Large eddy simulation of a turbulent jet flame with inhomogeneous inlets using a two mixture fraction flamelet modeling approach

A revised flamelet/progress variable (FPV) model in which two mixture fractions are defined has been developed to extend the range of applicability of flamelet models to include systems with inhomogeneous inlet conditions. The revised model is applied in Large Eddy Simulation of the modified University of Sydney turbulent jet burner with a compositionally inhomogeneous fuel inlet. The two mixture fractions Z and Z∗ characterize central jet/coflow mixing and fuel/air mixing, respectively. The flame structure predictions between the simulations using this new approach are compared in detail to experimental data for an inhomogeneously mixed case and a homogeneously mixed case. It is shown that the two mixture fraction model improves agreement with the experimental data in comparison to a single mixture fraction model, but some minor discrepancies remain. The effect of increasing grid resolution is examined to explain some of the discrepancies.