Influence of O2 on Thermophysical Properties of C4F7N–CO2 Arc Plasmas

C4F7N is a potential SF6 replacement as insulating and arc quenching medium in power system. It is usually mixed with CO2 and O2 to further reduce the global warming potential (GWP) and liquefaction temperature of gas mixtures and also to prevent the condensation of graphite after the arc discharge. In this work, we perform a numerical study on thermophysical properties of C4F7N–CO2–O2 arc plasmas at different proportions of O2. We first obtain the compositions of C4F7N–CO2–O2 arc plasmas using the method of Gibbs free energy minimization. Based on the plasma compositions, we further calculate the thermodynamic properties, namely mass density, specific heat, and specific enthalpy, at temperatures ranging from 300 to 30,000 K. Also, the transport coefficients including electrical conductivity, viscosity, and thermal conductivity of C4F7N–CO2–O2 arc plasmas are calculated based on the Chapman-Enskog theory. Lastly, we investigate the influence of O2 on the compositions, thermodynamic properties, and transport coefficients of C4F7N–CO2–O2 arc plasma, which could provide basic knowledge and data for the further study of C4F7N gas as arc quenching medium.