Predicted Anode Arc Attachment by Local Thermodynamic Equilibrium (LTE) and Two-Temperature Arc Models in a Cascaded-Anode dc Plasma Spray Torch

Abstract Anode erosion is a common concern in dc plasma spray torches. It depends largely on the heat flux brought by the arc and the dimensions, residence time, and mode of the arc attachment to a given location on the anode wall. This paper compares anode arc attachment modes predicted by LTE (local thermodynamic equilibrium) and 2-T (two-temperature) arc models that include the electrodes in the computational domain. The analysis is based on a commercial cascaded-anode plasma torch operated at high current (500 A) and low gas flow rate (60 NLPM of argon). It shows that the LTE model predicted a constricted anode arc attachment that moves on the anode ring while the 2-T model predicted a diffuse and steady arc attachment. The comparison between the predicted and measured arc voltage indicated that the 2-T prediction is closer to the actual voltage. A post-mortem observation of a new anode ring on a plasma torch operated under the same conditions confirmed the diffuse arc attachment predicted by the 2-T arc model.

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Predicted Anode Arc Attachment by LTE (Local Thermodynamic Equilibrium) and 2-T (Two-Temperature) Arc Models in a Cascaded-Anode DC Plasma Spray Torch

Journal of Thermal Spray Technology ◽

10.1007/s11666-021-01253-4 ◽

2021 ◽

Author(s):

Rodion Zhukovskii ◽

Christophe Chazelas ◽

Vincent Rat ◽

Armelle Vardelle ◽

Ron Molz

Keyword(s):

Thermodynamic Equilibrium ◽

Plasma Spray ◽

Plasma Torch ◽

Gas Flow ◽

Local Thermodynamic Equilibrium ◽

Computational Domain ◽

Dc Plasma ◽

Anode Plasma ◽

Short Time ◽

Two Temperature

AbstractIn DC plasma spray torches, anode erosion is a common concern. It mainly depends on the heat flux brought by the arc and on the dimensions and residence time of the arc attachment to a given location on the anode wall. The latter depend, to a great extent, on the attachment mode of the arc on the anode wall. This paper compares the anode arc attachment modes predicted by an LTE (Local Thermodynamic Equilibrium) and 2-T (two-temperature) arc models that include the electrodes in the computational domain. It deals with a commercial cascaded-anode plasma torch operated at high current (500 A) and low gas flow rate (60 NLPM of argon). It shows that the LTE model predicted a constricted anode arc attachment that moves on the anode ring, while the 2-T model predicted a diffuse and steady arc attachment. The comparison between the predicted and measured arc voltage showed that the 2-T prediction is closer to the actual voltage. Also, the post-mortem observation of a new anode ring of the actual plasma torch operated under the same conditions for a short time confirmed a diffuse arc attachment on a new anode.

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Account of diffusion in local thermodynamic equilibrium and two-temperature plasma models

Journal of Physics D Applied Physics ◽

10.1088/1361-6463/ab34c1 ◽

2019 ◽

Vol 52 (45) ◽

pp. 454003

Author(s):

D F N Santos ◽

M Lisnyak ◽

M S Benilov

Keyword(s):

Thermodynamic Equilibrium ◽

Local Thermodynamic Equilibrium ◽

Temperature Plasma ◽

Two Temperature

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Flow study in structure of the plasma torch for microwave plasma spray

Journal of Modern Manufacturing Systems and Technology ◽

10.15282/jmmst.v4i2.5251 ◽

2020 ◽

Vol 4 (2) ◽

pp. 56-60

Author(s):

Muhammad Fahmi Izuwan Samion ◽

Nur Ziana Norizat ◽

Ahmad Redza Ahmad Mokhtar

Keyword(s):

Reynolds Number ◽

Laminar Flow ◽

Plasma Spray ◽

Plasma Torch ◽

Gas Flow ◽

Microwave Plasma ◽

Microwave Oven ◽

Outer Diameter ◽

Flow Rates ◽

Suitable Structure

Microwave oven induced plasma method is a novel application of microwave oven to generate plasma for coating process. It uses 2.45 GHz microwave power and only 0.8 kW input power to produce the plasma which capable of spraying all materials that are considered sprayable. However, the research regarding this microwave plasma spray are more to be discovered. Suitable structure of plasma torch is needed for microwave plasma spray that can produce laminar flow to produce desire plasma for coating application. Therefore, this paper will discuss about the suitable structure of plasma torch needed for laminar flow by Reynolds number calculation. Reynolds number calculated by applying the outlet diameter of antenna which is 2, 3 and 4 mm. From this research, Reynolds number from all outer diameter of antenna are below 2000 which indicate laminar flow. The widest plasma diameter achieved at 6.59 mm with 4 mm outlet diameter of antenna and 15 lpm working gas flow rate while the narrowest plasma diameter achieved at 1.26 mm with 3 mm outlet diameter of antenna and 10 lpm flow rates of working gas. The most acceptable condition for producing plasma plume was at 3 mm of antenna diameter with 25 lpm of Ar gas flow rates.

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Model of a non-transferred arc cascaded-anode plasma torch: the two-temperature formulation

Journal of Physics D Applied Physics ◽

10.1088/1361-6463/ac2cec ◽

2021 ◽

Author(s):

Rodion Zhukovskii ◽

Christophe Chazelas ◽

Vincent Rat ◽

Armelle Vardelle ◽

Ron Molz

Keyword(s):

Plasma Torch ◽

Transferred Arc ◽

Anode Plasma ◽

Two Temperature

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Blackbody Radiation, Boltzmann Statistics, Temperature, and Thermodynamic Equilibrium

10.1093/oso/9780199662104.003.0003 ◽

2017 ◽

Author(s):

Kelly Chance ◽

Randall V. Martin

Keyword(s):

Thermodynamic Equilibrium ◽

Local Thermodynamic Equilibrium ◽

Photophysical Properties ◽

Blackbody Radiation ◽

Boltzmann Constant ◽

Noise Sources ◽

Atmospheric Molecules ◽

Tightly Coupled ◽

Boltzmann Statistics ◽

Planck’S Law

Blackbody radiation, temperature, and thermodynamic equilibrium give a tightly coupled description of systems (atmospheres, volumes, surfaces) that obey Boltzmann statistics. They provide descriptions of systems when Boltzmann statistics apply, either approximately or nearly exactly. These apply most of the time in the Earth’s stratosphere and troposphere, and in other planetary atmospheres as long as the density is sufficient that collisions among atmospheric molecules, rather than photochemical and photophysical properties, determine the energy populations of the ensemble of molecules. Thermodynamic equilibrium and the approximation of local thermodynamic equilibrium are introduced. Boltzmann statistics, blackbody radiation, and Planck’s law are described. The chapter introduces the Rayleigh-Jeans limit, description of noise sources as temperatures, Kirchoff’s law, the Stefan-Boltzmann constant, and Wien’s law.

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