Establishing safety distances for wildland fires

In wildland fires, safety zones should be considered concerning people who are intervening in the emergency or attempting evacuation. To establish such zones, the solid flame model, together with the view factor calculated from a previously selected equation, was used to estimate the thermal radiation emitted by the flame front of a wildland fire. After determining the flame heights yielded by the 13 fuel types in the Rothermel classification for surface fires, and for crown fires in various Mediterranean forests, the thermal radiation was calculated for each scenario as a function of the distance. These data, together with threshold values for the vulnerability of people (protected or unprotected) and houses to thermal radiation, allowed for a set of safety distances for different situations to be obtained. These safety distances can be applied both in territory planning and in emergency situations.     

Thermal exposure from large scale ethanol fuel pool fires

The growing use of ethanol as fuel for combustion engines has dramatically increased the need for large scale storage of ethanol in tanks. There are new risks related to fires in storage tanks having larger volumes. Very little experimental data exist to support risk assessments regarding emitted radiation and burning rate for large pool fires. Experience from small scale tests show that the exposure to nearby surroundings is less for alcohols than for hydrocarbon fuels like gasoline and these results are often extrapolated to fires of large sizes. This paper describes the results of two pool fires conducted within the frame of the ETANKFIRE project, one with 97% ethanol and 3% gasoline and the other with 85% ethanol and 15% gasoline, both with a surface area of 254 m². The results show, contrary to experience from small scale pool fires, that the exposure to nearby surroundings is much larger for ethanol-rich fuels compared to the calculated radiative heat flux from a pure gasoline fire of same fuel area.     

Limiting case fires arising from fuel tank/pipeline ruptures

Liquid and liquefied gas fuels will continue to play a predominant role in the energy picture of this country. Critical safety problems arise in connection with their storage and transportation. The problems become intrinsically serious in connection with military and civil aircraft operations, and accidents involving them. In an attempt to classify the varieties of fires which could arise with fuel tanks, an examination of such variables as the rupture size and location, pressure difference across the rupture, thermal properties, physicochemical properties, etc., is made to identify the circumstances when a pool fire, a flowing film fire, a falling film fire, a spray fire, and a gas fuel jet fire would evolve. Based on this framework, a review of scientific literature is made to seek an understanding of the basic heat and mass transfer phenomena involved in the associated diffusive combustion process. Areas in need of future scientific research are identified.     

Extinguishing agents for hydrocarbon fuel fires

This paper is a review of the extinguishing agents available for combating hydrocarbon fuel fires. The original work was done to set the state for a proposed laboratory test procedure to evaluate all known fire extinguishing agents that have been recommended for use in controlling and extinguishing aircraft fuel fires. This paper was the basis of the remarks made by the author during the Civil Aviation Workshop session of the National Fire Protection Association's 72nd Annual Meeting in Atlanta, Ga., on May 21, 1968.     

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.     

Spilled liquid fires in tunnels

The study focuses on release of liquids inside tunnels from tankers containing dangerous good. Experiments and analysis from large scale tests are presented. The tests include different leakage rates, leakage type, liquids, spillage sizes on sloping surfaces and heat release rates. Models for estimation of leakage rates, spillage sizes and heat release rates for different scenarios are presented. The results are important to use in the design of active fire protections systems in tunnels including ventilation, fixed fire-fighting and drainage systems.     

Suppression of sodium fires with liquid nitrogen

Sodium has unusual fire hazards, including autoignition when heated in air or exposed to liquid water. Owing to limitations of existing suppression agents for sodium pool fires, suppression using liquid nitrogen (LN₂) is examined here. Sodium pools of 5–80 g were heated in stainless steel beakers. At about 290 °C, pool surface autoignition occurred and caused a rapid pool temperature increase. Vapor phase combustion occurred when the pools reached 320–450 °C, ultimately leading to pool temperatures up to 700 °C. For suppression tests, LN₂ delivery (at 2.7 g/s) began when the fires became fully-developed, near a pool temperature of 600 °C. Liquid nitrogen was found to be an effective suppression agent. The minimum amount of LN₂ required to suppress a fully-developed sodium pool fire was found to be about three times the initial sodium pool mass.     

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.     

Combustion properties of large liquid pool fires

Data from a number of large liquid pool fire experiments, recorded at the Fire Research Institute of Japan over more than a dozen years, were gathered and compiled. Burning rate and radiative outputs of gasoline, kerosene, and heptane were of primary interest. It is difficult to deduce the behavior of large fires from data on small fires because of the likelihood of decreasing combustion efficiency and heavy soot generation with resulting blockage of radiation. The data compiled here is possibly the largest body of data available for study on large pool fires.     

火源—竖井间距对自然通风隧道火灾烟气流动特征的影响

通过数值计算,研究顶部开口自然通风隧道火灾火源–竖井间距对烟气流动特征与竖井排烟效率的影响。考虑因素有火源–竖井间距、竖井断面尺寸。结果表明：随着火源–竖井间距的增大,竖井前方来流烟气的质量流量增大,且竖井的排烟效率逐渐降低,竖井内空气卷吸量减少;当火源–竖井间距较小时,竖井更有利于排出更多的热量,竖井后方的温度降低幅度更大,烟气可以被控制在更小的范围内。此外,随着竖井截面尺寸的增大,竖井的排烟效率增加,且增大竖井的宽度更有利于增加竖井的排烟量。因此建议当相邻竖井的间距较大时,可适当增加竖井的截面尺寸和竖井高度。     

Internal separation distances for underground explosives storage in hard rock

Most recent studies on underground explosives storage have focused their attention on external safety distances, mostly inhabited distances for airblast, debris, and ground shock. Internal distances in prevailing codes generally deal with the need to prevent sympathetic detonation as a result of propagation by rock spall impact, or to prevent damage in an adjacent chamber in the event of an accidental explosion. For complex facilities, guidelines on separation requirements are often lacking. Also, there are several inconsistencies in the current separation requirements. This paper attempts to fill in the gap and rationalise the separation requirements for the various components of an underground storage facility. Recommendations will be made based on a comprehensive review of tunnel damage and results from large-scale tests.     

