Comparison of Planar and Axisymmetric Flowpaths for Hydrogen Fueled (invited)

A terse historical summary of the very early work on supersonic combustion serves as the foundation for the argument that contemporary designers of hypersonic vehicles need to broaden their perspective beyond planar inlet configurations. To support the argument, a large family of inlets that are streamline traced from truncated Busemann flowfields are described. The computational procedures for obtaining the geometry of the compression surfaces are outlined. Metrics are introduced that are intended to provide an equitable basis for comparing the performance and operability of engines that have planar or inward turning inlet flowfields. Although, there are many additional distinctive characteristics between the two families of engine flowpaths, emphasis in this paper is focused on the large differences in surface areas and the concomitant viscous losses. The large impact of the shape of the cross section of the compressed flow leads to higher pressure rises that must be sustained in the engine isolator as well as the lower engine specific impulse in the planar designs.