井喷喷射火热辐射影响范围与模型对比分析研究

为了评价井喷事故时喷射火的风险,对比分析Flacs、Thornton模型和点源模型在不同泄漏速率、风速下喷射火热辐射强度计算结果,探讨在相同泄漏速率或相同风速下各模型之间的差异.根据塔里木某口油井的工况,分析在风速为7 m/s,泄漏速率分别为200,170,140,120,90 kg/s和在泄漏速率为140 kg/s时...     

Experimental study on the feasibility of explosion suppression by vacuum chambers

In view of the invalidity of suppression and isolation apparatus for gas explosion, a closed vacuum chamber structure for explosion suppression with a fragile plane was designed on the base of the suction of vacuum. Using methane as combustible gas, a series of experiments on gas explosion were carried out to check the feasibility of the vacuum chamber suppressing explosion by changing methane concentration and geometric structure of the vacuum chamber. When the vacuum chamber was not connected to the tunnel, detonation would happen in the tunnel at methane volume fraction from 9.3% to 11.5%, with flame propagation velocity exceeding 2000 m/s, maximum peak value overpressure reaching 0.7 MPa, and specific impulse of shock wave running up to 20 kPa s. When the vacuum chamber with 5/34 of the tunnel volume was connected to the flank of the tunnel, gas explosion of the same concentration would greatly weaken with flame propagation velocity declining to about 200 m/s, the quenching distance decreasing to 3/4 of the tunnel length, maximum peak value overpressure running down to 0.1-0.15 MPa and specific impulse of shock wave below 0.9 kPa s. The closer the position accessed to the ignition end, the greater explosion intensity weakened. There was no significant difference between larger section and smaller vacuum chambers in degree of maximum peak value overpressure and specific impulse declining, except that quenching fire effect of the former was superior to the latter. The distance of fire quenching could be improved by increasing the number of the vacuum chambers.     

液化石油气站储罐区火灾爆炸危险性分析与安全措施

选择具体的液化石油气储配站,分析了该站的危险特性、危险产生的途径及可能造成的后果。在没有任何防护措施的情况下,采用蒸气云爆炸和沸腾液体扩展蒸气云爆炸模型,对该站一个50m3储罐发生泄漏造成的火灾爆炸事故后果进行预测,得出火灾爆炸后的安全距离为大于211．0m。在储配站不能满足此安全距离的基础之上,从防止产生爆炸性气体环境、消除点火源和抑制事故扩大三方面来提出有效的安全措施,降低事故发生的概率及事故造成的损失。其中,站址选在全年最小频率风向的上风侧且周围空旷的地区,罐上设置液位计、压力表、温度计及可燃气体报警器可防止产生爆炸性气体环境;罐及管道设静电接地,法兰用铜线跨接,站内设警示标志可消除点火源;生产区与辅助区间设置隔离墙,罐区周围设置砖混围堤,罐上设安全阀可抑制火灾爆炸事故扩大。     

黄磷储罐火灾临界安全距离理论分析与数值模拟

基于建筑防火隔离带的设计理念,研究了黄磷储罐临界安全距离的计算方法,将黄磷储罐火灾简化为罐内池火模型,通过理论计算和数值模拟黄磷储罐火灾周边热辐射分布,根据目标可燃物接受到的临界辐射通量是否大于或等于10 kW/m2来确定临界安全距离。研究表明：临界安全距离可通过火焰对目标可燃物接受到的临界辐射通量求得,且理论计算和数值模拟计算获得的临界安全距离基本一致。对于黄磷储罐火灾的防治具有一定的参考价值。     

The extreme carbon dioxide outburst at the Menzengraben potash mine 7 July 1953

Carbon dioxide is an asphyxiant and an irritant gas. An extreme outburst of carbon dioxide took place 7 July 1953 in a potash mine in the former East Germany. During 25 min, a large amount of CO₂ was blown out of the mine shaft with great force. It was wind still and concentrated CO₂ accumulated in a valley leading to multiple asphyxiation casualties. Based on a review of concentration-response relationships, the location of victims, and other information, it is concluded that concentrations of 10-30% carbon dioxide may have occurred 450 m from the point of release for at least 45 min. It is concluded that 1100-3900 tonnes of CO₂ were blown out of the mine shaft, possibly with intensities around 4 tonnes/s. It is also concluded that the large majority of the gas escaped as a near-vertical high-velocity jet with only little loss of momentum due to impingement. The release was modelled using PHAST. Output from the model is inconsistent with the asphyxiation harm observed. The high-momentum release is predicted to disperse safely and never reach the ground. Carbon dioxide capture and storage (CCS) schemes will involve handling and transportation of unprecedented quantities of CO₂. Case histories to date include sudden releases of CO₂ of up to 50 tonnes only, far too small to provide a suitable empirical perspective on predicted hazard distances for CCS projects. The 1953 outburst contributes to filling this gap.     

