On the space-charge boundary layer inside the nozzle of a cutting torch

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A numerical study of the space-charge sheath adjacent to the nozzle wall of a cutting torch is presented. The hydrodynamic model corresponds to a collision-dominated sheath and does not assume cold ions, so drift-diffusion-type equations are used. Also an improved expression for the ion-neutral mome...

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Autores principales: Prevosto, L., Kelly, H., Mancinelli, B.
Formato: Artículo publishedVersion
Lenguaje:Inglés
Publicado: 2009
Materias:
Average field
Biasing voltages
Breakdown threshold
Cold ions
Cutting torch
Drift diffusion
Electron densities
Gas breakdown
Hydrodynamic model
Ion collisions
Ion density
Ion velocity
Mean-free path
Momentum equation
Nozzle exits
Nozzle wall
Numerical studies
Plasma edges
Poisson's equation
Space charges
Space-charge sheath
Tangential components
Thermal conduction
Zero values
Carrier concentration
Electric fields
Electric potential
Electron density measurement
Fluid dynamics
Ions
Nozzles
Plasma turbulence
Poisson equation
Electron temperature
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_00218979_v105_n12_p_Prevosto
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling paperaa:paper_00218979_v105_n12_p_Prevosto2023-06-12T16:42:32Z On the space-charge boundary layer inside the nozzle of a cutting torch J Appl Phys 2009;105(12) Prevosto, L. Kelly, H. Mancinelli, B. Average field Biasing voltages Breakdown threshold Cold ions Cutting torch Drift diffusion Electron densities Gas breakdown Hydrodynamic model Ion collisions Ion density Ion velocity Mean-free path Momentum equation Nozzle exits Nozzle wall Numerical studies Plasma edges Poisson's equation Space charges Space-charge sheath Tangential components Thermal conduction Zero values Carrier concentration Electric fields Electric potential Electron density measurement Fluid dynamics Ions Nozzles Plasma turbulence Poisson equation Electron temperature A numerical study of the space-charge sheath adjacent to the nozzle wall of a cutting torch is presented. The hydrodynamic model corresponds to a collision-dominated sheath and does not assume cold ions, so drift-diffusion-type equations are used. Also an improved expression for the ion-neutral momentum transfer is employed rather than the usual constant ion-mean-free-path or constant ion collision frequency approximations. Assuming a constant electron temperature in the sheath and neglecting the electron inertial term, the continuity and momentum equations for ions and electrons, together with Poisson's equation, were solved for the electric potential, ion velocities (both normal and tangential components), and for the ion and electron densities. It was found that both the ion and electron densities present a sudden drop at the sheath-plasma edge. The ion density continues to decrease slowly inside the sheath, while the electron density presents a virtually zero value everywhere inside the sheath, the electron thermal conduction flux to the nozzle wall being negligible. These wall results thus become thermally isolated in spite of the high electron temperature in its adjacency. For a nozzle biasing voltage close to the gas breakdown, it was found that the electric field value is high, reaching a value of about 9× 106 V m-1 at the exit of the nozzle wall. This value is higher than the average field value across the sheath and is on the order of the breakdown threshold value. This means that an undesired sheath breakdown could occur at the vicinities of the nozzle exit even if the average electric field across the sheath is not strong enough. © 2009 American Institute of Physics. Fil:Kelly, H. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2009 info:eu-repo/semantics/article info:ar-repo/semantics/artículo info:eu-repo/semantics/publishedVersion application/pdf eng info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00218979_v105_n12_p_Prevosto
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
language Inglés
orig_language_str_mv eng
topic Average field
Biasing voltages
Breakdown threshold
Cold ions
Cutting torch
Drift diffusion
Electron densities
Gas breakdown
Hydrodynamic model
Ion collisions
Ion density
Ion velocity
Mean-free path
Momentum equation
