Numerical investigation on the flow characteristics of a reverse-polarity plasma torch by two-temperature thermal non-equilibrium modelling

Yin, Zhengxin; Yu, Deping; Wen, Yushi

doi:10.1088/2058-6272/ac0770

Cited by 7 publications

(8 citation statements)

References 26 publications

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“…[ 21 ] Comparing the volt‐ampere curves under different electrode polarities (normal‐polarity or reverse‐polarity), it can be seen that the arc voltage of reverse‐polarity is higher than that of normal‐polarity, which may be related to the different arc length for different electrode polarities. [ 23 ] The volt‐ampere curves for different electrode diameters indicate that the arc voltage decreases as the diameter of the outer electrodes decreases. In addition, when the gas flow rate is in the range of 3–6 m 3 /h, the arc voltage decreases as the current increases, which is a typical falling volt‐ampere characteristics.…”

Section: Resultsmentioning

confidence: 99%

“…The current ( I ) is 0.3–1.0 A. As described in published work, [ 23 ] when the high‐voltage electrode (cathode) is configured as the inner electrode, it is called normal‐polarity. When it is configured as the outer electrode, it is called reverse‐polarity.…”

Section: Experimental Device and Methodsmentioning

confidence: 99%

“…These quantities directly affect the volt-ampere characteristics (related to the electric power) and arc dynamics (related to discharge stability/electrode ablation rate), thus determining the range of variables and application scenarios of the plasma torch. [21][22][23] It can, of course, be inferred that the above factors also have a non-negligible influence on the discharge characteristics of GAP. Therefore, it is of great significance to understand the discharge characteristics of GAP, which contribute to the physical design, operation parameter selection, and application field guidance of GAP.…”

Section: Introductionmentioning

confidence: 99%

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Experimental study of the discharge characteristics of a 3D vortex gliding arc plasmatron

You

Wang

Yang

et al. 2022

Contributions to Plasma Physics

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The three‐dimensional (3D) vortex gliding arc plasmatron (GAP) is a promising gliding arc source due to its high reactant conversion rate and high energy efficiency, but there are few studies of its discharge characteristics. In this work, a 3D GAP device with a quartz window on the inner electrode is designed and studied. By means of high‐speed photography, high‐resolution current/voltage signal acquisition, and emission spectra, the effects of arc current, gas flow rate, electrode diameter, and electrode polarity on the discharge characteristics of this GAP are investigated. Results show that the volt‐ampere characteristic of GAP can be accurately predicted by similarity theory, and that the voltage for reverse‐polarity is significantly greater than that for normal‐polarity. Arc dynamics show that the arc at the inner electrode has the feature of high‐speed rotation, while the arc at the outer electrode has an extended current channel along with a large‐scale re‐strike process. The rotation speed and current channel length are closely related to electrode polarity, which can be ascribed to the movability of the cathode arc root. Emission spectra confirm that the plasma produced by GAP has typical non‐equilibrium properties, in which the rotational temperature ranges from 2,400 to 3,000 K and the vibrational temperature from 4,700 to 6,000 K. Moreover, abundant active free radicals, including NO, N2+$$ {\mathrm{N}}_2^{+} $$, O, and N, are detected in the plasma region. This investigation provides a better understanding of the discharge characteristics of 3D GAP, and will help to guide its further design and application.

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Section: Resultsmentioning

confidence: 99%

Section: Experimental Device and Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental study of the discharge characteristics of a 3D vortex gliding arc plasmatron

You

Wang

Yang

et al. 2022

Contributions to Plasma Physics

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“…The electron excitation temperature (T exc ) is obtained based on the spectroscopic lineratio method, and is used as a rough indication of the electron temperature, i.e. T e = T exc , for the atmospheric-pressure arc plasmas as used in [23,24]. The selected wavelengths of Ar I lines are λ 1 = 675.28 nm and λ 2 = 696.54 nm, and the method used is described in [25].…”

Section: Design Of the Arc Generator And Brief Descriptions On The Ex...mentioning

confidence: 99%

Production of a large volume non-equilibrium region in an atmospheric argon arc plasma with a counter injection of cold gas from an annular anode

