Numerical Analysis of Flame Flashback and Instability in Cavity-Stabilized Supersonic Combustion

Aimed at the phenomenon of flame flashback and low-frequency combustion oscillation in the scramjet combustor with equal straight cross sections, 3D simulations were conducted, with the hybrid RANS/LES method (delayed detached-eddy simulation, DDES) for turbulence modeling and the partially stirred reactor (PaSR) for turbulence-reaction interactions. The obtained entire combustion oscillation period is consistent with the low-frequency combustion oscillation phenomenon observed in the experiment. The low-frequency combustion oscillation period can be divided into 3 stages: the cavity-holding flame, the flame flashback, and the flame blowout. By analysis of the reacting flow field in different stages of the low-frequency combustion oscillation cycle, the possible formation mechanism of low-frequency combustion oscillations was summarized. The results show that, there is no choking in the combustion chamber during the whole low-frequency combustion oscillation period. The pressure rise induced by shock interaction and the heat released by combustion are the key factors for the formation of low-frequency combustion oscillations in the combustion chamber.