Fatigue Analysis of Francis Turbine Runner as a Result of Flow-induced Stresses

Abstract

Hydroelectricity plays a significant role in energy generation. It is by far the most reliable, sustainable and clean form of energy generation. Another beauty of hydropower plants is that they can operate under various load conditions and can respond well to sudden changes in the power grid. However, while doing so, hydroelectric machines are dragged beyond their operational limitation leading into fatigue deformation thus hidering the structural integrity of mechancial componets of hydraulic turbines. Fatigue deformation incurs huge financial losses, energy losses, national grid imbalance issues and sometimes tragic hazards at plant site. As a preventive measure or as a failure analysis, it is imperative to study about sensitive parts that are susceptible to fatigue failures.

Fatigue study can be carried out experimentally via analysis of real time measurement of pressure, fluid flow, vibration analysis in actual hydraulic turbines or their prototypes. Another method is through numerical analysis which is popularly used by researchers due to complex structures of actual machines and also due to time, cost considerations. Many studies have been carried out to study structural integrity of Francis runner using computer based numerical analysis. Fluid Structure Integration (FSI) is one such numerical method which is widely used for flow induced stress study. This research work has employed the same for fatigue analysis of Francis turbine runner using a commercial software, ANSYS 15.0. Through FSI analysis, it was observed that the maximum pressure lies at the joint between blade and band. It was further observed that Francis turbine runner considered for this study has infinite life and minimum damage combined with maximum factor of safety.