To clearly and intuitively study the self-priming characteristics of a self-priming pump under different impeller diameters,a visualization test bench was built based on the visualization technology.The self-priming time of five self-priming pumps with different impeller outer diameters and the transient changes of gas-liquid flow state in each region of the self-priming pump were recorded and compared by using high-speed camera,and the self-priming characteristics of the self-priming centri-fugal pump were experimentally studied.The results show that the visualization experiments can accu-rately capture the gas-liquid two-phase flow in the pump,and the flow state is transient and clear.It can clearly reveal the influence of different impeller outer diameters on the gas-liquid two-phase flow state at each stage of the self-priming pump during the self-priming process.The change in the outer diameter of the impeller affects the gap between its outlet and the baffle,thereby causing changes in the gas-liquid mixing state inside the pump and the characteristics of bubbles in the mixed fluid.Within a certain range(D2/160 is 0.963-1.000),the outer diameter of the impeller is directly propor-tional to the self-priming performance of the self-priming pump.As the outer diameter of the impeller increases,the gas-liquid mixing efficiency inside the pump increases,the self-priming time decreases,and the self-priming performance improves.On the contrary,the smaller the outer diameter,the worse the self-priming performance of the pump.When the outer diameter of the impeller decreases to a cer-tain extent(D2/160 is less than 0.963),the gas-liquid mixing process stops and the self-priming pump cannot perform self-priming.
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