Research On Internal Flow And Energy Loss Characteristics Of Centrifugal Pump Impeller Based On PIV Technology

As an important fluid transporting machine,centrifugal pump plays a vital role in national production and life.The impeller is the most important component of the centrifugal pump.Its own performance has a profound impact on improving the efficiency of the centrifugal pump.There are many related researches on the flow characteristics of pumps in domestic and foreign scholars.However,the deeper research on centrifugal pumps is limited because of the complexity of the internal flow of centrifugal pumps.In this paper,the centrifugal pump impeller is taken as the research object.The following work and research are carried out for its internal flow and energy loss characteristics by PIV technology:(1)Summarized the domestic and foreign research status of centrifugal pump internal flow,energy loss characteristics and PIV testing technology.(2)The internal flow characteristics of the centrifugal pump impeller are analyzed.It is found that the internal flow of the impeller flow channel is relatively stable and uniform when the centrifugal pump speed is 800r/min.When the centrifugal pump speed is 600r/min,the working condition at this time far away from the design speed is too much,there will be unstable flow inside the corresponding flow channel at 1.0Q_d.In the meantime,the internal flow is unstable,and the low-speed fluid zone will be accompanied.(3)The low-speed fluid zone appears firstly around the suction side of the flow channel,and the flow separation phenomenon occurs earlier.Besides,the separation vortex is generated in the whole impeller.Two vortices with opposite directions of rotation will appear simultaneously around the suction and pressure surfaces inside the flow channel,when the flow rate is reduced to a certain extent.As the flow rate gradually decreases,the flow path is gradually blocked by the fluid.The suction surface vortex inside the flow passage gradually moves toward the blade inlet direction,and the pressure surface vortex gradually moves toward the impeller outlet direction,because the two oppositely directed vortices interact with each other.(4)Based on the study of energy loss characteristics,the quantitative expression of energy loss in the pump based on the Euler head is presented.The results show that the Euler head is the smallest at the blade inlet position in the impeller flow path.The Euler head gradually increases along with the direction opposite to the impeller exit.And a small decrease begins to occur near the impeller exit when r/r_m is about 0.89.At the inlet position of the blade,the absolute flow angle is the largest.The absolute flow angle drops rapidly and then slowly decreases in the direction of fluid flow.A small increase begins to occur near the impeller exit when r/r_m is about 0.89.In addition,as the flow rate decreases,the absolute flow angle gradually decreases.(5)There is a large high Euler head region near the suction surface of the impeller blade trailing edge in the same flow channel.With the formation and strengthening of the positive vortex of the suction surface,the Euler head in this region gradually increases.The Euler head,around the pressure surface of the trailing edge of the blade,gradually decreases,With the appearance and strengthening of the reverse vortex near the trailing edge of the pressure surface.The comparison shows that the positive vortex near the suction surface of the impeller promotes the increase of the Euler head,and the reverse vortex near the pressure surface of the blade has an inhibitory effect on the increase of the Euler head.