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。     

刚/柔性障碍物对甲烷/空气预混气体泄爆动力学的影响

为探究刚/柔性障碍物对甲烷/空气泄爆行为的影响，采用自主搭建的连接容器(20 L球形容器连接4 m长爆炸管道和0.5 m长泄压管道)试验系统，研究不同阻塞比与厚度的刚性/柔性障碍物对甲烷/空气爆炸超压及泄爆火焰的影响。结果表明，在球形容器内，随阻塞比和厚度增加，峰值超压与最大升压速率相应增大，在阻塞率为80%和厚度为0.40 mm时峰值超压分别达到了190.4 kPa和273.5 kPa,最大升压速率分别为4.32 MPa/s和7.32 MPa/s。在管道末端，随柔性障碍物厚度增加，爆炸超压与升压速率同样大幅度提升。而随刚性障碍物阻塞比增加，峰值超压和最大升压速率先上升后下降。在设置刚性和柔性障碍物后，泄爆管道内均出现二次爆炸的现象，不同的是，二次爆炸的剧烈程度随柔性障碍物厚度增加而上升，而随刚性障碍物阻塞比增加呈现先增加后降低的趋势。     

障碍物对采用泄爆管泄放气体爆炸影响的数值模拟

采用k-ε湍流模型和漩涡耗散概念模型(EDC)建立了泄爆管泄放气体爆炸的模型,并模拟容器内置障碍物时泄爆管泄放气体爆炸火焰的传播过程,分析了障碍物形状、阻塞率、位置、个数对超压(pred)和压力上升速率的影响.结果表明:障碍物的出现导致燃烧速度和pred上升,正方形障碍物导致的爆炸后果最严重;增加障碍物个数或增大障碍物阻塞率均可增加超压和燃烧速度;障碍物置于容器中心,爆炸后果较强,而靠近点火源或泄爆口,后果有所减弱.     

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。     

CO2-超细水雾对瓦斯/煤尘爆炸抑制特性研究

为了解CO2-超细水雾对瓦斯/煤尘爆炸抑制特性，用自行搭建的实验系统，从超压、火焰传播速度和火焰结构3个方面研究了CO2-超细水雾形成的气液两相介质对9.5%瓦斯/煤尘复合体系爆炸的抑爆效果、影响因素与原因。研究结果表明:随着CO2体积分数和超细水雾质量浓度的增加，爆炸火焰最大传播速度、爆炸超压峰值均出现明显下降，火焰到达泄爆口时间显著延迟；尤其当CO2体积分数达到14%与超细水雾的共同抑爆效果凸显，瓦斯/煤尘复合体系爆炸超压的“震荡平台”消失，同时火焰结构呈现“整体孔隙化”。所得结论为煤矿井下高效防爆抑爆技术进行了完善和增强。     

障碍物对油气-空气混合气体泄压爆炸火焰传播特性影响

为了研究障碍物对油气泄压爆炸火焰传播特性的影响规律,进行了不同数量障碍物工况下的对比实验,并利用纹影仪和高速摄影仪记录了火焰传播过程,针对障碍物对火焰形态、火焰锋面位置及火焰传播速度的影响规律进行了研究,结果表明:圆柱体障碍物会导致油气泄压爆炸火焰形态产生褶皱和弯曲变形,诱导层流火焰向湍流火焰转变,加速火焰的传播,对油气泄压爆炸火焰的初始传播形态有显著影响;随着障碍物数量的增多,火焰锋面传播距离点火端的最大距离增大,但到达最远距离的时间减少;障碍物能够增强火焰的传播速度,尤其对障碍物下游火焰影响最为显著,随着障碍物数量的增多,火焰传播的最大速度也随之增大,但达到最大火焰传播速度的时间却随之减少;障碍物的存在增大了油气泄压爆炸过程外部爆炸压力,并且随着障碍物数量的增多,外部爆炸压力峰值增长幅度增大。     

水雾喷洒时间对滑移装置下甲烷爆炸特性影响

为提升滑移装置抑爆效果，在方形管中通入体积分数为9.5%甲烷/空气预混气体，分析细水雾协同不同弹性系数滑移装置作用下，水雾起始喷洒时间对预混气体爆炸特性影响。结果表明：先喷、指尖喷出现坡形火焰二次加速火焰传播，爆炸反应加剧，水雾不同程度充当障碍物加速火焰传播和碰壁断链，缩短火焰熄灭时间；后喷细水雾障碍物作用微弱，利用吸热降温作用抑制火焰传播，熄灭耗时相对较长。在爆炸超压方面，0.22 N/mm、0.42 N/mm 2种弹性系数滑移装置协同作用，先喷情形超压峰值增幅分别为9.25%、16.55%,指尖喷情形则高达88.71%、77.37%,促爆效果明显。后喷有一定的抑爆作用，超压峰值降幅分别为7.11%、2.93%。综上，后喷的抑爆效果优于先喷和指尖喷。     

