Resonance Oscillation Response of Turbine Rotor Cascade to Viscous Wakes of Upstream Nozzle Cascade : Resonance Amplitude in Bending-Torsion Coupled Oscillation

Abstract

Forced oscillation response of turbine rotor cascade to upstream viscous wakes, which are regarded as inviscid sinusoidal gust in the analysis, are studied. Taking the effects of the rotor steady loading on unsteady rotational flow around the non-oscillating cascade and irrotational flow around the oscillating cascade into account, vortex distributions over the rotor contours are determined by solving integral equations of Fredholm's type of second kind which are derived from the tangential flow conditions on non-oscillating and oscillating cascade respectively, and then the exciting forces by gust and damping forces by cascade oscillation are obtained. The general characteristics of forced oscillation responses are clarified from equations of motion for bending-torsion coupled oscillation and, in particular, some notable features of frequency and amplitude in resonance are considered through numerical examples.