Large-Eddy Simulation of a Swirling Diffusion Flame Using a SOM SGS Combustion Model

Abstract

Swirling flows and methane–air swirling diffusion combustion are studied by large-eddy simulation (LES) using a Smagorinsky-Lilly subgrid-scale (SGS) turbulence model, a second-order moment (SOM) SGS combustion model, proposed by the present authors, and an eddy-break-up (EBU) combustion model used by some investigators. The LES statistical results are compared with the experimental results and the Reynolds-averaged Navier-Stokes (RANS) modeling results using the Reynolds stress equation model and the SOM combustion model. For swirling flows, the LES statistical results give better agreement with the experimental results than the RANS modeling, indicating that the adopted SGS turbulence model is suitable for swirling flows. For swirling combustion, both the SOM SGS combustion model and the RANS-SOM model give results in good agreement with the experimental results, but the LES-EBU modeling results are not in agreement with the experimental results. The LES instantaneous results show large vortices formed in the shear layer and a complex vortex shedding pattern in the downstream region. It is shown that combustion weakens the vortex structures, combustion is intensified by the coherent structures, and swirl thickens the flame front.