The Structural Design And Performance Analysis Of The Single Stage Canned Motor Pump

The canned motor pump unit is an important auxiliary equipment of nuclear power plants,but it is limited by foreign technology.Therefore,the independent design of the safe and reliable operation of single stage canned motor pump which is satisfied with the high standard requirements for nuclear power is of great significance to enrich our relevant product structure and provide technical support for the vigorous development of the nuclear power industry.Based on the construction of No.3 unit of a nuclear power plant,the structural design of the single stage canned motor pump is carried out.The performance of the canned motor pump is optimized by three-dimensional numerical simulation and experimental tests.This thesis introduces the working principle and structure classification of the canned motor pump in detail,combined with the research status and development trend at home and abroad,using the speed coefficient method to hydraulically design the impeller and pump body of the 50-32-160 single stage canned motor pump.The strength and rigidity of each pressure-bearing component are calculated by the formula in the RCC-M standard,and the results all meet the standard requirements of the nuclear power pump,thus ensuring the reliability of the pump operation.The three-dimensional geometric model of 50-32-160 type single stage canned motor pump is built by CREO software.ICEM is used to make grid division of the 3D model.Then ANSYS Fluent software is used to perform three-dimensional steady numerical simulation of the whole flow field inside the canned motor pump and the performance curve and internal flow characteristics of this 50-32-160 canned motor pump are obtained.The parameters such as head and efficiency predicted by numerical simulation are basically consistent with the variation trend of experimental test results,which accurately reflects the flow condition of the medium in the pump.In this thesis,the 0.6,1.0,1.2 times of rated flow points are simulated respectively.The flow rate and pressure distribution of the blade face,blade back and the volute in the three different conditions are obtained.The performance of the canned motor pump is analyzed.The pressure on the working face of the impeller is higher than that on the back under the three kinds of working conditions.And the position of water inlet edge on the blade back,which is close to the blade rim becomes the most often place to produce cavitation.The fluid increases gradually along the radial direction of the blade,and the blade face velocity at the same radial position is always greater than the blade back.The maximum pressure occurs at the outlet of the volute.There is partial impact in the volute tongue,and the fluid velocity in the volute decreases gradually.Especially when the fluid flows to the diffusion zone of volute,the decreasing amplitude of velocity increases obviously.The fluid velocity reduce to the minimum value when it get to the outlet of the volute,because the fluid converts some kinetic energy into pressure energy.This thesis improves the structural design of the single-stage canned motor pump.According to the problems existing in the actual operation of the pump,a certain number of gusset plates are welded to the inner wall of pump casing surface to complete optimization.Compare the static pressure on the impeller front cover of before and after optimization by simulation result,it proves that the gusset plates welded to the inner wall of pump casing have an obvious effect on the axial force balance.So it is useful to improve the operation stability and increase the life of the single stage canned motor pump.