Exchange Inlet Design for Rocket-Based Combined-Cycle Engines

Abstract

A methodology is presented for generating an inlet containing an entrained flow surrounded by an annular flow of driving, supersonic gas. As the driving flow expands outward into an annular pattern, it maintains a circular throat area while allowing the entrained flow to be drawn toward the axisymmetric axis. The methodology accounts for both compressibility and viscous effects, and it can be scaled for a variety of operating conditions and driving gases. Designs are presented for the inlet to an example rocket-based combined-cycle engine based on both a kerosenefueled and a hydrogen-fueled rocket. Numerical results are presented, showing rocket exhaust patterns that contain uniform conditions over 75% of the annular exhaust area. The entrained air passage is also shown to have high total pressure recovery over the subsonic flight range. The predicted performance is shown to be within 10% of the numerical simulations over the range of conditions considered.