Experimental Investigation And Numerical Calculation On High Temperature Superconducting Maglev Based On A Permanent Magnetic Guideway

It was found that a bulk high temperature superconductor (HTS) can stably levitate above or suspend below a permanent magnet soon after the discovery of superconductors which work at the liquid nitrogen temperature. Since then, much work on HTS Maglev has been done. Our group also did a lot of research on HTS Maglev and successfully developed the first man-loading HTS Maglev test vehicle at the end of 2000. Up to now, only little research on HTS Maglev vehicle was done by other groups except ours. For the further study on HTS Maglev vehicle, levitation characteristics of a HTS above a permanent magnetic guideway were investigated by both the experimental and the numerical methods based on our original experimental research in this dissertation, whose aim is to understand the interaction between a HTS and the permanent magnetic guideway and to provide corresponding experimental bases and theoretical studies.The levitation force and the lateral force are not only two characteristic parameters disclosing levitation characteristics of a HTS but also two important parameters for the design of HTS Maglev vehicle. First, the levitation force and the lateral force of a HTS above a permanent magnetic guideway were investigated by the experiments in this dissertation, then the research was extended by a numerical computation.In the experimental research, the levitation force of a HTS above a permanent magnetic guideway was first investigated in the case of zero-field cooling. The hysteresis of the levitation force curve and the interaction between a HTS and the applied magnetic field were explained by the Bean model, and the effect of the measuring precess on the levitation force was further analyzed. In addition, the relationship between the levitation force and the magnetic field were investigated. As for the levitation force and the lateral force of a HTS above the permanent magnetic guideway in the case of field cooling, the research focused on the effect of the cooling height on the levitation force and the lateral force and the relationship between the levitation force and the lateral force. Then the research of the effect of the size and the thickness of a HTS on the levitation force and the lateral forcetogether with the levitation force and the lateral force of a ring-shape HTS were followed above the permanent magnetic guideway. Finally, the effect of the interaction among HTS on the levitation force and the lateral force was investigated.In the numerical computation, a two-dimensional numerical method integrating finite element method and difference method was employed, where the finite element method is used to calculate the magnetic field of the permanent magnetic guideway and the difference method is used to calculate the induced current in the superconductor, then the levitation force and the lateral force were calculated by Lorentz formula. Both the field dependence of the critical current density and the anisotropy of a HTS were considered in this method. The levitation force and the lateral force of a HTS above the experimental permanent magnetic guideway were calculated by this method. Numerical results proved a series of phenomena in the experiments and agree well with the experimental results. Furthermore, some research that is difficult or unable to be done by experiments was carried out by the numerical computation, such as the effect of critical current density, the width and the thickness of a superconductor, the maximum lateral displacement, the interaction among superconductors and the concentration width of the permanent magnetic guideway on the levitation force and the lateral force and the levitation force distribution on the cross section of a HTS. These numerical results together with the experimental data provide important theoretical bases for the research and engineering applications of HTS Maglev vehicle.