【作者】 赵威风；

【导师】 廖光煊； 宗若雯；

【作者基本信息】 中国科学技术大学 ， 安全科学与工程， 2013， 博士

【摘要】 城市化进程不断加快,出现了越来越多的大型建筑和隧道空间。在外型上,许多建筑都为狭长空间。狭长空间火灾的发展受诸多因素的影响,比如燃料、火源尺寸、壁面材料、开口条件及通风条件等。因此,开展狭长空间影响火灾发展规律的因素研究有着重要意义。本文利用小尺度实验模拟、及数值模拟相结合的方法,研究了狭长空间内的火灾发展规律及燃烧特性的变化规律。通过文献调研,分析研究后搭建了小尺寸实验台,在此基础上搭建了小尺寸狭长空间火灾实验台,实验过程中通过改变不同的边界条件开展了一系列的实验,测量了烟气温度、浓度和质量损失速率,研究不同工况条件下狭长空间火灾的发展过程。最后对实验数据进行处理,分析研究了各种工况条件下狭长空间火灾的燃烧特性。通过实验模拟,首先研究了准稳态条件下开口形态的影响,正庚烷的无量纲质量损失速率随开口的增大而减小,且服从指数衰减规律；另一方面,不同开口大小的无量纲质量损失速率变化趋势相同,而且无量纲质量损失速率随开口尺寸的增大而减小。其次针对远火源场,实验证实了温度的纵向衰减符合指数关系,几种开口大小的远火源端纵向温度衰减因子变化规律一致,均随着中性面高度的增加而增大；而且中性面高度相同时,远火源端的纵向温度衰减因子随开口大小的增大而增大。之后,实验还证实了竖向温度分布属于高斯型,最高温度距顶棚的位置随中性面高度变化趋势相同。利用小尺寸实验模拟,研究开口位置耦合火源尺寸下的火灾发展情况。通过与开放空间Babraluskas经验值以及狭长空间0. Megret模型预测值的对比,单位面积的质量损失速率在Babraluskas经验值的最小值和最大值之间变化,但不是线性增长,而是先减小后增大；实验值比狭长空间0. Megret模型预测值高。针对狭长空间温度分布,不同油盘尺寸的无量纲顶棚温升变化趋势相同,服从指数衰减,而且具有高度的相似性。在远火源区,油盘尺寸对各断面处无量纲竖向温升分布规律影响可以忽略,不同油盘尺寸的各断面处无量纲温升均很好的服从高斯分布,并具有很高的相似性。随后,通过实验模拟研究了狭长空间双火源燃烧特性。研究发现,火源1和火源2不同油盘尺寸对其质量损失速率的影响比较复杂,整体而言,火源2油盘尺寸小对火源1的影响较小,油盘尺寸较大时将抑制火源1的燃烧。远火源区竖向温度分布具有高度的相似性,服从高斯分布,不随火源2油盘尺寸的变化而改变。此外,火源1的燃烧充分与否直接影响C0浓度的产量。而对于延时点火的实验研究,火源2延时点火时火源1的质量损失速率明显高于未延时的；相对于单一火源,延时点火的质量损失速率峰值明显较小。延时点火时C0浓度峰值几乎相等,相对于未延时点火的情况,C0浓度峰值小了一个量级。最后,利用小尺度狭长空间实验台的测量数据和数值模拟软件FDS研究了狭长空间双火源对燃烧特性的影响。通过FDS模拟,给出了x-z平面上温度场和速度场随时间的变化情况,并通过对比发现双火源作用下,对于双火源之间的温度分布而言,着火后不久燃烧比较充分,此时FDS模拟产生的烟尘高于实验值,双火源之间FDS模拟温度较高；充分发展后,燃烧不充分,FDS模拟产生的烟尘低于实验值,造成了此时的FDS模拟温度较低。对于远火源区,FDS模拟温度普遍低于实验值。更多还原

【Abstract】 With the world’s rapid economic development and accelerating process of urbanization, the number of huge building and tunnel space is increasing. In appearance, many buildings should be long and narrow space, which act as main passage for walking and fire evacuation path for a fire accident. It facilitates the human life, but also brings some fire hazards. The development of the long-narrow space fire is influenced by many factors, such as fuel, the size of fire source, opening conditions, ventilation conditions, etc. Therefore, carrying out the study of factors affecting fire development law in a long-narrow space is of great significance,In this study, by means of combining small-scale experiments and numerical simulation, fire development law and variation of combustion characteristics in a long-narrow space have been studied. Referring to previous research methods and ideas, a small-scale long-narrow space fire bench is constructed. By changing the opening configuration, fire source area, shape of fire source, fire source location and other boundary conditions, the fire occurrence process in the long-narrow space is reproduced and the parameters in fire process, such as smoke temperature, density, thermal radiation flux on the floor and mass loss rate of fire source, is measured accurately, which offer data support for comparison validation and discussion between theoretical model and numerical simulation.First, with a series of experiments, the effect of opening configuration in a quasi-steady-state had been studied. Dimensionless mass loss rate of n-heptane reduced with the increasing of opening size and was subject to exponential decay. On the other hand, dimensionless mass loss rate of different opening sizes had the same change tendency. Second, for the far fire source field, the experiments confirmed that the longitudinal temperature reduction was subject to exponential relationship and the decay factors of longitudinal temperature reduction with several different opening sizes had the same variation, which increased with the increase of the neutral plane height. Also, when the neutral plane height was same, the decay factor of longitudinal temperature reduction would grow up with the increase of opening size. After that, experiments also confirmed that the temperature profile had a good agreement with Gaussian distribution and the location of the maximum temperature from ceiling varied with the neutral plane height. According to a series of small scale experiments, the influence of fire size coupling with opening position on the fire development was studied. Compared to the Babraluskas empirical value in open space and the predicted value by O. Megret model in long-narrow space respectively, the mass loss rate per unit area ranged from the minimum to the maximum of Babraluskas empirical value, which decreased at the beginning and increased subsequently, rather than linear growth; and the measurements were higher than the predicted values obtained by O. Megret model. The dimensionless ceiling temperatures of the oil pans with different sizes all had agreement with exponential attenuation, and the variation trend was highly similar. For the far fire source field, the influence of the oil pan size on the dimensionless ceiling temperatures at different cross sections could be ignored; the dimensionless ceiling temperatures at different cross sections with different sizes of the oil pans had good agreement with Gauss Distribution, which was also highly similar.Subsequently, the combustion characteristics with double fire sources in long-narrow space were studied by a series of experiments. The results showed that the influence of the two fire resources on the mass loss rate was quite complicated. As a whole, it would strongly restrain the combustion of fire source at the closed end when the size of fire source in the middle increased. For the far fire source field, the temperatures at different cross sections had good agreement with Gauss Distribution, which were not affected with fire source size in the middle. When fire source in the middle ignited after fire source at the closed end, mass loss rate of the latter was higher obviously than the experiments that were not delayed.Finally, comparing with the results measured in a series of small scale experiments, the influence of double fire sources in long-narrow space on the combustion characteristic was studied by Fire Dynamics Simulator (FDS). The variation of temperature distribution and velocity distribution in X-Z plane over time is studied through FDS simulation. The results showed that when double fire sources existed in long-narrow space, the velocity distribution between the double fire sources as well as in the region far from the fire source had good agreement with Gauss Distribution respectively. In the region between the two fire sources, the simulated smoke temperature was higher than measured results, and the deviation mainly came from the underestimate of the mass loss rate after the complete combustion. While in the region far from the fire source, the simulated temperature was lower than measured results.更多还原