This paper presents the effect of cavity-based injection in an axisymmetric supersonic combustor using numerical investigation. An axisymmetric cavity-based angled and transverse injections in a circular scramjet combustor are studied. A three-dimensional Reynolds-averaged Navier−Stokes (RANS) equation along with the k-ω shear-stress transport (SST) turbulence model and species transport equations are considered for the reacting flow studies. The numerical results of the non-reacting flow studies are validated with the available experimental data and are in good agreement with it. The performance of the injection system is analyzed based on the parameters like wall pressures, combustion efficiency, and total pressure loss of the scramjet combustor. The transverse injection upstream of the cavity and at the bottom wall of the cavity in a supersonic flow field creates a strong shock train in the cavity region that enhances complete combustion of hydrogen-air in the cavity region compared to the cavity fore wall injection schemes. Eventually, the shock train in the flow field enhances the total pressure loss across the combustor. However, a marginal variation in the total pressure loss is observed between the injection schemes.