Sensitivity of the Winter-Kennedy method to inlet and runner blade angle change on a Kaplan turbine

Abstract

The Winter-Kennedy (WK) method is a widely used index testing approach, which provides a relative or index value of the discharge that can allow to determine the on-cam relationship between blade and guide vane angles for Kaplan turbines. However, some discrepancies were noticed in previous studies using the WK approach. In this paper, a numerical model of a Kaplan model turbine is used to study the effects of upstream and downstream flow conditions on the WK coefficients. Experiment on the model turbine is used to validate unsteady CFD simulations. The CFD results show that the inflow condition affects the pressure distribution inside the spiral casing and hence the WK results. The WK coefficients fluctuate with high amplitude - suggesting using a larger sampling time for on-site measurement as well. The study also concludes that to limit the impact of a change in runner blade angle on the coefficients, the more suitable WK locations are at the beginning of the spiral casing with the inner pressure tap placed between stay vanes on the top wall. © 2019 Published under licence by IOP Publishing Ltd.