| The slanted axial pump device is one of the pump device types for large low-lift puming stations,which has the advantages of less civil engineering,good hydraulic performance of flow passage,good heat dissipation conditions and convenient pump maintenance,etc.,and has been applied in the construction of many low-lift puming stations.In recent years,the application of slanted axial pump device in low-lift pumping station research found that the flow rate of the left and right holes in the outlet passage with conventional length of the septum is not equal,and there is a serious water bias problem,which affects the stable and efficient operation of the slanted axial pump device.In order to study the water bias at outlet passage of slanted axial pump device,improve the flow pattern of outlet passage,improve the hydraulic performance of the pump device,this paper takes an slanted axial pump device with a pump shaft inclination of 20° as the study object.This paper takes a pump device with a pump shaft inclination angle of 20° as the study object,by changing different design parameters of the guide vane body(guide vane vane number S,guide vane length L and guide vane outlet angle β),and using the three-dimensional turbulent flow numerical simulation method,which has been tested in the pump device model,was used to study the effect of the variation of the design parameters of the guide vane body on water bias and the performance of slanted axial pump device,and obtains the following study results:(1)The water bias in the outlet passage of slanted axial pump device is serious due to the combined effect of the remaining loop volume of the water flow at the outlet of the guide vane body and the "S" shaped curved section of the outlet passage of slanted axial pump device,which uses a conventional length septum outlet passage of slanted axial pump device.The water bias in the outlet passage of the slanted axial pump device is serious due to the combined effect of the remaining loop volume at the outlet body and the "S" shaped curved section of the outlet passage of the slanted axial pump device,and a new idea to reduce the water bias at the outlet passage is proposed:change the design parameters of the guide vane body to reduce the remaining ring volume of water flow at the outlet of the guide vane body,and then improve the outlet passage flow pattern to reduce the water bias coefficient of the left and right holes.(2)Under the guide vane outlet angle β=90.0° and blade length L=0.42D(D is the impeller diameter 3.65m)unchanged,the numerical simulation of the three-dimensional flow of the slanted axial pump device was carried out for 5,6,7,8 and 9 guide vanes with 5 guide vanes respectively,and the results showed that:the number of guide vane S of slanted axial pump device increases,the head loss of the guide vane increases gradually,and the head loss of the outlet passage increases gradually,the water bias coefficient λ decreases from 1.725 to 1.510 and the extent of water bias at outlet passage decreases,the head loss of outlet passage is reduced from 0.422m to 0.320m;the efficiency of pump device ηzz increases with the increase of the number of guide vanes and then decreases slightly,and the highest efficiency of pump device is 77.77%when S=7.(3)Under the condition that the number of guide vanes S=7 and the outlet angleβ=90.0° unchanged,five guide vane schemes were designed and numerical calculated within the length of the guide vane casing with the guide vane length L gradually increasing from 0.42D to 0.54D,and the results showed that:increasing L,the head loss of the guide vane gradually increased but the magnitude was small,and λ decreased from 1.606 to 1.172,which greatly improved the water bias at outlet passage,the head loss in the outlet channel was reduced from 0.330m to 0.293m,and ηzz was increased from 77.77%to 78.65%.(4)Under the condition that the number of guide vanes S=7 and the length of the vanes L=0.42D unchanged,nine guide vane schemes with the outlet angle of guide vane βgradually increasing from 85° to 105° are designed and numerical calculated,and the results showed that:λ decreases gradually as β increases,and λ approaches 1.0 when β=97.5°,and when β<97.5°,the flow in the outlet passage is leftward,and when β>97.5°,the flow in the outlet passage is rightward.;with β increases,the guide vane body head loss gradually increases,outlet passage head loss is first reduced and then increased the trend of change,the pump device efficiency shows the trend of first increased and then reduced;when β=97.5°,P is close to 1,outlet passage in the flow pattern is good When β=91.5°,λ is close to 1,the flow pattern in the outlet passage is good,the minimum value of head loss in the outlet passage is 0.230m,and the maximum efficiency of the pump device is ηzz=80.05%.(5)A comprehensive analysis of the water bias at outlet passage of slanted axial pump device and the hydraulic performance of the three guide vane design parameters was carried out,and a relatively better optimized solution for the guide vane body was selected:S=7,L=0.42D,β=97.5°;the results of the calculation of the original versus the optimized solution for the pump unit at different flow conditions show that:the performance of the original scheme is better than the optimized scheme for small flow conditions,and the performance of the optimized scheme is better than the original scheme for large flow conditions,and the efficiency of the optimized scheme has increased by 1.08%compared with the original scheme.In this paper,the water bias at outlet passage of slanted axial pump device is effectively solved by adjusting the design parameters of the guide vane body in the slanted axial pump device.The problem of water bias at outlet passage of slanted axial pump device was solved effectively by adjusting the design parameters of the guide vane body in the slanted axial pump device,and the flow pattern of outlet passage was improved and the efficiency of the pump device was increased.The research results of this paper provide a new direction for the design and optimization of the slanted pump device,and can provide technical support for solving the problem of water bias at outlet passage of slanted axial pump device in low-lift pumping station,which has certain theoretical significance and important engineering application value. |
PDF Full Text Request