轴向磁场对焊接电弧作用的数值模拟研究

Simulation of Welding Arc in Axial Magnetic Field

采用耦合阴极模型模拟轴向磁场对焊接电弧的作用,分析了轴向磁场对焊接电弧位形的作用机制。计算结果显示,随轴向磁场增加:阴极弧根收缩;阴极附近等离子体温度升高,高温核心径向增大,弧柱收缩程度增加;阳极附近弧柱径向张开,中心温度降低;阳极表面电流密度和压力分布呈环状结构;阳极加热面增大,极值温度降低,出现温度平顶;电弧对阳极的传热量增加。分析认为,轴向磁场与电弧径向电流间的Lorentz力作用使近阳极区电弧旋转流动,产生磁抽吸作用,使阴极弧根和近阴极弧柱收缩,而阴极弧根收缩增强了阴极射流,并且抑制近阳极区电弧扩张。

Numerical simulation of welding arc in axial magnetic field（AMF） at atmospheric pressure is performed with an ideal magnetic hydromechanics dynamics（MHD） model of coupled plasma and cathode.Hence the mechanism of the welding arc affected by the AMF is analyzed.The calculation results indicate that,with the increase of AMF,the cathode arc root and the arc column near the cathode shrink,the plasma temperature near the cathode increases,the arc column near the anode expands radically,yet the core temperature decreases;the current density and the pressure of the anode arc root are both torus in configuration,the heated area of the anode increases,the plasma temperature near the anode decreases,the maximum temperature of the anode surface decreases,a temperature flat appears,and the heat transferred to the anode increases.The AMF produces a ＂magnetic sucking＂ effect through inducing arc rotating near the anode by the Lorentz effect which will enhance upstream cooled gas flow.The effect of low pressure in plasma core,together with the cooling effect by upstream cool gas,will shrink the cathode arc root and the arc column near the cathode.The shrinkage of the cathode root enhances the cathode jet,as a result,the expansion of arc column near the anode is limited.