Theoretical and Experimental Investigation of Pressure and Flow in Induction Plasmas

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Abstract
An investigation of flow in and around an induction plasma is made as a continuation of an earlier theoretical study of magnetic pressure in an induction plasma. The existence of the predicted flow out from both ends of the plasma is confirmed by flow visualization and stagnation pressure measurements in and around an ambient-pressure vortex-free argon plasma in a 28-mm tube. Flow visualization and gas velocities are obtained by photographing injected solid particles. For a 3-kW argon discharge, the velocity at the upstream end of the plasma was 6±0.3 m/sec, and velocity varies linearly with discharge power over the range investigated (up to 4.7 kW). A model of the plasma is devised to enable the maximum velocity of magnetically pumped flow to be calculated from the static magnetic pressure. Pressures in the range of +0.04 in. water, caused by expansion thrust of hot gases from the torch, were measured behind the plasma. The thrust pressure is calculated and is in reasonable agreement with measurements. A consequence of both magnetic and thrust pressures is that material introduced at the back of the torch tends to bypass the plasma.