An Experimental Study of Smoke Movement in Multi-Storey Buildings

This paper presents the results of an experimental study of smoke movement in a 10-storey building. Eight full-scale experiments including four real fuel fires and four propane fires were conducted in the National Research Council Canada (NRCC)’s 10-storey experimental tower to generate smoke movement data that can be used for the validation of computer models. The heat release rate (HRR) of fire cannot be measured in this tower, so to estimate the HRR of fuel-package fires in this study, an approach using propane as a fuel was developed to reproduce the temperature distribution of various fuel-package tests.     

The Impact of a Change on the Size of the Smoke Compartment in the Evacuation of Health Care Facilities

Evacuation in health-care facilities is complex due to the physical impairment of the patients. This kind of evacuation usually requires the assistance of the workforce members. A proposed change of NFPA 101, Life Safety Code, would increase the maximum allowable size of a smoke compartment (a space within the building enclosed by smoke barriers on all sides that restricts the movement of smoke) in health-care occupancies from 2090 m² to 3700 m², almost double the size. This study aims to analyse the impact of this change in the required time for evacuating patients during a fire in order to understand the consequences of that potential change. This paper is focused on the area where the patient’s rooms are located. The evacuation scenario is a floor plan comprised of four smoke compartments. To analyse the proposed change, the smoke barriers between two adjacent compartments were removed in a floor plan and three ratios of number of patients per one staff member were considered (4:1, 3:1 and 2:1). A computational methodology was conducted to calibrate the model STEPS for simulating assisted evacuation processes. In addition, Fire Dynamic Simulator (FDS) was used to simulate the fire and smoke spread in a table and a PC to compare fire and evacuation results The evacuation results show that the change of the smoke compartment size increases the mean evacuation time by 23%; however, the fire results show that the available safe egress time is 16 min for both smaller and large smoke compartment. The ratio of the number of patients per staff member is also a strong factor that increases the evacuation up to 82% when comparing the ratios of 2 patients per staff member and 4 patients per staff member.     

夏季环境温度对地铁火灾烟气的影响

以地铁火灾与烟气发展过程的数学模型为基础,建立FDS模拟的物理模型,对双层岛式无屏蔽门的地铁车站站台在夏季的情况进行火灾数值模拟。模拟中选取主要楼梯出口对烟气、温度和能见度进行描述,记录相关参数变化情况,得出CO体积分数、温度、能见度的变化规律,为烟气扩散的有效控制提供理论依据。     

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.     

Wind tunnel tests on compartment fires with crossflow ventilation

When a fire occurs in a room at ground level or a compartment located in the higher floors of a very tall building , the strong ambient wind will play an important role in fire spreading and smoke movement behavior. However, wind effect on compartment fire in cross ventilation condition has not been fully studied so far. In the present study, an effort has been made to study the wind effect on compartment fire in cross ventilation condition through experimental investigations. The experimental fire was generated by 250 ml n-heptane on the floor center of a cube enclosure with two opposite vents on the walls. The inside and outside gas temperature profiles at different vertical and horizontal locations were recorded by two thermocouple matrixes. The ambient wind velocity was set to 0, 1.5 and 3 m s⁻¹. It is observed that the ambient wind would enhance the fire severity by increasing the compartment fire temperature and reducing the time to flashover. The spilled-out flame/plume would extend horizontally farther with the increase of wind speed. Simple theoretical analysis shows that there is a critical wind velocity, or a dimensional number, to differentiate whether the gas flow across the vents is bidirectional or unidirectional, which is believed to influence enclosure fire behavior greatly.     

室内烟气运动影响因素模拟研究

运用FDS模拟室内火灾烟气的运动规律,分析烟气层稳定性,以及门的尺寸、火源位置和火源面积对烟气温度及高度的影响。结果表明,具有稳定热释放速率的火源,燃烧一段时间后烟气层高度不会随时间发生变化;烟气层高度随门的高度和宽度增加而升高;火源处于房间中心时,烟气层高度随着门宽度增加迅速升高,与门高度的关系较小;随着火源面积增加,烟气层高度下降,温度升高。     

创意概念型博览会展建筑消防性能化设计

结合某创意概念型博览会展建筑工程,针对其防火分区面积大、疏散距离长的问题进行性能化防火设计。设计7个场景,以FDS模拟烟气流动,使用EVACNET4模拟人员疏散情况。就此类建筑性能化设计中若干关键问题进行探讨。性能化设计的防火分区应与按规范要求设计的防火分区在安全性上等价或相似。应增强防排烟以弥补疏散距离长的缺陷。应考虑增配消防排烟车以增强应急救援能力。     

