Developing Superconducting Fault Current Limiters (SFCLs) for Distributed Electric Propulsion Aircraft

分布式电力推进飞机已被航空业的主要参与者提出，作为解决航空旅行对环境影响的颠覆性技术。电力推进提供了在飞机内部分配电力的灵活性，并将分布式推进与机身更好地集成在一起，从而显著节省燃油，降低排放和噪音。例如，NASA的N3-X概念飞机有很大的潜力，相对于2000年的基线，它可以节省70%的燃料。超导故障限流器是实现分布式电力推进系统在不同故障条件下的可靠性和安全性的关键。电阻式超导故障限流器（SFCL）是一种最简单、最紧凑的设计，它利用了超导材料的固有特性，即在高电流水平下淬火，并从可忽略的电阻过渡到高电阻来限制故障电流。过去和现在的SFCL研究主要是针对陆基电力系统进行的。电阻式SFCLs已研制成功，并在交流活网中可靠运行。研究了2G高温超导导体直流应用的直样品和小线圈。然而，到目前为止，还没有专门为飞机应用而设计的SFCL。与陆基动力系统相比，设计用于飞机的SFCL的关键挑战是提高效率和减轻重量，以实现最小的重量损失。因此，为了实现未来大型电力推进飞机的发展，迫切需要采用数值和实验相结合的方法开发高效、轻量化的交、直流SFCLs。该项目将通过提供1)交流损耗最小的交流SFCL和2)所需高温超导材料最少的直流SFCL来满足这一要求。这将通过确定新型缠绕策略和候选高温超导层压材料的最佳组合来实现。首先，我们将建立一个新的多物理场有限元模型，对2G高温超导SFCL线圈的电磁和热行为进行耦合分析。将使用有限元模型研究新型绕组策略和HTS层压材料的组合，以提供最佳的交流和直流SFCL线圈。其次，我们将构建和表征具有代表性的交流SFCL小螺旋线圈。一个1 kA的演示交流SFCL线圈也将使用最佳组合来构建，在50 K和77 K之间的广泛工作温度范围内进行识别和表征。第三，我们将构建和表征一个1 kA直流SFCL演示线圈，并根据最小的整体系统重量确定最佳工作温度。最后，我们将验证多物理场SFCL模型，并根据实验结果检查基本物理限制。我们还将确定将实验室示范扩大到工业原型的途径。这将为实现飞机应用的高效率和轻量化SFCLs提供至关重要的一步。这项工作将与空中客车公司和牛津仪器公司密切合作，并将提供具体的建议，以扩大实验室演示到工业原型。

Distributed electric propulsion aircraft have been proposed by leading players in the aviation industry as a disruptive technology to address the environmental impact of air travel. Electric propulsion offers flexibility to distribute the electric power within the aircraft and better integration of distributed propulsion with airframe, leading to significant fuel saving, emission and noise reduction. The NASA N3-X concept aircraft for example has great potential to deliver 70% fuel saving relative to 2000 baseline. Superconducting fault current limiters (SFCLs) are critically required to achieve reliability and safety of the distributed electric propulsion power system under different fault conditions. Resistive superconducting fault current limiter (SFCL) is the simplest and most compact design making use of the intrinsic superconductor material behaviour of quenching at high current levels and transitioning from negligible resistance to a high resistance to limit the fault current. Previous and ongoing SFCL research have been undertaken mainly for land-based power system. Resistive SFCLs have been successfully developed and demonstrated reliable operation in AC live-grids. Straight samples and small coils of 2G HTS conductors have been investigated for DC application. However, up to now there is no SFCL specially designed for aeroplane application. Compared with the land-based power system, the key challenges to design SFCL for aeroplane application is efficiency improvement and weight reduction in order to deliver minimum weight penalty. Therefore, there is a timely requirement to develop high efficiency and lightweight AC and DC SFCLs using both numerical and experimental methods to enable future development of large-scale electric propulsion aircraft.This project will meet this requirement by delivering 1) an AC SFCL with minimised AC losses, and 2) a DC SFCL with minimised HTS materials required. This will be achieved by determining the optimum combination of novel winding strategy and candidate HTS lamination material. Firstly, we will develop a new multi-physics finite element model coupling analysis of electromagnetic and thermal behaviour of the 2G HTS SFCL coil. The combination of novel winding strategies and HTS lamination materials which deliver optimum AC and DC SFCL coils will be investigated using the finite element model. Secondly, we will construct and characterise representative small helical coil for the AC SFCL. A 1 kA demonstration AC SFCL coil will also be built using the optimum combination identified and characterised in a wide range of operation temperature between 50 K and 77 K. Thirdly, we will construct and characterise a 1 kA DC SFCL demonstration coil and determine the optimum operating temperature in terms of minimum overall system weight. And finally, we will validate the multi-physics SFCL model and examine fundamental physics limitation based on the experimental results. We will also determine the pathway to scale up laboratory demonstrators to industry prototype. This will provide a vital step towards the realisation of high efficiency and lightweight SFCLs for aeroplane application. This work will be carried out in close collaboration with Airbus and Oxford Instruments, and will provide specific recommendations to scale up laboratory demonstrators to industry prototype.