室内火灾区域模拟及火灾各分模型的模化

简述区域模拟的基本原理,介绍区域模型模拟室内火灾的基本分析方法,给出轰燃前后室内火灾发展的质量、能量守恒方程,并阐述火灾模拟中四个子模型包括火源热释放速率、羽流、开口流、传热的数学模化理论,在具体应用中应合理假设并正确选择各子模型的模化方法,得出符合实际的室内火灾发展规律.     

全盛期室内火灾参数化模型的参数随机性

通过总结各国在全盛期室内火灾升温的参数化模型研究领域的成果和统计国外火灾荷载调查数据,分析了模型输入参数的随机性,建立了火灾荷载密度、开口因子和房间壁面热惰性的概率分布模型,并给出了不同用途房间的火灾荷载密度均值和变异系数、开口因子模型参数的概率密度函数及不同房间壁面热惰性的范围。结果表明,火灾荷载密度服从正态分布,开口因子模型中的参数服从对数正态分布,而房间壁面的热惰性可认为是均匀分布的随机变量。     

论21世纪防火安全问题

概括介绍20世纪世界范围内的火灾形势，综述防火技术研究的进展及尚未解决的问题。在防火安全技术、燃烧基础理论、火灾模化仿真模型研究、消防队救灾出动模化及今后2～3个世纪内防火安全技术及装备方面提出新的课题，展望未来。     

地下建筑公共娱乐场所火灾烟气防治

本文描述了地下建筑公共娱乐场所火灾烟气扩散特点，根据国内多卜研究成果，提出防排烟系统应将烟气限制在着火房间内，防止烟气分层的破坏。采用经实际火灾试验证实的火灾模型是消防工程设计的发展方向。我国关于地下建筑火灾计算机模化和水力模化已经取得可喜的研究成果。     

用于模拟建筑火灾的风险分析模型CUrisk的开发和火灾案例分析

加拿大卡尔顿大学开发了火灾风险计算机模型CUrisk，用以评估四层木结构商品建筑的火灾安全设计。该模型包括系统模型和许多子模型。系统模型用于设定风险分析框架及控制子模型数据流。它还负责计算每个火灾场景的生命危险值。其他子模型包括火灾增长、烟气运动、边界失效火灾蔓延、人员反应和疏散以及建筑造价和经济损失等模型。利用子模型的输出数据，系统模型可计算三个决策参数：对生命的预期风险、对受伤情况的预期风险以及消防成本预期。这些参数是以可能的火灾场景及相关概率为基础的。文章简要介绍了CUrisk模型，并介绍了运用该模型对四层商业建筑所进行的多火灾场景风险分析的结果。     

火灾模化与相似理论

讨论了火灾模化与相似理论的关系，介绍了相似理论三定律，分析了火灾模化的困难性，最后介绍了全相似与近似相似的概念。     

火灾模化方程的数值解法

高层建筑火灾模化的核心工作有两部分。一是通过假设建立物理模型，并由此推导出火灾模化方程。二是通过求解火灾模化方程，得出不同时刻建筑单元内的压力、温度和烟气浓度等参数。而火灾模化方程的数值解则是模化软件编制的核心，也是整个工作的重点和难点。本文详尽介绍了用逐步逼近法求解压力，以及求常微分方程的初值问题的常用方法欧拉法和龙格—库塔法，并详述了通过能量守恒方程的二阶龙格—库塔法，求解温度的方法和步骤。     

基于FDS的室内火灾蔓延特性研究

本文基于FDS软件建立室内火灾模型,研究了不同火源位置、排风口位置及大小对烟气蔓延的影响,得出室内火灾下温度变化、热释放速率、烟气分布等特征,并对室内火灾发展形势进行模拟,在一定程度上能为研究火灾人员疏散安全时间评定提供理论基础。     

