兰州大学机构库 >土木工程与力学学院
高温超导复合带材的交流损耗及失超行为的数值分析
Alternative TitleNumerical analysis of AC losses and quench behaviors in HTS composite tapes
万星星
Thesis Advisor周又和
2016-05-28
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword高温超导体 H方法 交流损耗 失超
Abstract超导体处于交变电磁场中产生的交流损耗是其在实际应用中的关键问题。在低温环境下,交流损耗作为直接的热源输入整个超导设备中,不仅会增加制冷系统的负担,增大超导应用的成本,还会导致超导设备的运行不稳定。在超导磁体中,局部温升引起的失超及正常区域的传播也是实际应用中的安全隐患,在强电流环境下发生的失超甚至会对超导磁体产生毁灭性的损伤。 本文基于有限元数值方法,对高温超导复合带材的交流损耗和失超行为分别进行了研究。首先,分析了单层超导带材和堆叠结构中的交流损耗。基于幂指数E-J关系和H方法实现超导体建模,计算了不同交变电流、磁场的幅值、频率、相位差等条件下超导带材的交流损耗。通过比较高温超导带材和超导/铁磁基底复合带材的交流损耗分析了不同电磁场中磁性铁磁基底对高温超导带材交流损耗的影响。在低磁场环境下,磁性基底会增大超导带材内的交流损耗;而在高磁场环境下,磁性基底有减小超导带材交流损耗的作用。超导/铁磁基底复合带材的交流损耗在低磁场环境中随频率增大而减小,但在高磁场环境中交流损耗随频率增大先增大后减小。相位差等于90度时交流损耗最小,电流和磁场同相和反相时的交流损耗相等。磁性铁磁基底对多层堆叠的超导带材交流损耗的影响与单层带材情况相似。 其次,研究了堆叠的超导复合带材中的失超行为。考虑材料参数与温度之间的关系,结合热传导方程和麦克斯韦方程讨论了超导带材中的磁热耦合行为。当稳定运行的超导体受到局部热扰动时,超导带材的载流能力因产生的局部温升而减小,带材中的传输电流分流到铜稳定层内并产生焦耳热。绝热环境下,当铜稳定层中产生的焦耳热大于热传导的热量时,超导体中温度快速升高,超导层温度大于临界温度时,超导体转变到正常态,即超导体失超。铜稳定层产生的焦耳热使失超向外传播,直至整个导体完全失超。通过对比超导复合带材中超导层是否含有局部缺陷的计算结果发现,当一个超导复合带材的超导层中有局部缺陷时,超导体的临界电流减小,局部热源和缺陷之间的失超传播速度明显增大,并且失超在整个超导磁体中更快速地传播。
Other AbstractAs the superconductors are exposed to an alternating electromagnetic field, AC losses are an key issue to the practical application of superconductors. At the low temperature environment, AC losses is a direct source of heat for a superconducting device, which will not only increase the burden of the refrigeration system and increase the cost of superconductivity application, but also result in the instability of superconducting devices. In a superconducting magnet, the quench triggered by a local temperature rise and the spreading of the normal zone is the threats for its practical application. Due to running with strong current, the quench even results in a destructive damage for superconducting magnet. Based on the finite elment numerical method, the AC losses and quench behavior in high temperature superconducting (HTS) composite tapes are investigated, respectively. Firstly, we analyze the AC losses of single superconducting tape and a stack of tapes. The modeling of superconductor is based on the E-J power law and H-formulation. We compute the AC losses of HTS tapes in different electromagnetic field conditions, such as, thechanges of amplitudes, frequency and phase difference of alternating current and/or magnetic field. Comparing the AC losses of HTS tape and superconductor/ferromagnetic substrate(SC/FM) composite tape, we analyze the effect of magnetic ferromagnetic substrate on the AC losses of HTS tapes in different electromagnetic fields. It is found that the magnetic substrate can increase the AC losses of superconducting tapes at low magnetic field, but at high magnetic field, the magnetic substrate can decrease the AC losses. The AC losses of SC/FM composite tape will decrease with increasing frequency at low magnetic field, however the losses will increase firstly and then decrease with increasing frequency at high magnetic field. The AC losses has a minimum value, as the phase difference is equal to 90 degree; when the magnetic field and current are inphase and antiphase, the AC losses are equal. The effects of magnetic ferromagnetic substrate on multi-layer stacked superconducting tapes are every similar to the effects on single tape. Secondly, the quench process in a stack of composite superconducting tapes is investigaed. The temperature-dependent material parameters of composite superconducting tape is considered in low temperature environment. The thermally coupled H-formulation is used to analyse the magneto-thermal coupled behav...
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Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226423
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
万星星. 高温超导复合带材的交流损耗及失超行为的数值分析[D]. 兰州. 兰州大学,2016.
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