A new benchmark problem for electromagnetic modelling of superconductors: the high-Tcsuperconducting dynamo
A new benchmark problem for electromagnetic modelling of superconductors: the high-Tcsuperconducting dynamo
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DOI：
10.1088/1361-6668/abae04
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发表时间：
2020-10-01
影响因子：
3.6
通讯作者：
Brambilla, Roberto
中科院分区：
文献类型：
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作者：
Ainslie, Mark;Grilli, Francesco;Brambilla, Roberto
高温超导(HTS)发电机是一种很有前途的装置，可以向封闭的超导电路注入大的直流超导电流。这对于给核磁共振/核磁共振磁体和超导旋转机器中的高温超导线圈充电特别有吸引力，而不需要通过电流引线连接到电源。直到最近，才开发出定量准确的预测模型，能够分析高温超导发电机并解释其潜在的物理机制。在这项工作中，我们建议使用HTS发电机作为HTS建模社区的新基准问题。为简单起见，假设2D(无限长)的情况，基准几何结构由一个永磁体组成，该永磁体在开路配置中通过静止的高温超导涂层导线。尽管在几何上很简单，但解决方案是复杂的，包括整个超导体积中时变的空间不均匀的电流和场。在这项工作中，这个基准问题使用了几种不同的方法来实现，包括基于H公式的方法，耦合H-A和T-A公式的方法，最小电磁熵产生方法，以及基于积分方程和体积积分方程的等效电路方法。这些方法对开路等效瞬时电压和累积时均等效电压，以及在磁路过渡过程中关键位置高温超导导线内的电流密度和电场分布都表现出很好的定性和定量一致性。最后，基于以下关键指标，对每种建模框架进行了关键的分析和比较：高温超导导线中的网格单元数、模型中的网格单元总数、自由度数、公差设置以及每个模型的每个周期所花费的大约时间。这一基准和本文包含的结果为研究人员提供了一个合适的框架，以验证、比较和优化他们自己的高温超导发电机建模方法。
The high-T(c)superconducting (HTS) dynamo is a promising device that can inject large DC supercurrents into a closed superconducting circuit. This is particularly attractive to energise HTS coils in NMR/MRI magnets and superconducting rotating machines without the need for connection to a power supply via current leads. It is only very recently that quantitatively accurate, predictive models have been developed which are capable of analysing HTS dynamos and explain their underlying physical mechanism. In this work, we propose to use the HTS dynamo as a new benchmark problem for the HTS modelling community. The benchmark geometry consists of a permanent magnet rotating past a stationary HTS coated-conductor wire in the open-circuit configuration, assuming for simplicity the 2D (infinitely long) case. Despite this geometric simplicity the solution is complex, comprising time-varying spatially-inhomogeneous currents and fields throughout the superconducting volume. In this work, this benchmark problem has been implemented using several different methods, includingH-formulation-based methods, coupledH-AandT-Aformulations, the Minimum Electromagnetic Entropy Production method, and integral equation and volume integral equation-based equivalent circuit methods. Each of these approaches show excellent qualitative and quantitative agreement for the open-circuit equivalent instantaneous voltage and the cumulative time-averaged equivalent voltage, as well as the current density and electric field distributions within the HTS wire at key positions during the magnet transit. Finally, a critical analysis and comparison of each of the modelling frameworks is presented, based on the following key metrics: number of mesh elements in the HTS wire, total number of mesh elements in the model, number of degrees of freedom, tolerance settings and the approximate time taken per cycle for each model. This benchmark and the results contained herein provide researchers with a suitable framework to validate, compare and optimise their own methods for modelling the HTS dynamo.