Numerical Study on Stall Flutter of A Compressor Cascade (2nd Report, Relationship between Unsteady Aerodynamic Characteristics of Oscillating Blades and Rotating Stall)

摘要

Stall flutter of a compressor cascade is studied by numerical analysis of the unsteady separated flow around the blades oscillating in a torsional mode. When the cascade operates at a stalling inlet flow angle, the unsteady flow behavior varies according to the relationship between the phase propagation velocity of the blade oscillation and the propagation velocity of rotating stall. The propagation of rotating stall is synchronized with or entrained by the blade motion and becomes very regular when the both propagation velocities are close to each other. The oscillating blades are subjected to intense flutter excitation when the synchronization occurs. On the contrary, the rotating stall propagates regularly regardless of the blade oscillation when the both propagation velocities are largely different from each other. The propagation of rotating stall becomes irregular under the influence of the blade oscillation when the difference of the propagation velocities is in between. The flutter excitation of the blades never occurs in the latter two flow conditions.