Study On Geometrical Parameters Optimization And Selection Of Two Water Inlet Forms Of Vertical Axial Flow Pump

There are usually two types of small and medium-sized vertical axial flow pump device water inlet forms:open suction sump and elbow-shaped inlet passage,and the influence of the geometric parameters of the suction sump and inlet passage on the pump performance can help the pump selection and pump station design.This paper takes the vertical axial flow pump device of Lingcheng pumping station as the research object,adopts the impeller diameter of 300mm axial flow pump hydraulic model,and carries out the model test and numerical simulation research on the two water inlet forms of vertical axial flow pump open suction sump and elbow-shaped inlet passage,and selects the suitable water inlet form of vertical axial flow pumping station through comprehensive comparison and analysis,and the research results can provide some reference for the inlet form selection and optimization design of vertical axial flow pump.Firstly,model tests were carried out for each of the two inlet forms of the pump unit respectively.Three kinds of floor clearance of bell mouth 0.598D_L,0.733D_LL and 1.033D_L were designed for the open suction sump,and suction vortex bands of varying intensity were observed for each operating condition during the test.The hydraulic performance of the pump unit was relatively stable at 0.598 D_L,with a maximum efficiency of 78.19%;the hydraulic performance at 1.033 D_L was unstable at large discharge conditions,with serious bottom vortex and wall vortex in the inlet pool at the same time,and the location of the vortex changed over time.The hydraulic performance of elbow-shaped inlet passage pump device is stable,the water flow in the flow passage is relatively smooth,the highest efficiency reached 78.54%.Then the orthogonal experimental design was used to optimize the two inlet forms respectively.Orthogonal test design was carried out for the four geometric parameters of the open suction sump:suction sump width B,rear wall distance T,floor clearance of bell mouth P_L and bell mouth length L_b.It was found that the factors affecting the hydraulic performance were in the order of L_b>B>P_L>T,and the optimal scheme was obtained through the comprehensive frequency method.The head and efficiency of the scheme are 5.58m and 81.45%respectively under design conditions.Orthogonal test design was carried out for the four geometric parameters of the elbow inlet passage:the height of the bottom from the impeller center,the width of the passage B,the height of the throat of the passage HKT and the length of the passage L.The calculation found that the factors affecting the hydraulic performance were arranged in the order of H_p>HKT>B>L,and the optimal scheme was obtained through the comprehensive frequency method.The head and efficiency of the scheme are 5.56m and 81.9%respectively under design conditions.Finally,unsteady numerical simulation is carried out for the pump device using the two optimal schemes.Through the analysis of pressure pulsation,it is found that in three typical flow conditions of 0.75Q_des,1.0Q_des and 1.2Q_des,the pulsation amplitude of each section of the open suction sump pump device is greater than that of the elbow-shaped inlet passage pump device.By comprehensive comparison,unsteady hydraulic stability of elbow-shaped inlet passage is better than that of open suction sump pump.In summary,the results show that the optimized vertical axial flow pump device can obtain better external characteristics and performance regardless of the use of open suction sump pump or elbow-shaped inlet passage,and the pump device with elbow-shaped inlet passage has slightly higher efficiency.The pump station with elbow inlet passage has smooth internal flow,and the passage width is 20%smaller than that of open suction sump.However,the open suction sump generally has vortex zones with different strengths,and the operation of the pump has potential safety risks.The stability of the pump is not as good as that of the elbow inlet passage Considering the lateral inlet of Lingcheng pump Station,it is recommended to adopt the elbow-shaped inlet passage.