Department of Aerospace Engineering, Indian Institute of Technology, Madras – 600036, India
Scramjet intake usually employs shock waves to reduce the flow velocity and increases the static pressure of the flow. However, this causes flow separation and multiple reflections of shock waves, which result in total pressure loss for the flow. This paper discusses the performance enhancement of scramjet intake through the implementation of a concavity along the cowl surface. The baseline intake model used here is the same as that reported in Emami et al. (1995) Two models with the concavities of depth 0.05 and 0.1 inches on cowl inner surface are numerically simulated at Mach number 4.03, and compared with the base model. An improvement in the performance is investigated in terms of total pressure and flow separation. Present study shows that a concavity on cowl surface reduces the flow separation on the ramp wall and increases the total pressure when compared to the base case. This is achieved by expansion fans produced at the beginning of the concavity. These expansion fans weaken the cowl lip shock and suppress the separation size. Further, it turns the shock waves along the flow, decreasing the number of shock wave reflections in the isolator. Thus, increase in total pressure at the exit of the isolator is observed. It is found that there is a marginal increase in Mach number for both the concavity cases without any change in mass flow rate. There was a minor flow distortion observed, which may be corrected by changing the isolator length. This study demonstrates the scope of overall improvement in scramjet engine performance by implementing concavity along the cowl surface.