添加剂对细水雾高原灭火性能影响的试验研究

为了发展适应于高原地区低压低氧环境下的火灾防治技术,基于高原地区建筑特点和防火重要性,建立用细水雾灭火技术来防治高原建筑火灾的方法。在中国拉萨进行细水雾添加剂灭火模拟试验,研究添加剂FeCl_2和NaCl对细水雾熄灭汽油和柴油池火的灭火性能的影响,分析试验过程的温度、烟气、辐射热流变化规律。结果表明,在拉萨地区低压低氧的环境下,分别含质量分数为1.5%FeCl_2和10%NaCl的细水雾对柴油池火的灭火效率较高,而汽油池火初期受到了抑制,但随后出现了强化现象,最终未被熄灭。含添加剂FeCl_2和NaCl的细水雾对高原地区柴油池火有较高的灭火效率。     

溴氟丙烯/13X沸石复合粉体抑制汽油火的试验研究

为提高粉体灭火介质的灭火性能,基于粉体灭火剂在火灾防治领域的重要性,通过减压吸附的方法,将洁净高效的气体灭火剂溴氟丙烯负载在13X沸石的孔洞之中,形成气-固复合粉体灭火剂。采用X-射线衍射仪、扫描电镜等对复合粉体的结构和组分进行表征。通过模拟试验研究溴氟丙烯含量不同的复合粉体对汽油油池火的灭火效果,并和普通的干粉灭火剂进行对比。结果证明,溴氟丙烯和13X沸石所形成的气-固复合粉体灭火剂针对汽油油池火具有很好的灭火性能,在同样的试验条件下,其灭火时间和灭火剂用量远少于普通的干粉灭火剂,且随着复合粉体中溴氟丙烯的含量增加,复合粉体的灭火性能逐渐提高。     

复合干粉灭火剂抑制食用油火的试验研究

为改善普通碳酸氢钠干粉灭火剂(BC干粉)抑制食用油火时抗复燃性较差的不足,选择聚磷酸铵、溴化钾和一水合草酸钾作为添加剂,与普通BC干粉灭火剂混合配制成复合干粉灭火剂。通过全尺度模拟试验研究各种复合粉体对食用油火的灭火效果及其抗复燃性能。结果证明,普通BC干粉与一水合草酸钾复配而成的复合粉体针对食用油火的灭火效果和抗复燃性能在几种粉体中最佳。根据试验数据和各粉体的理化特性,对4种粉体的灭火效果差异作了详细的分析和讨论。     

泡沫灭火剂对车用汽油油盘火的灭火性能研究

汽油易挥发且闪点低,火灾危险性极大,且理化性能与标准燃料存在较大差异,有必要评估当前市售泡沫灭火剂对汽油的灭火性能。通过4.52 m 2油盘火试验,对水成膜泡沫灭火剂、抗溶水成膜泡沫灭火剂、氟蛋白泡沫灭火剂及抗溶氟蛋白泡沫灭火剂的灭火性能进行评估研究,并与标准燃料油盘火进行对比,结果表明抗溶水成膜泡沫灭火剂对车用汽油火的灭火效能最佳,石化企业和消防救援队伍在处置汽油火灾时应优先考虑使用抗溶水成膜泡沫灭火剂。此外,车用汽油比标准燃料的灭火难度更大,石化企业可适当提高固定泡沫灭火系统的设防标准。     

磷酸铵盐亚纳米粉体灭火性能实验研究

使用溶剂-非溶剂法制备了粒径达到亚纳米量级（300nm-500mm）的磷酸铵盐灭火剂,建立了1．2m×1．2m×1．2m的小尺度灭火实验平台,开展了灭油池火和木垛火的全淹没灭火实验,对磷酸铵盐亚纳米粉体的灭火性能进行了研究,并与普通磷酸铵盐粉体的灭火性能进行了比较。实验结果显示磷酸铵盐亚纳米粉体的灭火性能要明显高于普通粉体,并且在低压下就可以获得很好的灭火果。工作压力的增加会缩短粉体的灭火时间,但是对于磷酸铵盐亚纳米粉体灭木垛火的情况,由于灭火时间相差示大,反而会导致灭火剂用量增加。     

