An Experimental Study of Smoke Movement in Multi-Storey Buildings

This paper presents the results of an experimental study of smoke movement in a 10-storey building. Eight full-scale experiments including four real fuel fires and four propane fires were conducted in the National Research Council Canada (NRCC)’s 10-storey experimental tower to generate smoke movement data that can be used for the validation of computer models. The heat release rate (HRR) of fire cannot be measured in this tower, so to estimate the HRR of fuel-package fires in this study, an approach using propane as a fuel was developed to reproduce the temperature distribution of various fuel-package tests.     

Post-flashover fires for structural design

One of the major difficulties in designing structures to resist fires is the selection of post-flashover design fires. This paper proposes modifications to the parametric equation for post-flashover fires given in the Eurocode. The proposal is based on design fires obtained from the COMPF2 computer program, after calibration to results from realistic test fires using judicious characterisation of the fuel in the input data. The proposed new equation gives a much better fit to the real fire data than the existing Eurocode equation, which predicts temperatures lower than those measured in tests.     

Parametric temperature–time curves of medium compartment fires for structural design

A parametric temperature–time curve for structural fire design purposes is developed for small and medium compartment fires. This method may be used, with reasonable precision, to estimate the temperature history of a fully developed compartment fire. It concerns mainly cellulosic (wood-based) fires. This method has three main characteristics: (1) the temperature–time curves are determined by two key parameters of fire severity: maximum gas temperature (intensity) and fire duration; (2) the maximum gas temperature and fire duration are determined by the fire load density (or surface area of fuel), opening factor, geometric shape and thermal properties of compartment boundaries; (3) both ventilation- and fuel-controlled fire are explicitly distinguished in this method. Comparisons of the predicted curves with the test results and computer simulation show the applicability of this method.     

Simulating the effects of fuel type and geometry on post-flashover fire temperatures

This paper discusses the effect of fuel type and geometry on predicted compartment temperatures derived from computer modelling of post-flashover compartment fires. Many previous studies have investigated post-flashover fires with either wood crib or liquid pool fuels, but very few analytical or experimental studies have considered realistic wood-based fuels with different ratios of surface area to volume, combined with plastic-based fuels. A simple single zone fire model was used to calculate the temperatures in post-flashover compartment fires. The program includes a catalogue of furniture items, each with fuel mass loss rate evaluated on the basis of a constant regression rate on all exposed surfaces. The program also includes a pool-burning model and considers wood fuels and thermoplastic fuels burning together inside a compartment. Use of the model shows that the total fuels load alone is not sufficient to characterise a post-flashover fire. The fire temperature is highly dependent on the fuel type and geometry. For given ventilation and total fuel load, the resulting temperature depends greatly on the average thickness of the wood fuels and the presence of thermoplastic fuels. The ratio of the available fuel surface area to the ventilation opening is particularly important. Several fire scenarios involving different fuel types and characteristics are simulated and compared with Eurocode parametric fires.     

Effect of cross section and ventilation on heat release rates in tunnel fires

Model scale fire tests were performed in tunnels with varying tunnel widths and heights in order to study the effect of tunnel cross-section and ventilation velocity on the heat release rate (HRR) for both liquid pool fires and solid fuel fires. The results showed that for well ventilated heptane pool fires, the tunnel width nearly has no influence on the HRR whilst a lower tunnel height clearly increases the HRR. For well ventilated solid fuel fires, the HRR increases by approximately 25% relative to a free burn test but the HRR is not sensitive to either tunnel width, tunnel height or ventilation velocity. For solid fuel fires that were not well ventilated, the HRRs could be less than those in free burn laboratory tests. In the case of ventilation controlled fires the HRRs approximately lie at the same level as for cases with natural ventilation.     

电气火灾隐患的诊断和改进方法

本文分析了用感官法及电磁法难以发现隐蔽状态的电气火灾隐患，提出了采用红外、超声等现代高新技术在线检测电气火灾隐患的方法，并运用计算机图形处理及智能诊断技术进行科学计算和管理，从根本上对电气火灾进行控制。     

A combined overall and surface energy balance for fully-developed ventilation-controlled liquid fuel fires in compartments

As part of the research to extend the understanding of fully-developed wood fires to non-cellulosic fuels, the outline of a theoretical energy balance for a liquid fuel fire in a compartment is presented. A computer solution of the heat balance is described and the results of simulated fires are given to illustrate the uses of the model and the limitations of the assumptions made in the theory.The results show systematic departures from the well known assumption of the constancy of the ratio of burning rate to ventilation rate; this can account for some of the scatter commonly found in measurements of this ratio.     

