Experimental Researches on the Properties of Plasma Jet in the Magnetic Field at a Low Pressure Atmoshere (Report I)

Abstract

In the welding technology, it may be interesting to examine the magnetic control of a plasma jet flame. In this report is described the experimental result on the fundamental properties of plasma jet flame in a magnetic field.
The distribution of field strength in the cusp type or mirror type magnetic field, each of them were made by two coils M_l and M₂, was measured as a preliminary research. The plasma jet was injected to the low pressure vessel along the axis of magnetic field, as shown in Fig. 1.
Photographic observations show that the plasma jet flame flows in the direction of magnetic line of force. Radial distribution of total pressure of the plasma jet flame was measured with use of a pitot tube on the mid-plane between coil Mt and coil M₂. In general, the total pressure of plasma jet in the mirror type magnetic field was higher than that in cusp type field. Higher values were observed at relatively constricted region near the central axis of plasma jet.
Total pressure rises as the are current incrases, but is almost invariant with the arc voltage in this experiment.
The thermal efficiency of the plasma jet torch was also investigated. The amount of energy contained in plasma flame is expressed as ηVI, η being thermal efficiency of torch.
It has been found that the total pressure varies with the amount of plasma energy ηVI.