A design method for elliptical to rectangular shape transition nozzles

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 modified version of an established maximum thrust nozzle is used as the axisymmetric parent flowfield to allow for more accurate capture of its properties in and design flexibility for the shape transition nozzle. The design procedure is detailed and applied to design a nozzle for a Mach 12 scramjet engine at an off-design condition. An inviscid CFD analysis of the nozzle is used to analyse 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.