A large-scale, variable-geometry inlet model with a design Mach number of 3.0 was tested at Mach numbers from 1.55 to 3.2. Variable features of the inlet for off-design operation are an adjustable-height ramp system and a translating cowl. This report presents experimental results for a diffuser and boundary-layer bleed configuration which was optimized at the design Mach number. Overall performance was high with throat-mounted vortex generators, which were effective in reducing flow distortion in the subsonic diffuser at the higher Mach numbers.

A numerical investigation of a fixed geometry mixed-compression scramjet inlet is presented in this paper to illustrate the compression process and flow interactions of a hypersonic inlet prior to supersonic combustion. Through the use of an AUSM (Advection Upstream Splitting Method) differencing scheme, applied for both inviscid and turbulent scenarios, this analysis explores the complex phenomena associated with hypersonic flows such as shock-shock and shock-boundary layer interactions. Particular attention is placed in the vicinity of the inlet throat area, where such interactions may cause flow separation and give rise to further complications such as inlet unstart. The inlet geometry is a modified version of the hydrogen-fueled axisymmetric scramjet used on the Hypersonic Flying Laboratory (HFL) named "Kholod", designed and tested by NASA and the Central Institute of Aviation Motors (CIAM) on February 12, 1998. The inlet is computationally solved using the commercial software FLUENT 6.3 and the computational grids were generated using the grid generator GAMBIT 2.4.6. Grid nodes were clustered near the critical flow path areas in order to accurately capture any viscous interactions within the flow field. Solutions presented in this paper assumed free stream properties equivalent to an altitude of 10,000 meters, at 0 degree angle of attack, with Mach numbers of 5, 7, and 9, all solved through both inviscid and turbulent models.