A convective model for laboratory fires with well-ordered vertically-oriented fuel beds

Several studies in the literature explore the connection between rate of spread (ROS) and wind in wildland fires. These studies show very different positions about the role of radiation and convection as heat transfer mechanisms. In the case when the fuel bed is well-ordered and vertically-oriented, there seems to be a consensus leading to suggest that convective heating is the dominant heat transfer mode in that case. The purpose of this work is to propose a convective semi-physical model for the behaviour of the rate of spread in wind, when the fuel bed is vertically-oriented. Due to a specific fuel bed arrangement, flame radiation –i.e. radiation from the part of the flame above the vegetal stratum– is neglected. Only horizontal radiation from the fuel burning particles area and convective heating are taken into account. Convective heat transfer is assumed to be the primary heat transfer mechanism. The proposed model is confronted to 172 laboratory fires with a wide range of fuel characteristics. The predicted results are also compared with two simplified models from the literature. Statistical tools are used to check the agreement between the predicted ROS and the observed one where a strong agreement is generally observed, irrespective of fuel bed characteristics.     

Extinction of gas and liquid pool fires with water sprays

Extinction in open space of flames from pool fires by downwardly directed water sprays has been investigated on two linear scales, one three times larger than the other. Circular pool fires were employed as fire sources, mostly in the form of gas discharge (methane) from a horizontal sand surface but also, to a limited extent, in the form of heptane pools. The results are presented in normalized plots based on scaling theory verified in a previous study. Extinction data from the methane fires are insensitive to the initial spray angle of the nozzle discharge. The data are consistent with an engineering relation showing extinction water flow rate approximately proportional to an effective nozzle diameter, and to the 0.4-power of both nozzle height and freeburn heat release rate. This result has been interpreted to indicate that spray-induced dilution of the flammable gas is a major factor in extinguishing fires from gaseous discharge. Extinction data of liquid pool fires from this study (n-heptane) and previous investigations (gasoline, JP-5) are consistent with the methane data, except for somewhat higher water rates at extinction.     

Flame radiation from polymer fires

Enclosure fires can be divided into two ventilation regimes: well-ventilated and under-ventilated combustion. The influence of fire ventilation on flame radiation is very important in enclosure fires especially for under-ventilated conditions. An approximate model for predicting flame radiation for both well- and under-ventilated fires is proposed on the basis of the Γ-correlation, in which the role of flame sootiness and heat release is considered. This paper is an extension of work performed earlier and reported in Tewarson et al. (Combustion and Flame, 95 (1993) 151-169)[1]. The results are calculated for several typical polymers, and the relationship between the flame radiant fraction and the fuel’s smoke-point has been examined. Additionally, flame radiation is predicted by the slightly modified Global Flame Radiation (GFR) Model of de Ris and Orloff. The comparisons between experimental and predicted data are satisfactory. This study attempts to provide: (1) a deeper scientific understanding of the effect of ventilation conditions on flame radiation, and (2) available correlation, for the analysis of enclosure fires.     

Fighting building fires with liquid nitrogen: A literature survey

Brief reference is made to inert gases having some potential for fighting building fires and it is suggested that nitrogen, or to be more accurate the massive use of liquid nitrogen, stands out as being the most promising for immediate consideration. Reports and publications produced in the last twenty years on the use of liquid nitrogen are reviewed. It is concluded that its effectiveness and the elimination of the water damage often resulting from conventional firefighting make it desirable for firefighters to gain experience in its use with a view to determining whether or not it should supersede the use of water in fighting many building fires.     

The use of ground cover materials to suppress fuel fires at airports

Crushed rock has demonstrated a capability for retarding flame spread in hydrocarbon fuel fires. What are the effects of rock size, depth of fuel surface below ground cover surface, and fuel flash point in flame suppression?     

圆形航空煤油池火脉动频率实验研究

对航空煤油池火准稳定状态下火焰脉动频率进行实验研究,油盘直径分别为0.10、0.15、0.20m.分析池火火焰周期性的动态演化过程.应用自编的MATLAB程序,处理分析火焰连续图像序列,获得了火焰脉动频率.对火焰脉动频率的实验结果进行回归拟合,给出池火脉动频率与油盘直径的关系式.分析预测模型比前人的预测结果略小的原因.     

从仓储库房火灾中获得的经验和教训

历史的经验表明,当灾害性火灾发生后,人们对火灾进行调查所获得的经验和教训推动了仓储库房防火的进步。下面讨论由这种方式得出的经验和教训。1自动喷水灭火系统的设计应和火灾危险相匹配该教训来源于含有可燃物质的气溶胶罐仓库的自动喷水灭火系统的防火评估。1978年在新泽西