试析高层建筑防排烟系统的常见问题

防排烟系统设施是高层建筑保障人民生命财产安全不可缺少的消防安全设施.防排烟系统共有三种类型:自然排烟系统、机械排烟系统、机械加压送风系统.由于部分设计、施工人员对防排烟设施的结构、作用、性能缺乏了解,对国家规范标准理解不够透彻,往往导致在设计、施工中出现防排烟系统设施配置被忽略或有配置而功能不全等现象.本文主要列举了高层建筑的3种防排烟系统在设计、施工和验收中的若干常见问题,以期引起设计、施工、管理和使用人员的重视.     

高层建筑防排烟设计浅析

高层建筑由于层数多、火灾时外部救援难,在防火方面的要求远高于低层或多层建筑。防排烟作为建筑防火的一项重要措施,对火灾逃生及救援有着十分重要的作用。本文对高层建筑防排烟设计中碰到的一些问题进行简要的分析与探讨。     

高层建筑竖井内烟气流动特性及控制方法

竖井火灾烟气流动特性和控制是与高层建筑火灾安全紧密相关的问题。从竖井烟气流动作用因素、烟气参数分布特性与烟气上升速度3个方面论述了对于高层建筑竖井烟气流动特性的研究现状。总结了目前常用的竖井烟气控制方法及工程实践中存在的问题,提出了改善烟气控制效果的方法和思路。     

Development of CAU_USCOP,a network-based unsteady smoke simulation program for high-rise buildings

In this study, a new network-based unsteady smoke control program, CAU_USCOP (Chung-Ang University, Unsteady Smoke Control Program), was developed for use in high-rise buildings. This program solves the unsteady conservation of mass and energy equation. Using CAU_USCOP, we then analyze the movement of smoke in a high-rise building according to the existence of a natural smoke release unit. Moreover, the strength of the stack effect is estimated using the movement of a neutral plane in a stairwell over time. The neutral plane in the case with the natural smoke release unit descends 90% less than the case without the unit, and the natural exhaust in the fire room should be helpful in reducing the risk from fire.     

高层建筑火灾消防及安全逃生研究

高层建筑的火灾是威胁居民生命财产安全的重要因素,对高层建筑火灾进行深入的研究,能够降低火灾发生的可能性,并减少火灾带来的人身伤害和财产损失。本文分析了高层建筑发生火灾的原因,同时分析了高层建筑火灾的特点。高层建筑由于其建筑本身的高、人员密集以及室内空间较复杂等特点决定了发生火灾时危害性很大。本文之后给出了若身处高层建筑火灾中应采取的几点逃生策略,以便有效地降低人员的伤亡。最后,本文介绍了逃生模拟软件FDS+Evac,该软件可以有效地模拟火灾时室内温度场、烟流分布等情况,可以指导人员进行安全逃生。     

Numerical simulation of the spread of smoke in an atrium under fire scenario

The Fire Dynamics Simulator code is used to investigate the smoke movement in an atrium under fire scenario. At first, by comparing with experimental data of the atrium fire under low and high heat release rates, reasonable model constants of C_s and Pr_t and appropriate grid system are determined for simulating smoke movement in the atrium, the simulation results are in good agreement with those experimental data. Then, the performance of different smoke exhaust methods in the atrium is studied. Smoke filling processes are investigated under different natural and enhanced smoke exhaust methods. Simulated results show that natural smoke exhaust method is preferred when the smoke exhaust vents are located at the ceiling of the atrium. On the other hand, when the smoke exhaust vents are located on the walls of the atrium, the higher positions of the smoke exhaust vents are preferred. In addition, the influence of the fire source locations on the smoke spreading process is presented in this paper, three kinds of fire source locations are studied, they are central fire, side wall fire and corner fire. Results indicate that the descending process of the smoke layer is the slowest when the fire source is at the corner of the atrium.     

高层建筑防火排烟设计探讨

在当前的城市建设过程中,高层建筑已经成为了城市建设的主要建筑形式,为了满足当前高层建筑物内部结构以及功能性方面的要求,高层建筑的内部设计也呈现出复杂性的特征,这给高层建筑物的消防工作带来了巨大的挑战,文章立足于实际,结合高层建筑物设计的相关内容,对当前我国高层建筑防火排烟设计的相关细节内容进行了探讨与分析.     

