A Design Method for Three-Dimensional Scramjet Nozzles with Shape Transition

A design method for three-dimensional shape transition scramjet nozzles is introduced. The method employs streamline tracing to capture the properties of an axisymmetric thrust nozzle in a complex three-dimensional shape that allows for airframe integration and side-by-side mounting of scramjet engine modules. A contoured centerbody is added to an established maximum thrust nozzle and used as the axisymmetric parent flowfield. This allows for tailoring the shape of the nozzle to a variety of vehicle geometries while at the same time eliminating drag producing surfaces traditionally encountered in this type of nozzle. The design procedure is described and applied to the design of a nozzle for a Mach 12 scramjet engine at an off-design condition. An inviscid computational fluid dynamics analysis of the nozzle is used to analyze the accuracy of the capture of the parent flowfield's properties. It is found that despite the shape transition the nozzle is able to reproduce the interior flow of the axisymmetric flowfield.