Effect of upstream injection on local flame intensity in a scramjet combustor fueled with liquid kerosene at Mach 4 flight condition

The intensity of the local flame generated by spark ignition was investigated in a scramjet combustor fueled with liquid kerosene under Ma 4 flight conditions. The study utilized wall pressure evolution and high-speed imaging during experiments to assess the local flame intensity. The rise in wall pressure near the aft edge of the cavity was found to be an indicator of local flame intensity, and the impact of upstream injection on the flame intensity was discussed. The results demonstrated that the dense spray resulting from upstream injection suppressed the local flame intensity. In particular, the spray in close proximity to the shear layer caused weakening of the local flame through evaporation. Additionally, the height of penetration increased with higher upstream injection pressure, leading to the dense spray being located further away from the shear layer flame and thereby strengthening the local flame intensity. Moreover, a larger injection distance marginally decreased the flame intensity due to the presence of additional spray near the wall. Conversely, injections with higher mass rates resulted in a weaker flame intensity as more spray was distributed into the cavity.