Flutter analysis of blisks with friction ring dampers

Aeroelastic flutter is a phenomenon when blades experience an aeroelastic self-excitation from the surrounding air resulting in the full destruction of aero-engines. It poses a big challenge for aero-engine bladed-disks design, especially for integrally bladed-disks (blisks). The lack of friction interfaces in blisks drastically reduces structural damping making them more likely to experience aeroelastic flutter. One of the most effective approaches to improve the damping in a blisk is the use of friction ring dampers. This paper presents a numerical study to investigate the effects of friction ring dampers on the aeroelastic stability of blisks. A lumped parameter model is used to represent the blisk with a ring damper. Aeroelastic self-excitations are simply represented by Van der Pol oscillators. The frictional contact between the blisk and ring damper is modelled by using Jenkins elements. Nonlinear modal analysis is used to compute the nonlinear dynamic response of the system. The results show that the friction ring damper can significantly reduce the risk of flutter and the amplitude of flutter induced limit cycle oscillations for a blisk by increasing the structural damping, especially at a high modal amplitude. The study also shows that the nonlinear modal analysis can efficiently identify the flutter boundary of such a strongly dissipated nonlinear system.