Large eddy simulation of bluff-body stabilized flames using a multi-environment filtered density function model

Abstract

A multi-environment turbulent combustion model, originally developed for Reynolds averaged Navier–Stokes equations (RANS), was extended to large eddy simulation (LES) and was used to model a bluff-body stabilized flame series (HM1 and HM3) that ranges from near equilibrium to near global extinction. The multi-environment filtered density function model (MEFDF) depicts the filtered density function (FDF) as a weighted summation of a small number of multi-dimensional Dirac delta functions in composition space. It is derived from the transport FDF equation using the direct quadrature method of moments (DQMOM). The MEFDF method with multiple reactive scalars retains the unique property of the joint FDF model of treating the chemical source term exactly. It was coupled with a 19-species reduced mechanism based on quasi-steady-state assumption and an In Situ adaptive tabulation (ISAT) algorithm for chemical source term integration. The model successfully captures the level of local extinction of the two flames exhibited in experiment. The predicted radial profiles of mixture fraction, temperature and CO mass fraction are in good agreement with measurements. The current work highlights the potential of LES/MEFDF approach as a tool for modeling of turbulent flame stability and combustion dynamics as well as pollutant emissions.