Experimental investigation of a 3d stream-traced air-inlet for a scramjet engine

Abstract

A model of a scramjet inlet was investigated experimentally in the hypersonic wind tunnel H2K of DLR in Cologne. Test were carried out at four different Mach numbers between M∞ = 5.3 and M∞ = 8.7, and at Reynolds numbers between Re = 1.7·106 and Re = 10.1·106 (reference length lref = 0.532m). The angle of attack was varied from α = -2° to α = 2°, and the sideslip angle was varied from β = 0° to β = 2° in between different test runs. The internal contraction ratio of the inlet was varied between I = 1.17 and I = 1.52 by the use of cowl inserts that changed the position of the cowls leading edge. Tests with an optional passive bleed system were performed, too. For all tests, the inlet model was connected to a throttle device that allowed varying the back pressure during the test run in order to record performance mappings. Next to simulating the back-pressure, the throttle was used to measure the captured mass flow. Further information was gathered by 37 static pressure ports distributed over the surface of the inlet and three Pitot pressure probes located in the inlet exit plane. Schlieren visualisation was used to analyse the external flow field. The tests showed that reliable inlet starting was only observed for the lowest internal contraction ratio, i.e. with the most swept-back leading edge of the cowl. For this configuration reliable, robust operation of the inlet was observed at on- and off-design conditions. Further on, it was shown that the inlet’s performance fulfils the design requirements.