地下商铺火灾燃烧特性研究

通过开展大型火灾试验,分析火灾蔓延途径和火灾情况下商铺内温度分布,研究相对封闭的地下空间内的火灾燃烧特性。将火源位置设置于房间中部和墙角处,分析火源位置对火蔓延特性的影响。试验结果表明,使用机械排烟和自然补风时,商铺内未发生轰燃,只出现了燃烧相对缓慢的火蔓延现象。燃料的摆放方式可削弱火蔓延趋势。火源位于商铺中间时,火蔓延只持续了较短时间后熄灭,其蔓延路径与前人提出的一维线性蔓延假设不一致。火源位于墙角时,火焰沿着墙面附近快速蔓延,火灾持续时间是火源位于商铺中间时的两倍以上。     

综合管廊内防火隔板对电缆火蔓延的影响

以苏州城北路综合管廊标准段为参考建立FDS全尺寸火灾数值仿真模型,模拟分析综合管廊电力电缆舱室发生火灾时的火势发展形势、温度分布。在管廊左、右两侧设置了4层电缆,分有、无防火隔板两个场景研究防火隔板对火势发展及温度分布的影响。结果表明：未设置防火隔板时,管廊内发生火灾时火势的发展方向首先以横向蔓延为主,顶部电缆随着火势的扩大及烟气聚集传热发生燃烧最后向管廊的其他区域蔓延。设置防火隔板后,竖向火的蔓延时间延缓了约40%,管廊内最高温度降低约18%。     

瑞士凯乐阻燃窗纱和装饰布——瑞士生产、瑞士质量、欧洲首选

对实际火灾的分析表明,很多火灾是由于室内织物(如窗帘、床单)首先被点燃,或火焰通过室内织物迅速蔓延而酿成的。品质优良的阻燃织物在火焰烧烤下不起火、为燃     

某“三合一”场所火灾数值重构及消防安全隐患对策

以FDS模拟某"三合一"场所火灾发展过程,再现火灾发生时的烟气、火势蔓延、温度等随时间的变化情况,并观察到轰燃现象。通过对热释放速率、温度、烟气浓度随时间变化的分析,验证了此次火灾中人员的死亡原因是吸入浓烟缺氧窒息而死。结合模拟结果分析"三合一"场所生活区划分、广告牌设置、疏散通道设置等方面的消防安全隐患,并提出针对性的措施。     

外墙窗户面积及位置对建筑外立面火蔓延的影响

搭建20层的全尺寸办公建筑三维模型,通过设置不同窗户面积、窗户位置研究外窗对建筑外立面竖向火蔓延的影响。研究发现窗户面积较大时,火灾竖向蔓延速率更快,室内温度升高更快,采用大的窗墙比更容易加快火灾在建筑外立面的竖向蔓延。在竖直位置上,随着窗户上移,各楼层的引燃时间均增加。     

古建筑传统防火措施适用性模拟分析

基于FDS软件对古建筑的防火措施包括墙壁涂泥抹灰、天井、瓦屋顶和山墙等进行适用性分析。结果表明：室内墙壁涂泥抹灰具有较好的防火功能,可延缓火灾轰燃时间60 s,减少古建筑木材损失18%;天井面积增大可延缓火灾在水平方向的蔓延,轰燃面积减小;随着天井面积增大,离火源较远区域的升温速率降低,而离火源较近区域的升温速率先降低后增加;瓦屋顶能够有效防止飞火,建议古建筑屋顶采用瓦或其他难燃材料进行完全遮盖;山墙可一定程度阻隔飞火向邻近房屋蔓延,建议天井两侧的山墙高度高出屋檐0.5 m以上。     

丽江古城木结构建筑火灾发展特点分析

结合丽江古城建筑的调查,对建筑的火灾荷载、通风条件、构件耐火极限和火灾蔓延途径等基本参数进行了统计和归纳。结合火灾动力学分析研究丽江古城建筑火灾的发展规律和特点,建立丽江古城建筑火灾发展的事件树。结合建筑火灾发展的时间规律,提出按控制火源、增设报警系统提高初起阶段控火能力、增设消防设施提高发展阶段控火能力、严格防火分隔防止轰燃阶段火灾蔓延4道防线建立火灾防控体系,提出古城建筑消防安全改造和灭火救援的相关建议。     

