细水雾作用下火灾烟气典型特性参数的变化规律

利用ISO 9705全尺寸多功能热释放速率测试仪研究细水雾作用下火灾烟气的消光系数、质量密度及辐射热通量等特性参数的变化规律,通过改变细水雾工作压力、喷头种类和喷头数量等参数研究雾滴粒径、喷雾强度等对烟气特性参数的影响规律.确定了受限空间通风助燃和熄灭火焰的临界速率.实验发现,火源热释放速率是影响烟气特性参数变化规律的主要内在因素.研究结果为细水雾技术用于火灾烟气抑制提供了科学的参考依据.     

细水雾作用下池火热释放率研究

热释放速率是燃烧过程的基本特性参数之一，利用锥型量热计研究细水雾与池火相互作用特性时，部分细水雾会受热汽化并改变进入锥型量热计的气体浓度，导致热释放速率测量产生一定误差。文章提出了一种简单合理的方法来修正相应的热释放速率数据，并在此基础上利用锥型量热计研究了细水雾作用下的池火热释放速率特性。     

细水雾对油池火热释放速率影响的初步研究

热释放速率是反映火场规模与发展的最重要的基础参数，利用ISO9705实验台进行细水雾灭火有效性的影响因素及相关机理研究，不仅能营造出一个真实的室内火灾环境，而且能够得到火场的热释放速率。对汽油池火的初步实验表明：热释放速率曲线能直接反映出细水雾对火源的作用；细水雾作用下燃烧总的热释放量减少很大；开启水雾的时间不同，细水雾对热释放速率峰值的削减程度不同。     

细水雾灭火对烟雾特性影响分析

通过数据分析细水雾作用下,烟雾中的O2、CO、CO2浓度、烟雾的消光系数及烟雾粒径等特性参数的变化规律,分析不同压力对烟气特性参数的影响规律。通过观察图片分析细水雾后烟雾颗粒的变化情况,以及烟雾沉降原理分析。从而得出细水雾是一种很适用的灭火方式,它可以有效控制火灾烟气的产生和蔓延。     

不同排烟条件下细水雾扑灭油池火的实验研究

通过全尺寸模拟实验研究了细水雾和机械排烟共同作用下小室火灾烟气特性.实验中通过改变变频器频率来调节风量和风速,通过封堵来改变排烟口位置及其开口大小,研究分析了细水雾和机械排烟共同作用下火场的温度和CO体积分数变化.实验结果表明,随着排烟强度的增加,细水雾灭火时间延长,烟气平均升温速率和平均降温速率均下降,CO体积分数降...     

室内沙发燃烧的全尺寸实验和数值模拟

在ISO9705标准的全尺寸燃烧间(3.6m×2.4m×2.4m)内对单人沙发进行全尺寸火灾实验模拟,测量了沙发燃烧的热释放速率、室内烟气温度分布等火灾参数,分析比较了它们之间的关系,同时也用数值模拟的方法对聚氨酯(PUF)材料燃烧占支配地位的沙发燃烧过程进行了模拟,计算得到了沙发燃烧的热释放速率、室内温度场分布和烟气中性面高度.结果表明,计算得到的热释放速率、温度分布和烟气中性面高度与实验测得的结果比较吻合.     

低压低氧环境下油盆火的燃烧特性和烟气特性

为了研究高原地区低压低氧环境下的燃烧特性和烟气特性,在拉萨和合肥两地区分别进行了正庚烷油盆火实验.实验测量了油盆上方温度、热辐射通量、燃料失重速率、烟气热辐射发射率、烟气组分浓度和火焰高度等燃烧和烟气参数.结果表明:随着海拔高度的升高,油盆火单位面积燃烧速率降低,火焰及热烟气温度降低,对周围环境的热辐射通量和单位面积辐...     

