Simulation Analysis And Experimental Verification Of Hydraulic Performance Of Large Centrifugal Pumps

Centrifugal pumps as a general fluid machinery and equipment is widely used in various fields such as urban water supply,water conservancy projects,petrochemical,aerospace.In recent years,with the development of the economy and society,there has been a higher demand for centrifugal pump characteristics in the field of water transfer projects,pumped storage and large units of nuclear power generation.In view of the high flow and high head(high specific speed)centrifugal pump units used in these fields are more powerful and place higher demands on unit efficiency and vibration.Therefore,the optimisation of centrifugal pumps of conventional design to improve their hydraulic characteristics has attracted the attention of many scholars.Traditional centrifugal pump design methods can use existing excellent models as well as experience to design hydraulic models,but due to individual experience differences or different selection of formula coefficients,the design of centrifugal pumps often can not reach the optimal state.Therefore,it is important to improve the traditional design methods and optimise the hydraulic components of centrifugal pumps so that they can achieve efficient,safe and stable operation.In the centrifugal pump design stage to give full play to computer computing efficiency and numerical simulation capabilities,not only can improve the efficiency of centrifugal pump optimisation,but also shorten the development cycle and reduce research and development costs.At the same time,numerical simulation can also visualise the internal fluid flow state of centrifugal pumps and solve problems such as head,efficiency and pressure fluctuations from the study of hydraulic characteristics.Therefore,this paper examines centrifugal pumps from the following three aspects,as follows:(1)Influence of the number of blades on the hydraulic performance of impellersFirstly,the influence of the number of blades on the movement of the impeller internal flow field was analysed by means of "constant calculations",using impellers with different numbers of blades(5,6,7 and 8)as the object of study.By studying the fluid pressure distribution,velocity distribution and vortex distribution inside the impeller,the law between the impeller characteristics and the number of blades was investigated.Numerical calculations are also carried out for the external hydraulic characteristics of the impeller.(2)Influence of the number of vanes on the hydraulic performance of centrifugal pumpsThe radial type guide vane model was optimally designed according to the impeller parameters.The influence of the number of guide vanes on the overall hydraulic characteristics of the hydraulic model was analysed by using the control variable method to ensure that the geometric parameters of the hydraulic model remain unchanged and only the number of guide vanes is changed.At the same time,the model was optimised by numerical simulation results.Finally,performance tests are carried out on the optimised hydraulic model to verify the accuracy of the optimised model parameters and the optimisation method.(3)Influence of tip clearance on the hydraulic performance of centrifugal pumpsA simulation approach was used to investigate the effect of the leaf top clearance on the performance of the hydraulic model.The distribution patterns of the pressure field,velocity field,vorticity and external characteristics of the fluid inside the hydraulic model are analysed.The effect of the clearance on the internal pressure pulsation of the hydraulic model was investigated by means of ’non-constant calculations’.Finally,the hydraulic model was optimised according to the simulation analysis,and the optimised hydraulic model was tested and verified.The test results are in general agreement with the simulated data.