Simulation of temperature and smoke distribution of a tunnel fire based on modifications of multi-layer zone model

Some modifications on Suzuki’s multi-layer zone model (MLZ) have been done to predict temperature and smoke distribution of a tunnel fires, i.e., the radiation heat loss of fire source is taken into account and a four-surface radiation heat transfer model is introduced. Like Suzuki’s model, as a special long and narrow space, the tunnel space is also divided into a number of layers in vertical direction and regions in longitudinal direction. The physical properties like temperature and species (CO, CO₂, etc.) are assumed uniform in every zone like two-zone model. However, the different heat transfer model is introduced. The MLZ model prediction is compared with the experiments of USTC and CFD model (FDS). It shows good agreement between the model prediction, experiments and CFD models (FDS). And the MLZ model needs less time than CFD model.     

A zone model for fire development in multiple connected compartments

Developments in fire engineering and in the understanding of fire influence on humans, together with advances in regulatory base, encourage the use of performance-based methodologies and numerical fire simulation tools in ship design. A numerical method for fire modelling in multiple ship compartments is proposed here, which can be used routinely in the assessment of alternative designs due to its speed and robustness. The method uses an improved treatment of walls between compartments and an efficient algorithm for pressure calculations. The performance of the method is demonstrated on two examples, experimental results for which were available in the literature.     

Wall fire behavior in an under-ventilated room

An experimental setup has been designed and built to study, at a laboratory scale, the behavior of a wall fire in a semi-confined compartment both in naturally ventilated and vitiated (combustion products) atmospheres.A diffusion flame is stabilized along a vertical porous flat burner located at the rear of an enclosure. The combustion is supplied by injection of propane through the vertical burner surface. Air enters into the compartment by natural convection through a door, topped by a soffit, opposite the burner. After reaching a thermal steady state, the temperature field in the compartment is characterized. Then, the door is closed leaving only a horizontal free slot (0.06 m height) between the top of the door and the bottom of the soffit. The flame behavior completely changes, the intensity of the spontaneous flame emission decreases drastically and a weakly blue vertical flame leaves the burner surface and moves, at low velocity, through the chamber, up to the open slot. Visualizations of the flame and measurements of the temperature and main stable chemical species fields are performed in order to characterize the behavior of a flame referred as a ghosting flame.This flame displacement mode has been already observed in full-scale fires by Audouin (Fifth International Symposium on Fire Safety Science, 1997, Melbourne, p. 1261–1272). After the initial “flame propagation”, combustion can be stabilized at the room aperture that participates to the development of the fire outside the compartment. This work contributes to a better understanding of this phenomenon in order to prevent such a fire.     

A comparison of a FLOW3D based fire field model with experimental room fire data

This paper describes the application of a fire field model based on the FLOW3D CFD software to the simulation of fire induced flows in domestic sized rooms. Several scenarios are examined consisting of various sized fires, fire locations and door sizes. Comparisons are based on upper-layer room temperatures, mass fluxes in and out of the fire compartment and door-way vertical and horizontal temperature and velocity profiles. For most cases the model agrees reasonably well with the observed trends, however the results suggest that significant mesh refinement is required to produce results in quantitative agreement with experimental results. A close examination of the horizontal door-way velocity profiles highlights the need for careful modelling and experimental practices in this region.     

Turbulence statistics in a fire room model by large eddy simulation

Fire and smoke movement in a room is influenced by the turbulence characteristics (such as Reynolds stress, turbulent heat flux, etc.) of the flow and temperature fields. In order to accurately predict fire and smoke movement by computational fluid dynamics (CFD), it is necessary to verify these turbulence quantities. The purpose of this study is to predict the turbulence structure of the flow and temperature fields due to a fire in the compartment by large eddy simulation (LES) using detailed experimental data to verify the simulation results. The results show reasonably good agreement with experimental data for both the mean flow properties and the turbulence quantities with the exception of the region near ceiling. This study provides useful information for verifying LES technique when applied to compartment fires.     

