障碍物对瓦斯煤尘爆炸火焰传播规律的影响

为了进一步探究瓦斯煤尘耦合爆炸火焰的传播规律,用自行搭建的半封闭垂直管道爆炸试验系统,研究障碍物对瓦斯煤尘耦合爆炸火焰传播规律的影响。研究结果表明:障碍物能显著提高瓦斯煤尘爆炸火焰的传播速度,其加速机理主要是障碍物诱导的湍流区会促进火焰的传播;火焰在传播过程中的加速度不是一直增加,随着火焰速度的增加会出现上下波动;煤尘的加入会使瓦斯爆炸产生的火焰传播速度显著增大及速度的最大值距离点火端较远;通过障碍物时爆炸产生的火焰形状发生较大的改变,出现拉伸和褶皱现象。     

Experimental study of the effect of nitrogen addition on gas explosion

Flame propagation and combustion characteristics of methane/air mixed gas in gas explosion were studied in a constant volume combustion bomb. Stretched flame propagation velocity, unstretched laminar flame propagation velocity, unstretched laminar combustion velocity and Markstein length were obtained at various ratios of nitrogen to gas mixture. Combustion stability at various ratios of nitrogen to gas mixture was analyzed by analyzing the pictures of flame propagation. Furthermore, the effect of initial pressure on the flame propagation and combustion characteristics of methane/air mixed gas in gas explosion was analyzed. The results show that the unstretched laminar flame propagation velocity, the unstretched laminar combustion velocity, Markstein length, flame stability, and the maximum combustion pressure decrease distinctly with the increase of nitrogen fraction in the gas mixture. At the same ratios of nitrogen to gas mixture, Markstein length, unstretched laminar flame propagation velocity and unstretched laminar combustion velocity decrease and the maximum combustion pressure increase with the increase of initial pressure of the gas mixture. When nitrogen fraction in the gas mixture is over 20%, the flame will be unstable and is easy to exterminate.     

丙烷/空气拉伸火焰传播稳定性实验研究

为了揭示空气中丙烷火焰传播特性,利用纹影系统记录了预混气体小能量点火条件下火焰形成与传播过程,得到了火焰表面的微观结构特征,分析了混合气体火焰的稳定性及其影响因素。结果表明:丙烷/空气混合物火焰发展过程及其表面微观特征与浓度直接相关;当混合物浓度接近爆炸上下限时,火焰扩展速率整体不大于0.5 m/s,燃烧区域向上漂浮,浮力成为影响火焰失稳的主导因素;当混合物浓度靠理论配比时,火焰呈规则球形扩展,火焰稳定性按照先减弱后增强的趋势发展,火焰表面褶皱的形成及演化规律是热扩散不稳定性和流体力学不稳定性共存与竞争的作用结果。     

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。     

Scale effects on hydrogen–air fast deflagrations and detonations in small obstructed channels

An experimental study of flame propagation, acceleration and transition to detonation in hydrogen–air mixture in 2-m-long rectangular cross-section channel filled with obstacles located at the bottom wall was performed. The initial conditions of the hydrogen–air mixture were 0.1 MPa and 293 K and stoichiometric composition (29.6% H₂ in air). The channel width was 0.11 m and blockage ratio was 0.5 in all experiments. The effect of channel geometrical scale on flame propagation was studied by using four channel heights H of 0.01, 0.02, 0.04, and 0.08 m. In each case, the obstacle height was equal to H/2 and the obstacle spacing was 2H.

The propagation of flame and pressure waves was monitored by four pressure transducers and four ion probes. The pairs of transducers and probes were placed at various locations along the channel in order to get information about the progress of the phenomena along the channel.

As a result of the experiments, the deflagration and detonation regimes and velocities of flame propagation in the obstructed channel were established.     

大尺寸通风管网中障碍物对瓦斯爆炸冲击波传播特性影响的数值模拟

为了研究大尺寸通风管网中的瓦斯爆炸传播规律,采用数值模拟方法,针对具有不同障碍物数量的大尺寸通风管网模型,利用Fluent分析管网中各个监测点的超压变化曲线以及障碍物附近的速度矢量图,分析爆炸冲击波传播规律。研究结果表明:初期瓦斯爆炸后,障碍物的存在改变了通风管网内未燃瓦斯的积聚区域;高温和高压发生耦合作用,在氧气相对充足的进气管道中形成二次爆炸;障碍物与火焰波以及管网自身结构变化等多种因素形成复合作用,改变了通风管网内瓦斯爆炸冲击波的传播路径和叠加区域的位置;无障碍物时高压区域出现在进气管道中,有障碍物时高压区域出现在中部直管与斜管的交汇处附近,且数值相对较大。     

