井喷失控可燃性蒸气云形成数值模拟研究

利用计算流体力学方法(CFD)对井喷失控发生后天然气喷射流进行数值模拟研究,在有限元的基础上建立模型,采用紊流模型求解Navier-Stokes方程,计算井喷失控后任意时刻可燃气体浓度分布,考察不同风速对气体扩散的影响,最后得出井喷后易爆蒸气云稳定时间随风速变化规律.数值模拟计算结果与实验结果吻合较好,验证了紊流模型和数值算法的可靠性.该研究成果可对井喷失控后所形成的可燃性天然气易燃区域进行预测,有助于预防井场重大天然气着火、爆燃事故的发生.     

井喷点火过程天然气爆炸后果分析

井喷失控事故发生后，尽快点火是减少人员伤亡的最有效措施之一。然而，点火过程中一旦发生天然气爆炸，其可能的爆炸伤害范围、破坏范围以及是否在可接受风险范围，就成为决策能否点火的关键。本文应用蒸汽云爆炸的肿当量模型和冲击波峰值超压模型，提出了天然气井喷失控后，发生天然气爆炸的人员死亡区、重伤区和轻伤区的计算方法；假设井喷的天然气无阻流量，计算了可能的人员伤害范围，并对计算结果进行了分析。分析发现，在井喷失控后，最大限度地减少井喷失控时间，以及最大限度地防止天然气在某一区域的大量积聚，是减轻井喷失控天然气爆炸后果的最佳措施。     

穿越城市生活区的天然气管道泄漏连锁爆燃后果评估研究

为评估城市天然气管道泄漏连锁爆燃事故后果,基于计算流体力学(CFD)方法构建穿越城市区域的天然气管道泄漏连锁爆燃后果预测与评估模型,以某城市生活区域为例,在城市生活区域建筑物内风场流动计算的基础上,模拟风场作用下可燃气体在城市建筑物空间内的运移规律,预测可燃气云的积聚区域;考虑意外点火的情况,计算城市生活区域内可燃气云爆燃灾害特征,预测爆燃超压、热辐射和高温的影响。研究结果表明：由于建筑物之间的阻挡与反射作用,建筑物下风向有明显的低风速区域,并在一定时间段后扩散过程趋于稳定;在爆燃火焰作用下,高温和热辐射会造成建筑物部分钢结构发生失效变形。     

端部开口受限空间汽油蒸气爆燃超压特性研究

基于实验研究了端部开口半受限空间内汽油蒸气泄放爆燃特性,获得了受限空间 内外爆燃超压的变化规律。研究结果表明:受限空间内部超压随时间变化分为点火孕育 期、加速泄流期、外部爆燃期、波动振荡期、衰弱恢复期,爆燃过程中出现多超压峰值 现象且伴随有强烈的压力振荡;随着初始油气浓度的增大,受限空间外部爆燃超压先增 大后减小,外部爆燃超压最大浓度为1.70%;随着比例距离的增加,受限空间外部超压 值呈负指数规律衰减,且横向衰减速率要大于轴向衰减速率。     

钻井井喷失控因素分析及预防对策

井喷失控是钻井中的灾难性事故,有必要开展井喷失控研究,找到井喷失控发生的原因和提出防止井喷失控的对策。在统计分析1970年到2009年间中石油发生在钻进过程中的48例井喷失控事故的基础上,通过对防喷器、节流压井管汇、套管、井喷后爆炸起火等井喷失控因素分析,并利用MLS法对上述各种井喷失控因素危险值进行评估。最后,根据井喷失控因素分析和危险值评估结果,结合现有的钻井井控设计,提出了防止钻井井喷失控的对策。     

海上钻井平台井喷天然气爆燃特性研究

针对海上钻井平台井喷事故特点,基于计算流体动力学(CFD)理论,建立了海上钻井平台井喷天然气爆炸事故的风险预测与评估模型,对不同风况、不同场景条件下的井喷天然气爆燃特性进行模拟和分析,探讨爆燃超压和爆燃火焰的发展规律,并评估其危害程度和影响范围。结果表明:钻台区域最大超压值为6.1 kPa,对平台结构及设备不会造成明显破坏,对作业人员有轻微伤害;悬臂梁内部最大超压值达到10.4 kPa,会造成平台结构、设备轻微损坏,对作业人员伤害严重;分析了不同场景条件下爆燃火焰的发展规律;高温燃烧火焰会严重影响平台结构、设备等钢材性能,导致设备损坏、结构失效甚至坍塌,对附近作业人员会有致命伤害。     

天然气钻井井口安全距离研究分析

分析天然气钻井井场可能发生的事故类型及事故的破坏程度,选择适合的事故后果模型,对天然气井井喷失控后可能发生的蒸气云爆炸及硫化氢扩散的后果进行量化分析,根据超压-冲量准则、热剂量准则和硫化氢扩散行为规律,计算出爆炸波、爆炸火球及硫化氢扩散的危害范围。笔者建立了天然气钻井井口安全距离的计算模型,并提出一种确定安全距离的方法。通过计算给出不同无阻流量、不同硫化氢体积含量的20种条件下的天然气钻井井口安全距离,并应用该模型对某含硫气井井口安全距离进行了计算。实例表明,该方法具备实用性,值得在天然气井选址规划中推广和使用。     

