Fatigue Life Prediction of a Pump Turbine Runner

Abstract

The working environment of the runner of a hydro-turbine unit is complex, and it is subjected to relatively large and variable water pressure. Fatigue cracks may occur after a long period of work, and even cause the runner to lose its working ability. The fatigue crack problem of hydraulic turbines should be paid attention to. This paper introduces the nominal stress method which is often used to analyse the fatigue life of a hydraulic turbine unit. Modelling and numerical calculation are carried out for a pump turbine unit. Stress concentration points and load spectra are calculated for different working conditions of the turbine. The load spectra are processed by rain flow counting method. The fatigue life of the runner under different working conditions is carried out by Miner criterion. The results show that the fatigue life of the unit tends to be infinite under steady working conditions, and the fatigue life under variable working conditions is far less than that under steady working conditions. Therefore, from the point of view of fatigue life, the working process under variable working conditions should be minimized to improve the service life of the unit.