A methodology to predict shock overpressure decay in a tunnel produced by a premixed methane/air explosion

A methodology for estimating the blast wave overpressure decay in air produced by a gas explosion in a closed-ended tunnel is proposed based on numerical simulations. The influence of the tunnel wall roughness is taken into account in studying a methane/air mixture explosion and the subsequent propagation of the resulting shock wave in air. The pressure time-history is obtained at different axial locations in the tunnel outside the methane/air mixture. If the shock overpressure at two, or more locations, is known, the value at other locations can be determined according to a simple power law. The study demonstrates the accuracy of the proposed methodology to estimate the overpressure change with distance for shock waves in air produced by methane/air mixture explosions. The methodology is applied to experimental data in order to validate the approach.     

Estimation of pressure distribution for shock wave through the bend of bend laneway

Propagation of the air shock wave caused by explosion via the bend of a bend laneway has obvious nonlinear characteristics, compared with its propagation in a straight laneway. These characteristics are important bases to analyze the accident of gas explosion in underground mines and to estimate the blast resistance of underground structures in mines. In this work, the rule of the shock wave propagation via the laneway bend and the pressure distribution are studied by means of the numerical simulation approach. Theoretical results show that attenuation of the peak overpressure with distance does not obey exponent law when the air shock wave goes through the laneway bend. At some locations within the bend zone, the overpressures are higher than ones around those locations, the front of original plane wave bends in the bend of the laneway and after passing through the bend, it gradually returns to the state of plane wave propagation. There is a span dependent on the cross section dimension of laneway and the bend angle and increasing with the bend angle, in which the peak overpressure of shock wave does not uniformly attenuate with distance. When the bend angle is equal to 135°, this span is about five times as long as the corresponding equivalent diameter of the laneway. Additionally, the impulse of air shock wave attenuates uniformly via the laneway bend. On the end section of the complicated pressure distribution area in the bend, it is 66.65–98.7% of that in the straight laneway at the same scaled distance.     

瓦斯爆炸在角联通风管网中的传播特性研究*

为研究真实通风工况下瓦斯爆炸冲击波在复杂管网内的超压演化规律及高温传播规律,采用数值模拟方法,研究角联通风管网模型中各个监测点在不同通风条件下对瓦斯爆炸冲击波超压及高温的影响规律,研究结果表明:瓦斯爆炸冲击波在角联管网传播过程中产生3个局部高压区域,高温气体主要在左、右通路内传播,斜角联分支内只受到微弱影响;管网入口风流的存在,使得爆炸初期冲击波超压经相同距离传播用时更短,峰值更大,破坏力更强;风流的存在使得管网内高温气体传播状态发生改变,斜角联分支与左通路尾部热量发生积聚,温度峰值更大。     

Experimental investigation on shock waves generated by pressurized gas release through a tube

An experimental investigation on the flow structures and the strength of shock waves generated by high-pressure gas release through a tube into air was conducted. The results demonstrated that a leading shock wave was generated in front of the compressed gas jet and the shock wave speed increased firstly, then decreased and finally kept constant with an increase of the propagation distance in the tube. The experimentally measured Mach numbers of shock waves were close to those calculated from the theory of ideal shock tube flow. After spouting out of the tube, the normal shock quickly developed into a hemispherical shape. The Mach disk was observed in the under-expanded jet. For high-pressure combustible gas release, the concept of theoretical critical pressure of ignition was introduced and several theoretical critical pressures of common gaseous fuels were obtained.     

Blast overpressures from medium scale BLEVE tests

The measured blast overpressures from recent tests involving boiling liquid expanding vapour explosions (BLEVE) has been studied. The blast data came from tests where 0.4 and 2 m³ ASME code propane tanks were exposed to torch and pool fires. In total almost 60 tanks were tested, and of these nearly 20 resulted in catastrophic failures and BLEVEs. Both single and two-step BLEVEs were observed in these tests. This paper presents an analysis of the blast overpressures created by these BLEVEs. In addition, the blast overpressures from a recent full scale fire test of a rail tank car is included in the analysis.The results suggest that the liquid energy content did not contribute to the shock overpressures in the near or far field. The liquid flashing and expansion does produce a local overpressure by dynamic pressure effects but it does not appear to produce a shock wave. The shock overpressures could be estimated from the vapour energy alone for all the tests considered. This was true for liquid temperatures at failure that were below, at and above the atmospheric superheat limit for propane. Data suggests that the two step type BLEVE produces the strongest overpressure. The authors give their ideas for this observation.The results shown here add some limited evidence to support previous researchers claims that the liquid flashing process is too slow to generate a shock. It suggests that liquid temperatures at or above the Tsl do not change this. The expansion of the flashing liquid contributes to other hazards such as projectiles, and close in dynamic pressure effects. Of course BLEVE releases in enclosed spaces such as tunnels or buildings have different hazards.     

