Spatial distribution of rigid vorticity in pump turbine under turbine mode with different heads

Abstract

Abstract Pump turbines under off-design operating conditions can generate significant vortex structures that cause hydraulic instability in the unit. The aim of this study is to investigate the spatial distribution of large-scale rigid vortex structures in the runner blade channels of a model pump turbine operated under different head conditions with fixed guide vane opening in turbine mode. A new method is proposed that utilizes a relative streamline coordinate system based on mean camber line and provides a unique perspective to quantify the spatial distribution and intensity of various physical variables within the runner blade channels from a novel perspective along the streamwise, circumferential, and spanwise directions. Ultimately, an analysis is conducted on the causes of rigid vortex structures. This paper provides a novel and advanced research technique to analyse unstable flow structures in pump turbines.