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Fire Scenario (fire + scenario)
Selected AbstractsHuman survivability in motor vehicle firesFIRE AND MATERIALS, Issue 4 2008K. H. Digges Abstract Automobile fires are consistently among the largest causes of fire death in the United States (about 500 annually) and the U.S. motor vehicle industry and others have spent a significant amount of money in recent years studying this problem. The authors of this review have analyzed the auto industry reports, the scientific literature, and statistical data, and conclude that measures should be taken to improve survivability in automobile fires. The U.S. Federal Motor Vehicle Safety Standard 302 (FMVSS 302) was introduced almost 40 years ago to measure the flammability of interior materials, but improvements in the crashworthiness of automobiles and their fuel tanks and the increased use of combustible materials have changed the motor vehicle fire scenario significantly. In particular, the primary threat has changed from ignition of a small quantity of combustible interior materials by a lit cigarette, in 1960, to ignition of a large quantity of combustible interior and exterior materials by an impact-induced fire, at present. The authors therefore suggest that FMVSS 302 is no longer relevant to automobile fire safety and recommend improved standards based on objective criteria for fire safety performance (fireworthiness) at the system/vehicle level as is routinely done for crashworthiness. Copyright © 2008 John Wiley & Sons, Ltd. [source] Development of fire-retarded materials,Interpretation of cone calorimeter dataFIRE AND MATERIALS, Issue 5 2007B. Schartel Abstract There is little consensus within the fire science community on interpretation of cone calorimeter data, but there is a significant need to screen new flammability modified materials using the cone calorimeter. This article is the result of several discussions aiming to provide guidance in the use and interpretation of cone calorimetry for those directly involved with such measurements. This guidance is essentially empirical, and is not intended to replace the comprehensive scientific studies that already exist. The guidance discusses the fire scenario with respect to applied heat flux, length scale, temperature, ventilation, anaerobic pyrolysis and set-up represented by the cone calorimeter. The fire properties measured in the cone calorimeter are discussed, including heat release rate and its peak, the mass loss and char yield, effective heat of combustion and combustion efficiency, time to ignition and CO and smoke production together with deduced quantities such as FIGRA and MARHE. Special comments are made on the use of the cone calorimeter relating to sample thickness, textiles, foams and intumescent materials, and the distance of the cone heater from the sample surface. Finally, the relationship between cone calorimetry data and other tests is discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Effective thermal actions and thermal properties of timber members in natural firesFIRE AND MATERIALS, Issue 1 2006Jürgen KönigArticle first published online: 28 JUL 200 Abstract For the thermal analysis of structural or non-structural timber members, using conventional simplified heat transfer models, thermal conductivity values of timber are normally calibrated to test results such that they implicitly take into account influences such as mass transport that are not included in the model. Various researchers and designers have used such effective thermal conductivity values, originally determined for standard fire exposure, to evaluate other fire scenarios such as natural fires. This paper discusses in qualitative terms some parameters that govern the burning of wood and their influence on effective conductivity values. Reviewing fire tests of timber slabs under natural fire conditions, the study explains why effective conductivity values, giving correct results for the ISO 834 standard fire scenario, should not be used in other fire scenarios. For this reason, the thermal properties of timber given in EN 1995-1-2 are limited to standard fire exposure. As shown by heat transfer calculations, the effective thermal conductivity of the char layer is strongly dependent on the charring rate and therefore varies during a natural fire scenario. It has also been shown that char oxidation during the decay phase in a natural fire has a significant influence on the temperature development in the timber member, since char surface temperatures exceed the gas temperature in the compartment or furnace. Using increased effective gas temperature as thermal action during the decay phase, and varying conductivity values for the char layer, fairly good agreement could be obtained regarding the temperature development in the timber member and the char depth. Copyright © 2005 John Wiley & Sons, Ltd. [source] Assessment of fire protection performance of water mist applied in exhaust ducts for semiconductor fabrication processFIRE AND MATERIALS, Issue 5 2005Yi-Liang Shu Abstract Fume exhaust pipes used in semiconductor facilities underwent a series of fire tests to evaluate the performance of a water mist system. The parameters