EFFECT OF A COOL CENTRAL GAS FEED ON TEMPERATURES AND VELOCITIES IN AN INDUCTION PLASMA TORCH.

Studies of the effect of a cool central argon feed on temperatures and velocities along or near the axis of a 5 kw induction plasma are described. Measurements were made by enthalpy probes, water-cooled impact and static pressure probes and cine-photography. Theoretical computations of temperatures in the 98. 3 mol% argon/1. 7 mol% hydrogen plasma in the absence of central feed were made for comparison. Temperatures and velocities along or near the axis reached peak values within or slightly beyond the coil region. Peak axis temperatures were below those predicted in the absence of central feed, and decreased with increasing central feed rate and decreasing feed tube diameter. Heating by thermal conduction and partial confinement by the surrounding plasma probably account for the observed initial steep rises in the temperature and velocity of the central stream. Further downstream the central stream behaves in some ways like a turbulent jet.