Influence of laneway support spacing on methane/air explosion shock wave

A laneway support system provides an available way to solve problems related to ground movements in underground coal mines, but also poses another potential hazard. Once a methane/air explosion occurs in a laneway, inappropriate design parameters of the support system, especially the support spacing, likely have a negative influence on explosion disaster effects. The commercial software package AutoReaGas, a computational fluid dynamics code suitable for gas explosions, was used to carry out the numerical investigation for the methane/air explosion and blast process in a straight laneway with different support spacing. The validity of the numerical method was verified by the methane/air explosion experiment in a steel tube. Laneway supports can promote the development of turbulence and explosion, and also inhibit the propagation of flame and shock wave. For the design parameters in actual laneway projects, the fluid dynamic drag due to the laneway support plays a predominant role in a methane/air explosion. There is an uneven distribution of the peak overpressure on the same cross section in the laneway, and the largest overpressure is near the laneway walls. Different support spacing can cause obvious differences for the distributions of the shock wave overpressure and impulse. Under comparable conditions, the greater destructive effects of explosion shock wave are seen for the laneway support system with larger spacing. The results presented in this work provide a theoretical basis for the optimized design of the support system in coal laneways and the related safety assessments.     

Propagation and intensity of blast wave from hydrogen pipe rupture due to internal detonation

The coupled fluid-structure-rupture model was developed to study the propagation and intensity of blast wave from hydrogen pipe rupture due to internal detonation. The dynamic rupture of pipe and propagation of blast wave were well coupled together in every timestep during the simulation. The numerical model was validated with experiments in terms of both typical rupture profiles and blast overpressures. Results reveal that crack branching of pipe can dramatically increase the rupture opening rate which controls the intensity and shape of the resultant blast wave. Due to the process of crack initiation and extension, the blast wave out of the pipe first forms and then is strengthened by the subsequent compression waves. This makes the maximum peak overpressure appears at a certain standoff distance above the rupture. Despite consuming some percentages of energy, the dynamic rupture of pipe generally presents positive effects (up to 2–3 times) on the blast wave intensity along the jetting direction due to the convergence effect of rupture opening on the release of internal high-pressure gas. Finally, through defining normalized overpressure and impulse based on the same hydrogen detonation in open spaces, the quantitative influences of pipe rupture on the blast wave intensity in cases of different detonation pressures and standoff distances are clarified.     

汽车爆炸的超压分布规律实验研究

测试了不同药量和不同车型的爆炸超压值,对汽车爆炸的超压分布规律进行了实验研究.结果表明,小汽车内发生炸药爆炸时,车门侧压力明显大于车尾部方向的压力,车外的冲击波超压值要大于空气中炸药爆炸的结果,前者约为后者的1.0～2.2倍.即车体对冲击波约束作用要小于车内底盘的反射作用.计算得到了实验中冲击波超压对人员的杀伤半径和最小安全距离,对汽车爆炸案件具有一定指导作用.冲击波的反射不可忽视,货车下地面炸药爆炸表现出明显的冲击波反射作用,测得超压值大于空气中爆炸的超压值.     

煤与瓦斯突出冲击波及瓦斯气流所致伤害研究

为揭示煤与瓦斯突出过程中冲击波及瓦斯气流传播特性,针对这种突出做功随瓦斯压力、煤的普氏系数和煤的放散初速度变化的特征,运用气体动力学理论,建立冲击波超压、冲击瓦斯流速度与传播距离以及煤层瓦斯压力等参数的关系,计算不同超压下瓦斯气流传播伤害的范围。理论计算与现场测试结果表明,突出冲击波属惰性弱冲击波;波阵面上的超压传播伤害距离与突出时瓦斯膨胀的强度、巷道断面及巷道壁面的摩擦力和局部阻力等因素有关;冲击产生的高压瓦斯气流是造成巷道内大量人员窒息伤亡的主要诱因;突出能量瞬间释放没有补给,冲击波及瓦斯气流会在巷道阻力等因素作用下迅速衰减。     

城镇燃气管道泄漏爆炸的定量风险分析

介绍了城镇燃气管道泄漏爆炸冲击波超压的定量风险分析方法.简要介绍了城镇燃气管道,对城镇燃气管道泄漏的失效概率、泄漏源模型、爆炸冲击波超压模型、超压概率模型、个人风险和社会风险分别作了论述.     

