Effect of ambient pressure on the extinction limit for opposed flame spread over an electrical wire in microgravity

Experimental study on downward/opposed flame spread and extinction over electric wires in partial gravity environments

“…Videos for the flame spread over Cu#3 and NiCr#3 at 0G, 0.16G, 0.38G, and 1G are provided as supplemental materials. As observed in previous studies [10][11][12], the flame along the wire formed a nearly spherical shape in microgravity, but its downstream edge was open due to the oxygen shadow caused by the upstream oxygen consumption in the flame and quenching of the downstream flame on the metallic core [13]. Furthermore, the molten LPDE was accumulated in the burning zone and formed an ellipsoidal shape in microgravity due to the surface tension of the molten LDPE.…”

On the effects of opposed flow conditions on non-buoyant flames spreading over polyethylene-coated wires – Part II: Soot oxidation quenching and smoke release

“…Further detailing of the mechanism driving the smoke point transition for each flow parameter variation is thus required. In the following, experimental investigations conducted in parabolic flights document the smoke point transition with respect to oxidizer flow rate, oxygen content, and pressure variations.These flow conditions are known to influence other features of combustion.Using the same wire samples in the same configuration, oxygen content as a function of pressure at the flammability limit has been reported by Masashi et al at a flow velocity of 100 mm.s −1[31]. Along this curve, pressure decreases from P = 150 kPa at x O 2 ,∞ = 0.15 to P = 50 kPa at x O 2 ,∞ = 0.17.The flammability limit is thus less sensitive to pressure than the smoke point transition at the same flow velocity.…”

“…From a fire safety perspective, this approach would have to be weighed against the impacts on flammability limit, ignitability, and flame spread rate. Experimental data on the flammability limit over the same configuration suggest that low pressure and low oxygen content also increase fire safety [31], as illustrated in Fig. 2.…”

Effects of flame retardants on extinction limits, spread rate, and smoke release in opposed-flow flame spread over thin cylindrical polyethylene samples in microgravity

“…During the observation period, if combustion is not self-sustained, the flame gets smaller and less luminous until it eventually quenches at its leading edge, then releasing a significant amount of unburnt pyrolysis gases and possibly soot particles which are visible through backlight attenuation. Such a situation is regarded as extinction [26]. The infrared camera provides additional clues regarding the surface temperature evolution.…”