A quasi-steady-state model for predicting fire suppression in spaces protected by water mist systems

A quasi-steady-state model was developed to predict the effectiveness of a water mist system for extinguishing fuel spray and pool fires. The model was developed for obstructed fires where extinguishment primarily occurs as a result of a reduction in oxygen concentration due to the consumption of oxygen by the fire and due to dilution of the oxygen with water vapor. Interactions between the mist and the flame are neglected resulting in limiting case predictions. The model is based on conservation of energy and requires the following input parameters: fire size, compartment geometry, vent area, and water flow rate. The steady-state temperatures and oxygen concentrations predicted by the model can be used to determine the smallest fire that can be extinguished. The predictions made by the model compared favorably to the results of three full-scale test series conducted for the US Coast Guard. These tests were conducted in shipboard machinery spaces with compartment volumes ranging from 100 to 500 m³ with a wide range of ventilation rates and openings. The model was able to accurately predict the compartment temperatures during the tests where steady-state conditions were produced. The model was also able to accurately predict the extinguishment times for a wide range of fire sizes and was used to identify the smallest fire that could be extinguished for a given set of conditions.     

Three-dimensional non-isothermal numerical model for predicting semi-volatile organic compound transport process in a room

In this paper, a three-dimensional non-isothermal computational model for predicting indoor SVOC distribution is proposed, considering the effects of turbulence diffusion and suspended particles. The realizable k-ε model is introduced for turbulent flow simulation in a room. The Euler-Euler method is adopted to deal with the gas-particle two-phase flow coupled problem. Inertia slip velocity and irreversible first-order absorption boundary are employed for more accurate prediction of particle motion. The simulated curve of outlet gas-phase di-2-ethylhexyl phthalate (DEHP) concentration with emission time is verified by available experimental data. The emission process of DEHP in a 15 m² room in Beijing during 100 days with or without air cleaner is simulated by the developed model considering air leak through window and door gaps. It is found that if the air cleaner keeps on all the time during 100 days the gas-phase DEHP concentration in the room will tend to be uniform, while the emission process is far from equilibrium without an air cleaner even the emission lasts 100 days. Results also suggest that floor heating, decrease of particle concentration, weaken of heat transfer, enhancement of mass transfer, and air infiltration in window gap contribute to decrease DEHP concentration.     

Development of a hybrid field and zone model for fire smoke propagation simulation in buildings

A novel hybrid fire model combining the traditional field and zone modeling approaches to simulate the fire smoke propagation in a multi-storey building is presented in this paper. In the hybrid model, the field model is used to model the fire smoke movement in rooms with complex fire-induced airflow where the two-layer zone assumption of the zone model is not valid, e.g. in the room of fire origin. The zone model is used to model the fire smoke propagation in the rooms/corridors where the hot smoke layer is well stratified and the smoke movement can be reasonably simulated based on the two-zone concept. The fundamentals of the hybrid fire model are presented and discussed in this paper. The interface treatment between the field model and the zone model is presented in detail. In addition, some examples highlighting the application of the new hybrid model to simulate the smoke propagation in a multi-storey building are also presented. The hybrid model provides a more accurate prediction of fire smoke propagation and consumes less computational resources in comparison to the full zone and full field models, respectively.     

A room fire screening test procedure

Full-scale room fire economics necessitate a screening test procedure requiring only a small amount of material to quantitatively assess heat release rate. This test could determine which materials may justify full-scale testing and those which fail early. Such a procedure is described, sample results are given, and it is suggested that correlation of screening test results with full-room and bench-scale test methods could improve the evaluation of the pre-flashover fire spread characteristics of materials.     

烤漆房的火灾事故原因与防火安全

在分析汽修厂烤漆房火灾事故原因的基础上,对其防火安全的注意事项作了阐述。     

ASET-B: A room fire program for personal computers

ASET-B, a personal computer program for predicting the fire environment in a single room, is presented. ASET-B solves the same differential equations as the previously developed computer program, ASET (Available Safe Egress Time), using a simpler numerical technique. ASET-B requires as input the height and area of the room, the elevation of the fire above the floor, a heat loss factor, and a fire specified in terms of heat release rate. The program predicts the thickness and the temperature of the hot smoke layer as a function of time. ASET-B is written in BASIC and is not subject to copyright. This paper describes the program and its use. Included are a listing of the program, program variable name listing and a sample run. A discussion of user modifications also is given. Reference: William D. Walton, ASET-B: A Room Fire Program for Personal Computers,Fire Technology, Vol. 21, No. 4, November 1985, p. 293This paper is a contribution of the National Bureau of Standards and is not subject to copyright.     

