Aerodynamic Design Considerations for Biconic Supersonic Air Intakes Revisited

TL;DR

This paper revisits and refines the aerodynamic design principles for biconic supersonic air intakes, proposing smaller ramp angles, offset cowls, and shock modifications to improve performance and eliminate flow spillage.

Contribution

It introduces revised design guidelines including smaller cone angles, offset cowls, and shock configurations, enhancing intake efficiency and flow stability over traditional methods.

Findings

Offset cowls can prevent flow spillage without complex modifications.

Replacing normal shocks with oblique or Lambda shocks improves pressure recovery.

Design modifications are simple, cost-effective, and significantly enhance intake performance.

Abstract

Traditional design principles for determining the optimal intake ramp or cone angles, for ensuring no flow spillage at the intake cowl under design conditions, and for the form of the terminal shock in the intake duct are revisited. We show that it is preferable to select the ramp or cone angles to be somewhat smaller than that suggested by the Oswatitsch criterion. An offset cowl lip that slightly violates the shock-on-lip condition is found to be beneficial; in fact, an offset cowl can be arranged for conical intakes with no flow spillage at the cowl lip at all. Improvements to the total pressure recovery are seen when the terminal normal shock is replaced by a strong form of the oblique shock for two-dimensional ramp-type intakes, and with a Lambda shock in case of conical intakes. The necessary design modifications are simple and virtually cost-free. These results rewrite the ground rules for the aerodynamic design of supersonic intakes.