Numerical and field experimental study on the start-up process of a prototype axial-flow pump system considering the motion characteristics of cutoff facilities

Clarifying the evolutionary mechanism of the start-up process of a large axial-flow pump that includes cutoff facilities is of great significance for ensuring the safe and stable operation of such a system. However, the three-dimensional dynamic characteristics of the start-up process of a prototype axial-flow pump system (PAPS), considering cutoff facilities, are still unknown. In this paper, a method combining motor starting characteristic experiment, computational fluid dynamics, and field test of prototype pump system is proposed to study the starting process of PAPS. The results indicate that flow interruption facilities will significantly affect the start-up process of the pump system. High-speed forward fluid particles collide with reverse fluid particles in the guide vane channel during the acceleration of the pump owing to the influence of the cutoff facilities. A large number of wall vortex structures block the guide vane channel. This leads to a brief plateau period during the increase in instantaneous head. As the start-up process progresses, a clear horseshoe-shaped vortex structure is formed at the trailing edge of the guide vane, which subsequently falls back. The accelerated shedding of horseshoe-shaped vortical structures at the trailing edge of the guide vane induces high-frequency pulsating components, leading to a high-energy region of the pressure fluctuation signal at the outlet of the guide vane, which gradually expands toward higher frequencies. During this transition process, the flow field near the cutoff facility also exhibited significant unstable flow behavior. After the interaction between the outflow at the flap gate and the outflow at the gate, entrainment occurs, forming a region of circulating motion, and a large number of vortices with a jet-like structure are formed at the exit of the flap gate.