Velocity Measurements for Arc Jets Produced by a DC Plasma Spray Torch

An optical method was used to determine the axial velocity of plasma jets produced by a DC plasma spray torch. Different experimental conditions were tested in order to systematically study the influence of the working parameters on the plasma velocity. In this way, the arc current ranged between 200 and 600 A, the gas flow rate between 30 and 80 slm, and the internal nozzle diameter between 6 and 10 mm; the plasma gases were either an Ar–H₂mixture or N₂. Rather well defined tendencies were observed and at the same time it appeared that the arc stability greatly influenced the fluctuations of the velocity.