高原与平原地区油池火燃烧特性对比试验研究

为研究高原环境液体燃烧时火焰特性参数与平原地区的差异,在拉萨和合肥进行了汽油油池火燃烧试验.结果表明,在燃料类型和油盘尺寸相同的条件下,两地汽油和柴油的质量燃烧速率之比等于大气压力之比,且高原地区的汽油火火焰比平原地区细长. 随着高度的增加,高原地区羽流中心温升的下降幅度减小,且幅度小于平原地区. 相同燃烧速率下,高原地区小尺寸油盘的油池火高度和中心温度大于平原地区,McCaffrey羽流温升公式不适用于计算低压环境下小功率火源.研究表明,由于氧气含量和压力的不同,高原地区燃料的燃烧特性与平原呈现不一样的规律.进一步研究环境压力对燃料燃烧特性的影响规律,可为研究高原火灾发展规律及火灾防治技术提供理论指导.     

改性超细粉体灭火性能模拟实验研究

针对新一代超细高效粉体灭火剂的要求,构建了一套小型固定式粉体灭火装置,对3种粉体的灭火性能进行对比研究,通过扫描电子显微镜(SEM)观察粉体颗粒的粒径分布和表面形态,研究了粒径等因素影响粉体灭火性能的规律,指出了改性前后粉体灭火时间不同的原因.实验结果表明,与普通干粉相比,经改性细化的粉体的灭火时间缩短了1/2,灭火性能显著提高.     

超细粉体三相泡沫灭火剂热稳定性研究

为探讨超细粉体的加入对水基泡沫灭火剂油面热稳定性的影响,用自行设计的小尺寸可视化油池,完成不同粉体类型、不同添加量的泡沫油面热稳定性试验。观察高温条件下三相泡沫的形态变化过程,并用热电偶测定试验过程中的油品温度,优选2种适合制备防灭火三相泡沫的超细粉体。结果表明:向泡沫灭火剂中加入超细粉体,可使其在高温下的稳定时间延长10倍以上;对于空心玻璃微珠和炭粉,泡沫灭火剂的油面热稳定性随粉体添加量的增加而增强,发泡倍数随粉体添加量增加而减小,炭粉对发泡性能的影响更为显著,空心玻璃微珠和炭粉的最优添加量(质量分数)分别为11.2%和13.2%;高温条件下,粉体在泡沫表层形成致密外壳,阻碍油品与环境的传热传质过程,防止油品复燃。     

高原火羽流温升特性与模型对比研究

针对高原地区火羽流中心线的温升特性,在3个小尺寸火源试验结果的基础上,将火源功率进行无量纲化,运用CFD模拟软件进行了大规模的数值模拟并对模拟结果进行了分析.通过将模拟结果与两大经典羽流模型Heskestad和McCaffrey预测模型进行比较,分析了这两大模型在高原地区低压低氧环境下的适用性,并对后者在海拔4000m高原处进行了修正,以满足其在高原地区的适用性.     

载铁改性沸石粉体抑制甲烷/空气扩散火焰试验研究

为发展洁净高效新型粉体灭火介质,以沸石粉体为基体,采用盐酸活化和氯化铁溶液浸泡方法制备载铁改性沸石粉体灭火剂。采用X-射线衍射仪(XRD)、扫描电镜(SEM)和X-射线荧光光谱仪(XRF)等仪器对该粉体灭火剂的结构和形貌进行表征。通过小尺度的杯式燃烧器试验研究载铁沸石粉体对甲烷/空气扩散火焰的灭火效果,并和未改性沸石粉体进行对比。试验结果表明,载铁改性沸石粉体灭火剂的灭火效能明显高于未改性沸石粉体。改性沸石灭火效能提高,主要是由于所负载的铁离子在火焰中转化为活性铁原子,参与清除火焰自由基的催化反应。     

高原乙醇油池火燃烧特性实验研究*

为研究低压条件下油品燃烧特性,以乙醇油池火为研究对象,搭建高原油池火实验平台,研究不同油盘直径下乙醇油池火燃烧规律,分析燃烧速率、火焰高度和火焰脉动等参数随时间的变化规律。研究结果表明:低压条件下的乙醇油池火,燃烧速率小于同等尺度常压条件下的油池火燃烧速率;乙醇油池火的燃烧速率随油盘直径增加变化不明显;火焰高度随油池直径增加呈现显著上升趋势,并拟合推导出适用于低压乙醇池火的火焰高度公式;火焰脉动频率随油池直径增大而减小,并给出火焰脉动与油池直径的经验公式。研究结果可丰富低压乙醇燃烧的油池火实验数据,为低压乙醇油池火的风险评估提供参考。     

