横向静磁场对电磁悬浮液滴稳定性的影响

Influence of horizontal static magnetic field on the stability of electromagnetic levitated Cu molten droplet

在利用电磁悬浮技术实现液滴悬浮的过程中,液滴内部往往存在剧烈对流、外部伴随快速旋转和质心的水平位移等不稳定因素;因此,实现液滴的稳定悬浮是完善电磁悬浮技术的关键.本文采用实验观测的方法,通过U形静磁场组件对液滴所在空间施加横向静磁场,利用高速相机记录了不同磁场强度下纯铜熔融液滴的振荡变形过程;分析了横向静磁场对悬浮铜液滴振荡频率、振幅以及旋转的影响.实验发现:对于熔融前的固态铜颗粒,若静磁场强度超过0.3 T,铜颗粒几乎以静止状态悬浮.熔融后,当施加0.15 T的静磁场,与未加静磁场时相比,液滴俯视图轮廓线拟合出的椭圆分别与x轴和y轴的交点坐标之差R-、椭圆面积A和椭圆长轴长度Dmax的振幅分别减小了25%,76%和60%;随着磁场强度的继续增加,振幅和频率继续减小,但在静磁场强度为0.3 T时,相比静磁场强度为0.2 T,频率增加了1 Hz.横向静磁场还抑制了悬浮铜液滴的旋转,当磁场强度增加到0.53 T时,悬浮液滴只在10?的角度范围内摆动.这些结果表明,施加横向静磁场能够有效提高悬浮液滴的稳定性.

For an electromagnetically levitated （EML） molten droplet, there usually exist some unstable factors, such as internal fluid convection, quick spin and horizontal displacement and so on. As a result, stabilizing the droplet is very important for EML technology. In this paper, a horizontal static magnetic field is imposed on an EML Cu droplet through a U-shaped static magnetic component. The shape oscillation of a Cu droplet is recorded continuously under different magnetic field intensities using a high speed camera. The effects of static magnetic field on the oscillation frequency, amplitude and spin angle of the droplet are analyzed from the recorded data of droplet shape. The result shows that when the strength of the static magnetic field exceeds 0.3 T the solid Cu is levitated statically without any spin and horizontal movement. For molten Cu droplet, its amplitudes of the R^-, A and Dmax are reduced by 25%, 76%and 60%respectively when a static magnetic field with 0.15 T is imposed. With the increase of magnetic field strength the amplitude and frequency of oscillation decease continuously. However, when the intensity of the static magnetic field is 0.3 T, its frequency is 1 Hz higher than that when the intensity of the static magnetic field is 0.2 T. Finally, the result indicates that the horizontal static magnetic field can inhibit the spin of the levitated droplets. For instance, when the strength of the magnetic field is 0.53 T the droplet spins are within a very narrow angle of 10°, which is quite smaller than in the case without static magnetic field. These results exhibit that the imposed horizontal static magnetic field can effectively improve the stability of electromagnetic levitated droplet.