Experimental Characterization of Three-Dimensional Scramjet Inlet with Variable Internal Contraction

Abstract

A compact three-dimensional scramjet intake with a high compression ratio and a movable cowl as a starting device and for the adaption of the internal contraction to respective operating conditions was designed for a parabolic reentry flight experiment. In an extensive measurement campaign, conducted in a blowdown wind tunnel at Mach 7, the operational behavior of this inlet was characterized. The parameters investigated include internal contraction ratio, Reynolds number, angle of attack, and angle of yaw, and the starting behavior was examined. Static and total pressure ratios and mass capture ratios were used to evaluate the performance of the inlet and throttle curves to determine the operational limits. The flowfield was studied by schlieren images, wall pressure distributions, and Mach number profiles in the interface of the isolator and combustion chamber, which were determined with a pressure measurement rake with static and pitot pressure probes. The flow on the external ramp was analyzed by infrared thermography. The inlet showed good performance regarding compression and efficiency and proved to be quite robust at various flight angles. The performance tended to improve, and the inlet operated more stably with increasing internal contraction, with the most important factor being whether the inlet leading-edge shock was captured by the cowl.