涂层超导复合结构三维电-磁-热有限元仿真模型研究

Superconducting coated conductors with composite structure is promising for electric power devices and high field magnets for their advantages, such as high transporting current, high magnetic field, low self-inductance, structure flexibility and compact layout et al. With a parallel arrangement of the tapes, when external thermal disturbance is initialized, the flowing currents would redistribute within the cross sections of the superconducting composite conductors, due to the electro-magneto-thermal interaction. Additionally, circulating current and screening current would also be excited among the neighboring tapes. These would eventually decrease the current-transporting capacity and the stability of the magnetic field, meanwhile, increase the load of the cryogenic refrigerators. Based on the T-A electromagnetic computing model, this project focuses the scientific problem of establishing 3D electro-magneto-thermal FEM model for superconducting coated conductors with parallel composite structure, uses the boundary condition to constrain the whole current of the cross section, employs the E-J power law as superconducting constitutive relation which takes account of current redistribution between superconducting layer and stabilizer layers, and finally verifies the numerical model with the analytical and experimental results. This project can be roughly divided into three parts, the electromagnetic computing model for parallel superconducting coated conductors, the electro-magneto-thermal simulation model for single superconducting coated conductor and the electro-magneto-thermal simulation model for parallel superconducting coated conductors. We aim to investigate the multiphysics interaction mechanism, propose the analysis methods for superconducting characteristics such as current distribution, ac loss and stability et al, and finally enable the designs of electric power devices and high field magnets.

复合结构涂层超导体具有载流密度大、产生磁场高、线圈自感小、结构灵活、布局紧凑等优点，在超导电力设备和高场磁体等装备中应用广泛。涂层超导体并联复合后，当受到热扰动而失超时，由于电-磁-热多物理场耦合，电流会在横截面重新分配，带材间会形成环流和屏蔽电流，降低导体载流能力和磁场稳定性，增加损耗。本项目围绕并联复合结构涂层超导体三维电-磁-热耦合有限元仿真的科学问题，在T-A电磁计算模型的基础上，以横截面总电流为约束边界条件，以包含超导层和稳定层分流过程的扩展E-J指数模型为本构关系，采用理论分析和实验测量相结合的验证手段，依次建立并联复合导体的电磁计算模型、单个涂层超导体的电-磁-热耦合仿真模型和并联复合结构涂层超导体的电-磁-热耦合仿真模型，认知多物理场相互作用机制，掌握电流分布、交流损耗和失超传播等超导特性的计算方法，为超导电力装备和高场磁场的研发奠定科学基础。

本项目在涂层超导体T-A电磁计算模型的基础上，通过引入截面总电流约束边界条件和考虑超导层和稳定层分流过程的扩展E-J本构关系，建立涂层导体复合结构三维电-磁-热高效通用有限元仿真模型，并采用理论和实验相结合来对数值模型进行验证。首先，以复合超导体总的传输电流为约束条件，建立涂层超导体并联复合结构三维电磁计算模型，通过实际超导电缆的测试数据进行验证，分析临界电流与交流损耗的关系；其次，建立扩展的E-J指数模型，考虑暂态过程中电流在不同层间的再分配过程，建立三维电-磁-热耦合暂态仿真模，分析冲击电流作用下和热扰动下涂层超导体的失超传播过程；最后，结合并联复合结构的边界条件和扩展本构关系，建立涂层超导体并联复合结构三维电-磁-热有限元仿真模型，仿真研究TSTC复合导体在热扰动下失超传播和恢复过程。本研究提出的模型为进一步开展大容量复合导体结构优化设计、超导电力装备特性分析和强磁场磁体设计与保护等关键技术研究奠定理论基础。