典型有机保温材料的热过程演化及火蔓延特性研究
发布时间：2018-08-28 13:35
【摘要】：建筑节能是建设低耗环保型社会和保持经济可持续发展的关键环节。有机保温材料因为其优越的隔热效果而被国内外的建筑保温系统广泛采用,其中热塑性材料和热固性材料作为日常生活中最常见的有机保温材料,应用极为广泛。然而,这些材料在受热情况下易产生裂解甚至发生燃烧,火蔓延速度极快,同时会产生大量的烟气和有毒有害气体。对于外墙保温材料的热危害性的防治已经成为大力发展节能型建筑急需解决的关键问题。不同于热固性材料的燃烧行为,热塑性保温材料燃烧过程中会产生大量的熔融滴落物质,并且在壁面火蔓延的底部积聚形成流淌油池火,加大其整体热危害性。本文选取最常见的三种热塑性材料：聚乙烯(PE),聚丙烯(PP)和聚苯乙烯(PS)作为实验研究对象,并通过自行搭建的实验平台,开展一系列实验。观察分析三种热塑性颗粒材料形成稳定熔融滴落熔液情况下,产生的油池火蔓延流淌行为,并且定量分析不同逆向滴落速率下情况下油池火的流淌速率,温度场,辐射场和质量变化等规律。本文围绕三种典型热塑性材料熔融滴落形成的油池火所进行的实验研究和理论分析表明,三种热塑性材料加热后形成的熔融物质在空中滴落过程中的质量损失占整体质量损失相当大的比例,高温熔液在空中逆向滴落过程中的热量损失同样会对周围环境形成较大热危害,增加消防扑救的难度。相同条件下,聚苯乙烯(PS)形成的高温熔融液滴由于其较大的粘性导致其逆向滴落速率低于聚丙烯(PP)和聚乙烯(PE)。由于三种热塑性材料解聚物表观粘性和材料分子结构的差异,导致聚苯乙烯(PS)形成的油池火流淌速率慢于聚丙烯(PP)和聚乙烯(PE),但聚苯乙烯(PS)形成的熔滴油池火在熔流槽内流淌蔓延过程中的燃烧速率却高于聚丙烯(PP)和聚乙烯(PE),聚苯乙烯材料较大的燃烧热及流淌粘度使得其形成的流淌火火焰前锋和油池的前锋移动保持一致。从熔融、滴落和流淌三方面特性观察热塑性材料表现出的燃烧行为差异,聚丙烯(PP)和聚乙烯(PE)形成的滴落流淌火热危害性大于聚苯乙烯(PS)。所以在实际的建筑防火设计中,对热塑性材料火灾热危害性的综合性评估是非常必要且关键的。另一方面,热固性保温材料的火蔓延行为是气相燃烧与固相热解相互耦合的复杂反应过程。本文选取典型热固性保温材料—硬质聚氨酯泡沫(RPU)和软质聚氨酯泡沫(FPU)作为研究对象,通过外加辐射源,模拟研究实际火灾场景中不同的外界辐射强度下二种保温材料的火蔓延行为,着重分析火蔓延速度、温度场、质量损失、火焰脉动频率和火焰高度等典型特征参数随试样宽度的变化规律。存在外界辐射源情况较之普通环境的逆向稳态火蔓延过程具有更强的辐射热反馈,硬质聚氨酯(RPU)和软质聚氨酯(FPU)板材的逆向火蔓延皆会发生加速蔓延现象,板材表面火蔓延随着外界辐射强度的增加,会产生大量热解气,加剧火势,质量损失速率和火蔓延速度与外界辐射强度大小呈正相关的关系。相比硬质聚氨酯(RPU)材料,软质聚氨酯(FPU)泡沫由于其自身的物理结构,表现出了更充分的燃烧性能。当外界辐射强度大于一定强度时,硬质聚氨酯材料沿厚度方向将被完全燃透。而二者的火焰高度的变化规律则是无关,主要受辐射强度控制。硬质聚氨酯和软质聚氨酯板材的火焰脉动频率与外界辐射强度和宽度耦合作用的结果。当外界辐射强度较小时,硬质聚氨酯板材的火焰高度随着板材宽度的增加而增加；反之,火焰高度的增加与板材宽度外界辐射强度和宽度呈反相关关系。由于软质聚氨酯板材燃烧过程中火焰前锋出会出现一层薄熔融层,我们借鉴油池火理论对软质聚氨酯的火焰脉动频率和火焰高度进行预测,得出的实验数据变化趋势与理论公式预测曲线表现出很好的一致性。
[Abstract]:Building energy conservation is the key link of building a low-consumption environment-friendly society and maintaining sustainable economic development.Organic thermal insulation materials are widely used in building thermal insulation systems at home and abroad because of their superior thermal insulation effect.Thermoplastic materials and thermosetting materials are the most common organic thermal insulation materials in daily life. However, these materials are liable to crack or even burn under the condition of being heated, and fire spreads very fast. At the same time, a lot of flue gas and poisonous and harmful gases are produced. Thermoplastic insulation materials produce a large number of melt dropping substances during the combustion process, and accumulate at the bottom of the spread of wall fire to form flowing oil pool fire, increasing its overall thermal hazard. A series of experiments were carried out on the experimental platform. The spreading and flowing behavior of pool fire was observed and analyzed when three kinds of thermoplastic granular materials formed stable dropping melt. The flow rate, temperature field, radiation field and mass change of pool fire under different reverse dropping rates were quantitatively analyzed. Experimental study and theoretical analysis of pool fire formed by melt dropping of typical thermoplastic materials show that the mass loss of melt formed by three thermoplastic materials in the process of air dropping accounts for a considerable proportion of the total mass loss, and the heat loss of high temperature melt in the process of air reverse dropping will also be around. Under the same conditions, the high-temperature melt droplets formed by polystyrene (PS) have a lower reverse dripping rate than polypropylene (PP) and polyethylene (PE) due to their greater viscosity. Due to the difference of the apparent viscosity and the molecular structure of the three thermoplastic materials, polyphenylethylene (PP) is produced. The flow rate of pool fire formed by polystyrene (PS) is slower than that of polypropylene (PP) and polyethylene (PE), but the combustion rate of pool fire formed by polystyrene (PS) is higher than that of polypropylene (PP) and polyethylene (PE) during the flow and spread process in the pool. The higher combustion heat and viscosity of polystyrene make the flame front and flame front formed