Study on vibration characteristics and stability of steam turbine vanes with large capacity

Abstract

A vane used in a low pressure end of steam turbine is usually fixed to an inner shroud and an outer ring by welding both ends. In such a vane structure, the damping in loading operation is comprised of the material damping and the aerodynamic damping, because the structural damping is very small. In such a steam turbine vane, the total damping may become negative, and the flutter may occur under the high loading condition. Therefore, in the design of the steam turbine vane, it becomes indispensable to evaluate the stability under the high loading condition. In this study, first, the vibration characteristics of steam turbine vane with grouped vane structure are examined in detail by use of the results of FE analysis. Second, the reduced order model (the equivalent spring-mass model) of the whole vane structure is assembled, based on the results of FE analysis. The stability analysis of the whole vane structure is carried out using the reduced order model, and the effect of the design parameter of the vane on the flutter is clarified. Finally, the mistuning analysis of the whole vane structure is carried out, using the Monte Carlo simulation, and the effect of the frequency deviation on the stability is clarified.