Assessment of the Use of Fire Dynamics Simulator in Performance-Based Design

This paper discusses a procedure for the use of fire modelling in the performance-based design environment to quantify design fires for commercial buildings. This procedure includes building surveys, medium-and full-scale experiments and computer modelling. In this study, a survey of commercial premises was conducted to determine fire loads and types of combustibles present in these buildings. Statistical data from the literature were analysed to determine the frequency of fires, ignition sources, and locations relevant to these premises. Based on the results of the survey and the statistical analyses a number of fuel packages were designed that represent fire loads and combustible materials in commercial buildings. The fuel packages were used to perform medium- and full-scale, post-flashover fire tests to collect data on heat release rates, compartment temperatures and production and concentration of toxic gases. Based on the experimental results, input data files for the computational model, Fire Dynamics Simulator (FDS), were developed to simulate the burning characteristics of the fuel packages observed in the experiments. Comparative analysis between FDS model predictions and experimental data of HRR, carbon monoxide (CO), and carbon dioxide (CO₂), indicated that FDS model was able to predict the HRR, temperature profile in the burn room, and the total production of CO and CO₂ for medium- and large-scale experiments as well as real size stores.     

耦合电梯门狭缝流动的高层竖井火灾烟气模拟

利用FDS 建立17 层高层办公楼数值模型,考虑狭缝的小开口流动,耦合了基于开口流动理论的HVAC 模型,研究高层建筑内烟气通过电梯竖井的蔓延过程,得到了高层建筑内烟囱效应诱导的火灾烟气蔓延规律。高层建筑内较低层发生的火灾会显著加热电梯竖井中的气体,形成烟囱效应,高层建筑内部会形成中性面。通过将HVAC 模型与基于标准流量系数的模型进行比较,可以发现这两种方法计算的质量流量相差约1.5 倍。这是由于采用的HVAC 模型并没有考虑狭缝处的开口流动损失。通过进一步修正,取开口损失系数K 值为3.56 能得到较好的模拟结果。     

Simulation of temperature and smoke distribution of a tunnel fire based on modifications of multi-layer zone model

Some modifications on Suzuki’s multi-layer zone model (MLZ) have been done to predict temperature and smoke distribution of a tunnel fires, i.e., the radiation heat loss of fire source is taken into account and a four-surface radiation heat transfer model is introduced. Like Suzuki’s model, as a special long and narrow space, the tunnel space is also divided into a number of layers in vertical direction and regions in longitudinal direction. The physical properties like temperature and species (CO, CO₂, etc.) are assumed uniform in every zone like two-zone model. However, the different heat transfer model is introduced. The MLZ model prediction is compared with the experiments of USTC and CFD model (FDS). It shows good agreement between the model prediction, experiments and CFD models (FDS). And the MLZ model needs less time than CFD model.     

空气幕对列车车厢火灾烟气的影响规律研究

为研究防烟空气幕对列车车厢火灾烟气的影响规律,建立了CRH2A动车组一节车厢的内部模型,利用FDS模拟软件对列车车厢火灾时期的烟气流动规律进行数值模拟.依据给定火灾场景下烟气水平运动速度设置空气幕水平切向速度,通过改变空气幕安装角度,研究车厢内部火灾时,在空气幕作用下车厢空间各区域烟气层高度的变化,温度及CO浓度的分布...     

新疆国际会展中心消防安全性能化评估

针对新建新疆国际会展中心防火分区面积过大、疏散宽度不足、疏散距离过长等设计问题,提出设置防火隔离带、亚安全区等措施的消防设计方案,设计6个火灾场景模拟分析消防设计的安全性.以FDS模拟烟气流动状况,比较可用疏散时间和必需疏散时间.模拟分析结果表明其消防设计能够满足安全性要求.     

Determinations of the fire smoke layer height in a naturally ventilated room

According to the case-based reasoning of natural ventilation designs in recommended Green Buildings, an investigated model space was proposed in this study. FDS simulations and full-scale experiments were carried out to measure the impact of natural ventilation conditions and the installation of a natural ventilation shaft on smoke layer descent during different fire scenarios. The feasibility of using the N-percentage rule to determine the fire smoke layer height in a naturally ventilated space was also investigated.In a non-fire room, the smoke descent curve determined from the FDS simulated temperatures is consistent with the experimentally measured temperatures and visual observation of the smoke layer. However, the thermocouples in the fire room are affected by direct burning and fire radiation, and the experimentally measured temperatures cannot be used to determine the smoke height. Under these conditions, FDS simulations can be used to compensate for the lack of experimental measurements. In fire scenarios without outdoor winds blowing into the building's interior, FDS simulations can reliably model the fire smoke layer height. When outdoor air blows into the interior, it causes the smoke layer temperature to become unstable. Thus, the temperature will not be thermally stratified, and the use of the N-percentage rule is not recommended.     

