Testing of a sub-scale scramjet research engine model was carried out in the March 6 Ramjet Testing of a sub-scale scramjet research engine model was carried out in the March 6 Ramjet Engine Test Facility of the National Aerospace Laboratory, Kakuda Research Center. By attaching a Engine Test Facility of the National Aerospace Laboratory, Kakuda Research Center. By attaching a short strut on the top wall, intensive combustion with high combustion efficiency was attained, and short strut on the top wall, intensive combustion with high combustion efficiency was attained, and the engine-produced thrust canceled the drag. The flame was held in the low-velocity region around the engine-produced thrust canceled the drag. The flame was held in the low-velocity region around the step, even after the ignitors had been turned off. When the fuel flow rate was small, there was a the step, even after the ignitors had been turned off. When the fuel flow rate was small, there was a different combustion mode with weak combustion and little thrust. Tangential injection of fuel intendifferent combustion mode with weak combustion and little thrust. Tangential injection of fuel intensive combution. sive combution.

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Two-stream flow model of ejector including heat and mass transfer was constructed by the comparison of the numerical simulations in the rocket-ramjet combined-cycle engine driven three different rocket gas; cold N2 gas, hot combustion gas and it within excess H2. The analysis of the ejector revealed that the heat and mass transfer from hot rocket plume with supersonic speed to cold airflow induced area change (expansion) of the airflow stream tube and the pressure rise in the constant-area section at the downstream of the rocket base. This pressure rise reduced the pumping performance of the ejector. To absorb the expansion of the airflow, the flowpath was changed from the constant area to the diverging area at the downstream of the rocket base. The numerical simulation in the modified engine demonstrated that the diverging-area section at the downstream of the rocket base improved the pumping performance.