纵向磁场下GTAW电弧传热与流动数值模拟

Numerical simulation of heat transfer and fluid flow for arc plasma in gas tungsten arc welding

针对外加纵向磁场(LMF)下的焊接电弧的传热与流动特性,建立基于磁流体动力学的二维轴对称数学模型,将流体动力学理论与麦克斯韦方程组进行耦合对电弧的温度场、电势场、电弧压力以及电流密度等进行求解,又分别对磁感应强度为0与0.06 T下的阳极热进行定量分析与对比.结果表明,外加LMF驱动带电粒子旋转并使电弧扩张,其中心出现负压并形成反重力流将阳极热汇聚于阴极附近,同时电弧因高速旋转增大热对流损失,降低焊接热效率.当磁感应强度为0.06 T时,阳极表面的电流密度、热流密度以及电弧压力等由中心分布转化为双峰分布模式.

An axisymmetrical model based on the magnectohydrodynamics(MHD)is established to study the effect of external longitudinal magnetic field(LMF)on heat transfer and fluid flow characteristics of welding arc.The profiles of temperature and voltage drop,distributions of arc pressure and current density,etc.,are simulated by utilizing the fluid dynamic theory coupled with Maxwell equations.The quantitative analysis and comparison of anodic heat fluxes in the cases of LMF strength of 0 T and 0.06 T applied are also obtained.The results show that the applied LMF could drive particles to rotate so as to expand the arc,a negative pressure area appears at the center and induces an anti-gravity flow through the arc core,concentrating the anodic energy to the cathode.Meanwhile,the arc rotating at high speed could increase the convection heat loss,and reduce the thermal efficiency.When the magnetic induction strength is 0.06 T,the distribution of current density,anodic heat flux and arc pressure shift from the arc center to periphery and shows a bimodal pattern.