Species Transport from Post-Flashover Fires

A study was performed to determine the use of an equivalence ratio to predict gas levels (CO, CO₂, O₂, and unburned hydrocarbons) transported to locations remote from a post-flashover compartment fire. A series of tests were conducted in a reduced-scale facility to measure the evolution of post-flashover compartment fire gases flowing down a hallway. Test variables included air entrainment into gases in the hallway, stoichiometry of the compartment fire gases entering the hallway, mass flow rate of compartment fire gases, and the presence of a vitiated smoke layer accumulated in the hallway. In cases with no layer accumulated in the hallway, species yields in the hallway were found to correlate with a control volume equivalence ratio. The control volume equivalence ratio is the ratio of the mass loss rate of fuel inside the compartment to the air flow into the compartment plus the air entrained into compartment fire gases flowing along the hallway. Layers that accumulate in the hallway were determined to limit oxidation, which in some cases resulted in CO yields transported to remote locations being 20% higher than those inside the compartment. Based on the experimental data, a methodology was developed for predicting species levels transported to remote locations.     

室外风对高层建筑竖井内烟气运动影响的数值模拟

采用火灾模拟专业软件FDS对不同火源位置、不同风向条件下火灾烟气的运动进行模拟,测定典型位置处温度、速度、CO及CO2体积分数变化情况。实验结果表明:在近地风场中,风向对竖井内烟气蔓延的影响大小顺序为迎风>背风>侧风,竖井开口位于迎风面时,外界风对竖井内烟气运动影响最大:火源位于中性面以上时,烟气通过竖井与前室的开口向竖井内蔓延,并向下运动;而火源位于中性面以下时,前室内烟气向外部运动,竖井内无烟气流入。     

室内火灾危险性分析

利用FDS软件模拟火源在室内不同位置处火灾的危险性,分析火源在不同位置时室内烟气层的温度、氧气体积分数及烟气层高度的变化规律。模拟结果表明:火源在门开口径向方向时,室内1.5 m高度以下空间的烟气层温度较高,氧气体积分数较低,而1.5 m以上情况相反;火源位置距离开口越近,烟气层高度越低,危险性越大。     

Scale Tests of Smoke Filling in Large Atria

The large Atriums of airports and railway stations facilitate the access to transport vehicles including shopping malls, cultural spaces, etc. For this reason, they are used by an elevated number of passengers and visitors. Numerous malls contain a large atrium too, as a principal access or as a food court, and they usually have high occupant loads. In case of fire, the smoke can affect human health seriously, and people may be unable to reach a safe place before being overcome by the conditions created by the fire. The traditional approach to fire protection by compartmentation is not applicable to these large volume spaces and the ability of sprinklers to suppress fire in spaces with high ceilings is limited. This work evaluated—using scale tests, fire computer modeling and analytical methods—a comparative analysis of the different results obtained for the smoke control in large atria when the smoke filling approach is applied. Smoke layer and plume temperatures have been registered during the scale test—based on the Froude Modeling—and they have been compared opposite to the FDS scale simulation and the FDS large scale simulation. Smoke layer descend has been studied and compared for the scale test, the computer simulations developed and the empirical equations used. The results demonstrated that the evacuation time calculation is conservative when the zone computer model CFAST, the field computer model FDS or the empirical equations are used, although it turns out to be difficult to define the interface height based on the temperatures registered during the scale tests. The zone computer models generate results faster than field computer models or smoke tests, so it would be necessary to develop better calculation algorithms to define the smoke layer interface.

烟囱效应下山岭隧道火风压特性模拟研究

为探究山岭隧道火灾模式下竖井内火风压的变化特性,采用数值模拟方法,选取火灾发生在竖井附近及远离竖井时的烟气流动特性为研究对象,分析烟气在纵向通风作用下竖井内火风压的变化规律。研究表明：与传统斜坡隧道火灾不同,由于烟气涡流影响,竖井内火风压在纵向通风作用下均呈现非单调的变化趋势,故隧道火风压理论模型不能直接用于竖井内火风压预测;竖井内火风压随纵向风速从0 m/s 增大至3.5 m/s 时呈现逐渐增加趋势,最大差值约为40 Pa;火源靠近竖井时比远离竖井时,竖井内火风压更大,纵向无风时,两者最大差值约为25 Pa。     

地暖对单层大空间火灾烟气运动的影响

为研究地暖采暖对单层大空间火灾烟气上升过程的影响,设计建立了小规模实验装置进行实验,并利用FDS 软件模拟实验工况,通过对比实验值和模拟值证实了FDS 软件模拟的可靠性。利用FDS 软件,对真实采暖单层大空间的火灾烟气上升规律进行数值模拟,提出该环境中影响烟气运动的主要因素及控制措施。研究结果表明：地暖采暖环境中的火灾烟气处于不稳定状态;在地暖采暖空间中,烟气上升和顶棚射流的速度都将有所提高,从而总体加速了烟气的发展进度。     

某商业综合体室内步行街消防设计数值模拟

以某商业综合体为例,使用FDS进行三维数值模拟,研究商业综合体内部发生火灾时烟气运动规律。模拟中庭发生火灾的两个火灾场景,考察首层步行街作为人员疏散准安全区的可行性。结果表明:步行街满足准安全区的要求;人员可用安全疏散时间主要受能见度影响;火灾不会通过热辐射的方式蔓延;机械排烟失效造成的危害比自动灭火失效严重。建议加强管理,室内步行街回廊设置排烟系统。