Transient cavitation characteristics of compound centrifugal impeller

In order to reveal the transient characteristics of the compound impeller under cavitation condition, the research method using numerical simulation was adopted. The steady and unsteady numerical calculations of cavitation flow in compound impeller were carried out. Monitoring points are set in the circumferential area of the volute aiming to compare the characteristics of pressure fluctuations in the pump during the state of the non-cavitation and cavitation. The results show that in the circumference of the volute, when cavitation isn't started, the dominant frequency is between the long blade passing frequency and the blade passing frequency and is closer to the long blade passing frequency; in the state of cavitation, the pressure fluctuation amplitude in the volute decreases and the dominant frequency is most influenced by the long blade passing frequency. Analyzing the transient flow field inside the impeller under cavitation and non-cavitation states, it is found that when cavitation is started, axial vortices are generated inside the impeller flow path, and the cavitation area is large, vapor blocks the flow path, causing the head of the pump declines.