Structural Optimization Analysis Of High Speed Axial Magnetic Bearings

The development of modern industry puts higher demands on the performance of rotating machinery.In order to pursue higher efficiency and greater power density,many industrial fields require higher and higher rotational speeds of the rotor,and even require it to work at supercritical speeds.At this time,ordinary mechanical bearings are often difficult to meet the rotational speed requirements.The active magnetic suspension bearing uses a controllable bearing force to support the rotor,eliminating mechanical contact and mechanical friction between the stator and rotor.It has many advantages,such as high speed,low frictional power consumption,no lubrication,and controllable stiffness and damping.It is widely used in high-speed centrifugal fans,compressors,machine tool spindles,artificial hearts,energy-powered rotating machinery,chemical rotating machinery.,food processing machinery and aerospace equipment.At present,magnetic suspension bearings have become a research hotspot in academia and industry,and are one of the ideal support bearings for high-end rotating machinery.Magnetic suspension bearing technology involves many disciplines such as mechanics,mechanics,rotor dynamics,electromagnetism,power electronics,control engineering,and computer science.Therefore,improving the performance of magnetic suspension bearings is a comprehensive project.The rational design and optimization of the magnetic suspension bearing structure is an important basic technology to improve its performance.For high-speed heavy-duty rotating machinery,it has the characteristics of high speed,large load and small volume.If the currently used E-type axial electromagnetic bearing is adopted,the thrust disk rotor has large diameter,large stress and easy damage,which brings certain challenges to the structural design of the axial magnetic bearing.Therefore,this thesis mainly studies the structural form improvement and structural optimization design method of axial magnetic bearings under high speed and heavy load.Based on the structure of the traditional E-type axial electromagnetic bearings,this paper improves the magnetic circuit model equivalent to the structure which considered the edge effect for the improved axial electromagnetic bearing structure,and gives the calculation formula of the bearing capacity of the bearing.The relationship between the structural design process and structural parameters.In order to further reduce the rotor disk diameter and bearing power consumption,a permanent magnet ring is introduced into the axial magnetic bearing to provide permanent magnet biasing force,and electromagnetic force is used to provide dynamic restoring force.An axial hybrid magnetic bearing is designed.Considering the edge effect,the equivalent magnetic field equivalent model and the electromagnetic magnetic circuit equivalent model of the axial hybrid magnetic bearing are established respectively,and the calculation formula of the bearing capacity of the bearing is derived.Under the principle of maximum energy product,the structural parameters of the biased permanent magnet ring are designed,and the relationship between structural design method and structural parameters is given.In order to optimize the structural parameters,thegenetic algorithm is adopted.and according to the relationship between the bearing capacity and the structural parameters,the minimum bearing size and the maximum bearing capacity are taken as the objective functions.and the structural parameters of the axial electromagnetic bearing and the axial hybrid magnetic bearing are respectively carried out.Optimize the design.Under the requirement of theoretical bearing capacity of 3000N.compared with tlhe thrust plate radius of traditional E-type axial electromagnetic bearing of 73.3mm.the optimized thrust axis of the modified axial electromagnetic bearing has a radius of 60mm.which is reduced by 18.1%.The rear axial hybrid magnetic bearing has a thrust disk radius of 50 mm.which is reduced by 31.8%,and the thrust disk diameter is greatly reduced.Based on the equivalent magnetic circuit method,the calculated bearing capacity of the axial electromagnetic bearing is 2953.5N,and the deviation from the incdex is-1.55%the calculated bearing capacity of the axial hybrid magnetic bearing is 1089N.and the deviation from the index It is 2.97%.which meets the bearing capacity design requirements.After the optimization design of the axial electromagnetic bearing and the axial hybrid magnetic bearing are completed,the ffm is used to simulate the two structures.The simulation value of the bearing capacity of the axial electromagnetic bearing is 3007N,and the simulation value of the bearing capacity of the axial hybrid magnetic bearing is 2992N,and the deviation from the bearing capacity calculated by the equivalent magnetic circuit method does not exceed 4%.And the deviation between the magnetic flux of each part of the axial electromagnetic bearing given by the equivalent magnetic circuit method and the finite element simulation is mostly below 5%,while the deviation of the axial hybrid magnetic bearing is slightly larger,below 10%,but the main magnetic pole The error of the magnetic flux is also below 5%,which indicates that the magnetic circuit model established in this paper has higher accuracy.The bearing capacity and magnetic flux density of the optimized magnetic bearing at different displacements of the thrust plate are simulated,and the relationship between bearing capacity and magnetic flux density and thrust disk displacement is further studied.The research shows that the axial magnetic bearing improved in this design can greatly reduce the diameter of the thrust plate while satisfying the high bearing capacity,and is more suitable for supporting the high-speed heavy-duty rotor.This paper lays a foundation for the development of high-speed,heavy-duty magnetic levitation rotating equipment,and has engineering value as well as theoretical significance.