Scale modeling of quasi-steady wood crib fires in enclosures

A scale modeling hypothesis for quasi-steady enclosure fires has been experimentally evaluated. The scheme utilizes geometric similarity and freeburn behavior of the source fuel to scale the source fuel element and the enclosure walls from one scale to another. The burning rate, gas and wall temperature rise, combustion product concentrations and radiative heat flux were measured in full, half and quarter-scale enclosures using wood cribs as the fuel. The good agreement of reduced data among different size enclosures strongly supported the modeling hypothesis. Relatively large scatters were observed with combustion product concentrations and radiative heat flux. In general, the scatters for the measured burning rate and gas and wall temperature rise in enclosure fires were within those observed in freeburn crib fires. The experimental results established that the modeling scheme can be used for predicting the burning rate and room environment in enclosure fires.     

Temperature distribution within aircraft-fuel fires

The authors have investigated temperature distribution within aircraft-fuel fires involving JP-4 and 100/130-octane aviation gasoline. Data, based on a relatively simple test method, show where the hottest temperatures are encountered in fires typical of aircraft-fuel spill fires. Average flame temperatures of the two types of fuel are compared as well as temperatures at different levels in the test fires.     

汽车火灾的研究

近年来汽车火灾在全国各地均属上升趋势，火灾损失的比例不断加大，尤其是汽车放火案与汽车电气故障引发的汽车火灾，损失与纠纷越来越多也更加复杂，而汽车燃料油与排气管系统引发的火灾也时有发生。文章主要介绍各种类型火灾的蔓延规律与痕迹特征、起火点判断方法及物证提取时注意事项；并提出了一些防止与减少火灾的措施。     

Spread and burning behavior of continuous spill fires

Spill fire experiments with continuous discharge on a fireproof glass sheet were conducted to improve the understanding of spill fire spread and burning. Ethanol was used as the fuel and the discharge rate was varied from 2.8 mL/s to 7.6 mL/s. Three ignition conditions were used in the experiments; no ignition, instantaneous ignition and delayed ignition. The spread rate, regression rate, penetrated thermal radiation and the temperature of the bottom glass were analyzed. The experiments clearly show the entire spread process for spill fires. Further, the regression rate of spill fires at the quasi-steady burning was lower than that of pool fires and the ratio of the spill fires’ regression rate to the pool fires’ regression rate was found to be approximately 0.89. With respect to the radiative penetration and the heat conduction between the fuel layer and the glass, a regression rate expression for spill fires was developed based on some modifications on existing expressions for pool fires. In addition, a complete phenomenological model for spill fires was developed by combining the characteristics of spread and burning. The model was verified by the experimental data and found to predict the spread process for spill fires with reasonable accuracy.     

Heat transfer mechanisms in liquid pool fires

The heat transfer mechanisms in liquid pool fires were studied. The heat balance in the combustion system which includes both the liquid fuel and the burner vessel was discussed. The convective heat from the vessel wall to the fuel is dominant in small scale pool fires, and was calculated using the finite difference program. The heat flux between the wall and the fuel during flame spreading over the fuel below its flash point in the vessel of small width was calculated. From the results, it was found that the poorer the thermal conductivity of the vessel the larger the heat flux from the wall to the fuel immediately below the fuel surface. The liquid level at which a flame self-quenches was measured for various materials and wall thicknesses of the vessel. The concentration gradient of fuel at the self-quenching liquid level was found to be nearly constant for a given fuel.     

Effect of scale and fuel type on the characteristics of pool fires for fire fighting training

This paper examines the effects of pool size and fuel type on the characteristics of pool fires. The fuels studied include hydrocarbon solvents, alcohol and their blends. The large-scale experiments were conducted on 0.445 and 1 m diameter pools in two enclosures: 41 m long×5.4 m wide×2.4 m high and 25 m long×2.7 m wide×2.4 m high, under a ventilation rate of 1–1.2 m/s. In these tests, measurements of the fuel pyrolysis mass loss rate, heat release rate (from CO₂ and CO concentrations as well as oxygen depletion), smoke extinction area (from laser attenuation), total heat flux emanating from the flame, and the yields of CO₂ and CO were made. Bench-scale tests were conducted using the same fuels and fuel blends on 100 mm× 100 mm pool fires in a Cone Calorimeter—a well-known fire test method.

The hydrocarbon+alcohol fuel blends are used to create large pool fires for fire fighting training. The aim of this study was to: (1) Formulate a fuel blend which will produce a “hot” fire for realistic fire fighting training while generating a minimal quantity of smoke to comply with the pollution regulations. (2) Investigate the effect of fuel type and scale on the properties of the pool fires. (3) Make comprehensive measurements on pool fires in tunnels which can be used for validating mathematical fire models.

This study has resulted in the formulation of a fuel blend which satisfies the requirements of fire fighting training as well as Environment Protection Authority of New South Wales. The bench and the large-scale results correlate well showing good agreement between the heat of combustion, smoke extinction area (SEA) and the yields of CO₂ and CO. The SEA increases with the CO and CO₂ yields which in turn increase with the carbon fraction and the aromatic content of the fuel/fuel blend. The SEA correlates strongly with the CO and CO₂ yields and in both the correlations, the entire data collapse on a single curve. These correlations indicate that the SEA and the CO₂ and CO yields vary mainly with the fuel type, and not so much with the pool size. The flame heat flux increases with the carbon content in the fuel.     

