Study on the vibration characteristics of bladed disks (Effect of damping variation on the resonant responses of bladed disks)

Abstract

Although bladed disks are nominally designed to be cyclically symmetric (tuned system), the vibration characteristics of all blades on a disk are slightly different due to the manufacturing tolerance, deviations in the material properties, and wear during operation. These small variations break the cyclic symmetry and split the eigenvalue pairs. Bladed disks with small variations are referred to as a mistuned system. Many researchers suggest that while mistuning has an undesirable effect on the forced response, it has a beneficial (stabilizing) effect on blade flutter (the self-excited vibration). However, almost all studies have focused on the deviation of the blade frequency, and few studies have discussed the damping mistuning. In a blisk (integrally manufactured bladed disk), it seems that the damping mistuning can be neglected because the material damping is dominant. However, in a bladed disk with the blade root inserted into the disk groove, the damping mistuning caused by the partial contact between the root and groove in rotation cannot be neglected in predicting the resonant response of the bladed disk. Therefore, in this study, incorporating the damping mistuning into the FMM (Fundamental Mistuning Model), the frequency response analysis of the bladed disk is systematically carried out. From the calculated results, the effect of the damping mistuning on the vibration response of the bladed disk is clarified.

Keywords

• turbomachinery
• forced vibration
• blade
• damping
• mistuning