Application of combined LES and Flamelet modeling to Methane, Propane, and Jet-A Combustion

This paper reports on the performance of the flamelet model for diffusion flames when combined with the Large Eddy Simulation (LES) and assumed probability density functions for the mixture fraction and its dissipation rate. The flamelet equations are reduced to a set of first order ordinary differential equations and calculated very cheaply using Newton's iteration. The LES models support both the standard Smagorinsky and the dynamic approaches and are numerically calculated using the sixth-order compact diffusing and tenth-order filtering schemes. Time integration is done with the standard fourth-order Runge-Kutta procedure. The effects of three models for the probability density function of the mixture fraction are discussed. Also presented are various assumptions for the stoichiometric value of the mixture fraction dissipation rate and the effect on the combustion simulation results. The application of the developed procedures to the combustion of methane/air, propane/air, jet- A/air, and hydrogen/air are reported. In the case of methane, the performance for homogeneous turbulence and spatially-evolving mixing layers are also reported.