中文摘要：

为了更好地研究直流电弧等离子体炬内的流动与传热,根据磁流体动力学（MHD）理论建立了等离子体电弧区的数学物理模型,采用磁矢量势A的方法来计算磁感应强度B的大小,利用通用软件FLUENT并进行二次开发,采用用户自定义函数（user defined function,UDF）加入磁流体动力学方程组中的源项和物性参数,并利用用户自定义标量方程（user defined scalar,UDS）的方法加入Maxwell方程组,采用SIMPLE算法对电弧区域进行了数值模拟。计算结果表明：等离子体炬内的弧电压随着气体质量流量的增加而增加;等离子体炬内的温度随着气体质量流量的增加而减小,而速度随着气体质量流量的增加而增加;出口处的温度和速度随径向距离的增加而减小,但温度减小的速率增加。这一结果可为实验提供理论指导和参考。

英文摘要：

Numerical simulation is a very effective and economic method for better understanding the flow and heat transfer in DC arc plasma torch.We established a mathematical physics model of the plasma arc area according to the magneto hydrodynamics（MHD） theory,in which the magnetic induction intensity B was calculated based on the method of magnetic vector potential A.The software FLUENT was further developed,and then UDF（user defined function） was used to add in the source terms in the MHD equations and the physical parameters of plasma.Meanwhile,while using the method of UDS,the Maxwell＇s equations were also added in.The simulative calculation of the arc zone was carried out using the SIMPLE algorithm.Several results were obtained from the numerical simulation： the arc voltage of plasma torch increased with the gas flow rate;with the increasing working gas flow rate,temperature of plasma torch decreased,yet the velocity of the plasma increased;the exit temperature and velocity both decreased with the increase of radius distance,meanwhile the rate of temperature decreasing kept increasing.Those results could be considered as a theoretical guidance and reference for further experiments.