浸煤油固体着火及燃烧特性实验研究

以棉布、纸板和碎纸屑为对象,考察了煤油添加量对3种材料的点燃时间、火焰传播速率及烧损速率的影响,分析了固体材料性质对浸油固体着火及燃烧特性的影响机理。结果表明:随煤油含量增加,棉布和纸板的引燃时间缩短,表面火焰传播速率加快,并在特定比例出现闪火燃烧现象;而碎纸屑的火焰传播速率则随煤油含量的增加呈先增大后减小的趋势。横向比较时,火焰传播速率为:浸煤油的碎纸屑>纸板>棉布。值得注意的是,浸煤油棉布和纸板燃烧时能够观察到样品表面火焰传播速率(煤油燃烧速率)和样品本身炭化速率。     

干湿混纺地毯燃烧性能研究

为研究火灾初期自动喷水灭火系统作用时对铺地材料燃烧性能的影响,利用火焰传播量热仪,以混纺地毯为例,分别研究了干态、含水率50%、全浸泡3 种状态下水对其燃烧性能的影响。试验结果表明：随着含水率的升高,混纺地毯的引燃时间增长,含水率高的混纺地毯不易被引燃;含水条件下峰值热释放速率比干态条件下大,火灾规模较大,火焰燃烧持续时间内总热值较小;含水条件下,总烟气生成量及组成成分峰值出现时间后移。     

含油锯末着火及燃烧特性实验研究

测试了含油量、油品性质、锯末粒径和湿度等因素对含油锯末着火和燃烧特性的影响.结果表明,锯末含油量越高,油品挥发性越强,所需的引燃时间越短,质量损失率越大,火焰持续时间越长,高度越高,炭化深度越深,传播距离越长;若含油量超过13%,点火71 s之后火焰可传播至整个锯末表面,使锯末本身也发生燃烧;含汽油、煤油或含机油锯末被点燃的最低油含量分别3%、5%和12%;粒径较大锯末中的油品更容易蒸发燃烧;湿度越大,含油锯末越不容易被点燃.     

浸机油棉布引燃及燃烧特性实验研究

设置明火、香烟火和热辐射3种火源,研究机油含量对棉布引燃特性的影响。对于明火条件,还考查了机油含量和含水量对棉布燃烧特性的影响。热辐射引燃实验采用锥形量热仪进行,分别取热辐射强度为25、30、35、40kW/m2。结果表明:随着机油含量增加,明火和热辐射作用下棉布的引燃时间均逐渐缩短,香烟火条件下则影响较小;当机油含量达45%时,棉布被明火引燃的时间缩短近一半;明火作用下棉布的燃烧火焰持续时间先增大后减小,残留物质量先缓慢减小再迅速减小最后趋于恒定;对于29%机油含量的棉布,含水量越大引燃越困难,含水量达13%时棉布不能被引燃。     

基于图像识别技术的汽油、无水乙醇燃烧火焰识别研究

为了实现基于视频图像对火灾现场存在助燃剂的分类识别,对燃烧火焰的特征进行分析,根据汽油和无水乙醇引燃后各自特有的燃烧现象,结合火焰的视频图像识别算法实现对汽油和无水乙醇燃烧火焰的识别。首先,基于图像的灰度阈值得到其疑似火焰区域,再提取其H、S、I颜色分量和面积变化特征;并提取燃烧图像的小波高频能量特征和LBP直方图特征;最后将特征向量输入SVM分类器进行分类识别。试验表明,SVM对汽油和无水乙醇燃烧火焰的识别分类准确率可达98.5%,可较好地实现对汽油、无水乙醇燃烧火焰的区分。     

不同压力环境下小纸箱燃烧特性实验研究

在低压低氧舱中对小纸箱进行点火燃烧实验,探讨不同压力环境、不同通风条件对固体火灾燃烧热释放速率、火焰高度、火焰温度等燃烧性能的影响。燃烧工况的压力为90、75、64kPa,通风条件为不打孔、单面打孔和双面打孔。分析实验过程中热电偶的最高温度、最高温度对应的热电偶的位置以及压力变化曲线。结果表明:通风条件对固体可燃物在同一压力下的燃烧抑制作用显著。通风条件良好时,在75kPa的环境压力下,固体可燃物的燃烧可进入充分燃烧阶段。相同压力环境下,通风条件的改善缩短了固体可燃物燃烧发展阶段的时间,提高了固体可燃物燃烧的火焰温度。在相同通风条件下,环境压力降低,固体可燃物最大燃烧速率降低,固体可燃物上方相同位置的火焰温度下降,最大燃烧速率、火焰温度与环境压力成正比;压力近似时,火源温度的高低与固体可燃物热解的速度成正比,火源温度最低的固体可燃物燃烧质量变化曲线最为平缓。     

