Numerical investigation of surface conduit parallel gas pipeline explosive based on the TNT equivalent weight method

With the rapid development of petroleum industry, the transport pipelines of oil and gas are increasingly constructed to minimize land use conflicts. Therefore, the parallel pipelines are unavoidable in order to save land resource, reduce the pipeline construction and maintenance costs. The economy and security of pipeline laying and running is the primary problem considered in pipeline construction, which the parallel spacing plays a decisive role to. The leakage of natural gas is very serious and dangerous due to its flammable and combustible. The explosive of leak gas causes impact failure to parallel pipeline. Specific to the surface conduit parallel gas pipeline, numerical simulation of leak natural gas explosive was carried out based on TNT equivalent weight method. Explosive damage degree of pipeline decreased with the pipeline distance increasing. Consulting with the pipeline ovalization strain design criteria and the combustion effect, the safety parallel natural gas pipeline space maybe at least 4 m to ensure the surface conduit parallel pipeline safely and steadily operation.     

爆炸冲击波作用下靶板的塑性大变形响应研究

对四边约束方形靶板 ,在爆炸冲击波作用下的塑性大变形响应情况 ,进行了理论分析与试验研究。运用能量守恒的方法 ,同时考虑试验过程中靶板的边界约束条件 ,得到了四边约束方形靶板在爆炸冲击波作用下发生塑性大变形时挠度的半经验公式。理论计算与试验结果吻合性较好 ,这种方法可应用于板结构在爆炸冲击波作用下的毁伤或防护方面的工程预测     

Response of the buried steel pipeline caused by perilous rock impact: Parametric study

One of threatening buried steel pipeline in bad geological regions is collapsed rock. Buckling behavior of a buried pipeline impacted by a perilous rock with spherical shape was investigated by numerical simulation. Effects of pipeline parameters (internal pressure, wall thickness, diameter, buried depth) and perilous rock parameters (impact velocity, radius, eccentric distance) on deformation, stress and strain of the buried pipeline were discussed. Buckling behaviors of the buried pipeline under transverse and longitudinal inclined impacts also were studied. The results show that cross section shape of the buried pipeline becomes to an oval, then to a peach shape, and finally to a crescent shape or gourd shape in the process of rock’s impact. The deformation process of a buried pipeline can be divided into four stages. They are elastic deformation stage, buckling stage, elastic recovery stage and final deformation stage. Buckling mode of no-pressure pipeline is more serious than the pressure pipeline. The impact dent’s length and depth increase with the decreasing of buried depth, wall thickness and internal pressure. But they increase with the increasing of impact velocity, perilous rock’s radius and pipeline’s diameter. The maximum stress and plastic strain decrease with the increasing of buried depth and wall thickness. Under rock’s eccentric impact, impact dent trends to one side. Stress and plastic deformation decrease with the eccentric distance increases. Under rock’s transverse and longitudinal inclined impacts, cross section shape of the buried pipeline is an oval shape when the incidence angle α ≤ 45°, and there is no plastic deformation. When α > 45°, impact dent appears. Buckling is more serious with the incidence angle increases. Destructive powers of transverse and longitudinal inclined impacts are smaller than the vertical impact.     

An overpressure-time history model of methane-air explosion in tunnel-shape space

This study investigated methane-air explosion in tunnel-shape space and developed an overpressure-time history model based on numerical results. The findings revealed that for the progressively vented gas explosion with movable steel obstacles in a 20 m long tunnel, the inner peak overpressure increased as the activation pressure of the tunnel top cover got higher but remained below 6 bar. However, as the activation pressure increased to 8 bar or higher, the peak inner overpressure remained unchanged. As the segment cover panel became wider, the peak pressure was almost unchanged, but the pressure duration and impulse declined significantly. The peak pressure and impulse increased as the tunnel length vary from 10 to 30 m. With fixed tunnel length, higher blast pressure but lower impulse was observed as the inner obstacles were closer or the activation pressure of obstacles was higher. It is also found that a local enlarged space in the tunnel enhanced the peak pressure significantly. An overpressure time history model for the tunnel with fixed top cover and enlarged end zone was established. The model considered activation pressure of vent cover, area and length of vent opening, methane concentration, number and blockage ratio of fixed obstacles was developed to calculate the overpressure and corresponding time at characteristic points of the pressure-history curve. The cubic Hermite interpolation algorithm and a specially tuned formula consisting of the power and exponential function were used to interpolate pressure values between characteristic points. The proposed model can predict both the peak pressure and the overpressure time history with acceptable accuracy.     

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.     

