Hydraulic fluctuations during the pump power-off runaway transient process of a pump turbine with consideration of cavitation effects

• Published in: Journal of hydrodynamics. Series B 2021-12, Vol.33 (6), p.1162-1175
• Main Authors: Fu, Xiao-long, Li, De-you, Wang, Hong-jie, Cheng, Yong-guang, Wei, Xian-zhu
• Format: Article
• Language: English
• Subjects: Engineering; Engineering Fluid Dynamics; Hydrology/Water Resources; Numerical and Computational Physics; Simulation
• ISSN: 1001-6058; 1878-0342
• DOI: 10.1007/s42241-022-0105-5

A runaway transition after the pump power interruption and the simultaneous guide vane servomotor failure is one of the most dangerous and complex transitions for a pumped storage power system (PSPS). This paper analyzes the fluctuation behavior and mechanism of a PSPS during a runaway transition caused by the pump power interruption. The transient cavitation flow in the PSPS is simulated by using a one-dimensional and three-dimensional coupling flow simulation method for the runaway transition. Subsequently, the effects of the transient fluctuation of the radial hydraulic thrust on the runner and transient pressures are analyzed using the short-time Fourier transform method. Finally, the mechanisms are analyzed based on the analysis of the internal flow field. This study suggests that the extreme fluctuation generally occurs near the critical transformation points between the two operation modes. In addition, the extreme fluctuation behavior is primarily related to the local backflow near the runner inlet and the unstable cavitation phenomena in the runner and the draft tube. This finding helps for optimizing the runner design to resolve the instability problems of a PSPS.