A Case Study of a Community Affected by the Witch and Guejito Wildland Fires

Wildland-urban interface (WUI) fires occur when fire spreads through both wildland and community (structures and vegetation) fuels. These fires are capable of causing significant destruction to both the built and the natural environments. When these fires occur under extreme fire danger conditions (e.g., high winds, low humidity) and in areas of significant population (e.g., San Diego, California) firefighters, and other emergency responders, are significantly challenged by the combination of firefighting and aiding the public. This paper presents the results of an in-depth case study of a community of 274 residences which was subjected to two wildland fires (within 2.5 h of each other) during the October 2007 firestorm in southern California. A significant amount of effort was spent obtaining information from residents and emergency responders to determine the fire spread timeline, structure ignition mechanisms, and defensive actions. Of the 274 residences, 245 were within the fire perimeter, 74 were destroyed, and 16 were damaged. When the first fire front arrived, the rate of structure ignitions peaked at 21 per hour. Direct and indirect ember, or firebrand, attack was responsible for the ignition of 2/3 of the destroyed homes. Defensive actions were taken on one of every three homes. Of the 16 damaged homes, 15 were successfully defended. Further study of this community is ongoing to investigate what currently recommended pre-fire hazard reduction actions could be, and were, implemented and their effectiveness at reducing the likelihood of structure ignition.     

Theoretical Analysis and Experimental Study on Whirling Flames in Enclosure Fires

Whirling flames are not commonly observed in enclosure fires, but some special hazards will be induced for their characteristics once they occur. Employing the theories of vorticity transport and fire dynamics, the formation mechanism of whirling flames in enclosure fires has been analyzed, and the factor expression governing the formation of whirling flames occurring in single rooms with ceiling and lower openings, which are familiar to us in industrial buildings, has been deduced. Using a small-scale firebox with a lower door and a ceiling opening, the experiments of whirling flames in enclosure fires were carried out. Based on the experimental results, the characteristics of whirling flames in enclosure fires were studied, and the basic parameters of fires with and without whirling flame were compared. Combining the results of the theoretical analysis and experimental study, the formation criterion of swirling flames in enclosure fires were derived. Furthermore the reasons that whirling flames cause increases in some parameters, such as hot gas layer temperatures and floor radiant heat flux, were analyzed.     

Full-Scale Experimental Investigation to Quantify Building Component Ignition Vulnerability from Mulch Beds Attacked by Firebrand Showers

Structure ignition by wind-driven firebrand showers is an important fire spread mechanism in large outdoor fires. Experiments were conducted with three common mulch types (shredded hardwood mulch, Japanese Cypress wood chips, and pine bark nuggets) placed adjacent to realistic-scale re-entrant corners. In the first series of experiments, mulch beds were placed adjacent to a re-entrant corner constructed with wood studs and lined with oriented strand board (OSB) as the sheathing. The premise behind conducting experiments with no siding treatments applied was predicated on the notion that bare OSB mulch contact would be a worst-case scenario, and therefore, a wall assembly in the most vulnerable state to mulch ignition. In the second series of experiments, vinyl siding was applied to the re-entrant corner assemblies (wood studs/OSB/moisture barrier/vinyl siding), and the influence of vertical separation distance (102 mm or 203 mm) on wall ignition from adjacent mulch beds was determined. The vertical separation distance was maintained by applying gypsum board to the base of the re-entrant corner. The siding itself did not influence the ignition process for the mulch beds, as the mulch beds were the first to ignite from the firebrand showers. In all experiments, it was observed that firebrands produced smoldering ignition in the mulch beds, this transitioned to flaming ignition, and the re-entrant corner assembly was exposed to the flaming mulch beds. With no siding treatments applied, the flaming mulch beds ignited the re-entrant corner, and ignition was observed to propagate to the back side of re-entrant corner assembly under all wind speeds (6 m/s to 8 m/s). With respect to the re-entrant corners fitted with vinyl siding, the mulch type, vertical separation distance, and wind speed were important parameters as to whether flaming ignition was observed to propagate to the back-side of a re-entrant corner assembly. Mulches clearly pose an ignition hazard to structures in large outdoor fires.     

