STUDY OF THE DYNAMIC AND STATIC BEHAVIOR OF DC VORTEX PLASMA TORCHES .2. WELL-TYPE CATHODE

This work was devoted to the study of the dynamic and static behavior of a de vortex plasma torch with a well-type cathode (power level below 100 kW). The dynamic behavior of the torch was characterized by the fluctuations of arc voltage and current, plasma jet radiation, and acoustic pressure. Characteristic frequencies of the arc root movement inside the torch were observed. By numerical simulation (with the numerical code MELODIE), it was shown that the position of the erosion area at the wall of the well-type cathode was linked to the variation (vs. its diameter) of the axial velocity along the cathode channel near the wall. The static behavior of the torch was investigated for different cathode designs. The variations of voltage U with are current I, gas flow rate G, nature of the gas, and cathode design were represented by semiempirical relationships established between dimensionless numbers. By dimensional analysis, the behavior of this torch was compared with that of two powerful torches: the Aerospatiale and tire Plasma Energy Corporation torches.