Direct Measurement of the Gas Entrainment Into a Turbulent Thermal Plasma Jet |
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Authors: | Hai-Xing Wang Fu-Zhi Wei Xian Meng Xi Chen Dong-Sheng Han Wen Xia Pan |
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Institution: | (1) School of Astronautics, Beijing University of Aeronautics and Astronautics, Beijing, 100191, China;(2) Institute of Mechanics, Chinese Academy of Sciences, Beijing, 100190, China;(3) Department of Engineering Mechanics, Tsinghua University, Beijing, 100084, China |
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Abstract: | An experimental study is conducted to investigate the entrainment characteristics of a turbulent thermal plasma jet issuing
from a DC arc plasma torch operating at atmospheric pressure. The mass flow rate of the ambient gas entrained into the turbulent
plasma jet is directly measured by use of the so-called “porous-wall chamber” technique. It is shown that a large amount of
ambient gas is entrained into the turbulent plasma jet. With the increase of the gas mass flow rate at the plasma jet inlet
or the plasma torch exit, the mass flow rate of entrained ambient gas almost linearly increases but its ratio to the jet-inlet
mass flow rate decreases. The mass flow rate of the entrained gas increases with the increase of the arc current or jet length.
It is also found that using different ways to inject the plasma-forming gas into the plasma torch affects the entrainment
rate of the turbulent plasma jet. The entrainment rate expression established previously by Ricou and Spalding (J. Fluid Mech.
11: 21, 1961) for the turbulent isothermal jets has been used to correlate the experimental data of the entrainment rates
of the turbulent thermal plasma jet, and the entrainment coefficient in the entrainment rate expression is found to be in
range from 0.40 to 0.47 for the turbulent thermal plasma jet under study. |
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