Numerical investigation of back pressure and free-stream effects on a mixed compression inlet performance

Inlet performance has an important role in the operation of air-breathing propulsion systems. In this study, performance of a supersonic axisymmetric mixedcompression inlet in the supercritical operating condition is numerically studied. The eects of free-stream Mach number and engine-face pressure on performance parameters, including mass ow ratio, drag coecient, total pressure recovery, and ow distortion, are investigated. For this sake, a multi-block density-based nite volume CFD code is developed, and Reynolds-averaged Navier-Stokes equations with Spalart-Allmaras oneequation turbulence model are employed. The code is validated by comparing numerical results against other computational results and experimental data for two test cases of inviscid ow in a two-dimensional mixed-compression inlet and ow in an external compression inlet. Finally, the code is utilized for the investigation of a specic 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 the decrease in total pressure recovery and drag coecient, while mass ow ratio and ow distortion increase. The eects of engine-face pressure on performance parameters showed that by increasing the engine-face pressure, mass ow ratio and drag coecient remain constant, while total pressure recovery increases and ow distortion decreases