Gas-liquid flow patterns visualization in a self-priming centrifugal pump

The self-priming pumps are ubiquitous in gas-liquid mixtures lift and transportation areas. The fast self-priming time is a vital evaluation index for a self-priming pump. However, the bubble movement path and the bubble size distribution characteristics during the self-priming process are still an open issue. This paper aims to obtain the gas-liquid flow patterns inside a centrifugal pump during the self-priming process and evaluate the effect of the rotational speed and the position of the back-flow hole on the self-priming time through experiments. A centrifugal pump with a double-blade was designed as a visualization prototype. The high-speed photography technology was used to capture the bubble motion and size in the pump during the self-priming process. The bubble image processing method was used to identify the bubble size distribution in the diffuser during the self-priming process. The bubble number and size distribution images were presented to understand the influence of the rotational speed and the position of the back-flow hole. The higher rotational speed accelerates the gas-liquid mixing rate and shortens the self-priming time. However, there is a limited value of the self-priming time as the speed goes up to a certain high level. Moreover, the position of the back-flow hole slightly affects the self-priming time.