风门对矿井火灾烟气流动特性影响的数值模拟研究*

为研究巷道内风门开启程度对矿井火灾烟气流动特性的影响,使用火灾动力学模拟软件FDS模拟0.5,1.0,1.5,2.0,2.5,3.0 m/s 6种通风风速,以及风门开启1/4,1/2,3/4和全开启4种情况对巷道火灾烟气流动特征参数温度和能见度的影响。结果表明:风速0.5,1.0 m/s 时,风门开启1/4最有利于人员逃生;风速1.5 m/s时,风门开启1/2最有利于人员逃生;风速高于1.5 m/s时,风门关闭影响巷道内风流流动,因此不宜关闭风门;在风门全开启时,随着风速增大,火源上风侧的温度降低、井下能见度升高,烟气的逆退距离缩短,当风速2.5 m/s时各监测点温度最稳定。     

不同隧道坡度下射流风机临界风速研究

为研究隧道坡度对射流风机临界风速的影响,通过理论分析与数值模拟,采用全尺寸隧道模型和5种不同火源功率,考虑0%,±1%,±3%,±5%,±7% 9种不同隧道坡度,研究隧道坡度对射流风机临界风速的影响规律。结果表明:坡度对射流风机临界风速有较大影响。在射流风机与火源纵向间距不小于100 m情况下,即其临界风速与火源纵向间距无关;当上坡时,其临界风速与火源功率的1/3次方成正比,坡度越大,临界风速越小;当下坡时,其临界风速与火源功率的1/3次方成正比,坡度（绝对值）越大,临界风速越大;对数据结果进行拟合,得到上坡与下坡时的射流风机临界风速模型,并与模拟结果取得了较好的一致性。     

Floating roof storage tank boilover

Storage tanks are important facilities for the major hazard installations (MHIs) to store large quantity of crude oil. There is several fire types can occur with large diameter open top floating roof storage tanks. Boilover is considered one of the most dangerous fires in large-scale oil tank. The world has witnessed many incidents due to boilover in floating roof storage tank. Boilover problem has been studied in experiments and by models to understand how to control the boilover phenomena. An experimental study has been carried out in Jebel Dhanna (JD) terminal area by Abu Dhabi Company for Onshore Oil Operations (ADCO) with support of Resource Protection International (RPI) consultant. 2.4 m diameter and 4.5 m diameters pans have been used to study the characteristics of the large oil-tank fires (i) to gain more knowledge of the boilover phenomenon of crude oil (ii) verify if the crude oil stored by ADCO would boilover (ii) estimation of rate of hot-zone growth and the period needed from ignition to boilover (iii) estimation of radiant heat and consequences of boilover. This paper presents an overview on the floating roof storage tank boilover. The paper also presents briefly boilover experimental research study carried out by ADCO.     

The use of water sprays for mitigating chlorine gaseous releases escaping from a storage shed

Accidental releases of toxic gases in partially confined spaces, like a storage shed, can sometimes be controlled by water sprays. This paper presents the results of experimental field tests during which various water sprays were used to mitigate chlorine gaseous releases. The releases (source strength: 1–4 kg/min) simulated a loss of containment occurring at an industrial chlorine storage installation (5 m³). The mitigation performances of different water sprays were investigated for diverse configurations, and under various atmospheric conditions. The best chlorine concentration reduction was achieved close to the source by a mobile upward water spray, with a maximum concentration reduction of a factor 10 at a distance of 5 m downstream from the source, and for a release flow rate of about 2 kg/min. The good performances of a fixed downward flat fan water spray were also pointed out (mean concentration reduction of a factor 2–5 for the whole series of experiments carried out), with an optimum of effectiveness at a distance of 10 m downstream from the source. In low wind speed conditions (U₁₀<1 m/s), the downward flat fan water spray was more effective for weak release flow rates. The mitigation effectiveness by absorption remained slight (<3%).     

甲苯池火灾热辐射数值模拟

文中用CFD技术对甲苯池火灾进行数值模拟,首先对甲苯火焰进行数值计算,得到在稳定的横向风条件下,甲苯燃烧的峰温、产物组分、瞬时速度等火焰特征参数以及其空间分布情况：火焰温度的最高点在对称面y=0上,最高温度为1778K,火焰倾斜角度为26°（与竖直方向夹角）,火焰高为22.5m。然后应用CFD软件F luent对池火灾进行热辐射模拟,模拟结果表明：对于锰钢材料、内径为20m甲苯储罐,稳态有风池火灾情况下,相邻两储罐之间安全距离在上风向为59m,下风向为72m。由于描述燃烧过程和湍流情况的数学物理模型还不太完善、对大气状况的简化等原因,结果偏保守,文中对此进行了分析讨论。此项研究为CFD技术研究碳氢化合物火灾的一个尝试。     

