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Vers un modèle numérique fiable du fonctionnement d'une torche de projection plasma à courant continu

Abstract : DC plasma spraying is a coating technology that utilizes the energy of a plasma flow to accelerate, heat up, melt and deposit the coating powder on a substrate. For a high reproducibility in coating production, the plasma flow should have low fluctuations of enthalpy and velocity, and the erosion of electrodes should be limited. Plasma torches with a cascaded anode yield a more stabilized arc length and could achieve the first goal. However, a stabilized arc does not guarantee a low erosion rate of electrodes and in particular anode. An insight into the electromagnetic and thermal processes inside the plasma torch could help to control the properties of the plasma flow issuing from the torch and extend the lifetime of the torch parts. This work dealt with the simulation of the commercial plasma torch SinplexPro™ manufactured by Oerlikon Metco operated in argon under atmospheric pressure. It involved two steps. The first consisted in developing a LTE model with the inclusion of the electrodes in the computational domain. The arc voltage and cooling loss predicted by this model were in good agreement with the experimental values for a low gas flow rate and high electric current. For such operation conditions, the model predicted a constricted anode arc attachment. Then, two methods were tested to rotate the constricted anode arc attachment: gas swirling injection and axial external magnetic field. The swirling gas injection was found to be more efficient for a gas injection angle of 45° than for an angle of 25°, which is the angle used in the actual plasma torch. The second step of this study was about the development of a two-temperature model. The latter considered two formulations for the enthalpy of electrons and heavy species differing in the attribution of the ionization energy to electrons or heavy species. The 2T model with both formulations projected a diffuse anode arc attachment and arc voltage that agreed with the experimental values for a wider range of arc current and gas flow rate. The mode of anode arc attachment was confirmed by the observation of tested anodes. The formulation of the energy equation with the ionization energy assigned to the electrons had an acceptable computational cost and yielded reasonable results in terms of electron and heavy species temperature. It will be used to develop further the model and apply it to diatomic gases.
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Submitted on : Tuesday, January 19, 2021 - 11:24:08 AM
Last modification on : Monday, January 25, 2021 - 2:36:08 PM


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  • HAL Id : tel-03114779, version 1



Rodion Zhukovskii. Vers un modèle numérique fiable du fonctionnement d'une torche de projection plasma à courant continu. Mécanique des matériaux [physics.class-ph]. Université de Limoges, 2020. Français. ⟨NNT : 2020LIMO0021⟩. ⟨tel-03114779⟩



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