considered were the amount of water that the mist nozzles used, the air flow velocity, the fire intensity and the water mist system operating pressure. In order to make a performance comparison, tests were also performed with a standard sprinkler system. The base case served as a reference and applied a single water mist nozzle (100 bar operating pressure, 7.3 l/min water volume flux and 200 µm mean droplet size) installed in the pipe (60 cm in diameter) subjected to a 350°C air flow with an average velocity of 2 m/s. In such a case, the temperature in the hot flow dropped sharply as the water mist nozzle was activated and reached a 60°C saturation point. Under the same operating conditions, four mist nozzles were applied, and made no further contribution to reducing the fire temperature compared with the case using only a single nozzle. Similar fire protection performances to that in the base case were still retained when the exhaust flow velocity increased to 3 m/s and the inlet air temperature was increased to 500°C due to a stronger input fire scenario, respectively. Changing to a water mist system produced a better performance than a standard sprinkler. With regard to the effect of operating pressure of water mist system, a higher operating pressure can have a better performance. The results above indicate that the droplet size in a water-related fire protection system plays a critical role. Copyright © 2005 John Wiley & Sons, Ltd. [source] Dangers relating to fires in carbon-fibre based composite materialFIRE AND MATERIALS, Issue 4 2005Tommy Hertzberg Abstract Inhalable carbon fibres have been suspected to pose similar threats to human health as asbestos fibres. It is well-known that fibres having a diameter of less than 3 µm might be inhaled and transported deep into the human respiratory system. Some composite materials use carbon fibres as structural reinforcement. These fibres do not pose any risks as such as they are firmly connected to the laminate and surrounded by a polymer matrix. Also, these fibres typically have diameters >6 µm and thus, are not inhalable. However, if the material is exposed to a fire, the carbon material might be oxidized and fractionated and thereby, inhalable fibres might be generated into the fire smoke. The capability of carbon fibre-based composite material to produce dangerous inhalable fibres from different combustion scenarios has been investigated. It was found that the risk of fires generating inhalable carbon fibres is related to the surface temperature, the oxygen level and the airflow field close to the material surface. The temperatures necessary for oxidation of the carbon fibre is so high that it is possible that only a flashover situation will pose any real danger. Other possible danger scenarios are highly intense fires (e.g. a liquid fuel fire), or situations where structural damage is part of the fire scenario. Copyright © 2005 John Wiley & Sons, Ltd. [source] Numerical determination of 3D temperature fields in steel jointsFIRE AND MATERIALS, Issue 2-4 2004Jean-Marc Franssen Abstract A numerical study was undertaken to investigate the temperature field in steel joints and to compare the temperatures in the joints with the temperatures of the adjacent steel members on the hypothesis that the thermal protection is the same on the joint and in the members. Very brief information is given on the numerical model, supplemented with parametric studies made in order to determine the required level of discretization in the time and in the space domain. A simplified assumption for representing the thermal insulation is also discussed and validated. Different numerical analyses are performed, with a variation of the following parameters: (i) type of joints, from very simple to more complex configurations, with welds and/or bolts, all of them representing joints between elements located in the same plane; (ii) unprotected joints or protected by one sprayed material; (iii) ISO, hydrocarbon or one natural fire scenario. The fact that the thermal attack from the fire might be less severe because the joints are usually located in the corner of the compartment is not taken into account. Copyright © 2004 John Wiley & Sons, Ltd. [source] Fire exposure of liquid-filled vesselsPROCESS SAFETY PROGRESS, Issue 1 2003Larry L. Simpson Pressure vessels in the chemical industry generally have top-mounted pressure relief valves (PRVs) sized to handle fire exposure and other possible scenarios. Designers usually assume that the fire scenario causes liquid to boil and vapor to vent, regardless of the initial liquid level. Under some circumstances, however, a high liquid level, together with thermal expansion, can result in a vessel being full of liquid when the PRV opens. If so, the initial fluid discharged through the PRV would be a two-phase gas-liquid stream. This paper analyzes non-reactive phenomena occurring during the heat-up and venting process in non-agitated liquid-filled pressure vessels. A new criterion is developed to determine if the vapor-venting sizing assumption is justified. Results from several cases show that pressures in most liquid-filled vessels sized for vapor-only flow will be below the ASME Code-allowable values during