【作者】 许磊；

【导师】 张和平； 程旭东；

【作者基本信息】 中国科学技术大学 ， 安全科学与工程， 2014， 博士

【摘要】 建筑节能是国家“节能减排”政策的关键措施之一,主要通过建筑保温节能技术来实现。聚苯乙烯(PS)外墙外保温系统(ETICS)具有保温隔热性能好、施工方便、价格便宜等优点,是外墙外保温系统中应用最广泛的系统。然而,建筑外立面完全处于开敞环境中,外墙外保温系统中的有机保温材料极易燃烧,并缺乏对外墙外保温系统火灾进行有效控制和扑救的手段,导致一旦发生火灾,容易形成竖向立体火蔓延,火灾发展速度快且难以扑救,存在较高的危险性。在外墙外保温系统的火灾发展过程中,可燃物的辐射引燃过程是其中的一个关键阶段,对于研究系统的火灾危险性具有重要意义。因此,本文选取挤塑聚苯乙烯(XPS)-ETICS展开相关研究,针对其在竖直条件下的辐射引燃过程进行实验研究及理论分析。当前,国内外学者对XPS材料的研究大多是关于XPS材料的制备、热解、燃烧行为的研究,尚缺乏对XPS保温板在竖直条件下辐射引燃过程及XPS-ETICS的火灾特性的研究。因而本文利用自主设计搭建的垂直辐射源作用下热塑性材料熔融滴落引燃平台,实验研究了XPS保温板的辐射引燃过程,并进一步研究了XPS-ETICS的辐射引燃过程,分析了保护层结构对外墙外保温系统火灾特性的影响。论文首先分析了XPS保温板的辐射引燃过程,研究了不同燃烧等级的XPS保温板在不同辐射热流强度及有无外加点火源等因素影响下的辐射引燃过程,分析了材料的引燃时间、质量变化及温度分布等参数的变化规律。研究结果显示,在竖直方向下XPS保温板的辐射引燃过程分为初始、收缩、熔融滴落、热解及引燃5个阶段；引燃方式不同导致引燃时间的差值随辐射强度的增加而减小,并且该差值在较高热流强度下近似可以忽略,对于B1级材料为50kW/m2,B2级材料为35kW/m2;试样的滴落速率、热解失重速率均随辐射强度的增加而增加,但其增加的幅度不断减小；分析了不同燃烧等级材料在不同辐射强度下的材料引燃前最高温度变化的情况,结果显示随热流强度的增加自然辐射引燃过程中的温度变化较为明显。其次,基于XPS保温材料在竖直条件下辐射引燃过程研究,建立了热塑性发泡材料在竖直条件下的引燃时间预测模型。预测模型根据实验中质量是否发生变化将XPS材料的辐射引燃过程分为升温熔融、热解点燃两个阶段。通过对不同燃烧等级、不同辐射热流强度下的实验数据进行验证,结果表明提出的模型能够较好的预测热塑性泡沫材料的引燃时间。论文最后进一步研究了XPS外墙外保温系统的引燃行为和火灾特性,着重讨论了外墙外保温系统中保护层的作用,对比分析了有无保护层条件,保护层脱落和不脱落条件下的引燃过程。实验结果表明：在有保护层条件下,系统的引燃时间比纯XPS板辐射引燃过程的时间长,但保护层脱落后的引燃时间比纯XPS板辐射引燃过程的时间短；系统的引燃时间在不同燃烧等级材料之间的差距较小,且在较高热流条件下可近似忽略。试样的滴落速率随辐射强度的增加而增加,保护层的存在导致其在保护层脱落前失重速率较小,脱落后材料的失重速率大约增加2倍,引燃后材料的失重速率大约增加2倍。分析温度变化可以看出,脱落前最高温度同引燃前最高温度之间存在较大差距,且随着辐射强度的增加而减小,在60kW/m2的条件下可以忽略这种差距；保护层未脱落条件下的系统引燃需要较高的热流强度；进一步分析了墙角火条件下外墙外保温系统的内部温度在垂直试样表面及沿试样竖向方向的变化规律。更多还原

【Abstract】 Building energy efficiency is a key measure of national policy of "energy conservation and emission reduction", mainly realized through the external thermal insulation composite systems (ETICS) technology. The ETICS, especially based on polystyrene (PS) foam, has been widely used in china, which has some advantages of good thermal protection performance, light weight, convenient operation and low prices etc. However the ETICS, once on fire, can easily form a stereoscopic fire spread on the building facade, difficulty to extinguish and no effective measure to control its fire in open environment. Thus, its fire characteristics need to be studied urgently, in order to assess the fire risk of ETICS. Due to the ignition being an important stage during the fire process, a series of experiments and theoretical analysis are carried out under the radiation ignition process of the ETICS on polystyrene, in the purpose of researching its fire risk.Nowadays, researchers mainly pursue research on the material characteristics, manufacturing process, pyrolysis and burning behavior of polystyrene. There are few studies on the ignition process of XPS-ETICS in the vertical condition. Therefore a melting and dripping ignition of thermoplastics platform is designed to study the ignition process of the xps and xps-etics, and then is used to analysis the system structure effect on the fire features.In the first stage, the radiation ignition process of XPS insulation panel is taken for consideration. The burning behavior class, the radiation flux level and the way to ignite is mentioned during the experiments, and several important parameters including the time to ignition (piloted ignition and auto ignition), the mass of pyrolysis and the temperature distribution in the sample is measured. The burning process, including origin, shrinking, melting and dripping, pyrolysis and ignition phases, has been described in the experimental results. The difference of tig between the auto ignition and the piloted ignition decreases as incident heat flux increasing, and it is quite insignificant once the incident heat flux exceeds50kW/m2for B1and35kW/m2for B2. Comparing with the auto ignition process, the difference of tig between B1and B2is much smaller in piloted ignition condition. The dripping and the pyrolysis rate of the sample rise while the incident heat flux increase although the increasing rate is dropping. The highest temperature before ignitions changes more obviously during the process of auto ignition.Secondly, based on the analysis of the ignition process of XPS and theoretical derivation of heat transfer, the prediction model of tig is put forward to thermoplastic foaming material in vertical condition. On the basis of the mass change, the ignition process is divided as heating-melt and pyrolysis phase in the model. Comparing with the data of the ignition experiment, the model can better match and predict the tig for the thermoplastic foaming material in vertical condition.In the end, the fire behaviors of the ETICS are discussed and focused on the role of the rendering layer during the experiments, along with the comparison analysis of the ignition process with and without the rendering layer and with the dropped behavior of the rendering layer or not. The difference of tig between different combustion grade materials is smaller than the pure xps. The dripping rate rises while the radiation flux increases. The pyrolysis rate is quite small before the rendering layer dropped, once the rendering layer dropped that increases about two times, and the pyrolysis rate also increase two times as soon as the material be ignited. There are larger gap of the maximum temperature of rendering layer dropped comparing with that of ignition, which is decreased as the radiation flux increase, but it can be ignored when the radiation flux exceed to60kW/m2. Even higher radiation flux is needed in the ignition process under the condition of rendering layer remained. Furthermore, the fire behaviors of ETICS under comer fire are studied, and the temperature vertical along with the sample surface are investigated.更多还原