Effect of Vortex Motion of Stabilizing Liquid Wall on Properties of Arc in Water Plasma Torch a JIŘÍ JENIŠTA, MILAN HRABOVSKÝ, VLADIMÍR KOPECKÝ Institute of Plasma Physics AS CR, Za Slovankou 3, 182 21 Praha 8, Czech Republic ABSTRACT: In water stabilized plasma torches an electric arc is ignited in a centre of water vortex which is created in cylindrical arc chamber with tangential water injection. The arc is stabilized by an interaction with inner wall of the vortex. Principle physical mechanisms which control arc properties and parameters of generated plasma jet are evaporation of water wall and heating and ionization of vapour flowing from the wall into the arc column. The vortex movement of water is necessary to maintain fixed shape of inner wall of the vortex due to inertial forces. Published model of mechanisms of water stabilized arc does not consider effect of movement of water on mechanisms of arc 1 . The aim of investigation described in this paper is theoretical and experimental study of the effect of movement of water and induced tangential component of velocity of plasma in the arc column on properties of arc and generated plasma jet. PHYSICAL MODEL The published numerical model of water stabilized arc 2 does not take tangential movement of the discharge into account. It can be expected that a part of rotating momentum of a swirl is transferred to the arc plasma, i.e. the plasma discharge is rotating with nonzero tangential velocity. Thus the two-and-half dimensional axisymmetric model including the arc discharge area between the cathode and the outlet nozzle of the torch has been formulated. The following assumptions are applied: The plasma flow is assumed to be steady, laminar, mildly compressible in the state of local thermodynamic equilibrium. Radiation effects are involved through the net emission coefficient; absorption of radiation in water vapours is omitted. Magnetic field is generated only by the arc itself, gravity effects and viscous dissipation are negligible. The mass flow rate of water vapour, i.e. production of plasma material itself, is assumed to be uniform along the discharge and its value is derived from experiments. The set of governing two- dimensional equations is written, for a computer implementation, in an axisymmetric cylindrical system of coordinates. The governing equations can be written in cylindrical coordinates as follows: continuity equation: ( ) ( ) ¶ ¶ r ¶ ¶ r ¶ ¶ r t r r vr x u + + = 1 0 , (1) a Financial support from the Grant Agency of the Czech Republic under projects No. 106/96/K245 and 102/98/0813 is gratefully acknowledged.