Thermal Plasmas

Boulos, Maher I.; Fauchais, Pierre; Pfender, E.

doi:10.1007/978-1-4899-1337-1

Cited by 883 publications

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“…The plasma composition can be determined by: the mass action law (minimization of Gibbs free energy), Dalton's law of partial pressures, and the quasi-neutrality condition [28]. The present study considers a four-species argon plasma, composed of the species: Ar, Ar + , Ar ++ , and e -(i.e., argon atoms, single ionized ions, doubly ionized ions, and free electrons).…”

Section: Materials Properties and Constitutive Relationsmentioning

confidence: 99%

“…Table 6 shows the values of J qmax and r cath for the values of I tot simulated (i.e., from 100 to 300 [A] in intervals of 25 [A]). A value of n cath = 4 has been used for all J qcath profiles, whereas a value of n cath = 1 has been traditionally used for sharply conical cathodes or truncated two-dimensional computational domains (e.g., [29,68,76] varies approximately linearly with I tot ; this functional dependency produces the expected behavior of the cathode jet [28], as described in the following section. T from Hsu and Pfender [29] (left).…”

Section: Boundary Variablementioning

confidence: 99%

“…The free-burning arc is a canonical thermal plasma flow in which an electric arc, formed by a constant DC current between a conical cathode aligned vertically on top of a flat horizontal anode in the absence of external forcing (e.g., auxiliary gas flow, imposed magnetic field), establishes a recirculating flow of gas and a corresponding bellshaped optical emission pattern from the plasma [28]. Due to its relative simplicity and relevance in diverse technological applications (e.g., arc welding, metallurgy, circuit breakers), the freeburning arc has been extensively studied, both experimentally and computationally, and is commonly used for benchmarking computational plasma flow models [29, 27, 60-71, 73, 74].…”

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confidence: 99%

“…Furthermore, thermal plasmas are traditionally described using models based on the Local Thermodynamic Equilibrium (LTE) assumption. The energy of heavy-species (molecules, atoms, ions) and the free electrons in a plasma in LTE, due to the high collision frequencies among its constituent particles, can be characterized by a single temperature [28]. The LTE approximation is largely valid in the core of the plasma, but it is often invalid when the plasma interacts with another medium, such as solid electrodes or a surrounding cold gas.…”

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confidence: 99%

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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: Materials Properties and Constitutive Relationsmentioning

confidence: 99%

Section: Boundary Variablementioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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Formation of self-organized anode patterns in arc discharge simulations

Trelles

2013

Plasma Sources Sci. Technol.

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“…Data on the thermodynamic and transport properties of nitrogen is available in Ref. [3]. The 10-mm-long coaxial tubes are set on the z-axis in the cylindrical polar coordinates.…”

Section: Modeling For Stable Arc Discharge With Flowmentioning

confidence: 99%

Stable Arc Discharge Modeling with Flow for Carbon Nanohorn Synthesis by Assuming an Isobaric Environment

Nishikawa

Hayashi

Kitamura³

2014

Proceedings of the 12th Asia Pacific Physics Conference (APPC12)

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We have devised a simple model for obtaining hydrodynamic properties in plasmas generated by a stable arc discharge with gas flow. We considered a high-temperature, uniform-column plasma as the arc and assumed that its pressure was equal to the outer surrounding gas flow. Using this model, we could solve the energy fluxes from the arc plasma into the outer gas flow and obtain various hydrodynamic properties in the plasmas of carbon nanohorn synthesis. To demonstrate the usefulness of the model, we chose a nitrogen flow typically used in experiments for carbon nanohorn synthesis. The relationships among the plasma temperature, size of the plasma, and velocity of the outer gas flow are also discussed.

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Emission Spectroscopy and Mie Scattering on an Inductively Coupled Plasma Torch

Lins¹

2000

Contrib. Plasma Phys.

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Plasma flash evaporation uses an inductively generated thermal high‐power plasma to deposit films immediately out of the vapour phase of material introduced into the plasma as a powder. In an attempt to assess the suitability of the method for the deposition of yttria‐stabilised zirconia coatings, the plasma temperature was measured in the absence and in the presence of evaporating zirconia (ZrO2) powder, and the evaporation behaviour was investigated by Mie scattering. It was found that hydrogen as an admixture to the plasma‐forming gas was superior to oxygen, because of its more favourable thermal conduction properties. When the plasma was loaded with ZrO2 powder at a rate of 100 mg/min the temperature dropped by 2,000 K but remained still high enough for the existence of (ZrO2) vapour. Finally, with an appropriate plasma composition, ZrO2 powder with a maximum grain size not significantly exceeding 12 μm could be completely evaporated at a powder feed rate of 180 mg/min.

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Thermal Plasmas

Cited by 883 publications

References 0 publications

Formation of self-organized anode patterns in arc discharge simulations

Formation of self-organized anode patterns in arc discharge simulations

Stable Arc Discharge Modeling with Flow for Carbon Nanohorn Synthesis by Assuming an Isobaric Environment

Emission Spectroscopy and Mie Scattering on an Inductively Coupled Plasma Torch

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