Forescast of the chemical and transport properties of a carbon oxyen plasma in isochoric conditions

International audienceThe composition and transport properties of CO2, CO, CH4, CO + Ar, CO + Fe have been calculated at constant volume. Except at low temperature (T < 3,000 K) with the formation of condensed species or more complex molecules, pressure increases with temperature at constant volume. For example, 1 mole of CH4 starting at 0.1 MPa and 298 K can reach 35 MPa at 20,000 K. The net result is a shift to a higher temperature of dissociation and ionization. The electrical conductivity ae at constant volume increases drastically relatively to that obtained at 0.1 MPa over 15,000 K, in spite of the decrease of the electron density ne. The decrease is due to the increase of neutral species ni with a much lower electron-neutral species collision cross section σei (σe is increased proportionally to the inverse of ni*σei). The viscosity always exhibits a maximum when the ionization degree reaches 3% but this maximum is shifted to a higher temperature and its peak value is higher. The thermal conductivity peak due to dissociation is shifted to higher temperature and its value is reduced while the conductivity peak due to ionization, again being shifted to higher temperature, is increased in its value

Faut-il traiter systématiquement les embolies pulmonaires découvertes fortuitement ?

International audienc

Fast modelling of plasma jet and particle behaviours in spray conditions

International audienceThis paper presents a simplified code allowing to find in a few minutes the trends of the d.c. plasma spray process, at least for a single particle in flight. It is based on a parabolic two dimension (2D) flow for the plasma jet and a three dimension (3D) calculation for the heat and momentum transfer to a single particle. It neglects the carrier gas flow rate- plasma flow interaction but the obtained trends are in good agreement with those obtained with 3D sophisticated codes. However results depend strongly on the turbulence model, the plasma effect corrections chosen for the heat and momentum transfer. Thus, as with 3D codes, the model has to be backed by experiments. It can be used to train operators and let them “see” almost immediately the effects of the different macroscopic spray parameters. The code and the plasma properties used can be freely downloaded

CALCULS DES PROPRÉTÉS THERMODYNAMIQUES ET DE TRANSPORT DES PLASMAS Ar-N2 ET Ar-NH3 À LA PRESSION ATMOSPHÉRIQUE

Les propriétés thermodynamiques et de transport de mélanges Al-N2 et Al-NH3 pour la synthèse de nitrure d'aluminium par arc transféré plasma sont calculées. Dans le cas de vapeur d'aluminium métallique en présence de plasma d'azote ou d'ammoniac, une approche thermodynamique donne les conditions de composition initiale et de température qui conduisent à de bonnes conditions expérimentales pour la réaction en phase gazeuse. Les calculs des compositions des mélanges et des propriétés de transport (conductivité thermique, viscosité, coefficient de diffusion des différentes espèces...) permettent de prévoir le comportement des arcs transférés et le taux d'aluminium vaporisé