Experimental Studies of Electromagnetic Wave Attenuation by Flame and Smoke in Structure Fire

Attenuation of electromagnetic waves in the fire scene is an important issue when the stability of wireless communication is concerned, especially in fire rescue scenarios of high-rise buildings. Therefore, it is of importance to study the effects of flame and smoke on the attenuation of electromagnetic waves in structure fire. In this article, the influence of flame was studied through using alcohol as fuel. Different types of fuels were used to produce different concentrations of smoke. Different ranges of electromagnetic wave frequency from 350 MHz to 400 MHz were also used to investigate the frequency-dependent properties of the attenuation effect. The results show that flame itself does not have significant effects on the electromagnetic wave attenuation, but smoke plays an important role. Smoke from diesel fuel results in larger signal attenuation than other fuels, with attenuation of 1.16 dB at 300 MHz. The relationship between the concentration of smoke and signal attenuation follows the first-order exponential function. It also indicates that electromagnetic wave attenuation is frequency-dependent. The attenuation is 5.43 dB at 360 MHz when the smoke concentration is 20 dB/m, but only 0.26 dB at 400 MHz. It is suggested that a frequency-dependent assessment should be considered for investigating the reliability of the wireless communication system in structure fire in high-rise buildings.     

住宅凹口火灾烟气对外廊的影响分析

通过建立高层住宅凹口内烟气流动的数学模型,分析研究凹口内烟气对外廊的影响,得出在火灾发生初期,烟气主要影响靠近火灾发生层以上几层的外廊,随着时间的推移,烟气影响区域逐渐向上移动,在烟气发生量稳定后烟气主要影响距火灾发生层十层以上的外廊。不同的凹口尺寸,烟气会对外廊有不同的影响,横向增大凹口尺寸并不会对外廊烟气分布产生显著的影响,纵向增加凹口尺寸,能降低烟气对外廊的影响。     

Smoke detection based on condensed image

Smoke is difficult to detect whether based on static characteristic such as smoke color, texture, etc., or on dynamic characteristics such as frequency, shape or fluttering, etc. Smoke detection are always subject to some significant exceptions, e.g. swinging bags, driving cars in night, fog, and even moving persons. To efficiently detect smoke we condense video and find that smoke trajectories have some special characteristics, such as right-leaning line, smooth streamline, low-frequency, fixed source and vertical–horizontal ratio. Based on these characteristics it is very accurate and fast with little cost to find smoke even in a complex environment. To demonstrate the effectiveness, the proposed method is conducted on various videos, e. g. videos shot by ourselves, videos from Korea CVPR Lab, videos from YouTube, videos from Bilkent University. Experiments show that similar objects often mistaken by other algorithms are differentiated rightly and the ratio of correct detection is promoted to a higher level of 83.0%.     

Study on the real-time size distribution of smoke particles for each fire stage by using a steady-state tube furnace method

For the analysis of the adverse effects of smoke on health, it is essential to determine the amount and location of smoke particles deposited in the respiratory tract. However, the deposition characteristics of the particles are influenced by their morphology and size distribution. Moreover, the real-time particle size distribution during inhalation is important for determining smoke particle deposition in the lungs. Smoke particles generated under different fire conditions differ in their physical and chemical characteristics. Thus, there is a need to adopt international standard methods for characterizing the particles generated in fire. In the present study, the size distributions together with morphology of smoke particles were measured for each fire stage by using the steady-state tube furnace method given in ISO/TS 19700. The size distributions of smoke particles from wood and polypropylene (PP) were measured in real time by using an electric low-pressure impactor (ELPI⁺), and their morphologies were analyzed using transmission electron microscopy (TEM).     

高层建筑防排烟设计探讨

随着我国城市化进程的加快,高层建筑逐渐增多,建筑内部功能趋于综合化、复杂化,在防火方面的要求更高。防排烟作为建筑防火的一项重要措施,对火灾逃生及救援有着极为重要的作用。     

含吹拔空间的高层建筑火灾烟气流动数值模拟

研究设有吹拔空间的高层建筑烟气流动及火灾蔓延特征,分析其对防火分区和安全疏散的影响。采用性能化消防设计的方法对某设有74.65 m、55.95 m双吹拔空间的一类高层建筑建立火灾发展模型、设计火灾场景、用CFD火灾模拟软件进行数值模拟。结果表明该建筑利用吹拔空间自然排烟时各火灾场景均能满足各层人员疏散的性能指标,在吹拔空间四周环廊上设置挡烟垂壁影响烟气的顺畅排出,缩短了危险来临时间,增大了火灾的危害性。提出吹拔空间式建筑宜利用烟囱效应优先采用自然排烟方式,烟气控制宜疏堵结合,以疏导为主的设计理念。     

