Numerical Investigation of Back Pressure and Free-stream Effects on a Mixed Compression Inlet Performance

Abstract

Inlet Performance has an important role in the operation of air-breathing propulsion systems. In this study, performance of a supersonic axisymmetric mixed-compression inlet in the supercritical operating condition is numerically studied. The effects of free-stream Mach number and engine-face pressure on performance parameters, including mass flow ratio, drag coefficient, total pressure recovery, and flow distortion are investigated. To this sake, a multi-block density-based finite volume CFD code is developed and Reynolds-averaged Navier-Stokes equations with Spalart-Allmaras one-equation turbulence model is employed. The code is validated by comparing numerical results against other computational results and experimental data for two test cases of inviscid flow in a two-dimensional mixed-compression inlet and flow in an external compression inlet. Finally, the code is utilized for investigation of a specific supersonic mixed-compression inlet with the design Mach number of 2.0 and length to diameter ratio of 3.4. Results revealed that the increment of free-stream Mach number leads to decrease in total pressure recovery and drag coefficient, while mass flow ratio and flow distortion increase. The effects of engine-face pressure on performance parameters showed that by increasing the engine-face pressure, mass flow ratio and drag coefficient remain constant while total pressure recovery increases and flow distortion decreases.