Numerical investigation on flame development and oscillations in strut-based supersonic combustor

To achieve sustainable combustion in scramjets, struts or cavities are typically introduced as flame holders, but they also contribute to complex combustion instabilities. This study employs a hybrid Large Eddy Simulation (LES) and Reynolds-Averaged Navier-Stokes (RANS) technique to investigate the German Aerospace Center’s (DLR) strut-based supersonic combustor, providing detailed insights into the combustion processes with a focus on the near-field flame development and overall combustion oscillations within the combustor. The high-resolution simulation reveals that two pairs of recirculation zones emerge behind the strut. The expansion of the main recirculation zone induces a forward movement of the high-temperature region, triggering auto-ignition and causing a flame reverse movement phenomenon. The interaction between turbulence and chemical reactions results in two types of reverse flame movement in the near-field region, collectively forming a complex flame-switching behavior to induce upstream combustion oscillations. The pressure oscillation frequencies in the near- and far-field regions are essentially identical and exhibit strong cross-correlation characteristics, suggesting a potential influence of near-field combustion oscillations on the far-field combustion oscillations.