Role of sock wave in aerodynamic instability in annular cascade. (1st Report, Transonic turbine cascade oscillating in torsional mode).

Abstract

Effects attributable to shock wave movement upon cascade flutter were studied experimentally, using 13 miniature pressure transducers aligned at 3% chord length intervals on the blade surface of an transonic turbine cascade. The experimental range was for 4 outlet Mach numbers, 4 interblade phase angles and reduced frequencies from 0.028 to 0.330, based on half chord. It was made clear that the shock wave movement strongly affects the occurrence of cascade flutter. The effect was remarkably dependent on an interblade phase angle, not on a reduced frequency or an outlet Mach number. It acts as a blade vibration exciter or a damper. The pressure ratio of the time-variant pressure to the static pressure rise due to the shock wave on the blade surface was about 30%.