Pressure oscillations in multi-cavity scramjet combustor using kerosene fuel for hypersonic transport

The kerosene-fueled scramjet with multi-cavity combustor is a promising concept for hypersonic transport, but its combustor exhibits strong unsteady flow behavior with large pressure oscillations. The influence of shocks on pressure oscillations and the acoustic coupling between cavities remains unclear, posing challenges for preliminary design and optimization under ground-based test conditions. To address this issue, the present study investigates pressure oscillations under different equivalence ratios under both non-reacting and reacting flows using LES/RANS hybrid methods. The combustor features six cavities arranged in three groups, each containing two transverse cavities. Results show that the acoustic coupling between cavity groups varies with combustion and mainstream flow type. Additionally, under non-reacting flows, large-amplitude pressure oscillations are primarily driven by shock–vortex–acoustic interactions, and fuel injection can suppress oscillations up to an equivalence ratio threshold by introducing a vortex and acoustic propagation boundaries. Under reacting flows, large-amplitude pressure oscillations arise from complex interactions involving shocks, flames, vortices, and acoustics, with the equivalence ratio significantly dictating the mainstream flow type, which in turn affects the oscillation intensity. Notably, the supersonic–subsonic coexistence flow type produces the largest pressure oscillation amplitude, reaching up to 170%, which is detrimental for practical applications. These findings provide new insights into the mechanisms governing pressure oscillations in kerosene-fueled multi-cavity scramjets and offer guidance for the design of combustors with improved stability for hypersonic flight.