隧道火灾模型试验中参数的无量纲化研究

针对隧道火灾通风现象中众多参数复杂的相互作用特点,本文利用量纲分析的方法,对隧道火灾通风实验中火源热释放率大小与模型进行了无量纲化处理,对壁面导热过程、对流与辐射换热过程、壁面粗糙度的影响等相关参数,从量纲的角度进行了理论上的分析,比较了它们各自在隧道火灾的发展过程中起到的不同作用。最后确定了火源热释放率大小与模型是影响火源附近热力状态的决定性因素;与壁面导热、辐射过程相比,对流在火灾通风过程中起着决定性的控制作用。最后指出可以将各个参数所起不同作用的分析结果作为建立隧道火灾模型试验的理论参考,将无量纲关系式作为模型试验处理数据的依据。     

基于LSTM网络的船舶机舱火灾多特征融合探测

针对船舶机舱火灾高效准确探测的需求,建立基于LSTM-ID3 判决的船舶火灾探测方法。首先确定采集船舶火灾特征的三类传感器,然后完成 LSTM 神经网络模型的构建、参数的优化,将 LSTM 神经网络输出的明火、阴燃火、无火的概率值与烟雾持续时间作为决策树的输入量,输出火灾探测结果。利用国家标准火典型数据进行训练,并开展相关试验,对船舶机舱火灾进行探测。试验结果表明,与其他算法进行对比,探测准确率达到97%以上,该方案能对机舱火灾做出有效探测,为船舶安全提供科学依据。     

Numerical simulation of fire in a tunnel: Comparative study of CFAST and CFX predictions

The mathematical modeling of fire growth and smoke movement in any enclosure is a formidable task. Two types of deterministic models are in vogue, zone models and field models (popularly known as CFD technique). CFAST is a popular zone model used for modeling of fires in enclosures. Likewise, CFX is a general purpose CFD code used for various purposes including modeling of fires. In the present paper, a tunnel of length 150 m having a rectangular cross-section of 80 m² has been considered for analyzing the temperature and velocity profiles generated by fire, placed at a distance of 20 m from one end of portal, by both CFAST and CFX. The simulation by CFAST has been carried out by dividing the tunnel into 1, 2, 5, 8, 10, 12 and 15 compartments of equal size, where these compartments are joined by openings or vents having same cross-section as that of the tunnel. In case of tunnel divided into 15 compartments the fire source position lies at the position of vent; CFAST predicted very high temperatures. The simulations have also been carried out by dividing tunnel into unequal sized compartments such that position of fire was at the center of the compartment. It was found that for accuracy of results, location of fire source inside compartment is an important factor. Computational difficulty was experienced when tunnel was divided into more than 15 compartments. In this paper, a comparative study of temperatures predicted by CFAST and CFX has been done. The CFX and CFAST predictions show that smoke temperature changes with a pattern roughly similar to that of heat release rate. The temperature profiles at selected positions cannot be predicted by CFAST unlike CFX. The detailed features like flame tilt, flow field can only be observed from CFX predictions.     

A parametric natural fire model for the structural fire design of multi-storey buildings

A parametric natural fire model is presented, which is derived on the basis of simulations with heat balance models for realistic natural design fires, taking into account the boundary conditions of typical compartments in residential and office buildings. These so-called iBMB parametric fire curves are formulated with the help of simplified empirical equations which can easily be used for structural fire design as part of a performance-based natural fire design concept. The iBMB parametric fire curves are checked and validated by comparison with results of different heat balance models and with published fire tests from different fire research laboratories. In addition, a natural fire test in a test room with ordinary office room furnishings has been performed which supports the parametric natural fire model presented here. The application of the iBMB parametric fire curves is demonstrated by means of an example.     

On Radiant Network Models of Thermocouple Error in Pre and Post Flashover Compartment Fires

Thermocouples are often used to obtain gas temperature measurements in compartment fires. Such measurements are subject to a thermal lag during fire growth, but the main problem is a steady-state error induced by radiant heat transfer at the thermocouple surface. This error is sensitive to thermal parameters of the flame, compartment structure, thermocouple surface and combustion products; and is also influenced by the size and position of both the flame and thermocouple. The literature contains models of varying sophistication to enable an assessment of steady-state error. A model is now proposed that makes use of the concept of radiosity. Developed from radiant network theory, the model can be applied to both pre-flashover and post-flashover conditions. Experiments have been performed using different sizes of thermocouple and the models compared. The simpler models pre-date the more sophisticated and predict much larger errors than the latest published and current versions.     

