共查询到19条相似文献,搜索用时 140 毫秒
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本文主要利用计算流体动力学CFD技术,对香港西九龙总站地下停车库火灾不同产烟量对能见度的影响进行了数值模拟分析。模拟结果表明:在火灾大小为2 MW的情况下,排烟系统的排烟量在9.6~20 m~3/s范围内,火灾较高产烟量(Ys=0.064)时,2.2 m清晰高度处的温度不超过60℃,但能见度低于10 m;在较低产烟量(Y_s=0.028)时,20 m~3/s的排烟能力能确保2.2 m清晰高度处的能见度大于10 m,可以提供人员安全疏散环境。合理选择火灾的产烟量是决定利用火灾工程方法计算排烟系统能力大小的关键. 相似文献
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为了分析防护工程机械排烟量大小对走廊烟气扩散影响,利用火灾模拟软件FDS对防护工程"单室-走廊"模型火灾时顶棚排烟口状态及不同排烟量的排烟效果进行了模拟,分析不同工况下走廊内不同区域的烟气温度、能见度及二氧化碳浓度.结果表明:由于走廊两端向火区"补风",开启排烟口会降低火源附近排烟效果,在其他区域则能有效提高排烟效果;火灾前期,不同排烟量的排烟效果没有太大差别,火灾后期,排烟量为1800 m~3/h与2700m~3/h对走廊中段的排烟效果几乎一致,继续增大排烟址,能有效提高排烟效果。但在疏散出口处,排烟量为1800 m~3/h时,排烟效果最好,考虑人员逃生安全和经济效益,本模型中单个排烟口最优排烟量确定为1800 m~3/h。 相似文献
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本论文对地下组合受限空间火灾初期的分区现象进行了模拟试验和数值分析。地下组合受限空间火灾呈现出特殊的分区现象。一般可分为燃烧区、新鲜空气补充区、烟气流区、过渡区和火焰后面的“惰化区”五区。有上下两层的地下复杂组合受限空间可分为燃烧区、烟气流区、新鲜空气补充区和“惰化区”4区。将数值模拟分析结果与实验结果进行了比较,二者吻合较好。研究表明,本文所采用的组合受限空间火灾三维模拟分析模型,是一种既能实现对实际结构复杂火灾现象的模拟分析又能在一定程度上满足实际工程要求的较好分析方法。 相似文献
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本文建立了地下狭长受限空间火灾模拟实验台架,完成了不同燃烧物种类、不同燃烧物质量的火灾燃烧实验,建立了适用于狭长式地下受限空间火灾的大涡三维数学模型。研究重点在于测量狭长式地下受限空间火源热释放率和烟气温度分布,得到燃烧物分别为柴油、汽油的火源热释放率及烟气温度分布的实验测量数据;结合实验完成了狭长式地下受限空间火灾的大涡三维数值模拟分析。通过火灾数值模拟结果与实验结果进行比较分析,本文所建立的模型能较为真实地反映实际狭长式地下狭长受限空间火灾的情形。 相似文献
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Abstract The adverse effects of a sprinkler on smoke exhaust systems used to be debated in designing fire safety provisions. However, very few experimental studies on the interaction of a sprinkler with the smoke layer have been reported; therefore, this study investigates and reports on the interaction of a smoke layer with a sprinkler water spray by a specially designed rig with 25 tests. Smoke spreading from a fire chamber was collected in an adjacent hall. The stability of the smoke layer was then studied by the discharged water spray. The ratio of spray drag to smoke buoyancy is proposed to determine smoke stability. 相似文献
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With the development of urban rail transit, ensuring the safe evacuation of pedestrians at subway stations has become an important issue in the case of an emergency such as a fire. This paper chooses the platform of line 4 at the Beijing Xuanwumen subway station to study the emergency evacuation process under fire. Based on the established platform, effects of the fire dynamics, different initial pedestrian densities, and positions of fire on evacuation are investigated. According to simulation results, it is found that the fire increases the air temperature and the smoke density, and decreases pedestrians' visibility and walking velocity. Also, there is a critical initial density at the platform if achieving a safe evacuation within the required 6 minutes. Furthermore, different positions of fire set in this paper have little difference on crowd evacuation if the fire is not large enough. The suggestions provided in this paper are helpful for the subway operators to prevent major casualties. 相似文献
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提出一种基于火点与背景的类间方差和烟雾掩膜的红外光谱火点检测算法。该算法的潜在火点判定阈值设为305K,再利用MODIS热红外光谱通道亮温数据的类间方差值将森林火灾火点从背景中区分出来,并对低温闷烧火点采用烟雾掩膜进行识别。应用该算法对福建省和黑龙江地区的林火数据进行探测处理,与传统MODIS火点检测方法比较分析表明,该算法使用简单高效,在不同环境适应性较强,可以更准确地检测到高温明火点和一些低温闷烧火点,降低了火点的误报率和小火点的漏报率,检测效果更理想。 相似文献
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声波团聚技术在细颗粒物排放控制领域具有很好的应用前景,最近衍生发展为一种全新的火灾烟雾控制手段。该文对声波团聚技术发展现状进行全面总结,介绍近年的实验和理论研究进展。随后,阐述了声波团聚消烟的基本原理,并以火灾烟雾中占比较大的电缆燃烧烟雾为实验对象,发现声波团聚技术在一分钟后就实现对电缆燃烧烟雾的完全消除,即存在突出团聚效果。该结果验证了该技术在火灾烟雾控制领域的可行性。最后,依托我国城市发展现状,探讨了声波团聚技术在火灾消烟的发展前景。 相似文献
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Space-time correlation functions have been derived for the time-varying intensities of speckle patterns in image space produced by a series of moving random-phase screens. The time-correlation length, which measures the changing rate of intensity fluctuations, is evaluated from the correlation functions to examine the effects of the imaging properties on the temporal behaviour of the speckles resulting from the multiple scattering. It is shown that the average velocity and velocity dispersion of the phase screens can be measured from the time-correlation length by using imaging systems which have a small and a large point spread at the front focal plane of the systems, respectively. Theoretical results for the relationship between the focal position of the imaging lens and the time-correlation length are also presented. 相似文献