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Modeling of an induction plasma under transient turbulent flow conditions

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3 Author(s)
Ye, R. ; National Institute for Materials Science, Advanced Materials Laboratory, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan ; Ishigaki, T. ; Boulos, M.I.

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A renormalization group (RNG) k-Є turbulence model was employed to investigate the role of turbulence for the transient behavior of the radio frequency induction plasma discharge. Time-dependent conservation equations for the plasma and turbulence under local thermal equilibrium (LTE) conditions were solved numerically in two-dimensional, axisymmetric coordinates. Responses of energy, momentum, and turbulence to steplike and pulsed power changes in an Ar-H2 plasma with a hydrogen volume concentration of 10.9%, and a total gas flow rate of 104.0 slpm were studied. The corresponding Reynolds number at the inlet of the discharge cavity was 2667. The turbulence model was validated qualitatively by comparing the predicted results with experimental observations under pulsed power conditions. It is found the transient behavior of the plasma energy and momentum are mainly governed by radial convection, while that of the turbulence is primarily determined by axial convection. These gave rise to a 5–10 ms delay in the response of the turbulence lagging behind the temperature field, for sudden power changes, under current operating conditions. A comparison between the results predicted using the RNG k-Є turbulence model and those obtained using the laminar model indicates the presence of turbulence leads to a longer relaxation time of plasma. Under pulsed power conditions, the plasma temperature responds to power changes almost instantaneously, and it is always in a transient state. In contrast, variation in the relative turbulent viscosity is insignificant and it is concluded that the turbulence is in a quasisteady state when the period of a pulse is between 10 and 15 ms. By comparing the predicted results with images obtained using a high-speed camera (0.67 ms/frame) under the same operating conditions, we found that the turbulence model predicted a more accurate transien- t behavior in terms of plasma volume and temperature than the laminar model does. © 2004 American Institute of Physics.

Published in:

Journal of Applied Physics  (Volume:96 ,  Issue: 1 )