DIFFUSION PHENOMENA OF A COLD GAS IN A THERMAL PLASMA STREAM

The present study involves both experimental investigation and mathema tical modeling of the diffusion process of a cold gas injected into a main plasma stream. The cold gas (nitrogen or helium) was injected axi ally through a water cooled tube located along the centerline of an in duction plasma torch. The 2-D distribution of the temperature, velocit y and concentration profiles in the plasma flow were measured using en thalpy probe techniques, The results are compared with the predictions of a 2-D, LTE, turbulent mathematical model. The effects of the natur e (composition) of the injected gas and its mass flow rate are investi gated. The enthalpy probe measurements and the predictions of the mode l are in good agreement. The effective (turbulent and molecular) trans port properties are estimated from a comparison of the measured and ca lculated profiles of the temperature, velocity and concentration field s. This study sheds light on the basic diffusion mechanisms involved i n a widely used configuration of induction plasma reactors, i.e. in wh ich the material to be treated is injected axially into the plasma, th rough a central water cooled tube.