ORC低温余热发电用叶轮转子一体化高速永磁电机特性研究

Compared with the traditional ORC low temperature waste heat generation system, the integrated high-speed permanent magnet machine direct drive system has the advantages of high efficiency, reliability and no leakage. However, because the organic medium with density higher than the 10kg/m3 and the temperature more than 80 oC directly flow through the interior of the motor, and the integrated structure of the rotor and the impeller, resulting in the problems of huge wind friction, poor heat dissipation, and difficult coupling design, which seriously restricts the application of high speed permanent magnet machine. First of all, considering the characteristics of medium low boiling point and large axial temperature difference of rotor, a rotor evaporating cooling structure of hollow shaft is put forward. The thermal calculation model considering phase transformation and rotor rotation is established to obtain the heat transfer law and efficient cooling scheme. Secondly, considering the difference of rotor temperature distribution, a stress calculation model under non-uniform temperature is established, and the stress distribution law of rotor under non isothermal body is analyzed, and the rotor structure is optimized. Finally, we analyze the cross coupling mechanism of multi-physical fields and the sensitivity of the constraint parameters, and select the constraint parameters and optimization objectives reasonably, and establish a multi physical field coupling optimization design model. It will lay a foundation for the practical industrial application of ORC high speed direct drive system for waste heat power generation. The research achievement of this project will also promote the application of high speed permanent magnet motor in compressor, micro gas turbine power generation and other fields.

与传统ORC低温余热发电系统相比，采用一体化的高速永磁电机直驱系统，可以提高效率、增加可靠性、实现介质全封闭无泄漏的优点，然而由于叶轮与转子一体化结构、密度高于10kg/m3、温度高于80度的有机介质直接流过电机内部，造成风摩耗巨大、散热困难、难以耦合设计等问题，严重制约着高速永磁电机的应用。首先，本项目结合介质低沸点和转子轴向温差大的特点，提出一种转子空心轴循环蒸发冷却结构，建立考虑多种流体形态的电磁-温度迭代分析模型，得到流体传热规律和高效冷却方案；其次，考虑转子温度分布的差异性，分析非等温体下的转子应力分布规律，建立非均匀温度下的应力计算模型，优化转子结构；最后，分析多物理场交叉耦合机理和制约参数的敏感度，合理选取约束参数和优化目标，建立一种多物理场耦合设计模型，为余热发电高速直驱系统的实际工业应用奠定基础，该项目的研究成果还将促进高速永磁电机在压缩机、微型燃气轮发电等领域的应用。

采用一体化的高速永磁电机直驱系统，可以提高ORC低温余热发电系统的效率、可靠性、实现介质全封闭无泄漏的优点，是余热发电关键装备的重要发展趋势。然而由于余热发电有机介质具有高温高质量密度的特点，且直接流过电机内部，造成风摩耗巨大、散热困难、难以耦合设计等问题，严重制约着高速永磁电机在余热发电领域中的应用。本项目针对ORC低温余热发电用高速永磁电机，首先分析了高密度介质下的损耗特性，在此基础上设计了四种冷却方案，对四种冷却方案建立了电磁-温度多次迭代计算的温度场计算模型，对比了四种冷却方案的温度分布规律，并分析了温度特性的主要影响因素，获得了良好的冷却系统；其次，考虑转子温度分布的差异性，建立非均匀温度下的应力计算模型，获得了非等温体对转子应力分布的影响规律；最后，分析了电机主要设计参数对多物理场性能的交叉影响，总结了设计参数对多物理场性能综合影响规律，获得了满足多物理场需求的设计方案。基于一台400kW，10000rpm的余热发电用高速永磁电机，对该样机进行了综合性能测试，验证了本项目的理论分析。该项目获得了ORC低温余热发电用高速永磁电机的损耗特性、传热规律、非等温体下转子应力分布规律以及多物理场约束下的电机设计规律，所研制的样机已在实际工业中得到初步应用，有效地提高了低温余热发电系统的效率和可靠性，为高速直驱余热发电系统的发展与应用提供了理论依据。依托该项目的研究发表高水平学术期刊论文8篇，获得国家发明专利2项，参加学术会议7次，培养硕士生3名。