Development of an arc root model for studying the electrode vaporization and its influence on arc dynamics

Abstract

Plasma–solid interaction represents a major concern in many applications such as power-interruption and plasma–metal processing. Characterized by high-current density and voltage drop, the arc roots dissipate intensive heat to electrode vaporization, which participates in the ionization and, thereby, significantly alters the plasma properties and gas dynamics. Most of the arc root models feature approaches based on surface temperature or (temperature dependent) current density. Due to the complexity of conjugated heat transfer across arc roots involving three-phase interactions of plasma with liquid spots and solid electrodes, accurately determining the surface temperature distribution is extremely computationally demanding. Hence, models hitherto fail to quantitatively estimate neither the molten spot size nor the total amount of vaporization. In this work, we propose an arc root model featuring a hemispherical structure that correlates the molten spot size with the heat partition between conduction and vaporization to estimate the energy dissipation at arc roots and, thus, to trace the vaporization rate. Following local partial pressure adjusted Langmuir vaporization, we deduce an analytical solution of molten spot size for quasi-steady-state, which compares favorably with experiments. Specifically, the vaporization dominates over conduction for large molten spots as in the case of high-current arcs. However, for low-current arcs, the vaporization heat is trivial compared with conduction. Furthermore, we integrate this arc root model into a study case of arc plasma based on the magnetohydrodynamics method. The simulated arc voltage and arc displacement match with the experiment. This model is expected to find broad applications in power interruption and plasma etching.

Experimental Study of Arc Discharge Induced Electrode Erosion and Its Influence on Arc Behaviors

“…For low-current arcs, the metal vaporization is very small. Huo et al [8] has proposed an arc root model which employs an structured hemisphere model for heat partition at the arc root and the results well matches the experimental measurements. Another big problem in the arc interruption technique is the complicated arc root physics [29,32], like voltage drop.…”

“…Electric arc discharge is one of the most popular research areas for many applications, such as plasma torches [1,2], circuit breakers [3][4][5][6][7][8], arc welding [9], surface flashover and charge generation [10][11][12][13]. The arc roots on electrode surfaces features high current density and voltage drop [14].…”

“…So, the polymer should be high-temperature resistive and can absorb considerable thermal energy (conduction and radiation) to instantly vaporize [33][34][35][36]. Huo et al [8] proposed an approach of using Stefan flow to model the vaporization induced the gas flow, which helps to understand the wall-arc interactions. In addition, for each power interruption, the materials in circuit breakers suffers a temperature rise and fall, which can even causes an fluctuating thermal stress and fatigue problems [37] for the metals.…”

Cu/W Electrode Ablation and Its Influence on Free-Burning Arcs in SF₆ Alternatives

“…Huo et al compared modeling and experimental results from a mobile free-burning arc in a Jacob's ladder configuration. Their results showed that a reduction in the Cu concentration during the arc elongation coincided with an arc voltage plateau that was observed in both the model and the experiment [23]. Such a plateau could indicate that the expected voltage increase due to the arc elongation was offset by the reduced Cu concentration of the arc, leading to a reduction in Ēarc .…”

“…Here the basic processes and dependencies are well understood, and can also inform the interpretation of the results for free-burning arcs. For temperatures below 15 kK, Cu contamination can increase the electrical conductivity of the arc due to higher ionization, while at higher temperatures the effect is reversed [23] [25]. Estimated arc temperatures are consistently below the 15 kK threshold that would lead to a reduction in the electrical conductivity, as demonstrated by Fig.…”