Investigation on supersonic combustion heat release modes based on the HyShot Ⅱ combustor

A simulation study and analysis of the Hyshot II have been conducted based on the RANS. By analyzing the characteristics of the flow field, which is divided into pure air flow, mixing, and combustion regions. Further research was conducted on the contribution of these regions to heat release and the flame stabilization mechanisms. Along the flow direction, the volume percentage of pure air flow region decreases, the volume of the combustion region first increases and then decreases, while the mixing region increasing nearly linearly. Combustion region is classified into four distinct modes based on Mach number and flame index: supersonic premixed combustion, supersonic diffusion combustion, subsonic premixed combustion, and subsonic diffusion combustion. Quantitative analysis revealed that supersonic and subsonic premixed modes significantly lower volumetric percentages and heat release rates compared to supersonic and subsonic diffusion modes. This study therefore focuses on the two diffusion combustion modes. The subsonic diffusion combustion mode has the smallest volume but the highest heat release. The volume of subsonic diffusion combustion mode increases first and then decreases along the flow direction, but the heat release remains nearly constant. Supersonic diffusion combustion mode occupies the largest volumetric percentage, and although supersonic flow is not conducive to chemical reactions, its large volumetric percentage contributes to heat release. The supersonic diffusion combustion mode volume increases continuously along the flow direction, but the heat release continuously decreases. Combined with the Damkohler number and the streamline, the causes of the coronal high temperature heat release region at the top of the jet and the flame stabilization region are analyzed.