Demonstration of mode transition in a scramjet combustor

Direct-connect combustor hardware has been assembled at the Avery Propulsion Research Laboratory (APRL) of the Johns Hopkins University Applied Physics Laboratory (JHU/APL) to investigate a hydrogen-fueled scramjet combustor. The test hardware was designed to perform tests at simulated Mach 5 to Mach 8 flight conditions. This is done using a combustion heater with H2 fuel and makeup O2. The air, H2 and O2 flow rates are all supplied through computer-controlled digital valves. This system allows rapid changes in conditions and very steady flow rates can be maintained throughout the test. Recently, tests were performed in which the flow rates were systematically varied during the test to simulate an acceleration from M = 5.9 to 6.2. During this acceleration the fuel-air equivalence ratio was held constant and the combustor transitioned from a dual mode ramjet with a precombustion shock system creating subsonic flow at the injection plane, to a scramjet with no precombustion shock system. The results of these tests are presented along with descriptions of the hardware and control systems.