Experimental Study On The Impact Of Physics Condition To The Translation From Smoldering To Flaming Combustion Of Polyurethane Foam

Smoldering material will release a mass of noxious gas, and it's easy to translate to flaming combustion, which will arise fire accident. The existing studying on smoldering and its translation to flaming combustion usually ignored the impact of physics condition to material smoldering. In this text, by changing physics conditions, such as the size and density of material, heat exchange condition, continuity and moisture content of material, the characteristic law of Polyurethane foam translating from smoldering to flaming combustion was studied.By measuring diffusion coefficient of oxygen and temperature of smoldering area, a series of chemical changes of polyurethane foam with different size were analyzed. Study indicates that the smoldering will translate to flaming combustion so long as the sizes of polyurethane foam reach to criticality.Study on two kinds of different density polyurethane foam and analysis gaseous product with gas chromatograph. Combined with thermal analysis, it discusses the influence of material density to smoldering and transition from smoldering to flaming combustion. The results show that polyurethane foam which has the big density produces more calories in natural and produce high concentrations of CO, and provide plenty of flammable gas. So, it's easier to promote the transition form smoldering to flaming combustion.In the condition of changing heat exchange, the dynamic varying law was analyzed theoretically and quantificational analysis indicate that, the change of physical parameters and heat exchange of external environment cause smoldering and external heat transfer at the dynamic unbalance state, which easy to take shape a high-temperature region, and produce flammable gases; at the same time, outer air providing sufficient oxygen, which will cause the transition from smoldering to flaming.The variation of fuel included continuous samples with part of dryness and part of wetness, and discrete samples with part of dryness and part of wetness. The phenomena of different experiments were observed. And the temperature histories during smoldering were recorded by thermocouples. Combined with thermal analysis, the oxidation and prolific reaction mechanism of smoldering material in different temperature stages was studied. The result demonstrates that gaseous phase reaction is easier to take place and translate to flaming combustion on continuous material than discontinuous material. When the discontinuous spacing of material increases, smoldering will not easy to transmit, even it will crush out immediately. As the moisture content larger than 20.9%, the propagation of smoldering slowed down and extinguished. When the moisture content of latter discrete part reached 17.4%, the smoldering extinguished.The research findings in this text will provide theoretical basis for exactly understanding smoldering fire, knowing the law and characteristic of smoldering well and decreasing fire accident.