An Attempt at Large Eddy Simulation for Combustor Modeling

Abstract

Large eddy simulation (LES) is recognized as a promising method for numerical simulation in combustion systems. A LES attempt in a model combustor has been made, and a few important issues including grid size, inflow condition, wall boundary conditions, physical sub-models and data sampling, have been carefully considered. It is found that the turbulence forcing with the vortex method at the air/fuel inlets does not affect the LES results for the present configuration and the turbulence can develop naturally in the inlet section. Moreover, significant computing power is required for LES to capture both the high and low frequencies of interest in a turbulent reacting flow. In the paper, some of the numerical results are presented and compared with a comprehensive experimental database, which indicates that LES can provide reasonable predictions for the mean axial velocity and temperature distributions inside the combustion chamber. However, in order to make LES a valuable and cost-effective tool in the development of advanced combustion systems, some fundamental questions remain to be addressed and more validation efforts are required.

RANS Modelling of Turbulence in Combustors

“…Turbulence is characterized by irregularity or randomness, diffusion, vortices and viscous dissipation, and involves a wide range of time and length scales. Despite the rapid development of computing power, large eddy simulations are limited to benchmark cases with relatively simple geometries, while direct numerical simulations of turbulent flows remain practical only at low Reynolds numbers [2][3][4]. It is particularly true for turbulent reacting flows.…”