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High Temperature Material Processes: An International Quarterly of High-Technology Plasma Processes
SJR: 0.19 SNIP: 0.341 CiteScore™: 0.43

ISSN Print: 1093-3611
ISSN Online: 1940-4360

High Temperature Material Processes: An International Quarterly of High-Technology Plasma Processes

DOI: 10.1615/HighTempMatProc.v8.i2.50
pages 207-214

INFLUENCE OF EXTERNAL PRESSURE ON TURBULENT PHENOMENA IN A THERMAL PLASMA JET

J. Hlina
Institute of Thermomechanics, Academy of Sciences of the Czech Republic, Dolejskova 5, 182 00 Praha 8, Czech Republic
J. Sonsky
Institute of Thermomechanics, Academy of Sciences of the Czech Republic, Dolejskova 5, 182 00 Praha 8, Czech Republic
V. Nenicka
Institute of Electrical Engineering, Academy of Sciences of the Czech Republic, Dolejskova 5, 182 02 Praha 8, Czech Republic
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
O. Chumak
Thermal Plasma Department, Institute of Plasma Physics AS CR, Za Slovankou 3, 18200, Praha 8, Czech Republic

ABSTRACT

A dc hybrid Ar-water plasma torch attached to a vacuum vessel was used for the experiment. Plasma optical radiation from the jet was recorded by a fast CCD camera adapted for acquisition of image series containing 8 pictures of the plasma jet with time intervals 4 μs and exposure time 200 ns. The conditions for the onset of turbulence in the plasma jet were varied by changing the pressure in the vacuum vessel between 10 and 80 kPa. The analysis of the acquired images was based on subtraction of matrices representing succeeding pictures in the series. This method reveals turbulent structures characterized by increasing or decreasing luminosity moving along the flow. The evaluation of the results included statistical analysis of the number, size and velocity of the detected structures. The statistical distributions of these quantities approach Gaussian shapes at low pressures. A significant transition in the flow behaviour occurs between 30 and 40 kPa.


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