Abstract: A transparent self-priming centrifugal pump device has been designed and tested to study its performances at different rotational speeds and the relationship between its self-priming performance and rotational speed. We use a high-speed camera to record the development of the gas-liquid two-phase flow patterns in its spiral case at the early self-priming stage, and measure the time variations of the liquid level in its suction pipe. The pump’s self-priming process is divided into the suction stage, the inflow stage, and the outflow stage; the influence of rotational speeds on the self-priming time in the suction and inflow stages is summarized. The experimental results show that at low rotational speeds, the pump’s self-priming time is inversely proportional to the rotational speed, because the liquid level in the gas-liquid separation chamber has not yet reached its highest at the end of suction stage. In this stage, gas content is the dominant factor of the self-priming performance; the higher the rotational speed, the higher the gas content, the higher the exhaust efficiency and the better the self-priming performance. At high rotational speeds, the self-priming time is proportional to the rotational speed only in part of the rotational speed range, because the liquid level in the chamber has reached its highest at the end of suction stage. In this case, a higher rotational speed means a faster gas reflux speed which results in the failure of discharging gas in time and even part of the self-priming function. This study illustrates the relationships of the rotational speed versus the liquid level in the inlet pipe and the liquid level in the gas-liquid separation chamber, and reveals the relationship of the rotational speed versus the self-priming performance of the pump via an explanation of the exhaust efficiency, thereby providing reference towards the design on the rotational speed of self-priming centrifugal pumps.

Key words: self-priming pump, self-priming performance, pump rotational speed, experimental method, high speed photography