Studies of Inlet Distortion in a Direct-Connect Axisymmetric Scramjet Isolator

Abstract

Direct-connect wind-tunnel facilities that produce uniform flow entering the test section are generally used for scramjet-component (isolator/combustor) studies. In freejet experiments and flight tests, however, air enters the engine through an inlet, and flow entering the isolator and combustor is typically distorted. The distortion effects can include nonuniform boundary-layer thicknesses on the walls and relatively strong oblique shock waves. This research focuses on the effects of inlet distortion on a round scramjet isolator. A numerical study was performed using various distortion devices, including ramps, injector ports, and injector slots, that were placed downstream of the direct-connect facility nozzle to simulate a distorted flowfield from a prescribed inlet. The computational results provided a methodology for simulating flow distortion in direct-connect testing. Based on the numerical findings, experimental testing was conducted in the supersonic wind-tunnel facility to validate the numerical results and determine the impact of flow distortion. In addition, this paper focuses on design, fabrication, and execution of flow-distortion experiments. Air injection in the distortion section was used to create the flow distortion, and shock angle increases with the injection flow. Comparisons of wall pressure, exit flow profiles, and shock-holding capability are made from the experimental and numerical results. Good agreement between these data on wall pressures and flow profiles was found.