Effect of Boundary-layer Suction on the Performance of an Intake under Off-design Condition

Under off-design conditions, shock wave-boundary layer interaction (SWBLI) and large-scale separation within the intake become prominent, leading to significant decrease in aerodynamic performance. By introducing a boundary layer suction system, numerical calculations are used to investigate the variations in flow and performance, and to analyze the suction mechanism. Boundary layer suction effectively removes low kinetic energy fluid, reduces the size of the separation bubble size, relieves the pressure gradient, and transforms the bow shock at the inlet into an incident oblique shock. At the same time, the suction device can also increase the total pressure recovery ratio (TPR), and the captured mass flow ratio (CMFR), while reducing the distortion index (DI). In particular, different suction locations and numbers, as well as backpressures, affect the flow field differently. The S2 is key in controlling the cowl-incident shock wave and separating bubble. Its suction action can change the type of shock interaction at the inlet from λ-type to x-type. Therefore, the reasonable setting of suction holes can enhance the aerodynamic performance and operating stability of the intake by optimizing the internal shock wave system.