Flutter analysis of mistuned bladed disks (Effect of bladed disk structure on flutter characteristics)

Abstract

Although bladed disks are nominally designed to be cyclically symmetric (tuned system), the vibration characteristics of all the 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. In the forced response of a mistuned bladed disk, the responses of all the blades become different, and the response of a certain blade may become extremely large due to splitting of the duplicated eigenvalues and distortion of the vibration modes. On the other hand, many researchers suggest that mistuning suppresses blade flutter, because the complete traveling wave mode is not formed in a disk. In the previous paper, authors studied the forced response of the mistuned bladed disk, using the reduced order model SNM (Subset of Nominal system Modes), and clarified that the effect of the bladed disk structure on the amplification factor. This work is a follow-up study on the previous paper. The stability analyses of mistuned bladed disks with the free-standing blade structure and the continuous ring-blade structure are carried out extensively, using the reduced order model SNM. Comparing the results of the stability analyses of mistuned bladed disks, the effect of the bladed disk structure on the blade flutter is clarified.

Keywords

• turbomachinery
• self-excited vibration
• blade
• flutter
• damping
• mistuning