Research on supersonic combustion

Abstract

Introduction S OME qualifications to the pretentious nature of the title of this Paper are in order. Research in this context is applied, i.e., it is directed toward the design and development of devices. The devices are air breathing propulsion systems, wherein supersonic combustion is inherent or it provides an adjunct benefit. Principal applications of the former are manned hypersonic aircraft, transatmospheric accelerators, and missiles. Typical examples of the latter are external burning systems that sustain thrust or reduce drag when used in tandem with primary accelerator engines. This Paper is not at all representative of the complete body of the research on supersonic combustion. Instead, what is presented is primarily based on material with which the writer has had either direct involvement or a first-hand knowledge. It does not do justice to the exemplary works of many other investigators. Hopefully, this is somewhat rectified by the extensive list of references. The reader is encouraged to consult these manuscripts to obtain a more balanced perspective. This applied research must be viewed from the perspective of the engineer who is charged with expediting development and is in the need of design tools. Exact physics have frequently been abandoned to produce functional models. Much of the experimental verification upon which the models are based has been obtained in facilities which have known imperfections with respect to duplication of flight conditions. Moreover, compromises have been made in the analysis and interpretation of the experimental data, in part due to imperfect or incomplete diagnostic instrumentation, and in part due to a limited understanding of the underlying physics. An example that embodies all of these deficiencies would be a design model that is based on the use of integral techniques to describe combustion in supersonic flow from experiments conducted in an arc-heated tunnel.