Transient vibration analysis of multi-system coupling in pumped storage power Stations: Insights into cavitation-induced flow and shaft dynamics

Shaft vibration in pumped storage power stations (PSPSs) is a complex nonlinear problem driven by multiple coupled excitation sources, with cavitation-induced effects posing significant challenges due to the lack of effective methods. This study develops an innovative transient multi-system framework that integrates the Method of Characteristics (MOC), Computational Fluid Dynamics (CFD), and the Runge-Kutta method to couple the hydro-turbine shafting system (HTSS), hydro-turbine governing system (HTGS), and flow passage system. The framework reveals the evolution of cavitation during transient processes and its impact on shaft vibration. Key findings include: Cavitation evolves dynamically, initiating in turbine modes, peaking in reverse pump modes, and collapsing as rotational speed decreases, with bubble dynamics directly influencing pressure pulsations. Superimposed effects of water hammer, flow separation, backflow, and bubble collapse-induced shock waves are identified as primary drivers of shaft vibration. The maximum radial force on the runner occurs during flow rate reversal, while axial force peaks align with axial hydraulic thrust trends, highlighting distinct sensitivities to hydraulic excitation and mechanical forces. This framework provides a novel methodology and critical insights into the coupled dynamics of cavitation and shaft vibration, offering a foundation for improved design and operational strategies in PSPSs.