Arrangement of Rocket Engine Location in a Combined Cycle Engine

Abstract

To avoid the severe thermal load within the embeddedly configured Rocket-Based Combined Cycle engine, we arranged the rocket engine location in the present study, that is, the rocket engine was separately mounted for the scramjet flowpath. The rocket engine was taken out from the scramjet flowpath and located on the ramp wall of the scramjet external nozzle. In this case, the ramp wall acted as the additional nozzle in the spike nozzle manner for the rocket internal nozzle. One-dimen-sional analysis showed that there was an optimal expansion ratio favorable for the scramjet external nozzle. Subsequently, more complex analysis was partially performed using Method-of-Characteristics based two-dimensional wave model with some novel modifications, which can express the pressure mismatching between the exhaust and the ambient flows. The two-dimensional analysis showed that thrust production within the scramjet external nozzle could become much lower due to impingement of the cowl lip expansion waves resulting from the pressure mismatching. This pressure change also sizably reduced the thrust performance of the rocket spike nozzle. It was, however, also demonstrated that presently analyzed nozzle system has great potential to drastically improve its thrust performance by means of controlling the impingement of the cowl lip expansion waves.