The effects of swirler vane configurations on the vortex-mixing interaction and combustion stability in a low-emission combustor

Particle Image Velocimetry (PIV) measurements and Large Eddy Simulation (LES) simulations are conducted for non-reacting and reacting flows to investigate the effects of swirler vane configurations on the vortex-mixing interaction and combustion stability in a low-emission tower-type coaxial-staged combustor (LETCC). Results show that the LES simulation results agree well with the experimental data. The combustor without vane lobes exhibits large mixture fraction bubbles in the inner shear layer (ISL) in non-reacting flow, and shows unstable combustion in reacting flow. Adding lobes to the first main stage swirler vanes eliminates instability factors in both non-reacting flow and reacting flow. Adding lobes to the second main stage swirler vanes suppresses mixture fraction bubbles in the ISL, but forms large areas with low mixture fraction in the outer shear layer (OSL) and outer recirculation zone (ORZ) in non-reacting flow, and induces localized flame extinction and re-ignition within the ORZ in reacting flow, leading to combustion instability.