燃料间距对PMMA竖向火蔓延行为的影响

以PMMA（聚甲基丙烯酸甲酯）板（8 cm×10 cm×1 cm）为实验材料,开展不同燃料间距（0~10 cm）的竖向火蔓延实验,分析火焰高度、燃烧速率、热解前锋位置及点燃滞后时间的变化规律。结果发现,随着燃料间距增加,固体表面的净火焰高度与燃烧速率均呈现先增大后减小的趋势。此外,火焰在相邻固体燃料表面的蔓延过程中出现“点燃滞后”现象,点燃滞后时间随着燃料间距的增加呈指数级增长。     

全尺寸汽车燃烧试验火蔓延及火场温度研究

为探究汽车燃烧特性以及对相邻车辆的影响,通过点燃浸有汽油的海绵引燃发动机,对两辆平行反向放置的三厢式小汽车进行全尺寸燃烧实验。火灾实验室长40 m、宽12.87 m、高11.87 m,两车间距设为0.8 m。通过摄像机、热电偶等设备获取汽车火灾的发展过程,得到汽车内温度及烟气温度随时间的变化。结果显示:点燃发动机舱20 min后火蔓延至第二辆车,汽车燃烧29 min后火势达到最大;火焰在汽车内部蔓延的速度低于在车顶的蔓延速度;汽车内测得的最高温度为900℃,实验室空间各个测点测得的烟气最高温度为89~185℃。     

自由燃烧下油池火灾的燃烧特性研究

通过对93#汽油、0#柴油和95％的乙醇的自由燃烧试验,得出了3种燃料的燃烧特性,包括液层温度、质量损失速率、燃烧速度、密度、热释放速率、火焰温度等,并结合理论公式拟合热释放速率随油盘直径变化的曲线.质量损失速率与火焰高度汽油＞柴油＞乙醇;汽油、柴油、乙醇燃烧时的液面温度分别为125、310、80℃;3种燃料都在2 min以后达到稳定燃烧状态.     

窗帘辐射引燃特性实验研究

对市售的亚麻、棉麻、涤纶、仿真丝和雪尼尔5种窗帘进行辐射引燃实验,测得辐射引燃过程中的引燃现象、表面温度变化情况、引燃时间、质量损失速率和烟气中CO体积分数变化情况。结果表明:5种窗帘在引燃过程中都有收缩、熔融的现象发生,亚麻窗帘较易引燃;引燃温度为321~522℃,引燃时间为244~449s;平均质量损失速率为0.006 6~0.04g/s,雪尼尔窗帘燃烧速率较大;燃烧过程中单位质量麻质窗帘烟气中CO含量平稳期较长,单位质量仿真丝窗帘烟气中CO含量峰值最大。     

燃料覆盖率对非连续分布固体竖向火蔓延的影响

非连续分布固体燃料是指多个固体可燃物非常靠近但被气隙隔开的状态,与连续分布燃料相比,非连续分布燃料更能够代表一些现实的火灾情况,以往的研究中较少涉及.笔者通过实验的方法分析不同燃料覆盖率下固体燃料竖直向上火焰蔓延的特点.所选用的浇筑型聚甲基丙烯酸甲酯(简称"PMMA")材料广泛应用于高层建筑外立面中,呈现出一种非连续分...     

Burning behavior of sedan passenger cars

Four full-scale fire experiments using 4-door sedan passenger cars were carried out. The cars were ignited either at the splashguard of the right rear wheel or at the left front seat in the passenger compartment with a gasoline spill. The temperature inside the burning car and the mass loss rate were measured. The burning of the 4-door sedan was composed of three compartmental fires: the engine compartment, the passenger compartment, and the rear part inclusive of the fuel. In the experiments where ignition was initiated at the splashguard, the flame spread in the following order: to the rear part of the car, to the passenger compartment, and to the engine compartment. Breakage of the window glass markedly affected the spread of fire into the passenger compartment. The quantity of gasoline in the fuel tank also affected the speed of spread of the fire, because the gasoline ignited at an early stage of the fire. In the experiment where ignition was initiated in the passenger compartment, the fire gained force after the windshield was broken entirely. The flame spread in the following order: to the passenger compartment, to the engine compartment, and to the rear part of the car. The temperature within the passenger compartment peaked at 1000 °C. The heat release rate (HRR) curves showed several peaks depending on the burning of the three compartments. The HRR increased markedly when the fire spread to several different parts of the car at the same time. The HHR peaked at 3 MW when the passenger compartment and fuel (gasoline) burned simultaneously. The measured HRR curves were characterized by superposition of a Boltzmann curve and a Gaussian curve in order to obtain a model, which allowed us to make a more precise prediction of the fire spread probability from a burning car to nearby structures. The HRRs of burning cars were described by the sum of HRR from each compartment.     