fire exposure. Hence, the common industry practice of ignoring two-phase flow when sizing fire cases is usually justified. [source] The effect of temperature and ventilation condition on the toxic product yields from burning polymersFIRE AND MATERIALS, Issue 1 2008A. A. Stec Abstract A major cause of death or permanent injury in fires is inhalation of toxic gases. Moreover, every fire is unique, and the range of products, highly dependant on fire conditions, produces a wide variety of toxic and irritant species responsible for the most fire fatalities. Therefore, to fully understand each contribution to the toxicity it is necessary to quantify the decomposition products of the material under the test. Fires can be divided into a number of stages from smouldering combustion to early well-ventilated flaming through to fully developed under-ventilated flaming. These stages can be replicated by certain bench-scale physical fire models using different fuel-to-oxygen ratios, controlled by the primary air flow, and expressed in terms of the equivalence ratio (the actual fuel/air ratio divided by the stoichiometric fuel/air ratio). This work presents combustion product yields generated using a small-scale fire model. The Purser Furnace apparatus (BS7990 and ISO TS 19700) enables different fire stages to be created. Identification and quantification of combustion gases and particularly their toxic components from different fire scenarios were undertaken by continuous Fourier transform infrared spectroscopy. The relationship between type of the fire particularly the temperature and ventilation conditions and the toxic product yields for four bulk polymers, low-density polyethylene, polystyrene (PS), Nylon 6.6 and polyvinyl chloride (PVC) is reported. For all the polymers tested, except PVC, there is a dramatic increase in the yield of products of incomplete combustion (CO and hydrocarbons) with increase in equivalence ratio, as might be expected. For PVC there is a consistently high level of products of incomplete combustion arising both from flame inhibition by HCl and oxygen depletion. There is a low sensitivity to furnace temperature over the range 650,850°C, except that at 650°C PS shows an unexpectedly high yield of CO under well-ventilated conditions and PVC shows a slightly higher hydrocarbon yield. This demonstrates the dependence of toxic product yields on the equivalence ratio, and the lack of dependence on furnace temperature, within this range. Copyright © 2007 John Wiley & Sons, Ltd. [source] Effective thermal actions and thermal properties of timber members in natural firesFIRE AND MATERIALS, Issue 1 2006Jürgen KönigArticle first published online: 28 JUL 200 Abstract For the thermal analysis of structural or non-structural timber members, using conventional simplified heat transfer models, thermal conductivity values of timber are normally calibrated to test results such that they implicitly take into account influences such as mass transport that are not included in the model. Various researchers and designers have used such effective thermal conductivity values, originally determined for standard fire exposure, to evaluate other fire scenarios such as natural fires. This paper discusses in qualitative terms some parameters that govern the burning of wood and their influence on effective conductivity values. Reviewing fire tests of timber slabs under natural fire conditions, the study explains why effective conductivity values, giving correct results for the ISO 834 standard fire scenario, should not be used in other fire scenarios. For this reason, the thermal properties of timber given in EN 1995-1-2 are limited to standard fire exposure. As shown by heat transfer calculations, the effective thermal conductivity of the char layer is strongly dependent on the charring rate and therefore varies during a natural fire scenario. It has also been shown that char oxidation during the decay phase in a natural fire has a significant influence on the temperature development in the timber member, since char surface temperatures exceed the gas temperature in the compartment or furnace. Using increased effective gas temperature as thermal action during the decay phase, and varying conductivity values for the char layer, fairly good agreement could be obtained regarding the temperature development in the timber member and the char depth. Copyright © 2005 John Wiley & Sons, Ltd. [source] Structural fire design according to Eurocode 5,design rules and their backgroundFIRE AND MATERIALS, Issue 3 2005Jürgen KönigArticle first published online: 18 NOV 200 Abstract This paper gives a review of the design rules of EN 1995-1-2, the future common code of practice for the fire design of timber structures in the Member States of the EU and EFTA, and makes reference to relevant research background. Compared with the European pre-standard ENV 1995-1-2, the new EN 1995-1-2 has undergone considerable changes. Charring is dealt with in a more systematic way and different stages of protection and charring rates are applied. For the determination of cross-sectional strength and stiffness properties, two alternative rules are given, either by implicitly taking into account their reduction due