2016 №01 (08) DOI of Article
2016 №01 (02)

Automatic Welding 2016 #01
Avtomaticheskaya Svarka (Automatic Welding), #1, 2016, pp. 3-13

Characteristics of non-equilibrium arc plasma in plasmatron nozzle channel

A.V. Ignatov1, I.V. Krivtsun1 and I.L. Semenov3

1Guangdong General Research Institute of Industrial Technology (Guangzhou Research Institute of Non-Ferrous Metals), Guangzhou, PRC
2E.O. Paton Electric Welding Institute, NASU 11 Kazimir Malevich Str., 03680, Kiev, Ukraine. E-mail: office@paton.kiev.ua
3German Aerospace Center (DLR) Munich, Germany. E-mail: igor_semenov@list.ru
A mathematical model was developed for processes of energy, pulse, mass and discharge transfer in non-equilibrium plasma of electric arc, burning in cylindrical channel with water-cooled walls being blown out by laminar flow of plasma inert gas. The model is based on multi-fluid equations for nonisothermal, ionization non-equilibrium arc plasma, considering double ionization of atoms of the plasma gas written in a drift-diffusion approximation. Such an approach allows uniform description of the processes taking place in central region of the channel (in arc column plasma) as well as near-wall region (in plasma ionization layer) up to interface of space charge layer directly adjacent to channel wall. Consideration of the processes taking place in collisionless layer of space discharge and determination of characteristics of thermal and electric interaction of arc plasma with channel wall is carried out using corresponding boundary conditions on interface of the indicated layer. Besides, if presence of doubly charged ions in arc plasma is taken into account, it is possible to calculate its characteristics in a wide range of values of arc current and channel radius. Numerical solution of equations of the proposed model is carried out by finite volume method. Corresponding software is developed for computer realization. Detailed numerical analysis is given to radial distribution of characteristics of argon arc plasma in the cylindrical channels of direct plasmatron nozzle as well as intensity of longitudinal electric field in arc plasma and heat flow from plasma to channel wall at different values of arc current, channel radius and consumption of plasma gas. It is shown that in contrast to the central regions of the channel, where arc plasma is virtually equilibrium, a significant thermal and ionization non-equilibrium of plasma is realized in the near-wall region. It is also shown that increase of arc current and reduction of channel radius requires consideration of the doubly charge ions present in arc plasma. Comparison of results of modelling of characteristics of the non-equilibrium argon arc plasma in the plasmatron nozzle channel with available experimental data was carried out. 11 Ref., 1 Table, 9 Figures.
Keywords: arc plasmatron, plasma-shaping channel, electric arc in channel, non-equilibrium plasma, mathematical modelling
Received:                24.09.15
Published:               15.03.16
  1. Meier, E.T., Shumlak, U. (2012) A general nonlinear fluid model for reacting plasma-neutral mixtures. Physics of Plasma, 19, 072508. https://doi.org/10.1063/1.4736975
  2. Benilov, M.S. (1995) The ion flux from a thermal plasma to a surface. Phys. D: Appl. Phys., 28, 286–294. https://doi.org/10.1088/0022-3727/28/2/010
  3. Benilov, M.S., Marotta, A. (1995) A model of the cathode region of atmospheric pressure arcs. Ibid., 28, 1869–1882. https://doi.org/10.1088/0022-3727/28/9/015
  4. Almeida, N.A., Benilov, M.S., Naidis, G.V. (2000) Simulation of the layer of non-equilibrium ionization in a high-pressure argon plasma with multiply-charged ions. Ibid., 33, 960–967. https://doi.org/10.1088/0022-3727/33/8/312
  5. Almeida, N.A., Benilov, M.S., Naidis, G.V. (2008) Unified modelling of near-cathode plasma layers in high-pressure arc discharges. Ibid., 41, 245201. https://doi.org/10.1088/0022-3727/41/24/245201
  6. Almeida, N.A., Benilov, M.S., Hechtfischer, U. (2009) Investigating near-anode plasma layers of very high-pressure arc discharges. Ibid., 42, 045210. https://doi.org/10.1088/0022-3727/42/4/045210
  7. Engelsht, V.S., Gurovich, V.Ts., Desyatkov, G.A. et al. (1990) Low-temperature plasma. Vol. 1: Theory of electric arc column. Novosibirsk: Nauka.
  8. Beulens, J.J., Milojevic, D., Schram, D.C. et al. (1991) A two-dimensional nonequilibrium model of cascaded arc plasma flows. Fluids B, 3(9), 2548–2557. https://doi.org/10.1063/1.859967
  9. Ignatov, A.V., Semenov, I.L. (2015) Characteristics of nonequilibrium arc plasma in channel of plasmatron nozzle. In: of 8th Int. Conf. of Junior Scientists on Welding and Related Technologies (Vorzel, Ukraine, 2015).
  10. Benilov, M.S. (1996) Multifluid equations of a plasma with various species of positive ions and the Bohm criterion. Phys. D: Appl. Phys., 29, 364–368. https://doi.org/10.1088/0022-3727/29/2/012
  11. Manteuffel, T.A., White, A.B. (1986) The numerical solution of second-order boundary value problems on nonuniform meshes. Mathematics of Computation, 47, 511–535. https://doi.org/10.1090/S0025-5718-1986-0856700-3