直流传导式液态金属电磁泵流场畸变及其电磁构型补偿

DC conduction liquid metal electromagnetic pump flow field distortion and its electromagnetic configuration compensation

  • 摘要: 利用直流传导电磁泵(DC-EMP)驱动低熔点的镓基液态金属作为冷却工质的散热方法,在高热流芯片的热控领域展现出重要的应用前景。为削弱液态金属的磁流体动力学(Magnetohydrodynamic, MHD)效应及其导致的流场畸变,提高DC-EMP的驱动性能。对液态金属的流动特性,流道内电流密度场、磁感应强度及洛伦兹力矢量分布进行了研究,采用磁轭和绝缘板进行电磁构型补偿以提高DC-EMP作用区的磁感应强度和有效电流,从而削弱MHD效应。结果表明:受MHD效应的影响,靠近侧壁面的液态金属被加速主流区流速降低,流道内液态金属在穿过作用区后会发生严重的流场畸变。液态金属切割磁感线产生的感应电流在作用区端部形成涡电流,减弱了作用区内的有效电流,同时在涡电流和电、磁场端部效应的耦合下,在作用区外产生与流速方向相反的洛伦兹力阻力,抑制液态金属进入和离开作用区,进而降低DC-EMP的性能。试验表明电磁泵的进出口压差∆P随输入电流It的增加而增大,当It=50 A时补偿后的∆P较传统结构提高了78.08%。

     

    Abstract: A heat dissipation method using a DC-conduction electromagnetic pump (DC-EMP) to drive a low-melting-point gallium-based liquid metal as a cooling workpiece, which has significant prospects in the field of heat dissipation in chips. In order to weaken the magnetohydrodynamic (MHD) effect of liquid metals and its resulting flow field distortion, and to improve the performance of DC-EMP. The flow characteristics of liquid metal, current density field, magnetic induction strength and Lorentz force vector distribution in the flow channel were investigated, and the electromagnetic configuration was compensated by using an iron yoke and an insulation bars in order to increase the magnetic induction strength and the effective current in the DC-EMP region of action, thus weakening the MHD effect. The results show that the liquid metal near the side wall surface is accelerated by the MHD effect, the flow velocity in the main flow zone decreases, and the liquid metal in the flow channel undergoes serious flow field distortion after passing through the magnetic field zone. The induced current generated by the liquid metal cutting the magnetic susceptibility line forms an eddy current at the end of the action zone, which attenuates the effective current within the action zone, and at the same time, under the coupling of the eddy current and the end effect of electric and magnetic fields, it generates a Lorentz force resistance outside the action zone in the opposite direction of the flow velocity, which inhibits the liquid metal from entering and leaving the action zone, and thus reduces the performance of the DC-EMP. The tests show that the ∆P of the electromagnetic pump increases with the increase of the input current It, and the compensated ∆P is improved by 78.08% compared with the conventional structure when It = 50 A.

     

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