Modeling VOCs emissions in a room with a single-zone multi-component multi-layer technique

Building envelopes are usually comprised of several layers with different materials, which can significantly affect volatile organic compounds (VOCs) concentrations in indoor environments. These layers may act as source and sink alternatively depending on the different sorption and diffusion potentials. The model proposed here is a single zone one and it considers the different emission properties of building components, namely, the different sorption and diffusion characteristics of the side walls, the floor and the ceiling. In addition, each component comprises of several layers, which represents different construction materials. Two VOCs, ethyl acetate and n-octane, representing polar and nonpolar compounds respectively, are modeled to study the emission profiles in a room with several building materials. The effects of various construction materials, and the different convective mass transfer coefficients between room air and different building components, on the emission characteristics are investigated.     

Advanced model for predicting the fire response of concrete filled tubular columns

In this work, a nonlinear finite element three-dimensional model is presented and validated in order to study the behaviour of axially loaded concrete filled tubular (CFT) columns with circular cross-section exposed to fire. A realistic sequentially coupled nonlinear thermal-stress analysis is conducted for a series of columns available in the literature. The model is validated by comparing the simulation results with the real fire resistance tests. By means of this model, and extensive sensitivity analysis is performed over a wide range of aspects concerning the finite element modelling of the problem under study, including new key factors not studied previously. Based on this sensitivity analysis several modelling recommendations are given in this paper, which will be useful for future research work. The validated numerical model is furthermore employed to study and discuss the Eurocode 4 Part 1–2 simple calculation model, which is deeply analysed in this paper.     

单室火灾的数值模拟研究

采用大涡模拟和混合分数燃烧模型，对单室火灾进行了数值模拟研究。对混合分数燃烧模型的不足进行了分析，并指出了改进的方向。比较了喷淋和无喷淋状态下单室火灾的烟气发展规律及燃烧产物成分的变化情况。计算结果表明：由于喷淋的加入，可燃物的不完全燃烧性增强，导致烟气中烟灰成分大量增加，二氧化碳等产物的生成量呈减少趋势；对不同燃烧释热率的火灾情况进行了数值模拟，随着火源释热率的增大，室内热烟气的温度增高得更快，热烟气温度层下降的速度越快，下降的高度越低。单室内火灾热烟气的温度分布呈明显的分层现象，可以将场模拟中的烟气层转换为上下两层相互区分的热烟气层和冷烟气层。     

Fire in a residential building: Comparisons between experimental data and a fire zone model

Fire hazards in residential buildings were investigated by conducting a range of fire experiments on a typical New Zealand dwelling built for this purpose. Hazards evaluated ranged from limited liquid-fuel fires to larger-scale burns using items of furniture. The effectiveness of detection and suppression devices was also tested.A series of experiments in a three-bedroom dwelling were conducted and included both a nonflashover and a flashover fire, and a selection of experimental results were analyzed to determine smoke and gas movement together with temperature rises in the various rooms. These results were compared to the predictions of the CFAST fire and smoke transport computer model.     

火电厂消防设计中冷凝器污垢累积规律的神经网络预测模型

为了防止火电厂锅炉消防设计中冷凝器因结垢而引起锅炉的火灾和爆炸事故,需要对冷凝器污垢系数的发展规律进行预测。设计了一种结合K-均值算法和Chebyshev 神经网络的污垢系数预测模型,针对Chebyshev 神经网络的弊端,应用K-均值算法对其进行改进,将污垢系数随时间发展的曲线分为启动阶段、粘附阶段和老化阶段3 类。结果表明,改进Chebyshev 神经网络模型有效地预测了冷凝器污垢系数发展规律,得到的输出结果比渐进预测和幂率预测模型的预测结果更准确,该模型具有算法简单、收敛速度快的特点。     

A stochastic model for the number of deaths in a fire

A stochastic model for the number of deaths resulting from a fire is put forward. The particular case being considered is that of flaming ignition on a bed in a hospital ward and the crucial importance of the features of the early stages of development becomes apparent. Note: An account of this work was presented at the Fifth International System Safety Conference which was held in Denver, Colorado in 1981. A full version of this paper is due to appear inFire Safety Journal, Vol. 4, No. 3, pp. 169–184.     

A model for predicting heat transfer through noninsulated unloaded steel-stud gypsum board wall assemblies exposed to fire

With the advent of performance-based codes and performance-based fire safety design options, validated fire-resistance models have become essential. In this paper, a one-dimensional heat transfer model for steel-stud, noninsulated, unloaded gypsum board protected wall assemblies is presented. Also presented are a comparison between temperature predictions and measured temperatures at different locations in gypsum board wall assemblies as well as a comparison between the predicted and measured fire-resistance ratings. The model, which predicts slightly conservative fire-resistance ratings compared to the experimental measurements, is appropriate for most fire safety engineering applications. Considerations for further model development are identified.