Modellierung des Single Burning Item Tests

Modelling the Single Burning Item Test Harmonisation in Europe led to new standards, tests and classification of building products in fire safety. The Single Burning Item (SBI) test is the new reaction to fire test for the intermediate level. In the test a developing fire caused by a single burning item, e.g. a burning waste paper basket, is simulated. Numerical investigations of the SBI test have been performed by the Federal Institute for Materials Research and Testing (BAM) in cooperation with Technical University Berlin. Two CFD (Computational Fluid Dynamics) codes, Fluent and FDS, have been used to develop models of the SBI test. Data of our own experiments and literature has been used to validate the numerical models. Variation of ventilation in the burning room and variation of ambient air temperature lead to significant changes in temperatures and flow velocities in the burning room. The SBI standard EN 13823 allows the ventilation and ambient air temperature to be in a range. New experiments are necessary to show the effect of one single parameter like ambient air temperature. But the used data and the numerical results give reason to think about narrowing the ranges for ventilation and ambient air temperature in the standard.     

Subgrid scale laminar flamelet model for partially premixed combustion and its application to backdraft simulation

Flame spread after air is suddenly introduced to a vitiated compartment in backdraft is between non-premixed and premixed flame spread under a ventilation-controlled condition. And it is necessary, but difficult to numerically simulate it. In this paper, an attempt of backdraft simulation is introduced. Numerical models including a subgrid scale laminar flamelet model and a partially premixed model are imbedded in FDS3.0 source code for backdraft simulation. Some significant fire characteristics reported in previous backdraft experiments can be seen in the numerical results. It is also indicated that these combined models can be used to predict the partially premixed combustion and fire phenomena under ventilation-controlled conditions.     

The application of a genetic algorithm to estimate material properties for fire modeling from bench-scale fire test data

A methodology based on an automated optimization technique that uses a genetic algorithm (GA) is developed to estimate the material properties needed for CFD-based fire growth modeling from bench-scale fire test data. The proposed methodology involves simulating a bench-scale fire test with a theoretical model, and using a GA to locate a set of model parameters (material properties) that provide optimal agreement between the model predictions and the experimental data. Specifically, a GA based on the processes of natural selection and mutation is developed and integrated with the NIST FDS v4.0 pyrolysis model for thick solid fuels. The combined GA/pyrolysis model is used with cone calorimeter data for surface temperature and mass loss rate histories to estimate the material properties of two charring materials (redwood and red oak) and one thermoplastic material (polypropylene). This is done by finding the parameter sets that provide near-optimal agreement between the model predictions and experimental data, given the constraints imposed by the underlying physical model and the accuracy with which the boundary and initial conditions can be specified. The methodology is demonstrated here with the FDS pyrolysis model and cone calorimeter data, but it is general and can be used with several existing fire tests and almost any pyrolysis model. Although the proposed methodology is intended for use in CFD-based prediction of large-scale fire development, such calculations are not performed here and are recommended for future work.     

Models for calculating flame spread on wall lining materials and the resulting heat release rate in a room

An extensive research programme, dealing with fire growth on combustible wall lining materials, has been ongoing in Sweden over the last decade. Several lining materials were tested in bench-scale fire tests in order to derive basic material flammability parameters. The same materials were also tested in a full scale room test and a 1/3 scale room test for two different scenarios, A and B. Scenario A refers to the case where walls and ceiling are covered by the lining material, Scenario B where lining materials are mounted on walls only.

This study utilises the results from these experiments and presents a mathematical model where material properties derived from standardised bench-scale tests are used as input data. The model predicts fire growth in the full- or 1/3 scale tests, in two different scenarios (A and B), and consists of sub-models for calculating the rate of heat release, gas temperatures, radiation to walls, wall surface temperatures and flame spread on the wall lining material.

A thermal theory of wind-aided flame spread on thick solids is examined and solutions are given and analysed for flame spread velocities under ceilings. Both numerical and analytical solutions are discussed.

The analytical solutions can be used to evaluate the flame spread propensity of materials and thus, whether a certain material is likely to go to flashover or not in the Room Corner Test. More generally, the solutions can be used to estimate whether a material will spread flame in a variety of concurrent flow flame spread scenarios. Results from the analytical solutions are compared with experimental flashover data for 22 materials, showing a good agreement.

