Flutter prediction in turbomachinery with energy method

Abstract

The study described in this article is the application of energy method for the prediction of flutter boundary and the effects of some parameters on aeroelastic stability in turbomachinery. The unsteady flow with multi-layer moving grid technique for blade oscillation was undergone for aerodynamic work with the blade passage being discretized using a background fixed H-grid and a body-fitted O-grid moving with the blade. Also, with the assumption of equivalent viscous damping, aerodynamic modal damping ratio was defined based on energy method. The numerical method, with mode shapes and nodal diameter numbers considered, was applied for a transonic compressor rotor stage for which measured flutter boundary on characteristic map was available. It was found that the calculated flutter boundary in the first bending blade mode agreed well with the measured one. Furthermore, it was concluded that the mode shapes and inter-blade phase angle were key parameters on aeroelasticity in turbomachinery and that the flutter instability was mainly induced by the co-action of shock wave and separated flow.