Numerical investigation of the stress state in the runner hub of a Kaplan turbine

Abstract

In the context of global warming, Romania has assumed through European directives to increase the percentage of energy produced from renewable sources. In the last years, energy generated in hydropower plants had the largest contribution to the total renewable energy production. This is expected to continue in the forthcoming period, considering the seasonal nature of energy produced in photovoltaic and wind farms. Therefore, efforts are made to increase the installed power of hydropower plants and to reduce the downtime for maintenance and repairs. Increasing the installed power requires an accurate diagnosis of the components of hydro turbines. In Kaplan turbines one of the main components is the runner hub. The runner hub is subjected to a complex state of loading that depends on several factors, the most important being the runner opening and the operating mode. This paper presents a methodology for numerical analysis of the stress state of a six-bladed Kaplan runner hub. The algorithm for transposing to the hub the forces that act on the runner (hydrodynamic loads, mass and inertial forces, forces generated by the action of the servomotor) is described. The results of the numerical analysis are presented in the form of stress and displacement plots.