Development of a hybrid field and zone model for fire smoke propagation simulation in buildings

A novel hybrid fire model combining the traditional field and zone modeling approaches to simulate the fire smoke propagation in a multi-storey building is presented in this paper. In the hybrid model, the field model is used to model the fire smoke movement in rooms with complex fire-induced airflow where the two-layer zone assumption of the zone model is not valid, e.g. in the room of fire origin. The zone model is used to model the fire smoke propagation in the rooms/corridors where the hot smoke layer is well stratified and the smoke movement can be reasonably simulated based on the two-zone concept. The fundamentals of the hybrid fire model are presented and discussed in this paper. The interface treatment between the field model and the zone model is presented in detail. In addition, some examples highlighting the application of the new hybrid model to simulate the smoke propagation in a multi-storey building are also presented. The hybrid model provides a more accurate prediction of fire smoke propagation and consumes less computational resources in comparison to the full zone and full field models, respectively.     

农村地区火灾荷载调查初步研究

对黑龙江、内蒙古、河南、江西、山东五省市部分农村进行了小范围的火灾荷载的调查统计分析，计算了卧室、客厅、厨房、杂物房等房间的火灾荷载密度，然后利用算术平均值的方法计算了室内平均火灾荷载密度，并分析了影响各个房间火灾荷载密度大小的因素，这些数据将为以后广大农村地区火灾研究及性能化设计奠定了基础。     

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.     

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.     

A comparison of a FLOW3D based fire field model with experimental room fire data

This paper describes the application of a fire field model based on the FLOW3D CFD software to the simulation of fire induced flows in domestic sized rooms. Several scenarios are examined consisting of various sized fires, fire locations and door sizes. Comparisons are based on upper-layer room temperatures, mass fluxes in and out of the fire compartment and door-way vertical and horizontal temperature and velocity profiles. For most cases the model agrees reasonably well with the observed trends, however the results suggest that significant mesh refinement is required to produce results in quantitative agreement with experimental results. A close examination of the horizontal door-way velocity profiles highlights the need for careful modelling and experimental practices in this region.     

腔室火灾烟气向远距离房间的传播迁移

利用数值模拟方法研究了腔室火灾产生的烟气通过毗邻的走廊向远距离目标房间传播迁移的规律。结果表明,烟气到达走廊弯处远距离目标房间的时间接近或少于到达某些中间位置房间的时间,有些远距离目标房间中烟气的下降时间反而短。这就解释了遇难者大量死于远距离处的主要原因。     

Mapping areas at elevated risk of large-scale structure loss using Monte Carlo simulation and wildland fire modeling

This work presents, and demonstrates through application to California, a data-driven methodology that can be used to identify areas at elevated risk of experiencing wildland fires capable of causing large-scale structure loss. A 2D Eulerian level set fire spread model is used as the computational engine for Monte Carlo simulation with ignition points placed randomly across the landscape. For each randomly-placed ignition point, wind and weather conditions are also selected randomly from a 10-year climatology that has been developed by others using the Weather Research and Forecasting (WRF) mesoscale weather model at a resolution of 2 km. Fuel and topography inputs are obtained from LANDFIRE. Housing density is estimated from 2010 Census block data. For each randomly-selected combination of ignition location and wind/weather, fire progression is modeled so that fire area and number of impacted structures can be recorded. This is repeated for over 100 million discrete ignition points across California to generate “heat maps” of fire probability, fire consequence, and fire risk. In this work, fire volume (spatial integral of burned area and flame length) is used as a proxy for fire probability since quickly spreading fires with large flame lengths are most likely to escape initial attack and become extended attack fires. Fire consequence is taken as the number of impacted structures. Fire risk is then estimated as the product of probability and consequence. The methodology is assessed comparing the resultant fire risk raster with perimeters from California's 20 most damaging fires as tabulated by the California Department of Forestry and Fire Protection (CALFIRE). It is found that these historical perimeters from damaging fires correlate well with areas identified as high risk in the Monte Carlo simulation, suggesting that this methodology may be capable of identifying areas where similarly damaging fires may occur in the future.     

