Numerical analysis of chemical reaction processes in different anode attachments of a high‐intensity argon arc

Sun, Su‐Rong; Wang, Hai‐Xing; Zhu, Tao

doi:10.1002/ctpp.201900094

Cited by 8 publications

(6 citation statements)

References 40 publications

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“…The change of electric field strength changes the current density distribution of the arc anode, thereby affecting the distribution of the Lorentz force on the anode surface. According to a previous analysis [7], the main reason for the formation of the constricted arc attachment mode is a relatively high current density at the anode attachment region, which leads to anode jet formation via the Lorentz force, which is due to the interaction of the current with the self-induced magnetic field. The annular boss enhances the electric field, causing the arc to be evenly distributed on the boss, which increases the arc anode attachment area and decreases the current density, thereby preventing the formation of an anode jet.…”

Section: Resultsmentioning

confidence: 98%

“…Arc anode attachment modes have consequently been the subject of many studies. Previous experimental observations and theoretical analysis have shown that the arc anode attachment mode can be divided into the diffuse mode, the constricted mode, the multi-arc root attachment and other transitional attachment modes [2][3][4][5][6][7][8]. Among these, the constricted arc anode attachment often leads to the extremely high current and heat flux density on the anode surface, so that the arc attachment region is often subjected to strong ablation when there is insufficient anode cooling [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

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A novel anode structure for diffuse arc anode attachment

Meng

Huang

et al. 2021

J. Phys. D: Appl. Phys.

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A novel method for adjusting the direct current arc anode attachment mode by changing the anode surface structure is proposed. A transferred arc device is used to investigate the effect on the arc anode attachment state of the electrode separation and the presence and dimensions of an annular boss, or embossing, on the anode. The experimental results show the diffuse arc anode attachment mode is more likely to be formed in the presence of an annular boss structure on the anode, compared to the standard planar structure. In the case of argon working gas, as the distance between the cathode and the anode increases from 15 mm to 30 mm, the arc maintains the diffuse arc attachment on the anode with the annular boss, while for a planar anode, the arc anode attachment mode changes from diffuse to constricted. Comparison of the measured temperature distribution by the relative intensity method and the emission intensity of the arc attachment region verifies that the annular boss anode can indeed promote diffuse attachment. Analysis of the electric field strength distribution between the electrodes shows that the introduction of the annular boss doubles the electric field strength near the anode surface due to the boss edge effect, which drives the arc to be evenly dispersed on the boss, resulting in the formation of diffuse arc attachment. The enlarged attachment area reduces the current density and heat flux on the anode surface, which is important for the stabilization of diffuse arc attachment. No obvious ablation is found on the surface of the annular boss anode after 1 h operation, while there significant ablation is evident on the surface of the planar anode.

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Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

A novel anode structure for diffuse arc anode attachment

Meng

Huang

et al. 2021

J. Phys. D: Appl. Phys.

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“…Note that results of numerical computation of the excited atom density in atmospheric-pressure arcs are reported in a number of works, e.g. [5,15,31], however, it is difficult to draw definite conclusions from these results. (For example, the excited atom density near the cathode, computed in [5], is by a factor of at least 300 lower that the ion density.…”

Section: Electron Emission From Impact Of Excited Atomsmentioning

confidence: 99%

Numerical investigation of AC arc ignition on cold electrodes in atmospheric-pressure argon

Santos¹,

Lisnyak²,

Almeida³

et al. 2021

J. Phys. D: Appl. Phys.

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Since experiments cannot clarify the mechanism of current transfer to non-thermionic arc cathodes, this can only be done by means of numerical modelling based on first principles and not relying on a priori assumptions. In this work, the first quarter-period after the ignition of an AC arc on cold electrodes in atmospheric-pressure argon is investigated by means of unified one-dimensional modelling, where the conservation and transport equations for all plasma species, the electron and heavy-particle energy equations, and the Poisson equation are solved in the whole interelectrode gap up to the electrode surfaces. Results are compared with those for DC discharges and analysed with the aim to clarify the role of different mechanisms of current transfer to non-thermionic arc cathodes. It is found that the glow-to-arc transition in the AC case occurs in a way substantially different from the quasi-stationary glow-to-arc transition. The dominant mechanisms of current transfer to the cathode during the AC arc ignition on cold electrodes are, subsequently, the displacement current, the ion current, and thermionic emission current. No indications of explosive emission are found. Electron emission from the impact of excited atoms can hardly be a dominant mechanism either. The introduction of the so-called field enhancement factor, which is used for description of field electron emission from cold cathodes in a vacuum, leads to computed cathode surface temperature values that are appreciably lower than the melting temperature of tungsten even in the quasi-stationary case. This means that pure tungsten cathodes of atmospheric-pressure argon arcs can operate without melting, in contradiction with experiments.

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“…In order to accurately assess the non-equilibrium distribution of excited energy levels, the collisional–radiative (CR) model has been developed in recent years to describe the chemical kinetics and radiation in the non-equilibrium flow field (Sun & Wang 2014; Cheng, Wang & Sun 2016; Sun et al. 2017; Sun, Wang & Zhu 2020). The collisional–radiative model treats the vibrational and electronic energy states as individual species, and takes into account all relevant collisional and radiative processes among different species (Armenise & Kustova 2013).…”

Section: Introductionmentioning

confidence: 99%

Numerical study on the non-equilibrium characteristics of high-speed atmospheric re-entry flow and radiation of aircraft based on fully coupled model

Du,

Sun,

Tan

et al. 2023

J. Fluid Mech.

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The strong coupling interactions of non-equilibrium flow, microscopic particle collisions and radiative transitions within the shock layer of hypersonic atmospheric re-entry vehicles makes accurate prediction of the aerothermodynamics challenging. Therefore, in this study a self-consistent non-equilibrium flow, collisional–radiative reactions and radiative transfer fully coupled model are established to study the non-equilibrium characteristics of the flow field and radiation of vehicle atmospheric re-entry. The comparison of the present calculation results with flight data of FIRE II and previous results in the literature shows a reasonable agreement. The thermal, chemical and excited energy level non-equilibrium phenomena are obtained and analysed for the different FIRE II trajectory points, which form the critical basis for studying the heat transfer and radiation. The non-equilibrium distribution of excited energy levels significantly exists in the post-shock and near-wall regions due to the rapid vibrational dissociation and electronic under-excitation, as well as the wall catalytic reactions. The analysis of stagnation-point heating of FIRE II illustrates that the translational–rotational convection and the dissociation component diffusion play key roles in the aerodynamic heating of the wall region. The spectrally resolved radiative intensity in the entire flow field indicates that the vacuum ultraviolet radiation caused by the high-energy nitrogen atomic spectral lines makes the main contribution to the radiative transfer. Finally, it is found that the non-equilibrium flow–radiation coupling effect can exacerbate the excited energy level non-equilibrium, and further affect the gas radiative properties and radiative transfer. This fully coupled study provides an effective method for reasonable prediction of atmospheric re-entry flow and radiation fields.

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Numerical analysis of chemical reaction processes in different anode attachments of a high‐intensity argon arc

Cited by 8 publications

References 40 publications

A novel anode structure for diffuse arc anode attachment

A novel anode structure for diffuse arc anode attachment

Numerical investigation of AC arc ignition on cold electrodes in atmospheric-pressure argon

Numerical study on the non-equilibrium characteristics of high-speed atmospheric re-entry flow and radiation of aircraft based on fully coupled model

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