thermal

The radiative heat transfer in arc plasma models is considered from the point of view of its description in terms of a net emission coefficient, the method of spherical harmonics in its lowest order, and the discrete ordinate method. Net emission coefficients are computed, applying approximate analytical and numerical approaches and a multi-band representation of the spectral absorption coefficient with three kinds of its averaging and two datasets.

The dataset contains results of a unified one-dimensional model of an arc plasma in air, between copper electrodes, that includes the change of the gap distance. The occurance of multiple reversals of the electric field and the anode voltage drop is observed. The evolution of the spatial distribution of the electron and heavy particle temperatures with the gap distance and the opening speed is also studied. The model quantitatively predicts a number of plasma properties under conditions that are relevant to the contact separation in low-voltage switching devices.

Double-pulse laser induced breakdown spectroscopy (LIBS) measurements in water with up to 600 bar hydrostatic pressure and 150 mJ energy of each pulse were done to select a setup which promote separated spectral lines in the observed plasma emission even at elevated pressures, where line broadening until loss of the most spectral information can occur. For this a compact spectrometer und a Czerny-Turner spectrometer, both fiber-based, has been applied to investigate the dependence of the emitted radiation on different parameters and hydrostatic pressure.

Double-pulse laser induced breakdown spectroscopy (LIBS) measurements in water with up to 600 bar and 400 mJ each pulse were done to select laser parameters which promote optimized spectral line emission from plasma even at elevated pressures, where line broadening until loss of the most spectral information can occur. Optical emission spectroscopy, using a Czerny-Turner spectrometer, has been applied to investigate the dependence of the emitted radiation on laser parameters and hydrostatic pressure.

The lifetime of tungsten cathodes used in plasma spray torches is limited by processes leading to a loss of cathode material. It was reported in the literature that the mechanism of their erosion is the evaporation. A model of the ionization layer of a cathode is developed to study the diffusive transport of evaporated tungsten atoms and tungsten ions produced due to ionization by electron impact in a background argon plasma.

The work is concerned with the effect of a spatially fluctuating heating of Al_2O_3 particles with diameters of 5–120 μm during a plasma spray process. A plasma jet is generated in a mixture of Ar (40 NLPM) and H_2 (14 NLPM) and in pure Ar at an electric current of 600 A. The tracing of the injected particles in the plume region of the plasma jets is considered in the framework of a three-dimensional model taking into account a turbulent fluid flow.

The data set is related to a two-dimensional and stationary magneto-hydrodynamic model of a plasma spray torch operated with argon, which is developed to predict the plasma properties in a steady operating mode. The model couples a submodel of a refractory cathode and its non-equilibrium boundary layer to a submodel of the plasma in local thermodynamic equilibrium in a self-consistent manner. The Navier-Stokes equations for a laminar and compressible flow are solved in terms of low- and high-Mach number numerical approaches.

An appropriate coupling of an arc plasma column in the state of local thermodynamic equilibrium to a refractory
cathode necessarily involves the non-equilibrium boundary layer between them. A model has been developed that