Churning loss characteristics of a wet three-phase high-speed reluctance motor

Abstract

With the increasing requirements of electro-hydrostatic actuators (EHAs) for power, volume, and pressure, there is a growing tendency in the industry to combine the motor and pump to form a so-called ‘motor pump’ to improve the integration. In this paper, a novel structure for a wet three-phase high-speed reluctance motor pump is proposed, which can further improve integration by removing the dynamic seal on the pump shaft, thereby avoiding the problems of dynamic seal wear and oil leakage and improving heat dissipation under high-speed working conditions. However, after the motor is wetted, the churning loss caused by immersion of the rotor in the oil causes additional fluid resistance torque. Based on fundamental fluid mechanics, an analytical model of the churning torque of a wet motor was established. To verify the accuracy of the analytical model, a simulation model of churning loss was established based on computational fluid dynamics (CFD), and the churning torque and flow field state were analyzed. Finally, an experimental prototype was designed and manufactured, and a test bench for churning loss was built. The oil churning torque was measured at different speeds and temperatures. The results from the analytical, simulation, and experimental models agreed well. The experimental results validated the analytical model and CFD simulation. This research provides a practical method for calculating the churning loss and serves as guidance for future optimization of churning loss reduction. 目的 传统干式电机在高速工况下存在动密封磨损和油液泄露等问题。1. 本文通过电机湿式化提出一种湿式三相高速磁阻电机泵的新结构以去除动密封。2. 简化电机泵结构并提高集成度,以通过油液的循环流动改善电机散热问题。3. 集中研究电机湿式化后所引起的搅拌损失问题,为后续湿式电机搅油阻力矩的减阻优化提供一种较好的计算方法。 创新点 1. 提出一种新型湿式三相高速磁阻电机泵,并通过O型密封圈来构成湿式耐高压结构,避免了高速工况下的动密封磨损、油液泄露和发热严重等问题;2. 通过理论分析,推导出湿式电机搅油阻力矩的解析模型;3. 基于计算流体力学(CFD)建立湿式电机搅油的仿真模型,并对其运行过程中所受到的阻力矩和内部流场状态进行分析;4. 设计制造实验样机,搭建湿式电机搅油的实验台架,并测试不同转速和温度下的搅油阻力矩。 方法 1. 通过理论分析,建立湿式电机搅油阻力矩的解析模型(公式(26));2. 通过仿真模拟,对电机运行过程中内部流场状态(图9和10)与其受到的流体阻力矩(图11和12)进行分析,验证解析模型的有效性(图13和14);3. 通过湿式电机搅油样机和实验台架(图15和16)测试不同转速和温度下的搅油阻力矩,验证解析模型和仿真模拟的有效性(图19和20)。 结论 1. 湿式三相高速磁阻电机泵的新结构能够去除传统动密封,使其无需克服动密封摩擦力;这大大简化了电机泵的结构,提高了集成度,使其可通过油液的循环流动改善电机散热问题。2. 电机搅油阻力矩与内部流场参数之间存在映射关系,因此可通过建立解析模型实现关联表征;通过CFD对湿式电机搅油进行仿真模拟,能够验证解析模型的有效性,为电机流场求解提供一种较好的方法。3. 实验结果验证了解析模型和仿真模拟的有效性;三者的搅油阻力矩在不同转速、不同温度下的曲线趋势吻合良好,为后续湿式电机搅油阻力矩的减阻优化提供了一种较好的计算方法。4. 在高速运转过程中,电机的侧面搅油阻力矩占总搅油阻力矩的比重很大,所以如何优化电机结构参数以减小其侧面搅油阻力矩是该湿式电机能否得以成功应用的关键所在。