Experimental Testing of an Airframe Integrated 3-D Scramjet at True Mach 10 Flight Conditions

Free-jet experiments have been conducted in a shock tunnel at Mach 10 with a small airframe-integrated three-dimensional scramjet engine. The goal of the investigation was to examine the influence of airframe integration on the engine operation. The tests were conducted at a condition replicating flight at Mach 10.4 and a dynamic pressure of 48 kPa. The internal flowpath featured a rectangular-to-elliptical shape transition (REST) inlet designed for flight at Mach 12, an elliptical combustor with a constant area and diverging section, and a three-dimensional nozzle. This flowpath was integrated with a forebody and streamlined external geometry similar to what would be expected on a flight vehicle. Gaseous hydrogen fuel was injected either through portholes on the inlet, or a combination of inlet injection with a series of portholes behind a rearward facing step at the combustor entrance. Both fuel injection schemes produced robust combustion without the use of ignition aids. Comparison with tests of a three-times scale engine with a truncated forebody indicate that airframe integration and smaller scale led to a slightly reduced pressure rise. However, the core aspects of the engine characteristics remained unchanged.