Analysis of Proposed Fully Internal Compression Geometry for an RBCC Engine

A proposed fully internal compression geometry for rocket based combined cycle (RBCC) engine, STEPER (Space Transportation Engine Prototype for Engineering Research), was investigated numerically in this paper. The Steper-engine has been designed to power a reusable launch vehicle that may take-off horizontally, accelerate to Mach 2, sustain supersonic air-breathing combustion to Mach 10 while ascending to 50 km and then transition to full rocket propulsion to enter low earth orbit. The proposed engine geometry replaces the alternative conical center-body and supporting struts with a quasi-stationary upper and lower compression ramps. A cluster of thruster nozzles was embedded inside the ramp and provide thrust to the engine with additional fuel existing at the nozzle exit. The proposed geometry eases the problem of cooling hard to reach cavities. This design geometry was investigated numerically. Both perfect gas and finite rate chemistry analysis were performed. Results indicated that the emanating oblique shock waves produced by the upper and lower compression ramps intersect and the reflecting shocks do not reach the wall of the combustor but rather downstream. This effect allows the formation of two distinct regions that can be considered the core region and the surrounding flow region. The core region has higher pressure and higher temperature than the surrounding region. Therefore providing some reduction to the thermal loads to the inner walls.