In Vestigations of Some Characteristics of the Plasma Jet (Report I)

Abstract

A plasma jet of low gas flow rate can be somehow generated by the usual plasma torch, but more easily by the A-type torch having a copper anode nozzle whose inner surface is smoothly and convergently curved.
But this torch has some shortcomings. To eliminate these shortcomings the authors have devised the B-type torch having a gas guide nozzle which is electrically insulated from the cathode and the anode, and installed between them. This gas guide nozzle can constrict the arc and direct it along the torch axis.
Generating the plasma jet whose arc current and argon flow rate were respectively 270 Amp and 3-12 1/min, some characteristics were investigated of the two types of torches to compare them. The distance between the cathode and the nozzle exit was changed in the range of 11-20 mm.
Results obtained of the experiments are as follows:
(1) The arc voltage is more stable for the B-type torch than for the A-type torch.
(2) The regulation of the arc voltage is easier for the B-type torch than for the A-type torch.
(3) The output power of the B-type torch can be larger than that of the A-type torch at a certain constant arc current and gas flow rate.
(4) When the plasma jet is laminar, its flame is longer with the B-type torch than with the A-type torch.