Non-Equilibrium Effects in High Pressure, High Intensity Arcs

研究发现，平行于阳极表面的冷气流可以使发光弧等离子体与阳极表面之间的非平衡区扩大，从而形成稳定的附着区。流向阳极的电流似乎分布在相对较大的区域上，因此极大地减少了阳极的热通量。在本研究中，研究了这种类型的电弧附着，即收缩稳定的电弧附着到垂直于电弧轴的阳极上，并使冷气流平行于阳极表面。利用激光辐射的汤姆逊散射来确定电子温度和密度分布的数据分析技术，表征了阳极和弧柱之间扩大的非平衡区。通过在阳极中嵌入朗缪尔探头的测量，可以在阳极表面提供相同数量的值，从而可以确定电流密度分布，而热通量探头测量可以给出阳极表面的热通量分布。使用三维有限体积代码对非平衡等离子体进行的并行建模工作提供了对该非平衡区域中的物理过程的洞察，包括电场强度的映射。同时考虑了动力学和成分的不平衡，并采用了自洽的扩散处理方法。宽带冲击高强度电弧由于能够提供高通量的电子、离子或其他自由基，在材料加工中引起了极大的兴趣。然而，由于电弧等离子体通常接近平衡，这些熔剂通常与高热流密度耦合，限制了它们在加工应用中的有效性。此外，电弧经常以不稳定的方式运行，高热流密度导致电极被侵蚀，限制了电弧装置的寿命。这项研究解决了与高电子密度在电弧中的益处相关的高热流问题。这项调查的两个方面预计将导致具有实际意义的结果。一种是产生更大的非平衡等离子体体积，可用于表面处理或整体化学处理。第二个问题是，对于热流密度明显较低的高强度电弧，存在广域漫射连接，因此

It has been discovered that a cold gas flow parallel to the anode surface can lead to a stable attachment with an enlarged non-equilibrium region between the luminous arc plasma and the anode surface. The current flow to the anode appears to be distributed over a relatively large area, thus drastically reducing the anode heat flux. In this study, this type of arc attachment, in which a constrictor-stabilized arc attaches to an anode perpendicular to the arc axis with a cold gas flow parallel to the anode surface, is investigated. The enlarged non-equilibrium region between the anode and the arc column is characterized with a newly developed data analysis technique using Thomson scattering of laser radiation to determine the electron temperature and density distributions. Measurements with a Langmuir probe imbedded in the anode provide values for the same quantities at the anode surface allowing determination of the current density distribution, and heat-flux probe measurements give the heat-flux distribution at the anode surface. A parallel modeling effort using a three-dimensional finite-volume code for a non-equilibrium plasma provides insight into the physical processes in this non-equilibrium region including a mapping of the electric field strength. Both kinetic and composition non-equilibrium are considered, and a self-consistent treatment for diffusion is used.Broader impactHigh intensity arcs have attracted considerable interest for materials processing because they can provide high fluxes of electrons, ions, or other radicals. However, because the arc plasma is usually close to equilibrium, these fluxes are usually coupled with high heat fluxes, limiting their usefulness for processing applications. Furthermore, electric arcs frequently operate in an unstable manner, and the high heat fluxes lead to erosion of the electrodes, limiting the life of arcing devices. This study addresses the problems of the high heat fluxes associated with the benefits of high electron densities in electric arcs. Two aspects of this investigation are expected to lead to results of practical importance. One is the generation of larger non-equilibrium plasma volumes that can be used for surface treatment or bulk chemical processing. The second is the existence of a wide-area diffuse attachment for high-intensity arcs with apparently low heat-flux densities and, consequentl