The numerical solutions are incorporated into a simple room fire model. The results from the numerical model are compared with experiments on 22 materials tested in the full scale room for Scenario A. Comparisons for Scenario B are made with 10 materials tested in the 1/3 scale room. The results show reasonably good agreement for most materials between the model and the experiments.     

Modeling fire growth in a combustible corner

A fire growth model was developed to predict the flame spread and total heat release rate of a fire in a corner configuration with a combustible lining. Input data for the combustible lining were developed using small-scale test data from the ASTM E1354 cone calorimeter and ASTM E1321 LIFT. The fire growth model includes a flame spread model linked with a two zone compartment fire model, CFAST Version 3.1.2. At a user selected time interval, the flame spread model uses the gas temperature from CFAST to predict the heat release rate of the fire at that time interval, and then provides CFAST with a new heat release rate to predict conditions during the next time step. The flame spread model is an improved version of the flat wall flame spread model previously developed for the US Navy. The model is capable of predicting flame spread in a variety of configurations including a flat wall, a corner with a ceiling, flat wall with a ceiling, unconfined ceiling, and parallel walls. The model has been validated against ISO 9705 test data and was used in this study to simulate conditions that develop in three open corner tests each with a different lining material. The model was able to predict the heat release rate of the fire and provide a reasonable estimate of the flame fronts and flame lengths during the growing fire.     

Evaluation of FDS V.4: Upward Flame Spread

NIST’s Fire Dynamics Simulator (FDS) is a powerful tool for simulating the gas phase fire environment of scenarios involving realistic geometries. If the fire engineer is interested in simulating fire spread processes, FDS provides possible tools involving simulation of the decomposition of the condensed phase: gas burners and simplified pyrolysis models. Continuing to develop understanding of the capability and proper use of FDS related to fire spread will provide the practicing fire engineer with valuable information. In this work three simulations are conducted to evaluate FDS V.4’s capabilities for predicting upward flame spread. The FDS predictions are compared with empirical correlations and experimental data for upward flame spread on a 5 m PMMA panel. A simplified flame spread model is also applied to assess the FDS simulation results. Capabilities and limitations of FDS V.4 for upward flame spread predictions are addressed, and recommendations for improvements of FDS and practical use of FDS for fire spread are presented.     

New approach to estimate temperatures in pre-flashover fires: Lumped heat case

This paper presents a model for estimating temperatures in pre-flashover fires where the fire enclosure boundaries are assumed to have lumped heat capacity. That is, thermal inertia is concentrated to one layer with uniform temperature and insulating materials are considered purely by their heat transfer resistance. The model yields a good understanding of the heat balance in a fire enclosure and was used to predict temperatures in insulated and non-insulated steel-bounded enclosures. Comparisons were made with full scale experiments and with other predictive methods, including CFD modeling with FDS and the so called MQH relationship. Input parameter values to the model were then taken from well-known literature and the heat release rates were provided from the experiments. The fire temperature predictions of the model matched very well with experimental data. So did the FDS predictions while the original MQH relationship gave unrealistic results for the problems studied. Major benefits of using the model in comparison with CFD modeling are its readiness and simplicity as well as the negligible computation times needed. An Excel application of the presented pre-flashover fire model is available on request from the author.     

建筑火灾烟气迁移特性研究及排烟设计

在火灾烟气迁移和机械加压补风的理论研究基础上,基于FDS火灾模拟软件的大涡模拟（LES）及Smagorinsky亚格子尺度模型对某大学宿舍楼进行实体建模。危害性气体CO在水平方向上的体积分数演变非常相近,火源处产生的危害性气体成分能够沿着水平方向传播到远距离处而自身体积分数的变化很小,CO的体积分数峰值随高度呈现明显的阶梯变化。数值模拟结果证明,火灾中大量的人员都死于远距离处的主要原因可能是吸入了大量迎面而来的（而不是身后面赶上的）烟气中危害性气体CO,由此对建筑防火结构设计中针对高层建筑火灾烟气迁移问题提出了改进意见。     

Combination of a fire model and a smoke sensor model

A combination between a fire model and a smoke sensor model has been developed. For the realization of the combined fire and smoke sensor model, output parameters of the fire model have to be converted into input parameters of the sensor model. With respect to the simulation of the smoke evaluation during a fire, most fire models give the smoke mass density as a result. For the simulation of a smoke sensor, information about the size distribution of the smoke particles is needed. The developed model gives the opportunity to simulate the response of a smoke sensor whereby the simulation of the fire is included. The goal of the development of this combined model was to provide a tool for the simulation of EN54 test fires. The model has been validated for EN54 test fires, and results of numerical simulations of EN54 test fires with this combined model are presented and discussed.     

