【作者】 芦逸云；

【导师】 王家素；

【作者基本信息】 西南交通大学 ， 电工理论与新技术， 2009， 博士

【摘要】 自从1986年发现了可以工作在液氮温区的YBCO高温超导体以来,世界上许多科学家纷纷对其表示了极大的兴趣并投入大量的精力进行研究,使得高温超导体的性能不断提高,为其在工程方面的应用开辟了广阔的前景。由于YBCO高温超导块材拥有较强的磁通钉扎能力而具有自稳定的悬浮特性,因此具有巨大的应用潜力。本研究小组对高温超导磁悬浮列车系统进行了大量的研究工作,并于2000年12月31日研制成功世界首辆载人高温超导磁悬浮实验车。为了使高温超导磁悬浮车系统早日走向工程应用,系统地进行实验研究耗资巨大,所以,本论文提出了一种求解高温超导块材磁悬浮特性的三维数值模型,描述了该磁悬浮三维数值计算原理。本三维模型采用虚拟电导率的方法,将高温超导块材分为两种块材叠加来模拟超导块材内部的电流各向异性;论文中详细地描述了两种永磁轨道产生的轨道磁场的解析计算方法以及三维模型的数值求解过程,采用有限元方法结合时域差分法,使用迭代法处理非线性耦合问题。在FORTRAN平台上编写实现了高温超导磁悬浮三维数值模拟计算程序,同时实验验证了该程序的正确性。从而为高温超导磁悬浮车系统的悬浮性能数值模拟研究和优化设计提供了理论指导。通过三维仿真模型对高温超导磁悬浮车用永磁导轨上方高温超导块材电磁特性进行了模拟计算,研究了超导块材在沿永磁轨道无限长方向垂直面内对称外磁场中的端面效应。该研究揭示了由于超导块材端面效应的存在,虽然外磁场在永磁轨道无限长方向磁场分量为零,但是超导块材内部沿此方向的磁场分量不为零,这是目前世界上二维超导磁悬浮计算所不能做到的。使用实验与数值计算相结合的方法,研究了高温超导块材在对称分布式永磁轨道和Halbach结构永磁轨道上方悬浮力特性。实验研究和数值计算了在对称分布式永磁轨道下,高温超导块材悬浮力磁滞回线与超导块材横向水平偏移量之间的关系;最大悬浮力与超导块材横向水平偏移量之间的关系。在Halbach结构永磁轨道下,悬浮力磁滞回线与超导块材横向水平偏量之间的关系;最大悬浮力与超导块材横向水平偏移量之间的关系。研究结果表明,悬浮力磁滞回线以及最大悬浮力与块材横向水平偏移量之间的关系与外磁场结构紧密相关;模拟计算和实验结果能够较好的吻合。通过三维仿真计算,研究了高温超导磁悬浮列车系统几何参数和物理参数对悬浮性能的影响。对于对称分布式永磁轨道,高温超导磁悬浮性能随着轨道横截面厚度的增加和宽度的增加而在一定范围内增加,当永磁轨道横截面积一定时,与永磁轨道的宽度与高度的比值紧密相关。对于Halbach结构永磁轨道,高温超导块材的磁悬浮性能比较复杂。在轨道其它参数保持不变的情况下,高温超导磁悬浮性能随着主磁体宽度的增加不仅取决于主磁体宽度与聚磁体宽度的比例,还与主磁体宽度与永磁轨道的高度的比例相关。高温超导磁悬浮性能与聚磁体宽度之间的关系和主磁体宽度与聚磁体宽度的比例值、主磁体宽度与永磁轨道的高度的比例值密切相关。通常上述各比例数值一定的情况下,永磁轨道横截面积的增大能够在一定范围内提升悬浮性能。通过仿真计算了对称分布式永磁轨道上方高温超导块材在不同临界电流密度下的悬浮力曲线、Halbach结构永磁轨道上方高温超导块材在不同临界电流密度下悬浮力曲线,得出超导块材临界电流密度对超导体磁悬浮性能的提升,与外磁场结构有着密切的关系。单纯的提升超导块材材料性能,未必能达到优化磁悬浮性能的最终目的。更多还原

【Abstract】 The discovery of high-temperature superconductors (HTS) in 1986 and YBCO in 1987 made HTS operable at temperatures within the cooling capabilities of liquid nitrogen. Ever since, many scientists have expressed great interest in HTS phenomena and its potential applications and have done a lot of research, for example, YBCO can be argued to be the most studied material in the world. Hence, performance in HTS is constantly improved, making its applications in engineering easier and more realistic. Given the fact that HTS, more specifically YBCO bulks, have a strong flux pinning effect, the stability of the its levitation above a permanent magnet (PMG) can be achieved without any complex control systems making bulk superconductors have great potential. Our research group has performed a lot of research on HTS maglev vehicle systems and was successful in developing the first man-loading HTS maglev test vehicle in Dec 31, 2000.In order to promote the application of the HTS maglev vehicle system in engineering applications, a 3D-modeling numerical solutions of electromagnetic behavior of HTS bulk is given in this thesis. In this 3D-modeling, the virtual conductivity method is used; two virtual superconductors were taken in nestification to simulate the anisotropic property of the current density in the interior of the HTS bulk. The magnetic flux density on two different types of PMG were calculated and analyzed with this method. Iteration methods were used to resolve the nonlinear coupling problem. The resolved code of the 3D-modeling of the HTS Maglev was developed using the FORTRAN language. The results of the work presented provide important scientific theories for the optimum design and numerical simulation of HTS Maglev vehicle systems.The magnetic behavior of an HTS bulk over a symmetric PMG was computationally simulated with the mentioned 3D-modeling. The results show that the component of the magnetic field, H_z, is not equal to zero because of the terminal-face affection of the limited size of the HTS bulk even though the component of H_z of the external magnetic field generated by the PMG does not exist. This simulation result is different than most HTS maglev magnetic behavior over a PMG in 2D-modeling from other reports.The magnetic levitation behavior of the HTS bulk over the symmetrical PMG and a PMG with a Halbach array was studied by numerical simulation and experimental methods. The relationship of the magnetic levitation curve of the HTS bulk with the lateral displacement over the symmetrical PMG and the Halbach PMG was investigated. The relationship of the maximum value of the magnetic levitation of the HTS bulk over the two types PMG with the lateral displacement is also was studied. The experimental and computational results are in good agreement with each other.Furthermore, influences of the symmetry geometry and physical parameters of the HTS maglev system to the magnetic levitation behavior was studied by 3D-modeling numerical simulation. For a symmetrical PMG, the behavior of the magnetic levitation is enhanced with the increase of the height and width of the PMG For the Halbach PMG, the behavior of the magnetic levitation of HTS bulk is complicated. The enhancement of the magnetic levitation of the HTS bulk not only depends on the proportionality of the main permanent magnet’s (PM) width with the PM assembly but also depends on the proportionality of the main PM width with the height of the PMG There is strong correlation between the magnetic levitation behavior of the proportionality of the main PM with the width assembly and the proportionality of the main PM width with the height of the PMG When the above mentioned proportionalities are kept constant, an increase of the cross-sectional area can enhance the magnetic levitation behavior to within a certain range.The magnetic levitation curves of the HTS bulk over the symmetrical PMG and the Halbach array PMG are calculated with 3D-modeling at different critical current densities. The simulation results show that the critical current density can improve the magnetic levitation force, but it is also tightly related to the external magnetic field. Simply improving the critical current density of the HTS samples may not always optimize the magnetic levitation behavior of the HTS maglev system.更多还原