The fire environment in a multi-room building— comparison of predicted and experimental results

This paper outlines results from a research project which is being used to investigate realistic fire environments in a prototype multi-room building. A comprehensive set of experimental data was obtained from a recently constructed three-storey Experimental Building-Fire Facility. The facility is used for a variety of fire investigation purposes, including fire growth and spread, smoke movement, and the effects of stair pressurisation and extinguishment. For the current investigation, a propane burner was located in the centre of a burn room to simulate a fire under both steady-state and transient-state conditions. The burn room was connected to other rooms. A comprehensive set of temperature, radiation and flow velocity measurements was obtained.

The numerical results obtained from a computational fluid dynamics (CFD) model were found to agree well with the experimental results. The CFD model results were also found to agree well with zone model predictions. These results encourage use of the CFD model to research the phenomena of realistic fire growth and spread and smoke movement in prototype building layouts.     

Comparison of FDS Prediction of Smoke Movement in a 10-Storey Building with Experimental Data

In this study, the Fire Dynamics Simulator (FDS), a computational fluid dynamics (CFD) model developed by National Institute of Standards and Technology (NIST) is used to simulate fire tests conducted at the National Research Council of Canada (CNRC). These tests were conducted in an experimental 10-storey tower to generate realistic smoke movement data. A full size FDS model of the tower was developed to predict smoke movement from fires that originate on the second floor. Three propane fire tests were modelled, and predictions of O₂, CO₂ concentrations and temperature on each floor are compared with the experimental data. This paper provides details of the tests, and the numerical modelling, and discusses the comparisons between the model results and the experiments. The 10-storey experimental tower was designed to simulate the centre core of high-rise buildings. It includes a compartment and corridor on each floor, a stair shaft, elevator shaft and service shafts. Three propane fire tests were conducted in 2006 and 2007 to study smoke movement through the stair shaft to the upper floors of the building. The fire was set in the compartment of the 2nd floor. Thermocouples and gas analyzers were placed on each floor to measure temperature and O₂, CO₂ and CO concentrations. Comparisons in the fire compartment and floor of fire show that the FDS model gives a good prediction of temperature and O₂ and CO₂ concentrations. In the stair shaft and upper floors there are some small differences which are due to the effect of heat transfer to the stairs that was not considered in the model. Overall the study demonstrates that FDS is capable of modelling fire development and smoke movement in a high rise building for well ventilated fires.     

Research on smoke control in underground structures

The purpose of the research described in this paper is to test smoke movement, to study the efficiency of smoke control by air control around the fire origin, and to determine control methods to protect evacuation zones from smoke. The four steps required to accomplish these aims are: (1) construction of mathematical models that describe the horizontal movement of smoke, the propagation velocity and heat loss of smoke; (2) a comparison between the mathematical models and full-size and scale models of an underground corridor; (3) a comparison between different ventilation systems and positions of fire origin in a scale model of an underground structure; and (4) simulation of the smoke movement of the underground structure using a one-layer zone model. A simulation model for evaluating the safety of underground structures is also proposed.     

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.     

A numerical study of atrium fires using deterministic models

The smoke filling process for the three types of atrium space containing a fire source are simulated using the two types of deterministic fire model; zone model and field model. The zone model used in this simulation is CFAST (Version 3.1) developed at the Building and Fire Research Laboratories, NIST in the USA. The field model is a self-developed CFD model based on full consideration of the compressibility and k–ε modeling for the turbulence. This article is focused on finding out the smoke movement and temperature distribution in atrium spaces. A computational procedure for predicting velocity and temperature distribution in fire-induced flow is based on the solution of three-dimensional Navier–Stokes conservation equations for mass, momentum, energy, species etc. using a finite volume method and non-staggered grid system. Since air is entrained from the bottom of the plume, total mass flow in the plume continuously increases. Also, the ceiling jet continuously decreases in temperature, smoke concentration and velocity; and increase in thickness with increasing radius. The fire models, i.e. zone models and field models, predicted similar results for the smoke layer temperature and the smoke layer interface heights. This is important in fire safety, and it can be considered that the required safe egress time in three types of atrium used, in this paper is about 5 min.     

