Modelling of the arc reattachment process in plasma torches

The need to improve plasma spraying processes has motivated the development of computational models capable of describing the arc dynamics inside plasma torches. Although progress has been made in the development of such models, the realistic simulation of the arc reattachment process, a central par...

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Bibliographic Details
Published in:Journal of physics. D, Applied physics Applied physics, 2007-09, Vol.40 (18), p.5635-5648
Main Authors: Trelles, J P, Pfender, E, Heberlein, J V R
Format: Article
Language:English
Subjects:
Exact sciences and technology
Physics
Physics of gases, plasmas and electric discharges
Physics of plasmas and electric discharges
Plasma devices
Plasma dynamics and flow
Plasma properties
Plasma torches
Transport properties
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Summary:The need to improve plasma spraying processes has motivated the development of computational models capable of describing the arc dynamics inside plasma torches. Although progress has been made in the development of such models, the realistic simulation of the arc reattachment process, a central part of the arc dynamics inside plasma torches, is still an unsolved problem. This study presents a reattachment model capable of mimicking the physical reattachment process as part of a local thermodynamic equilibrium description of the plasma flow. The fluid and electromagnetic equations describing the plasma flow are solved in a fully-coupled approach by a variational multi-scale finite element method, which implicitly accounts for the multi-scale nature of the flow. The effectiveness of our modelling approach is demonstrated by simulations of a commercial plasma spraying torch operating with Ar-He under different operating conditions. The model is able to match the experimentally measured peak frequencies of the voltage signal, arc lengths and anode spot sizes, but produces voltage drops exceeding those measured. This finding, added to the apparent lack of a well-defined cold boundary layer all around the arc, points towards the importance of non-equilibrium effects inside the torch, especially in the anode attachment region.
ISSN:0022-3727
1361-6463
DOI:10.1088/0022-3727/40/18/019