Detailed transient flow evolution were numerically analyzed in multi-cavity combustors at high supersonic flight condition in order to understanding the flow characteristics at initial stage of ignition start-up. To evaluate the accuracy of solution methdology and physical models, computational experiments were carried out. Fairly good match of the wall pressure has been obtained with experimental data for both nonreacting and reacting flows. Based on the hot-spot ignition model, the unsteady combustion processes of three seperated conditions were described and compared. Initial ignition point positions, which controlled by many factors such as local total temperature, total pressure and flow velocity, have been found to affect the flow pattern of stable combustion. The phenomena of mainstream flameout, countercurrent flame propagation and mainstream reburning have been observed during the high-speed inflow (Ma=1.7) ignition start-up, which does not appear in the low-speed inflow (Ma=1.4) ignition process.
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