Influence Of Anti-guide Vane Design On Hydraulic Performance Of Segmented Multistage Centrifugal Pump

The segmental multistage centrifugal pump is widely used in the engineering field,and can easily and quickly meet different head requirements by increasing or decreasing the number of stages.The reliability problem is more prominent,and one of the main measures to improve the reliability of operation is to reduce the axial length of the pump.Radial guide vanes are an indispensable part of the segmented multistage centrifugal pump.Its hydraulic design will not only affect the hydraulic efficiency of the pump,but also reduce its axial width is the key to optimizing the overall axial size of the pump.Especially,the axial width of the anti-guide vane has relatively large optimization space in hydraulic design.In this paper,the segmental multi-stage centrifugal pump is taken as the research object.When the axial width of the anti-guide vane is shortened as much as possible,the research goal is to ensure that the pump head and efficiency do not drop significantly.The RNG k-εturbulence model is used to calculate the unsteady constant value,and the axial width of the anti-guide vane,the relative position of the blade in the circumferential direction,the radius of curvature in the middle of the blade,the blade inlet angle,and the blade wrap angle are systematically studied.The influence of the change of parameters on the hydraulic loss inside the guide vane and the hydraulic performance of the pump,the optimization measures for the hydraulic design of the anti-guide vane are clarified,in order to provide a certain theoretical reference and method guidance for the hydraulic design and performance optimization of the segmen tal multistage centrifugal pump.Firstly,with other geometrical parameters unchanged,only the axial width of the anti-guide vane is changed.The influence of the change of the axial width of the anti-guide vane on the hydraulic loss inside the guide vane and the hydraulic performance of the pump is systematically studied.The results show that the change of the axial width of the anti-guide vane in the range of b₅=（1.3～1.8）b₂ has no obvious influence on the hydraulic efficiency of the pump,taking the outlet width of the impeller as the reference.When the scheme b₅=1.7b₂,the loss is the smallest,and the efficiency of the pump is the highest,which is 0.33 percentage points higher than the original scheme,followed by the scheme b₅=1.4b₂,which is 0.16 percentage points higher than the original scheme.The drop of the pump is the largest,but it only reduces by 0.15 percentage points;the change of the axial width of the anti-guide vane has a greater impact on the lift than the efficiency.When b₅=1.7b₂,the pump lift is the highest,which is an increase of 0.57%compared with the original scheme,with the reduction of the axial width of the anti-guide vane,the head of the pump also gradually decreases.When b₅=1.4b₂,the head drop is 0.4%,and when b₅=1.3b₂,the head drops by 0.66%compared with the original scheme.The trend of rapid decline;comprehensively consider the influence of the change of the axial width of the anti-guide vane on the pump head and efficiency,and consider reducing the axial size of the pump as much as possible to improve the stability of the pump operation.The axial width of the anti-guide vane When b₅=1.4b₂ is the most reasonable axial dimension,the axial width of the anti-guide vane is reduced by 12%compared with the original scheme（b₅=1.59b₂）.In order to explore the influence of the relative position of the anti-guide vane in the circumferential direction on the hydraulic loss in the guide vane and the hydraulic performance of the pump,based on the original plan,the anti-guide vane was rotated around the Z axis along the rotation direction of the impeller at intervals of 7.5°.Once placed,a total of 6 groups of schemes are formed with the original scheme.The comparative analysis of the numerical calculation results of each circumferential arrangement scheme shows that changing the relative position of the inlet edge of the reverse guide vane and the outlet edge of the forward guide vane will affect the hydraulic performance of the pump,in the range of 7.5°～37.5°relative to the outlet edge of the vane,the hydraulic efficiency of the pump shows a trend of first decreasing and then increasing with the increase of the angle,and the hydraulic loss in the guide vane is related to the pump efficiency.The trend of change is just the opposite;when the inlet side of the anti-guide vane is placed at a 7.5°rotation relative to the outlet side of the positive guide vane,the hydraulic loss in the guide vane increases the most,which is 15.85%higher than the original scheme.The drop is also the largest,in which the head is reduced by 0.98%compared with the original scheme,and the efficiency is reduced by 0.54 percentage points;when the inlet side of the reverse guide vane is placed at a 30°rotation relative to the outlet side of the positive guide vane,the pump head and efficiency are all schemes.The only one among them is higher than the original scheme,in which the lift is increased by 0.47%and the efficiency is increased by 0.22 percentage points.At this time,the hydraulic loss in the guide vane is reduced by 6.43%compared with the original scheme.In order to reveal the influence of the blade profile design of the anti-guide vane on the hydraulic loss of the guide vane and the hydraulic performance of the pump,the Bezier curve is used to study the variation of a single variable from the curvature radius of the blade profile,the blade inlet angle and the blade wrap angle.The results show that the Bezier curve can improve the efficiency of the blade drawing of the anti-guide vane;when the inlet and outlet angles and the blade wrap angle of the blade are kept constant,the irregular change of the curvature radius of the blade profile along the flow direction can cause the inside of the guide vane to change.The hydraulic loss of the guide vane increases,resulting in a decrease in the lift and efficiency of the pump;keeping the outlet angle and wrap angle of the vane unchanged,and appropriately increasing the inlet angle of the vane can reduce the hydraulic loss in the guide vane,which is conducive to improving the hydraulic power of the pump efficiency;keep the inlet angle and outlet angle of the blade unchanged,and appropriately reduce the size of the blade wrapping angle,which can reduce the hydraulic loss in the guide vane,and at the same time can improve the pump head and efficiency.Finally,on the basis of b₅=1.4b₂,the optimal values of the relative position of the inlet side of the anti-guide vane,the blade inlet angle and the blade wrap angle are combined to design the optimal values of the three geometric parameters.Compared with the scheme,there is almost no change,and the maximum difference of each performance parameter does not exceed 0.04%;although the efficiency of the pump has not improved,the pump head has not decreased,and the axial width of anti-guide vane is reduced by nearly 12%compared with the original scheme,which can significantly improve the stability of pump operation and achieve the optimization goal.