Start-up strategy of mixed-flow pump system with impulse operation

The impact head, tip leakage vortex, and pressure pulsation during start-up can cause vibration and noise in the pump, and affect its hydraulic performance. The linear speed start-up method cannot solve the impact head and vibration problems. Therefore, in this study, a mixed-flow pump was investigated to explore the influence of different speed start-up schemes on the flow field and to optimize them. The rated speed was set to 1634 r/min, and numerical simulations of different start-up schemes were carried out using the standard k-ε model. Furthermore, the turbulent kinetic energy distribution of the inlet and outlet sections of the mixed-flow pump during different start-up schemes was provided. In addition, the normalized helicity and blade surface pressure for different start-up schemes were compared. Finally, an evaluation function was proposed to evaluate the stability of the flow field during start-up. The results showed that the evaluation function had four factors related to speed and acceleration during start-up. Factors α and γ were obtained based on the acceleration and speed at 0.2 s and 0.42 s during start-up, respectively. Factor β was affected by the time taken to reach the rated speed. Parameter δ was determined by the acceleration of the period before reaching the rated speed. Based on the evaluation function, a theoretical scientific selection of speed start-up scheme is proposed to improve the stability of the flow field in the pump during start-up.