by the pool fire. The difference of combustion behavior of thermoplastic materials was observed from three aspects of melting, dropping and flowing characteristics. The thermal hazard of dropping flow formed by polypropylene (PP) and polyethylene (PE) was greater than that of polystyrene (PS). Therefore, the thermal hazard of thermoplastic materials in fire protection design was synthesized. On the other hand, the fire spread behavior of thermosetting insulation materials is a complex reaction process coupled with gas-phase combustion and solid-phase pyrolysis. In this paper, the typical thermosetting insulation materials, rigid polyurethane foam (RPU) and soft polyurethane foam (FPU), are selected as the research objects and simulated by external radiation sources. The fire spread behavior of two kinds of insulation materials under different external radiation intensity in actual fire scene is studied. The variation of typical characteristic parameters such as fire spread velocity, temperature field, mass loss, flame fluctuation frequency and flame height with sample width is analyzed emphatically. The process has stronger radiation heat feedback. The reverse fire spread of rigid polyurethane (RPU) and flexible polyurethane (FPU) sheets will accelerate. With the increase of external radiation intensity, a large amount of pyrolysis gas will be produced, which will aggravate the fire. The mass loss rate and fire spread speed are positive with the external radiation intensity. The results show that flexible polyurethane (FPU) foams exhibit better combustibility than rigid polyurethane (RPU) foams because of their own physical structure. When the external radiation intensity is greater than a certain intensity, rigid polyurethane materials will be fully burned along the thickness direction. However, the flame height of the two foams is independent, mainly. Controlled by radiation intensity, the flame fluctuation frequency of rigid polyurethane and flexible polyurethane sheets is coupled with external radiation intensity and width. When external radiation intensity is small, the flame height of rigid polyurethane sheets increases with the increase of plate width; otherwise, the flame height increases with the increase of plate width and the external radiation is strong. The flame front appears a thin melting layer during the combustion of soft polyurethane sheet. We use the oil pool fire theory for reference to predict the flame fluctuation frequency and flame height of soft polyurethane. The experimental data show a good consistency with the theoretical prediction curve.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU551
本文编号：2209540
[Abstract]:Building energy conservation is the key link of building a low-consumption environment-friendly society and maintaining sustainable economic development.Organic thermal insulation materials are widely used in building thermal insulation systems at home and abroad because of their superior thermal insulation effect.Thermoplastic materials and thermosetting materials are the most common organic thermal insulation materials in daily life. However, these materials are liable to crack or even burn under the condition of being heated, and fire spreads very fast. At the same time, a lot of flue gas and poisonous and harmful gases are produced. Thermoplastic insulation materials produce a large number of melt dropping substances during the combustion process, and accumulate at the bottom of the spread of wall fire to form flowing oil pool fire, increasing its overall thermal hazard. A series of experiments were carried out on the experimental platform. The spreading and flowing behavior of pool fire was observed and analyzed when three kinds of thermoplastic granular materials formed stable dropping melt. The flow rate, temperature field, radiation field and mass change of pool fire under different reverse dropping rates were quantitatively