Experimental study on the quenching process of methane/air deflagration flame with porous media

This article reports experimental investigation of deflagration flame quenching behavior by porous media. In this study, a semi-vented deflagration chamber with a porous media plate was constructed, taking account of effects of obstacles and porous media materials on the flame quenching process. A high speed video camera was used to image the process and behavior of flame propagation, meanwhile, the gas-phase temperatures and ion currents, upstream, within, and downstream of the porous media, were measured using micro-thermocouples and ion probes, respectively. Results show that methane/air deflagration flame can be quenched by the Al₂O₃ porous media with thickness of 20 mm and pore density of 10 ppi. However, the presence of obstacles along the flame path may lead to significant increase of flame speed, thereby both the decreases of gas-phase temperature and ion current when the flame passes through the porous medium in the case with continuous obstacles are less, eventually the unburnt gases downstream the porous media may be reignited. Compared to Al₂O₃, Al porous media shows superior flame quenching performance because this metallic material has higher thermal conductivity, which makes combusting flame release more heat to the pore walls and adjoining structures of the porous media.     

障碍物压力反射特性对瓦斯爆炸传播影响的数值模拟研究*

为了研究不同形状障碍物对瓦斯爆炸传播的影响机理,对直径0.2 m、长6.5 m的密闭直管道内的瓦斯爆炸过程进行数值模拟。研究结果表明:在该实验条件下,对于火焰通过整个管道的时间,方形障碍物时间最长,球形障碍物与无障碍物时间接近,且用时最短;无障碍物时,在反射压力波作用下火焰传播速度存在明显的波动特性;有障碍物时,障碍物的诱导作用要大于反射压力波的作用,火焰传播的这种波动特性得到抑制,提升了火焰前锋向未燃区域传播的能力;压力波的波动频率与气流震荡、压力波反射叠加有关,波幅则主要与正向压力波和反射压力波的叠加效果有关。研究结果为煤矿瓦斯爆炸事故防治及隔抑爆技术应用提供技术支撑。     

阻化注浆在硫化矿床自然发火治理中的应用

为治理大厂铜坑矿细脉带硫化矿石自燃火灾,提出喷洒添加NCZ-1型防火阻燃剂的阻化泥浆灭火方法;依据该矿具体条件设计了喷洒工艺流程,测定单位体积阻燃剂用量及各指标气体浓度等参数,研究注浆法在自燃火灾治理中的应用问题。结果表明:该防火阻燃剂在金属矿山火灾治理中效果较好;喷洒阻化泥浆后,环境质量明显改善,主要有害气体SO2浓度减少47.16%;CO2浓度减少了58.49%;阻化期可达14～20天。该试验成果及使用方法对非煤类含硫矿床自燃治理研究有一定借鉴意义。     

煤尘爆炸性鉴定中瞬间火焰长度检测技术的研究

确定煤尘爆炸性质需要检测其燃烧瞬间的火焰长度,现有的大管状煤尘爆炸性鉴定系统以肉眼观察作为主要检测手段,存在测量精度差、重复性误差大以及人为干扰因素多等问题,提出将数字图像处理技术引入到煤尘爆炸性鉴定系统的方法即通过采用数字图像处理技术,对煤尘火焰图像进行预处理及图像分割与边缘检测后,得到最大火焰长度特征参数,并推导出煤尘爆炸的判断依据。     

基于不同风速下火旋风的数值计算及特性分析

基于大涡模拟(LES)技术,对不同风速下的火旋风进行数值模拟。运用最小二乘拟合方法研究不同风速下火旋风的中心漂移角速度的变化,其结果表明:随着风速的增加,中心漂移角速度的变化规律遵循某3次方多项式变化趋势,发现存在某一临界风速(3.18m/s)对火旋风中心漂移角速度的变化速率有较大影响。同时,对热量释放率及火焰温度场进行分析,认为随风速的增加,热量释放率逐渐增加且波动逐渐减小,火焰温度场分布梯度逐渐增加,高温区分布呈现连续纺锤面分布形式。     

基于彩色图像的林火图像火焰分割研究

结合实际林火图像的特点,提出了一种基于彩色图像分割策略的林火图像的火焰分割算法。该算法首先将图像转化为HSI彩色模型,然后根据各个分量的特点进行分割,并且进行了仿真实验,实验结果表明此算法能够很好地将火焰从复杂的背景中分割出来,克服了基于灰度图像分割不能准确分割烟雾和火焰的弊端,为今后对林火图像进一步分析提供了良好的基础。     

An analytic study of the effect of saltation on wind profiles

An analytic study of wind profiles above the saltation layer, in which the motion of uniform saltating grains of sand or snow occurs, is conducted. In this study, analytic solutions of the Ekman layer equation that governs the motion of air in a barotropic, neutral atmosphere are obtained in order to investigate the effects of the saltation on the airflow at large distance from a smooth surface. Solutions are derived subject to expressions of the eddy viscosity K(z) defined above the saltation layer up to the Ekman layer. The wind profiles and boundary layer interactions with the saltation process are discussed. With the assumptions that the eddy viscosity varies smoothly from the surface layer to the Ekman layer and K=0.4u _* z(1–z/h), the solutions are found to be consistent with bottom boundary conditions, specified by the velocity profile law outside the saltation layer. These solutions can be either used as an alternative to predict the saltation or used to test the sensitivities of the parameterization scheme designed to simulate dust emissions in a climate or general circulation model (GCM).     

凝胶渗透色谱-硅胶柱-气相色谱-负化学离子源质谱测定生物介质中49种BFRs类化合物

建立了生物介质内22种多溴联苯(PBBs)和27种多溴联苯醚(PBDEs)的净化和分析方法。通过分析不同时间段凝胶渗透色谱(GPC)洗脱液中49种化合物含量,得出不同化合物凝胶色谱洗脱曲线。样品经过凝胶渗透色谱-混合硅胶柱净化后,再使用GC-(NCI)/MS对样品进行检测。实验结果表明,PBBs和PBDEs检出限分别为0.02~0.88 pg/g和0.01~74.00 pg/g。对实验过程进行验证发现,样品不同浓度加标回收率为80%~120%,相对标准偏差小于20%。该方法具有良好的净化效果、准确度和精密度,拥有良好的线性范围及检出限,满足生物介质中溴代阻燃剂的检测分析实际要求。     

国内外烟气流速测量标准比较分析

比较了国内外燃煤电厂烟气流速测量技术及相关标准,分析了测量仪器、矩形烟道采样位置及采样点位置和数目等方面的异同,结合我国电厂现场烟气流速测量的实际情况,提出了修改《固定污染源排气中颗粒物测定与气态污染物采样方法》相关内容的建议。     

气体污染源中总氟的监测方法研究

通过对玻璃纤维滤筒的预处理,在等速采样情况下达到完全捕捉烟气中的总氟。