变电站电缆沟火灾探测试验与数值仿真研究

为探讨火灾探测器灵敏度对电缆沟火灾响应的影响程度,验证火灾监控系统的准确性,应用点式温度探测器、点式烟雾探测器、电缆式感温探测器和吸入式烟雾探测器4种火灾探测器,在标准变电站电缆沟防火分区内进行了全尺寸电缆火灾试验,测试不同灵敏度火灾探测器的火灾报警序列。根据电缆沟的实际尺寸,利用FDS搭建模拟明火和阴燃两种不同火灾场景,对不同灵敏度火灾探测器的温度场、有毒气体质量浓度和火灾报警顺序进行了分析和讨论。试验结果表明,在变电站电缆沟火探测中,电缆式感温探测器、吸入式烟雾探测器、点式感烟探测器火灾平均响应时间分别为41.2,111.4,331.8 s;吸入式感烟探测器的灵敏度对探测结果影响较大,其火灾报警响应时间比电缆型线性温度探测器约延迟50%。     

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.     

Thermal response of steel framing members in open car park fires

For open car park structures, adopting a performance-based structural fire design is often justified and allowed because the fire does not reach flashover. However, this design approach requires an accurate assessment of temperatures in structural members exposed to car fires. This paper describes a numerical study on the thermal exposure on steel framing members in open car park fires. Steel temperatures are computed by the coupling of computational fluid dynamics and finite element modeling, and by analytical models from the Eurocodes. In addition, the influence of galvanization on the steel temperature evolution is assessed. Results show that temperatures in unprotected beams and columns are influenced by the section geometry, car fire scenario, modeling approach, and use of galvanization. Galvanization slightly delays and reduces peak temperature. Regarding the different models, CFD-FEM (CFD: computational fluid dynamics, FEM: finite-element method) coupled models predict lower temperatures than the Hasemi model, because the latter conservatively assumes that the fire flame continuously touches the ceiling. Further, the Hasemi model cannot account for the effect of reduced emissivity from galvanization on the absorbed heat flux. Detailed temperature distributions obtained in the steel members can be used to complete efficient structural fire designs based on the member sections, structure layout, and use of galvanization.     

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.     

Experimental study on fire performance of cross laminated timber structure exposed to compartment fire

为了研究室内自然火灾作用下可燃的正交胶合木(cross laminated timber, CLT)对CLT房间火灾荷载的贡献和不同层板组成的CLT对火灾的动态影响，开展4次内表面受火面积不同、板材层板组成不同的CLT房间自然火灾试验，直接受火CLT面积占CLT房间内表面积百分比分别为0%、19.8%、36.4%和87.6%；并以双区域模型为基础，建立考虑炭化层脱落的CLT结构室内自然火灾温度场计算模型，对CLT房间火灾试验进行模拟，分析双区域模型应用于CLT结构自然火灾时的有效性及局限性。试验结果表明：CLT受火面积对室内自然火灾发展过程及热量释放影响显著，随着CLT受火面积的增大燃烧速率显著提高，火灾的热释放速率增大；炭化层是否脱落对火灾发展过程影响显著，炭化层脱落时间及区域存在随机性；CLT单层层板厚度越薄，炭化层越早发生脱落；考虑CLT燃烧及炭化层脱落的双区域模型可一定程度上准确模拟CLT房间自然火灾室内空气温度，但是火灾降温阶段双区域模型预测的温度始终低于试验温度。     

密闭机舱双火源燃烧质量损失研究

在3 m×3 m×3.5 m的缩尺度船舶密闭机舱中,设置边长分别为10,15,20 cm的正方形双油池,试验研究双油池不同间距下的燃烧速率变化规律。结果表明：密闭舱室内的双油池火可分为初始、稳定、熄灭三个典型燃烧阶段,不同面积油池的无量纲间距S/L与燃烧速率之间呈现抛物线关系且质量损失率达到峰值时S/L的阈值在0.70～0.85,这与开放空间以及隧道半封闭空间下的双火源发展有很明显的区别。在此基础上,给出了密闭舱室内修正间距S的无量纲热释放速率预测模型。