Study on Staged Start-up Mitigation Strategies for Water Hammer in Large-scale Centrifugal Pump Systems Based on One-dimensional and Three-dimensional Coupled Simulation

In large-scale centrifugal pump systems, the conventional linear start-up method often induces significant instantaneous pressure peaks (commonly referred to as water hammer) at the pump outlet when the valve is initially opened. These pressure surges not only exceed the system's designed operational pressure but also exert substantial mechanical stress on critical components, such as the impeller, potentially disrupting the system's stability and reliability. This study investigated whether a staged start-up method can effectively minimize the instantaneous pressure peaks generated at the pump outlet upon the completion of the start-up process. The transient external characteristics and internal flow field variations of a medium-to-high specific speed centrifugal pump system during staged start-up were investigated by integrating one-dimensional external characteristics analysis and three-dimensional internal flow field simulation. The study revealed that under the conventional linear start-up method, where the pump speed is increased to the rated speed before opening the valve, the pump–valve coordinated start-up mode generates an instantaneous pressure peak at the pump outlet, exceeding the designed head by 39%. In the staged start-up method, where the valve is opened in advance when the pump speed reaches 0.7 times the rated speed, the pressure peak is reduced by 23.94% compared with that in the linear start-up method, Additionally, the pressure fluctuation within the internal flow field is significantly mitigated, effectively ensuring the safe start-up and operation of the large-scale centrifugal pump.