Numerical Simulation of Fire Exposed Façades Using LEPIR II Testing Facility

The fire behavior of external wall insulation system on façades is assessed during LEPIR II testing. This facility involves a 600 kg wood crib fire in a 30 m³ lower compartment of a two levels high concrete structure. External flames develop in front of the façade from the fire compartment through windows with dimensions 1?×?1.5 m (W?×?H). In order to predict the fire exposure of a façade during the test, CFD simulations were carried out with the computational fluid dynamics code Fire Dynamics Simulator (FDS) for two full-scale experiments. The main objective of this study was to evaluate the ability of FDS to reproduce quantitative results in terms of gas temperatures and heat fluxes close to the tested façade. This is an important step before the fire performances of any insulation system can be predicted by numerical tools. A good repeatability was observed in terms of measured gas temperatures for experiments. Maximum heat release rate of the fire, close to 5 MW, was achieved after 5 min of test. When experimental results were compared with numerical calculations, good agreement was found for every quantity. The most critical zone on the facade is located above the fire room and is directly impacted by external flame outgoing from the fire compartment. Temperatures up to 500°C were observed in this zone. For the thermocouples located up to the second level opening, these probes were not located directly in the flames, but rather in the hot gases above the fire plume. The maximum temperature achieved was thus close to 400°C. The proposed model gives correct thermal loads and flames shape near the façade during calibration tests and can be used for further evaluation of combustible material on façade.     

Designing fire safe interiors.

Any product that causes a fire to grow large is deficient in fire safety performance. A large fire in any building represents a serious hazard. Multiple-death fires almost always are linked to fires that grow quickly to a large size. Interior finishes have large, continuous surfaces over which fire can spread. They are regulated to slow initial fire growth, and must be qualified for use on the basis of fire tests. To obtain meaningful results, specimens must be representative of actual installation. Variables--such as the substrate, the adhesive, and product thickness and density--can affect product performance. The tunnel test may not adequately evaluate some products, such as foam plastics or textile wall coverings, thermoplastic materials, or materials of minimal mass. Where questions exist, products should be evaluated on a full-scale basis. Curtains and draperies are examples of products that ignite easily and spread flames readily. The present method for testing curtains and draperies evaluates one fabric at a time. Although a fabric tested alone may perform well, fabrics that meet test standards individually sometimes perform poorly when tested in combination. Contents and furnishings constitute the major fuels in many fires. Contents may involve paper products and other lightweight materials that are easily ignited and capable of fast fire growth. Similarly, a small source may ignite many items of furniture that are capable of sustained fire growth. Upholstered furniture can reach peak burning rates in less than 5 minutes. Furnishings have been associated with many multiple-death fires.(ABSTRACT TRUNCATED AT 250 WORDS)     

Assessment of the Use of Fire Dynamics Simulator in Performance-Based Design

This paper discusses a procedure for the use of fire modelling in the performance-based design environment to quantify design fires for commercial buildings. This procedure includes building surveys, medium-and full-scale experiments and computer modelling. In this study, a survey of commercial premises was conducted to determine fire loads and types of combustibles present in these buildings. Statistical data from the literature were analysed to determine the frequency of fires, ignition sources, and locations relevant to these premises. Based on the results of the survey and the statistical analyses a number of fuel packages were designed that represent fire loads and combustible materials in commercial buildings. The fuel packages were used to perform medium- and full-scale, post-flashover fire tests to collect data on heat release rates, compartment temperatures and production and concentration of toxic gases. Based on the experimental results, input data files for the computational model, Fire Dynamics Simulator (FDS), were developed to simulate the burning characteristics of the fuel packages observed in the experiments. Comparative analysis between FDS model predictions and experimental data of HRR, carbon monoxide (CO), and carbon dioxide (CO₂), indicated that FDS model was able to predict the HRR, temperature profile in the burn room, and the total production of CO and CO₂ for medium- and large-scale experiments as well as real size stores.     

