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-e 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 alpha and gamma were obtained based on the acceleration and speed at 0.2 s and 0.42 s during start-up, respectively. Factor beta was affected by the time taken to reach the rated speed. Parameter delta 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.