开敞空间可燃气云爆炸冲击波超压及灾害动力响应研究评述

为了进一步梳理和分析开敞空间可燃云爆炸冲击波超压传播规律及灾害动力响应方面的各项研究成果,推进可燃气体爆炸安全防控,减少人员伤亡和经济损失。在分析现有研究的基础上,总结开敞空间可燃气云爆炸冲击波超压传播规律及灾害动力响应研究等方面存在的不足,提出开敞空间多元混合气体爆炸冲击波超压传播规律研究、多影响参数下可燃气云爆炸冲击波超压传播规律定量分析、基于可燃气云爆炸冲击波超压作用下的承载体动力响应等未来研究的关键技术问题。     

Hazard evaluation of hydrogen–air deflagration with flame propagation velocity measurement by image velocimetry using brightness subtraction

Deflagration phenomena in hydrogen–air mixtures initially filled in 1.4 m³ spherical latex balloons were measured using a high-speed digital video camera and pressure transducers. The image velocimetry using brightness subtraction was introduced to eliminate the background effects for obtaining accurate time evolution records of flame propagation velocity. The maximum flame propagation velocity of about 100 m/s was observed with maximum overpressure 15 kPa at 1 m from ignition point. According to the detailed flame propagation velocity records, there were long deceleration durations. The observed maximum overpressure was smaller than the overpressure estimated by the basis of the observed maximum flame propagation velocity and the pressure wave theories of spherical flames. A new blast curve plot of scaled overpressure vs. distance was tentatively proposed.     

挡气板对综合管廊燃气舱爆炸冲击波传播规律影响研究

为研究挡气板对综合管廊燃气舱爆炸冲击波传播影响规律,采用Fluent模拟软件,研究三维燃气舱模型中不同挡气板间距下燃气爆炸后超压变化规律,探究不同间距挡气板对抑制燃气舱内爆炸冲击波传播效果.结果表明:挡气板对燃气舱中部超压影响较小,对顶部超压变化影响较大,导致燃气舱顶部挡气板处超压峰值激增;当气体填充区长20 m,挡气...     

综合管廊燃气舱燃气爆炸冲击波传播特征研究*

为研究综合管廊燃气舱燃气爆炸冲击波的传播特征,采用数值模拟方法研究首次超压峰值和首次流速峰值的变化规律,建立首次流速峰值与首次超压峰值和填充长度的耦合关系,分析不同填充长度情况下燃气爆炸后的超压和水平流速的变化规律。结果表明:燃气爆炸后,燃气舱内存在多个超压峰值,峰值间存在明显的时间差。冲击波到达各测点的时间与燃气填充长度成反比关系。水平流速曲线随着时间的变化以0为基点上下振荡,存在正向峰值和反向峰值。随着燃气填充长度的增加,流速下降趋势变快。首次超压峰值随传播距离的增加先增大后减小再增大,随着填充长度的增加,产生超压峰值最大值的位置由接近填充长度结束的位置转移到燃气舱封闭端。首次流速峰值随传播距离的增加先增大后减小。首次流速峰值与首次超压峰值呈现正比关系,通过拟合得到流速峰值与超压峰值及填充长度的耦合关系。研究结果可为燃气舱燃气爆炸后的流速分布研究以及燃气舱防火分区的设计提供参考。     

Numerical simulation of blast wave oscillation effects on a premixed methane/air explosion in closed-end ducts

This paper investigated the effects of blast wave oscillation on the overpressure of premixed methane/air explosions by numerical simulations and experiments. The AutoReaGas 3D code and a duct were used in the study. The oscillation induced by the repeat reflection of a blast wave in a closed-end duct was observed by high-speed camera. There was an oscillation zone in the blast wave which exhibited some saw-toothed characteristics. This explained why the overpressure in closed-end ducts was higher than that in open-end ducts. In addition, some of the peak overpressure was even higher than the C–J pressure of 1.76 MPa. The peak overpressures at the ducts' ends were higher than at other measurement points for 5 m, 10 m, and 15 m long ducts. This was mainly due to the reflection of the blast wave. The oscillating period increased with increasing duct length, and could be calculated by t = 0.0003 + 0.00198 L. However, the duct's diameter had no significant influence on the oscillation's period. The amplitude increased with increases in the duct length, except for the case of a 20 m long duct, and increased with decreases in the ducts' diameter. In addition, the peak overpressures in ducts of the same length/diameter ratio were similar. The peak overpressure increased with the increase of the length/diameter ratio, and the maximum value of the peak overpressure in the ducts had the same trend. However, the overpressure did not increase when the length/diameter ratio reached 250.     