Numerical simulation study of dust concentration distribution regularity in cavern stope

Based on the theory of gas-solid two-phase flow and the characteristics of cavern stope a model of dust migration was established. The dust concentration changing of cavern stope by ventilation in 20 min after blasting and the dust trajectory in different wind speed were simulated by Fluent Software. The results show that distribution of dust concentration is significantly affected by flow field of airway in cavern, and the dust concentration of inlet is higher than that of outlet and the highest one on the corner of inlet’s side. In the stope, the smaller the wind speed of inlet is, the shorter of dust can be captured, settled and discharged, the more obviously affected by the trajectory of gas flow field. It goes into the stage of clean cycle emissions after 60 s, the speed of dust concentration dropped is the biggest between 0 s and 70 s, the main dust in stope is respirable dust after 70 s, it needs much time to settlement.According to the measured data of metal mining, approximately 87% of dust was generated during the drilling and blasting in the mine (Wang, 1979). A lot of dust with high concentrations was produced during the cavern stope blasting and it was difficult to be discharged. It can help choose the right speed to rule out the dust quickly which produced during cavern blasting, if the dust concentration distribution and the dust migration law of different inlet velocity in the cavern can be verified, what’s more, the labor productivity can be increased. It has great significance for choosing reasonable ventilation parameters, reducing dust hazards of stope to researching the dust concentration distribution regularity in the stope.     

Configuration predictions of large liquefied petroleum gas (LPG) pool fires using CFD method

Liquefied petroleum gas (LPG) has potential pool fire risks due to its flammability. The configuration of pool fires plays a significant role when applying the solid flame model or point source model to assess the risks from heat radiation. However, no existing correlations can precisely predict the configuration of large LPG (100% propane) pool fires. To enhance the fundamental understanding on how pool diameter and wind velocity can influence the configuration of large LPG pool fires, an experimentally validated Computational Fluid Dynamics (CFD) model is employed to simulate fires using different burning rate models. Fire temperature profiles, flame heights, and flame tilts predicted by the CFD model were compared with empirical models and experimental data. Accordingly, new correlations for flame height and flame tilt as functions of pool diameter D and wind velocity u_w have been developed. The comparisons demonstrate that the new correlations have the best overall accuracy in the prediction of flame height and tilt for large LPG pool fires under different conditions (10 m ≤ D ≤ 20 m, 0 ≤ u_w ≤ 3 m·s⁻¹).     

全尺寸船舶机舱火灾烟气填充研究

为研究机舱火灾烟气蔓延的特点,进行了全尺寸机舱火灾烟气填充试验,在试验舱室内设置4个不同尺寸的填充物,研究不规则截面舱室的烟气沉降规律,同时改变油池尺寸和抬升火源研究火源功率和火源高度对烟气温度分布和烟气层沉降的影响。结果表明:随火源功率增大,顶棚和侧墙的温度升高,烟气的沉降速率增大,当火源功率较小时顶棚温度较低,以温度为阈值的消防喷头失效;将火源抬升4 m时烟气温度及烟气沉降速率均升高,但烟气层稳定在8 m高度,舱室底部形成一个相对安全的空间。另外,基于Zukoski羽流模型和质量守恒,推导出不规则截面烟气沉降理论预测模型,与前人的模型对比,该理论模型预测值更接近实际观测值。     

Analyzing effective factors on leakage-induced hydrogen fires

Currently, novel energy resources are receiving increasing attention as a response to the limitation in fossil fuels as well as their adverse effects on human health. Hydrogen, one of the most abundant elements on the earth, can be regarded as a new energy source to replace fossil fuels. Therefore, safety assessment of the relating processes is very crucial by increasing use of hydrogen as a fuel source. In this regard, consequence analysis for risk assessment and power reduction is very important. The present study aims at modeling hydrogen dispersion along with consequence analyses for such events as jet fire and flash fire. The model was validated by using the data derived from a study on hydrogen leakage in supply pipelines in the laboratory of the University of Pisa. Modeling results reveal that ambient conditions will impose a milder impact on leakage consequences if internal pressure is high in release source. The safe distance was also estimated to be 14 m. Dispersion consequence modeling was performed, followed by the evaluation of the effect of environmental (i.e., stability, ambient temperature, surface roughness, wind speed, and humidity) and process (i.e., vessel temperature and pressure, leakage diameter, and releasing point height) parameters on maximum size flammable vapor cloud and maximum level jet fire radiation on the ground. The size of flammable vapor cloud (consequence dispersion index) and the maximum flux of radiation were affected by process parameters more than ambient parameters. Leakage diameter and the vessel pressure were found to have the highest impact on the operational parameters.     