Nozzle exits
Nozzle wall
Numerical studies
Plasma edges
Poisson's equation
Space charges
Space-charge sheath
Tangential components
Thermal conduction
Zero values
Carrier concentration
Electric fields
Electric potential
Electron density measurement
Fluid dynamics
Ions
Nozzles
Plasma turbulence
Poisson equation
Electron temperature
spellingShingle Average field
Biasing voltages
Breakdown threshold
Cold ions
Cutting torch
Drift diffusion
Electron densities
Gas breakdown
Hydrodynamic model
Ion collisions
Ion density
Ion velocity
Mean-free path
Momentum equation
Nozzle exits
Nozzle wall
Numerical studies
Plasma edges
Poisson's equation
Space charges
Space-charge sheath
Tangential components
Thermal conduction
Zero values
Carrier concentration
Electric fields
Electric potential
Electron density measurement
Fluid dynamics
Ions
Nozzles
Plasma turbulence
Poisson equation
Electron temperature
Prevosto, L.
Kelly, H.
Mancinelli, B.
On the space-charge boundary layer inside the nozzle of a cutting torch
topic_facet Average field
Biasing voltages
Breakdown threshold
Cold ions
Cutting torch
Drift diffusion
Electron densities
Gas breakdown
Hydrodynamic model
Ion collisions
Ion density
Ion velocity
Mean-free path
Momentum equation
Nozzle exits
Nozzle wall
Numerical studies
Plasma edges
Poisson's equation
Space charges
Space-charge sheath
Tangential components
Thermal conduction
Zero values
Carrier concentration
Electric fields
Electric potential
Electron density measurement
Fluid dynamics
Ions
Nozzles
Plasma turbulence
Poisson equation
Electron temperature
description A numerical study of the space-charge sheath adjacent to the nozzle wall of a cutting torch is presented. The hydrodynamic model corresponds to a collision-dominated sheath and does not assume cold ions, so drift-diffusion-type equations are used. Also an improved expression for the ion-neutral momentum transfer is employed rather than the usual constant ion-mean-free-path or constant ion collision frequency approximations. Assuming a constant electron temperature in the sheath and neglecting the electron inertial term, the continuity and momentum equations for ions and electrons, together with Poisson's equation, were solved for the electric potential, ion velocities (both normal and tangential components), and for the ion and electron densities. It was found that both the ion and electron densities present a sudden drop at the sheath-plasma edge. The ion density continues to decrease slowly inside the sheath, while the electron density presents a virtually zero value everywhere inside the sheath, the electron thermal conduction flux to the nozzle wall being negligible. These wall results thus become thermally isolated in spite of the high electron temperature in its adjacency. For a nozzle biasing voltage close to the gas breakdown, it was found that the electric field value is high, reaching a value of about 9× 106 V m-1 at the exit of the nozzle wall. This value is higher than the average field value across the sheath and is on the order of the breakdown threshold value. This means that an undesired sheath breakdown could occur at the vicinities of the nozzle exit even if the average electric field across the sheath is not strong enough. © 2009 American Institute of Physics.
format Artículo
Artículo
publishedVersion
author Prevosto, L.
Kelly, H.
Mancinelli, B.
author_facet Prevosto, L.
Kelly, H.
Mancinelli, B.
author_sort Prevosto, L.
title On the space-charge boundary layer inside the nozzle of a cutting torch
title_short On the space-charge boundary layer inside the nozzle of a cutting torch
title_full On the space-charge boundary layer inside the nozzle of a cutting torch
title_fullStr On the space-charge boundary layer inside the nozzle of a cutting torch
title_full_unstemmed On the space-charge boundary layer inside the nozzle of a cutting torch
title_sort on the space-charge boundary layer inside the nozzle of a cutting torch
publishDate 2009
url http://hdl.handle.net/20.500.12110/paper_00218979_v105_n12_p_Prevosto
work_keys_str_mv AT prevostol onthespacechargeboundarylayerinsidethenozzleofacuttingtorch
AT kellyh onthespacechargeboundarylayerinsidethenozzleofacuttingtorch
AT mancinellib onthespacechargeboundarylayerinsidethenozzleofacuttingtorch
_version_ 1769810079675056128

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