兰州大学机构库 >土木工程与力学学院
高温超导悬浮体面内移动时的静力特性研究
Alternative TitleA Study on the Static Characteristics of High-temperature Superconducting Levitation Body When Lateral Traversing
杨勇
Thesis Advisor郑晓静
2007-05-10
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name博士
Keyword圆柱形高温超导体 矩形永磁体 磁通冻结-镜象模型 竖向移动镜象磁偶极子 面内移动镜象磁偶极子 解析表达式 临界态模型 数值模拟 悬浮力 面内力 竖向刚度 面内刚度 交错刚度 临界初始冷却高度 悬浮系统参数
Abstract

在近二十年来,由于高温超导体在飞轮储能和磁浮轴承等方面的广泛应用而使得高温超导体和永磁体之间的相互作用越来越引起研究者的关注。目前,有关悬浮体受力的研究状况是:实验探索多于理论分析,悬浮力研究多于面内力研究。本文针对典型的高温超导-永磁悬浮系统,对悬浮体受到的力做了较为全面的研究,尤其是对磁通冻结-镜象模型的修正以及对悬浮力和面内力的数值模拟,得到了一些有意义的结果。本文对磁通冻结-镜象模型进行了修正。通过引入竖向移动镜象磁偶极子和面内移动镜象磁偶极子,得到了一个磁偶极子悬浮于半无限超导体上方时受到的悬浮力和面内力的解析表达式。修正后的模型可以给出零场冷却下永磁体受到的面内力以及悬浮力曲线和面内力曲线上的磁滞特性,这是磁通冻结-镜象模型所不能反映的。根据修正后的模型,得到永磁体竖向移动时竖向刚度的解析表达式以及面内移动时面内刚度和交错刚度的解析表达式,研究了永磁体在任意位移下受到的面内力和悬浮力,并利用电流环之间的相互作用力公式定量计算了永磁体相对于超导体竖向移动时的悬浮力以及面内移动时的悬浮力和面内力。
本文对悬浮体受到的力进行了数值模拟。推导出矩形永磁体磁场分布的解析表达式,并将其推广到 n 块永磁体颠倒磁极并在一起时的情形,据此分析了一到三块永磁体外部空间磁场分布的主要特征。依据电流矢势法和有限元法建立了分析超导电磁场分布、静态悬浮特性的数值计算方法,通过与实验结果比较验证了该方法的可靠性。数值模拟永磁体受到的悬浮力、面内力和静磁刚度,结果显示移动历史对悬浮体受到的力和刚度有显著的影响。本文研究了悬浮体受到的面内力与超导体的初始冷却条件的关系,提出了高温超导悬浮系统面内稳定的临界初始冷却高度 zc0的概念。当初始冷却高度小于临界初始冷却高度 zc0时,面内力和面内位移方向始终相反,面内力为面内稳定悬浮的恢复力;当大于 zc0时,面内力有可能和面内位移方向一致,导致面内悬浮不稳定。本文讨论了超导体的初始冷却条件、磁体的表磁强度、超导体临界电流密度、永磁体面内移动时的悬浮高度、永磁体和超导体的面积比和厚度比等悬浮系统参数对永磁体面内移动时所受到的悬浮力、面内力的影响以及对临界初始冷却高度 zc0的影响。

Other Abstract

The interaction between a permanent magnet (PM) and a high temperature superconductor (HTS) has drawn researchers’ attention for the last nearly twenty years because of the possible applications of HTSs, such as flywheel energy storage systems and magnetic bearing systems. Now, in the study of the vertical and lateral forces, the experimental researches are more than the theoretical ones, and also the researches on levitation force are more than these on lateral force. In this paper, for a typical superconducting levitation system composed of a HTS and a PM, the vertical and lateral forces are considered, and then the some very useful results are obtained from modification of the frozen-image method and simulation of the vertical and lateral forces.
The frozen-image method is modified. The exact solutions are obtained for the point magnetic dipole over a flat nonideal type-II superconductor using of the vertical and horizontal movement images. Comparing with the frozen-image method, our method can give the lateral force in zero field cooling and the hysteresis in the vertical and lateral forces. The two characteristics can not be obtained by the frozen-image method. In this case, the vertical stiffness during vertical traverses and the lateral and cross stiffnesses during lateral traverses are obtained by the analytic expressions of vertical and lateral forces. The vertical and lateral forces are obtained by the modified frozen-image method when the PM moves arbitrarily. The levitation force during vertical traverses and the lateral and vertical forces during lateral traverses are recalculated by the modified frozen image method and the equivalent current loops for all images.

The vertical and lateral forces are simulated. A set of analytic expressions of magnetic field distribution are derived, not only for one rectangular PM bulk, but also for n rectangular PM bulks arranged by alternating north pole and south pole of the magnet. The major characteristics of magnetic filed produced by one, two or three PM bulks are analyzed. The finite element method and the current vector potential are adopted in the simulations. The numerical methods which can be used to deal with the electromagnetic field of HTS, static levitation characteristics are established. By comparing the numerical results with experimental data, the numerical methods are validated. The vertical and lateral forces, static magnetic stiffnesses are simulated. The calculations show that those forces and stiffnesses are significantly influenced by the movement history. In this case, the relationship between lateral force and initial cooling condition is investigated. A concept of transition cooling height ( zc0 ) is given. The levitating body is laterally stable when the initial CH is less than zc0 , whereas, when CH is more than zc0 , the levitating body is possibly laterally unstable. The effects of the physical parameters, the levitating height during lateral traverses and the dimensions of the system on the transition cooling height and the vertical and lateral forces are presented

URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226412
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
杨勇. 高温超导悬浮体面内移动时的静力特性研究[D]. 兰州. 兰州大学,2007.
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