清明时节活消防

2008年2月28日,阿根廷南部丘布特省埃斯克尔附近发生森林火灾,迅速蔓延的大火已造成途700多公顷的森林被烧毁;3月2日,智利第五大区瓦尔帕莱索市附近发生森林火灾,已导致3313公顷森林被毁……近期世界各地的森林火灾不禁使人联想到4月4日—中国传统节日“清明”,防火护林的警钟再次于耳畔敲响。     

隧道火灾一氧化碳浓度及温升分布试验研究

为了掌握长大公路隧道内的火灾行为,提升特长公路隧道的火灾安全性,进行了水平通道中不同纵向通风强度下,一氧化碳浓度和温升空间分布关系的1∶6大尺寸火灾模型试验,并与Newman的研究结论进行了对比。试验在长66 m,宽1.5 m,高1.3 m的模型隧道中进行的。研究结果发现,Newman的研究结论并不适用于所有通风条件。一氧化碳浓度和温升的纵向分布和竖向分布都不尽相同。在纵向分布方向,烟流的温升随着远离火源的纵向距离的增加而显著衰减,然而一氧化碳浓度却并没有随着纵向距离的增加而发生改变。一定强度的纵向通风使得温升沿纵向的衰减率变得缓慢,然而,纵向通风对一氧化碳浓度的纵向分布特性影响甚微。在无纵向通风的情况下,相对于温升来讲,一氧化碳浓度随高度减小而衰减的速率明显比温升要慢。然而,随着纵向通风风速的增加,一氧化碳浓度和温升的竖向分布呈现出了很好的相似性。     

Experimental Study on the Burning Behavior of Pool Fires in Rooms with Different Wall Linings

An experimental test series, comprising 10 experiments with varying pool sizes, lining materials and amounts of liquid burning, was conducted under free burn and room burn conditions. The thermal feedback from the enclosure (ISO 9705 Room Corner Test facility) enhanced the burning rate of the pools and resulted in a thermal runaway in some of the runs. The onset of the thermal runaway, which can be associated with flashover, varied with all the input parameters. The lining with the lowest thermal inertia lead to the fastest increase in the heat release rate (HRR) in the enclosure and caused flashover in the shortest time. Given the profound difference between the enclosure tests and the free burn tests and also between enclosure tests with different linings, it is recommended to show great caution if free burn tests are to be used in design fire scenarios.     

上海消防置置上天入地“奇兵”降火魔揭秘

目前，上海有高层建筑6000多幢、地下空间3000多万平方米、轨道交通近400公裹，还有世界级的化工基地、造船基地和物流中心。这些既是城市高度繁荣的标志，也是世界性的消防安全难题。针对这些灭火救援难题，市消防局在全国率先组建了高层、地铁、化工、船舶等灭火救援专业队伍。     

Pulsations During Fires in Tunnels

The existing theoretical modelling of thermoacoustic oscillations has been studied and applied to the case of tunnel fires. The assumptions of the theoretical model were reviewed. It was found that several assumptions are not applicable to tunnel fires and, hence, suggestions for improvement are given. The correlation which expresses the starting conditions for thermoacoustic oscillations is analysed and dependencies on different parameters are presented. The pulsations documented during the large-scale tests in the Runehamar tunnel in 2003 have also been further analysed. The measurements were compared to the theoretical limiting curve for oscillations, showing good agreement. To further study thermoacoustic oscillations in tunnels, more detailed tests in a model-scale tunnel (1:100) were performed. These tests focused on the circumstances which are required to create thermoacoustic oscillations, i.e. the fire was located at different positions along the tunnel and the air flow rate was varied. The tunnel had a length of 4 m, was 8 cm wide and 6 cm high. The results were in good accordance with the theoretical modelling but showed deviations which were most obvious at very low and high air velocities. Both the starting conditions for thermoacoustic oscillations and cases where the thermoacoustic oscillations suddenly stopped, were observed. These findings led to identification of several points in the theoretical model which need to be improved, and to the development of a strategy to avoid such pulsation in fires.     

Experimental Investigation of Suppression of 18650 Lithium Ion Cell Array Fires with Water Mist

Fire Technology - The effectiveness of suppression of lithium ion battery, LIB, fires with water mist was investigated experimentally using a previously developed bench-scale wind tunnel. The...     

