Prediction of anode temperatures of free burning arcs

Zhu, Peiyuan; Lowke, J. J.; Morrow, R.; Haidar, J

doi:10.1088/0022-3727/28/7/014

Cited by 71 publications

(66 citation statements)

References 13 publications

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“…This fact has motivated the use of a time-dependent and three-dimensional NLTE model in the present work. As stated in Section 1, the NLTE model is based on the chemical equilibrium assumption and uses relatively simple boundary conditions over the anode surface, and does not include the modeling of the bulk electrodes, electrode sheath models, or anode material evaporation effects [62][63][64][65][66][67][68][69]. nodes; therefore, the fine mesh has approximately 2 times the resolution and size of the base mesh.…”

Section: Problem Descriptionmentioning

confidence: 99%

Formation of self-organized anode patterns in arc discharge simulations

Trelles

2013

Plasma Sources Sci. Technol.

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Pattern formation and self-organization are phenomena commonly observed experimentally in diverse types of plasma systems, including atmospheric-pressure electric arc discharges.However, numerical simulations reproducing anode pattern formation in arc discharges have proven exceedingly elusive. Time-dependent three-dimensional thermodynamic nonequilibrium simulations reveal the spontaneous formation of self-organized patterns of anode attachment spots in the free-burning arc, a canonical thermal plasma flow established by a constant DC current between an axi-symmetric electrodes configuration in the absence of external forcing. The number of spots, their size, and distribution within the pattern depend on the applied total current and on the resolution of the spatial discretization, whereas the main properties of the plasma flow, such as maximum temperatures, velocity, and voltage drop, depend only on the former. The sensibility of the solution to the spatial discretization stresses the computational requirements for comprehensive arc discharge simulations. The obtained anode patterns qualitatively agree with experimental observations and confirm that the spots originate at the fringes of the arc -anode attachment. The results imply that heavy-species -electron energy equilibration, in addition to thermal instability, has a dominant role in the formation of anode spots in arc discharges.

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Section: Problem Descriptionmentioning

confidence: 99%

Formation of self-organized anode patterns in arc discharge simulations

Trelles

2013

Plasma Sources Sci. Technol.

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“…In the first publications, devoted to mathematical simulation of the processes of heat, mass and charge transfer in refractory cathode arcs [2][3][4][5][6][7][8][9][10], arc plasma was assumed to be single-component, i.e. containing atoms and ions of just the shielding gas.…”

mentioning

confidence: 99%

Simulation of electric arc with refractory cathode and evaporating anode

Krikent¹,

Krivtsun²,

Demchenko³

2014

The Paton Welding J.

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Equation of convective diffusion of ionized metal vapour in arc plasma, allowing for the difference in coefficients of diffusion of atoms, single-and double-charged metal ions, presence of thermodiffusion flows of metal particles, as well as ion drift in the electric field, was proposed to more precisely define the earlier developed complex model of the processes of energy, mass and charge transfer in the column and anode region of electric arc with refractory cathode and evaporating anode, running in inert gas. Based on the thus precised complex mathematical model, numerical analysis of the influence of diffusion-induced evaporation of anode material (Fe) on heat, gas-dynamic and electromagnetic characteristics of multicomponent plasma of the column and anode region of stationary electric arc with refractory cathode (W) at its running in inert gas (Ar) was performed. An essential influence of metal surface temperature distribution in the region of anode binding of the arc on distribution of temperature and electric current density in near-anode plasma, as well as on distributed and integral characteristics of its thermal impact on evaporating anode surface, is shown. 18 Ref., 12 Figures. K e y w o r d s : electric arc, refractory cathode, evaporating anode, arc column, anode region, multicomponent plasma, metal vapour, diffusion, mathematical simulationElectric arc plasma in inert-gas nonconsumableelectrode welding, as a rule, is multicomponent, as alongside shielding gas particles, it contains atoms and ions of metal vapour coming to the arc gap due to evaporation of anode metal from weld pool surface. Presence of an even small amount of metal component in inert gas arc plasma has an essential influence on its ionization composition, thermodynamic, transport and optical properties. It leads to a significant difference of heat, electromagnetic and gas-dynamic characteristics of plasma in near-anode zone of arc column in nonconsumable-electrode welding from respective characteristics of arc discharge with refractory cathode and nonevaporating, for instance, water-cooled anode. Characteristics of welding arc anode region, determining the conditions of thermal and electromagnetic interaction of the arc with metal being welded and, consequently, nature of its penetration, are also different [1].In the first publications, devoted to mathematical simulation of the processes of heat, mass and charge transfer in refractory cathode arcs [2-10], arc plasma was assumed to be single-component, i.e. containing atoms and ions of just the shielding gas. Such idealization did not incorporate any conditions of running of real welding arcs, and required further improvement of mathematical models of the arc, in order to allow for a number of additional physical factors, related to multicomponent nature of arc plasma. Publications devoted to allowing for evaporation of anode material in simulation of nonconsumableelectrode welding arc, appeared in the world scientific literature comparatively recently [11][12][13]. When describing...

