Holographic Measurements and Theoretical Predictions of the Unsteady Flow in a Transonic Annular Cascade

Abstract

A series of measurements have been made on a transonic annular cascade. The cascade which represents the tip section of a compressor fan blade has an inlet Mach number of 1.18. By the use of external vibrators it is possible to vibrate the blades independently in torsion simulating different interblade phase angles in order to gain an understanding of shock movement and blade loading. The results presented are made over interblade phase angles of 180 and 135 deg at a blade frequency parameter of 0.1, based on chord. The holographic data obtained shows detail of shock movement during the cycle using a miniature holocamera located within the hub of the cascade. Unsteady sidewall pressure measurements have also been obtained over the vibration cycle. The data obtained have been compared with finite element calculations.