Performance of a Rocket-Ramjet Combined-Cycle Engine Model under Ramjet-Mode Operations

A rocket-ramjet combined cycle engine model, embedding twin rocket chamber on top wall side of a scramjet flow-pass, was tested under ramjet- (dual-) mode operation at M6 flight conditions. The rocket chamber was driven with gaseous hydrogen and oxygen at nominal operation condition of 0.6 MPa in chamber pressure and 6.0 in mixture ratio. Gaseous hydrogen was also injected through injector orifices within the ‘ramjet’ combustor to pressurize the combustor. A simple, one-dimensional calculation was conducted based on wall pressure measurement to evaluate combustion mode and engine performance. Engine exhaust samplings as well as Pitot pressure measurements were conducted to evaluate the calculation results. Different combustion modes were observed, which were found to have sizable effects on the engine performance.