浅谈多层及高层建筑室内消火栓的布置

本文从住宅内、住宅底层小商业区、高层住宅的防烟楼梯间、双阀双出口和消防箱内消防卷盘的消火栓布置,以及消火栓在防火分区中的设置等方面介绍了多层及高层建筑室内消火栓的合理布置,以供参考。     

Using Sensor Signals to Analyze Fires

Building fire sensors are capable of supplying substantially more information to the fire service than just the simple detection of a possible fire. Nelson, in 1984, recognized the importance of tying all the building sensors to a smart fire panel [1]. In order to accomplish a smart fire panel configuration such as envisioned by Nelson, algorithms must be developed that convert the analog/digital signals received from sensors to the heat release rate (HRR) of the fire. Once the HRR of the fire is known, a multiroom zone fire model can be used to determine smoke layers and temperatures in the other rooms of the building. This information can then be sent to the fire service providing it with an approximate overview of the fire scenario in the building.This paper will describe a ceiling jet algorithm that is being developed to predict the heat release rate (HRR) of a fire using signals from smoke and gas sensors. The prediction of this algorithm will be compared with experiments. In addition, an example of the predictions from a sensor-driven fire model, SDFM, using signals from heat sensors, will be compared with measurements from a full-scale, two-story, flashover townhouse fire.     

火灾烟气毒性评价新的"RRC"动态模型及工程应用

就火灾中的死亡人数而言，最主要的威胁来自于火灾中的烟气。目前已经有很多种模型来描述火灾中的烟气毒性危害，如CO随机模型、FED、FEC和N气体模型。所有这些模型都不能反应真实火灾中烟气浓度的时空变化。根据真实火灾中的烟气危害度，选取人员的呼吸率、人员在火灾中的逃生路径、特定建筑中的烟气浓度场分布等三个对于人员致死具有决定性的因素，初步建立一个新的“RRC”动态模型来描述火灾中的烟气毒性危害，并通过算例展示了模型的工程应用。     

居民自建房楼梯-走道组合结构火灾烟气运动

采用大涡模拟技术对居民自建房楼梯-走道组合结构中的火灾烟气运动规律进行数值模拟。通过对烟气及速度矢量场的分析发现,火灾烟气在建筑内的流动可以分为5个不同的阶段。通过对FDS源程序进行改进,提取烟气粒子的位置随时间变化的信息,得到烟气粒子的拉格朗日运动轨迹,展示烟气的几种典型运动形式。烟气在进入走道后最初的环形运动多是贴近壁面的,而后环形轨道路径越来越远离壁面靠近中心部位,环形轨迹的路径也越来越小。     

模型车厢内火灾烟气层运动模拟分析

旅客列车车厢内发生火灾时，火灾烟气的运动状况直接影响旅客的人身安全，往往造成重大的人员伤亡和巨大的财产损失。采用模型实验、数值模拟的方法对运行的旅客列车经过隧道发生火灾时车厢内烟气层高度的特征进行了研究，将旅客列车卧铺车厢处理为多个受限空间的组合，研究了车厢内烟气层高度在开口不同状况下的变化规律。模型实验与数值模拟相结合为列车车厢火灾研究提供了理论分析模型和实验研究方法，研究成果为车厢防火设计提供了重要的技术依据。     

住宅建筑内火灾高温烟气流动数学模型

以住宅建筑火灾安全为研究背景,根据多室实体住宅建筑模型室内火灾升温及高温烟气流动影响的试验结果,重点讨论了起火房间尺寸、门洞尺寸及枢纽空间等3个主要空间构造因素对室内高温烟气流动影响。以质量守恒等相关热力学和流体力学基本概念建立了住宅空间单室尺寸与高温烟气分布的几何关系模型;利用动量守恒控制体法建立了开敞空间的开口尺寸与烟气扩散的关系模型。分析表明,住宅建筑火灾安全应充分考虑空间构造形式的影响;通过对烟气流动模式的独立房间尺寸设计和房间连通形式设计,可以有效地控制室内温度分布和烟气流动路径。     

Full-scale experiment research and theoretical study for fires in tunnels with roof openings

In order to assess the possibility of exhausting smoke through passive roof openings and the influence of smoke on personnel in the tunnels, full-scale fire experiments in tunnels with roof openings are carried out, which were rarely reported in the previous references. The data of smoke propagation, smoke sedimentation, velocity field and temperature field are measured. On the basis of the smoke longitudinal propagation laws, the prediction model of calculating backlayering distance is built. The Kurioka model and the built mathematical models are validated by those experiments. All the experimental data presented in this paper can be further applied for verification of numerical models, and bench-scale experimental results. Those full-scale experimental results and theoretical analysis can also be used for directing tunnel fire research, which afforded scientific gist for fire protection and construction of road tunnel with roof openings.     

