Investigations on flutter characteristics of rotor blade with IGV/fan interactions

It is widely known that the upstream wake is a major contributor to the forced vibration of rotor blades, but seldom noticed its influence on flutter characteristics. The present research performs aeroelastic analysis on a typical turbofan NASA Rotor 67 by CFD technique and energy method. The results indicate that the most dangerous flutter mode of the rotor blades is the second bending mode with IBPA=60°without IGV. While analyzing the rotor with IGV, the wake changes the flutter characteristics of the rotor blade significantly. If the natural frequency of the most dangerous flutter mode of the blade is close to the IGV passing frequency, flutter may happen even it is stable without IGV. For a mode whose natural frequency is far away from the IGV passing frequency, the wake may also drive the vibration to be unstable. Though the IGV does not influence the performance of the rotor much, it does add significant nonlinear effects to the flutter behavior of the rotor blades. Designers need to consider the coupling effects between IGV and rotor to avoid the significant change of the flutter boundary.