Effects of multiple annular obstacles on flame propagation of local corn starch dust in a vertical pipe

With high-speed camera technology, the propagation behavior of explosion flame for the local dust cloud of corn starch in a semi-open vertical pipe under the action of the annular obstacle was studied experimentally, and the blockage rate and the annular obstacle numbers as well as impact of dust cloud concentration on the flame propagation were investigated. The researches showed that both the blockage rate and the annular obstacle numbers have significant effects on the flame speed and propagation process for the dust cloud explosion of corn starch. The increase of the blockage rate of such annular obstacles will cause that the combustion of dust cloud with high concentration is mainly concentrated in the lower part of the pipe. The increase of the annular obstacle numbers will lead to the acceleration of combustion of the dust cloud. With the increase of the blockage rate and the annular obstacle numbers, the maximum flame speed shows a trend of the first increasing and then decreasing, and the phenomenon of accelerated propagation of the flame becomes more and more obvious, however, the distance of continuous acceleration for the flame is gradually decreased and the maximum flame speed is farther from the outlet of the pipe. Under the action of such annular obstacles, the concentration of dust cloud has a significant effect on the flame speed and shape of the dust cloud of the corn starch. The increase of the concentration of the dust cloud will decrease the acceleration effect of such annular obstacles to result in maximum flame speed showing a trend of the first increasing and then decreasing. However, the acceleration distance of the flame is longer, and the maximum flame speed is closer to the outlet of the pipe. The increasing concentration will make the flame speed develop more slowly, the flame color will be darker, and the flame segmentation phenomenon will be more obvious.     

Modeling of maize starch explosions in a 12 m3 silo

This paper presents a 2-dimensional numerical model of Eulerian–Lagrangian multi-phase combustion flow to predict maize starch explosions in a 12 m³ silo. The flow field after ignition, flame propagation velocity and pressure development histories etc. during the explosion, are calculated. The data of non-uniform initial conditions including dust concentration, flow velocity and turbulent RMS velocity in the silo for this model are adopted from Hauert, Vogl and Radandt (1994) [Hauert, F., Vogl, A., Radandt, S. (1994). Measurement of turbulence and dust concentration in silos and vessels. 6th international colloquium on dust explosions (pp. 71–80), Shenyang, China, August 28–September 2, 1994.]. A simple concept of dust granule taking into consideration dust dispersion efficiency is proposed and introduced. The Lagrangian method is used to trace trajectories and granules, so it is easier to consider particle size distribution. The k−ε model is used to simulate the turbulence of the gas phase, and the particle's pulsation is modeled by random vector wind generated by the surrounding gas. In the combustion model, vaporization of water, volatilization of volatile, gas phase reaction and the particle's surface reaction are taken into account.     

对称障碍物条件下瓦斯爆炸火焰与压力波耦合作用研究

为了研究对称障碍物条件下瓦斯爆炸压力波与火焰传播的耦合作用,在150 mm×150 mm×1 700 mm的有机玻璃瓦斯爆炸管道中,距离点火端不同距离安装0.5阻塞率的对称障碍物,进行8.5%甲烷体积分数的爆炸试验,采集瓦斯爆炸的超压信号并同步拍摄火焰传播图像。结果表明:火焰穿越板式对称障碍物的过程经历了火焰加速、火焰降速到火焰再加速的过程,火焰降速的时间仅为5 ms。距离点火焰源不同长度的对称障碍物在火焰加速过程中的作用存在明显差异,近点火源的障碍物作用主要为诱导湍流,远离点火源的障碍物作用主要为湍流增强。     

甲烷爆炸传播过程膜状障碍物的激励效应研究

针对管状空间内膜状障碍物对甲烷爆炸传播的激励效应现象,基于机理分析进行了数值模拟和实验研究,计算分析薄膜附近爆炸冲击波压力峰值大小与火焰速度变化,同时运用激波管道进行相同工况条件下的实验,并对两者结果对比分析,发现有无膜状障碍物的压力峰值相差6倍以上。研究表明,膜状障碍物的激励效应是破膜以后形成的带压燃烧,提高了燃烧速率,导致甲烷爆炸的火焰传播速度剧增。实验结果一定意义诠释了同样数量的甲烷气体爆炸在不同环境内后果上的巨大差异,研究结果对矿井瓦斯爆炸事故调查及防治具有指导意义。     

