Analysis Of Radial Force On Large Double-suction Centrifugal Pump

In this paper,the s700-500-730 double suction centrifugal pump produced by a factory is taken as the research object.In the process of its use,the double suction centrifugal pump has some faults such as vibration,shaft bending and even shaft breaking,which cause trouble to the safe operation of the pump station.After analysis,it is concluded that the fault is caused by the excessive radial force of double suctio n centrifugal pump during operation.Therefore,on the premise that the external factors(casting materials,processing technology,operating environment and operating medium)remain unchanged,this paper explores the influence of volute section area law,blade arrangement and blade wrap angle on the radial force of impeller part of centrifugal pump.The main work and results of the thesis:1.Comparing the simulation value data of the external characteristics of the centrifugal pump with the test data provided by the manufacturer,the reliability o f the simulation calculation is verified,and the steady flow and transient flow fields o f the original model pump are analyzed to lay the foundation for subsequent research.2.On the basis of the volute section area law(hereinafter referred to as Y-law)adopted in the original model,the L-law with linear change of volute section area,the N-law with convex rise change and the U-law with concave rise change are put forward.The results show that under the condition of full flow,the spiral case designed by Y-law has better hydraulic performance than other schemes.As far as the steady-state radial force is concerned,under the design conditions,the radial force value of the Y-law scheme is 28.7%larger than the radial force value of the L-law scheme,and the absolute value of the radial force of the smaller flow is greater.Finally,compared with other schemes,the spiral case designed with L-law can effectively improve the pressure fluctuation inside the spiral case and balance the radial force acting on the impeller,reduce the possibilit y of vibration of the centrifugal pump,and improve its operation stability.3.Through the simulation calculation and analysis of the three schemes of blades using symmetrical arrangement,staggered 15°arrangement,and staggered 30°arrangement,it can be concluded that overall,compared with the symmetric arrangement,the staggered arrangement of the blades will cause the centrifugal pump The hydraulic performance is reduced.At the same time,compared with the symmetrical arrangement scheme of the blades,the staggered arrangement scheme o f the blades can effectively reduce the steady-state radial force value and the transient radial force pulsation amplitude on the impeller,and improve the pressure pulsation in the volute.Among them,the relative reductions of the radial forces at staggered30°under the working conditions of 0.8Q_d,1.0Q_d and 1.2Q_d are 10.822%,22.311%,and 20.356%.It can be seen that,within the allowable range of head and efficiency of centrifugal pump,the arrangement of blades is changed to a staggered 30°arrangement,which can effectively improve the radial force characterist ics of the impeller and improve the stabilit y of the centrifugal pump operation,reduce the occurrence of vibration or even shaft break fault.4.On the basis of the original model blade wrap angle of 130°,two schemes o f blade wrap angle of 120°and 110°are proposed.Through the simulation calculatio n and analysis of each scheme.The results show that:the head of centrifugal pump decreases with the increase of wrap angle.As the operating flow rate increases,the efficiency of the centrifugal pump increases with the increase of the wrap angle,but when the operating flow is too large,the efficiency of the centrifugal pump decreases with the increase of the wrap angle.At the same time,as the wrap angle increases,the steady-state radial force acting on the impeller decreases.At last,there is an optimal value for the wrap angle of the blade to minimize the pressure pulsatio n amplitude and the transient radial force pulsation amplitude in the volute.Based on comprehensive consideration,it is most appropriate to choose the blade wrap angle of 130°for the s700-500-730 double suction centrifugal pump studied in this paper.