密闭受限空间可燃气体爆炸特性数值模拟研究

密闭受限空间中可燃气体的爆炸研究对于石油及天然气工业的安全生产具有重要意义.以RNG湍流模型及EBU-Arrehnius燃烧模型为基础,建立了可燃气体单步化学反应湍流爆炸模型,以有限体积法求解爆炸流动及反应控制方程,从而对二维受限空间中可燃气体爆炸的过程及规律进行了数值模拟,模拟结果与实验数据有着较好的吻合性.所做的工作为受限空间中可燃气体爆炸特性及规律的进一步研究及工业防爆抑爆技术的工艺实施、系统设计和关键参数计算提供了理论依据.     

爆炸性气体在连续拐弯管道中传播特性的实验研究

针对复杂燃气管网燃气爆炸致灾严重,传播规律复杂的问题,利用实验室加工成的连续拐弯管道,模拟研究了复杂燃气管网爆炸性气体通过连续拐弯管道时的火焰传播速度、爆炸波超压变化情况。研究结果表明,当整个管道内充满瓦斯气体时,通过连续拐弯后,火焰传播速度和爆炸波超压值产生显著变化,在连续拐弯管道拐弯处为一扰动源,诱导附加湍流,气流湍流度增大,管道拐弯增加了燃烧区的湍流度,火焰燃烧产生加速度,加速燃烧产生更大能量以推动加速传播。研究结果对指导现场如何防治复杂燃气管网气体爆炸,减轻爆炸的威力具有重要作用。     

管道燃气爆炸特性实验研究

管道是化工及油气储运系统的重要组成部分,却时常受燃烧爆炸事故的威胁,因此对管道中燃气燃烧爆炸特性与规律的研究就十分必要。以甲烷作为研究对象,采用压力传感器以及火焰传感器等对水平封闭管道内甲烷-空气预混燃烧爆炸进行了实验研究,通过大量实验来研究可燃气体爆炸压力与火焰及其传播变化规律。根据实验结果将超压以及气体燃烧的变化情况,对前驱冲击波与火焰面的相对时间及相对位置关系进行了分析。结果显示,管道中会产生前驱压力波,并超前火焰阵面甲烷气体在管道传播过程中,出现冲击波反压射、波叠加及反冲现象,压力的持续时间较火焰光信号持续时间长。所做的工作为油气受限空间中燃气燃烧爆炸特性与规律的进一步研究及工业防爆抑爆技术及工艺的实施、系统设计以及关键参数计算提供了理论依据。     

地下复杂组合受限空间火灾分区现象与初期模式实验研究

主要介绍地下狭长与组合受限空间油料介质火灾分区现象、初期火灾主要模式模拟实验研究结果与讨论;地下组合受限空间火灾呈现出特殊的分区现象。一般可分为燃烧区、新鲜空气补充区、烟气流区、过渡区和火焰后面的“惰化区”五区。有上下两层的地下复杂组合受限空间可分为燃烧区、烟气流区、新鲜空气补充区和“惰化区”4区。地下受限空间(包括组合受限空间、容积式受限空间和狭长受限空间)密闭条件下火灾初期模式主要有：爆炸、爆炸减弱、爆炸增强、燃烧、爆燃向爆轰发展。地下复杂组合受限空间下部与下部狭长受限空间分别全开口条件下着火后火灾主要模式为爆炸、燃烧、爆炸后持续燃烧、爆炸后短时燃烧、爆炸后发展为出口外爆炸;爆炸又可分为爆炸强度逐步加强、爆炸由爆燃发展为爆轰、爆炸强度逐步减弱。     

球形容器内可燃气体泄爆过程的数值模拟

利用流体力学软件Fluent对球形容器泄爆过程中流场进行数值模拟,分析泄爆导管长度和泄放压力对爆炸压力和爆炸强度的影响,以及泄爆过程中火焰阵面和速度场的变化。研究表明,泄爆过程增大了燃烧火焰的面积,燃烧火焰在泄爆过程中发生湍流,燃烧速度得到极大地加速,泄爆导管对于容器内的高压气体的泄放起到了约束作用,泄爆导管的长度是影响泄爆过程中容器内部压力变化的重要因素。     

障碍物对开敞空间贫燃天然气爆炸特性的影响研究

为揭示贫燃条件下障碍物对开敞空间天然气爆炸特性的影响,试验记录了火焰传播形态和爆炸压力,并对火焰结构和压力空间分布进行了数值分析.结果表明:在无障碍物工况下,火焰近似以球形向外膨胀传播,火焰表面较为连续,火焰传播速度较慢,爆炸压力较低;而在障碍物的湍流扰动下,火焰表面出现较大的"褶皱"结构,火焰燃烧表面积显著增大,火焰传播速度升高,爆炸压力也相应增大.相比于由障碍物引起的火焰加速作用,因流体动力学不稳定性产生的失稳效应可忽略不计.由温度分布可清晰观察火焰表面"褶皱"结构的形成过程,计算所得的爆炸压力达到峰值时间较早,且超压峰值相比试验值较低.     

