar dissipation rate. For application to LES, a presumed probability density function closure is employed, in which a beta-distribution is used for the mixture fraction, a statistically most-likely distribution is employed for the reaction progress parameter, and the distribution of the stoichiometric scalar dissipation rate is modeled by a Dirac delta function. Compared to the steady flamelet/progress variable model, predictions from the UFPV model show significant improvements, and the spatial evolution of the flame igni-tion process and lift-off height is in good agreement with experimental data. Flow field structure, statistical results, and scatter data are compared with experimental data, and potential improvements of the model are discussed. I