A comparison of gas velocity measurements in a full-scale enclosure fire

Gas velocity measurements were conducted in the doorway of an enclosure containing a natural gas fire. Two independent measurement techniques, Stereoscopic Particle Image Velocimetry (SPIV) and bi-directional impact-pressure probes, were utilized for comparison – the first such comparison for a fire-induced flow in a full-scale structural fire. Gas velocities inferred from the bi-directional probe measurements were consistently greater than SPIV measurements in a region of the flow between the floor and the flow interface. The comparison revealed that a measurement bias exists in the bi-directional probe technique. Estimates of the relative magnitude of the bias were inferred from the results.     

大型室内步行街防火分区划分安全性分析

介绍某商业综合体防火分区设置,针对其室内步行街防火分区划分存在的问题,设置步行街临街商铺火灾和中庭火灾,改变自动喷水灭火系统、机械排烟系统、火源功率三个因素设置6个火灾场景,分析火灾后烟气流动.设置两个场景模拟人员疏散,比较可用疏散时间和必要疏散时间,分析其防火分区划分的可行性.     

Aircraft cargo compartment fire detection and smoke transport modeling

The US Federal Aviation Administration, along with other regulatory agencies, requires that cargo compartments on passenger carrying aircraft be equipped with fire detection and suppression systems. Current regulations require that the detection system alarms within 1 min of the start of a fire and flight tests are required to demonstrate compliance with these regulations. Due to the high costs of flight tests, extensive ground certification tests are typically conducted to ensure that the detection system will meet the time to alarm requirements during the flight tests. For the purpose of improving the detection system design and certification process, a transient computational fluid dynamics computer code for the prediction of smoke, heat, and gas species transport in cargo compartments has been developed. This simulation tool couples heat, mass, and momentum transfer in a body-fitted coordinate system in order to handle a variety of cargo bay shapes and sizes. Ideally, such a physics-based simulation tool can be used during the certification process to identify worst case locations for fires, optimum placement of detector sensors within the cargo compartment, and sensor alarm levels and algorithms needed to achieve detection within the required time. Validation of the model was completed, and comparison of the predicted results with the results obtained from full-scale fire tests in a variety of actual aircraft cargo compartments provides insight into the model capabilities.     

A general formula for the prediction of vent flows

A new formula for fire-induced wall vent flow rate is developed based upon a theoretical derivation and mathematical fit to data. Previous research had developed a formula of mass flow rate for fire-induced doorway flows only. Here it is extended to include window flows. A theoretical model based on an ideal point source fire plume is used to guide the form of the empirical correlation. A thorough examination concerning the difference between the window and doorway flow modes is conducted. Both sill height and width of the windows pose key influence on the formula. The two vent configurations are merged into one equation. The results were compared to available flow data and shown to be within 15% accuracy for a wide range of fire conditions.     

室内火灾危险性分析

利用FDS软件模拟火源在室内不同位置处火灾的危险性,分析火源在不同位置时室内烟气层的温度、氧气体积分数及烟气层高度的变化规律。模拟结果表明:火源在门开口径向方向时,室内1.5 m高度以下空间的烟气层温度较高,氧气体积分数较低,而1.5 m以上情况相反;火源位置距离开口越近,烟气层高度越低,危险性越大。     

Predicting the structural response of a compartment fire using full-field heat transfer measurements

Inverse heat transfer analysis (IHT) was used to measure the full-field heat fluxes on a small scale (0.9 m×0.9 m×0.9 m) stainless steel SS304 compartment exposed to a 100 kW diffusion flame. The measured heat fluxes were then used in a thermo-mechanical finite element model in Abaqus to predict the response of an aluminum 6061-T6 compartment to the same exposure. Coupled measurements of deflection and temperature using Thermographic Digital Image Correlation (TDIC) were obtained of an aluminum compartment tested until collapse. Two convective heat transfer coefficients, h =35 W/m²-K and h =10 W/m²-K were examined for the thermal model using the experimentally measured heat fluxes. Predictions of the thermal and structural response of the same compartment were generated by coupling Fire Dynamics Simulator (FDS) and Abaqus using the two values for h, h =35 W/m²-K and h from convection correlations. Predictions of deflection and temperature using heat fluxes from IHT and FDS with h=35 W/m²-K agreed with experimental measurements along the back wall. The temperature predictions from the IHT-Abaqus model were independent of h, whereas the temperature predictions from the FDS-Abaqus model were dependent on h.     