Numerical assessment of hazard in compartmental fire having steady heat release rate from the source

The fire ignited due to air conditioner (A/C) malfunctioning is studied numerically for a single room, two rooms with interconnection, two interconnected rooms with attached corridor and a two-storeyed building with stairs. Coupled finite difference and finite volume based open source solver, Fire Dynamics Simulator (FDS) is used for domain discretization and solution of governing equations. Heat release rate per unit area (HRRPUA) is varied in the single room case and temperature and visibility contours are studied to determine HRRPUA corresponding to maximum hazard, judged based on available safe evacuation time (ASET) calculation. Further, positions of air conditioners, at a prescribed HRRPUA, are varied in two interconnected rooms to obtain the case with maximum ASET. Evacuation strategy is discussed and the maximum number of persons who can be safely evacuated from the accident site is calculated followed by the variation in the position of doors in the case with inter-connected doors attached with a corridor. Soot flow pattern and flame contours are also observed for each of the above cases. At the end, fire breakout is simulated in a two-storeyed building with stairs and having the room configuration based on the maximum ASET value.     

锅炉房设计中某些安全问题的讨论

文章结合有关“防火规范”、“监察规程”要求,针对民用建筑物供热(空调)用锅炉房(包括直燃型溴化锂吸收式冷热水机机房)设计中常见的有关防火等安全问题进行分析讨论,并对提高设计的安全性提出观点。     

锅炉房设计中某些安全问题的讨论

文章结合有关“防火规范”、“监察规程”要求，针对民用建筑物供热(空调)用锅炉房(包括直燃型溴化锂吸收式冷热水机机房)设计中常见的有关防火等安全问题进行分析讨论，并对提高设计的安全性提出现点。     

更正说明

室内火灾具有较高的危险性,是建筑火灾造成人员伤亡和财产重大损失的灾害之首。利用计算流体动力学(CFD)的方法,建立了室内火灾时期烟气流动的三维大涡数值模型,目的是通过对火灾烟气流动的数值模拟,为多室火灾的控制和人员救助提供理论基础。模拟结果认为,火灾及附近地区温度较高,烟流浓度较大,高温引燃其他易燃物品的可能性加大。通风与火灾的发展状态存在密切关系,通风既能降低室内温度,加快烟流及有毒有害气体的扩散速度,同时也为火灾的进一步发展提供条件。从模拟结果与实验验证可得出结论:火源功率大小及房屋的几何尺寸影响着火灾程度、温度及烟流浓度的分布和变化,数值计算的结果总体上与实测结果存在较好的一致性。     

Firefighter Wayfinding in Dark Environments Monitored by RFID

A building on fire is a smoky and dark environment both for firefighters and for civilians trapped inside. The faster firefighters find a way to search for and rescue civilians at a fire scene, the higher the survival rate of those trapped inside. This study presents a discussion on the characteristics of firefighter wayfinding under low visibility. The firefighters who participated in this study underwent testing at a training ground. The participants’ search and wayfinding paths were recorded using radiofrequency identification (RFID) technology. The results revealed that the mean searching time in each room decreased from 135 to 19 s as the firefighters became increasingly familiarized with the task. As expected, data also shows that smaller rooms contributed to shorter searching times. Most participants could manage a maximum of three rooms, with wayfinding confusion manifested after they had searched through the third room. These findings are crucial for the design of fireground strategies and training.     

Fire Performance of Sandwich Panels in a Modified ISO 13784-1 Small Room Test: The Influence of Increased Fire Load for Different Insulation Materials

