LAPCAT II intake starting tests

As part of the EU LAPCAT II programme, the University of Oxford tested and analysed a 1:100 scale Scramjet intake for starting capabilities. Tests were performed at a Mach 7 condition in the Oxford Gun Tunnel, with a unit Reynolds number of 20x106/m. The model was instrumented with 61 measurements of wall static pressure throughout the intake and isolator, 24 thin film heat transfer gauges on the end of the intake and start of the isolator and video Schlieren of the cowl closure region of the inlet. A comparison of the intake wall pressures showed that the LAPCAT MR2 intake exhibited higher intake pressures than the tests completed by DLR using the same geometry and flight condition. Analysis of the Schlieren and the pressure data has revealed that the most likely cause of the higher inlet pressures is a small separation that originates from the corner at the mid-plane of the intake. With a reduced exit area 25.4%, which is analogous to an increased back pressure from the combustor, a normal shock sits stable in the isolator. At extreme AoA (i.e. above +4°), the external part of intake shows a very low pressure as it is being processed by a Prandtl-Myer expansion, resulting in low pressure in the isolator with minimal external compression achieved. Testing showed that the intake was capable of self-starting across the range +4 degrees to -12 degrees AoA. This was observed through rapid start-unstart or buzz on the intake once a sufficient level of blockage was applied. Body wall pressure, body heat flux and crotch area Schlieren for various times throughout the inlet start/unstart/start process will be presented and discussed in the final paper. The presence of intake buzz confirms that this geometry is self-starting.