Investigation Of Typical Building Facade Insulation Material Fire Suppression Mechanism Using Water Spray

Energy is one of the important factors for social sustainable development. Our country has been a major energy consumer and ranked second in the word. So energy conservation is imperative to ensure the sustainable development of economy and society. Organic thermal insulation materials have been one of the important building energy efficiency measures. Non-retardant organic thermal insulation materials have a high fire risk and easy to be ignited. Water spray is one of the most effective technical means for fire suppression. It is significant to explore the extinguishing mechanism of thermal insulation material and important to establish an optimized, efficient water spray system.In this paper, experimental and theoretical studies are involved. Typical thermosetting insulation material named as RPU (rigid polyurethane) material was selected in the following experiments. Fire spread characteristics of vertical rigid polyurethane material were studied with various ignition positions, and the effects of pyrolysis forward slope on fire spread were deeply analyzed. A serious of vertical rigid polyurethane material fire suppression experiments were conducted. Rigid polyurethane fire suppressions affected by water spray flux, pressure, spray angle and external radiant were carefully investigated.Vertical rigid polyurethane material fire spread experiments were held with various ignition positions. When the ignition position was at the top of the sample material, lateral flame spread rate was around 0.27 cm/s at the first stage, which was larger than that at the second stage. Lateral flame spread rate at the second stage decreased when the pyrolysis forward slope increased. However, downward flame spread rate increased with the pyrolysis forward slope. In addition, theoretical model was established. And we found Vf,v～1/cosα for downward flame spread rate and Vf,h～1/sinα for lateral flame spread rate. The experimental values were consistent with theoretical values. When the ignition position was at the bottom of the sample material, both flame and pyrolysis forward height exponents were obtained from the corresponding fitting curves. The exponents in down-linear ignition case were higher than that in down-middle and down-right case. In contrast, the case of ignition position at the bottom was highest.A number of experiments were developed to study the effects of water spray flux, pressure and spray angle on RPU fire suppression without external radiation using water spray.As can be seen from the impact of water spray flux on RPU fire suppression, extinguishing effect was not obvious when water spray flux was higher than 0.1365 gm-2s-1 in that water spray entrained in strong winds. The winds weakened once the water spray flux was lower than 0.1365 gm-2s-1. Optimal water spray flux was 0.04583 gm-2s-1 for RPU fire suppression under the experimental conditions.As for the impact of water spray pressure on RPU fire suppression, it can be seen that averaged flame height, peak CO and HCN concentration were decreased rapidly once spray was applied. The peak CO concentration produced by RPU was bigger than that produced by flexible polyurethane regardless of pressure. The averaged flame height increased and had a shorter duration when spray pressure increased. Simultaneously, perspective coefficient F-became smaller, Fji became lager and extinguishing time became shorter. However, both extinguishing time and perspective coefficient had little changes when the spray pressure was higher than 0.3MPa. Namely, 0.3MPa could be considered as the optimal pressure in this experiment. Moreover, the residence time of water droplet is shorter than the sum of heat-up and complete evaporation time, the droplet diameter may not be reduced through vaporization. And flame cooling could be ignored, and surface cooling could be significant.Afterwards, the experiments of water spray angle and pressure effects on RPU fire suppression were conducted. The maximum CO concentration decreased rapidly after applying water spray, and dropped faster with 30-degree spray angle than that with 0-degree spray. In addition, extinguishing time, concentration values M measured by optical smoke density meter, Y measured by ion smoke concentration meter with 0-degree spray angle were higher than that with 30-degree spray angle. In general, extinguishing effects with spray angle of 30 degrees were better than that with 0-degree spray angle.A series of experiments were conducted to study the effects of water spray flux, external radiation on RPU fire suppression using water spray. RPU burning rate was a linear function of external radiation flux. The droplets arriving at the sample surface were between the complete evaporation and non-evaporation case. And critical burning rate of RPU was modelled with various water spray flux. At the same time, water spray control effect R1, effectiveness R2 and water mass consumed per unit combustible mass R3 were analyzed with different external radiation fluxes, water spray application fluxes and sample burning rates. The paper analyzed the three ratios with three cases-the same external radiation fluxes and different water application rates, different external radiation fluxes and the same water application rates, and different external radiation fluxes and different water application rates. The results showed that curves of the three ratios were not changed when the water spray application rate was added to the dimensionless under the case of different external radiation fluxes and the same water application rates. That meant the influence of external radiation was stronger than that of water application flux.