Influence of guide vane opening on channel vortex and pressure pulsation in Francis turbine runners

Abstract

In order to investigate the impact of guide vane opening on channel vortex and pressure pulsation within the runner of a Francis turbine, this research examines the cavitation phenomenon, channel vortex phenomenon, and flow field characteristics of a power station's turbine in China. The investigation is conducted using computational fluid dynamics theory. Furthermore, the analysis focuses on the influence of changes in guide vane opening on the flow state within the turbine runner. The findings indicate that the occurrence of rotor cavitation is severe when the opening is small, and increasing the opening reduces the cavitation capacity of the rotor. The presence of a lobe vortex phenomenon is mainly observed within a small range of guide vane openings, and altering the opening modifies both the range of influence and flow characteristics of the lobe vortex. In the middle range of guide vane openings, vortex pressure pulsation dominates within the rotor, with the highest amplitude of pressure pulsation occurring at a 60% opening. In the large opening range, pressure pulsation mainly occurs in the lobe frequency pressure pulsation of the rotor within the lobe-less area. The amplitude of blade frequency is typically small, indicating good hydraulic stability of the unit. These study results elucidate the interval of stable operating conditions for the unit and offer valuable insights for maintaining its stable operation.