Experimental Testing of a Hypersonic Inlet with Rectangular-to-Elliptical Shape Transition

Wind-tunnel testing of a hypersonic inlet with rectangular-to-elliptical shape transition has been conducted at Mach 6.2. These tests were performed to validate the use of a recently developed design methodology for fixed-geometry hypersonic inlets suitable for airframe integrated scramjets. Results indicated that flow features within the inlet were similar to design and that the inlet typically captured 96% of the available airflow. Typical mass-flow-weighted total pressure recoveries of 55% were obtained for compression ratios of 14.8 throughout the test program. Assessment of the inlet starting characteristics indicated that the inlet self-started at Mach 6.2 despite the fact that it had an internal contraction ratio well above the Kantrowitz limit (Kantrowitz, A,, and Donaldson, C., "Preliminary Investigation of Supersonic Diffusers," NACA WR L-713, 1945). These results demonstrate that high-performance, fixed-geometry inlets can be designed to combine a nearly rectangular capture with a smooth transition to an elliptical throat.