Experiment of Supersonic Air Intake Buzz

概要

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For the purpose of examining supersonic intake instability, the authors have designed a supersonic wind tunnel of blow down type, in which the test section dimension is 200mm×180mm, its Mach number is 2.0,Reynolds number is about <10>^7 with reference length of air intake model diameter (60mm). By using this supersonic wind tunnel, experiments of inlet buzz are made, where the model is all external compression type and as parameters are used the throttle ratio (T.R.) and the center body position relative to the cowl lip (θ_A). The effect of attack angle (α) is also examined. They show that : 1) In the subcritical regime the unstationary phenomena occur and some characteristic frequencies are observed, where the transition from lower frequency to higher one happens according to the decrease of T.R., while the amplitude is fluctuated in rather arbitrary manner. 2) The motion of the bow shock wave corresponds fairly well to the pressure records, showing complicated behaviour of the boundary layer on the center body surface when it is expelled out from the cowl lip. In addition a theory is proposed in Appendix, where calculations are made to explain some buzz characteristics emphasizing two boundary conditions, the front shock wave and the rear choked exit.
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