Starting Processes of High Contraction Ratio Scramjet Inlets

摘要

An experimental campaign was undertaken at the Von Karman Institute, Belgium, aimed at investigating the sliding doors inlet starting mechanism for a hypersonic scramjet inlet. This campaign provides the first step upon a much larger inlet starting investigation, with the results providing a backbone for comparison to future 2D and 3D transient RANS numerical studies. A scaled 2D representation of the SCRAMSPACE-I geometry was constructed, with two steel 3.2mm thick doors extending upstream from the inlet leading edge at an angle of 20 degrees. After achieving steady flow conditions, the doors were then retracted via a pneumatic piston and cabling system, with the resulting flow phenomena captured via visualization as well as quantitative instrumentation. The test campaign was undertaken in the H3 Wind Tunnel Facility, which provided a jet at Mach 6 at various reservoir pressures, with variance in Reynolds number used to simulate changing altitude conditions. Due to limitations with regards to tunnel blockage and diffuser placement, a scaling factor of 5.1 was applied to the model geometry proportionally in both the x and y directions. Successful inlet starting was achieved at conditions simulating flight at an altitude of approximately 29 km. Schlieren visualization techniques were employed, showing that supersonic conditions were indeed obtained in the inlet for approximately 32 flow lengths. Senflex thin film arrays, located on the inner surfaces of the inlet, captured the transient heat flux progression at different locations along the inlet. These profiles accurately captured the phenomena observed via the Schlieren imaging, in particular the propagation of shock structures into the inlet during the inlet starting procedure. Stanton number distributions along both arrays were extracted and showed a close comparison to those expected from numerical simulations reconstructed test flow conditions, which lends credibility to the integrity of the heat flux results.