A plasma torch (also known as a plasma arc, plasma gun, plasma cutter, or plasmatron) is a device for generating a directed flow of plasma.
The plasma jet can be used for applications including plasma cutting, plasma arc welding, plasma spraying, and plasma gasification for waste disposal.
A benefit of transferred DC torches is that the plasma arc is formed outside the water-cooled body, preventing heat loss—as is the case with non-transferred torches, where their electrical-to-thermal efficiency can be as low as 50%, but the hot water can itself be utilized. Furthermore, transferred DC torches can be used in a twin-torch setup, where one torch is cathodic and the other anodic, which has the earlier benefit of a regular transferred single-torch system, but allows their use with non-conductive materials, as there is no need for it to form the other electrode. However, these types of setups are rare as most common non-conductive materials do not require the precise cutting ability of a plasma torch. In addition, the discharge generated by this particular plasma source configuration is characterized by a complex shape and fluid dynamics that requires a 3D description in order to be predicted, making performance unsteady. The electrodes of non-transferred torches are larger, because they suffer more wear by the plasma arc.
The quality of plasma produced is a function of density (pressure), temperature and torch power (the greater the better). With regards to the efficiency of the torch itself—this can vary among manufacturers and torch technology; though for example, Leal-Quirós reports that for Westinghouse Plasma Corp. torches "a thermal efficiency of 90% is easily possible; the efficiency represents the percentage of arc power that exits the torch and enters the process".
For example, a research plasma torch at the Institute of Plasma Physics (IPP) in Prague, Czech Republic, functions with an H2O vortex (as well as a small addition of argon to ignite the arc), and produces a high temperature/velocity plasma flame. In fact, early studies of arc stabilization employed a water-vortex. Overall, the electrode materials and carrier fluids have to be specifically matched to avoid excessive electrode corrosion or oxidation (and contamination of materials to be treated), while maintaining ample power and function.
Furthermore, the flow-rate of the carrier gas can be raised to promote a larger, more projecting plasma jet, provided that the arc current is sufficiently increased; and vice versa.
The plasma flame of a real plasma torch is a few inches long at most; it is to be distinguished from fictional long-range plasma weapons.
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