Small-scale physical explosions in shock tubes in comparison with condensed high explosive detonations

A series of small-scale experiments involving physical explosions in a 1.6 l pressure vessel was carried out. Explosions were initiated by spontaneous rupture of an aluminium membrane on one side of the vessel at a pressure in the range 1–1.2 MPa. The pressure waves released were measured at different distances along two separate shock tubes, one 10 m long and 200 mm in diameter (closed at one end by the high pressure vessel) and the other 15 m long and 100 mm in diameter.TNT equivalency was used for predicting the blast wave characteristics after vessel rupture. TNT equivalency was used because equations for prediction of peak pressure and impulse of the blast wave in 1-D geometry after detonations of condensed explosives are known. Some experiments with an equivalent amount of real explosive were carried out for comparison with the theoretical and experimental data obtained. The applicability of the TNT equivalency method presented for calculations of maximum pressure and shock wave impulse generated after rupture of the pressure vessel in 1-D geometry is discussed.     

沉箱码头聚脲涂层抗爆防护毁伤效应数值模拟

为探究爆炸荷载作用下聚脲涂层对沉箱码头的保护作用,采用LS-DANA非线性动力分析平台,模拟在1 kg TNT当量炸药水中非接触爆炸时,不同涂覆厚度聚脲涂层的沉箱码头毁伤破坏特征.结果表明:无聚脲防护的沉箱码头毁伤破坏程度明显大于涂覆聚脲防护的沉箱码头,沉箱码头的毁伤主要集中在迎爆面外墙和迎爆侧上部管沟,随着聚脲涂层厚...     

套管损伤磁记忆检测信号定量研究

在油气生产过程中,井下套管损伤会造成井况恶化,致使正常井转变为套损井。为了防止套损井的出现和安全事故的发生,有必要对套管进行早期损伤检测。采用金属磁记忆检测技术,开展了实验研究。实验中,通过对套管内壁环切,将套管壁厚设计为等值递增和不等值递增两种形式;根据实验数据,对磁记忆检测信号梯度值、信号梯度波峰值及信号梯度峰宽值等特征参量与壁厚、壁厚变化量的定量关系进行拟合。结果表明:磁记忆检测信号梯度值、信号梯度波峰值及信号梯度峰宽值等特征参量,可以很好的表征套管壁厚的变化情况;信号梯度值与套管壁厚呈线性递增关系;信号梯度波峰值和信号梯度峰宽值均与套管壁厚变化量呈线性递增关系。该试验结果有助于完善磁记忆检测技术的定量化研究和利用磁记忆原理检测套管损伤的评价体系。     

Effect of rusting and mechanical damage of gap surfaces on efficiency of flame gaps in flameproof electrical apparatus

Potentially incendiary electrical apparatus for use in the presence of explosive gas atmospheres have to be specially designed to prevent the apparatus from igniting the gas. Flameproof design is one of several options, and one requirement is then that any holes and gaps in the enclosure wall be designed to prevent a gas explosion inside the enclosure from being transmitted to an explosive gas cloud outside it. Current standards (IEC) require that flame gap surfaces have a surface roughness of <6.3 μm. Any damaged flame gap surface has to be restored to this quality. The present investigation has demonstrated that flame gap surfaces in flameproof electrical apparatuses can suffer considerable corrosive and mechanical damage without any reduction of gap performance. In some cases very significant mechanical surface damage in fact improves gap performance. Possible physical reasons for this are discussed. These findings indicate that current high costs of repairing and replacing flameproof electrical apparatus in process plants offshore and onshore can be significantly reduced without any increase of explosion risks.     

抛光铝粉爆炸及ABC粉体抑爆特性的实验研究

为研究抛光铝粉的爆炸危险和ABC粉体的抑爆特性,在对实验粉体粒径分布进行分析的基础上,采用20 L粉尘爆炸特性实验装置,分别对不同铝粉尘浓度、不同抑爆剂浓度条件下的爆炸特性参数进行测试。研究结果表明:在实验条件下,铝粉的爆炸下限为45 g/m3＜C＜60 g/m3;随铝粉浓度增加,爆炸烈度呈现出先增强后减弱的变化趋势,在浓度为400 g/m3时爆炸烈度最大。ABC抑爆剂能够有效抑制铝粉爆炸超压和爆炸反应进程,随着惰性粉体浓度的增加,抑制效果愈加明显,爆炸逐渐减弱。当ABC惰性粉体的质量占比增加到50%时,相较单一铝粉爆炸,反应过程时间由72 ms增加至785 ms,爆炸最大压力、最大压力上升速率分别下降了61.7%,89.5%;当ABC粉体质量占比为53%时,铝粉被完全惰化,未发生爆炸。     