2,5-二甲基呋喃-空气燃烧过程研究

利用球形发展火焰研究了常温常压下不同当量比,不同相态时2,5-二甲基呋喃-空气的层流燃烧速度和马克斯坦长度,分析了火焰拉伸对火焰传播速度的影响。研究结果表明:随着当量比的增加,2,5-二甲基呋喃-空气混合气的马克斯坦长度减少,火焰的稳定性减弱。并且分别计算出当量比为1.25和1.5的层流燃烧速度,分别为:1.189m/s,1.135m/s.。对于同一当量比1.5的情况下,不同相态的2,5-二甲基呋喃-空气混合物,在相同时刻的气液两相混合物的火焰半径已经拉伸火焰传播速度远远大于纯气相的混合物。     

有障碍物半开口管道内氢气燃烧数值模拟研究

基于有障碍物氢气燃烧实验装置进行数值模拟研究,采用Fluent软件分析了半开口管道内障碍物对氢气/空气燃烧特性的影响。结果表明:障碍物会促进实验管段内氢气火焰加速,随着障碍物阻塞率和数量的增加,火焰加速更快且燃烧压力峰值更大;在相同阻塞率下,障碍物形状对氢气火焰速度和燃烧压力峰值的影响很小;燃烧压力随障碍物间距的增大先增大后减小,障碍物间距为3倍管道内径时产生的燃烧压力峰值最大。     

Effects of moisture and particle size distribution on flame propagation of L-lysine sulfate powder

Lysine is an essential amino acid for human body, and lysine sulfates are at risk of fire and explosion during the production and processing. However, there is no public report on the lysine sulfate powder explosion hazard research. In this paper, the effects of moisture, mass concentration and particle size on the flame propagation behaviors of L-lysine sulfate powder were studied in a vertical pipe. The results showed that the flame propagation could be divided into 3 stages: free propagation, acceleration and attenuation, in which the acceleration was owed to the positive feedback of combustion reaction, gas expansion and turbulence. Moisture content could promote the flame propagation of L-lysine sulfate powder to a certain extent, but it had a strong inhibitory effect on the explosion when the moisture content was too large. The flame propagation velocity increased with the decrease of the average particle size of powder,.With the increase of the particle concentration, the flame propagation velocity of powder explosion increased first and then decreased, that was, there was an optimal concentration of powder explosion, and the powder was more sensitive to the change of concentration in the range of low concentration.     

水平管内不同煤质煤尘爆炸火焰传播特性实验研究

为研究水平管道空间不同煤质煤尘爆炸火焰传播特性，选取褐煤、长焰煤、不粘煤、气煤4种煤尘，对爆炸火焰焰峰特性、火焰加速传播特性、火焰传播距离与持续时间展开研究。研究结果表明:褐煤在500 ms内焰峰的形状由尖锐向平滑再向钝化不断演变，长焰煤与不粘煤在375 ms时焰峰前端出现明显焰体分离现象，分析认为这与管体冷壁效应、空间尺度效应及空间氧气消耗直接相关；气煤在375 ms时焰峰出现大面积火焰碎纹，说明气煤爆炸火焰猛烈传播的持续时间相对较短，整体爆炸强度相对较弱；褐煤与长焰煤爆炸火焰存在2次间断性加速，分析认为这与管体空间受限、常温管壁散热、局部助燃氧气瞬间不足等因素有关；褐煤在爆炸后400～600 ms内火焰2次加速完全，火焰传播距离达740 mm，明显大于长焰煤、不粘煤与气煤，说明低变质褐煤爆炸火焰持续时间更长，火焰传播距离更远且传播更剧烈；虽然气煤火焰最远传播距离比长焰煤大30 mm，但由于气煤火焰在375 ms左右出现大片火焰碎纹，因此气煤整体的爆炸强度小于长焰煤。     

3m直径煤油池火灾火焰特性的数值研究

为了预测油池火灾的火焰特性,采用CFD模拟技术开展静风状态下3 m直径煤油液池的火灾场景模拟,探讨火焰温度、火焰羽流速度、辐射热通量、燃烧产物质量分数等油池火焰特性参数随高度的变化关系;并结合火焰形态分布,提出一种4区域模型,即将湍流扩散火焰划分为油气混合燃烧区、燃烧火焰区、烟尘区和热烟气区来分析燃烧气流在不同高度的实际物理化学特性。此外,通过经验公式和CFD模拟2种方法分别计算出3 m直径煤油池火灾的火焰高度、火焰表面的辐射通量及热辐射破坏半径,并对计算结果进行比较分析,结果表明:2种方法可互相补充完善,有助于池火灾的热辐射危害性评估。     

