Effect of Rocket Exhaust Configurations on Ejector Performance in RBCC Engines

Abstract

The results of a study of several rocket-based combined cycle engine ejector flowfield configurations, those using a single rocket located along the axisymmetric axis and those incorporating an additional annular rocket located along the outer wall of the ejector are detailed. Steady-state solutions of the axisymmetric Favre averaged Navier-Stokes equations closed by the Wilcox k-w turbulence model (including the Wilcox dilatational dissipation correction) are obtained using WARP, a finite difference flow solver using the Yee-Roe flux limiting scheme. It is shown that by having 75% of the rocket exhaust enter the ejector through the annular rocket a compression ratio of nearly 2.5 can be achieved for the case where both the air and rocket exhaust mass flows are equal. It is also shown that the effectively mixed area using this configuration extends over the outer 95% of the ejector exit area. A grid convergence analysis shows the resulting total pressure increase to be conservative by approximately 10%. In addition, WARP's ability to simulate mixed subsonic/supersonic shear layers accurately with high convective Mach numbers is demonstrated through comparison with experimental data.