Hypersonic wavecatcher intakes and variable-geometry turbine based combined cycle engines

A summary is presented of research progress in the design and technology of hypersonic air intakes and variable-geometry turbine based combined cycle (TBCC) intakes. Development of hypersonic intakes has passed through three geometry variations: 1) intakes with Prandtl-Meyer flow, terminating at planarly symmetric flat, oblique shocks and bounded by sidewalls, 2) the novel modular wavecatcher intakes, based on axial flow; 3) diverterless supersonic intakes, integrated with a bump surface to displace the boundary layer. We describe development of the design method of the axisymmetric wavecatcher intake, covering the direct streamline tracing technique and methods of intake flowpath morphing. We characterize intakes on the basis of the flow-related, meaningful concepts of turning, convergence and deflection to distinguish the different fundamental and characterizing flows that form an intake flowpath. These concepts closely relate to intake capability and efficiency and so can be identified and ascribed as contributing factors to performance. Still-outstanding design challenges are highlighted. Development of the variable-geometry TBCC intake is reviewed. Classified by spatial layout, the TBCC intake includes tandem and parallel (over/under) flow paths that can be divided further into internal and external over/under TBCC intakes. The virtues and critical technologies of various variable-geometry TBCC intakes are reviewed and summarized and the capabilities of the over/under TBCC with an axial-flow-based wavecatcher intake are highlighted.