Study On The Influent Of Non-uniform Inflow On Performance Of Centrifugal Pump And Optimization

Centrifugal pump is widely used in multiple industries,its operation stability is very important for the whole pump system.When designing the impeller of centrifugal pump,it is generally assumed that the inflow is uniform,but in some special occasions,there will be non-uniform inflow in the impeller import,resulting in increased hydraulic loss,performance decline;Especially when the operation deviates from the design condition,the non-uniform inflow will aggravate the backflow,flow separation and other unstable flows,which will increase the pressure pulsation,and even cause the resonance of the pump set,resulting in serious consequences.In this paper,the influence of elbow inflow on the external and internal flow characteristics of single-suction centrifugal pump is studied.On this basis,it proposes a method to suppress non-uniform inflow through inlet guide vane,and the influence of different guide vane parameters on the inhibition effect is emphatively explored.The main research contents and conclusions are as follows:The influence of bend angle on hydraulic performance and internal flow characteristics of centrifugal pump is studied.The elbow inflow will lead to the decline of centrifugal pump head and efficiency,and the drop of pump external characteristics is more obvious with the increase of elbow angle.In addition,the elbow inflow will make the pressure uneven distribution of the inlet pipe,and the flow inhomogeneity is enhanced.The obvious vortex and low-speed area in the inner part of the elbow,the turbulent kinetic energy in the impeller increases and forms blockage,the impact loss at the inlet of the blade increases,the load decreases and the power capacity decreases.At the same time,the pressure pulsation at the inlet of the centrifugal pump was enhanced,and the pressure pulsation at different circumferential positions around the volute showed an increasing trend,especially at the position of the tongue.In order to improve the influence of non-uniform inflow on the performance of centrifugal pump,the method of installing inlet guide vane to suppress the non-uniform inflow was proposed,and the inhibition mechanism of different inlet guide vane on the non-uniform inflow was studied.With the decrease of the flow rate,the unevenness in the inlet pipe of the centrifugal pump increases,the backflow strength in the inlet pipe increases,and the performance of the impeller decreases.The inlet guide vane can inhibit the backflow in the inlet pipe,improve the inhomogeneity of the impeller import,make the incoming flow into the impeller more smoothly,the high turbulent kinetic energy region in the impeller is reduced.Compared with the straight guide vane,the airfoil guide vane has a better improvement effect on the non-uniform inflow.The improvement effect of the installation angle,thickness and number of guide vane on the non-uniform inflow under the condition of small flow was studied.The different installation angles change the circumferential velocity component of the impeller import,the high turbulent kinetic energy area near the blade pressure surface in the flow passage is reduced,and the pressure on the blade pressure surface is increased,thus increasing the blade load.The influence of blade thickness on external characteristics is small.The low speed region and high turbulent kinetic energy region in the flow passage are changed mainly by affecting the backflow at the impeller import,and then the total pressure and turbulent kinetic energy at the impeller outlet are changed.The number of blades changes the non-uniformity of the impeller import section by changing the backflow in the inlet pipe.The experimental design is used to consider the influence of the interaction between the three parameters of the airfoil guide vane on the performance of the centrifugal pump under the elbow inflow condition.Airfoil optimal parameters for installation guide vane angle 45° in leaf number is 4,leaf thickness is 2.0 mm,compared with the absence of guide vane,it is found that with the addition of airfoil inlet guide vane,the circulation difference between inlet and outlet of the impeller decreases,but can improve the work ability of impeller blades,and reduce the pressure inside the inlet pipe and impeller pulse amplitude.