Abstract: In order to explore the transient characteristics of a prototype centrifugal pump during startup period, the variations of the external performance of the pump are recorded in experiments at different discharge valve openings, and then the non-dimensional parameters of the flow rate and head are also used to analyze the transient behavior. The result shows that the rise characteristic of the rotational speed is not basically changed by working points, which mainly depends on the startup characteristics of the driving motor. Compared with the rapid rise of the rotational speed, the rising speed of the flow rate is relatively low at the beginning of the startup. Moreover, the flow rate lags behind the rotational speed to rise to final stable value, and the delay becomes more severe as the discharge valve opening increases. In the range of smaller valve opening, the pressure impact shows decrease tendency as the discharge valve opening increases; while in the range of higher valve opening, the pressure impact shows increase tendency as the discharge valve opening increases. There generally exists the shaft power impact phenomenon in the process of startup. The non-dimensional analysis shows that the non-dimensional instantaneous head is of extremum at the very beginning of startup, and quickly falls to the minimum, then gradually rises to final value. The non-dimensional instantaneous flow rate always shows a rise trend during whole startup period. It is found that the quasi-steady assumption can not be used to accurately assess the transient flow during startup period.

Key words: Centrifugal pump, Experimental investigation, External performance, Non-dimensional analysis, Startup