典型热塑性材料竖直逆向火蔓延研究

以典型的热塑性材料聚丙烯(PP)和聚甲基丙烯酸甲酯(PMMA)为研究对象,实验分析了不同宽度的试样竖直贴壁向下燃烧的温度、火蔓延速率等参数,并给出火蔓延速率、未燃区表面接收的对流传热和辐射传热的计算公式。试样长度为20cm,厚度为3 mm,宽度分别为1、2、3、4、5cm。实验表明:燃烧中PP材料会受热熔融生成液滴并发生卷落现象,火焰主要呈蓝色且温度较低,卷落时出现火焰高度和温度增加。PMMA材料流动性差,不产生熔融液滴并在试样上方有稳定的黄色火焰。火蔓延速率受试样宽度与流动性的综合影响。在实验范围内,随着宽度的增加,PP的火蔓延速率呈先减小后增大的趋势,PMMA的火蔓延速率呈单调递增的趋势。     

怎样确定起火点

火灾现场勘查的目的在于查清起火原因。而查清起火原因的关键一步是找出起火点。这是关系到火灾原因能否查清的首要前题。那么,在火灾现场勘查中,根据什么来确定起火点呢? 一、根据物质燃烧的规律来确定起火点。一般规律,可燃物燃烧总有它的起始点,不可能在同一时间内把可燃物烧光。火总是由一点燃向另一点,从而形成了火灾的蔓延方向。这个蔓延方向的起点,就是起火点。     

一起高层建筑火灾事故原因分析及引发的思考

从一起高层建筑火灾事故案例入手,介绍了此类火灾事故调查的方法,特别注重了起火部位和起火点的勘验认定,分析了起火原因和造成火灾蔓延扩大的成因。提出加强建筑外墙保温材料防火性能的管理、限制外墙大型户外广告牌的设置、规范竖向井道的防火封堵、预留空调外机摆放的位置、强化动火用火的管理制度以及保障建筑消防设施的完好有效等改进高层建筑防火性能的建议。     

The contribution of flames under ceilings to fire spread in compartments

An experimental investigation has been made of flames spreading beneath both combustible and non-combustible ceilings. Experiments were performed in a model representing the ceiling of a corridor with a fire at one end: a gas burner was used to represent the fire, this was replaced by wooden cribs in experiments to be described in later part of this report.

The flames rising vertically from the fire in effect drew air up into the horizontal layer of flames and gases beneath the ceiling. Depending on the rate of flow of fuel gas (or rate of burning of the cribs) this air could be sufficient for complete combusion of the fuel gases and the flame length was then apparently determined by mixing processes within the layer. When this air was not sufficient, the remaining air for combustion was entrained vertically into the horizontal layer from the cool air beneath and the flames became much longer.

Correlations of lengths of horizontal flames beneath non-combustible ceilings have been derived and related to the much shorter lengths of vertical flames. Relationships have been derived from the experimental data from which it is possible to estimate the radiation downwards from a hot non-combustible ceiling and the gases beneath it to the floor with a view to estimating the contribution to fire spread on the floor. A heat balance of the ceiling gases was satisfactory, so confirming the validity of the calculations. Horizontal flames radiate more of the heat produced at a level sufficient to assist fire spread than do vertical ones.

A combustible ceiling lining results in longer flames, an increase in the distance over which heat radiated downwards at an intensity sufficient to promote fire spread and a faster rate of increase of radiation than a non-combustible one with similar thermal constants.

The aspect of performance which best related to the results of BS 476 tests was the rate of increase of radiation downwards in the early part of the experiments. The radiation downwards was apparently partly determined by extraneous factors such as the detachment of the board from its holding nails and whether the decomposition products were emitted as jets.

