Flow Characteristics of Magnetic Fluid on Yoke Surface of Magnetic Fluid Seal

用有限元方法分析了磁性流体密封轭架表面的磁力分布。对两种典型的磁流体形状进行了计算，即薄膜形状和尖峰形状。有趣的是，注意到磁力方向开关的一半轭的长度。对于较厚的磁铁、较厚的轭架和带有主轴的壳体，发现磁性流体流向轭架顶部方向的区域较宽。这导致了具有自注入作用的磁性流体密封的新概念。发现在固定磁通量条件下，由半月板的扩散唯一地决定了磁流体溅射的临界转速。需要注意的是，随着磁通密度从0.2 t增加到0.4T，临界转速显著提高了近两倍。通过将SMAC方法推广到涉及表面张力和磁力的情况，建立了确定密封间隙周围形成的半月板表面形状的计算程序。通过与实验半月板形状的比较，证明了计算结果的正确性。

The magnetic force distribution on the yoke surface of a magnetic fluid seal is clarified using finite element analysis. Calculations are performed for two kinds of typical magnetic fluid shape, that is, film shape and spike shape. It is interesting to note that magnetic force direction switches halfway the yoke length. The region wherein magnetic fluid flows to the yoke top direction is found to be wider for a thicker magnet,thicker yoke and the case with a spindle. This leads to a new concept of magnetic fluid seal having self injection action.The critical rotational speed at which splashing of the magnetic fluid is initiated is found to be uniquely determined by the spread of the meniscus under a fixed magnetic flux condition. It should be noted that, with increasing flux density from 0.2 to 0.4T, the critical speed is considerable increased nearly two times.Calculation procedure to determine the surface shape of the meniscus formed around the seal gap is established through the extension of the SMAC method to the case involving surface tension and magnetic force. The calculation is justified being compared with the experimental meniscus shape.