我国屋面工程防火技术路径探讨

阐述了发展我国屋面工程防火技术的路径,首先应制定《屋面系统(制品)燃烧试验方法》,然后据此修订工程设计和材料的相关标准;指出屋面系统及其覆盖的防水材料燃烧试验方法和分级标准的要求不应与墙体一样,建议我国正在修订的国标GB 8624和GB 50016中有关屋面工程防火试验方法宜等效采用EN和ISO相关标准。     

水平隧道火灾通风纵向临界风速模型

火灾时的烟气控制在隧道防火安全设计中占有很重要的位置,为此通过1/20小尺寸模型实验和全尺寸现场试验对水平隧道火灾通风纵向临界风速进行了研究。根据隧道全尺寸试验和小尺寸实验研究结果,并结合Jae等的小尺寸实验结果以及胡隆华的全尺寸试验和数值模拟结果,建立了水平隧道火灾通风纵向临界风速的预测模型。将模型得到的预测结果跟基于气体火源的实验结果进行对比,结果表明 Wu和Barker通过气体火源小尺寸实验所建立的模型预测值偏低。     

An analysis of compartment fire doorway flows

A mathematical study is made to compute the doorway flow behavior due to fire in a room. Two approaches were taken, first a model attempting to include the effect of fire entrainment and vent mixing; second was a model based on an ideal point source plume fire—both in the zone model concept. Limiting analytic results were found for the latter to give insight into the physics. The results were compared to available flow data, and an approximate formula was developed to predict the doorway mass flow rate to within 20% for a wide range of fire conditions. CFD computations were also explored using FDS. Results are compared from FDS and the zone model with experimental data for a wide range of variables.     

Experimental investigation and numerical simulation of a furnished office fire

Experiments were conducted in a full-scale model room equipped with both movable and fixed fire loads to explore fire growth and spread via heat release rates, indoor air temperature and species concentration. The room 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. The northeast and southeast corners each feature a 2.1 m × 0.9 m open doorway. Numerical simulations with parameter adaptation were carried out using FDS software to predict the fire features and were compared with the experimental results. In this study, the material properties and oxygen limit settings in the FDS software were tested to explore their influence on the tendency of heat release rate and on the total amount of heat release. The results show that the heat release rate from the FDS simulations is comparable to the full-scale experiment results during the fire growth period. Temperature profile near ceiling can be modeled well. In the full-involvement burning and decaying periods, the qualitative trends were identical, although the simulated value differed greatly from the experimental result.     

油罐火灾模型试验的安全性分析

采用数学计算和FDS软件模拟对缩小尺寸的油罐火灾模型试验进行安全性分析,得到火焰跳动频率、倾斜角、火焰高度和热辐射安全距离等参数数据,与实际的模型试验进行比较。模拟油罐的直径为1.7m、高度为1.7m,模拟试验中罐底距离地面0.3m,油罐上端开口,环境风速为0m/s及5m/s。结果表明,数学计算和FDS软件模拟的各种数据取最小值时和模型试验最为接近,因此该安全性分析具有可行性,同时建议保守地采取FDS下风向数值作为试验的安全距离。     

建筑材料燃烧性能分级方法的新发展

世界各国均有各自关于建筑材料燃烧性能的分级方法，欧盟颁布了建筑材料（或制品）燃烧性能分级方法（EN13501-1），它是对材料燃烧性能分级方法的一个新发展，它比较科学和系统地对燃烧性能，包括烟密度和燃烧滴落物，进行了分级。     

水平弧形公路隧道临界风速研究

采用FDS建立弧形隧道火灾模型,对模型进行模拟计算,结合Wu&Bakar的临界风速预测模型和计算观测数据,应用MATLAB拟合工具箱建立弧形隧道的临界风速模型。利用该模型预测重庆市某公路隧道在发生火灾情况下的临界风速,将预测结果与Wu&Bakar模型和FDS的预测结果进行对比,结果表明,该模型比Wu&Bakar模型更加接近数值模拟的结果。     

Numerical modeling of the fire-structure behavior of steel beam-to-column connections

This study proposes a numerical model to investigate the behavior of steel beam-to-column connections in fires. Two strategies have been employed to transfer thermal results from a fire simulation to structural analysis. A full scale fire test was performed on a steel beam-to-column connection following the ISO 834 standard fire curve; it was simulated to verify the proposed methods. The wall temperatures obtained by FDS were used as an interface for fire exposure on the surface of the structure. The numerical results are in agreement with the experimental data. In addition, the size effect of the furnace and a sensitivity analysis on insulation materials had been studied. Two reduced beam sections were analyzed and compared with the simulation results of an unreduced beam section. Both sections were able to withstand the severity of the blaze with the runway phenomenon occurred after a similar period of time for each beam.