泄爆导管长度对除尘器泄爆影响的模拟分析

使用FLACS软件DESC模块,对连接不同长度泄爆导管的除尘器泄爆模型进行了模拟,研究泄爆过程中除尘器内部以及泄爆方向上的超压与高温变化规律。研究结果表明,泄爆导管内部要比除尘器内部先达到最大爆炸压力,但压力值却要小于除尘器内的超压;在泄爆方向上,距泄爆口越远,导管内的爆炸压力也越小,且在泄爆导管末端压力下降的趋势明显加快;随着导管长度从1 m增加到6 m,除尘器与泄爆导管内部的最大爆炸压力也逐渐增大,在泄爆导管长6 m时,除尘器内部达到了81.8 kPa的最大爆炸压力;而对于不同长度的导管泄爆模型,泄爆导管内部都达到了2 000 K左右的高温,且导管越长,最大爆炸温度所能持续的时间也越长。     

有障碍物开敞空间可燃气云爆炸超压场的数值模拟

利用计算流体动力学软件AutoReaGas定量研究障碍物、障碍物阻塞比对开敞空间可燃气云爆炸超压场的影响以及爆燃超压随测点距离变化的分布规律。研究结果表明:当有障碍物存在时,爆炸峰值超压会显著增加,且峰值超压随着障碍物阻塞比的增加而增加。对于有障碍物条件下开敞空间的丙烷气云爆炸,无论是气云内部还是气云外部,随着距爆心距离的增加,峰值超压都有减小的趋势。     

瓦斯爆炸后空间温度分布及热危害区域分析研究

为了获得瓦斯爆炸引发次生灾害的特性参数，建立了超压预测模型及爆炸后空气温度衰减模型，并结合实验数据进行了验证。结果表明:依据所建立的超压修正模型，不同浓度和体积下的超压在爆源附近呈对数形式快速下降，之后缓慢趋向平稳；基于模型修正的爆炸超压计算公式，能够很好的对各个情形的瓦斯爆炸超压进行计算，吻合较好。对初始瓦斯体积相对较小的情形吻合度很高，对于初始体积大的瓦斯爆炸超压在100 m附近会出现一定误差，但有一定指导意义。瓦斯爆炸热危害区域的研究，对瓦斯爆炸次生灾害的防治工作具有重要意义。     

含弱约束端面直角管道汽油蒸气爆炸及七氟丙烷抑爆研究*

为研究七氟丙烷对汽油蒸气爆炸抑制作用,搭建含弱约束端面直角管道汽油蒸气爆炸抑制实验系统,开展汽油蒸气爆炸实验研究,并与喷入七氟丙烷抑爆介质进行对比,分析爆炸超压值、火焰强度值和火焰传播速度等爆炸特性参数变化情况。结果表明:在1.3%,1.5%和1.7%汽油蒸气体积分数下,不加抑爆介质时,爆炸超压值、火焰强度和火焰传播速度随着汽油蒸气体积分数的升高而增大;将七氟丙烷作为抑爆介质喷入时,爆炸超压峰值分别下降91.06%,34.57%和50.92%,火焰强度降幅达到99.83%,火焰传播速度几乎降为0,火焰持续时间随之缩短几乎为0,七氟丙烷具有良好的阻隔防爆效果。     

Effects of vent layout and vent area on dynamic characteristics of premixed methane-air explosion in a tube with two side-vented ducts

To further elucidate the influence mechanism of side vents on the dynamic characteristics of gas explosions in tubes is helpful to design more reasonable vent layouts. In this paper, 9.5% methane-air explosion experiments were conducted in a tube with two side-vented ducts, and the effects of vent layouts and vent areas on the dynamic characteristics of explosion overpressure and flame propagation speed were investigated. The results demonstrate that under the same condition with a single vent area of 100 mm × 100 mm, when only the end vent is open, the maximum explosion overpressure and the maximum flame propagation speed are the highest among the five vent layouts. When the side vents 1 and 2 and the end vent are open, the maximum explosion overpressure is the lowest, and an unusual discovery is that the flame front changes into a hemispherical shape, finger shape, quasi-plane shape, tulip shape and wrinkled structure. When only side vent 1 is open, a unique Helmholtz oscillation occurs, and a new discovery is that there is a consistent oscillation relationship among the overpressure, flame propagation speed and flame structure. Helmholtz oscillation occurs only when a single vent area is 100 mm × 100 mm–60 mm × 60 mm, and the oscillation degree decreases with decreasing vent area. During the vent failure stage, the maximum explosion overpressure is generated, the flame front begins to appear irregular shape, and the flame propagation speed shows a prominent characteristic peak. After the vent failure stage, the driving effect of the end vent on the flame is higher than that of the side vent on the flame. Furthermore, the correlation equations of the mathematical relationships among the maximum explosion overpressure P_red, the static activation pressure P_stat and the vent coefficient K_v under four vent layouts are established, respectively.     

