【作者】 杨愉；

【导师】 钱建民；

【作者基本信息】 重庆大学 ， 供热、供燃气、通风与空调工程， 2006， 硕士

【摘要】 近年来,会展建筑在数量上、规模上以及功能上都不断有新的发展和突破,但由于其建筑结构与使用功能的特殊性,也向建筑火灾安全领域提出了新的挑战。本文通过对当今国内外大空间建筑火灾研究方法的分析比较,针对会展中心建筑特点与火灾特性,选用属于场模拟层次的大涡模拟技术作为研究方法,并选择美国NIST发行的FDS软件作为研究工具。通过将大空间火灾试验与FDS数值模拟结果进行对比,计算值与试验值基本吻合,说明FDS软件能较为准确真实地再现大空间火灾过程,利用FDS软件来研究会展类大空间建筑烟气流动具有可行性与适用性。本课题选用典型会展建筑作为研究对象,通过正交数值模拟试验,比较分析了各因素(排烟口位置、大小、开启数目及排烟量)及其交互作用对其机械排烟效果(烟层高度)的影响,并寻找可能最优的机械排烟方案以优化会展中心烟气控制系统设计。研究表明排烟口位置、排烟量以及排烟口大小与排烟口开启数目的相互作用对考核指标影响显著,是影响机械排烟效果的主要因素,因而在进行展厅机械排烟设计时,应重点考虑以上因素。根据会展中心数值模拟结果,开展展厅火灾羽流发展过程,烟气层发展过程及火灾典型现象分析。研究发现由于展厅空间高大,会展建筑火灾过程中烟羽流温度、速度及浓度衰减非常大,存在烟气层温升小,烟层波动大,发展不均匀等特点,容易产生烟气沉降、弥散现象,这给早期火灾探测及人员疏散带来极大阻碍。当排烟口速度过大时,由于排烟口强烈的抽吸作用,容易产生“卷吸现象”,从而降低机械排烟效率,因而设计排烟口风速时,应考虑临界排烟量。通过排烟效果分析,比较不同排烟口位置及机械排烟量大小对展厅排烟效果的影响,研究发现“顶排”明显优于“侧排”。这是因为与“侧排”相比,顶棚排烟系统能使上升烟气以最短的路径最快的速度流向排烟口,及时排走高温高浓度烟气,减少其与空气混合扩散的几率。而“顶排”时的下部空间气流形式也有助于控制烟层下降。随着排烟量的增大,顶棚排烟方式的优势将更为突出。并就所需排烟量大小、排烟效果、排烟效率以及排烟量确定依据等方面,对国内《高规》及美国NFPA 92B这两种当前广泛使用的确定排烟量的方法进行比较。研究表明美国NFPA 92B综合考虑了火灾荷载、建筑空间尺寸等因素,与传统的换气次数法相比,更为经济合理。但是两种方法在确定因素的考虑上都欠缺全面。笔者建议采用数值模拟方法确定排烟量,可以综合考虑各种因素,做到具更多还原

【Abstract】 In recent years, there are various new development and breakthroughs of the conference and/or exhibition building on their quantity, scale and functions continuously. Sometimes, such a building challenges the fire safety for its special structure and usage function.After comparing various research methods for large space building fire nowadays, LES of field simulation and FDS software, issued by NIST, are selected as research method and tool in this paper.In this paper, a typical conference and exhibition building is selected as research object. Through orthogonal numerical simulation experiment, compare and analyze the influence of each factor on mechanical smoke emission effect to optimize design of somke control system of the conference and exhibition building. The study indicates that the positon of the exhaust port, the quantity of smoke exhaust as well as the interaction between the size and the quantity of exhaust ports are important for mechanical smoke emission effect. Thus they should be taken into account more carefully.Fire phenomena, plume development and smoke layer development within exhibition hall are analyzed according to its numerical simulation result. Due to the large space in the hall, the temperature, the speed and the concentration of the smoke plume minish rapidly. In case of the hall fire, the temperature rise of the smoke is low, the depth of the smoke layer fluctuates is largely and non-uniformly, and the smoke will deposit and diffuse easily. It sometimes interferes into fire detection and evacuation. Oversize exhaust speed through an exhaust port will lead to plug holing, which will reduce efficiency of smoke emission. Hence, critical quantity of smoke exhaust should be taken into account when designing somke control system.Comparing the influence on mechanical smoke emission effect from different exhaust port positons and different quantities of smoke exhaust, it indicates that exhaust port on the roof is obviously better than on the wall. Because somke will be emitted more quickily, and the air implement below the smoke will be helpful to smoke control, when exhaust port is on the roof. The quantiy of the smoke exhaust is larger, the advantage of exhaust through roof is more obviously.Comparing GB50045“code for protection design of tall building”with NFPA 92B,更多还原