Combined effects of ramp surface modification and throat shift on the performance of scramjet intakes

This numerical study discusses the performance enhancement of scramjet air intake model by a combination of ramp geometry modification and change in throat position. One of the scramjet intake models developed by Emami et al1 is used in this research as baseline model (B). Ramp surface angle is initially 11° in the baseline model. This angle is reduced by 3° after 1 in. flat length from ramp leading edge. This inclined surface is extended upto 4.92 in. and then connected to throat with 4 different locations. The effect of this change is to introduce an expansion fan and a compression in the ramp flow. The expansion fan weakens the ramp leading edge shock and curves it towards the cowl lip. Further, the cowl lip shock also turns more towards the flow direction and weakened. This reduces the shock wave boundary layer interaction on the ramp surface. Four different configurations namely TS1, TS2, TS3 and TS4 are numerically simulated. Except TS1 model which unstarted, reduction in flow separation to a great extent is noticed in other models. These modifications further increase total pressure recovery and mass capture. The only drawback appears to be the slightly higher Mach number in the flow. Thus this study exhibits the scope of overall improvement in scramjet engine performance by implementing a combination of both ramp geometry modification and change in throat position.