Effectiveness of downward evacuation in a large-scale subway fire using Fire Dynamics Simulator

Effective evacuation routes in the case of a large-scale subway fire were studied. A serious problem in the subway fire is that the directions of smoke flow are coincident with those of evacuation toward the surface. Hence, it is necessary to design an evacuation route without interference from smoke. A disastrous fire broke out in the Jungangno subway station in Daegu, South Korea in 2003. Based on this case, the Jungangno subway station with three basement levels was used in Fire Dynamics Simulator model in this study. The influences of smoke, temperature, and toxic gases (carbon monoxide [CO] and carbon dioxide [CO₂]) were computed at the evacuation staircases in the subway station with a fire source in the third basement floor (B3). The calculations showed that the evacuation staircases had high smoke density, temperature, and concentrations of CO and CO₂ in the subway fire. Hence, these factors greatly affected all of the upward evacuation staircases due to the coincidence of the smoke flow and the evacuation routes. Therefore, our paper proposes a new subway station with a fourth basement floor (B4) having downward evacuation routes which are in the opposite direction to the smoke flow. The results of analysis show that these factors hardly affected the staircases from B3 to B4. We conclude that downward evacuation can be more effective than upward evacuation for a large-scale subway fire.     

A global soot model developed for fires: Validation in laminar flames and application in turbulent pool fires

In this study, a global soot formation model based on the LSP (Laminar Smoke Point) concept in combination with the soot oxidation model developed by Leung et al. [40] is validated in three laminar flames: a non-smoking and a smoking ethylene flame, as well as a non-smoking propane flame, and then applied in two turbulent pool fires fueled by ethylene and methane, respectively. In this global soot model, the sooting propensities of different fuels are accounted for by a pre-exponential factor determined from the LSP height, providing a general and practical solution for soot modeling in multi-fueled fires. The flame fields are solved by FLUENT with UDFs to provide material properties and add additional soot governing equations. A-CSE (Alternative Conditional Source-term Estimation) approach is adopted to handle the interaction between soot chemistry and turbulent flow in the turbulent fires.The model parameters such as the pre-exponential factor, soot inception limits and soot particulate surface area are determined and calibrated against the experimental data. Mixture fraction and temperature are first verified to provide a good premise for soot modeling. Good agreements between the predicted and measured soot volume fraction, as well as the reproduction of transition from non-smoking to smoking flames, demonstrate the capability of current global soot model in accurately predicting soot for both laminar flames and turbulent fires. Using the A-CSE soot modeling approach together with the global soot model, this study presents a general effective yet computationally efficient global soot modeling framework for fires.     

Ausmaß und Folgen des Tabakkonsums und Passivrauchens in Deutschland

In consequence of the health hazards of smoking and environmental tobacco smoke (ETS) and the high prevalence in the German population there are more than 100,000 deaths annually in Germany. Still more than half of the German population ever starts smoking and currently about a third of the adult population and a fifth of the adolescents are smokers at present. Additionally about 55 percent of all non-smokers between the age of 18 and 79 are often exposed to ETS at home, at work or in their leisure time. A differentiation of smoking prevalence and of exposure to ETS concerning socio-economic determinants shows that social differences have grown with successive birth cohorts. Thus, significant social inequalities can be observed today. In contrast to this, gender differences are becoming increasingly irrelevant, particularly in smoking prevalence. Tobacco consumption and ETS therefore has become one high-priority field of action of health and prevention politics in Germany, which manifests in an improved tobacco control policy. International achievements in the implementation of a comprehensive tobacco control policy show however, that in Germany further efforts are needed to reduce smoking prevalence significantly. Eingegangen: 11. Mai 2007; Angenommen: 15. Mai 2007     

