Comparison of Physical and Aerodynamic Ramps as Fuel Injectors in Supersonic Flow

An experimental investigation was conducted to compare the supersonic mixing performance of a novel flush-wall aerodynamic ramp injector with that of a physical ramp injector. The aerodynamic ramp injector consists of nine flush-wall jets arranged to produce fuel-vortex interactions for mixing enhancement in a supersonic crossflow. Test conditions included a Mach 2.0 crossflow of air with a Reynolds number of 3.63 x 10 exp 7 per meter and helium injection with jet-to-freestream momentum flux ratios of 1.0 and 2.0. Conventional probing techniques, including species composition sampling, were employed to interrogate the flow field at several downstream locations. Results show that, with increasing jet momentum, the aeroramp exhibited a significant increase in fuel penetration, whereas the physical ramp showed no discernible change. The near-field mixing of the aeroramp was superior to that of the physical ramp; however, the physical ramp reaches a fully mixed condition at approximately half the distance of the aeroramp. As the jet momentum was increased, the far-field mixing performance of the aeroramp approached that of the physical ramp. In all cases the total pressure loss incurred with the aeroramp was less than that caused by the physical ramp. For both injectors the total pressure loss decreased with increasing jet momentum. It was concluded that, although physical ramps may provide better far-field mixing, properly designed flush-wall injection can provide comparable mixing performance while avoiding the practical problems associated with an intrusive geometry in a scram jet combustor. (Author)