Numerical Investigation On The Self-priming Process Of A Self-priming Centrifugal Pump

This study is financially supported by the National Natural Science Foundation of China(Grant No.51879120)and Natural Science Foundation of Jiangsu Province(No.BK20151342).The supports are gratefully acknowledged.The self-priming centrifugal pump is a kind of turbomachinery that develops low efficiency with a great capability of self-priming.Due to their unique capability of prime advantages,they have found their applications in many fields such as the construction,petrochemical,chemical,fire and mining fields.The self-priming centrifugal pump design has undergone several modifications over the years.However,the major drawn back of self-priming centrifugal pump is their low efficiency compared to other vaned hydraulic pumps.Although,the main idea is to study the self-priming process of self-priming centrifugal pump,the two-phase flow behaviour and the pressure fluctuations were also studied to serve as a reference for a future improvement.Firstly,numerical calculations were carried out after the self-priming centrifugal pump model was designed without modifying its geometrical parameters of design by using the Langrangian and Eulerian model.In this numerical approach,the real practical operation of the pump was used to carry out this simulation study.During the early stage of pumping the gas inhaled was pumped in the self-priming process.Observing the flow characteristics,the two chambers(separating chamber and storage chamber)play a primordial role particularly the separating chamber.The performances of experimental and numerical were consistent with an approximation of 4.4% uncertainties.Furthermore,different physical parameters comprising exchanged mass flow,pressure fluctuation and turbulent kinetic energy intensity were given at different operating conditions to analyze the internal flow characteristics.The gas presence in the pump reduced the performance of the pump by consuming more input power.At the early stage,air volume fractions of the pump outlet decreased rapidly about 50% while that of inlet increase and both fluctuate till zero at 3s corresponding to the single the phase flow.In the initial stage of self-priming a larger number of bubbles wrapped around the outer edge of the impeller,and formed vortex distributions.It was found that the pressure distribution was lower during the early stage of self-priming process due to the instabilities such as vortices mixture process and two phases flow interactions.The air volume fractions at the inlet of the impeller were lower compared to that of the pump outlet due to the mixture process of two-phase flow.The pressure became higher after the self-priming process since the flow is single-phase flow(water)corresponding the self-priming time of 3 seconds.The amplitude of pressure fluctuation intensity reaches a maximum at the volute-impeller interface,and then decreases in the radial direction or by moving to inner radius.The turbulence kinetic energy also increased over the time from the outer impeller radius to inner radius and at the period 3s it creases due to the single flow.In perspective,this work will be performed well to optimize the working conditions by:(1)Varying the initial volume of water contented in the storage chamber.(2)Investigating the optimal position and the size of the reflux-hole of the self-priming pump.(3)Optimizing the gap between the impeller and the volute tongue as it has seen from the results that the highest peak of pressure fluctuation occurs at the volute when the impeller passes over there.