某地下网吧消防排烟设计

介绍了地下网吧消防排烟系统的设计。消防排烟系统与日常排风系统合用设置,排烟口兼作排风口;消防补风系统与日常送风系统合用设置;平时,排烟系统、补风系统作日常通风换气使用,火灾时,则自动切换为消防排烟方式运行。     

基于烟气湍流效应的火灾判据

烟气是火灾过程的重要物理现象,烟气的湍流效应是火灾图像探测的重要影响因素。本文分析了烟气湍流效应对火灾图像探测的影响,得出了一些烟气湍流效应的图像特征,为多参数特征的火灾探测提供了理论依据。     

A computational study on effects of fire location on smoke movement in a road tunnel

In this work, a numerical model of tunnel fire is developed and aimed to investigate the influence of cross-sectional fire locations on critical velocity and smoke flow characteristic. It is shown that the critical velocity for a fire next to the wall is obviously higher than that for a fire in the middle or on the left/right lane. The ratio is estimated to be 1.12. The predictions of critical velocity from ‘small-fire’ models show a good agreement with that for a fire in the middle or on the left/right lane from CFD. The tunnel height at the fire location is proposed to be instead of the hydraulic tunnel height in the ‘big-fire’ model of Wu and Bakar for a fire next to the wall. The smoke moves backward in a tongue like form as the ventilation velocity is lower than the critical velocity. The back-layering length of a fire in the middle is shown to be approximate twice than that on the left/right lane under the same ventilation velocity, although they share the same critical velocity. Whereas a relatively short back-layering length for a fire next to the wall under the velocity of 2.6 and 2.7 m/s. In addition, a snaky high-temperature profile on the top wall at the initial downstream is observed for a fire on the left lane and next to the wall, and finally a steady and layered smoke flow. The likely cause of this phenomenon is subsequently explained in this study.     

Wind effects on smoke motion and temperature of ventilation-controlled fire in a two-vent compartment

High-rise building fire is often influenced by the ambient wind. Study concerning fire behavior in the compartment of high-rise buildings in wind environment is needed for exploring some effective methods used for evaluation of compartment fire smoke movement and control. In this paper, smoke flowing direction and temperature of ventilation-controlled fire in a two-vent compartment are studied when ambient wind blows to the vent at higher altitude. It is found that there is a critical wind speed, above which the direction of smoke movement is dominated by wind rather than by buoyancy. It is also found that ambient wind has a complex influence on smoke temperature in the compartment. When wind speed exceeds another critical value, only one steady state appears in the smoke temperature rising curve. Otherwise three steady states appear. Heat transfer through the compartment walls has great influence on the second critical wind speed.     

山岭隧道通风排烟设计现场火灾试验

详细介绍某山岭隧道的工程概况以及在隧道内进行的现场火灾试验,参考AS 4391-1999澳大利亚热烟试验标准设计通风排烟试验,并增加了一次全尺寸汽油燃烧试验。通过对隧道内火灾试验时的温度、风速、烟气层高度等进行比较,总结山岭隧道火灾的特点和规律,并为该山岭隧道火灾工况下通风排烟设计方案优化提出建议。     

防排烟系统与空调系统火灾后兼用的模拟研究

本文以某高层建筑的单室空调房间为研究对象，利用计算流体软件PHEONICS，分别对空调系统、排烟系统、兼用系统等空调系统的不同运行工况下单室火灾发展过程进行了数值模拟计算。分析兼用系统对空调房间火灾发展，以及对室内人员疏散产生的影响，从理论上证明兼用系统火灾后在排烟、降温、减压等方面的实用性和可行性。研究结果对于单室火灾后人员疏散和空调、防排烟兼用系统的设计都具有重要的指导意义。     

重庆市发展长江水源热泵的水源概况分析

为了解重庆段长江水作为热泵冷热源的概况,对重庆段长江水温的横断面变化和时间变化进行了实测分析,并对江水的水质和水位变化进行了分析,得到长江水温在整个横断面基本恒定,而江水的夏季月平均温度在22~25℃,冬季月平均温度在11~16℃,水温日变化幅度不超过0.5℃。是一种具有良好品质的稳定的冷热源。而长江水作为水源热泵的冷热源,主要解决的水质问题是泥沙和悬浮物,在三峡库区形成后水位变化可达到30 m,因此取水方式可考虑采用浮船取水方式。