Four sandwich panel rooms were constructed as prescribed in the ISO 13784-1 test. However, the construction followed normal industry practice, and the panels were also subjected to the kinds of damage typically found in commercial premises, although such damage may not typically be concentrated in such a small room. The fire load was increased to simulate fires actually occurring in commercial premises by stepping up the propane burner output from the usual maximum of 300–600 kW, and by placing a substantial wooden crib in two of the rooms. The results showed significant differences in fire growth rate and burning behaviour between those panels filled with polyisocyanurate (PIR) and those filled with stone wool in both the experiments without and with the wooden crib. Most significantly, the PIR pyrolysis products caused earlier ignition (by radiation from above) of the wooden crib 11 min into the experiment (1 min after the burner was stepped up to 300 kW), whereas the crib ignited 22 min into the test (2 min after the burner had been stepped up to 600 kW, which is beyond the test standard both in time and heat input) for the stone wool panels. This interaction between building and contents is most often ignored in fire safety assessments. After a few minutes, the PIR pyrolysis products that escaped outside the room, from between the panels, ignited. The extra thermal exposure from the PIR-fuelled flames distorted the panels, which in turn exposed more PIR, resulting in large flames on both the inside and outside of the enclosure. From a fire safety perspective this is most important as it shows that with the large fire loads that are commonly found in commercial premises, steel-faced PIR filled panels are not capable of acting as fire barriers, and may support flame spread through compartment walls and ceilings. In addition, the PIR panelled rooms produced very large quantities of dense smoke and toxic effluents, whereas the stone wool panelled rooms produced small amounts of light smoke of lower toxicity. Furthermore, the experiments showed that modifications to the standard test can lead to extremely different outcomes for some of the products. As the modifications simulated real-life situations, it seems important to discuss whether the standard is robust enough for property safety scenarios encountered in industrial premises.     

某机场新建航站楼防火设计方案研究

总结某机场新建航站楼防火设计在防火分隔、疏散方面存在的难点,提出通过限制有可燃物的房间的面积、将可燃物集中的房间与航站楼其他区域进行分隔等措施,达到与划分防火分区等效的目的。国际、国内行李提取厅在不违背航空安全管理的前提下分别在防火墙上增设通往迎客大厅的甲级防火门作为疏散出口。设计火灾场景及疏散场景对方案进行分析评价,结果表明,针对该航站楼所确定的防火设计调整方案可保证建筑的消防安全。     

喷淋保护有效及失效情况下玻璃幕墙层间防火对比试验研究

采用装配式钢结构框架搭建6 层幕墙防火测试平台,考虑喷淋保护有效及失效等多种工况,对玻璃幕墙层间防火系统开展实体火灾试验研究。结果表明,在未安装喷淋系统喷淋失效试验工况中,着火房间的幕墙外侧中空夹胶玻璃在20～23 min陆续破裂脱落,着火上层幕墙玻璃外侧下沿的最高温度约700 ℃,高温导致上层房间幕墙外侧的双层夹胶半钢化玻璃出现裂缝,但未出现整体破裂或脱落。着火上层室内未出现明显过火及高温烟气窜入,说明层间防火构造可有效防止火灾沿幕墙与楼板的结合处向上蔓延。在距幕墙水平距离0.9 m 位置设下垂型喷头,在自动喷水灭火系统自动或手动开启的2 种工况条件下,均可对幕墙周围的火源进行有效抑制,并对幕墙玻璃和铝合金框架提供保护。着火房间内的幕墙玻璃未完全破裂脱落,火势不会蔓延至着火房间上层。     

Modeling of fire spread through probabilistic networks

The postflashover fire spread from room to room is treated in a stochastic analysis beginning with the development of a probabilistic network, and followed by a method of solving the network for discrete probability distributions. The first step in this analysis is the construction of a graph representing a space in which the rooms are nodes, and the walls and other fire barriers are links between the nodes. The space network graph is then transformed into a probabilistic network by introducing one node for representing the preflashover state and another node for representing the postflashover state of each room with the link between them representing the probability of flashover and the time characteristic to flashover. Each link between a flashed-over room and an adjacent space has a probability of the barrier being breached and a characteristic time of fire resistance. The probabilistic network is then solved by creating an “equivalent network” which has multiple links between the nodes to represent the uncertainty intrinsic to fire spread. For instance, a door may be open or closed. This would be represented by two links, one with the probability of the door being open with a characteristic time of zero, and the other with the probability of the door being closed with the time associated with the fire resistance of the door. The analysis of the possible flow through equivalent networks is discussed and the probability of a source node connecting with the sink node as well as the expected shortest travel time are calculated. Finally a numerical example is solved in which the source node is the room of origin of a fire, and the sink node is a section of the corridor which is critical to the escape of the occupants in nearby rooms Two cases are developed, one with “5-minute” doors and the other with “20-minute” doors and automatic closures. A different fire scenario is shown to be represented by each path through the equivalent network, and the probability and characteristic time for each of these scenarios is also calculated. The consequence of the changing to a 20-minute door is presented in quantitative terms and the probability of the door being open is used as a sensitivity parameter.     

