LOADING AND RADIATION EFFECTS IN PLASMA JET MODELLING

M- L'effet de l'interaction plasma-particules et de la prksence de vapeurs mktalliques provenant de l'bvaporation des particules est Btudit? il l'aide d'un modkle mathkmatique. On trouve que le chauffage des particules ainsi que l'augmentation du rayonnement du aux vapeurs mBtalliques provoquent un fefroidissement trks important du plasma. La taille &S particules a un effet dbterminant sur ces deux phknomknes.- The plasma-particle interaction and the effect of the presence of metallic vapors from the evaporating particles is studied using a mathematical model. It is found that the particle heating and the increase in radiative losses due to the metallic vapors are responsible for the important cooling of the plasma. The particle size is a critical parameter for these two effects. In a d.c. plasma jet, the size of the hot luminous core is significantly smaller than in induction RFplasmas of the same power level. Even if the maximum temperatures may be higher in d.c. plasmas, radiation usually plays a minor role in the overall energy balance of the jet. However, in view of recent studies on the radiative power of plasmasin the presence of metallic vapoursll-21, it seems that even in plasma jets the increasedradiative losses may have a significant effect on the associated temperature fields. Essoltani et a 1 1 have demonstrated that iron vapors in an argon plasma increases the radiative losses of the plasma by orders of magnitude even for small iron concentrations