Arc-Anode Attachement Instability

摘要-Heberlein这项研究的最终目的是加深我们对弧阳极附着物的了解，特别是在运行不稳定的地区，以便为设计寿命更长、可靠性更高的消弧装置建立指南。较短期的目标是：(1)开发预测喷嘴阳极的弧阳极附着运动的方法，作为电弧电流、气体类型、流速和通道直径的函数；这些参数确定边界层中的速度和温度分布，从而确定电流从弧阳极向阳极转移的特征；以及(2)确定发生从扩散弧阳极附着到收缩弧阳极附着的条件，该条件与特定的电弧配置无关。为了实现这一点，针对两种不同的配置进行了建模和实验相结合：弧轴平行于阳极和弧轴垂直于阳极。具体任务包括：用三维动力学模型模拟喷嘴流动电弧的弧阳极附着不稳定性；对喷嘴阳极内的弧阳极附着运动进行实验研究，以获得附着速度与冷气体边界层厚度之间的关系；以及对弧轴垂直于阳极的弧阳极附着随等离子体速度和其他因素的变化进行实验研究。加深对弧电极效应的了解对于提高各种等离子体设备的性能和寿命至关重要，这些等离子体设备包括放电灯、断路器、弧喷推进器、等离子喷枪和冶金加工中的电弧加热器。

Abstract-HeberleinThis research has the ultimate goal of enhancing our understanding of the arc-anode attachment, particularly in the regions of unstable operation in order to establish guidelines for design of arcing devices with longer life and greater reliability. Shorter term objectives are: (1) the development of methods to predict arc-anode attachment movement for nozzle anodes as a function of arc current, gas type, flow rate, and channel diameter; these parameters determine velocity and temperature distributions in the boundary layer and therefore the characteristics of the current transfer from the arc to the anode; and (2) determination of conditions for which a transition occurs form a diffuse arc-anode attachment to a constricted one in terms that are independent of the specific arcing configuration. To accomplish this, a combination of modeling and experiments are performed for two different configurations: with the axis of the arc parallel to the anode and with the axis of the arc perpendicular to the anode. Specific tasks include modeling of the arc-anode attachment instability for nozzle flow arcs with a three-dimensional dynamic model; experimental investigation of the arc-anode attachment movement in nozzle anodes to obtain the relationship between attachment velocity and the cold gas boundary layer thickness; and experimental investigation of the change in arc-anode attachment with an arc axis perpendicular to the anode as a function of plasma flow velocity and other factors.Improved understanding of arc-electrode effects is essential for improving performance and lifetime in a variety of plasma devices such as discharge lamps, circuit breakers, arcjet thrusters, plasma spray torches, and arc heaters for metallurgical processing.