The transient flow in a centrifugal pump during the discharge valve rapid opening process

▶ DES is suitable for transient performance simulation of pump. ▶ Rotor–stator interaction phenomenon in transient process is captured. ▶ The transient performance deviates from the steady performance obviously. ▶ The flow acceleration and vortics revolution influence pump's transient performance. During the rapid opening period of the discharge valve in the pump system commonly used in nuclear reactor operation, the flow-rate of the pump increases impulsively. In this paper, we report on experiment and numerical simulations which were implemented to investigate the external transient hydrodynamic performance and the internal flow mechanism of the pump during this transient process. External and internal characteristics under different flow-rates were measured with an experimental system. The simulation for steady conditions was based on detached eddy simulation (DES) and sliding mesh was verified by comparing the simulation with test results. More importantly, the transient characteristics during the valve's rapid opening process were simulated using a similar method. Results show that the Q– H curve deviates from the steady-state value. The external characteristics are further explained by analyzing the relative velocity on the middle stream surfaces S 1 m and S 2 m between blades. The pump performance during the valve's rapid opening process is influenced both by the fluid acceleration and instantaneous evolutions of the vortex structure.