A new look at the thermal and gas dynamic characteristics of a plasma jet

Author： Pfender E. Spores R. Chen W.L.T.

ISSN： 0268-1900

Source： International Journal of Materials and Product Technology, Vol.10, Iss.3-6, 1995-11, pp. : 548-565

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Abstract

There is increasing evidence that reproducibility of the plasma spray process depends to a large degree on the reproducibility of the plasma jet which is utilised for spraying. Recent research using a broad range of diagnostic techniques, including, LDA, electric and acoustic probing, spectroscopy, and enthalpy probes, has greatly enhanced our present understanding of the thermal and fluid dynamic characteristics of plasma jets. Experimental results strongly imply that the entrainment mechanism in turbulent plasma jets is more of an engulfment type process as opposed to simple diffusion. Turbulence measurements indicate that the velocity fluctuations are non-isotropic, contrary to what has been assumed in most numerical work. Measurements of electric, acoustic, and light fluctuations demonstrate that there are correlations between some of these fluctuations and that turbulence in the plasma jet may be strongly affected by fluctuations in the torch nozzle. Temperature measurements using spectrometric and enthalpy probes indicate strong discrepancies, particularly in the jet fringes.