防火分区对消防联动系统的影响

以北京太阳星城特殊结构的地下车库为背景，通过列举该车库划分防火分区的不同方案，说明了防火分区设计方案的多样化。分析了防火分区对消防联动系统工程的控制和投资产生的影响，论述了减少防火卷帘门的数量和降低其机械故障是规避风险的关键。     

Energy balance in a large compartment fire

The National Institute of Standards and Technology (NIST) and the Nuclear Regulatory Commission (NRC) are collaborating to assess and validate fire computer codes for nuclear power plant applications. This evaluation is being conducted through a series of benchmarking and validation exercises. The goal of the present study was to provide data from a large-scale fire test of a simulated nuclear power plant cable room. The experiments consisted of a hydrocarbon spray fire with a 1 MW heat release rate, burning in a single compartment 7 m wide, 22 m long, and 4 m high. Measurements included the vertical temperature profiles, heat flux to the compartment surfaces, the velocity and temperature at the compartment doorway, and the total heat release rate. From these measurements, an energy balance was considered, in which it was determined that nearly 74% of the fire's energy went to heat compartment surfaces, 22% escaped through the doorway, and 4% heated gases in the compartment.     

某地下商场防火分区性能化设计方案

针对某地下商场不能按常规方法划分防火分区的情况,结合建筑平面布局和商业业态的特点,提出性能化的防火分隔方案,重点阐述性能化消防设计的设计理念。     

Simulation of an experimental compartment fire by CFD

This paper analyses the experimental results, obtained in a compartment fire experiment [Kumar R. Studies on compartment fires. Ph.D. thesis. Indian Institute of Technology, Roorkee, 2004], by using CFD modelling. Experiments were conducted in a compartment by burning methanol as a fuel. Temperatures vs. time were recorded at 11 different locations in the compartment for three sizes of fires.     

火灾报警技术分析

简单回顾了火灾报警技术的发展过程及目前的发展特征,并对火灾报警技术进行了对比分析.     

穿越建筑物的消防车道作为防火分隔的可行性研究

借用森林防火中防火带的概念,拟采用一定宽度的消防车道替代防火墙的方式解决防火分区划分的问题,并对其可行性进行研究.     

对"体防火分区方式"的讨论

对新提出的“体防火分区”方式 ,就其设计依据、执行规范、实用价值、经济效果 ,以及工程实例中存在的危险性 ,提出商榷。     

Buoyancy and inertial force on oscillations of thermal-induced convective flow across a vent

Natural vents are commonly installed in buildings for smoke control. Air motion is induced by buoyancy of the thermal sources inside the building. Hot smoke is expected to be exhausted out of the vent. However, directions of air flowing across the vent might be oscillating under some conditions. The ratio B of buoyancy to inertial force defined by the Grashof number over the square of the Reynolds number is the key parameter in determining airflow oscillations.     

Large eddy simulation of compartment fire with solid combustibles

For properly describing practical building fire processes with solid combustibles, the pyrolysis kinetics model of solid combustibles and the large eddy simulation (LES) approach are applied to the simulation of the thermal decomposition of the polyurethane foam (PUF) slab and the space fire spread in a compartment. The instantaneous variations of the heat release rate of the PUF slab, the smoke temperature, and the smoke interface height with time are obtained under different ventilation conditions. They are in agreement with the measured data. The ventilation conditions have distinct effects on the interactions between the pyrolysis of the PUF slab and the space fire spread. Influenced by the space fire spread, the heat flux on the top plane of the PUF slab exhibits a non-uniform distribution. The PUF slab is consumed in an asymmetric manner.     

大空间建筑防火分区设计的探讨

通过两个工程实例对大空间建筑防火分区进行了分析 ,并从“性能化”设计的角度进行了探讨。     

分隔结构在建筑防火中的重要性

在大楼里设置可靠的防火分隔结构和防火设施是确保其安全的关键。国际火灾调查有限公司经理肯·茜蒙斯这样解释道 :今年《泰坦尼克》票房暴满 ,此豪华游轮的下沉令世人遗憾 ,同时也给防火分隔结构在建筑防火中的重要性提供了有力的证据。一般情况下 ,当设有许多防水隔间的战舰出现紧急情况时 ,船长会命令立即关闭船壁的防火闸门 ,因而即使鱼雷击中舰体 ,战舰也不会下沉。正因为泰坦尼克号豪华游轮缺少将船分成许多防水隔间的船壁 ,一旦海水进入船舱 ,就会迅速蔓延 ,最终导致游轮沉入大海 ,造成大量人员伤亡的悲剧。此原理对公众场合人群骚动…     

室内火灾破拆排烟的CFAST模拟

运用CFAST区域火灾模拟软件,对设有门窗的普通居民建筑室内火灾进行模拟计算,得出不同破拆方案对火灾烟气层随时间变化的影响,并用Origin软件制出曲线图,分析破拆对排烟影响的基本规律.结果表明,当燃烧处于通风控制时,破拆面积越大,其排烟效果越好;在通风口面积相同时,中部破拆比下部破拆效果好;排烟效果与破拆面积、位置有关,与破拆口是否对称无关.