The electrical boundary layer and current transfer between a thermal plasma and a plane electrode
- Stanford Univ., CA (United States). Mechanical Engineering Dept.
A two-temperature, multi-fluid model of a plasma in stagnation flow against a cooled, electrically biased surface is presented. The model presented here is an extension of an earlier quasi-neutral formulation, and couples bulk fluid motion, species diffusion and convection, electron and bulk energy equations, and net finite-rate ionization with poisson`s equation for the electric field in a generalized formulation. Application of the model to the case of an atmospheric pressure argon plasma flow reveals important interactions between thermal, hydrodynamic, chemical, and electrical boundary layers, with implications to current-limiting regimes of electrode performance. An example of the simulated current-voltage response of an electrode in contact with an atmospheric pressure argon plasma (free stream conditions of 6,000 K and 2,400 cm/s incident velocity) in stagnation flow is provided in the accompanying figure. The analysis also examines the response of a planar, Langmuir probe in contact with a collisional, flowing plasma. The simulated current-voltage behavior of the probe is compared to simple probe theory. Departures from simple theory arise from boundary layer perturbations near the electrode surface, away from free-stream conditions. The computational model incorporates a finite-rate catalytic recombination of ions and electrons at the electrode surface together with a specified current. These boundary conditions determine electron and ion fluxes at the electrode surface consistent with mass and charge conservation. While the value of the net recombination rate is unknown, the dependence of the calculated sheath strength on this rate can be investigated.
- OSTI ID:
- 51760
- Report Number(s):
- CONF-940604--; ISBN 0-7803-2006-9
- Country of Publication:
- United States
- Language:
- English
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