The rate of spread of fire along a narrow strip of wood on the floor beneath a burning ceiling lining has been calculated and the results related to the index of performance on the Fire Propagation Test.     

FEP 通信电缆燃烧性能试验研究

利用FIPEC 试验装置对FEP 通信电缆的燃烧特性进行了全尺寸试验研究。通过测试通信电缆在燃烧过程中的热释放速率、产烟速率、燃烧增长速率指数及火焰蔓延距离等参数研究其火焰蔓延情况,同时对影响电缆火焰蔓延的因素进行了分析。研究发现：点火源功率对FEP 通信电缆的火焰蔓延影响较小;电缆的排列方式和热边界条件是其影响FEP 通信电缆火焰蔓延的重要因素。同火源功率下,间隔排列比接触排列的火焰蔓延速度更快,其火灾危险性要大;同火源功率下,在钢梯后增加不燃背板比未加背板安装的火焰蔓延速度要快的多,其火灾危险性要大得多;FEP 通信电缆燃烧性能可达到GB 31247-2014《电缆及光缆燃烧性能分级》的B1 级。     

Effectiveness of vertical barriers in preventing lateral flame spread over exposed EPS insulation wall

Insulation panels made of organic, combustible materials are frequently used in the exterior thermal insulation systems (ETIS) for buildings. Such combustible insulation panels have been involved in several catastrophic building fires in recent years in China. One potential strategy to mitigate this fire hazard is to limit fire spread over the ETIS. The present work evaluates the effectiveness of vertical fire barriers in inhibiting fire spread over exposed insulation walls made of expanded polystyrene (EPS) panels. Reduced-scale experiments were carried out indoors using EPS panels with or without two vertical barriers made of non-combustible mineral wool, the fire started at the bottom center of the middle panel. The interval and width of the barriers were varied systematically, while the temperature distribution on the wall, the radiation heat flux from the fire, and the infra-red (IR) images were recorded. To demonstrate the validity of the concept, an outdoor, full-scale experiment was carried out using a 7-floor building. Our reduced-scale experiments showed that the installation of two vertical fire barriers successfully stopped the lateral flame spread, decreasing the peak temperatures of the two side panels by about 300 °C for all barrier configurations tested. When barrier width was fixed at 5 cm, an increase of the barrier interval from 30 to 90 cm led to increases in the peak temperatures, radiation heat flux, and the maximum rate of upward flame spread. By contrast, when barrier interval was fixed at 90 cm, an increase of the barrier width from 2 to 5 cm had little influence on the combustion dynamics of the middle panel but the peak temperature on the side panels dropped, consistent with the smaller heat transferred with wider fire barriers. In the regions of the side panels next to the barriers, pyrolysis and deformation could be observed with barrier widths of 2 and 3 cm, but not 5 cm. Finally, our outdoor, full-scale experiment demonstrated that a 30 cm wide vertical barrier made of air-filled cement successfully stopped the lateral flame spread over exposed EPS wall. The study highlights the effectiveness of vertical fire barriers in preventing the lateral flame spread over the exposed EPS insulation wall and provides another option for enhancing the fire safety of the combustible insulation systems.     

燃料覆盖率对非连续分布固体竖向火蔓延的影响

非连续分布固体燃料是指多个固体可燃物非常靠近但被气隙隔开的状态,与连续分布燃料相比,非连续分布燃料更能够代表一些现实的火灾情况,以往的研究中较少涉及.笔者通过实验的方法分析不同燃料覆盖率下固体燃料竖直向上火焰蔓延的特点.所选用的浇筑型聚甲基丙烯酸甲酯(简称"PMMA")材料广泛应用于高层建筑外立面中,呈现出一种非连续分...     

