The research uses CFD to investigate the internal flow of two hypersonic engine inlets: the Hypersonic Research Engine (HRE), a dual-mode ramjet/scramjet, and the Sustained Hypersonic Flight Experiment (SHyFE), a ramjet developed by QinetiQ. Various interactions are considered, namely shock-expansion, shock-shock and shock-boundary layer interactions. To isolate the different interactions, both inviscid and viscous turbulent computations are considered. For the HRE, axisymmetric computations are performed at Mach numbers of 5, 6 and 7, consistent with ground testing conditions used by NASA. The HRE was designed to cruise at a range of Mach numbers; for a given set of freestream flow conditions, dramatically different internal flow characteristics have been found depending on whether the engine arrived at the flow conditions through either acceleration or deceleration. CFD surface data and throat profiles have been compared to, and agree well with, experimental data obtained by. NASA. 'I\vo flow conditions are investigated for the SHyFE inlet. Firstly, the self-starting characteristics of the SHyFE intake are examined, where the effect of increased internal compression is considered. The findings show undesirable wave interactions, which lead to flow non-uniformities, and decreased shock stabilization properties have adverse effects on the performance of the engine. Secondly, the effect of freestream incidence on the inlet is examined..The SHyFE engine is designed to cruise at a mean incidence of between 2???????? and 3????????, however, it is conceivable that the engine will, at times, operate at 5????????. Fully three dimensional computations are performed at an angle of attack of 5???????? where the resulting flows show that Mach reflections on the inner surface of the cowl can lead to shock-detachment, as well as showing that shock-boundary layer interactions on the centrebody can cause centrebody flow separation which can unstart the engine. By aul1ing a rear-ward fdl-~l1b btep tU the CClltfCUUtly geometry, the centrebody separation is shown to be stabilised and does not unstart the engine. CFD results are compared to, and agree with, experimental data produced externally by QinetiQ, namely schlieren and surface pressure data.Imperial Users onl