可燃气体爆炸破坏效应的试验研究

借助高速摄像机及ProAnalyst软件,研究可燃气体体积分数和障碍物对可燃气体爆炸破坏力的影响。测定不同体积分数下的甲烷-空气预混气体爆炸冲击波超压,和爆炸火焰波在有无乒乓球方向传播的平均速度。试验结果表明:超压和平均速度均随着甲烷体积分数的增加呈现先增大后减小的变化趋势,其最大值均出现在甲烷体积分数为10%～11%之间;同一体积分数下的甲烷-空气预混气体爆炸火焰波在有乒乓球方向传播的平均速度比没有乒乓球方向传播的平均速度大。根据试验结果,推导出可燃气体爆炸冲击波超压和爆炸火焰波传播平均速度与可燃气体体积分数之间的函数关系,并得出障碍物对爆炸火焰波传播的加速作用随着体积分数的增加呈现先加强后减弱的变化趋势。     

多孔球形材料阻火抑爆性能影响因素数值模拟研究

为探究影响多孔球形材料阻火抑爆性能的主要因素,采用气体爆炸模拟软件FLACS建立多孔球形结构中湍流燃烧模型,对填充多孔球形材料后丙烷/空气预混气体燃烧爆炸过程进行数值模拟。研究结果表明:多孔球形材料能够有效衰减爆燃压力波、阻隔火焰传播,起到阻火抑爆作用,且压力波衰减程度和火焰阻隔效果与多孔球形材料的尺寸、孔径及填充密度密切相关。当多孔球形材料的直径为25 mm、孔径为3 mm、填充密度为20层时,压力波衰减程度最大,火焰阻隔效果最明显,说明直径和孔径越小,填充密度越大,材料的阻火抑爆性能越强。     

柱形压力容器开口泄爆过程数值模拟研究

为研究柱形压力容器泄爆规律,采用经典流体力学软件FLUENT对典型的柱形压力容器泄爆过程进行数值模拟,分析从泄爆口开启到泄压结束时间段压力发展、火焰传播、气体流动及可燃气体浓度变化特性。结果表明:不同泄爆压力下容器内压力发展变化呈现不同特点,在较小泄爆压力情况下会出现压力再度上升的双峰现象。泄爆过程中产生的湍流沿泄爆口附近容器壁拉长火焰面,并加快燃烧速率。同时就容器内不同点火位置对爆炸强度影响进行研究,得出在泄爆压力为0.04 MPa时,底面点火对本柱形压力容器产生的最大升压速率约为中心点火最大升压速率的1.4倍。     

不同浓度甲烷-空气预混气体爆炸特性的试验研究

利用自主搭建的易爆气体爆炸试验平台,研究了甲烷体积分数为8%、9%、9.5%、10%、11%的甲烷-空气混合气体的爆炸特性。结果表明:爆炸火焰在管道内经历了层流火焰传播加速、郁金香火焰传播速度变慢和湍流火焰传播速度增大3个特征阶段;爆炸管道压力表现出升压、振荡和反向冲击3个变化阶段;爆炸感应期、火焰最大传播加速度和最大爆炸升压速率等特征参数能更好地反映易爆气体的爆炸能力和爆炸强度。结合爆炸火焰图片、光电传感信号和压力传感信号发现,在一端开口的管道内,爆炸压力出现变化的时间总是先于火焰传播速度的变化时间,表明爆炸压力的变化是导致火焰传播速度变化的原因。因此,抑爆过程中,减小爆炸压力和降低升压速率是达到良好抑爆效果的关键。     

Numerical simulation and study on the transmission law of flame and pressure wave of pipeline gas explosion

Based on FLUENT simulation software, the laws of transmission of flame and pressure wave in pipeline gas explosion were studied. It turned out that, the maximum pressure value of the explosion point is not the maximum value of the whole explosion process; the maximum pressure value of the pressure wave lowers firstly near the explosion point, then rises to a peak, and then drops gradually; two waves divide the space in the pipeline into three sections during the gas explosion transmission. The result is basically consistent between numerical simulation and experiment, and the conclusion from the simulation provides theoretical basis for research on explosion-proof and suppression devices for underground gas pipeline, as well as for technical regulations of installation.     

多分支管道油气爆炸特性大涡模拟

为了研究油库常见的分支结构空间内发生油气爆炸时火焰和压力的传播特性,建立了基于WALE湍流模型及Zimont预混火焰模型的油气爆炸模型;模拟了6种不同分支管道结构空间内汽油/空气混合物爆炸发生发展过程;研究了分支管道数量及相对设置位置对爆炸超压的影响规律,以及分支管道对火焰传播形态和速度的影响规律;模拟结果与前人相关实验规律进行对比。研究结果表明:分支管道对汽油/空气混合气预混爆炸具有明显的强化激励作用;火焰锋面传播经过分支管道时,经历规则—褶皱—规则的变化过程;主管道内火焰传播速度,在分支管道对流场的突扩作用和湍流作用的共同影响下呈震荡变化的规律。     