Evaluation of the Onset of Flashover in Room Fire Experiments

Two series of full scale room fire tests comprising 16 experiments are used for a study of the onset of flashover. The fire loads were varied and represented seven different commercial applications and two non-combustible linings with significantly different thermal inertia were used. The test results showed that by lowering the thermal inertia and thereby lowering the heat loss from the room and at the same time increasing the thermal feedback, a thermal runaway occurred before significant fire spread; but only for objects composed of a mixture of plastic/rubber/textiles and wood/celluloses. In these cases the onset of thermal runaway was found to occur at room temperatures in the range 300°C to 420°C, supporting that the room temperature at the onset of thermal runaway is strongly dependent on the thermal inertia. It also shows that the onset of thermal runaway cannot in all cases implicitly be predicted by the traditional flashover temperature criterion of 500°C to 600°C. For fire loads composed of pure wood/celluloses the onset of flashover occurred about the same time as fire spread irrespectively of linings and at significantly higher room temperatures (725°C). This can be explained by flammability parameters making wood/celluloses less sensitive to thermal feedback.     

Dynamic modeling of fire spread in building

Modeling fire spread in a building is a key factor of a fire risk analysis used for fire safety designs of large buildings. In this paper, a dynamic model of fire spread considering fire spread in both horizontal and vertical directions is described. The algorithms for simulating the fire spread process in buildings and calculating dynamic probability of fire spread for each compartment at each time step of simulation are proposed. The formulae used in calculating the input data for the dynamic fire spread model are derived. The dynamic fire spread model can easily be applied for any building including high-rise buildings. A detailed example of calculation of fire spread in a two-storey office building is described.     

A computational study on the use of balconies to reduce flame spread in high-rise apartment fires

High-rise apartment fires are perhaps the most dangerous residential fires. Within high-rise buildings, flames and smoke can travel through ductwork, between interior walls, and up elevator shafts and stairwells. One of the fastest ways a fire spreads to other floors is along the exterior of the building due to open windows. Flame spread up vertical walls has been studied experimentally and computationally for years in the US and abroad. A numerical study has been undertaken to examine the reduction of vertical flame spread due to the presence of a balcony. The depth and geometry of the balcony greatly affects the vertical movement of fire. By varying the balcony depth and geometry, the aim of this study is to find an optimum configuration that reduces vertical fire spread on the external wall.     

Flame Heights and Heat Transfer in Façade System Ventilation Cavities

The design of buildings using multilayer constructions poses a challenge for fire safety and needs to be understood. Narrow air gaps and cavities are common in many constructions, e.g. ventilated façade systems. In these construction systems flames can enter the cavities and fire can spread on the interior surfaces of the cavities. An experimental program was performed to investigate the influence of the cavity width on the flame heights, the fire driven upward flow and the incident heat fluxes to the inner surfaces of the cavity. The experimental setup consisted of two parallel facing non-combustible plates (0.8 × 1.8 m) and a propane gas burner placed at one of the inner surfaces. The cavity width between the plates ranged from 0.02 m to 0.1 m and the burner heat release rate was varied from 16.5 kW to 40.4 kW per m of the burner length. At least three repeated tests were performed for each scenario. In addition, tests with a single plate were performed. The flame heights did not significantly change for Q′/W < 300 kW/m² (where Q′ is the heat release rate per unit length of the burner and W is the cavity width). For higher Q′/W ratios flame extensions up to 2.2 times were observed. When the distance between the plates was reduced or the heat release rate was increased, the incident heat fluxes to the inner surface increased along the entire height of the test setup. The results can be used for analysing methodologies for predicting heat transfer and fire spread in narrow air cavities.     

A new standard test method for the quantification of fire propagation behavior of electrical cables using Factory Mutual Research Corporation's small-scale flammability apparatus

A new specification test standard for cable fire propagation has recently been developed at Factory Mutual Research Corporation (FMRC), using FMRC's 50 kW-scale flammability apparatus. Guidelines for fire protection of grouped cables in non-combustible industrial and commercial occupancies have been formulated. Cables are classified into three groups on the basis of their fire propagation behavior: Group 1 cables: fire propagation beyond the ignition zone is not likely to occur and fire protection is not required; Group 2 cables: fire propagates slowly beyond the ignition zone and fire protection is required in most applications; and Group 3 cables: fire propagates rapidly beyond the ignition zone and fire protection is always required. This paper describes the concepts associated with the development of the standard test and fire protection guidelines for cables.