The ASHRAE design manual for smoke control

For many years smoke has been recognized as a major killer in fire situations. In response to this problem, the concept of controlling smoke movement in building fires has developed. The American Society of Heating, Refrigeration, and Air-Conditioning Engineers and the U.S. Veterans Administration have sponsored a design manual for smoke control systems. This paper provides an overview of this manual with emphasis on the principles of smoke control, stairwell pressurization, zone smoke control, computer analysis, and acceptance testing.     

Simulation of tunnel fires using a zone model

The use of a fire zone model for simulating tunnel fires is reported in this paper. The zone model CFAST version 2.0 was selected as the fire simulator. Numerical experiments were performed in an arbitrary tunnel by considering it as a single compartment, a two-room structure and a three-room structure. Five fires that would have a high likelihood of occurring in a tunnel were considered. They were caused by burning wood cribs, a passenger train, a subway coach, a truck, and a school bus. Results are also compared with another zone model, CCFM.VENTS, and those predicted from a self-developed fire field model for studying the aerodynamic and smoke movement in a tunnel. Further, experimental data collected in a smaller tunnel from an abandoned copper mine in Norway was used to justify the prediction.     

住宅建筑内火灾高温烟气流动规律试验研究

以住宅建筑火灾安全为研究背景,利用多室多层住宅建筑缩比模型,进行了空间构造形式对室内火灾升温及高温烟气流动影响的试验研究.重点考察了不同火源点情况下,各房间内部的升温模式和温度分布,间接分析了高温烟气流动的规律.试验结果表明,住宅建筑的枢纽空间构造形式、房间门上方垂壁及各房间的相对位置对室内高温烟气的流动具有较大的影响.室门上方垂壁能够有效阻止高温烟气的扩散,室内外温差要高于无垂壁房间;非起火房间的室门开启方向与起火房间相对时,高温烟气的进入量要高于两者开口同向或平行情况.     

地铁过江隧道事故通风系统对火灾的影响研究

以某城市地铁过江隧道火灾为例,采用地铁环境模拟软件,计算和分析列车不同着火部位及隧道事故通风系统启动时间对火灾高温烟气分布的影响。结果表明,列车活塞风由于惯性作用将对火灾高温烟气控制产生一定的影响。车头着火时,列车活塞风有利于控制烟气回流,隧道事故通风系统启动越快有利于控制车头烟气温度的升高;车尾着火时,活塞风对控制火灾烟气向车头蔓延产生不利影响,事故通风系统立即启动使车尾烟气温度快速达到最高,可能产生轰燃现象,事故通风系统推迟启动使高温烟气快速向车头方向扩散,不利于人员逃生。建议加强列车车尾自身的消防灭火装置,提高人员灭火救援的自救意识。     

性能化防火设计中人员疏散问题安全性的一种评估方法

提出了一种在性能化防火设计中人员疏散问题安全性的评估方法，该方法是把火灾烟气运动规律、建筑物结构和人员疏散特点结合的研究成果，分别计算建筑物中不同单元内的火灾荷载阚值，在发生火灾时，烟气达到危险状态的时间和人员疏散所用的时间，比较这两个时间来确定建筑物防火设计是否达到性能化防火中人员安全疏散的要求。该方法从控制建筑物内火灾荷载的多少和建筑物的结构出发，在现行的计算软件的基础上．可用于实际的火灾安全工程设计和火灾安全咨询。     

浅谈大空间火灾烟气运动规律的计算机模拟

分析并讨论了当前大尺度空间火灾烟气运动规律的计算机模拟研究现状。结果表明,采用大涡模拟方法结合多单元区域模拟是研究火灾烟气运动规律的发展趋势。