公共建筑结构内爆炸效应的数值模拟

大型公共建筑结构内的爆炸问题分为4个连续阶段,即炸药的爆轰、冲击波的传播、冲击波与结构壁面的反射、结构壁面在爆炸载荷作用下的动力响应。为研究大型公共建筑结构内爆炸的效应,以爆轰动力学、爆炸力学、结构动力学和爆炸力学计算方法等多个领域的理论知识为基础,选取典型长方体空间为研究对象,采用有限元计算方法,对长方体密闭空间内冲击波传播规律及壁面爆炸载荷分布特性进行了数值模拟。结果表明:在爆炸冲击波距离结构壁面较远时,计算模型中的冲击波衰减规律与无限大气中的相似,可以采用空爆理论计算模型;而在结构壁面处,由于受到反射冲击波的影响,当反射波与入射波叠加后在某些观察点会出现压力急剧升高,甚至压力超过首个峰值的现象;在结构壁面的角域,由于冲击波衰减缓慢,超压作用时间较长,破坏效果也最大。     

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。     

不同曲率弯曲巷道爆炸冲击波传播特性数值模拟研究

为研究爆炸冲击波在不同曲率弯曲巷道内的传播规律,采用数值模拟手段建立了不同曲率弯曲巷道爆炸模型,分析了爆炸冲击波在巷道内的传播特性及其变化规律, 并结合冲击波超压对人体的伤害程度分类,研究了不同曲率弯曲巷道内爆炸破坏效应分区。模拟结果表明,弯曲角度改变了巷道内冲击波超压分布,随着巷道弯曲角度的不断增大,壁面反射对冲击波超压峰值分布起主要作用,随着传播距离的增加,冲击波超压峰值衰减显著,体现了超压峰值变化的距离效应。此外,巷道弯曲角度的增加整体减小了爆炸损伤严重程度。研究结果可实现对不同曲率弯曲巷道内冲击波超压分布的预测,并为巷道内爆炸事故预防及应急救援提供借鉴。     

不同类型管道内瓦斯爆炸冲击波传播试验研究

为探究不同类型管道内瓦斯爆炸冲击波传播规律,利用L型、T型和十字型试验管道模拟井下巷道结构,采用瓦斯燃烧爆炸测试系统进行瓦斯爆炸模拟试验,监测管道内不同位置的压力值,研究不同类型管道内瓦斯爆炸冲击波在转弯和分岔结构前后的压力变化规律。试验发现:L型管道转弯处外侧管壁爆炸冲击波压力峰值最高;T型和十字型管道的分岔结构可以降低L型管道转弯处的压力峰值,且T型分岔结构的降低效果更好;L型、T型和十字型管道对冲击波压力的衰减效果依次增强。     

煤矿长壁工作面瓦斯爆炸全尺寸模拟

为丰富煤矿事故调查内容和有效应用矿井阻隔爆技术,利用气体爆炸数值模拟软件FLACS建立原型尺度的采煤工作面巷道模型进行数值模拟,并结合事故调查资料,研究瓦斯爆炸火焰、冲击波超压和动压在直巷、转角、分叉等巷道结构中的传播规律和破坏特征。结果显示:巷道分叉提供的自由空间可显著限制爆炸火焰传播;巷道分叉及转角能有效降低冲击波超压;冲击波动压气流速度衰减在巷道分叉处较为明显,但对直巷和转角不敏感;携残片和毒烟的动压高速气流是灾区远场的主要致灾因子。定量的数值仿真结果对认识矿井原型尺度下瓦斯爆炸传播规律、再现事故场景、优化阻隔爆设施布置有一定借鉴意义。     

不同曲率弯曲巷道弯角近区爆炸冲击波传播特性研究

为研究爆炸冲击波在不同曲率弯曲巷道弯角近区的传播规律,采用有限元方法建立爆炸模型,分析爆炸冲击波传播特性及其变化过程。研究结果表明,弯曲角度改变了巷道内冲击波超压分布,巷道内爆炸冲击波是巷道壁面反射叠加增强作用与传播距离衰减效应综合作用的结果,在爆源近区反射叠加作用占主导地位,使峰值压力出现极值;随着传播距离的增加,冲击波衰减占主导地位,峰值超压随距离呈现为线性衰减。     