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“…43 (2003) conditions for the reduction in computation time. 15,17) Because calculated arc temperature and cathode surface temperature are relatively insensitive to those detailed properties of the sheath. Table 1 shows the discharge configuration and operating conditions referring to Gas Tungsten Arc (GTA) plasma facility.…”

Section: Boundary Conditionsmentioning

confidence: 99%

Performance Evaluation of Arc-Electrodes Systems for High Temperature Materials Processing by Computational Simulation

2003

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Thermofluid analysis of an arc flow and the evaluation of the cathode lifetime have been conducted by a computational simulation for the performance improvement of arc-electrodes systems. The effects of arc current, electrode gap, inlet gas flow rate and cathode vertex angle on the temperature and velocity fields of an arc flow are clarified by parametric computations to optimize the operating conditions and torch geometry. The temperature field by an arc flow model shows the quantitative agreement with the available experimental data in the local thermodynamic equilibrium (LTE) region. The cathode lifetime is evaluated successfully by coupling with the computated thermofluid field of an arc flow. The effects of different operating conditions on the cathode lifetime are also discussed for longer lifetime of the arc-electrodes systems.KEY WORDS: computational simulation; arc; electrode; interaction; lifetime evaluation.Under these assumptions, the governing equations for arc and electrodes regions are presented as follows: The radiation loss Ra from arc is given by the multipleterms approximation as a function of plasma temperature from the experimental data for argon.2) inside the electrode ... (5) Heat flux between arc and cathode, anode are respectively given by neglecting space charge effects 13,14) in the very thin sheath and both electrodes evaporation for simplicity 15) ........ (6) ... (7) where the emission current density j e is given by the Richardson-Dushman equationion current j i is given as follows: Boundary ConditionsIn the previous almost studies, temperature distribution on the electrode surface and the current density at the cathode spot are given in assumptions. [4][5][6][7][8][9] In the present study, the temperature and electric potential conditions are given only at the cooled surfaces of anode and cathode, represented as lines CЈDЈ, FA, in Fig. 1 without assuming the current density and temperature at the electrodes surface, represented as lines CD, FG, GB 11) and neglecting sheath boundary Vol. 43 (2003) conditions for the reduction in computation time. 15,17) Because calculated arc temperature and cathode surface temperature are relatively insensitive to those detailed properties of the sheath. Table 1 shows the discharge configuration and operating conditions referring to Gas Tungsten Arc (GTA) plasma facility. Numerical Conditions and Procedures19) A cylindrical thoriated tungsten cathode (Wϩ 2wt%Th) and a plate copper anode are investigated for lifetime evaluation in the present study. The roots of both electrodes are cooled fixedly at 300 K. The thermofluid field is solved by Semi-Implicit-Method for Pressure Linked Equation (SIMPLE) 20) method using Tri Diagonal-Matrix Algorithm (TDMA). The electromagnetic field is solved by Gauss-Seidel method. Here, the grid has 75ϫ102 meshes in the axial and radial directions, respectively. The thermodynamic and transport properties of argon 21,22) and tungsten and copper 23) are given as a function of temperature. Figure 2 shows a schematic i...

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Prediction of anode temperatures of free burning arcs

Cited by 71 publications

References 13 publications

Formation of self-organized anode patterns in arc discharge simulations

Formation of self-organized anode patterns in arc discharge simulations

Simulation of electric arc with refractory cathode and evaporating anode

Performance Evaluation of Arc-Electrodes Systems for High Temperature Materials Processing by Computational Simulation

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