Experimental study of the venting characteristics of dust explosion through a vent duct

To further understand the dynamic mechanism of dust explosion through a vent duct, we designed a small-scale cylindrical vessel connected with a vent duct and performed a dust explosion venting experiment under different opening pressures using corn starch as the explosive medium in this study. The results show that weakening effect of duct on venting is positively correlated with the opening pressure. The explosion pressure in the duct presents a three-peak-structure with time, successively caused by the membrane breaking shock wave, the secondary explosion in the tube, and the continuous combustion, and decreases gradually with the propagation distance. Meanwhile, the three pressure peaks are positively correlated with the opening pressure, while the time interval between them goes to contrary. The increase of opening pressure leads to the increase of secondary explosion intensity and reverse flow in the vessel, further accelerates the reaction rate in the vessel, and then shortens the duration of combustion in the vessel until the phenomenon of flame reignition in the vessel disappears.     

泄爆面特征参数对天然气爆炸超压峰值的影响规律

为揭示泄爆面特征参数对大尺度受限空间内天然气爆炸超压峰值结构的影响机制,基于典型房间特征,借助计算流体动力学技术研究不同泄爆面开启压力、开启时间以及泄压比等参数条件下室内天然气泄爆超压峰值结构的分布规律。研究结果表明:峰值Pb随开启压力和开启时间增加均呈线性增长趋势,而泄压比对Pb影响较小;峰值Pmfa与室内最大火焰面积有关,随开启压力、开启时间的增加和泄压比的减小,气体出流速度增大,进而产生更强的湍流,导致室内火焰面积和气体燃烧率增加,最终Pmfa增大;峰值Pext随泄压比增加呈快速降低趋势,同时开启压力和开启时间对Pext影响具有协同效应,共同促进Pext快速增加。     

Effect of flame propagation regime on pressure evolution of nano and micron PMMA dust explosions

Experiments using an open space dust explosion apparatus and a standard 20 L explosion apparatus on nano and micron polymethyl methacrylate dust explosions were conducted to reveal the differences in flame and pressure evolutions. Then the effect of combustion and flame propagation regimes on the explosion overpressure characteristics was discussed. The results showed that the flame propagation behavior, flame temperature distribution and ion current distribution all demonstrated the different flame structures for nano and micron dust explosions. The combustion and flame propagation of 100 nm and 30 μm PMMA dust clouds were mainly controlled by the heat transfer efficiency between the particles and external heat sources. Compared with the cluster diffusion dominant combustion of 30 μm dust flame, the premixed-gas dominant combustion of 100 nm dust flame determined a quicker pyrolysis and combustion reaction rate, a faster flame propagation velocity, a stronger combustion reaction intensity, a quicker heat release rate and a higher amount of released reaction heat, which resulted in an earlier pressure rise, a larger maximum overpressure and a higher explosion hazard class. The complex combustion and propagation regime of agglomerated particles strongly influenced the nano flame propagation and explosion pressure evolution characteristics, and limited the maximum overpressure.     

Nonlinear distribution characteristics of flame regions from methane–air explosions in coal tunnels

High temperature flame fronts generated in methane–air explosions are one of the major hazards in underground coal mines. However, the distribution laws of the flame region in explosions of this type and the factors influencing such explosions have rarely been studied. In this work, the commercial software package AutoReaGas, a finite-volume computational code for fluid dynamics suitable for gas explosion and blast problems, was used to carry out numerical simulations of a series of methane–air explosion processes for various initial premixed methane–air regions and cross-sectional areas in full-scale coal tunnels. Based on the simulated results and related experiments, the mechanism of flame propagation beyond the initial premixed methane–air region and the main factors influencing the flame region were analyzed. The precursor shock wave and turbulence disturb the initial unburned methane–air mixture and the pure air in front of the flame. The pure air and unburned mixture subsequently move backward along the axial direction and mix partially. The enlargement of the region containing methane induces that the range of the methane–air flame greatly exceeds the initial premixed methane–air region. The flame speed beyond the initial region is nonzero but appreciably lower than that in the original premixed methane–air region. The length of the initial premixed methane–air region has substantial influence on the size of the flame region, with the latter increasing exponentially as the former increases. For realistic coal tunnels, the cross-sectional tunnel area is not an important influencing factor in the flame region. These conclusions provide a theoretical framework in which to analyze accident causes and effectively mitigate loss arising from the repetition of similar accidents.     

矿井瓦斯爆炸传播的尺寸效应研究

基于瓦斯爆炸传播过程的理论分析 ,确定了表征瓦斯爆炸传播过程的主要物理参数 ;通过在两条巷道中进行了瓦斯爆炸传播的对比实验 ,指出了瓦斯爆炸传播过程的尺寸效应存在的原因。笔者认为 :因为巷道支护设备使巷道有效面积的减少和壁面粗糙度的变化 ,尺寸效应使大断面巷道在可比条件下 ,发生瓦斯爆炸时 ,爆炸波的火焰、压力、冲量等在更大范围内形成破坏和伤害