爆炸冲击波及高温耦合引起瓦斯二次爆炸特性研究

在煤矿安全事故中,破坏程度最严重的事故之一就是瓦斯爆炸,而瓦斯爆炸冲击波及火焰锋面可能会二次点爆其他位置积聚瓦斯,加速火焰锋面及冲击波传播,并能产生更高的超压,造成更大的人员伤亡及财产损失。借助详细反应机理GRI Mech 3.0,基于开源化学动力学软件Cantera,研究冲击波强度、瓦斯体积分数和冲击波及高温耦合条件下对瓦斯爆炸特性的影响。结果显示,冲击波诱导瓦斯爆炸中,点火延迟时间随着瓦斯体积分数的增大而出现增大现象,随冲击波强度的增大而降低;同时分析了二氧化碳、一氧化碳和一氧化氮致害物质的浓度随瓦斯体积分数、冲击波强度和冲击波及高温耦合条件下的变化情况。     

Numerical simulations on the attenuation effect of a barrier material on a blast wave

This paper numerically modeled previous experimental results and quantitatively revealed the attenuation effect of a barrier material on a blast wave. Four fluids were considered in the present study: the detonation products, water, foamed polystyrene, and air. These fluids were modeled by Jones-Wilkins-Lee (JWL), stiffened gas, and ideal gas equations of state. A mixture of water and foamed polystyrene was used as a barrier to encircle a 0.1 kg mass of spherical pentolite, and the interface problem between the barrier and the blast wave was investigated. The simulation parameters were the radius and the water volume fraction of the barrier. To elucidate the effect of the barrier, we conducted two series of numerical simulations; one without a barrier, and another with a barrier of 50 or 100 mm in outer radius and 0–1 in the water volume fraction. Peak overpressure, positive impulse, and pressure history all agreed well with the previous experimental results. We focused on the energy transfer from high-pressure detonation products to other fluids. The sum of the kinetic energies of the detonation products and the barrier induced by the blast wave could quantitatively estimate the attenuation effect of the blast wave and was minimized when the water volume fraction was 0.5, as was the case in the previous experiment.     

泡沫镍对甲烷-空气预混气体爆燃超压影响的研究

为了有效抑制气体爆炸时产生的冲击波强度,设计加工了内部截面为110 mm×80 mm,长500 mm的爆炸实验管道,利用高频动态压力传感器,对比研究了泡沫镍在管道内的安放位置对甲烷-空气预混气体爆炸的影响。结果表明:当把泡沫镍铺设在管道中间位置时其对爆炸超压的抑制效果最好,其次是放置在管道的尾部,效果最差的是将多孔材料放置在管道的前部。     

Numerical study of dynamic response and failure analysis of spherical storage tanks under external blast loading

The performance of energy infrastructures under extreme loading conditions, especially for blast and impact conditions, is of great importance despite the low probability for such events to occur. Due to catastrophic consequences of structural failure, it is crucial to improve the resistance of energy infrastructures against the impact of blasts. A TNT equivalent method is used to simulate a petroleum gas vapor cloud explosion when analyzing the dynamic responses of a spherical tank under external blast loads. The pressure distribution on the surface of a 1000 m³ spherical storage tank is investigated. The dynamic responses of the tank, such as the distribution of effective stress, structural displacement, failure mode and energy distribution under the blast loads are studied and the simulation results reveal that the reflected pressure on the spherical tank decreases gradually from the equator to the poles of the sphere. However, the effects of the shock wave reflection are not so evident on the pillars. The structural damage of the tank subjected to blast loads included partial pillar failure from bending deformation and significant stress concentration, which can be observed in the joint between the pillar and the bottom of the spherical shell. The main reason for the remarkable deformation and structural damage is because of the initial internal energy that the tank obtained from the blast shock wave. The liquid in the tank absorbs the energy of impact loads and reduces the response at the initial stage of damage after the impact of the blast.     

液体火箭共底破裂爆炸安全设防距离

针对航天发射场一旦发生低温推进剂泄漏而导致火箭爆炸,会对人员和财产造成重大损失的问题,采用TNT当量模型和TNO(The Netherlands Organization)多能模型计算不同摩尔百分比的氢氧推进剂混合反应时产生爆炸冲击波的危害性,并模拟爆炸冲击波造成的事故影响范围,然后对两种模型的仿真结果加以对比分析,根据最不利原则选取出最终需要的结果,最后划分出安全设防距离。由仿真结果可知,不同的氢氧混合摩尔百分比造成的爆炸后果不同,同时TNT当量模型在爆炸近场处高估了爆炸超压值,在爆炸远场处低估了爆炸超压值,而TNO多能模型在理论上有效地对这一缺陷进行了弥补。对航天发射场的安全布局起到了一定的参考价值。