Measurements of the Plasma and Condensed Particles Parameters in a DC Plasma Jet

In this paper we present the experimental set up used to measure the temperature and velocity distribution in a dc plasma jet (N2-H2 or Ar-H2), and that of alumina particles injected in these jets. Our purpose being to study the complex problem of heat and mass transfer between a dc plasma jet at atmospheric pressure and alumina particles, we have assumed for the plasma measurement that the plasma is in thermodynamic equilibrium and not perturbed by the particle injection and also that there is no particle-particle interaction. The plasma jet temperature (T) measurements are made using the atomic emission spectra for T > 7000 K, the molecular emission spectra for T > 4000 K and the melting point of various materials for T < 4000 K. The particle velocity (υ) is measured for υ < 300 m/s by laser Doppler anemometry with interferential arrangment, and, for υ > 300 m/s, by a two laser beam method. For the plasma jet velocity map, this last technique is used with small particles (3 μm) as tracers. The particle surface temperature is measured by in-flight radiation pyrometry. The first results obtained, the precision and the limitations of the methods are presented.