热老化对阻燃PVC电缆燃烧性能的影响

采用锥形量热计对不同热老化程度的阻燃PVC电缆的引燃特性和热释放规律进行试验研究。结果表明,电缆试样的引燃时间随热老化程度的增加而延长,老化前期引燃时间增大较快,后期减缓;热释放速率的初始峰值随热老化程度的增加呈下降趋势;火灾性能指数随老化时间的延长总体呈下降的趋势。故与新投入使用的电缆相比,老化电缆的引燃危险和热危险相对减小。     

Warehouse commodity classification from fundamental principles. Part II: Flame heights and flame spread

In warehouse storage applications, it is important to classify the burning behavior of commodities and rank them according to their material flammability for early fire detection and suppression operations. In this study, a preliminary approach towards commodity classification is presented that models the early stage of large-scale warehouse fires by decoupling the problem into separate processes of heat and mass transfer. Two existing nondimensional parameters are used to represent the physical phenomena at the large-scale: a mass transfer number that directly incorporates the material properties of a fuel, and the soot yield of the fuel that controls the radiation observed in the large-scale. To facilitate modeling, a mass transfer number (or B-number) was experimentally obtained using mass-loss (burning rate) measurements from bench-scale tests, following from a procedure that was developed in Part I of this paper.Two fuels are considered: corrugated cardboard and polystyrene. Corrugated cardboard provides a source of flaming combustion in a warehouse and is usually the first item to ignite and sustain flame spread. Polystyrene is typically used as the most hazardous product in large-scale fire testing. The nondimensional mass transfer number was then used to model in-rack flame heights on 6.1-9.1 m (20-30 ft) stacks of ‘C’ flute corrugated cardboard boxes on rack-storage during the initial period of flame spread (involving flame spread over the corrugated cardboard face only). Good agreement was observed between the model and large-scale experiments during the initial stages of fire growth, and a comparison to previous correlations for in-rack flame heights is included.     

低温氢泄漏及射流火传播特性研究现状

阐述了低温氢的应用前景及泄漏危险性,从气体扩散特性和射流火点火、传播行为两方面介绍了低温氢泄漏的研究现状,对低温氢泄漏气体扩散及射流火传播特性的研究方法、手段及结论进行了总结分析。目前,低温氢泄漏研究方法包括实验研究和数值模拟,多数研究集中在气体扩散特性,对射流火的点火、传播行为的产生条件及影响因素尚不明确。未来应完善低温氢泄漏气体扩散预测模型,以建立有效的低温氢泄漏气体扩散过程及射流火点火、传播预测模型。     

Ignitor and Thickness Effects on Upward Flame Spread

The effects of a material's ignitor characteristics and burning duration on upward wall flame spread are investigated. The ignitor is represented as an energy line source. Its energy release rate and its duration after ignition are considered. The material is represented as a finite, thick noncharring material with properties representative of polymethylmethracrylate (PMMA). A Volterra integral equation is solved for upward flame speed by numerical methods, and a transient, noncharring burning rate model is included. Results show the influence on propagation of ignitor effects and material thickness. A propagation map is computed showing the domains of flames that spread and flames that stop. Criteria for propagation and how propagation affects fire growth are considered in a standard room-corner test.     

汽油池火热辐射量化模型预测准确性分析

分析池火热辐射半经验模型的预测精度随汽油池火油池直径的变化。运用MATLAB 分析了各组合模型热辐射通量预测值与实验值之间的误差,筛选出用于预测汽油池火的热辐射通量的最优组合模型。结果表明,采用本文拟合的汽油热辐射系数ηrad能提高固体火焰模型热辐射通量的预测准确性,采用经典固体火焰模型及本文提出的热辐射系数公式的组合模型为最优组合模型。当池火直径为0.3～22.3 m 时,最优组合模型的预测值与实验值的归一化均方误差低于0.05,该组合模型的预测准确度高于Mudan 模型与Shokri-Beyler 模型等其他半经验模型。     

低压环境下固体材料燃烧特性研究进展

低压环境一般存在于高高原地区和巡航飞机,我国存在着大面积的高高原地区和拥有世界上数量最多的高高原机场,低压环境会使固体材料的燃烧特性发生变化.介绍了固体可燃物的点燃、燃烧和火焰传播过程,系统综述了织物、纸箱、木材、电缆4种常见固体材料在低压环境下的燃烧特性研究进展,并对其燃烧特点进行了分析和总结,指出未来固体材料低压环...     

粒径对中密度纤维板粉尘爆炸特性影响实验研究

为探究粒径对中密度纤维板粉尘爆炸及相关特性的影响,采用20 L爆炸球、粉尘云最低着火温度装置、锥形量热仪和哈特曼管装置,对不同粒径粉尘的爆炸下限、最大爆炸压力、最低着火温度、热释放速率和火焰传播规律进行研究。结果表明,随着粉尘粒径减小,爆炸下限和粉尘云最低着火温度降低,最大爆炸压力逐渐增大;粉尘燃烧过程分为升温、着火、过渡、加剧和熄灭5个阶段,并出现2个峰值,热释放速率变化时间和吸热时间随着粒径减小而增加,热释放速率峰值增大;火焰在管道内的传播随着粒径减小先增强后减弱,管道外“火球”形状更大,火焰消散后火星数量变少,火焰尾端更加细长。