Experimental study on flame propagation over horizontal electrical wires under varying pressure

Abstract

Flame propagation behavior over the polymer insulation of electrical wires can ignite adjacent combustibles and increase the scale of the fire. In this study, the flame propagation behavior over polyethylene (PE)-insulated wires was investigated theoretically and experimentally under varying pressures. The experiments were conducted in three cities with different altitudes (64, 76, and 100 kPa) and in a newly designed hypobaric chamber (7.5–101.3 kPa) for the first time. The flame morphology, structure, and spread rate were examined and discussed. The results show that pressure significantly affects flame propagation behavior. With increasing pressure, the flame illumination increases, and the flame shape changes, while the average flame height increases monotonously with decreasing average flame width. The weaker reaction rate and reduced heat transfer are the essential factors that result in a decreasing flame spread rate at lower pressures. In addition, a simplified correlation between the flame spread rate, pressure, and wire configuration in the form of Vf∝(P2L3)0.65 is proposed to predict flame propagation along an electrical wire. Moreover, the influence of the metal core on the flame behavior was observed based on the different heat transfer mechanisms in the flame front zone. All results contribute to the safe operation of electrical wires.