Combustion instabilities in swirling flows

Large-Eddy Simulation (LES) methodology has been used to model combustion dynamics in a real-istic swirling flow dump combustor. Two important design parameters, velocity swirl number (5) and fuel equivalence ratio ($), are parametrically altered to in-vestigate their relative impact on the dynamics. A premixed flamelet model is employed to capture the interaction of the unsteady flame-front with local ve-locity fluctuations. It has been observed that higher swirling velocity profiles, those large enough to induce vortex break-down, substantially reduce pressure (over 6 dB reduction) and flame-front oscillations. In addi-tion to swirl-vane angle effects, pressure amplitudes are shown to increase in the lean limit.