A methodology for assessment of erosive wear on a Francis turbine runner

Abstract

This study addresses the problem of erosive wear of Francis turbine runner of a typical power station located in northern Himalayan belt of India. Wear damage is determined using the erosion models of IEC-2009, IEC-2013, empirical assessment of Thapa and a methodology proposed in this research work. The proposed model introduces effect of relative velocity of turbine instead of characteristic velocity and also the effect of curvature of the blades by incorporating a parameter referred to as geometrical factor. The results obtained from the proposed model of erosive wear of the Francis turbine have been calibrated against Jhimrukh Hydropower Centre(JHC).The study also includes petrographic analysis of the sediment taken from the site of power station to obtain the parameters related to concentration(C), size (Ksz), hardness (Khd) and shape (Ksh). Effect of these parameters have been introduced into the wear models used in this investigation. The erosive wear assessment reveals that damage is severe at the runner outlet due to the high relative velocity(45.5 m/s against 15.5 m/s at inlet) and presence of hard minerals. The average loss of thickness for runner is 1.3 mm/year of operation, which agrees within 10% of the measured values from site of the power station.