analyzed. Experimental study and theoretical analysis of pool fire formed by melt dropping of typical thermoplastic materials show that the mass loss of melt formed by three thermoplastic materials in the process of air dropping accounts for a considerable proportion of the total mass loss, and the heat loss of high temperature melt in the process of air reverse dropping will also be around. Under the same conditions, the high-temperature melt droplets formed by polystyrene (PS) have a lower reverse dripping rate than polypropylene (PP) and polyethylene (PE) due to their greater viscosity. Due to the difference of the apparent viscosity and the molecular structure of the three thermoplastic materials, polyphenylethylene (PP) is produced. The flow rate of pool fire formed by polystyrene (PS) is slower than that of polypropylene (PP) and polyethylene (PE), but the combustion rate of pool fire formed by polystyrene (PS) is higher than that of polypropylene (PP) and polyethylene (PE) during the flow and spread process in the pool. The higher combustion heat and viscosity of polystyrene make the flame front and flame front formed by the pool fire. The difference of combustion behavior of thermoplastic materials was observed from three aspects of melting, dropping and flowing characteristics. The thermal hazard of dropping flow formed by polypropylene (PP) and polyethylene (PE) was greater than that of polystyrene (PS). Therefore, the thermal hazard of thermoplastic materials in fire protection design was synthesized. On the other hand, the fire spread behavior of thermosetting insulation materials is a complex reaction process coupled with gas-phase combustion and solid-phase pyrolysis. In this paper, the typical thermosetting insulation materials, rigid polyurethane foam (RPU) and soft polyurethane foam (FPU), are selected as the research objects and simulated by external radiation sources. The fire spread behavior of two kinds of insulation materials under different external radiation intensity in actual fire scene is studied. The variation of typical characteristic parameters such as fire spread velocity, temperature field, mass loss, flame fluctuation frequency and flame height with sample width is analyzed emphatically. The process has stronger radiation heat feedback. The reverse fire spread of rigid polyurethane (RPU) and flexible polyurethane (FPU) sheets will accelerate. With the increase of external radiation intensity, a large amount of pyrolysis gas will be produced, which will aggravate the fire. The mass loss rate and fire spread speed are positive with the external radiation intensity. The results show that flexible polyurethane (FPU) foams exhibit better combustibility than rigid polyurethane (RPU) foams because of their own physical structure. When the external radiation intensity is greater than a certain intensity, rigid polyurethane materials will be fully burned along the thickness direction. However, the flame height of the two foams is independent, mainly. Controlled by radiation intensity, the flame fluctuation frequency of rigid polyurethane and flexible polyurethane sheets is coupled with external radiation intensity and width. When external radiation intensity is small, the flame height of rigid polyurethane sheets increases with the increase of plate width; otherwise, the flame height increases with the increase of plate width and the external radiation is strong. The flame front appears a thin melting layer during the combustion of soft polyurethane sheet. We use the oil pool fire theory for reference to predict the flame fluctuation frequency and flame height of soft polyurethane. The experimental data show a good consistency with the theoretical prediction curve.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU551
【参考文献】
相关期刊论文 前1条
1 邹样辉,周建军,钟占荣,范维澄;外加辐射条件下水平方向火蔓延的实验研究[J];中国科学技术大学学报;2001年04期
，本文编号：2209540
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