| The "energy-saving and emission-reduction policy" from the government has greatly prompted the application of a variety of organic external insulation materials in buildings. At present, the commonly used organic external insulation materials in the construction market are expanded polystyrene foam (EPS), extruded polystyrene foam (XPS) and rigid polyurethane foam (RPU). They have the advantages of good thermal insulation property, light weight, easy construction and low price, etc. However, organic polymer materials are flammable. In the case of a fire, polymer materials without flame-retardant treatment or with unqualified flame-retardant treatment will burn quickly and undergo a rapid flame spread rate while producing large amounts of toxic smoke. Related fire accidents occurred occasionally in recent years, which posed a serious threat to people’s life and properties and caused a negative social influence.The external wall fire includes two fire scenarios. One is "outflowing fire" which is caused by a fire occurring inside the building, and the other is "adjacent fire" which is initiated by an external fire close to the building envelope. There are lots of research work about the fire performance of EPS, XPS and RPU. However, none of them focus on the fire behavior of these organic foam materials such as melting, charring, ignition and combustion etc., under the conditions of outflowing fire and adjacent fire. Therefore, we designed and built the fire behavior test rig of external insulation materials considering the two scenarios of external wall fires. Based on the test rig, the thermal effect of outflowing fire and adjacent fire on the exterior wall was studied, and the fire behaviors of typical external insulation materials were investigated.For the case of outflowing fires, a number of experiments were conducted to characterize the thermal exposure imposed onto the exterior wall by external flame ejected from the wall openings. Opening geometries with a large range of aspect ratios were specially taken into consideration. Data from the experiments were analyzed and the heat flux was related to relevant influencing factors such as the heat release rate and flame height of the external flame and the aspect ratio of the wall opening. For the case of adjacent fires, the influence of fuel tray’s size, shape and distance to the exterior wall on the heat flux distribution were investigated, and the correlation between heat fluxes and the heat release rate, flame height was established.The fire behaviors of RPU, EPS and XPS under the impinging of outflowing fires and adjacent fires were studied on the fire behavior test rig. The major fire hazard of none-flame-retardant RPU comes from its high flammability and surface flame spread rate. For this reason, the flame spread rate of RPU was investigated by experimental and theoretical analysis. The significant factors that affect the flame spread rate were determined and the influencing mechanism was analyzed. A numerical model was further established to describe the fast flame spread behavior of RPU. The heat flux correlations of outflowing fires and adjacent fires were coupled into this numerical model, and the flame heights and pyrolysis fronts of the none-flame-retardant and flame-retardant RPU were predicted. The predictions showed good agreement with the experimental results. For the polystyrene foam materials, the major fire behavior includes melting, shrinking, decomposition, ignition and combustion. The experimental results of cone calorimeter and thermal gravimetric analysis showed that the decomposition and combustion of polystyrene foam underwent a single process. In the experiments of fire behavior of polystyrene foams under outflowing fires and adjacent fires, it was observed that the melting, ignition and formation of pool fires were greatly affected by foam density and attachment effect of external flames. This dissertation carried out a detailed analysis on this phenomenon. |
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