Current density at the refractory cathode of a high-current high-pressure arc (two modes of cathode spot attachment)

Nemchinsky, Valerian

doi:10.1088/0022-3727/36/23/022

Cited by 14 publications

(36 citation statements)

References 20 publications

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“…is the volumetric heat loss due to radiation; it is supposed that plasma is optically thin and the radiation from plasma is a net sink of energy 13 . Left-hand side of equations (12) and (13) represents the convective heat flux carried by electrons or heavy particles respectively. First terms on the right-hand sides of equations (12) and (13) correspond to the thermal conduction.…”

Section: Energy Transport Equationsmentioning

confidence: 99%

“…Left-hand side of equations (12) and (13) represents the convective heat flux carried by electrons or heavy particles respectively. First terms on the right-hand sides of equations (12) and (13) correspond to the thermal conduction. The second terms on the right-hand sides of these equations represent effects of the Joule heating.…”

Section: Energy Transport Equationsmentioning

confidence: 99%

“…Though arcs has been extensively studied earlier, most of the studies considered only specific aspects of the arc physics: cathodic region 7,8,9,10,11,12,13 , arc column 14,15 , anodic region 16,17,18,19,20,21,22,23,24 . A detailed review of works on argon arc modeling can be found in Ref.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of the short argon arc with hot anode. I. Numerical simulations of non-equilibrium effects in the near-electrode regions

et al. 2018

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Atmospheric pressure arcs have recently found application in the production of nanoparticles. Distinguishing features of such arcs are small length and hot ablating anode characterized by intensive electron emission and radiation from its surface. We performed one-dimensional modeling of argon arc, which shows that near-electrode effects of thermal and ionization non-equilibrium play important role in operation of a short arc, because the non-equilibrium regions are up to several millimeters long and are comparable with the arc length. The near-anode region is typically longer than the near-cathode region and its length depends more strongly on the current density. The model was extensively verified and validated against previous simulation results and experimental data. Volt-Ampere characteristic (VAC) of the near-anode region depends on the anode cooling mechanism. The anode voltage is negative. In case of strong anode cooling (water-cooled anode) when anode is cold, temperature and plasma density gradients increase with current density resulting in decrease of the anode voltage (absolute value increases). Falling VAC of the near-anode region suggests the arc constriction near the anode. Without anode cooling, the anode temperature increases significantly with current density, leading to drastic increase in the thermionic emission current from the anode. Correspondingly, the anode voltage increases to suppress the emission -and the opposite trend in the VAC is observed. The results of simulations were found to be independent of sheath model used: collisional (fluid) or collisionless model gave the same plasma profiles for both near-anode and near-cathode regions.Parametric studies of short atmospheric pressure argon arc with tungsten electrodes were performed for various current densities and inter-electrode gap sizes. Non-equilibrium effects in the near-electrode regions were studied. Anodes with and without water cooling were considered. Effect of electron emission on current-voltage characteristic of the near-anode layer was investigated. Analytical formulas for scaling of non-equilibrium regions widths and Volt-Ampere's characteristics of these regions and the whole arc are given in the accompanying paper 44 .The organization of the paper is as follows. In Section II governing equations and boundary conditions for plasma and electrodes are presented. Section III describes numerical procedure of solving the governing equations. Results of simulations including validation of the model and parametric studies of the arc are presented and discussed in Section IV. Conclusions of this work are summarized in Section V.

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Section: Energy Transport Equationsmentioning

confidence: 99%

Section: Energy Transport Equationsmentioning

confidence: 99%

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Investigation of the short argon arc with hot anode. I. Numerical simulations of non-equilibrium effects in the near-electrode regions

et al. 2018

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“…The ions that impinge onto the cathode surface recombine with electrons from the cathode and therefore release ionization potential for each recombination and bring significant heat flux to the cathode. In previous analytical theoretical papers 17,19 it was assumed that the ion current is the only source of energy flux to the cathode. However, it is reasonable to assume that plasma electrons lose some portion of their energy in elastic collisions with heavy particles, and this energy is transferred to the cathode by thermal conduction (due to temperature decrease towards the cathode surface).…”

Section: Iii2 Ion Current To the Cathodementioning

confidence: 99%

“…Analytical models of the arc column are limited to the case of long arcs where no variation of plasma parameters along the axis takes place in the arc column 15,16 . Analytical studies of the cathodic region either focus on energy balance 17,18,19 or on the ion transport 20,21 . We could not find self-consistent model of the cathodic region coupling all the effects of heat conduction in the electrode, ion generation and transport, and the sheath voltage drop.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the short argon arc with hot anode. II. Analytical model

et al. 2018

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Short atmospheric pressure argon arc is studied numerically and analytically. In a short arc with interelectrode gap of several millimeters non-equilibrium effects in plasma play important role in operation of the arc. High anode temperature leads to electron emission and intensive radiation from its surface. Complete self-consistent analytical model of the whole arc comprising of models for near-electrode regions, arc column and a model of heat transfer in cylindrical electrodes was developed. The model predicts width of non-equilibrium layers and arc column, voltages and plasma profiles in these regions, heat and ion fluxes to the electrodes. Parametric studies of the arc have been performed for a range of the arc current densities, inter-electrode gap widths and gas pressures. The model was validated against experimental data and verified by comparison with numerical solution. Good agreement between the analytical model and simulations and reasonable agreement with experimental data were obtained.

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Heat Transfer in Plasma Arc Cutting

Nemchinsky¹

2018

Handbook of Thermal Science and Engineering

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Current density at the refractory cathode of a high-current high-pressure arc (two modes of cathode spot attachment)

Cited by 14 publications

References 20 publications

Investigation of the short argon arc with hot anode. I. Numerical simulations of non-equilibrium effects in the near-electrode regions

Investigation of the short argon arc with hot anode. I. Numerical simulations of non-equilibrium effects in the near-electrode regions

Investigation of the short argon arc with hot anode. II. Analytical model

Heat Transfer in Plasma Arc Cutting

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