Fang

Zhang

Wang

et al. 2023

J. Phys. D: Appl. Phys.

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In this letter, an annular anode is designed for producing arc plasmas with a large non-equilibrium region by using a counterflow cold gas through the annular anode. The coupled mass-momentum-energy exchange processes in an argon arc plasma are studied numerically and experimentally. The counter-injection of the cold argon gas from the center of the anode leads to a steep gradient of the heavy-particle temperature due to the formation of a thin stagnation layer resulting from the interaction of the high temperature plasma with the cold gas; and in particular, a large volume non-equilibrium “dark” plasma region is obtained above the anode surface. The results show that, with the enhancement of the convective heat transfer process in the plasma core region, the fraction of the non-equilibrium region to the whole arc plasma region reaches 92.2% where the heavy-particle temperature can be reduced significantly, e.g., ~ 2300 K, while simultaneously, the electron temperature and number density are remained at high levels greater than 8000 K and 2.4×1020 m-3, respectively, under the operating condition studied in this letter. This research not only deepens the understanding to the non-equilibrium synergistic transport mechanisms of arc plasmas, but also provides a method for producing a large volume non-equilibrium plasma region so as to promote various existing applications, or even creating new applications in the future.

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“…The thermal non-equilibrium assumption can be essential in the prediction of the shape of the arc and anode arc attachment in a plasma torch because of a more complex geometry than that of transferred arcs with planar anodes (Ref 3). Adopting the local thermodynamic equilibrium (LTE) assumption in a plasma spray torch model can result in an overestimation of (i) the arc voltage in a wide range of arc current (Ref 3, 4) because of a higher resistance of the bulk of the arc column and (ii) plasma temperature even in the arc core (Ref 5,6). An important aspect is the cold boundary layer.…”

Section: Introductionmentioning

confidence: 99%

Effect of Cathode-Plasma Coupling on Plasma Torch Operation Predicted by a 3D Two-Temperature Electric Arc Model

et al. 2023

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In a DC plasma spray torch, the plasma-forming gas is the most intensively heated and accelerated at the cathode arc attachment due to the very high electric current density at this location. A proper prediction of the cathode arc attachment is, therefore, essential for understanding the plasma jet formation and cathode operation. However, numerical studies of the cathode arc attachment mostly deal with transferred arcs or conventional plasma torches with tapered cathodes. In this study, a 3D time-dependent two-temperature model of electric arc combined with a cathode sheath model is applied to the commercial cascaded-anode plasma torch SinplexPro fitted with a wide single cathode. The model is used to investigate the effect of the cathode sheath model and bidirectional cathode-plasma coupling on the predicted cathode arc attachment and plasma flow. The model of the plasma-cathode interface takes into account the non-equilibrium space-charge sheath to establish the thermal and electric current balance at the interface. The radial profiles of cathode sheath parameters (voltage drop, electron temperature at the interface, Schottky reduction in the work function) were computed on the surface of the cathode tip and used at the cathode-plasma interface in the model of plasma torch operation. The latter is developed in the open-source CFD software Code_Saturne. It makes it possible to calculate the plasma flow fields inside and outside the plasma torch as well as the enthalpy and electromagnetic fields in the gas phase and electrodes. This study shows that the inclusion of the cathode sheath model in the two-temperature MHD model results in a higher constriction of the cathode arc attachment, more plausible cathode surface temperature distribution, more reliable prediction of the torch voltage and cooling loss, and more consistent thermal balance in the torch.

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Numerical investigation on the flow characteristics of a reverse-polarity plasma torch by two-temperature thermal non-equilibrium modelling

Cited by 7 publications

References 26 publications

Experimental study of the discharge characteristics of a 3D vortex gliding arc plasmatron

Experimental study of the discharge characteristics of a 3D vortex gliding arc plasmatron

Production of a large volume non-equilibrium region in an atmospheric argon arc plasma with a counter injection of cold gas from an annular anode

Effect of Cathode-Plasma Coupling on Plasma Torch Operation Predicted by a 3D Two-Temperature Electric Arc Model

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