Study On The Influence Of Volute Geometry On Performance Of High Specific Speed Centrifugal Pump

Centrifugal pump with high head,high efficiency,accompanied by problems such as operational stability and noise vibration.The dynamic and static interference between the impeller and the volute,the fluid diversion in the impeller and the secondary reflux of the fluid at the outlet of the volute cause radial force and pressure pulsation in the pump,resulting in poor stability and noise vibration.In this thesis,the high specific speed centrifugal pump of a seawater desalination energy recovery device was taken as the original model.The effects of different volute structures on the external characteristics,internal flow field,radial force characteristics and pressure pulsation characteristics of the centrifugal pump were compared and studied through numerical calculation.The influence of the Re volute with better performance on the unsteady flow characteristics of the centrifugal pump was analyzed when volute tongue angle was changed.The main research contents and conclusions are as follows:（1）The three-dimensional hydraulic model was established by NX 12.0 software,and the SST k-ωturbulence model was selected to simulate the steady whole flow field.The reliability of the selected turbulence model was verified by building a test platform,and the error between the two models was less than 3.9%.By analyzing the external characteristics and internal flow characteristics of the centrifugal pump,it is found that the efficiency of the centrifugal pump is86.53%,and the hydraulic loss of the volute is 3.5%higher than that of the impeller.The reason is that the flow pattern of the volute tongue area,volute section and water outlet section is poor.（2）Based on the steady numerical calculation,the influence of different volute shapes on the hydraulic performance of centrifugal pump under different working conditions were compared and analyzed.The results show that the hydraulic loss of the volute domain is improved after changing the shape of the volute.The efficiency of the centrifugal pump can reach 90.50%under the optimal working condition,and the volute loss is only 4.62%.Under the working conditions of（0.4～1.4）Q₀,the head shows a typical“hump”characteristic when the working condition is small.With the increase of flow rate,the loss of volute domain increases.When the Re volute is used,the radial force of the volute and the impeller is the smallest under the 1.0Q₀ condition,and the blade load is larger under the smaller condition,and the work ability is stronger than other volutes.（3）Based on the unsteady numerical calculation,the effects of different volute shapes on the unsteady radial force characteristics and pressure pulsation characteristics of centrifugal pumps under different working conditions were compared and analyzed.The results show that the radial force of the impeller fluctuates obviously in a period of impeller rotation,which is similar to the“star”,while the radial force of the volute fluctuates in a small range,which is similar to the“circle”.Under all working conditions,the radial force on the impeller and volute is significantly smaller when the Re volute is used.Under the same working condition,the peak-to-peak value in the impeller flow channel gradually increases along the flow direction,while the peak-to-peak value in the volute flow channel increases first and then decreases.At1.0Q₀ working condition,the peak-to-peak value in the impeller and volute reaches the minimum.Under different working conditions,the main frequency in the impeller is the rotation frequency and its frequency doubling,while the main frequency in the volute is the blade frequency and its frequency doubling.（4）The unsteady flow field characteristics of Re volute centrifugal pump with better performance were studied by changing the tongue angle.The results show that when the tongue angle is 30°,the external characteristics of the centrifugal pump are optimal,and the peak-to-peak value of the monitoring points vol2～vol6 arranged in the volute flow channel is the lowest.In addition to the measuring points vol1 and vol7,the pressure pulsation of the blade frequency and its frequency doubling appeared at the five measuring points with different tongue placement angles.The pulsation amplitude of the measuring point vol2 was the largest,and the measuring point vol4 obviously weakened,and then the pulsation amplitude of the measuring point vol2～vol7 gradually weakened.Under the design condition,the radial force of the impeller and volute reaches the minimum value,and the radial force is particularly obvious when the tongue placement angle is 30°.