The flowfield in the nozzle exhaust of a vertical strut injected scramjet is studied in this thesis with emphasis on the prediction of thrust. An analytical model based on the physical processes expected to dominate the flow structure is presented. The distinctive feature of this model is the interaction between the developing vertical fuel jet and the horizontal swept expansion fan from the convex corner of the nozzle exhaust. This feature is noted to be similar to a swept expansion fan-boundary layer interaction.
Both the vertical strut injected nozzle exhaust flow and the swept expansion fan-boundary layer interaction are modelled in this thesis to consist of two separate processes. The first is the expansion and turning of the vertical fuel jet or the supersonic boundary layer by a swept expansion. It was found that during this interaction the jet or layer are turned more than the surrounding stream due to their Mach no. deficit relative to this stream.
The second process is the constraint of this jet or layer over-turning by the scramjet thrust surface or the boundary layer interaction expansion wedge. It is expected that the jet or layer will bulge near their respective constraining surfaces, deflecting surrounding streamlines, and hence incurring a pressure rise. This is expected to be the dominant thrust producing mechanism in a scramjet of this configuration.
A quantitative analytical procedure based on these processes is presented to calculate the pressure distribution on the scramjet thrust surface or the boundary layer interaction expansion wedge. The integration of this pressure distribution supplies a first order estimate of the thrust produced in a vertical strut injected scramjet.
To validate the flow model a series of experiments was conducted in a supersonic blowdown tunnel facility at the Mechanical Engineering Department, Queensland University, on swept expansion fan-boundary layer interactions. The measured pressure distributions on the expansion wedge in these experiments are presented in this thesis. These distributions correlate well with results produced using the model described. Given this correlation, the model is considered to be an accurate representation of the flow structure present in a swept expansion-boundary layer interaction. It is also considered to be an accurate model of the dominant feature in a vertical strut injected scramjet nozzle exhaust flow.