Numerical simulations were conducted to predict the ejector pumping performance of a rocket-ramjet combined-cycle engine under a take-off condition. The numerical simulations revealed that the suction airflow was chocked at the exit of the engine throat when the ejector rocket was driven by cold N 2 gas at the chamber pressure of 3 MPa. When the ejector-driving gas was changed from cold N 2 gas to hot combustion gas, the suction performance decreased remarkably. Mach contours in the engine

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... led that the rocket plume constricted when the driving gas was the hot combustion gas. The change of the area of the stream tube area seemed to induce the pressure rise in the duct and decreasing in the pumping performance. ( 110 )