Aerodynamic Performance Analysis Of Scramjet Isolator Under Asymmetric Supersonic Flow

In order to simulate the actual flowfield at the exit of supersonic/hypersonic inlet, the flow in scramjet isolator is investigated under asymmetric incoming flow. A wind tunnel is designed under asymmetric incoming flow and the compression fields in the isolator have been investigated using wall static and pitot pressure measurements, schlieren photography. Three incoming Mach numbers are considered, Mach 1.5, Mach 1.8 and Mach 2. To understand further the test data, the numerical simulations are performed with the Reynolds-averaged Navier-Stokes solver using the SST k ?ω turbulence model. The flow characteristics under asymmetric incoming flow are compared with that under symmetric incoming flow. The studies on the design method and length reduction of the isolator under asymmetric incoming flow are conducted. In the end, the geometric effects of cross-sectional shape on shock train in constant area isolators are analyzed. The results indicate that the asymmetric velocity distribution at isolator entrance induces significant asymmetric shock structure in isolator and non-uniform flowfield at the isolator exit. The increase of the asymmetry of the flow at isolator entrance will lead to the increase of the shock train length in isolator for a given pressure ratio. Based on an analysis of flow asymmetry effect at isolator entrance on shock train length, a modified correlation is proposed to calculate the length of shock train. The predicted results of the proposed correlation show good agreement with experimental results. By using the curve spacer in isolator, the overall length of the isolator could be reduced by 33 per cent without loss in static and total pressure recovery when the lower wall boundary layer thickness δ/Η is equal to 0.24 and the upper wall boundary layer thickness δ/Η is zero at the isolator entrance. For those non-axisymmetric engine flowpaths of airbreathing vehicles, the octangular isolator is a good choice, which reduces the isolator length without the increase of total pressure loss. The octagon cross section reduces successfully the low-momentum flow area in the corners found in the rectangular cross section.