Gas-liquid separation characteristics inside a drainage self-priming pump with different balance holes during self-priming

Self-priming pumps are widely used in agricultural irrigation and drainage due to their ability to achieve self-priming without on-site water filling. The self-priming performance is the most critical indicator for evaluating the self-priming capability of these pumps and has been extensively studied. Balance holes, primarily used to reduce the axial force in single-suction centrifugal pumps, connect the rear pump chamber with the impeller region and function as secondary return holes. However, the influence of balance holes on the self-priming performance of self-priming pumps remains unexplored. Based on an established circulating pipeline system, this study designs three types of balance holes and conducts numerical simulations of the gas-liquid two-phase flow during the self-priming process for computational models with these balance holes. The effects of three different balance hole diameters on the hydraulic and self-priming performance of the pump are thoroughly investigated. The results reveal that an increase in the balance hole diameter significantly prolongs the self-priming time, though this effect is not linear. Moreover, enlarging the balance holes has a notable impact on the rapid exhaust phase of the self-priming process. • The influence of balance holes on the self-priming performance of self-priming pumps is revealed. • An increase in the balance hole diameter significantly prolongs the self-priming time, though this effect is not linear. • Enlarging the balance holes has a notable impact on the rapid exhaust phase of the self-priming process.