The article presents the calculation of thermophysical properties of the mixture water steam-argon which has been used to further enhance the characteristics of plasma torches stabilized by the water wortex. The calculations were performed at the temperatures 400-50,000 K and at 0.1 MPa. First, the composition and thermodynamic properties are determined by classical methods. Further the calculations of viscosity, electrical conductivity and thermal conductivity of the mixture are computed in the 4th approximation of the Chapman-Enskog method. The computation of collision integrals is described with special respect to the interactions of charged particles where the necessary calculations for the Coulomb potential screened at the Debye length were enlarged to cover the 4th approximation. Then the formulae describing the method based on the variational principle of solving the system of Boltzmann integrodifferential equations are shortly introduced and the transport coefficients are presented.
The electrical conductivity of SF6-Cu and Ar-Cu plasmas has been calculated by using new values of the cross section of the electron-copper momentum transfer. The comparison between the new values of the electrical conductivity and the previous ones, in the temperature range 2500-15000 K, shows the actual influence of copper vapour on this transport coefficient and allows quantification of the errors made with the various approximations.
This paper presents a numerical investigation of characteristics and processes in the worldwide unique type of thermal plasma generator with combined stabilization of arc by argon flow and water vortex, the so-called hybrid-stabilized arc. The arc has been used for spraying of ceramic or metallic particles and for pyrolysis of biomass. The net emission coefficients as well as the partial characteristics methods for radiation losses from the argon–water arc are employed. Calculations for 300–600 A with 22.5–40 standard litres per minute (slm) of argon reveal transition from a transonic plasma flow for 400 A to a supersonic one for 600 A with a maximum Mach number of 1.6 near the exit nozzle of the plasma torch. A comparison with available experimental data near the exit nozzle shows very good agreement for the radial temperature profiles. Radial velocity profiles calculated 2 mm downstream of the nozzle exit show good agreement with the profiles determined from the combination of calculation and experiment (the so-called integrated approach). A recent evaluation of the Mach number from the experimental data for 500 and 600 A confirmed the existence of the supersonic flow regime.
The electrical conductivity of quasi-thermal SF6 plasmas is calculated as a function of the electric field by considering nonequilibrium effects on the electron distribution function and on the plasma composition. Generally, the presence of the electric field increases the electrical conductivity. These results are then used in a SF6 circuit breaker modelling during the plasma decay. Taking into account the modifications of the electrical conductivity due to the electric field modifies the post-arc current and decreases the calculated interruption capability.
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