Unsteady aerodynamic characteristics of annular cascade oscillating in transonic flow. 3rd Report. Low back-pressure supersonic compressor blade flutter.

Abstract

The low back pressure supersonic compressor blade flutter in the torsional mode were studied with a controlled-oscillating annular cascade test facility. The unsteady aerodynamic moment acting on an oscillating blade was measured with 18 pressure transducers on a blade surface, in 240 experimental cases which consist of reduced frequencies based on a half chord from 0.0375 to 0.547, 6 interblade phase angles and 5 inlet flow velocities from subsonic to supersonic. The region of unstall flutter occurrence and the significance of 3 parameters on aerodynamic instability were made clear, including the important role of unsteady pressure on the blade suction side upstream of the torsional axis for aerodynamic instability and the effect of shock wave movement due to blade oscillation on flutter.