Retrofit Design And Hydraulic Performance Analysis Of The Long-Shaft Centrifugal Pump

Vertical long-shaft centrifugal pump(hereinafter referred to as " long-shaft pump")has the characteristics of long axial dimension and short radial dimension.In recent years,there are some researches of the long-shaft pump,but most of them are focus on the impeller performance optimization.However,due to the long shaft of vertical long-shaft pump,besides the impeller,the influence of other flow components on the hydraulic performance of the pump can't be ignored,such as space guide vane and guide bearing and bell mouth support,optimization of these components have great significance on pump's internal flow promotion and efficiency enhancement.Based on the above research background,this paper use the CPLC type vertical long-shaft pump as the research object,its space guide vane,guide bearing and bell mouth were investigated and optimized to realize the optimal overall performance of the pump.The efficiency of long-shaft pump with the space guide vane is lower than that with the volute,and its high efficient area is narrow,which causes a large waste of energy.It is reported that the space guide vane causes the biggest hydraulic loss which is 40% ~ 50% of the total hydraulic loss in the pump.Therefore,investigation and optimization of the space guide vane is one of the main research tasks of this project.In this paper,we firstly studied the effect of three important parameters on the performance of guide vane,including exit angle,inlet angle and angle,this work is aimed to provide the basis for the design of space guide vane.Then we used the orthogonal experiment method to optimize the space guide vane,the results were analyzed to characterize the effect of each parameters on the performance of the space guide vane,and parameters for achieving optimal performance of the whole pump were find based on the analysis results.Guide bearing is an important structure parts of the long-shaft pump,it places in the pump's discharge pipe and supports the pump's shaft.In this paper,we investigated the influence of the guide bearing on the inner flow of the pump.Parameters of the guide bearing including the thickness of the support,axial plane projection shape,import settling angle and the number of the support were optimized based on the designing method of rear guide vane.The results show that the optimized guide bearing causes less hydraulic loss and eliminates the outlet circulation of the pump.Bell mouth is used to lead the water in suck pool directly into the of the entrance impeller.For the CPLC type vertical long-shaft pump,the bell mouth support is located inside of the bell mouth to support shaft better,and reduce the vibration of the pump unit.In this paper,we investigated the effect of the bell mouth support on the hydraulic performance of the pump from three aspects including the external characteristic,internal flow characteristics and pressure fluctuation characteristics.The results show that the bell mouth support increases hydraulic loss and water flow velocity and lowers the pressure inside the bell mouth.Besides,Noise interference was found between the impeller and the bell mouth support.Overall,the bell mouth support has little influence on the hydraulic performance of pump.