条形障碍物对瓦斯爆炸特性影响研究

我国煤矿瓦斯爆炸事故不断出现,造成了巨大的人员伤亡和经济损失,在置障条件下研究瓦斯爆炸特性,对预防和减少瓦斯爆炸事故具有重要意义。利用水平管道式爆炸试验装置,研究密闭管道内条形障碍物的数量和阻塞率对管道内瓦斯最大爆炸压力、火焰速度、最大爆炸压力上升速率和爆炸指数的影响以及敞口状态的影响。研究表明:障碍物对瓦斯爆炸具有显著激励作用,管道内瓦斯最大爆炸压力、火焰速度、最大爆炸压力上升速率和爆炸指数均显著增大,随着障碍物数量和阻塞率的增加,激励作用越明显;敞口状态下管道内最大爆炸压力、最大爆炸压力上升速率和爆炸指数均显著减小,火焰持续传播。研究结果对防治煤矿瓦斯爆炸事故提供一定的理论支持。     

Influence of built-in obstacles on unconfined vapor cloud explosion

The obstacle structure in the vapor cloud has a significant influence on the gas explosion. Obstacles could not only lead to the acceleration of flame, but also they may occupy some space, thus affecting the amount of combustible gas. In this paper, a new two-step method was proposed to respectively study the effects of the obstacles amount and volume blockage ratio (VBR) on the gas explosion by using Computation Fluid Dynamic software AutoReaGas, and the obstacles in the vapor cloud were set to “Solid” instead of “Subgrid”. Based on the results and analysis, it is found that the peak overpressure and the maximum combustion rate rise with the increase of the number of obstacles for a single VBR, which indicated that the vapor cloud explosion of more obstacles was more dangerous for a single VBR. However, under a single number of obstacles, the peak overpressure and the maximum combustion rate increase firstly and then decrease as VBR increases and reach the highest at the VBR of 0.74, which indicated that the intensity of vapor cloud explosion reach a peak at a certain VBR in the middle instead of the largest. In addition, the existence and structure of obstacles have little effect on the size of explosion fireball when the size and concentration of combustible gas cloud are the same.     

Experimental study on unconfined methane explosion: Explosion characteristics and overpressure prediction method

Explosion accidents have become the main threat for the high-efficiency use of cleaner gas energy sources, such as natural gas. During an explosion, obstacle causing flame acceleration is the main reason for the increase of the explosion overpressure, which still remains to be fully understood. In this research, field experiments were conducted in a 1 m³ cubic frame apparatus to investigate the effect of built-in obstacles on unconfined methane explosion. Cage-like obstacles were constructed using square steel rods with different cross section size. The results demonstrated that the flame could get accelerated due to the hydrodynamic instability and obstacle-induced turbulence, which enhanced the explosion overpressure. In the near field, the overpressure wave travelled slower and the maximum overpressure could almost keep constant. Reducing the cross section size, or increasing the obstacle height or the obstacle number per layer could determine the rise of the maximum overpressure, the maximum pressure rising rate and the overpressure impulse. For uniformly constructed obstacles, self-similar theory was chosen to measure the influence of the hydrodynamic instability, and a parameter β was adopted to measure the flame acceleration caused by obstacle-induced turbulence, the value of which was 2 in this research. Based on the acoustic theory, an overpressure prediction model was proposed and the predicted results agreed with the measured values better than previous models, such as TNT equivalency model and TNO multi-energy model.     

Study on the characteristics of gas explosion affected by induction charged water mist in confined space

To investigate the suppression effect of charged water mist on gas explosion, a small charged water mist generator and a gas explosion simulation device were designed based on the principle of electrostatic induction. Experiments for testing characteristics of the gas explosion in a confined space under different charged polarities, charged voltages and mist fluxes were carried out. Experimental results indicated that, compared with the normal water mist, the explosion peak overpressure and the flame propagation speed could be more effectively reduced by the charged water mist. And this suppression effect could be promoted by increasing the charged voltage. To visualize the effect of the charged water mist's polarity on gas explosion, comparative experiments were conducted. The results showed that the explosion peak overpressure, the overpressure rising rate, and the propagation speed of the flame were reduced by 64.7%, 33.0% and 19.4%, respectively, when a +8 kV charged voltage was applied. In situation where a -8 kV charged voltage was applied, 64.1%, 26.5% and 16.0% reductions were achieved for the explosion peak overpressure, the overpressure rising rate, and the flame propagation speed respectively. Comparison of this data leads to the conclusion that the gas explosion could be more efficiently suppressed by the positively charged water mist.     

油气浓度对半开口管道爆炸超压特性与火焰行为的影响

为了研究油气浓度对半开口管道爆炸超压特性与火焰行为的影响,建立半开口透明管道实验台架,采用5种不同初始油气浓度,进行了一系列油气爆炸对比实验。研究结果表明:油气浓度对油气爆炸超压峰值以及升压速率有显著影响,二者都呈现随浓度的增加先增大后减小的变化规律;油气浓度对火焰锋面传播速度有着显著影响,在当量浓度比下,火焰锋面的传播速度最大,并且火焰锋面的传播距离也最远;管道内的火焰行为可以分为4个阶段;油气浓度对火焰传播形态以及传播速度有明显的影响,对火焰传播形态的影响主要体现在破坏变形以及管道外爆炸阶段,随着浓度增加,爆炸半径先增大后减小,火焰传播速度呈现相同的变化规律。