The performance of a supersonic mixed compression air intake has been investigated experimentally. The intake is of axisymmetric one and has been designed for a free stream Mach number of 2.0. The present work has two main goals, first to investigate the performance of the intake without boundary layer bleed at design and at off-design conditions and second to study the effects of a bleed slot on the intake performance. The intake has been tested at free stream Mach numbers of 1.8, 2.0, and 2.2 and at zero degrees angle of attack. Total pressure recovery, mass flow ratio, and flow distortion have been selected to assess the intake performance. The bleed slot is located upstream of the intake throat perpendicular to the compression ramp surface. The suction is applied by the natural pressure difference between the entrance and the exit faces of the bleed duct. Results show that applying the boundary layer suction upstream of the intake throat can considerably improve the intake performance at its design and off-design conditions while it does not affect the intake mass flow rate.

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The performance and the buzz onset of a supersonic mixed-compression axisymmetric intake are experimentally investigated. Effects of the slot bleed position, angle, and width on the intake performance and on the buzz initiation at three different Mach numbers of 1.8, 2.0, and 2.2 and at a zero degree angle of attack are studied. The intake performance is assessed using the total pressure recovery, mass flow ratio, flow distortion, and bleed mass flow ratio. The results show that applying the bleed at a position near the intake entrance and reducing the bleed entrance slant angle and width all improve the intake performance considerably. Moreover, these parameters postpone the buzz onset. In addition, it is found that the vertical position of the intersection point of the barrier and normal shocks plays an important role in the intake pressure recovery.

A computational fluid dynamics code was developed to compute the flow inside and around a supersonic external compression axisymmetric intake. The code solves the Reynolds-averaged Navier–Stokes equations using an explicit finite volume method in a structured grid and uses the Baldwin–Lomax algebraic model to compute the turbulent viscosity coefficient. Experiments were performed to validate the predicted results and good agreements are achieved. In the next part of the research, a parametric study was undertaken using the designed base case at a constant Mach number of 2 and at 0° angle of attack. The effects of various important parameters such as free stream Mach number, spike deflection angle, and back pressure ratio on the total pressure recovery, mass flow ratio, flow distortion, and drag coefficient of the intake were then numerically investigated. The results showed that when the spike deflection angle of the intake was changed from 28° (designed base case) to 30°, the intake drag coefficient was reduced up to 9%. In addition, the intake performance degraded for very low values of the back pressure ratio.

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