微小重力環境におけるポリエチレン被覆導線の燃焼現象に及ぼす心線材質の影響

抄録

Combustion of wire insulation is important for fire safety in Space. Insulated wire has two unique features, one is sample geometry and another is existence of wire core. In this paper we investigate the effect of core materials on combustion phenomena of insulated wires. An experimental study of flame spread phenomena over polyethylene insulated wires with two different core materials, copper and nichrom, in different O₂ concentrations was performed in microgravity. The experiments were performed at the Japan Microgravity Center (JAMIC) 10 s dropshaft. Experiments were performed with different O₂ concentration and core material. The results show that the core material strongly affects the flame shape irrespective of gravity level. The flame spread rate is also strongly affected by the core material. Under normal gravity, the flame spread rate with copper cores is faster than that with nichrom cores in any of the tested oxygen concentrations. In microgravity, the effect of the core materials on the flame spread rate changes by oxygen concentration. In 35% O₂, flame spread rate with copper wire was faster than that with nichrom core wire, as also seen in the normal gravity case. In 21% O₂, the flame spread rate with the nichrom core wire is faster than that with copper core wire. The core heat conduction analysis shows that the thermal conductivity of the core material has an important effect on the flame spread rate. The case of high flame temperatures, the core acts as a heat source and high conductivity material supplies more heat to the insulation. At low temperatures, the core becomes heat sink and high conductivity material causes heat removal from the insulation near the flame front.