A study of the probability distribution of pool fire extinguishing times using water mist

Water mist, a replacement for Halon gaseous agents in fire fighting, has been studied for decades. However, the fire-extinguishing reliability of water mist is debated. For example, there are significant differences in extinguishing times between tests conducted under the same conditions, and water mists have difficulty extinguishing small fires. To date, no study of the probability distribution of extinguishing times has been reported. In this study a statistical analysis of the extinguishing time distribution of pool fires extinguished using water mist is presented. The fire sources were circular/square stainless steel pans with gasoline, diesel, ethanol or daqing RP-3 as fuel. Two types of extinguishing scenarios were observed. In one situation, the fire was extinguished via a blow off process, when the flames had not yet been suppressed. Flame cooling is the primary fire extinguishing mechanism; the mass loss rate and combustion heat of the fuel are two key factors. In the other situation, the fire was initially suppressed and subsequently extinguished after a long suppression stage. Surface cooling is the primary fire extinguishing mechanism; the flash point of the fuel is the key factor.     

An experimental study on the burning rate of a continuously released n-heptane spill fire on an open water surface

Spill fires are common during oil product storage and transportation after a loss of containment. Since the burning fuel is moving and the fuel depth is quite shallow, the burning rate in a spill fire is different from that of a pool fire with a static burning zone. Unlike pool fires, which have been studied for decades and have well-established correlations for burning rate, research on spill fires is inadequate. In this paper, continuously released n-heptane spill fire experiments were conducted on open water surfaces with varying fuel discharge rates. The pool diameters were measured, and the spill fire burning rates were estimated based on a dynamic balance between fuel supply and combustion. The burning rates in n-heptane pool fires from the literature were reviewed and compared with the estimated burning rates in spill fires of the same dimension. The spill fire burning rate was found to be close to that in a pool fire during the initial burning phase but lower than that in a bulk burning pool fire and that in a “fuel-level-controlled” pool fire. The distinction between the burning rates of spill fires and pool fires is explained by the heat balance analysis of the fuel layer. A model for the spill fire burning rate was proposed accordingly. The results calculated with the presented model are closer to the measured data than those calculated with pool fire models.     

Characteristics of large cooking oil pool fires and their extinguishment by water mist

Large cooking oil pool fires, occurring in industrial oil cookers, present a severe hazard to food processing plants due to their size and the large amount of hot oil involved. This paper reports a series of full-scale fire experiments conducted in a large industrial oil cooker mock-up. The characteristics of large cooking oil pool fires and the effect of oil depth and hood position in the oil cooker on fire growth were studied. The use of water mist for extinguishing large oil pool fires and their extinguishing performance under different discharge pressure and with different types of water mist systems were investigated. Experimental results showed that the cooking oil underwent a substantial expansion in volume during heating. The fires developed quickly once the oil auto-ignited. The fire growth rate was affected by the oil depth in the pan and the hood position in the oil cooker. The water mist fire suppression systems effectively extinguished large cooking oil fires and prevented them from re-igniting. Their extinguishing performance was determined by the type of water mist system, discharge pressure and hood position in the oil cooker.     

不同喷射方式细水雾灭火效果的试验

细水雾的喷射方式对其灭火效果存在一定的影响。利用时间继电器控制细水雾灭火系统的启停,开展了连续式和脉冲式两种喷射方式的细水雾对开门与关门两种通风条件下不同燃料油池火分别进行抑制的试验研究。结果表明:在试验条件下,对于开门状态下连续式细水雾难以扑灭的汽油池火,脉冲式细水雾能显著提高灭火效果;对于连续式细水雾容易扑灭的柴油池火及关门状态下的汽油池火,脉冲式细水雾不能提高灭火效果,且灭火时间和用水量均有所增加;对于细水雾难以扑灭的酒精池火,连续式细水雾和脉冲式细水雾均未有效扑灭火焰。     

