Experimental investigation of flame spread interaction and heat transfer over inclined parallel twin wires under different separation distances

This paper experimentally studies the effects of separation distance (0–52 mm) and inclination angle (0°–90°) on the flame spread interaction and heat transfer over inclined parallel twin electrical wires. The flame shape, flame height, flame length and flame spread rate are comparatively analyzed. The dual flame interaction behaviors over inclined parallel twin wires with increased separation distance can be divided into four typical regimes, where the heat feedback to the wire would change significantly. The flame length, flame height and flame spread rate first increase, reach maximum values, and then decrease until the corresponding values decrease to those of a single wire as the separation distance increases. The theoretical heat transfer analysis reveals the existence of competing mechanism for the heat conduction from the wire core and the heat feedback from the flame in the spreading of twin wire at different spacing and inclinations. The flame heat feedback become much more sensitive to separation distance in vertical flame spread compared to the low inclination cases. Utilizing the modified model considering the effects of dual flame interaction and inclination, the predicted flame spread rate over parallel twin wires is calculated, which shows a good agreement with the experimental measurements.