CFD simulation of a rocket-ejector for an ejector-ramjet combined cycle engine

Abstract

Ejector-ramjet combined cycle engines have received increased attention as candidate for future reusable launch vehicle propulsion systems. Such engines use an ejector rocket during takeoff and low speed acceleration. In order to obtain more reliable performance estimations and to get a better understanding of the engine characteristics and sensitivities, a CFD study has been initiated using a commercial CPD code. The final target of the study is to enable a more accurate input for system analysis studies. In this paper the first stage of this CFD investigation is described. A simplified, rotational symmetric model of an ejector-rocket is analyzed. The computations have been performed in 3-dimensional space, using the k-6 turbulence model and a subset of Evans and Schexnayder's hydrogen-air model for the chemical reactions. The inflow conditions correspond to a vehicle flight speed of Mach 2.0 at an altitude of 11 km. Because short mixing lengths are required if an ejector is implemented into a real vehicle, the effect of forced mixing is assessed. For this purpose a lobed rocket nozzle is simulated. The results are compared with those obtained from a conventional conical rocket nozzle.