基于微积分的LPG和CNG喷射火模型建立和三维数值模拟

由液体和气体泄漏引发的喷射火灾事故屡见不鲜,而现有的喷射火模型却有诸多缺陷。将喷射火形状近似为圆锥,鉴于液体和气体的泄漏速度随压强和温度均有变化、点源离地面会有一定高度、风速对火焰倾角也有影响、圆锥喷射中心线上每个点源对目标的热辐射均不同等实际情况,新建液体和气体扩展半径的计算方法,引入风速对火焰高度和火焰偏角的作用,比较AGA法和Thornton模型,发现AGA法更加符合实际,再利用微积分原理建立三维点源喷射火模型,展示火焰形状对目标的影响,从而得出热辐射的最终危险性。最后以LPG和CNG储罐喷射火事故为例进行对比验证,首次模拟出喷射火的形状,更清晰准确地展示了目标入射热辐射通量随目标点位置的变化和危险范围,可为火焰阵面处的消防安全决策提供参考。     

Study on difference of outburst elimination effect between sub-layers of soft coal and hard coal under the condition of gas per-drainage

The effect of drainage and outburst elimination are obviously different between soft and hard coal sub-layers under per-drainage of coal seam, and hence, the location of per-drainage borehole related to the soft sub-layer is the key that determines whether the outburst can be eliminated in whole coal seam. This paper discusses the differences between soft and hard coal from fields of pore radius distribution, pore structure, surface area and permeability, and the per-drainage effect was numerical simulated under different distance between per-drainage hole and soft sub-layer. Moreover, the optimum hole arrangement of outburst elimination is given in the paper. The result of research shows that the macro-pore with aperture that is larger than 50,000 nm, is dominant at about 50% in hard coal, correspondingly, the micro-pore with aperture less than 100 nm accounts for about 41.23% in soft coal. The surface area of soft coal is 1.6 times as that of hard coal. The residual gas content in soft coal sub-layer is obviously more than it in hard coal sub-layer under the same pre-drainage condition. To 5.5 m-thick coal seams which top is a soft coal sub-layer of 0.5 m-thick, pre-drainage gas can eliminate danger of gas outburst in whole coal seam at the seam time after 455 days drainage when the per-drainage holes are 1.0 m distances from the soft coal sub-layer.     

Research and practice on fluctuation water injection technology at low permeability coal seam

In order to solve the problem of poor affusion effect on low permeability coal seam, the paper analyzes the micro process of the coal seam water infusion in wetting coal and determines the main factors affecting coal seam water infusion. The permeability of the NO.3 coal seam in east working face of Xingcun coal mine by MTS815.03 servo-controlled rock mechanical test system has been tested. Results show that when the peak stress in coal sample specimens reaches 48.53 MPa, permeability ranges from 0.5158 to 2.9576 × 10⁻⁸ Darcy, and it means that the coal seam is low in permeability and difficult in water injection. Based on the characteristics of low permeability and geostress situation, efficient fluctuation water injection technology with permeable agent and relevant process parameters have been designed. The surface tension of the permeable agent developed here is 31.18 m N/m when mass concentration reaches 0.05%. The permeable agent can permeate into 2 cm thick coal layer completely in 10 s, thus improving the wettability of water effectively and the water injection pressure fluctuates between 7 MPa and 25 MPa. The application of the technique in the 3rd coal seam in east working face of Xingcun coal mine shows not only single-arch injection experienced a significant increase on average, from no more than 10 m³ to 63.3886 m³, but also the effect of dust fall, cooling and rock burst prevention is remarkable.     

风速对LNG泄漏扩散过程影响的数值模拟

为研究环境风速对液化天然气(LNG)泄漏扩散过程的影响,采用Fluent建立LNG连续泄漏计算流体力学模型,开展不同风速下LNG泄漏扩散过程的数值模拟研究。结果表明,LNG泄漏扩散分为扩散初期、扩散中期、扩散后期3个阶段,扩散过程中LNG从低温重气逐渐转变成轻质气体。环境风速对气云的扩散主要体现在:低于5级风时,云团以两侧卷吸为主,气云表现为"叶状分叉"、中间低两端高,此时气云横风向扩散较快,甲烷扩散距离与冻伤距离随风速增大而增大;而高于5级风时,云团以顶部卷吸为主,气云表现为云团坍塌、中间高两端低,此时气云垂直风向扩散较快,甲烷扩散距离与冻伤距离随风速增大而减小。初步建立了LNG蒸气云爆炸风险范围与冻伤区域和泄漏时间、环境风速的函数关系,可为爆炸风险区域和低温冻伤区域的预测提供理论支撑。