Supersonic combustion on hydrogen fuel injection locations in a cavity-based combustor

Supersonic combustion experiments have been performed using three different open cavity based injectors with various combustor inlet and fuel flow conditions. Angled injection is located upstream of a cavity, parallel injection is on the front step, and rearward injection is on the rear ramp wall. Hydrogen fuel is injected through four injection ports. The model scramjet combustor installs in the T3 free-piston shock tunnel and there is no a spark ignition source. Planar laser-induced fluorescence on the hydroxyl radical and fast acting pressures are used to investigate the flow characteristics. Angled injection method has a relatively high fuel penetration height and enhances diffusion among the two gases. As the equivalence ratio increases, angled injection generates a weak bow shock in front of the injector and recirculation zone to hold the flame. Parallel and rearward injection methods shows similar flame structure at low equivalence ratio At high equivalence ratio, parallel injection shows a single lined flame according to cavity geometry in the vertical section however, for rearward injection of high equivalence ratio, the fuel, which is injected in the opposite direction of air inflow with high injection pressure, bumps against the cavity leading edge, and it enhances the fuel diffusion and enables an ignition. Pressure ratio of cavity of reacting flow regarding non-reacting flow is almost same. Behind x = 300 mm, averaged pressure ratios of low equivalence ratio are similar for all injection methods, however, rearward injection is lower than others by 5 %.