Numerical study on hydraulic and self-priming performance of a double-stage self-priming pump

        

Vertical self-priming pump has numerous advantages and has been widely used in industrial and agricultural areas. Nevertheless, impeller in single-stage self-priming pump bears large diameter and huge friction loss in the delivery of high-lift fluid, and enhanced requirement for sealing capacity meanwhile generates greater increment of power loss from sealing auxiliary-impeller and sealing ring. Both of these have resulted in low efficiency in operation, to the extent of imposing restriction on the further application of self-priming pump. In this paper, a new design of double-stage vertical self-priming pump with two impellers settled back to back was put forward to cover the shortfalls above. 
 

The internal flow field was calculated adopting realizable k-ε turbulence model in commercial CFD software Fluent and performance prediction was conducted. Concurrently, two-phase flow inside this self-priming pump without backflow hole was calculated by gas-liquid two-phase unsteady simulation to explore the self-priming characteristics. In order to consist with practical self-priming situation, 

a section of suction pipe filled with air was installed as the initial condition, pressure inlet and pressure outlet was set as boundary condition. Base on the results, the variation of pressure distribution and the fluctuation of air volume fraction on the specific cross-section of impeller and volute were obtained to study the self-priming process. The simulation and test results showed distinct uniformity, which indicated that the optimizing design provided impacts great effect on efficiency improvement as well as meeting the purpose of energy-saving and expense-reduce in the aspect of self-priming performance. The research here has provided the instruction to the design of high-head vertical self-priming pump.