Measurement of Emission and Absorption of Radiation by an Argon Plasma

Evans, D. L.

doi:10.1063/1.1762256

Cited by 232 publications

(85 citation statements)

References 15 publications

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“…Figure 3 shows a comparison of the emission coefficient of an argon plasma at different pressures with values given by Menart et al [19] and measurements done by Evans et al [47]. The wavelength integration covers here the interval from 200 to 3500 nm corresponding to the sensitivity of the experiment [47]. Both numerical results are identical to within 10 % and lie slightly above the experimental results.…”

Section: Emission Coefficients Of Pure Argon and Ironsupporting

confidence: 73%

“…For argon corresponding temperatures are above 30000 K ( figure 1). Figure 3 shows a comparison of the emission coefficient of an argon plasma at different pressures with values given by Menart et al [19] and measurements done by Evans et al [47]. The wavelength integration covers here the interval from 200 to 3500 nm corresponding to the sensitivity of the experiment [47].…”

Section: Emission Coefficients Of Pure Argon and Ironmentioning

confidence: 99%

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Net emission coefficients of argon iron plasmas with electron Stark widths scaled to experiments

Wendt¹

2011

J. Phys. D: Appl. Phys.

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The net emission coefficient of plasmas containing argon and iron at atmospheric pressure is calculated and analysed for the case of cylindrical geometry. Its values are obtained by integrating the monochromatic net emission coefficient taking into account continuous and line radiation. The width of the spectral lines is determined by Doppler broadening, natural, resonance, van der Waals, electron and ion Stark broadening. As Stark broadening is the most important broadening mechanism in the considered pressure and temperature range, the electron Stark widths are calculated following the semi-empirical Stark broadening theory. Additionally, the electron Stark widths of Ar, Ar+, Fe and Fe+ are multiplied by scaling factors in order to reproduce experimental electron Stark widths. The scaling factor is determined for each species separately. For small plasma radii the net emission coefficient determined here shows good agreement with literature values where spherical geometry is considered while they decrease faster with increasing plasma radius. This behaviour is caused by the increase of the irradiation of the symmetry axis when cylindrical instead of spherical geometry is considered. For radii and temperatures typical of the metal filled core of arcs occurring in gas metal arc welding processes, i.e. radii between 1 and 2 × 10−3 m and temperatures between 5000 and 10 000 K, the scaling of the Stark widths increases the net emission coefficient of iron plasmas by between 2% and 23%. In this parameter range the net emission coefficient of iron plasmas for cylindrical geometry is between 30% and 37% smaller than values calculated for spherical geometry.

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Section: Emission Coefficients Of Pure Argon and Ironsupporting

confidence: 73%

Section: Emission Coefficients Of Pure Argon and Ironmentioning

confidence: 99%

Net emission coefficients of argon iron plasmas with electron Stark widths scaled to experiments

Wendt¹

2011

J. Phys. D: Appl. Phys.

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“…The thermodynamic properties were calculated according to the data given by Murphy [25] for a temperature range of between 300 and 30000 K. Radiative effects are considered by use of the net emission coefficient (NEC) model. Reliable NEC data are available for argon [26] and iron vapour [27] as well. For mixtures of both species, the net emission coefficient can be determined as a mole-fraction weighted average as recommended by Cressault et al [28].…”

Section: Numerical Analysis Of Particular Laser-arc Interaction Phenomentioning

confidence: 99%

Process characteristics of fibre-laser-assisted plasma arc welding

Mahrle¹,

Schnick²,

Rose³

et al. 2011

J. Phys. D: Appl. Phys.

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Abstract. Experimental and theoretical investigations on fibre-laser assisted plasma arc welding (LAPW) have been performed. Welding experiments were carried out on aluminium and steel sheets. In case of a highly focused laser beam and a separate arrangement of plasma torch and laser beam, high-speed video recordings of the plasma arc and corresponding measurements of the time-dependent arc voltage revealed differences in the process behaviour for both materials. In case of aluminium welding, a sharp decline in arc voltage and stabilization and guiding of the anodic arc root was observed whereas in steel welding the arc voltage was slightly increased after the laser beam was switched on. However, significant improvement of the melting efficiency with the combined action of plasma arc and laser beam was achieved for both types of material. Theoretical results of additional numerical simulations of the arc behaviour suggest that the properties of the arc plasma are mainly influenced not by a direct interaction with the laser radiation but by the laser induced evaporation of metal. Arc stabilization with increased current densities is predicted for moderate rates of evaporated metal only whereas metal vapour rates above a certain threshold causes a destabilization of the arc and reduced current densities along the arc axis.

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“…Other coefficients of the problem like C A p , C G p , k A , k G and σ were obtained from Ref. [9] for the temperature range 300 − 45000 K. Radiative losses from the arc were included by considering that the total radiation field is composed by ∼ 50% of continuous radiation and another 50% of line radiation [10,11]. The surrounding gas is considered to be transparent to continuous radiation but opaque to line radiation.…”

Section: ∂ ∂Zmentioning

confidence: 99%

Hydrodynamic model for the plasma-gas flow in a cutting torch nozzle

Kelly¹,

Minotti²,

Prevosto³

et al. 2004

Braz. J. Phys.

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We present a simple hydrodynamic model to obtain the profiles of the relevant physical quantities along a nozzle of arbitrary cross-section in a cutting torch. The model uses a two-zone approximation (a hot central plasma carrying the discharge current wrapped by a relatively cold gas which thermally isolates the nozzle wall from the plasma). Seeking for a solution with sonic conditions at the nozzle exit, the model allows expressing all the profiles in terms of the externally controlled parameters of the torch (geometry of the torch, discharge current, mass flow of the gas and plenum pressure) and the values of the arc and gas temperatures at the nozzle entrance. These last two values can be estimated simply appealing to energy conservation in the cathode-nozzle region. The model contains additional features compared with previous reported models, while retaining simplicity. The detailed consideration of an arc region coupled to the surrounding gas dynamics allows determining voltage drops and consequent delivered power with less assumptions than those found in other published works, and at the same time reduces the set of parameters needed to determine the solution.

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Measurement of Emission and Absorption of Radiation by an Argon Plasma

Cited by 232 publications

References 15 publications

Net emission coefficients of argon iron plasmas with electron Stark widths scaled to experiments

Net emission coefficients of argon iron plasmas with electron Stark widths scaled to experiments

Process characteristics of fibre-laser-assisted plasma arc welding

Hydrodynamic model for the plasma-gas flow in a cutting torch nozzle

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