障碍物对瓦斯爆炸冲击波影响研究

为研究障碍物对瓦斯爆炸冲击波传播规律的影响,利用水平管道式气体——粉尘爆炸实验装置,测试并分析障碍物数量、尺寸和壁面粗糙程度对瓦斯爆炸冲击波超压、冲击波传播规律的影响。结果表明:障碍物对瓦斯爆炸过程中冲击波传播规律具有重要影响。障碍物存在时,改变了爆炸冲击波的传播规律,提高了冲击波超压的最大峰值压力,且随着障碍物数量和尺寸的增加,这种激励作用越明显。随着壁面粗糙程度的增大,瓦斯爆炸冲击波超压明显增大。研究结果对井下巷道瓦斯爆炸冲击波的防治具有一定的指导意义。     

爆炸空气冲击波在巷道转弯处的传播特性

为了探索爆炸空气冲击波在巷道内的传播规律,进行了数值计算和理论分析,讨论了爆炸冲击波通过45°弯曲巷道后的压力变化过程.研究结果表明: 爆炸空气冲击波通过45°弯曲巷道后的压力分布复杂,空气冲击波逐渐恢复为平面波需经过4倍等效巷道直径的距离传播.在该4倍等效距离内,冲击波反射叠加,在巷道外侧壁面Mach反射点取得超压最大值,恢复平面波以后超压随距离呈单调衰减.     

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。     

缝洞型管道瓦斯爆炸特性数值模拟研究

为探究采空区遗煤、松散破碎岩块对瓦斯爆炸的影响，建立缝洞型管道模型，采用数值模拟与理论分析结合方法研究采空区内缝洞型管道内瓦斯爆炸的传播规律及管道长径比对瓦斯爆炸过程中速度与冲击波的影响。研究结果表明:在缝洞型结构内，随着火焰沿管道向前传播，各监测点速度逐渐变大、压力先增加后降低，而压力上升速率则表现出不规则的变化；缝洞结构加剧了火焰燃烧的剧烈程度，提高了管道内各监测点的温度峰值；在缝洞型管道内随长径比r增加，各监测点最大压力峰值以及速度大小依次降低。     

Blast phenomena in urban tunnel systems

Traffic infrastructure in urbanised areas is increasingly projected in tunnels underground or covered over, these days. A consequence is that in case of an incident with hazardous materials the safety level for fellow road users in tunnels is considerably less than it is in surface infrastructure. To reduce the consequences of incidents for fellow tunnel users, urban tunnels are sometimes interrupted by open spaces of limited length. Open spaces allow, for instance, the release of smoke in case of a fire. In this way, possible lethal effects are limited to the tunnel section in which the incident occurred. To what extent an open space may also be effective in the mitigation of blast effects from an explosion in a tunnel system is subject of this paper.

To this end, the blast effects originating from the rupture of a 50 m³ LPG pressure vessel in an urban tunnel system have been computed by numerical simulation. The results show that an open space in a tunnel system has a significant mitigating effect on the blast effects indeed. However, as a consequence of the ingress of a high-velocity jet flow that follows on a primary blast wave, a second blast wave develops in the tunnel section following on an open space. The strength of this second blast wave is not very dependent on the length of the open space. It shows that an open space in a tunnel system may not always limit the lethal effects of explosion incidents in tunnels to the tube in which the incident occurred. The second blast wave in the tunnel section following on an open space may have lethal consequences for fellow tunnel users by car window failure.     

Effect of scale on the explosion of methane in air and its shockwave

Explosion experiments using premixed gas in a duct have become a significant method of investigating methane-air explosions in underground coal mines. The duct sizes are far less than that of an actual mine gallery. Whether the experimental results in a duct are applicable to analyze a methane-air explosion in a practical mine gallery needed to be investigated. This issue involves the effects of scale on a gas explosion and its shockwave in a constrained space. The commercial software package AutoReaGas, a finite element computational fluid dynamics (CFD) code suitable for gas explosions and blast problems, was used to carry out the numerical simulation for the explosion processes of a methane-air mixture in the gallery (or duct) at various scales. Based on the numerical simulation and its analysis, the effect of scale on the degree of correlation with the real situation was studied for a methane-air explosion and its shockwave in a square section gallery (or duct). This study shows that the explosion process of the methane-air mixture relates to the scales of the gallery or duct. The effect of scale decreases gradually with the distance from the space containing the methane-air mixture and the air shock wave propagation conforms approximately to the geometric similarity law in the far field where the scaled distance (ratio of the propagation distance and the height (or width) of the gallery section) is over 80.     