Smoke filling time for a room due to a small fire: The effect of ceiling height to floor width aspect ratio

We consider the filling of a room with smoke from a small, centrally located floor fire. We present theoretical arguments for the behaviour of the filling time relative to the idealised ‘filling box time’ [Baines WD, Turner JS. Turbulent buoyant convection from a source in a confined region. J Fluid Mech 1969;37:51–80] as a function of the room height to width aspect ratio. Initially, the rate at which the smoke layer deepens is shown to be more rapid for relatively wide rooms (large aspect ratio). However, at larger times, relatively tall rooms (small aspect ratio) fill more rapidly due to large scale overturning and engulfing of ambient fluid. A series of experiments were performed to verify these results and showed good qualitative agreement with our theoretical predictions. The experiments were also used to evaluate the extent of deviation of the actual smoke front position from the idealised filling box model as a function of the aspect ratio.     

Assessment of the Fire Dynamics Simulator for Modeling Fire Suppression in Engine Rooms of Ships with Low-Pressure Water Mist

Water mist-based fire-extinguishing systems are gaining acceptance for the protection of ship machinery spaces. The use of simulation tools presents a great potential for taking a performance-based design (PBD) approach to these fire scenarios. The Fire Dynamics Simulator (FDS) is the most frequently used and validated fire modeling software; however, studies of low-pressure water mist fire suppression modeling in ship engine rooms are rare. This paper contributes to the current literature by using the FDS to model a series of fire suppression scenarios defined by the International Maritime Organization (IMO) Circulars, including spray and pool fires with heptane and diesel oil, as well as exposed and obstructed fires. The simulation results are compared to data from full-scale tests conducted at recognized fire testing laboratories. Furthermore, an analysis of both the experimental and model uncertainties is carried out to assess the simulations performance. In general, a good agreement in compartment temperature evolution and fire extinguishing time is found for the modeled fire scenarios. The results support the application of FDS in a PBD approach for the design of water mist fire extinguishing systems for machinery spaces in ships. In this way, designers and engineers could model different machinery volumes and nozzles spacings that differ from those prescribed for a one story square engine room of the IMO, and, thus, predict the evolution of temperatures and extinguishing times for get the authorities approval.     

相邻房间可燃物间距对火灾蔓延的影响

运用CFAST6.0软件对两相邻房间进行了火灾模拟,通过对三种情况下着火房间和相邻房间数据的比较,分析了相邻两房间的可燃物三种间距下着火房间火灾蔓延至相邻房间的可能性,以及火灾蔓延至相邻房间后对两房间火灾危险性的影响,进而得出相邻房间可燃物间距对火灾蔓延的影响作用。     

An experimental study on timely activation of smoke alarms and their effective notification in typical residential buildings

The volume of smoke alarm sound in rooms (other than room of sound origin) in real houses and smoke alarm activation time in rooms in full-scale model houses using ionization, photoelectric and dual detector smoke alarms were determined in this study. The alarm sound level measurements indicated that the sound level in many locations is likely to be too low to provide reliable notification, particularly for sleeping people, if smoke alarms are not installed in every room. In addition, changing to a lower frequency (520 Hz square wave) alarm would further aid effective notification of building occupants. The smoke alarm activation measurements showed that the time to detection (given a particular smoke source) was influenced by door position (open versus closed), the room in which the fire occurs, the location (room or hallway) of the detector, the type of detector and the smoke alarm manufacturer. Furthermore time to detection is also influenced by the type and form of the material that is burning. It was observed that photoelectric smoke alarms had the highest incidence of non-activation and when they did activate they, on average, took longer to activate than ionization and dual (ionization and photoelectric) smoke alarms over all smoke sources considered in this study. It is concluded that to achieve early detection and provide adequate notification, smoke alarms are necessary in every room and should be interconnected.