Experimental study and numerical simulation for a storehouse fire accident

Full-scale experiment and numerical simulations are carried out on a shelf fire in a storehouse to study the ignition manner, the fire spread and the combustion characteristics. A computational fluid dynamics (CFD) model of fire-driven fluid flow, FDS (Fire Dynamics Simulator), is used to solve numerically a form of the Navier–Stokes equations for fire. Ignition manner experiments with both cigarette ends and lighter are conducted first. Then a full-scale experiment on a shelf fire is performed. The temperatures are measured and the fire growth and spread process is analyzed. A numerical model is used to simulate the experiment; the temperatures, fire growth and heat release rate are studied. In numerical simulations, the grid size resolution is analyzed. The experimental results of temperatures and the fire growth and spread process are compared with the results of numerical simulations. It shows that the numerical results are in good agreement with the experimental results. The chimney effect is also observed in both the experiment and the simulation. These useful data can be helpful in the numerical reconstruction of the whole storehouse fire accident.     

Influence of fire ignition locations on the actuation of smoke detectors and wet-type sprinklers in a furnished office

Experiments were conducted in a full-scale model office equipped with movable and fixed fire loads to explore the influence of ignition source (movable fire load(s)) conditions on smoke detector and sprinkler actuation. The interior plan dimension is 5.7 m × 4.7 m and the net ceiling height is 3.3 m. Both northeast and southeast wings have a 2.1 m × 0.9 m single door to be opened. Seven fire scenarios (seven different ignited fire load configurations) under natural ventilation were investigated experimentally. The results show that the amount of fire load at the initial stage in a room fire does not markedly affect smoke generation and does not significantly impact the actuation time of the smoke detectors. When the fire source is located near a corner, the plume corner effect greatly increases; smoke detectors and sprinklers can activate quickly and effectively actuate the fire suppression. When the fire source is located in the room's center, given the uncertainty regarding smoke detector and sprinkler actuation, it may not be possible to control the fire spread.     

Verification of a Lagrangian particle model for short-range firebrand transport

Firebrands are a harbinger of damage to infrastructure; their effects cause a particularly important threat to people living within the wildland-urban-interface. Short-range firebrands travel with the wind with little or no lofting, and cause spotfires. In this work, the design of a novel firebrand generator prototype is discussed to achieve a uniform shower of firebrands. The transport of short-range firebrand is studied to verify the existing Lagrangian particle model of Fire Dynamics Simulator. Uniform, non-combusting cubiform and cylindrical firebrands are projected using the firebrand generator. The experimentally observed distribution of particles on the ground is compared with a simulated distribution using the fire dynamic simulator. The results show that the existing Lagrangian model gives a good agreement with the experimental data.     

某仓库火灾实验与数值模拟对比

采用FDS模拟某仓库火灾,并与实验结果比较温度曲线和火灾蔓延过程。在仓库中放置三层金属货架,分打火机和烟头两种引燃方式和不同点火位置进行实验。模拟与实验得到的温度曲线相似度很高。250s前模拟与实验得到的火灾蔓延过程比较相似,250s后由于纸箱倒塌,模拟结果出现延迟。合理摆放货物的情况下烟头引燃仓库火灾的可能性较小。     

某典型三合一场所火灾的数值模拟重构

以FDS模拟重庆开县某三合一场所火灾的全过程,再现火灾发生时的烟气、温度、能见度、CO体积分数等随时间的变化情况,通过提取火源附近壁面的温度信息,验证起火点的位置.通过对热释放速率、温度、CO体积分数随时间变化的分析,证实此次火灾中人员的死亡原因是高温和低氧的共同作用.模拟结果为火灾调查工作提供依据.     

Influence of fire source locations on the actuation of wet-type sprinklers in an office fire

An experiment is conducted on a full-scale model office and an actual sprinkler system to explore the influence of fire source locations on sprinkler actuation. The office space is a brick structure that measures 5.7 m in interior length, 4.7 m in width and 2.4 m in ceiling height, and equipped with a sprinkler system. The investigated fire source (100 kW LPG burner) locations include the room center, wall centers, room corner, and other locations at different distances from sprinklers. The results show that actuation of the sprinklers is affected by the fire source locations and the heat conduction properties of the glass temperature-sensing bulb. Average actuation time of all the tests is 102 s, around 40 s faster than if the fire source is located in the room center. For fire sources in corners, sprinklers are quickly activated at the experimental time 75 s, showing concentrated hot gas flow.     

火灾模化理论在火灾事故调查中的应用

对火灾模化理论在火灾事故原因调查中的运用进行了深入研究,提出利用计算机模拟的方法定量分析失火原因,为火灾调查提供确凿有力的证据。     

基于大型场所的FDS数值模拟分析

使用FDS软件模拟了大型娱乐场所中发生火灾时烟气流动的三种情况,分别讨论了有无水喷淋作用。排烟措施及防烟分隔情况下的烟气蔓延情况,结果表明大涡模拟FDS可以用来预测大尺度较复杂结构中的烟气流动,能够清楚地显示流动情况。     

公路隧道火灾的数值模拟

应用火灾动力学模拟软件FDS对某公路隧道内的火灾过程进行了数值模拟，定量预测了不同工况条件下隧道内的烟气流动状况及温度分布，并在此基础上对隧道通风方式、耐火性能，以及火灾探测报警中的温度点漂移问题进行了讨论。     

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。     

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.     

