Startability of truncated hypersonic wavecatcher intake

Abstract

This paper compares the self-starting ability of an unmodified modular Busemann intake (UBI), with a modified Busemann-based intake (MBI), where the modification is designed to promote intake starting. Both intakes are designed on the wavecatching principle to allow overboard spillage during the starting process. Both intakes are designed for a flight Mach number of 5.19. The theoretical exit Mach number of both intakes is 3.11. Unsteady CFD calculations show that the UBI does not start spontaneously at any flight Mach number. The MBI does start at Mach 3.1. For the MBI Busemann flow, the theoretical exit total pressure recovery is 0.937 with a startability index Si=(Ae−Ais)/(Akan−Ais) of 1.507. The modified internal contraction results in an exit flow with an elliptic oblique shock and some non-uniformity. The paper presents, a) how an intake is truncated, b) how streamline tracing is applied to design a wavecatcher flowpath, and c) how the strong shock principle is applied to design a startable intake.