Abstract: Abstract: To investigate the heat conduction effect of the metal core on horizontal wire flame spread, this paper established the predicted model for the horizontal wire flame spread rate, and then performed the wire flame spread experiments for different thermal conductivity. In terms of the flame contour, mass loss rate(MLR) and flame spread rate, the effect of the metal core diameters and the thermal conductivity for different metal core on the wire fire were examined. With the metal core diameter increasing, the MLR firstly increases to a higher value and then decreases. Due to the higher thermal conductivity for the copper wire, a large amount of heat conduction was accumulated in the preheated area, and the MLR is higher than these of the stainless steel wire. The bigger MLR of 0.007 1 g/s is obtained for the copper inner diameter of 3.5 mm while the bigger MLR is 0.006 8 g/s for the stainless steel inner diameter of 4.5 mm. Also, compared to the stainless steel wire, the mass loss rate and the flame spread rate for the copper wire attained the bigger value. For the smaller mental core diameter, the heat conduction of the mental core from the pyrolysis area to the preheated area is relatively larger with the insulating sheath diameter increasing, and thus the flame spread velocity gradually decreases. For the mental core diameter bigger than 3.5 mm, only the insulating sheath below the metal core gets involved in the combustion and thus the larger mass loss rate is obtained, further causing a bigger flame spread rate. With the mental core diameter further increasing, the effect of heat sink for the mental core is strengthened, making the flame spread rate decrease again. Moreover, when the flame fully cover the wire, the measured flame spread velocity form the experiment is in a good agreement with the predicted velocity from the model, further verifying the adaptability of the predicted model.

Key words: wire fire, the heat conduction effect, horizontal wire fire spread, flame spread rate