| Since the beginning of the 21st century,with the rapid development of society and economy,the energy consumption has increased day by day.Among them,the energy consumption in the construction field accounts for one-third of the total energy consumption.High polymer thermal insulation materials have good thermal insulation effects,low thermal conductivity,light weight and many other advantages are widely used in building exterior wall insulation.Due to its own general flammability,once it is ignited by the outside,it will spread rapidly,and a large amount of smoke and toxic gases will be generated during the combustion process,causing danger to human life and property losses.Fire accidents caused by accidental ignition of thermal insulation materials It is more common.At present,the organic thermal insulation materials on the market mainly include polyurethane foam（PU）,extruded polystyrene（XPS）and molded polystyrene（EPS）.In addition to the danger of burning the material itself,it will also produce molten drippings,which will increase the overall fire risk.How to prevent and reduce the fire risk of building insulation materials has become a more concerned topic in the field of building fire safety.In order to effectively curb the "rampant" trend of building thermal insulation materials in the fire scene,domestic and foreign scholars have conducted a large number of research experiments on the combustion characteristics of high polymer thermal insulation materials.However,the real fire scene often occurs in the situation of multi-element coupling,and the research on the special combustion behavior of thermal insulation materials caused by the complex structural configuration of buildings is not perfect.This paper analyzes and explores the fire spread process of thermal insulation materials under the restricted configuration of the inside and outside corners of the building adjacent to the facade.Considering that this complex configuration often occurs in the real fire scene,the phenomenon of fusion of multiple fire sources may occur during the experiment.Two ignition positions were set up to analyze the interaction mechanism of the countercurrent fire spread formed by the upper fire point and the downstream fire spread formed by the lower fire point in the process of flame propagation.By comparing six typical angle configurations of adjacent inner and outer angles,the experimental group has a good effect on the average fire spread rate,mass loss rate,near-domain temperature field and radiation field,pressure difference,flame pulsation frequency and flame height during the combustion process.These typical characterization parameters are recorded,and the flame propagation behavior and laws in different scenarios are analyzed.Through experimental research,it is found that during the combustion process of the adjacent included angle configuration,the flame front on the downstream side mainly migrates horizontally,and the flame on the countercurrent side mainly migrates vertically downward.The superimposed heat transfer of the surface accelerates the tilting behavior toward the center side,and the flame front shape changes from two-dimensional combustion to an inverted V-shaped flame front.The propagation speed of the downstream flame is faster than that of the countercurrent,which leads to the disappearance of the flame front on the countercurrent side,and the combustion front is transformed into a one-dimensional linearity.expansion,the radiant heat intensity of the combustion process,the average fire spread rate,and the mass loss rate all show periodic fluctuations,but the overall trend is declining.The rate of mass loss and the rate of mass loss show a decreasing trend;when the angle θ<90° between adjacent facades is included,the rate of combustion and heat release is higher,and there is a greater fire hazard.At the same time,it was found that with the increase of the included angle,the two configurations showed different trends of pressure difference.In the negative angle configuration,due to the coupling effect of heat transfer and combustion reaction rate,it first decreased and then increased.There is a gradual decrease in the angular configuration due to a decrease in the burning rate.The probability of melting droplet effect of polyurethane thermal insulation material in the adjacent fa?ade configuration will change with the change of angle,and its law is consistent with the change law of pressure difference flue gas flow rate,which proves that the probability of droplet generation during the combustion process is mainly affected by the external airflow stress The effect is that the configuration θ<90° is more likely to produce molten dripping,which is easy to cause the fire to intensify.Studies have shown that the configuration of the internal and external corners of the building adjacent to the facade will increase the complexity and risk of fire,and the internal corner configuration has a higher fire risk.The research findings of this experiment will enrich the theoretical system of fire spread of combustible solid materials under the building facade configuration,which can be used as a reference for building fire prevention and control measures,and provide a reference for real fire rescue behavior and building facade fire protection design.Figure[43]table[8]reference[74]... |
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