Study On Multifield And Mechanics Behavior Of Inserted No-insulation HTS Coil For Hybrid Magnets

The large high field magnets are the key and fundamental equipment for many scientific and high-tech applications,such as,material science,particle physics,medicine imaging,new energy and new transports et al,which has extensive and important application prospects.High temperature superconducting materials provide one powerful way to support for superconducting magnets to obtain the magnetic field intensity over 25 T and for hybrid magnet to acquire the stronger magnetic field intensity.The no-insulation(NI)high temperature superconductor(HTS)coil technology improves the thermal stability of HTS magnet and solves the difficulty of HTS coil quench protection.However,the hybrid magnet has complex structure,and electromagnetic and mechanical characteristics of NI HTS coil also become complex due to the interaction between inserter and outer magnets,the structure of the magnet is prone to large deformation and damage under multi-physics field,which has become an important and basic subject in the design,preparation and operation of high field magnets,precise mechanical analysis and comprehensive analysis of multi-physics field are needed to improve the stability and safe estimate of hybrid magnet.This thesis focuses on some mechanical issues and characteristics of multi-physics field of the inserter NI HTS coil in a hybrid magnet under the normal operational environment,a numerical model was established and a quantitative analysis method was used to simulate the mechanical behavior of NI HTS coil under multi-physics field coupling.At first,based on the circuit analysis,magnetic field analysis of hybrid magnets and temperature and mechanical analysis of NI HTS coil,we established the electricmagnetic-thermal multi-physics field model of NI HTS coil,which is the theoretical basis for the numerical simulation research.Secondly,we neglected the effect of temperature on NI HTS coil,and conducted the study on of the mechanical behavior and characteristics of NI HTS coil by using the finite element numerical simulation.The results indicated that the stress and strain responses of the NI HTS coil is closely related to the charging and discharging processes of the outer magnet,which is basically consistent with the current variation mode.The stress distribution is significantly different along the different directions,hoop and radial stresses are dominant,the hoop stress and radial stress are three orders of magnitude larger than the shear stress.While the parameters analysis of NI HTS coil indicates that the stress state of NI HTS coils will enhance with increasing of the inner radius and operational current of NI HTS coil,as well as accelerating the charge rate of outer coil.Additionally,the mechanical boundary influences the stress distribution of NI HTS coil and should be paid an attention in the magnet design.Finally,we synthetically considered the effect of electric-magnetic-thermal multiphysical field coupling and carried out the numerical study on the multi-physical and mechanical behavior of NI HTS coils,the effect of pre-existing crack on stability of NI HTS coil was also considered.The results included that NI HTS coil keeps the excellent thermal stability during the charge and discharge of the outer coil,the total coil is heated by induced current that increases resistance of NI HTS coil and improves the ability of preventing change of current of NI HTS coil;the hoop stress is dominated by temperature,and the radial stress is dominated by electromagnetic body force.The preexisting defects increase the temperature of NI HTS coil,resulting in a decrease of critical current and the hoop current being at over-current state,if a faster charge or discharge rate is applied,the NI HTS coil would quench integrally.In this thesis,the multi-physical field behaviors of the core component of the inserter superconducting coil in the hybrid superconducting magnet were simulated in the view of multi-physical field and mechanics.Some electromagnetic characteristics,the quantitative results and rules of mechanical behavior were obtained during the charging and discharging process of the outer coil.It will provide certain theoretical guidance for the design and analysis of the high-field HTS magnets.