VIBRATION ANALYSIS OF SHROUDED TURBINE BLADES FOR A 30 MW GAS TURBINE

Turbine blades are subjected to high static and dynamic loads. In order to reduce the vibration amplitude means of friction damping devices have been developed, e.g. damping wires, interblade friction dampers and shrouds. This paper presents both numerical and experimental results for investigating the dynamical behavior of shrouded turbine blades. The studies are focused on the lowest family of the bladed disk. The aspect of experimental studies, the effect of the shroud contact force on the resonance frequency of the blade was examined by using the simplified blade test stand. Based on the result of the simplified blade studies, the shroud contact force of the real blade was determined in order to stabilize the resonance frequencies of the bladed disk system. The resonance frequencies and mode shapes of the real bladed disk assembly were measured in no rotation and room temperature condition. Finally, the dynamic strains were measured in the actual engine operations by using a telemetry system. The aspect of analytical studies, a non-linear vibration analysis code named DATES was applied to predict vibration behavior of a shrouded blade model which includes contact friction surfaces. The DATES code is a forced response analysis code that employs a 3-dimensional friction contact model. The Harmonic Balance Method (HBM) is applied to solve resulting nonlinear equations of motion in frequency domain. The simulated results show a good agreement with the experimental results.