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

Abstract

Aimed at the phenomenon of flame flashback and low⁃frequency combustion oscillation in the scram⁃ jet 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 os⁃ cillation 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 combus⁃ tion 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.