Study on Rocket-Based Combined-Cycle Engines

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Recently, rocket-based combined-cycle (RBCC) engines have been discussed more frequently because of their attractive characteristics, such as an increased payload-to-take-off-weight ratio and a higher specific impulse. In this study the ScramLACE (liquefied air cycle / supersonic-combustion ramjet) engine was chosen for the transatmospheric accelerating mode of the RBCC system to investigate the feasibility of using the LACE mode and the Scramjet mode combination with the RBCC system.An experimental study on cooling the heat exchanger by liquid hydrogen was conducted to validate a method of estimating the air liquefaction ratio, alpha, based on the study of corrugated-straight-fin heat exchangers. The results showed that the measurements of alpha are well coincident with the calculations obtained by this method of estimating alpha. Based on this method of estimating alpha, the relationship between alpha and the flight Mach number, M, was obtained using a parameter of the heat transfer … More area of the heat exchanger in order to evaluate the system performance of a basic model of the LASE system. From the results, it was clarified that changing a hydrogen supply line from LACE 1 to LACE 2 at a selected value of the flight Mach number is one of the most reasonable ways to achieve a high specific impulse during the LACE mode operation, M=1 to 5.An experiment of an air intake model during the LACE mode operation was performed using a supersonic wind tunnel to validate numerical results obtained from Navier-Stokes equations. It was found that this computational method has sufficient accuracy to evaluate the qualitative performance of the supersonic intake. Based on this method, characteristics of two types of the intake model were investigated.Effect of airframe integration on scramjet performance were calculated on the assumption of quasi-one-dimensional flow. Three different types of airframe integration were investigated. From the results, it was clarified that it is desirable for the engine to be integrated on the airframe paralleled to the airframe axis, as well as to have an inlet inhaling the air compressed by the shock wave from the nose of the airframe.The pseudo-shock waves in rectangular scramjet isolators with steps were investigated, When the front of the pseudo-shock waves first reached to the step, pressure at the first shock vibrated with the clear frequency peak of 320-480 Hz. Then the pseudo-shock waves propagated further upstream of the step, the pressure around the first shock vibrated with 100-200 Hz. From these results, it was found that these features in the rectangular duct with the step were caused by the recirculation right downstream of the step. Less