Starting Characteristics of Curved Compression Ramp Air Intakes with Overboard Spillage

Abstract

An analytical framework is presented here for estimating the limiting area contraction for a family of curved compression ramp (CCR) supersonic air intakes with self-starting capability via overboard spillage. Flow compression in CCR intakes occurs through a combination of a curved ramp shock wave and a series of compression waves. In general, such a combination offers the best features of the canonical air intake families. That is, pressure recovery in CCR intakes is better than simple ramp (planar ramp) air intakes, and pressure ratios in CCR intakes are better than Prandtl–Mayer air intakes. A modified Kantrowitz criterion for startability is proposed to accommodate the nonuniform Mach number distribution in the cross-stream direction at the intake throat that is inevitably realized in CCR air intakes. The starting characteristics of different design configurations that fall within the family of CCR air intakes are analyzed, and a comparison is made with planar ramp and Prandtl–Meyer intakes. Inviscid flow numerical experiments of intake starting were carried out to successfully verify the starting characteristics predicted by the analytical model. The analytical framework presented here can be employed as a general tool for optimizing air intake design based on startability, efficiency, and other performance considerations.