Abstract
Large eddy simulation (LES) methodology is essentially used to model combustion dynamics in a swirling dump combustor. The aerodynamic effects of swirl and their resulting effects on flame stability and pressure oscillation are investigated, and it is noted that swirl numbers if above a certain critical value leads to the recirculating or breaking down of center-line axial flow, commonly known as Vortex-Breakdown. This chapter illustrates the impact of premixer swirl number, S, on the stability of a model swirl-stabilized, lean-premixed gas turbine combustor, which is numerically simulated using LES methodology. Unsteady vortex-flame and acoustic-flame interactions are essentially captured using premixed flamelet model “G-equation.” It is noted that for large values of five, those sufficiently high for vortex breakdown to occur, the fluctuating pressure amplitudes, p', are attenuated significantly. The reduced p' amplitudes are accompanied by reduced longitudinal flame-front oscillations and reduced coherence in the shed vortices. Furthermore, the chapter also explores a methodology for active control based on modulation of S. Open-loop control through S variation is demonstrated for a lean mixture with significant reductions in fluctuating mass-flow rate and p' after a convective time delay.
Published Version
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