Vibration response analysis of mistuned bladed disk with platform damper (Effect of friction force deviation on vibration characteristics)

Abstract

Recently, a blade with friction damper has been used in a steam turbine and a gas turbine to improve the blade reliability. Especially, for the gas turbine blade in the upstream stage, a platform type damper has been widely used, where the damper pieces with variable geometries are inserted into the platforms between the adjacent blades. The damper piece is designed so that its surface gets contact with the platform surface uniformly. The contact condition of the damper piece (in other words, the equivalent stiffness and the damping caused by the damper piece), however, may change remarkably blade by blade, because of the manufacturing tolerance, the blade deformation in operation, the wear of the damper piece, and so on. Therefore, it is indispensable to consider the mistuning effect caused by the deviation of the contact condition of the damper piece, in evaluating the response of the bladed disk with the platform type damper. In this study, the mistuned bladed disk with the platform type damper is represented by the equivalent spring-mass model, and the frequency response analysis is carried out, using the direct method and the Monte Carlo simulation. The effect of the deviation of the contact condition caused by the damper piece on the response of the bladed disk is examined by the numerical simulation.