LARGE-EDDY SIMULATION OF LIFTED TURBULENT METHANE/AIR DIFFUSION FLAMES

Abstract

In recent years laminar flamelet models for turbulent non-premixed combustion have been successfully applied in Large-Eddy Simulations (LES). However, these models cannot describe premixed or partially premixed flame propagation, which is known to be of great importance in the stabilization region of lifted diffusion flames. In the present work a model proposed by Peters (2000) for Reynolds averaged models has been formulated for LES. Flamelet models for premixed and non-premixed combustion are combined to describe premixed, partially premixed, and non-premixed combustion. The G-equation model is used to describe premixed flame propagation. The turbulent burning velocity of the sub-grid scales appearing in this equation is evaluated as function of mixture fraction. The partially premixed post-flame region is described by a steady state laminar diffusion flamelet approach. The model is applied in numerical simulations of lifted methane/air diffusion flames. The predicted lift-off heights are in reasonable agreement with experimental data.