PREDICTION OF ELECTRICAL BREAKDOWN CARBONIZATION OF GASES AND GAS MIXTURES

ABSTRACT This paper will describe theoretical and experimental work on the tendency of gases and mixtures to form free carbon on sparking or arcing. The theoretical work involves calculations from basic data of the amount of free carbon in equilibrium in gas mixtures as a function of initial composition and temperature in the range 500-5000 o K. It will be shown that the free carbon content varies widely with the initial gas composition and that ranges of mixtures of certain carbonizing gases with decarbonizing gases exist which are calculated not to contain free carbon in equilibrium at any temperature. The experimental work involves tests of the tendency of gas mixtures to carbonize on arcing. It will be shown that the experimentally observed cut-off composition for the formation of free carbon on arcing can be correlated with the theoretical cut-off mixture composition (for free carbon in equilibrium) at 1000-2000 o K. The dependence of carbonization on the amount of energy dissipated in the spark or arc and the rate of cooling will be discussed. The method is applicable to optimizing non-carbonizing low-cost high-strength gas mixtures for practical applications. This work is sponsored by the Electric Power Research Institute under Contract 847-1 with the Westinghouse Research and Development Center.