卷烟主流烟气中一氧化碳含量测量 不确定度的评定

目的评定卷烟主流烟气中一氧化碳含量的测量不确定度,为测定主流烟气中一氧化碳含量提供有效、可靠的测量数据。方法根据JJF(烟草)1-2007《卷烟主流烟气中烟碱、焦油和一氧化碳测量不确定度评定指南》的指导方法,对卷烟主流烟气中一氧化碳的测量过程进行研究,系统分析整个测量结果的不确定度来源,建立不确定度的数学模型,并确定测量结果的置信区间。结果结果表明一氧化碳测量的不确定度主要是由环境波动、示值、抽吸口数造成的,因此在检测过程中应尽量减小测试环境的波动性及提高示值的精度,才能进一步减小测量不确定度。结论该批卷烟样品的测定结果:一氧化碳含量为10.2 mg/支,扩展不确定度为0.7 mg/支。     

Effect of cross section on critical velocity in longitudinally ventilated tunnel fires

Numerical and theoretical work was conducted to investigate the effect of tunnel cross section on critical velocity for smoke control in longitudinally ventilated tunnel fires. The results show that for small fires, the critical velocity decreases with both the increasing tunnel height and tunnel width. For large fires, the critical velocity significantly increases with the increasing tunnel height but is independent of tunnel width. Different calculation models are compared with a focus on effect of tunnel cross section. A new correlation is proposed to account for the effect of tunnel width based on the previous model.     

羟基锡酸锌的制备及其对PVC电缆材料的阻燃消烟作用

研究了在Sn4+和Zn2+共存的水溶液中,以氢氧化钠为沉淀剂合成的纳米羟基锡酸锌（ZHS）。采用X射线粉末衍射、傅里叶红外和环境扫描电镜表征证明合成的ZHS是边长为380nm左右的纳米立方体。采用"熔融共混法"制备PVC电缆材料,通过极限氧指数、烟密度、环境扫描电镜炭渣形貌表征比较了ZHS与三氧化二锑（AO）对PVC的阻燃消烟作用。通过真空裂解气相色谱－质谱联用分析了阻燃PVC电缆材料的裂解产物,并结合燃烧性能的测试结果,推断了ZHS对PVC电缆材料阻燃消烟作用的机理。结果表明,用量相同时,ZHS对PVC电缆材料的成炭作用总是优于AO。添加量小于10份时,AO对LOI和SDR的影响优于ZHS;但添加量大于15份后,增加ZHS的用量可以进一步提高氧指数和降低烟密度值。     

PVC的阻燃与抑烟

本文采用正交实验的方法,研究了聚氯乙烯发烟量的控制。实验得到了无机阻燃剂、无毒、低烟,在聚氯乙烯中的填充量小,克服了传统无机阻燃剂填充量大、降低聚合物加工性能和力学性能的缺点。     

红磷烟幕对10.6 μm激光的消光系数测试研究

论述了红磷烟幕的成烟过程与遮蔽特性。在烟幕试验柜中测试了红磷烟幕对两种入射功率10．6μm激光的质量消光系数和红磷烟幕的粒度分布规律;根据米氏散射理论计算了单个红磷烟幕粒子对10．6μm激光的吸收效率因子、散射效率因子和消光效率因子。结果表明：红磷烟幕对入射功率分别为0．552、1．032W的10．6μm激光的平均质量消光系数分别为0．6027、0．5739m^2／g。成烟5min时红磷烟幕粒子的平均直径为2．47μm。研究表明,红磷烟幕对10．6μm激光的消光作用以吸收效应为主,其质量消光系数随浓度的增加而下降。同等条件下入射光的功率越大或空气的相对湿度越小．则红磷烟幕的消光系数就越小。     

自动设定烟气出口温度改善余热回收效率的方法

我国现役燃煤机组排烟温度普遍偏高,里面蕴含着提高锅炉效率的巨大节能空间。为了更高效地利用余热,并达到控白烟的目的,嘉华发电有限公司7号机组通过改造,采取了利用烟气余热回收加热凝结水的方法,实现了余热回收的初步节能效果。