低压(低氧)条件下古建筑装饰性织物燃烧特性的实验研究

在西藏和内地分别对古建筑中常用的装饰性织物进行了燃烧对比实验,测量了四种织物燃烧过程的失重速率、烟气成分以及火焰温度等参数。研究表明:织物在低压(低氧)条件下,火焰对织物的热辐射和热对流作用减弱,相同尺寸织物的燃烧速率、燃烧效率、火焰温度、烟气体积分数峰值降低,残炭量增大,明火燃烧时间增长。织物燃烧的热释放速率也随着大气压力降低而减小。研究结果揭示了高原环境对织物燃烧特性的影响规律,为高原火灾的预防和早期探测提供了科学依据。     

高压细水雾系统抑制货架障碍火的实验研究

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。     

火灾环境下钢管构件热响应特性

利用ISO9705标准火灾实验系统模拟火灾环境,对钢管构件的温升及温度分布进行实验研究.测量火源的热释放速率、温度场及钢构件的温度等参数,分析不同火源功率与位置下热环境的特点及钢构件的温度响应规律.结果表明,钢的导热系数较大,但由于所用建筑结构钢材大部分都是薄壁构件,截面积很小,使得构件沿长度方向的内部传热远小于沿径向与外界的热交换,因此,沿长度方向构件温度分布具有较大的不均匀性,主要取决于其表面热烟气温度的变化.     

细水雾与液体燃料火焰相互作用的小尺度实验研究及简化模型

细水雾灭火技术是可以替代哈龙灭火剂的绿色灭火技术。以此为工程背景,开展了细水雾与液体燃料火焰相互作用的小尺度实验研究,结果表明:预燃时间、喷雾气压、细水雾气源种类等参数对灭火过程有重要影响。细水雾抑制熄灭液体燃料火焰的主要机理是燃料表面冷却效应。建立的液体燃料平均温度零维简化模型与实验结果吻合较好。     

A Zone Model in Simulating Water Mist Suppression on Obstructed Fire

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.     

A numerical simulation of the suppression of hydrogen jet fires on hydrogen fuel cell ships using a fine water mist

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.     

喷水排烟作用下孤岛火灾行为及烟气运动实验

针对大空间内孤岛火灾安全集中讨论的焦点问题,通过全尺寸实验的方法研究了喷水排烟作用下大空间内孤岛火灾行为及烟气运动过程.分别设置不同火源功率、有无排烟喷水、不同排烟量、不同喷头类型及工作压力等条件而开展了全尺寸的对比性实验,并理论分析了排烟和喷水存在情况下的室内火灾动力学平衡的变化.结果表明:无排烟喷水时孤岛火灾增长迅速,在1.3 MW时可达到轰燃温度;不同喷头类型时孤岛内火灾行为特征及灭火规律表现不同;高速水雾喷头喷射会扩展羽流区半径及加强烟气分界面热分层失稳;喷头类型是灭火关键因素,增加喷头工作压力和排烟量可以降低室内温度,但效果不明显;规范设计孤岛排烟量(20 ACH)和喷水条件(标准喷头、0.05 MPa)存在一定的不足.全尺寸实验验证了排烟喷水作用可以有效地控制孤岛火灾对大空间影响.     

Experiment and prediction of fire extinguishment with water mist in an enclosed room

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.     

受限空间内细水雾抑制熄灭火焰过程中一氧化碳的生成率

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     

Experimental investigation on influence of different transverse fire locations on maximum smoke temperature under the tunnel ceiling

In former studies, fires were always assumed to occur at the longitudinal centerline of tunnels. In fact, fires will occur at any locations in tunnels, with different distances to the sidewall. A set of model scale experiments were carried out, to investigate the influence of different transverse fire locations on maximum smoke temperature under the tunnel ceiling. Results show that the restriction effect of the sidewalls of tunnels cause the maximum smoke temperature rise under the ceiling to increase compared with the unconfined space, even fires occurs at the longitudinal centerline. The maximum smoke temperature rises above the fire keep almost unchanged with the fire moving closer to the sidewall at the beginning and then increase significantly after the distance between the fire and the sidewall decreases to a certain value. For small pools of wall fire, the “mirror” effect is reasonable, and for large pools, will bring a relatively large error without considering the influence of the equivalent diameter of a wall fire, resulting in underestimating the mass flow rate of fire plume and then overestimating the smoke temperature. Under all fires, the maximum smoke temperature rise under the ceiling decreases exponentially as the longitudinal distance from fire increases. Correlations for related parameters are proposed.     

船舱中油的存在状态及危害分析和预防措施

介绍了船舱中油的主要存在状态包括:液态油、油烟、油雾、喷雾等。当油雾或喷雾的浓度增大到一定程度时,有引起火灾和爆炸的危险。主要预防措施可以安装油雾探测装置(OMD),OMD可通过检测油雾的浓度并发出报警信号来预防爆炸的发生。