An Aero-thermodynamic Analysis of Idealized Scramjet Configurations

The dual mode scramjet is a promising air breathing engine concept that is capable of powering an aircraft in the Mach number range of 3 through 12. This paper describes the inverse design of a tip-to-tail dual mode ramjet-scramjet engine that is derived from the exact solution of 1D and Quasi-1D flow fields. Through the coupled use of the exact solutions of shock waves in an ideal gas, and the exact representations of planar and axisymmetric geometric shapes, a series of elementary configurations are developed and analyzed. The design process is accomplished through the use of specially developed compressible flow relationships, to manipulate and assemble elementary configurations into idealistic engine configurations. The elementary shapes of interest to this study include star-shaped leading edges, the caret-shaped inlets, cylindrical combustors, convergent and divergent nozzles, and plug nozzle after-bodies. An integral part of this research effort is the development of an engineering code that generates an engine configuration and analyzes its thrust characteristics. Further, the algorithms used to evaluate the resulting engine performance, such as its Isp, its thrust, T, and its maximum operating temperatures, are based on established engineering correlations. The outcome of this research is classified into two categories: (a) configuration design and assembly, (b) engine parameters identification and optimization. Potentially, the design analysis concepts proposed herein may lead to the discovery of engineering parameters, both geometric and aerodynamic, that positively influence the performance of the resulting scramjet configuration. In addition, potentially, the manipulation of these newly derived engineering parameters may lead to the creation of configurations with superior thrust, T, and Isp characteristics.