Application of fire suppression materials on suppression of LNG pool fires

An LNG pool fire is considered one of the main hazards of LNG, together with LNG vapor dispersion. Suppression methods are designed to reduce the hazard exclusion zones, distance to reach radiant heat of 5 kW/m², when an LNG pool fire is considered. For LNG vapor dispersion, the hazard exclusion zone is the distance travelled by the LNG vapor to reach a concentration of 2.5% v/v (half of the LNG lower flammability limit).Warming the LNG vapor to reach positive buoyancy faster is one way to suppress LNG vapor dispersion and reduce evaporation rate (thus fire size and its associated radiant heat) and that is the main objective in LNG pool fire suppression. Based on previous research, the use of high expansion foam has been regarded as the primary method in suppressing LNG pool fires. However, in 1980, another method was introduced as an alternative pool fire suppression system, Foamglas^®. The research concluded that 90% of the radiant heat was successfully reduced. Currently-called Foamglas^® pool fire suppression (Foamglas^® PFS) is a passive mitigation system and is deployed after the leak occurs. Foamglas^® PFS is non-flammable, and has a density one-third of the density of LNG, thus floats when an LNG pool is formed.This paper describes the study and confirmation of Foamglas^®PFS effectiveness in suppressing LNG pool fires. In addition, while Foamglas^® PFS is not expected to suppress LNG vapor dispersion, further investigation was conducted to study the effect of Foamglas^®PFS on LNG vapor dispersion. An LNG field experiment was conducted at Brayton Fire Field. The experimental development, procedures, results and findings are detailed in this paper.     

庚烷池火多火源燃烧特性的实验研究

多火源燃烧是森林火灾和城市群发性火灾中重要而又特殊的火灾现象,相关研究很少。通过恒定控制液面高度的实验系统,对直径0.1m、0.2m和0.4m的庚烷池火在单个火源、两火源燃烧和三火源线性排列时的火焰高度、火焰体积和燃烧速率等特性进行了实验研究。研究发现,三火源燃烧时中间火源的火焰高度、火焰体积和燃烧速率明显高于两火源燃烧和单火源燃烧,三火源燃烧时边上火源与两火源的燃烧状况难以区分。这些燃烧特性随着火源间距的减小,呈现增大趋势。热量反馈增强和空气卷吸受限这两种火源相互作用机制相互耦合,且随着火源间距的减小而增强,在S/D（S为火源间距,D为油池直径）为2～4时,两种机制强烈竞争,在其他参数范围内热量反馈增强效应占主导作用。研究还发现火焰体积与热释放速率有较好的线性相关关系,单位火焰体积的热释放速率约为1614kW/m3。     

Improved models of failure time for atmospheric tanks under the coupling effect of multiple pool fires

Fire accidents of chemical installations may cause domino effects in atmospheric tank farms, where a large amount of hazardous substances are stored or processed. Pool fire is a major form of fire accidents, and the thermal radiation from pool fire is the primary hazard of domino accidents. The coupling of multiple pool fires is a realistic and important accident phenomenon that enhances the propagation of domino accidents. However, previous research has mostly focused on the escalation of domino accidents induced by a single pool fire. To overcome the drawback, in this study, the failure of a storage tank under the coupling effect of multiple pool fires was studied in view of spatial and temporal synergistic process. The historical accident statistics indicated that the accident scenario of two-pool fires accounted for 30.6% in pool fires. The domino accident scenario involving three tanks is analyzed, and the typical layout of tanks is isosceles right triangle based on Chinese standard “GB50341-2014”. The thermal response and damage of a target tank heated by pool fires were numerically investigated. The volume of 500 m³, 3000 m³, 5000 m³ and 10000 m³ were selected. Flame temperature was obtained by FDS, and then was input onto the finite element model. The temperature field and stress field of target tanks were simulated by ABAQUS. The results showed that the temperature rise rate of the target tanks under multiple pool fires was higher than that under a single pool fire. The failure time of the tank under the coupling effect of multiple fires was lower than that under the superposition of multiple fires without the first stage. The stress and yield strength were compared to judge the failure of the target tank. The model of failure time for the tank under the coupling effect of pool fires was established. Through the verification, the deviation of this model is 4.02%, which is better than the deviation of 15.76% with Cozzani's model.