Experimental Investigation of Unsteady Aerodynamic Characteristics of Transonic Compressor Cascades

Abstract

To elucidate the unsteady aerodynamic characteristics of a transonic compressor cascade, test facilities are developed. A high-speed mechanical drive system is developed which provides controlled pitching oscillation of a blade in the linear cascade. A traverse unit with dual turntables is developed in order to survey the entire flow field around the cascade. Indirect pressure measurement techniques are applied to obtain the unsteady blade surface pressures when only one blade in the cascade is forced to vibrate. The effect of the change in attack angle of one blade in the cascade looks limited within the flow passages adjacent to the relevant blade. For capturing the high-speed periodic shock wave motion, an accurate photographing and image processing system is developed using a video camera with a moderate frame rate instead of using a high-speed video camera. The feasibility for generating successive pictures in one period whose frequency is up to 500 Hz is confirmed. Although the amplitude of shock wave displacement does not change much within the range of the present experiment, the phase lag relative to the blade oscillation reaches around π /2 as the blade oscillation frequency increases to 200 Hz.