直流电弧等离子炬温度场-电场分布特性数值模拟

直流电弧等离子体是近年来放射性固废处理领域的重点开发技术。本文以直流非转移弧等离子炬为对象,基于Fluent软件UDF与UDS的二次开发功能,将数值模拟过程与工质气的物性参数、控制方程组源项变化以及电极电流分布进行动态链接,建立了二维轴对称的磁流体动力学(MHD)计算模型；通过求解流体力学控制方程组与麦克斯韦方程组,并采用合理的边界条件,得到了等离子炬内的温度场、速度场以及电流电势分布规律。结果显示,阴极附近电位降显著,电流密度分布集中；层流条件下弧柱区温度分布均匀,中心温度为全流域最高,区域边缘温度梯度较大；阳极附近存在电流密集分布区域,可作为弧根位置预测依据。研究工作同时为等离子炬电极寿命-射流热效率的耦合分析计算奠定了方法基础。

Numerical Simulation of the Temperature-electrical Field Characteristics in DC Arc Plasma Torches

Due to the high utilization rate, clean process and good effect of thermal plasma technology, it has become a hot development technology in solid waste incinerations. Among them, DC arc plasma is a key research technology in the field of radioactive solid waste treatment in recent years. The industrial plasma torch is the core device to realize this technology. But the internal temperature is extremely high, the temperature field and the electromagnetic field are coupled, and the experimental test is difficult. Therefore, the development and optimization of the device must rely on numerical simulation. Based on the secondary development functions of user-defined function and user-defined scalar and by analyzing the thermodynamic characteristics of the thermal plasma, the numerical simulation process was dynamically linked to the physical property parameters of the working gas, the source terms of the control equations and the electrode current distribution, thereby establishing two-dimensional axisymmetric Magnetohydrodynamics model. And using reasonable boundary conditions, the distribution law of characteristic physical parameters in the plasma torch was obtained by solving the hydromechanical control equations and Maxwell equations. The results showed that the potential drop was significant and the current density distribution was concentrated near the cathode; under laminar flow conditions, the temperature distribution in the arc column area was uniform, the center temperature was the highest in the entire basin, and the temperature gradient at the edge of the area was large; there was a dense current distribution area near the anode, which could be used as the basis for arc root position prediction. In view of the adhesion of the arc on the electrode surface, the electrode-plasma-coupling model can be calculated to obtain a more accurate temperature distribution on the inner wall surface of the device.