Abstract
Numerical analyses on the electrical coupling of a DC-RF (direct current - radio frequency) hybrid plasma torch are conducted on the basis of magneto-hydrodynamic flow and equivalent circuit models to find the dependency of the coupling efficiency on the RF frequency and the confinement tube's radius. Computations are also carried out for the inductively coupled RF plasma torch to make a comparison between the calculated results. Numerical results reveal that the electrical coupling efficiencies of the RF and the DC-RF hybrid plasma torches have a similar dependency on the RF frequency with an almost constant difference of slightly higher efficiencies for the hybrid plasma due to the radially expanded DC-RF hybrid plasma toward the confinement tube's wall compared with the RF plasma. However, the reduction for a confinement tube's radius less than some critical value, for instance 22 mm in this numerical work, is found to possibly cause the coupling efficiency of the hybrid plasma to drastically deteriorate compared with that of the RF plasma. Such poor efficiency of a hybrid torch with a relatively small radius is attributed to a significant diminution of the high-temperature region upstream between the DC torch's exit and the first induction coil segment. As a result of this reduced high-temperature region, the magnetic flux linkage is decreased for a smaller confinement tube, which leads to a drastic decrease in the electrical coupling. The present numerical analyses indicate that a special focus needs to be brought the influences of the DC arc jet on the electrical and the flow characteristics of a DC-RF hybrid plasma in determining the torch dimensions for effective conversion of the RF power into the plasma.
Original language | English |
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Pages (from-to) | 94-104 |
Number of pages | 11 |
Journal | Journal of the Korean Physical Society |
Volume | 54 |
Issue number | 1 |
DOIs | |
State | Published - Jan 2009 |
Keywords
- Confinement tube
- Coupling efficiency
- DC-RF hybrid plasma
- Equivalent circuit
- MHD flow
- Numerical analysis
- RF frequency