T型管道不同封闭状态瓦斯爆燃火焰传播特征

为了研究分岔管道不同封闭状态下瓦斯爆燃火焰阵面传播规律,在自制的T型透明分岔管道内,设置支管端口完全封闭、直管左端口弱封闭,采用光电传感器和压力传感器测试了直管右端弱封闭、完全封闭2种情况下,预混甲烷-空气可燃气体爆燃火焰传播过程中速度、超压参数的变化情况。结果表明:由于分岔的存在,2种封闭状态在支管端点火后瓦斯爆燃火焰阵面在支管中的传播速度均先增大后减小;直管右端弱封闭时,经过分岔后火焰加速向直管两端传播速度基本一致,分别达到86.29 m/s和88.07 m/s;直管右端完全封闭时,火焰向弱封闭端传播速度增大至166.67 m/s,火焰向完全封闭端传播时并不断压缩未燃气体产生高压振荡反馈导致火焰振荡传播现象,火焰速度不断减小至4.84 m/s;管道内瓦斯爆燃超压均迅速上升到达峰值,之后受压缩气体的膨胀和冲击后爆燃产物的振荡作用迅速下降。     

泄爆夹层内障碍物对泄爆效果影响的数值模拟研究*

为研究泄爆夹层内障碍物位置对燃气泄爆效果的影响,以某大型商业综合体暗厨房为研究对象,考虑泄爆夹层中结构梁不同位置的泄爆效果,对暗厨房燃气爆炸的泄爆过程开展数值模拟研究。研究结果表明:在火焰没有到达泄爆窗前的爆炸初始阶段,障碍物对火焰结构和传播速度基本没有影响,当火焰进入泄爆夹层后,障碍物的存在可引发火焰加速现象;当障碍物距离泄爆窗1.7 m时,火焰加速现象较为明显,火焰最大传播速度可达591.5 m/s,此时厨房内压力峰值约2.9 MPa,约为没有结构梁情况下1.42倍;障碍物距离泄爆窗较近时,二者将协同影响火焰传播;厨房内压力峰值随着障碍物与泄爆窗距离的增大遵循增大-突降-增大的规律。研究结果可为商业综合体暗厨房泄爆设计提供一定理论依据。     

障碍物场中预混燃烧火焰的数值模拟

利用k-ε湍流模型和拉切滑(SCASM)预混燃烧模型,对障碍物场中预混燃烧火焰进行了三维空间数值模拟。通过对控制方程添加不同的源项以反映障碍物对流场的影响,采用交错网格控制容积法将计算区域进行离散,用SIMPLE算法求解离散控制方程。模拟结果表明,障碍物的存在改变了燃烧流场的结构,成为加速燃烧甚至诱导爆炸过程的不稳定因素。该研究结果对有效预测障碍物场中火焰走势及其流场的分布情况,加强人们对火焰传播规律的认识,对预防工业灾害有重要参考价值。     

连通容器气体密闭爆炸与泄爆过程的实验研究

利用球型容器与管道组合,开展连通容器气体爆炸与泄爆实验,分析连通条件下,火焰在管道中的传播过程及其对起爆容器和传爆容器的压力影响。实验结果表明:连通容器气体爆炸中,火焰从起爆容器到传爆容器传播经历了一段不断加速,但加速度不断减小的过程;泄爆过程中,火焰传播过程与密闭爆炸时基本一致。管道中火焰加速传播,使得传爆容器的爆炸压力和强度相较于作为起爆容器时均明显增加,危险更大,采用与起爆容器相同的泄爆面积,无法满足对连通容器中传爆容器的泄爆。同时,泄爆是一个快速的能量泄放过程应选择合理的泄爆方式,防止二次危害。     

球形障碍物对瓦斯爆燃火焰影响试验研究

为进一步开发煤矿井下瓦斯爆炸事故的隔抑爆技术装备,利用截面为0.2 m×0.2 m的方形管道、纹影仪和高速摄像机,开展无障碍物时和球形障碍物存在情况下的瓦斯爆燃传播试验。研究发现,无障碍物时,密闭管道内爆燃火焰的结构和传播速度受反射压力波的影响很大,湍流火焰、化学反应作用能力与反射压力波的相互作用是造成火焰传播速度变化的主要原因;球形障碍物存在时,火焰受扰动后被拉伸为前锋、中锋和尾锋,前锋速度最快,尾锋最慢;火焰前锋从经过障碍物开始整体呈加速趋势,与无障碍物相比,通过观察段的时间明显缩短。