Research On Temperature Sensitivity Of High Temperature Superconducting Bulk And Its Monitoring System

High temperature superconducting(HTS)pinning maglev train has been developed for more than 20 years.During the development period,world-wild research institutes continue to join the development of the transport system.The development of any means of transportation bears the brunt of operation safety.The safety of HTS pinning maglev train first depends on the pinning performance of superconducting bulks,and its pinning performance depends on the temperature of superconducting bulks.Therefore,it is important for the safe operation of superconducting pinning maglev train to pay attention to the temperature evolution behavior and temperature sensitive region of superconducting bulks and establish the safety monitoring method related to the temperature of superconducting bulks.Taking safety as the foothold,this thesis gradually promotes the relevant research based on the actual engineering needs.Firstly,the change of surface heat flux of superconducting bulk in liquid nitrogen environment is taken as the starting point.The program of inversion method of heat transfer problem is compiled by MATLAB software.Temperature measurement is brought into it to inverse the change of surface heat flux density of superconducting bulk when it is cooled,which provides conditions for the analysis of temperature sensitive area of superconducting bulk and the establishment of coupling simulation model.Secondly,combined with the maglev high-speed operation simulation test-bed and temperature detection system,the temperature distribution and temperature sensitive area in the superconducting bulk are explored through experiments.Through the heat transfer equation,the heat taken away by the surface heat flow of the superconducting bulk is calculated,so as to obtain the temperature distribution of the superconducting bulk under adiabatic conditions and the approximate AC loss under a certain operating time.It is found that the temperature distribution of the superconducting bulk is uniform in the ab plane,but there is an obvious temperature gradient along the c-axis.The temperature sensitive area is near the permanent magnet.The research results provide a reference for the sensor installation position of the temperature monitoring system.Thirdly,taking the calculated surface heat flux as the thermal boundary condition and considering the anisotropy of superconducting bulk thermal conductivity,the magneticthermal coupling and thermal-mechanical coupling simulation modules are built by relying on the magnetic field formula module and solid heat transfer module of Multi physical field coupling software.The temperature distribution law of superconducting bulk is mutually confirmed with the experimental results.The influence of the change rate of vertical magnetic field irregularity on the temperature and levitation force of superconducting bulk and the relationship between the average temperature in the domain,the temperature of temperature characteristic point and levitation force are studied.Finally,the advantages and disadvantages of the existing superconductor temperature detection schemes and the difficulties of liquid nitrogen level monitoring in Dewar are analyzed.Then,the magnetic float level monitoring system and feasible temperature detection scheme are proposed.The Lab VIEW program of liquid level detection system based on magnetic float and temperature monitoring system based on Temperature sensor are made.This part provides a preliminary foundation for the subsequent construction of a more perfect multiparametric performance monitoring system based on Dewar unit.