High-temperature properties of dry air used as arc quenching medium and its mixture with vaporized C2F4 : reaction products and critical reduced electric field strength at 300–3000 K

Recently, electric power equipment manufacturers released a joint statement with the aim of developing high-voltage electrical equipment completely free of fluorinated gases such as fluoroketones and fluoronitriles, which are considered as alternatives to <?CDATA SF₆?> S F 6 and artificially produced compounds of F. This paper considers air as a typical gas present naturally in the environment to investigate its high-temperature properties, including an air mixture with <?CDATA C₂F₄?> C 2 F 4 vapor injected from a polytetrafluoroethylene nozzle, for application as an arc-quenching medium in a high-voltage circuit breaker equipped with a nozzle. Chemical composition results for the reaction products at 300–3000 K show that the admixture of <?CDATA C₂F₄?> C 2 F 4 vapor causes a decrease in the molar number of <?CDATA O₂?> O 2 contained in the air, owing to the production of O-containing compounds such as <?CDATA CO₂?> C O 2 and <?CDATA CO?> C O . Additionally, the results reveal that the admixture of <?CDATA C₂F₄?> C 2 F 4 vapor lead to the production of <?CDATA CF₄?> C F 4 as the predominant F-containing compound. Furthermore, the boundary condition for <?CDATA O₂?> O 2 production in terms of <?CDATA O₂?> O 2 molar number <?CDATA X_O₂?> X O 2 and <?CDATA C₂F₄?> C 2 F 4 molar number <?CDATA X_C₂F₄?> X C 2 F 4 is formulated. Such evaluation of the mixture composition enables the determination of a reduced effective collision ionization coefficient <?CDATA ᾱ/N?> α ˉ / N and a critical reduced electric field strength <?CDATA Ecr/N?> E c r / N , resulting in <?CDATA ᾱ/N?> α ˉ / N = 0. The strength <?CDATA Ecr/N?> E c r / N for the mixture with 30%–100% <?CDATA C₂F₄?> C 2 F 4 molar fraction rises to approximately 150 Td (1 Td = 1 <?CDATA ×\,10⁻²¹?> × 10 − 21 V m 2 ) over 300–3000 K, which is 20–50 Td higher than that for high-temperature air unmixed with <?CDATA C₂F₄?> C 2 F 4 vapor. The variation in <?CDATA Ecr/N?> E c r / N is discussed in terms of predominant electron impact processes and the electron energy distribution function in the mixture.