A two-dimensional numerical investigation of the oscillatory flow behaviour in rectangular fire compartments with a single horizontal ceiling vent

This paper presents a comparison of fire field model predictions with experiment for the case of a fire within a compartment which is vented (buoyancydriven) to the outside by a single horizontal ceiling vent. Unlike previous work, the mathematical model does not employ a mixing ratio to represent vent temperatures but allows the model to predict vent temperatures a priori. The experiment suggests that the flow through the vent produces oscillatory behaviour in vent temperatures with puffs of smoke emerging from the fire compartment. This type of flow is also predicted by the fire field model. While the numerical predictions are in good qualitative agreement with observations, they overpredict the amplitudes of the temperature oscillations within the vent and also the compartment temperatures. The discrepancies are thought to be due to three-dimensional effects not accounted for in this model as well as using standard ‘practices’ normally used by the community with regards to discretization and turbulence models. Furthermore, it is important to note that the use of the turbulence model in a transient mode, as is used here, may have a significant effect on the results. The numerical results also suggest that a linear relationship exists between the frequency of vent temperature oscillation (n) and the heat release rate ( ) of the type , similar to that observed for compartments with two horizontal vents. This relationship is predicted to occur only for heat release rates below a critical value. Furthermore, the vent discharge coefficient is found to vary in an oscillatory fashion with a mean value of 0.58. Below the critical heat release rate the mean discharge coefficient is found to be insensitive to fire size.     

Experimental and numerical study on water mist suppression system on room fire

Full-scale experiment and numerical simulations are carried out on a room fire to study water mist suppression system with heat release rate of 6 MW. A computational fluid dynamics (CFD) model of fire-driven fluid flow, FDS (Fire Dynamics Simulator), is used to solve numerically a form of the Navier–Stokes equations for fire. A fire experiment without water mist is performed and the temperatures are measured to validate the predictions of FDS code against the experimental data. Then a fire experiment with water mist suppression system is performed and the temperatures and extinguishing time are measured. The validated numerical model is used to simulate the experiment; the temperatures, oxygen concentration and extinguishing time are compared and studied. In numerical simulations, the cell size sensitivity is analyzed. The experimental results of temperatures and extinguishing time are compared with the results of numerical simulations. It appears that the numerical results are in good agreement (qualitatively) with the experimental data in temperature fields. These useful data can be helpful in accomplishing the design of water mist suppression system and the design regulations for fire safety management.     

火灾中人员伤亡原因及疏散行为

根据火灾调查取得的有关参数,使用FDS火灾模拟软件对火灾过程进行了模拟,取得了楼梯间内一氧化碳、二氧化碳、氧气含量及能见度等模拟数据。燃烧产物毒害性、高温烟气、烟气减光性是火灾中致人伤亡的原因。针对火灾中人员的疏散行为,分析了火灾事故教训,提出了预防伤亡的措施。     

Experimental study on the performance of a load-bearing steel stud gypsum board wall assembly exposed to a real fire

The National Institute of Standards and Technology (NIST) and the Center for Better Living (CBL) have formed an international collaboration to assess the performance and failure mechanisms of gypsum wall assemblies under real fires/furnace conditions. In an effort to compile an experimental database necessary to validate models that could be used to predict their performance and ultimate failure under various design fires, a full scale test was conducted in the Large Fire Laboratory (LFL) at NIST. This paper provides a valuable experimental data set on the performance of a full scale loaded gypsum steel stud assembly exposed to an intense full scale compartment fire.     

Probabilistic simulation of fire endurance of a wooden beam

This paper presents a probabilistic simulation approach to assessment of the fire endurance of a wooden load-bearing beam in a fire. The approach introduces several novel modelling techniques developed by VTT, such as the probabilistic fire simulator which is an interface enabling to run fire simulation models in the Monte Carlo mode and the time-dependent event-tree method which enables to take into account the active fire safety measures such as detectors, first-aid fire fighting, sprinklers and fire brigade intervention. Also the simulation of the response to heat and the mechanical performance of the structure are carried out using the Monte Carlo technique. The charring rate of the wooden beam is calculated by a new model that includes explicitly the principal sources of uncertainties and variabilites. The results show explicitly the effectiveness of different fire safety measures in reducing the risk of structural failure.     

从一起轰燃火灾看轰燃对火灾调查的影响

通过一起轰燃火灾事故调查,综合证人证言和火灾现场勘验、火灾物证技术鉴定等,分析认定起火部位、起火点和起火原因,并对在轰燃火灾现场勘验如何认定起火部位、起火点进行探讨.     

浅谈数值模拟在建筑防火性能化设计中的应用

运用FDS软件针对某一具体建筑进行防火性能化设计,并得出该建筑达到危险状态时刻的各个参数,对同类建筑的防火设计有一定的参考价值。