Influence of Al, Fe or Cu vapour on thermophysical properties of CO2 plasmas

摘要

CO2 has been adopted by gas circuit breakers serving as an arc extinguishing gas and by arc welding as a shielding gas. These applications are usually accomplished by the erosion of metal constituting the device, which may modify arc properties. Therefore, this paper investigates the impact of metals (Al, Fe, Cu) on equilibrium compositions, thermodynamic (mass density, specific enthalpy and specific heat) and transport properties (thermal conductivity, viscosity and electrical conductivity) for CO2 thermal plasmas, which are obtained using the Chapman-Enskog theory and the Gibbs free energy minimization method. Mass proportion is adopted for all mixtures. The presence of metals, particularly Al, can greatly enhance the electrical conductivity for CO2, especially at low temperature even for a small concentration like 1%. Fe and Cu reveal quite close evolutions of electrical conductivity and present similar effects on electrical conductivity of CO2 under the same mixing ratio. However, for viscosity and thermal conductivity of CO2, the attenuating effects of metals, particularly Fe and Cu, are quite marginal with a concentration of 10%.