Large Eddy Simulations of the Vortex-Flame Interaction in a Turbulent Swirl Burner*

A series of swirl-stabilized flames are simulated using large eddy simulation along with the flamelet based model for combustion. The target burner has separate and concentric methane and air streams, with methane in the center and the air flow swirled through the tangential inlets. By fixing the swirl number and air flow rate, the fuel jet velocity is reduced to study flame stability as the flame approaches towards the lean blow-off limit. Simulation results are compared against measured data, yielding a generally good agreement on the velocity, temperature, and species mass fraction distributions. The proper orthogonal decomposition method is applied on the velocity and progress variable fields to analyze the dominant unsteady flow structure, indicating a coupling between the vortex and the flame. The effects of vortex-flame interactions on the stabilization of the lifted swirling flame are also investigated. For the stabilization of the lifted swirling flame, the effects of convection, enhanced mixing, and flame stretching introduced by the vortex structure are assessed based on the numerical results.