大电流真空电弧阳极熔蚀过程的热力学仿真研究

Thermodynamics Simulation of the Anode Erosion Process Under High-current Vacuum Arcs

在大电流真空电弧开断过程中,阳极现象对于能否成功开断具有重要影响。当电弧电流超过阈值时,阳极表面温度将超过材料熔点,从而在阳极局部形成熔池。阳极熔池中的液态金属蒸发出的金属蒸汽及喷溅出的液滴将极大的提高弧后击穿的概率,并可能造成开断失败。该文建立了大电流真空燃弧过程中阳极熔池的流体流动和传热模型,着重研究真空大电流电弧对于阳极表面的熔蚀、变形以及相应的温度分布的变化。模型考虑了从电弧等离子体到阳极表面的传热以及表面材料在热流作用下的相变过程,将磁流体仿真结果获得的热流密度和压力分布作为阳极熔池流动和传热的仿真的边界条件,并采用有限体积法仿真获得阳极表面破坏过程以及温度分布的变化规律。仿真结果给出了不同电流下的温度分布和由电弧引起的阳极表面破坏情况,发现考虑熔池中液态金属流动和变形的仿真模型所获得的表面温度分布更加均匀,解释了实验中触头表面温度的均匀分布现象,证明液态金属的流动是影响温度分布的重要因素。所获得模型更为准确地描述了大电流真空电弧作用下的阳极现象,为评估真空断路器的开断能力提供了理论依据。

Anode activity is critical in a high-current interruption process of a vacuum interrupter. When the arc current exceeds a certain threshold value, anode surface temperature may exceed melting point, thus an anode melting pool can form. An evaporation of metal vapor and liquid droplets from an anode melting pool may play a role for a failure of the current interruption. The objective of this paper is to develop a model of fluid flow and heat transfer in an anode melting pool to study the anode erosion, deformation and temperature distribution under high-current vacuum arc. The model incorporated heat transfer from arc plasma to anode surface and phase change of anode materials. The model used heat flux and pressure distribution obtained from magneto-hydrodynamic simulations as an input. By applying a finite volume method, the model analyzed temperature distribution and the erosion of anode surface under different arcing situations. The results can explain the uniform distribution of anode surface temperature measured in experiments and prove that the liquid metal flow influences the temperature distribution strongly.