地下换乘大厅火灾烟气运动规律及机械排烟效率研究

发布时间：2018-01-13 17:29

本文关键词：地下换乘大厅火灾烟气运动规律及机械排烟效率研究　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着我国经济的迅速发展,中庭类大空间建筑日渐增多,而由于功能需求的不同,往往许多该类大空间建筑在防火设计中超过现有规范要求,发生火灾时,火灾烟气的控制尤为重要,因此需要对排烟技术中的一些关键性参数进行研究。本文以换乘大厅为研究对象,参考国内现有规范,并结合国内外研究现状,确定了换乘大厅建筑特点及烟气控制手段;理论分析了缩小比例模型的可行性,依据相似理论搭建了 1:10的缩尺模型大空间实验平台,采用顶部均匀开口,机械排烟与机械补风的方式;利用FDS模拟软件对3种不同火源功率、4种不同排烟量、5种不同排烟风速、5种不同排烟口高度以及5种不同补风量的实验工况,进行换乘大厅烟气层高度变化与能见度分布的研究;在缩尺实验平台上开展缩尺比例实验,与FDS数值模拟结果进行对比分析,验证FDS全尺寸模型的正确性,并通过实验结果,对换乘大厅烟气温度分布进行了研究;根据实验与数值模拟的结果,将研究成果应用于实际工程中,提出了地下换乘大厅的机械排烟优化方案。实验与模拟的结果表明:(1)大空间内烟气流动较为复杂,整个空间内流速分布不均匀,火灾烟气温度整体温升幅度不大,并不是主要的危险因素,烟气的减光性与毒性是主要的危险因素。(2)不同火源功率下,烟气顶棚温度随着火源功率的增大而升高,烟气层最终稳定高度与火源功率成正比。(3)不同排烟量下,模型空间内整体温度随排烟量的增大而降低,烟气层最终稳定高度与排烟量大小成正比,排烟量越大,烟气层稳定高度越高。(4)不同排烟风速下,模型空间内整体温度随着排烟风速的增大而降低。烟气层最终稳定高度与排烟风速成正比,排烟风速越大,烟气层稳定高度越高,但存在一定的限制,当风速增大到一定程度时,烟气层稳定高度的提升效果将减弱。(5)不同排烟口高度下,烟气层稳定高度与排烟口高度先成正比关系,后成反比关系。过高或过低的排烟口高度对于烟气的流动与排出都有较大的扰动影响。(6)不同补风量条件下,烟气层最终稳定高度与补风量大小成正比,补风量越大,烟气层稳定高度越高,但变化差距较小。(7)通过三种方案的比较,本课题为沙坪坝项目中换乘大厅的机械排烟方案的优化给出了以下建议:a)换乘大厅内不设置任何商业(包括零星商业),降低火灾规模;b)换乘大厅内设置机械排烟系统,以最大火源强度为4MW火源,且在20分钟内将烟气层高度控制在危险高度2.6m以上考虑,排烟量不应小于65000m3/h,排烟口风速建议取不小于2m/s,排烟口高度建议布置在距离顶棚2～3m高度处;c)设置机械补风系统,补风量按排烟量的50%设计;d)性能化设计与设计单位所做方案都能较好的满足排烟要求。
[Abstract]:With the rapid development of economy in our country, the large space buildings of atrium are increasing day by day. However, because of the different functional requirements, many large space buildings in fire prevention design often exceed the requirements of existing codes, when fire occurs. Fire smoke control is particularly important, so it is necessary to study some key parameters in smoke exhaust technology. This paper takes the transfer hall as the research object, referring to the existing domestic norms, and combined with the domestic and foreign research status. The building characteristics of the transfer hall and the means of smoke control are determined. The feasibility of reducing the scale model is analyzed theoretically. According to the similarity theory, the large space experiment platform of the 1:10 scale model is built, which adopts the mode of uniform opening at the top, mechanical smoke exhaust and mechanical air supply. FDS simulation software was used to study the experimental conditions of three different power sources, four different exhaust volumes, five different exhaust air speeds and five different outlet heights as well as five different supplementary air volumes. The change of smoke layer height and visibility distribution in the transfer hall are studied. The scale experiment was carried out on the scale experiment platform, and compared with the FDS numerical simulation results to verify the correctness of the full-scale FDS model, and through the experimental results. The temperature distribution of flue gas in the transfer hall is studied. According to the results of experiment and numerical simulation, the research results are applied to practical engineering. The optimization scheme of mechanical smoke exhaust in underground transfer hall is put forward. The experimental and simulation results show that the flow of flue gas in the large space is more complicated and the velocity distribution is not uniform in the whole space. The overall temperature rise of fire smoke is not the main risk factor, but the decrease of light and toxicity of smoke is the main risk factor under different fire source power. The flue gas ceiling temperature increases with the increase of the fire source power, and the final stability height of the flue gas layer is proportional to the fire source power, and the overall temperature in the model space decreases with the increase of the smoke exhaust volume. The final stability height of flue gas layer is in direct proportion to the amount of exhaust smoke. The larger the amount of smoke exhaust, the higher the stable height of flue gas layer. The overall temperature in the model space decreases with the increase of the exhaust wind speed. The final stability height of the flue gas layer is proportional to the exhaust wind speed. The larger the exhaust wind speed, the higher the stable height of the flue gas layer, but there are some limitations. When the wind speed increases to a certain extent, the lift effect of flue gas layer stability height will weaken. Too high or too low flue gas outlet height has great disturbance effect on flue gas flow and discharge. (6) under different rewind volume conditions, the final stable height of flue gas layer is directly proportional to the volume of supplementary air. The greater the amount of supplementary air, the higher the stable height of flue gas layer, but the difference is small. This subject gives the following suggestions for the optimization of the mechanical smoke exhaust scheme of the transfer hall in Shapingba project: (1) there is no commercial establishment in the transfer hall (including sporadic commerce to reduce the scale of fire; B) the mechanical smoke exhaust system is set up in the transfer hall, the maximum fire source intensity is 4MW fire source, and the height of the flue gas layer is controlled above 2.6m in 20 minutes. The amount of exhaust smoke should not be less than 65000m3 / h, the wind speed of exhaust outlet should be not less than 2m / s, and the height of exhaust outlet should be arranged at the height of 2m / m from the ceiling. C) set up a mechanical air supply system, the amount of air supply according to the 50% of the smoke design; D) performance-based design and design units can better meet the smoke requirements.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU967

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