A Physical Model and Improved Experimental Data Correlation for Wind Induced Flame Drag in Pool Fires

The flames over a burning liquid fuel are observed to spill over the downwind edge of the liquid pool in a wind. Empirical correlations in the literature relate the total base dimension of the fire (diameter + the spill over) with the wind Froude number. This leads to erroneous and physically incorrect (negative) value for the flame spillover at low wind speeds and/or in large diameter fires. The data from laboratory scale (0.1–0.6 m) to field scale (up to 35 m) fires of different hydrocarbon fuels on the wind induced flame “drag” or “spillover” were re-examined. The ratio of the flame spillover distance with the pool diameter is seen to vary in direct proportion to the square root of the Froude number but with different proportionality constants for different fuels. A physical model was developed to analyze the phenomena that occur at the base of a pool fire subject to a wind. This model indicates that the non-dimensional downwind flame spillover distance is directly proportional to the square root of the Froude number, inversely proportional to the square root of the dimensionless heat of combustion of the fuel and directly proportional to the 1/4th power of the ratio of vapor density to air density. Available experimental data are synthesized into a single correlation when plotted on the basis of the non-dimensional parameters from the model. This correlation includes the Froude number, the Damkohler number (dimensionless heat of combustion of the fuel), the wind flow Reynolds number and the fuel vapor-to-air density ratio.     

气象因素对南昌城市火灾的影响

火灾是发生比较频繁且危害严重的灾害之一，每年都会造成巨大的经济损失和人员伤亡。据统计，1997—2006年，全国共发生各类火灾209．2万起，其中死亡24656入、伤35986入，直接财产损失达142．96亿元。火灾的起因错综复杂，既有人为的因素，也与特定的客观条件有关。     

Typification of Fires in Buildings in Spain

Although the Dirección de General de Protección Civil (DGPC), an agency of the Spanish government, has been responsible for the collection of data and the statistical analysis of fires since 1985, it has not as yet issued any reports. It is true that a couple of studies have been made, but in neither case did they use a standardized methodology but relied simply on the heterogeneous information provided by the fire brigades which cooperated in the studies. At that time Spanish fire brigades did not have special units for professional fire investigation, nor was the information derived from standardized methodologies suited to research purposes. In addition, information was extremely scarce and basic, focussed only on the fire, the use of the building and personal data of the victims. In this context, the project for a Fire Investigation Unit in the Fire Brigade of Málaga (the sixth largest Spanish province in inhabitants) was set up. Although inspired in the methodologies used in the USA and in the UK, the aim was to create a customized methodology for the first scientific investigation of fires in Spain. Our research was conducted in 2007. Using the methodologies of the USA and the UK, our own methodological approach and the Spanish regulations, we drew up a questionnaire with 110 variables arranged into 6 modules. We studied 96 fires out of the 154 emergency fire calls received in 2007, having omitted some emergency calls for various reasons. Our results revealed that it was necessary to generalize the installation of fire extinguishers in residential buildings, to train the general public in the use of these devices, to promote the use of fire and smoke detectors in residential buildings, to encourage the inspection and control of old electric installations and to monitor the new installations, to generalize the implementation of emergency and evacuation plans and to design new systems and materials for the cabinets where hand-held extinguishers are stored.     

冷弯型钢冷弯效应试验研究

通过冷弯矩形管中截取的板件和短柱以及相应母材板件试样的冷弯效应试验 ,研究厚壁冷弯型钢冷弯效应对钢材强度的影响。根据板件试样的实测数据 ,分别用北美、澳大利亚和新西兰及我国相关规范建议的公式计算全截面屈服强度 ,并将计算结果与短柱试验结果进行比较分析。提出修改我国现行的冷弯薄壁(厚度≤ 6mm)型钢强度设计规范公式 ,得到冷弯厚壁型钢考虑冷弯效应的强度设计建议公式。     

半敞开式隧道火灾通风研究

采用CFD方法运用κ-ε双方程模型对半敞开式隧道着火时烟气扩散情况进行模拟,比较不同季节时的自然通风效果.结果表明,冬夏两季时隧道采用自然通风的排烟模式是切实可行的,都能起到很好的排烟作用.火灾前期烟气扩散速度远大于火灾后期,冬季烟气水平扩散速度高于夏季,但烟气沉降冬季比夏季严重,且冬季自然排烟效率比夏季提高了3.5%;夏季隧道顶部最高温度高于冬季,且火源两侧高温区域大于冬季.     

汽车油路系统火灾分析

本文通过对辖区内近年来车辆油路火灾的原因调查,分析了导致该类火灾的几种可能因素.文中提出了从勘察汽车供油系统变化痕迹来判断油路所发生故障的勘查手段,简要得出在调查车辆火灾原因和预防车辆火灾事故的一些做法。