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Advanced Thermomagnetic Cooling for Ultrahigh Power Density Electrical Machines

用于超高功率密度电机的先进热磁冷却

基本信息

批准号：
EP/T017988/1
负责人：
Guang-Jin Li
金额：
$ 58.85万
依托单位：
University of Sheffield
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2020
资助国家：
英国
起止时间：
2020 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FT017988%2F1
关键词：
Advanced Thermomagnetic Cooling Ultrahigh Power

项目摘要

Electrical machines are estimated to contribute to more than 99% of global generation and more than 50% of all utilisation of electrical energy. Their role will be more pronounced as we move towards a more sustainable carbon neutral economy. Taking the UK automotive industry as an example, it is the fastest growing sector in the European economy, utilising more than 30% of our primary energy resources. UK automotive production is around 2 million vehicles in 2017. By renewing end of life products with more energy efficient ones, such as electric and hybrid electric vehicles (EV and HEV), this strong growth will increase the efficiency of energy use and help meet UK government targets in CO2 emission reduction - a 34% cut in 1990 CO2 emission levels by 2020 and 80% by 2050. This trend of electrification in transport will lead to a huge demand in powertrain (machines and drives) research. To remain competitive, electrical machine manufacturers endeavour to increase power density and efficiency of electrical machines. However, the machine industry is a relatively mature sector and the margin for further improvement in machine efficacy and power density is slim without novel materials or radical cooling technologies. This is particularly the case for machine end-windings, which often have the highest temperature and hence have the biggest impact on machine achievable efficiency, power density and also life span. Methods such as spray cooling, flooded or semi-flooded stator are proposed for end-winding cooling. Both methods are very effective because the cooling fluid is in direct contact with the end-windings. However, due to corrosion and erosion of spray nozzles, the spray cooling suffers from reliability and robustness issues. Moreover, both spray cooling and flooded stator often require a closed circuit liquid (oil or deionised water) supply equipped with mechanical pumps, filters, etc. which adds to capital and operating costs while also leading to a reduction in effective machine power density.In order to overcome the challenges facing the traditional cooling technologies, this project aims to develop a novel thermomagnetic liquid cooling for machine end-windings. The thermomagnetic cooling medium is based on ferro-fluid, which is an electrically nonconductive, temperature sensitive fluid mainly consisting of ferromagnetic nano-scale particles (such as iron, cobalt, nickel, etc.) in a liquid carrier (such as synthetic oils, hydrocarbons, etc.). When such liquid experiences a temperature variation under an external magnetic field, the fluid behaves as a smart fluid, i.e. it will have higher magnetisation in the lower temperature region (farther away from the heat source) than in the higher temperature region. As a result, a net magnetic driving force is produced to self-drive the fluid to flow towards the heated area (heat source with higher temperature). Due to this special feature, the thermomagnetic liquid cooling will be self-regulating, pumpless and maintenance free and hence very cost effective.In this project, by adopting a multiphysics optimisation approach that combines electromagnetic and thermomagnetic domains into a single framework for machines with ferrofluid cooling, this project aims to achieve a temperature reduction of >30oC compared to a forced air cooled machine with rotor mounted fans. This is significant because the reduction in machine temperature, particularly the winding temperature, not only increases machine's life span, e.g. a 10oC increase in winding temperature will halve the winding insulation life (similar effect for bearings' life span), but also increases the machine's efficiency due to reduced power losses.

据估计，电机占全球发电量的99%以上，占所有电能利用的50%以上。随着我们迈向更可持续的碳中和经济，它们的作用将更加显著。以英国汽车工业为例，它是欧洲经济增长最快的部门，利用了我们30%以上的一次能源。2017年英国汽车产量约为200万辆。通过用更节能的产品更新报废产品，如电动和混合动力电动汽车（EV和HEV），这种强劲的增长将提高能源使用效率，并有助于实现英国政府的二氧化碳减排目标-到2020年将1990年的二氧化碳排放水平减少34%，到2050年减少80%。这种交通电气化的趋势将导致对动力系统（机器和驱动器）研究的巨大需求。为了保持竞争力，电机制造商努力提高电机的功率密度和效率。然而，机械行业是一个相对成熟的行业，如果没有新的材料或激进的冷却技术，进一步提高机器效率和功率密度的余地很小。对于机器端部绕组来说尤其如此，因为端部绕组通常具有最高的温度，因此对机器可实现的效率、功率密度和寿命具有最大的影响。提出了定子端部冷却的方法，如喷雾冷却、满液或半满液冷却。这两种方法都非常有效，因为冷却液与端部绕组直接接触。然而，由于喷嘴的腐蚀和侵蚀，喷雾冷却遭受可靠性和鲁棒性问题。此外，喷雾冷却和浸没式定子通常需要配备机械泵、过滤器等的闭路液体（油或去离子水）供应，这增加了资本和运营成本，同时也导致电机有效功率密度降低。为了克服传统冷却技术面临的挑战，本项目旨在开发一种新型的用于电机端部绕组的热磁液体冷却。热磁冷却介质是以铁磁流体为基础的，铁磁流体是一种主要由铁磁纳米级颗粒（如铁、钴、镍等）组成的非导电、温敏流体。在液体载体（如合成油、烃等）中。当这种液体在外部磁场下经历温度变化时，流体表现为智能流体，即，其在较低温度区域（远离热源）中比在较高温度区域中具有更高的磁化强度。因此，产生净磁驱动力以自驱动流体流向加热区域（具有较高温度的热源）。由于这种特殊的功能，热磁液体冷却将是自我调节，无泵和免维护的，因此非常具有成本效益。在这个项目中，通过采用多物理场优化方法，将电磁和热磁领域结合到一个单一的框架中，用于铁磁流体冷却的机器，这个项目的目标是实现温度降低> 30 oC与转子安装风扇的强制空气冷却机器相比。这是非常重要的，因为机器温度的降低，特别是绕组温度的降低，不仅增加了机器的寿命，例如绕组温度升高10 ℃将使绕组绝缘寿命减半（对轴承寿命的影响类似），而且由于减少了功率损耗，还增加了机器的效率。