to elevated temperature by reducing the residual cross-section by a zero-strength zone, or by calculating modification factors for strength and stiffness parameters. Design rules for charring and modification factors are also given for timber frame members of wall and floor assemblies with cavities filled with insulation. A modified components additive method has been included for the verification of the separating function. The design rules for connections have been systemized by introducing simple relationships between the load-bearing capacity (mechanical resistance) and time. The code provides for advanced calculation methods for thermal and structural analysis by giving thermal and thermo-mechanical properties for FE analyses. The code also gives some limited design rules for natural fire scenarios using parametric fire curves. Copyright © 2004 John Wiley & Sons, Ltd. [source] Anwendung von massiv paralleler Berechnung mit Grafikkarten (GPGPU) für CFD-Methoden im BrandschutzBAUPHYSIK, Issue 4 2009Hendrik C. Belaschk Dipl.-Ing. Berechnungsverfahren; Brandschutz; calculation methods; fire protection engineering Abstract Der Einsatz von Brandsimulationsprogrammen, die auf den Methoden der Computational Fluid Dynamics (CFD) beruhen, wird in der Praxis immer breiter. Infolge der Zunahme von verfügbarer Rechenleistung in der Computertechnik können heute die Auswirkungen möglicher Brandszenarien nachgebildet und daraus nützliche Informationen für den Anwendungsfall gewonnen werden (z. B. Nachweis der Zuverlässigkeit von Brandschutzkonzepten). Trotz der erzielten Fortschritte reicht die Leistung von heute verfügbaren Computern bei weitem nicht aus, um einen Gebäudebrand mit allen beteiligten physikalischen und chemischen Prozessen mit der höchstmöglichen Genauigkeit zu simulieren. Die in den Computerprogrammen zur Berechnung der Brand- und Rauchausbreitung implementierten Modelle stellen daher immer einen Kompromiss zwischen der praktischen Recheneffizienz und dem Detailgrad der Modellierung dar. Im folgenden Aufsatz wird gezeigt, worin die Ursachen für den hohen Rechenbedarf der CFD-Methoden liegen und welche Problemstellungen und möglichen Fehlerquellen sich aus den getroffenen Modellvereinfachungen für den Ingenieur ergeben. Darüber hinaus wird ein neuer Technologieansatz vorgestellt, der die Rechenleistung eines Personalcomputers unter Verwendung spezieller Software und handelsüblicher 3D-Grafikkarten massiv erhöht. Hierzu wird am Beispiel des Fire Dynamics Simulator (FDS) demonstriert, dass sich die erforderliche Berechnungszeit für eine Brandsimulation auf einem Personalcomputer um den Faktor 20 und mehr verringern lässt. Application of general-purpose computing on graphics processing units (GPGPU) in CFD techniques for fire safety simulations. The use of fire simulation programs based on computational fluid dynamics (CFD) techniques is becoming more and more widespread in practice. The increase in available computing power enables the effects of possible fire scenarios to be modelled in order to derive useful information for practical applications (e.g. analysis of the reliability of fire protection concepts). However, despite the progress in computing power the performance of currently available computers is inadequate for simulating a building fire including all relevant physical and chemical processes with maximum accuracy. The models for calculating the spread of fire and smoke implemented in the computer programs therefore always represent a compromise between practical computing efficiency and level of modelling detail. This paper illustrates the reasons for the high computing power demand of CFD techniques and describes potential problems and sources of error resulting from simplifications applied in the models. In addition, the paper presents a new technology approach that significantly increases the computing power of a PC using special software and standard 3D graphics cards. The Fire Dynamics Simulator (FDS) is used as an example to demonstrate how the required calculation time for a fire simulation on a PC can be reduced by a factor of 20 and more. [source] Investigation of the Development of Conflagration of Solid Material via Analysis of Coupled Heat, Mass and Momentum TransportCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 2 2009U. Krause Abstract A mathematical model is presented for the transport of heat, mass and momentum transfer through a porous medium to simulate the chain of events from self-heating, subsequent self-ignition to smouldering fire propagation and burn-out of combustible fractions. The model comprises both diffusive and convective transport. The chemical reaction sub-model includes solid fuel decomposition and the combustion of char, carbon monoxide and hydrogen. Furthermore, biological processes, which may be a precursor of self-heating and vaporization/condensation of moisture, are also included into the model. All input data necessary for implementing the model have been determined experimentally. The model has been validated against laboratory scale self-ignition and smouldering propagation experiments and then applied to predictions of different fire scenarios during storage of bulk materials. [source] | |||||||||||||