Study on Structure Dynamic Characteristics for Internal Components of Kaplan Turbine Runner under Different Contact Modes

Abstract

The stress and fatigue of the runner during the operation of the large Kaplan turbine are one of the key issues in the operation of turbines. Due to the complexity of the working load and the geometric configuration of the Kaplan turbine runner, the different contact modes between the internal components of the runner will have an impact on the stress and fatigue results. Therefore, the unsteady CFD calculation of the full channel is conducted in this article to analyze the hydraulic characteristics of the turbine blades in the unsteady flow field, such as pressure and torque. The pressure load is loaded onto the runner using a fluid–structure interaction (FSI) theory, and the stress characteristics of the blade, blade lever, and runner body are compared under three contact modes. Based on the dynamic stress spectrum of the blade lever calculated under three contact conditions, the life of the blade lever is predicted using the rain flow counting method and the Palmgren–Miner theory. The results indicate that the rotation of the runner has a significant impact on the hydraulic and structural characteristics of the Kaplan turbine. The non-uniform and asymmetric stress and torque conditions gradually cause fatigue in the components of the runner. The average and amplitude of dynamic stress on the blade, blade lever, and runner body under frictional and frictionless contact are greater than those of fixed contact. The life of the blade lever calculated under fixed contact is much greater than that under frictional and frictionless contact; therefore, the contact conditions have a significant impact on the structural characteristics of the runner.