Research Of The Effect Of Space Conditions On Smoldering Propagation Of Polyurethane Foam

Smoldering is the flameless, low-temperature combustion with low spread velocity,whose self-sustained propagation mainly relies on the heat released by the heterogeneous oxidation at the surface of the solid fuel. In this paper, a series of experiments were conducted to study smoldering combustion of the polyurethane foam,a most common porous material. Influence of smoke exhausted conditions, heating distance and material spatial structure on the smoldering propagation process has been analyzed by series of experiments under different conditions.In order to investigate the mechanism of forward smoldering and reverse smoldering of polyurethane foam under different smoke exhausted conditions, lots of experiments have been conducted with vertically-oriented polyurethane foam under natural convection condition. The results showed the smolder propagation could still sustain itself at a low spread velocity without a transition to flame when the exhaust port was fully closed. With area increment of the exhaust port, the smoldering propagation rate and the average heating rate of char burning were gradually increasing, and then the transition from smoldering to flaming happened finally.For the purpose of studying the characteristics of self-sustaining propagation smoldering, experiments were conducted with five different kinds of heating distance.The results indicated that the quantity of heat received from the heater reduced with the increasing of heating distance. Only when the exothermic oxidation of materials occurred and the temperature rose rapidly, could the smoldering propagate self-sustainably. Correspondingly, the heating rate curve showed a rapid rise, when smoldering could maintain propagation, while it showed no rise when smoldering could not maintain propagation.Under the smoldering temperature condition, the void increasement by changing the structure of the materials would accelerate the smoldering combustion. Adding either tobacco or scraps of paper to the polyurethane foam would accelerate the transition from smoldering to flaming and increase the risk of fire accident.Based on the research of smoldering, the general rules of the smoldering fire can be obtained, which can help to prevent the smoldering fire by providing the effectivemethod of management. The research can also provide scientific basis and guidance for safety management.