高速磁性液体旋转密封中的磁化弛豫效应及其对密封耐压的影响

磁性液体密封技术正在越来越多地被用来解决机械、军工、核能等领域中高速旋转轴的动密封难题，而由于现有磁性液体密封理论模型中忽略了磁性液体的磁化弛豫过程，使其未达到能够较为精确预测高转速工况下密封性能的水平。为此，本项目从磁化弛豫所引起的结果磁场出发，建立磁性液体磁化弛豫时间的测量方法；在此基础上，考虑磁化弛豫并应用非平衡磁性液体动力学理论，建立适用于高转速工况的磁性液体旋转密封理论模型，并应用多场耦合计算的方法求解数学模型；在验证模型和方法的正确性后，研究高转速工况下密封间隙内磁性液体的流动特性及其对磁性液体密封环的截面形状和密封耐压的影响规律，建立密封失效转速和密封耐压对各物理参数的依赖关系；基于建立的数学模型，探索密封结构中永磁体排布不均、转轴偏心等实际工况下的磁化弛豫效应和密封失效机制。. 项目研究成果可丰富磁性液体旋转密封理论，为实现高转速工况下良好的磁性液体密封设计奠定理论基础。

Ferrofluid seals are increasingly being used to solve rotary-shaft sealing problems with high rotational speeds in some fields such as machinery, petrochemical, and nuclear industry. However, the present theoretical models of ferrofluid seals have not reached the level that can accurately predict the sealing performance in high speed applications as a consequence of the ignorance of the magnetization relaxation process that occurs in ferrofluids. To this end a method for measuring the magnetization relaxation time of ferrofluids will be established according to the magnetic field caused by it. Furthermore, a theoretical model of ferrofluid rotary shaft seals operating at high speeds will be developed and subsequently solved using the multi-field coupling algorithm. After the correctness of the model and the method is verified, studies will be conducted to understand the flow characteristics of ferrofluids in the sealing gaps and how it will affect the high-speed performance including the section shapes of ferrofluid sealing rings and the pressure capacity. The dependence relations of failure speed and pressure capacity on various parameters will also be deduced. Moreover, the magnetization relaxation effect and the mechanism of seal failure under actual working conditions such as uneven arrangement of permanent magnets and eccentricity of rotating shafts will be explored based on the established mathematical model. . The results of this project herein could enrich the theory of ferrofluid rotary shaft seals. They may also provide a basis for achieving better design of ferrofluid seals operating at high speeds.