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Progress in Plasma Processing of Materials, 1999

ISBN:
1-56700-126-2 (Print)

INVESTIGATION OF STRUCTURE OF TURBULENT BOUNDARY LAYER BETWEEN THERMAL PLASMA JET AND AMBIENT AIR

Milan Hrabovsky
Institute of Plasma Physics, Academy of Sciences Za Slovankou 3, 182 00, Prague

M. Konrad
TECOSIM Technische Simulation Gmbh Robert-Bosch-Str. 10, D-50769 Collogne, Germany; and Institute of Plasma Physics, Za Slovankou 3, 182 00, Praha 8, Czech Republic

Vladimir Kopecky
Thermal Plasma Department, Institute of Plasma Physics AS CR, Za Slovankou 3, 18200, Praha 8, Czech Republic

Abstract

The structure of flow field in plasma jet was investigated by means of electrostatic probes. Plasma jet was generated in plasma torch with dc electric arc stabilized by water vortex. The generated plasma is characterized by very high temperature and velocity and low density. An array of several electric probes was moved across the jet in various axial positions. The lines of the same probe current were evaluated from the measured signals. These lines represent the lines of the same plasma properties. The process of entrainment of ambient cold gas at the jet boundary and production of separated plasma eddies surrounded by cold gas was visualized by the applied method. Characteristic dimensions of jet structures and their velocity were determined.