共查询到17条相似文献,搜索用时 116 毫秒
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受限空间中细水雾灭火的准稳态模型 总被引:4,自引:0,他引:4
通过受限空间中大量细水雾灭火实验,总结出预测细水雾系统灭火效果的准稳态模型。该模型是针对细水雾扑灭有障碍火的情况而发展的,火焰的熄灭主要是由于燃料燃烧耗氧和细水雾汽化稀释造成氧气浓度的降低而导致的,忽略了细水雾与火焰的直接作用,模型基于能量守衡,要求输入以下参数:火源功率、受限空间的几何结构、通风口面积和细水雾施加流量,通过模型预测出稳态时受限空间的温度和氧气浓度,进而可以确定临界火源的尺度(功率大小),同时能准确预测较大功率范围火的熄灭时间。 相似文献
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细水雾抑制气体扩散火焰的机理研究 总被引:4,自引:0,他引:4
应用三维LDV/APV系统和热成像方法,测量了细水雾和气体扩散火焰作用过程中的细水雾雾场、火焰温度场并研究了细水雾和气体扩散火焰的作用过程.探索了细水雾抑制火焰的机理和规律,比较了细水雾抑制气体扩散火焰时3种主要灭火机理,用数据定量表征了细水雾灭火时,水雾的蒸发潜热吸热作用、热容吸热作用以及稀释氧气作用对抑制气体扩散火焰所做的贡献,细水雾直接喷射或被卷吸进入火焰内部时,由于表面积大,吸收热量快,迅速汽化,体积扩大。大量的汽化潜热会降低火焰区及气相燃料的温度,细水雾及其蒸汽吸收部分热辐射,降低对燃料的热回馈,减少其汽化蒸发,从而降低反应区的可燃气体积分量。这些因素都会大大降低化学反应速度,抑制火灾的发展,直至扑灭火灾。 相似文献
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细水雾抑制熄灭火焰过程中一氧化碳的浓度是评价细水雾灭火系统安全可靠性的一个重要参数.本文通过受限空间内细水雾抑制熄灭障碍火的模拟实验研究,发现细水雾抑制熄灭火焰过程中一氧化碳生成率存在两种控制模式,即燃料控制模式和细水雾流量控制模式.实验结果表明,在燃料控制模式下,一氧化碳生成率随着燃料流量的增大而增大;在细水雾控制模式下,一氧化碳生成率随着细水雾流量的增大而增大.为了获得两种控制模式的临界转变条件,对燃料控制模式和细水雾控制模式的临界工况进行水蒸气含量分析.通过理论分析,得到一氧化碳生成率控制模式转变的水蒸气含量临界范围与 Suh and Atryeya 理论基本一致,即空气中水蒸气质量分数达到25%~65.5%时,水蒸气对火焰的作用从化学作用转为物理作用,一氧化碳生成率控制模式开始转变 相似文献
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In this paper, in order to evaluate the reliability of a fine water mist for the suppression of fires on hydrogen fuel cell ships, the fire dynamics simulator (FDS) software was used to simulate the jet fire process and the action of a fine water mist on a fire caused by a hydrogen leakage in the hydrogen storage tank areas of hydrogen fuel cell ships. The fire scenario was classified into vertical or horizontal jet fires according to the location of the leakage in the hydrogen storage tank area, and the suppression effects of a fine water mist on hydrogen jet fires under a different droplet size, spray velocity, and ambient wind speed were compared and analyzed. The results indicate that a fine water mist is not effective in extinguishing hydrogen jet fires; however, by selecting suitable parameters (a spray velocity of 30 m/s and average droplet size of 30 μm), it can effectively reduce the fire field temperature of hydrogen jet fires and prevent the fire from developing further. Increasing the average droplet size of the fine water mist results in a gradual degradation of the suppression effect, while a higher spray velocity of the mist enhances the suppression effect to a certain extent. The ambient wind speed is an important factor that influences the suppression effect of a fine water mist on hydrogen jet fires, and when this speed is less than 4 m/s, a fine water mist with a higher spray velocity and smaller average droplet size is still a superior way of suppressing fires. 相似文献
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The correlation between oxygen concentration and fire temperature when fire was extinguished with water mist was theoretically studied. The Semenov theory was applied to analyze the critical condition when fire was extinguished with water mist, from which the correlation could be obtained. The water mist experiments were carried out by varying the fire size, atomizer number, ceiling height, system pressure, and pre-burn time in an enclosed room. The oxygen concentration near the edge of the liquid pool and the fire temperature above the center of the liquid pool were measured. A comparison of the experimental data with the correlation was made under different conditions. The results showed that fire extinguishment was a stochastic process which could be affected by many factors. This theoretical model could predict the correlation between fire temperature and oxygen concentration when fire was extinguished with water mist in an enclosed room and it can also be treated as a critical condition for fire extinguishment. 相似文献
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货架火是商场超市火灾中的主要燃烧形式,对其行为规律的研究有助于该类建筑防灭火工作的开展。分析了利用高压细水雾系统灭货架火的可行性;搭建了高压细水雾灭火的实验平台,通过实验研究了高压细水雾系统控制与扑灭商场超市货架火灾的可能性;测试了细水雾的施加对该类火灾现场温度、辐射热通量强度及烟气浓度变化的影响情况;比较了货架的不同摆放形式对火灾参数的影响。实验结果表明,利用高压细水雾系统灭货架火是有效可行的。 相似文献
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Fire extinct experiments with water mist by adding additives 总被引:1,自引:0,他引:1
The effects of fire extinguishment with water mist by adding different additives were studied.Tens of chemical substances (including alkali metal salt,dilution agent and surface active agent) were selected as additives due to their different extinct mechanisms.At first the performance of fire extinguishment with single additive was studied,then the effects of the same kinds of chemical substances under the same mass fraction were compared to study their influences on the fire extinguishment factors,including extinct time,fire temperature and oxygen concentration from which the fire extinct mechanism with additives could be concluded.Based on this the experiments were conducted to study the cooperate effect of the complexity of different additives.It indicated the relations between different firefighting mechanisms and different additives were competitive.From a large number of experiments the extinct mechanism with water mist by adding additives was concluded and an optimal compounding additive was selected. 相似文献
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In order to investigate the fire suppression effectiveness of water mist with metal chloride additives, ultrafine water mists of these salts with diameters about 10μm were introduced into CH4 /air non-premixed flame in the cup burner. Results showed that these droplets hard to make itself to the flame front under the cup burner flow conditions functioned as a carrier of the vaporized solid particles or its decomposed materials. The metal chloride improved fire suppression efficacy of water mist which were affected by the type and concentration of metal chloride. On a mass basis, there is a fire suppression effectiveness relationship of MgCl2 相似文献
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A zone model is proposed for studying the obstructed fire suppression by a total flooding water mist system in a chamber with different ventilation conditions. This is a one-zone thermal model mainly for simulating scenarios where oxygen consumption and dilution by water evaporation are the main fire extinguishing mechanisms. The water flow rate and volume mean diameter of a droplet has been used to characterize the water mist system. The fire is taken as a heat source, and its heat release rate is related to oxygen consumption. Mass and energy conservation equations for gaseous species in the enclosure under fire have been solved. Fire suppression is predicted by investigating the limit of oxygen concentration. Numerical results are verified by two sets of experiments on water mist fire suppression system reported in the literature. The predicted results agreed qualitatively with the experiments. In addition, the predicted results by this model are also compared with other existing models. Factors affecting the fire extinguishment mechanism are analyzed, and the limitations of the model are discussed. 相似文献