Flame Spread over Wire Insulation under Microgravity

Abstract

An experimental study of flame spread phenomena over ETFE (Ethylene-Tetrafluoroethylene) insulated wire was performed under microgravity to obtain fundamental data on fire safety in space. The effects of the parameters thought dominant for wire combustion in fires-the ambient oxygen concentration, wire initial temperature, T_i, and wire diameter, d_ω, - were investigated in the microgravity experiments. A series of comparative experiments were also conducted at normal gravity. Flame shape under microgravity changed depending on the state of the molten fuel accumulation. Experimental results showed that there existed a possibility of higher flame spread rates under microgravity than at normal gravity, in spite of lower flame temperature in microgravity. Wire initial temperature, T_i, had a very large influence both on flame spread rates and extinction limit of the wire under microgravity. The degree of flame spread rate decreased with increase in d_ω and, correspondingly, the increase with decrease in d_ω under microgravity was higher than at normal gravity.