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.     

A numerical study of the evolution of the blast wave shape in rectangular tunnels

When the explosion of condensed materials occurs in square or circular cross-section tunnel, the subsequent blast wave reveals two patterns: three-dimensional close to the explosive charge and one-dimensional far from the explosion. Pressure decays for these two patterns have been thoroughly studied. However, when the explosion occurs in rectangular cross-section tunnel, which is the most regular geometry for underground networks, the blast wave exhibits a third, two-dimensional, patterns. In order to assess the range of these three patterns, several numerical simulation of blast waves were carried out varying the width and the height of the rectangular cross-section as well as the mass of the charge. Laws are presented to localize the transition zones between the 3D and the 2D patterns, and between the 2D and the 1D patterns, as functions of non-dimensional width and height. The numerical results of the overpressure are compared to existing 3D and 1D laws. An overpressure decay law is proposed to represent the 2D pattern. Knowing the two transition zones and the overpressure decays within these zones, an algorithm is presented to efficiently predict an overpressure map. This algorithm is validated by comparison with experimental data.     

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.     

基于超压值地铁上覆管道爆炸对隧道及人员安全影响研究*

为分析地铁上覆管道爆炸对乘客安全影响,采用基于超压冲击波阀值数值模拟,通过将泄漏气体能量等效为TNT当量,分析不同泄漏模式爆炸冲击波对地铁隧道及人员安全影响。结果表明:爆炸产生的超压冲击波对隧道及人员影响小于限值,不会造成人员伤亡,研究结果可为地下工程下穿油气管线安全影响分析提供理论支撑。     

Coupling effects of foam ceramics on the flame and shock wave of gas explosion

The coupling of gas explosion flame and shock wave is analyzed. In the gas explosion process, shock wave is affected by the flame directly, and shock wave also induces the flame. Inhibiting explosion can be achieved by the interference between the flame and shock wave propagation. If the coupling effects can be damaged, the adverse effects caused by the explosion should be mitigated and controlled. According to the structure characteristics of foam ceramics, the coupling effects mechanism of ceramic foam on gas explosion flame and shock wave is researched. When the explosion goes through the structure of foam ceramics, the flame can be quenched and the shock wave be attenuated. After the flame is quenched, the supply of precursor shock wave energy is cut off. Due to lack of energy supply, the destructive effects of blast wave will be reduced effectively. Coupling effects of the flame and shock wave can be damaged by the special structure of foam ceramics. Studies suggest that a certain function to represent the structure characteristics of foam ceramics must exist. For a certain material of foam ceramics, the sure porosity δ and the pore diameter d also can be get, which is the key to research and develop foam ceramic suppression technology of gas explosion.     

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。     

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.     

Computer-aided modeling of the protective effect of explosion relief vents in tunnel structures

This paper aims at contributing to the efficient design of explosion protection systems against confined explosions. The issue addressed concerns the quantitative estimation of the protective effect of explosion relief vents in the case of confined explosions inside tunnels. A series of virtual experiments performed by computer simulation, revealed how the number of vents, their diameter, as well as the angle between the vents and the tunnel, influences the blast wave attenuation. The computational study was performed considering a complicated large-scale tunnel configuration with branches on its half portion. The purpose was the calculation of the attenuation effect due to the presence of vents by comparing the total explosion-specific impulse developing at antidiametric positions inside the tunnel. Simulations were carried out via a three-dimensional numerical model built in the computational fluid dynamics code CFX 5.7.1, which has been validated in previous papers against experimental overpressure histories data demonstrating reasonable performance. Computer results showed that the use of branch vents provides an effective method for shock wave attenuation following an explosion, whereas their statistical elaboration revealed that the attenuation is mainly affected by the number of vents and their diameter. In contrast, the angle between the side vents and the main tunnel appeared to slightly affect the pressure wave weakening. Eventually, the quantitative influence of the above parameters was effectively illustrated in functional diagrams, so that the total attenuation effect may be promptly estimated, if the design variables are known. In addition, two statistical models with reasonable fitting to the calculated data are proposed, which express the attenuation effect as a dependent variable of the design variables including their interactions.