Detailed Numerical Simulation of Cathode Spots in Vacuum Arcs—I
Detailed Numerical Simulation of Cathode Spots in Vacuum Arcs—I
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DOI：
10.1109/tps.2017.2697005
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发表时间：
2017-05
影响因子：
1.5
通讯作者：
M. D. Cunha;H. T. C. Kaufmann;M. Benilov;W. Hartmann;N. Wenzel
中科院分区：
文献类型：
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作者：
M. D. Cunha;H. T. C. Kaufmann;M. Benilov;W. Hartmann;N. Wenzel
本文建立了一个大电流真空电弧阴极斑模型，考虑了阴极斑产生的等离子体云、阴极表面电流传输的各种机制，包括阴极斑中金属蒸气电离产生的等离子体的贡献以及阴极体中的焦耳热。模拟结果可以让一个人清楚地识别不同阶段的生活中的一个单独的点：点火，在阴极表面的膨胀，和热爆炸。膨胀阶段与阴极的几乎恒定的最高温度相关联，其发生在表面处并且大约为4700-4800 K。热爆炸是热不稳定性（失控）的结果，当焦耳加热开始起作用时，热不稳定性在阴极表面以下发展。如果等离子体云已经熄灭，则斑点的发展被中断：由于热传导，斑点被热量转移到阴极的主体中而被破坏。因此，根据云的作用时间，可能会出现不同的情况：光斑可能在形成之前或在膨胀阶段，甚至在热爆炸的初始阶段就被熄灭。
A model of cathode spots in high-current vacuum arcs is developed, with account of the plasma cloud left over from a previously existing spot, all mechanisms of current transfer to the cathode surface, including the contribution of the plasma produced by ionization of the metal vapor emitted in the spot, and the Joule heat generation in the cathode body. The simulation results allow one to clearly identify the different phases of life of an individual spot: the ignition, the expansion over the cathode surface, and the thermal explosion. The expansion phase is associated with a nearly constant maximum temperature of the cathode, which occurs at the surface and is approximately 4700–4800 K. Thermal explosion is a result of thermal instability (runaway), which develops below the cathode surface when the Joule heating comes into play. The development of the spot is interrupted if the plasma cloud has been extinguished: the spot is destroyed by heat removal into the bulk of the cathode due to thermal conduction. Therefore, different scenarios are possible depending on the time of action of the cloud: the spot may be quenched before having been formed or during the expansion phase, or even at the initial stage of thermal explosion.