Influence of mistuning on aerodynamic damping of blade in transonic compressor

Abstract

A three-dimensional full-annulus computational model for aerodynamic damping prediction based on energy method is demonstrated by the consideration of a transonic rotor which is designed for experimental research of flutter to improve understanding the influence of frequency mistuning and inter-blade phase angle mistuning on aeroelastic stability of transonic compressor. Each individual blade is capable of vibration with its own independent frequency and phase angle, thus modeling a full-annulus rotor with arbitrary mistuned blades. The numerical analyses of alternate, random, linear frequency mistuning, and random inter-blade phase angle mistuning are performed in detail. The studies of tuned rotor show that the aerodynamic damping for the blade first bending mode is most sensitive to inter-blade phase angle. Further investigations on various frequency mistuning and inter-blade phase angle mistuning indicate that inter-blade phase angle mistuning has almost no effect on average aerodynamic damping of rotor, while frequency mistuning significantly changes it. Especially, the aerodynamic damping is about 7 to 11 times at the least stable conditions of the study rotor. Furthermore, the divergence of individual blade aerodynamic damping enlarges due to both frequency and inter-blade phase angle mistuning. The individual blade aerodynamic damping for frequency mistuned blade is affected significantly by the blade local mistuned pattern and mistuning amount. Even more remarkable, the local instability of blade is induced by inter-blade phase angle mistuning at some case. It is beneficial to improve understanding the blade response and onset time differences of flutter in turbomachinery flutter problem.