多因素下开洞口煤仓风致积雪CFD模拟及拟合研究

为解决结构设计时开洞口圆形煤仓表面无法确定荷载分布系数问题,使用计算流体力学软件研究了开洞口煤仓不同跨度下风向角、积雪厚度及矢跨比变化下屋面积雪不均匀分布情况,提出了针对此种特殊结构的屋面积雪值拟合公式。研究结果表明:此公式拟合准确度高,屋面积雪值随风向角和积雪厚度增大而变大,风向角对积雪值影响极大,矢跨比影响下屋面积雪值变化较为复杂,且风向角和矢跨比2种参数相互影响,不应单一考虑矢跨比对球壳屋面积雪值的影响。     

The shaped blasting experimental study on damage and crack evolution of high stress coal seam

In the deep high stress coal and rock mass, the efficiency of the ordinary blasting method is constantly affected by the high pressure. This study investigates the shaped blasting technology with increased blasting efficiency, develops a mechanical model for coal crack expansion during shaped blasting, and examines the force-energy action of energy-gathering jets during coal splitting. The established model was combined with experiments and simulations to reveal the damage and evolution of cracks in coal and rock masses. Experiments demonstrate that shaped blasting can create an energy-gathering jet that causes a directional fracture in the test block. The peak of compressive strain in the energy-gathering direction is 1.12 times greater than that of ordinary blasting, and the static action period of the explosive gas is prolonged by 1.3 μs according to the stress curve. Moreover, the peak pressure strain increased 3.2 times, and the pull strain peak increased 3.92 times. The damage amount was represented by the resistivity and ultrasonic wave speed, and shaped blasting causes 1.2 and 1.5 times greater damage than ordinary blasting. The research results provide technical methods for safe and rapid penetration blasting in deep high-ground stressed coal mines.     

壳体厚度对传爆药慢速烤燃响应的研究

针对传爆药在制造、存贮、运输及实战环境中可能会遭受意外的热刺激,本文通过壳体厚度对传爆药慢速烤燃响应特性的影响的实验研究,来检测弹药对意外刺激的敏感程度和发生反应时的剧烈程度,并对实验结果进行了分析。实验以钝化RDX为主装药,以45#钢为壳体,利用自行设计的慢速烤燃试验系统对其进行试验。结果表明：在相同装药条件下,随着壳体厚度的增加,单位时间内传热量减少,体系升温速率减慢,炸药的烤燃时间随之增加,热爆炸延滞期增长;同时,随着壳体厚度的增加传爆药发生慢速烤燃反应的温度升高,热敏感程度降低,热安定性也随之提高。另外,在相同装药条件下,壳体厚度对慢速烤燃响应的剧烈性也有很大得影响。烤燃反应的剧烈程度随着壳体厚度的增大而减小。     

Numerical investigation and analysis of indoor gas explosion: A case study of “6·13” major gas explosion accident in Hubei Province,China

Taking the ' 6·13 ′ major gas explosion accident in Shiyan, Hubei Province, China as an example, three problems were studied in this work: (1)The determination of the volume of natural gas involved in the explosion; (2)The propagation process of shock wave inside the building and the damage evolution process of the accident-related building; (3)The overpressure and fragment injury to the person outside the building. Through the numerical simulation in ANSYS/LS-DYNA software, the volume of natural gas involved in the explosion is determined to be 10240 × 1400 × 400 cm (length × width × height) from three perspectives: the damage to the building, the distribution of overpressure inside the building, and the TNT equivalent of the explosion energy. The simulation results are in good line with the accident, which verifies the effectiveness of the scheme and the accuracy of the numerical model. Based on the reasonable filling scheme, the propagation process of shock waves inside the building, the damage evolution process of the building, and the injury ranges of overpressure and fragments outside the building are analyzed. It can be found that the propagation of shock waves in confined space is complex and variable. The explosion shock waves are first reflected and superimposed in the watercourse, resulting in pressure rise. At about 8ms, the shock waves rushed into the first-floor space of the building, and the maximum overpressure was about 0.56 MPa. At about 50 ms, the shock waves rushed into the second-floor space, and the maximum overpressure was about 0.139 MPa. The first and second-floor slabs and infilled walls were almost completely destroyed. The interior walls of the infilled walls are mainly collapsed, and the exterior walls are ejection around the building as the center. The peak displacement and peak velocity of the interior walls of each floor are about 15% of the exterior walls. The fragments which cause fragment injury mainly come from the retaining wall above the watercourse, the maximum velocity is about 89 m/s, and the maximum displacement is 8.9 m. The safety distance of fragment injury is about 8.8 m, while the safety distance of overpressure injury is about 4.6 m. The lethal distance of fragment injury is greater than that of overpressure injury. Compared with the distance between different damage levels of overpressure injury, the difference in fragment injury is small. Therefore, the safety assessment at the engineering level only needs to consider the safety distance of fragment injury. This study can provide suggestions for evaluating the damage of natural gas cloud explosions in confined spaces and is helpful for accident investigation and safety protection.     

