Recent developments in the dynamic analysis of water turbines

Abstract

This article gives an overview of the current methods for life cycle analysis with special emphasis on dynamic load analysis. Recent developments in CFD simulations of time-dependent phenomena are presented, such as the von Kármán vortex shedding at stay vanes in a Kaplan turbine and the part load vortex in the draft tube of a Francis turbine and a pump turbine. A major topic of this article is the unsteady pressure field in a pump turbine, which is caused by the interaction of guide vanes and runner blades. CFD results of the pressure pulsations and their validation through comparison with measurement data are presented. It is shown how the predicted time-dependent pressure load is transferred as input to the structural analysis of the runner. For the analysis of the response of the runner to the dynamic load knowledge of the natural frequencies of the structure is required including the influence of the surrounding water on the natural frequencies. New results of the prediction of the natural frequencies of a Francis runner including the added mass effect due to the surrounding water are presented. For Pelton runners the state-of-the-art of measurement of eigenfrequencies and detuning are discussed along with the potential improvements due to the new simulation methods.