Improved Aerodynamic-Ramp Injector in Supersonic Flow

An experimental study was performed in the Virginia Polytechnic Institute and State University supersonic wind tunnel on a simplified and revised multiport aerodynamic-ramp injector array in a supersonic flow. The new aerodynamic-ramp injector consisted of four flush-walled holes, in contrast to the original nine-hole versions. For comparison, a single, low downstream-angled circular injector hole was examined. Test conditions included sonic air injection into a Mach 2.4 air cross stream with an average Reynolds number of 4.2 x 10 7 /m at jet-to-freestream momentum flux ratios from 1.1 to 3.3. Shadowgraphs and surface oil-flow visualization pictures were taken in the vicinity of the injectors to gain a qualitative assessment of the injector flowfields. Quantitative measurements of the pressure field on the surface near injectors and in a cross-stream plane downstream were conducted using pressure-sensitive paint and pitot/cone-static probes, respectively. The mixing characteristics of the injectors at three downstream stations were quantified using total temperature probes and a combination of heated and unheated injected air profiles to generate a mixing analog to concentration. Results showed that the aerodynamic-ramp mixed faster and had a larger plume area than the single-hole injector, while sustaining somewhat higher pressure losses due to increased blockage and a higher downstream-angled injector arrangement.

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