The influence of travelling fires on a concrete frame

When building fires occur in large, open compartments they rarely burn uniformly across an entire floor plate of a structure. Instead, they tend to travel, igniting fuel in their path and burning it out as they move to the next fuel package. Current structural fire design methods do not account for these types of fires. This paper applies a novel methodology for defining a family of possible heating regimes to a framed concrete structure using the concept of travelling fires. A finite-element model of a generic concrete structure is used to study the impact of the family of fires; both relative to one another and in comparison to the conventional codified temperature-time curves. It is found that travelling fires have a significant impact on the performance of the structure and that the current design approaches cannot be assumed to be conservative. Further, it is found that a travelling fire of approximately 25% of the floor plate in size is the most severe in terms of structural response. It is concluded that the new approach is simple to implement, provides more realistic fire scenarios, and is more conservative than current design methods.     

Kerosene lamps and cookstoves—The hazards of gasoline contamination

Gasoline contamination of kerosene has been implicated in accidental fires associated with the use of kerosene illumination lamps and cook stoves. We have investigated potential causes of accidental fires in lamps and lanterns filled with contaminated fuel through controlled tests using typical appliances and varying amounts of contamination. Studying reports of accidents, it is apparent that a common cause of fires is filling hot appliances that are in operation or close to an open flame. The role of contaminated fuel vapor in creating a hazardous situation is shown to be crucial. We evaluate miscibility assumptions and quantify the hazard through flashpoint measurements for mixtures of kerosene and gasoline as a function of the amount of gasoline (up to 10%). A simple model for predicting the flashpoint of an arbitrary mixture is presented.     

Minimum extinguishment area required for safe escape of aircraft occupants during a fuel spill fire

Massive fuel spill fires enveloping the fuselage of large jet aircraft may develop quickly following a crash or other accident. Under such circumstances, occupant survival time is short unless burnthrough of the fuselage can be delayed. The authors propose an analytical method for determining the minimum fire area that must be extinguished in order to delay fuselage burn-through long enough to allow the occupants to escape.     

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.     

Numerical simulation of surface forest fire in Brazilian Amazon

This paper investigates fire spread through surface fuels of the Brazilian Amazon by using a three-dimensional, fully transient, physics-based computer simulation approach. Computer simulations are obtained through the solution to governing equations of fluid dynamics, combustion, heat transfer and thermal degradation of the vegetative fuel. Surface fuel fires composed mostly of dead leaves and twigs were numerically simulated and the calculated rate of spread was compared to findings from field observations. The importance of air humidity, vegetation temperature, moisture content, surface to volume ratio and bulk density was evaluated through the variation of each one individually in numerical simulation runs. Conclusions show that in the range of parameter variation considered, the most important parameters are the vegetation moisture, surface area to volume ratio, and bulk density. The vegetation initial temperature and air humidity, in the range of variation studied, did not influence the fire rate of spread. The numerical simulations also showed that the radiation process is very important and directly affects the fire rate of spread. Convection is less important because of the absence of external wind. The model is able to capture the main effects of a surface forest fire typical of the Amazon, and can be used as a numerical tool for studying such fires.     

Burning Rate of Liquid Fuel on Carpet (Porous Media)

The occurrence of a liquid fuel burning on carpet has been involved in many incendiary and accidental fires. While the research on a liquid fuel fire on carpet is still limited, much work on porous media has been performed using sand or glass beads soaked with liquid fuel. In this study, a heat and mass transfer theory was first developed to analyze the burning process of liquid on carpet, and then several small-scale tests were performed to validate the theory. This analysis is valid for pool fires intermediate in size (5–20 cm. in diameter). The experimental apparatus consisted of a circular pan (105 mm) and a load cell. Varying amounts of fuels (heptane, kerosene and methanol) were spilled onto the carpet, which was allowed to burn in a quiescent environment. It was found that due to the different controlling mechanisms, the liquid burning rate could be less or more than that of a similarly spilled free-burning pool fire. For the worst-case scenario in fires, the maximum enhancement of the burning rate due to the porous media is predictable through the physical properties of the fuel. This analysis is valid for both combustion and evaporation. Several similar results in the scientific literature are analyzed to further describe the trend. This work explains the role of carpet in liquid pool fires and also helps to explain special risks related to the presence of carpet involved in arsons and will be useful in reconstruction of the early development of an incendiary or accidental fire.     

Bending of wind-blown flames from liquid pools

The bending of a flame by wind influences the amount of heat transferred by radiation and convection, the fuel burning rate, and the flame spread rate. To what extent will a flame be bent by wind? The author presents correlations of data taken from liquid pool fires, which enable us to predict flame bending and trailing for large fires.