Opposed-wind Effect on Flame Spread of Electric Wire in Sub-atmospheric Pressure

Abstract

Opposed flame spread of electric wire in sub-atmospheric pressure is studied experimentally. Thin-polyethylene (PE) coated nickel-chrome (NiCr) and iron (Fe) wire are used as test samples in this study. Total pressure is reduced from atmospheric (100 kPa) to sub-atmospheric (40 kPa) and range of employed external forced-flow speed is from 0 cm/s to 40 cm/s. Results show that the spread rate monotonically decreases, or stays nearly constant, as the forced-flow speed increases regardless of the material of the wire. Dependence of the spread rate on the opposed-flow speed appears differently depending on the material of the wire; with high-conductive material (Fe), decrement trend of the spread rate with wind is suppressed. Importantly, under the conditions considered in this study, the spread rate tends to increase as the pressure decreases regardless of the pressure and the material of the wire. Dependence of the spread rate on pressure is more pronounced with less-conductive (NiCr) wire, whereas less-pronounced with high-conductive (Fe) wire. Qualitative discussions are made to explain the observed spread trend and the importance of the presence of wire to characterize the flame spread of the wire is addressed.