9. Concluding remarks

A review and summary is presented of hypersonic air intake technology highlighting design objectives, basic flows, airframe integration, flowpath modification and intake flow startability. Taylor-Maccoll equations and Busemann flow are presented as the basis for constructing modular Busemann intakes. The firstorder Taylor-Maccoll equations are recast with Mach number components as dependent variables. These equations illustrate the free-standing conical shock, the axisymmetric centered compression fan, characteristics, surface curvature and inflection point, surface pressure gradient, surface Mach number gradient and gradients at conical shock waves. A chart is presented for assessing the performance of the Busemann-flow-based intake on the basis of its capability to reduce Mach number and its efficiency as measured by total pressure recovery. Experimental results indicate that viscous effects cause the total pressure recovery to drop from near 1 to 0.5 for a Busemann intake at Mach 8 and 30 km flight altitude.

Wavecatching (streamline tracing), morphing and foreshortening, as attempts at conditioning and improving the performance of the basic Busemann intake flow, are presented to show that (a) wavecatching is a useful technique to create modular startable intakes; (b) morphing is useful in integrating the intake shape with other geometric requirements of the airframe and combustor; (c) foreshortening leads to minor gains in intake performance but large weight savings; (d) small amounts of leading edge blunting cause large changes in the intake's shock structure.

A novel, strong shock method is presented, that uses strong-shock boundary conditions for designing spontaneously startable, modular Busemann intakes of high performance. This analytical approach allows pre-determination of Busemann intake startability; offering great simplicity in the search for flowpath surface shapes that yield startable intakes with high compression, high efficiency and supersonic exit flows. This improved startability is made possible by the wavecatcher's ability to spill mass flow during external compression combined with the moderate contraction of the internal flowpath.

Busemann flow contains unique fluid mechanical features: (a) a flow passage from a uniform, high Mach number flow, to another uniform, lower Mach number flow; (b) internal, convergent flow with an inflected surface; (c) conical flow where high gradients are near the center line and milder gradients are at the walls; (d) an axisymmetric and conically symmetric centered compression fan; (e) a freestanding conical shock, bounding irrotational flow; (f) the last two features combining to preserve conical flow throughout. These are unique and fortuitous virtues, being significant in making the Busemann streamtube and its flow characteristics useful as a basis for designing high performance air intakes for hypersonic airbreathing engines.

Author details

Ryerson University, Toronto, ON, Canada

The Busemann Air Intake for Hypersonic Speeds DOI: http://dx.doi.org/10.5772/intechopen.82736

provided the original work is properly cited.

\*Address all correspondence to: smolder@ryerson.ca

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Sannu Mölder

109
