大容量高功率密度永磁电机自驱动蒸发冷却系统显性特征研究

With the development of large capacity high power density permanent magnet (PM) machine, demand of cooling system of PM machine is much higher. Moreover, evaporative cooling technology is an important way to cool PM machine efficiently and reliably. Self-driven evaporative cooling system has been verified on large capacity permanent magnet wind generator. Research shows, distributions of flow paths and heat will restrict self-driven two-phase flow and heat transfer characteristics within the stator core. Besides, local obstruction of flow path, high gaseous composition in local area, transient process of heat source will affect the reliability of cooling. This project will study dominant characteristic of self-driven evaporative cooling system in the PM machine, and morphology of gas-liquid two-phase flow in cooling channels. In addition, the project will study the distribution of gaseous component in the cooling area, and reveal the coupling relationship between two-phase flow and heat transfer performance in the PM machine. On the basis of above studies, the project study the method of selecting parameters, such as structure of cooling channel, heat density of core and stator windings. At last, the project gives collaborative method to solve flow channel and heat distribution problem, and propose efficient cooling structure and optimization guidelines which are suitable for large capacity high power density PM machine. The project will help expand theoretical research and engineering application of self-driven evaporative cooling system in large capacity high power density PM machine, and provide support for increasing capacity and power density ulteriorly.

大容量高功率密度永磁电机的发展，对电机的冷却系统提出了更高的要求，采用蒸发冷却技术是实现电机高效可靠冷却的重要技术途径。自驱动蒸发冷却系统已在大容量永磁风力发电机上得到试验验证，但研究发现定子铁芯内的自驱动气液两相流动和换热性能，受到流道形态和热源分布的制约，流道局部塞阻、区域气相组分偏高、热源瞬态过程等因素都将影响电机的冷却可靠性。本项目提出对电机内自驱动蒸发冷却系统的显性特征进行研究，研究电机冷却流道内的气液两相流动形态，获得散热区域内气相组份的分布，揭示电机内两相流动和换热性能的耦合关系；在此基础上，研究电机冷却通道结构、定子绕组和铁芯的热源密度等参数的选取方法，给出解决流动通道与热源分布的协同方法，确定适合大容量高功率密度永磁电机高效冷却结构和优化设计准则。本项目将有利于拓展大容量高密度永磁电机自驱动蒸发冷却系统理论研究和工程应用，并为进一步提高电机容量和功率密度提供支撑。

基于相变换热原理的蒸发冷却技术是实现大容量高功率密度永磁电机高效冷却的重要技术途径，而定子铁心径向通道沟内两相流道结构复杂、热源集中，通道内自驱动气液两相流动特性对换热过程具有重要的影响，尤其是气相组份偏高将威胁到电机冷却的可靠性，因此本项目提出对大容量永磁电机内自驱动蒸发冷却系统的显性特征进行研究，主要研究了如下内容：.1、提出了复杂结构内相变换热过程的数值模型，并利用三维均相模型进行流道内两相流的仿真计算。建立了高功率密度蒸发冷却电机定子温升和自驱动两相流换热的实验系统，并研制了流场测试装置及参数处理方法。.2、基于有限元数值计算平台，建立了电机定子复杂结构内的相变换热流场的精细化求解模型，实现了对求解模型参数的准确计算和提取。优化径向通道沟模型实验平台，实现了流道结构的高自由度调节和实验研究，并获得了径向通道沟内结构参数对两相流场分布的影响规律。.3、通过均相原理的两相流场数据处理，将实验结果与仿真数据进行对比分析，优化数值计算模型和数据处理方法，进一步提升了自循环蒸发冷却系统复杂结构内两相流动与传热过程计算的准确性。基于模型实验和数值仿真的数据，分析了自循环蒸发冷却系统中流道结构和热源参数与两相流动显性参量的耦合关系，并进行验证。.4、利用精细化的数值仿真，分析了不同电机热源分布和流道结构对通道内流型的影响和演变规律，并研究了电机径向冷却通道内两相流动传热恶化的极限。结合电机的高功率密度优化方向，提出了热源分布和冷却通道结构方案，并归纳了大容量高功率密度永磁电机高效冷却结构和优化设计准则。.本项目执行期间，已培养博士研究生2名，硕士研究生2名。发表相关论文14篇，其中SCI或EI收录14篇。申请了6件发明专利。