管道内天然气爆炸火焰及压力波传播规律实验研究

天燃气安全不仅仅局限在企业内部,而是面向全社会,关系到社会稳定和市民生命财产安全。随着天然气市场开拓和广泛利用,庞大的管网系统和多样的用气环境给安全工作提出了更高的要求。采用理论分析、实验研究相结合的方法研究了管道内天然气爆炸火焰及压力波的传播规律。应用直径为700mm,长度为93m的管道进行了三次天然气爆炸传播实验。得出爆源点最大压力值并不是整个爆炸过程的最大值;压力波最大压力值在爆源点附近先降低,然后上升到某一峰值之后再逐渐衰减;最大压力值在衰减过程中不是单调衰减,有点起伏;随着天然气浓度的增大,其爆炸平均升压速率反而减小;随着天然气浓度的增大,其爆炸平均升压速率反而在减小;爆源附近火焰传播速度较小,上升到某一峰值后逐渐衰减。     

圆拱形缺陷对砂岩力学特征影响的试验研究

为研究含圆拱形预制缺陷砂岩的力学特征,在板状黄砂岩试样内预制了不同α值的圆拱形缺陷。采用YNS-2000型电液伺服控制试验系统和数字照相采集系统研究了不同圆拱形缺陷倾角α对黄砂岩力学特征和破坏模式的影响规律。研究结果表明:试样峰值强度、平均模量和割线模量随着α的增大呈先减小后增大再减小趋势,α=30°试样峰值强度和峰值应变均最小,α=75°试样峰值强度和应变均达到最大;预制圆拱形缺陷α对试样起裂应力、起裂位置和破坏模式均具有重要影响,随着α值的增大,试样起裂应力总体呈先减小后增大再减小趋势,当α=30°时,试样的平均起裂应力最小,其值为10.90 MPa;当α=75°时,试样的平均起裂应力最大,其值为18.91 MPa。     

The effect of orifice plates with different shapes on explosion propagation of premixed methane–air in a semi-confined pipeline

The effect of internal shape of obstacles on the deflagration of premixed methane–air (concentration of 10%) was experimentally investigated in a semi-confined steel pipeline (with a square cross section size of 80 mm × 80 mm and 4 m long). The obstacles used in this study were circular, square, triangular and gear-shaped (4-teeth, 6-teeth and 8-teeth) orifice plates with a blockage ratio of 75%, and the perimeter of the orifice was regarded as a criterion for determining the sharpness of the orifice plate. The overpressure history, flame intensity histories, flame front propagation speed, maximum flame intensity and peak explosion overpressure were analyzed. The explosion in the pipeline can be divided into two stages: initial explosion and secondary explosion. The secondary explosion is caused by recoiled flame. The perimeter is positively related to the intensity of the recoiled flame and the ability of orifice plate to suppress the explosion propagation. In addition, the increase in the perimeter will cause the acceleration of the flame passing through the orifice plate, while after the perimeter of the orifice reaches a certain value, the effect of the increase in perimeter on explosion excitation becomes no obvious. The overpressure (static pressure) downstream of the orifice plate is the result of the combined effect of explosion intensity and turbulence. The increase in perimeter leads to the increase in turbulence downstream of the orifice plate which in turn causes more explosion pressure to be converted into dynamic pressure.     

Experimental study on methane explosion characteristics with different types of porous media

Porous media has a significant effect on flame and overpressure of methane explosion. In this paper, the pore diameter and thickness of porous media are studied. Nine experimental combinations of different pore diameter and thickness on the propagation of flame and overpressure of methane explosion in a tube are analyzed. The results show that the porous media not only can suppress the explosive flame propagation, but the porous media with large pore diameter can cause deflagration and accelerate the transition of flame from laminar to turbulent. The pore diameter of the porous media mainly determines the quenching of the flame. Simply increasing the thickness of porous media may cause the flame to temporarily stop propagating, but the flame is not completely extinguished for larger pore diameter. However, the deflagration propagation speed of flame is affected by the thickness. The attenuation of overpressure by porous media is mainly reflected in reducing the duration of overpressure and the peak value of overpressure. The smaller the pore diameter, the greater the thickness, and the more remarkable the reduction in overpressure duration and peak value. Suitable pore diameter and thickness of porous media can effectively suppress flame propagation and reduce the maximum value and duration of overpressure.     

配式钢混拱桥钢板加固立柱节点抗震研究

为研究装配式钢筋混凝土拱桥腹孔墩柱节点在地震荷载作用下的力学性能和破坏机理,通过拟静力试验和数值模拟计算,对比分析了立柱节点未加固、钢板加固两种情况下的抗震性能.设计制作8mm的钢板加固试件,采用拟静力试验得到试件的滞回曲线、等效阻尼比、初始刚度、荷载-位移骨架曲线作为衡量结构的耗能能力的指标.建立了装配式钢筋混凝土拱...     

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。