ABC和BC干粉抑制92号汽油蒸气-空气混合物爆炸效果研究

为研究干粉组成及粒径对其抑制汽油蒸气与空气混合物爆炸效果的影响,以92号汽油为例,在220 L爆炸罐基础上建立一整套可燃气体(液体蒸气)抑爆研究装置。选取磷酸铵盐、超细磷酸铵盐和钠盐3种干粉为抑爆剂。通过时间继电器调节点火时间,在油气爆燃转爆轰阶段喷射干粉,比较抑爆前后汽油蒸气爆炸的峰值压力、压力上升速率和能量的变化。试验结果表明:铵盐对汽油蒸气的抑爆效果优于钠盐,适当降低磷酸铵盐的粒径有利于提高气体抑爆效果。超细铵盐抑制汽油蒸气爆炸的效果最佳,能降低58.5%的汽油爆炸压力和31.6%的爆炸能量,3种干粉的最佳抑爆质量浓度分别为:超细铵盐0.682 g/L,铵盐0.228 g/L,钠盐0.455 g/L。     

司钻房爆炸载荷场景下的人员安全撤离分析方法

为有效降低井喷失控场景下人员的应急疏散风险,提出针对司钻房控制室爆炸载荷的安全撤离分析方法。首先,根据司钻房控制室载荷设计规范和布局,确定司钻房的爆炸载荷阈值;然后,运用多能法初步估计爆炸载荷阈值对应的等效气云体积,并构建井喷失控场景平台爆炸仿真模型,借助逆推法确定爆炸载荷的可燃气云体积阈值;最后,针对井喷重组分气体扩散过程的危险气云体积变化曲线,确定不同场景下的可用安全疏散时间T_A,通过对比所需安全疏散时间T_R,判断人员能否安全撤离。结果表明：所提方法可以针对多种井喷场景下的人员安全撤离给出指导建议,其中,井喷速率和风速对T_A有显著影响,当风速增至7 m/s时可以保证司钻人员的安全撤离,而井喷速率的增加则会显著降低T_A,当井喷速率>390 m/s时,会威胁司钻人员的安全撤离。     

海洋平台井喷含硫天然气扩散危险区域研究

针对海洋酸性气田开采过程中含硫天然气井喷失控扩散问题,采用CFD方法建立井喷含硫天然气扩散后果预测与评估模型。综合考虑天然气爆燃与硫化氢毒害风险因素,对不同场景条件下的含硫天然气扩散过程开展数值模拟,研究硫化氢浓度、风向、风速等因素对含硫天然气扩散行为的影响,预测和评估天然气扩散所形成的危险区域和硫化氢气体扩散所形成的毒害范围。研究表明:随着硫化氢浓度的增加,燃爆区域无明显变化,而毒害区域明显增加;船艉来风导致的事故后果最为严重,左、右舷来风有利于危险气体的扩散与消散;风速越大,燃爆区域和毒害区域范围越小,但是在船艏来风且风速较大的工况下,硫化氢气体竖直扩散距离降低且逐渐贴近生活区,容易造成作业人员中毒事故的发生。     

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。     

圆柱形无约束气云爆炸高温效应研究

为了分析无约束可燃气云爆炸产生的高温伤害效应,建立了相应的数学模型,利用有限体积的离散方法,对无约束空间内甲烷浓度10％、高径比为1的圆柱形可燃气云爆炸的瞬态温度场进行了数值研究。研究结果表明,圆柱形可燃气云爆炸的温度场呈不对称性分布,靠近地面处足最危险区域,高温可能达到的最大怪直高度和最大水平距离分别约为圆柱体高的2倍和半径的3．2倍。对数值模拟结果的数据进行多项式拟合,得到了圆柱形可燃气云爆炸场最高温度随水平距离、初温及参与爆炸气云质量的函数关系式,给可燃气云爆炸灾害的预测及防护提供了科学依据。     

Accident modeling of toxic gas-containing flammable gas release and explosion on an offshore platform

Toxic gas-containing flammable gas leak can lead to poisoning accidents as well as explosion accidents once the ignition source appears. Many attempts have been made to evaluate and mitigate the adverse effects of these accidents. All these efforts are instructive and valuable for risk assessment and risk management towards the poisoning effect and explosion effect. However, these analyses assessed the poisoning effect and explosion effect separately, ignoring that these two kinds of hazard effects may happen simultaneously. Accordingly, an integrated methodology is proposed to evaluate the consequences of toxic gas-containing flammable gas leakage and explosion accident, in which a risk-based concept and the grid-based concept are adopted to combine the effects. The approach is applied to a hypothetical accident scenario concerning an H₂S-containing natural gas leakage and explosion accident on an offshore platform. The dispersion behavior and accumulation characteristics of released gas as well as the subsequent vapor cloud explosion (VCE) are modeled by Computational Fluid Dynamics (CFD) code Flame Acceleration Simulator (FLACS). This approach is concise and efficient for practical engineering applications. And it helps to develop safety measures and improve the emergency response plan.     

Evaluating the potential for overpressures from the ignition of an LNG vapor cloud during offloading

Ignition of natural gas (composed primarily of methane) is generally not considered to pose explosion hazards when in unconfined and low- or medium-congested areas, as most of the areas within LNG regasification facilities can typically be classified. However, as the degrees of confinement and/or congestion increase, the potential exists for the ignition of a methane cloud to result in damaging overpressures (as demonstrated by the recurring residential explosions due to natural gas leaks). Therefore, it is prudent to examine a proposed facility’s design to identify areas where vapor cloud explosions (VCEs) may cause damage, particularly if the damage may extend off site.An area of potential interest for VCEs is the dock, while an LNG carrier is being offloaded: the vessel hull provides one degree of confinement and the shoreline may provide another; some degree of congestion is provided by the dock and associated equipment.In this paper, the computational fluid dynamics (CFD) software FLACS is used to evaluate the consequences of the ignition of a flammable vapor cloud from an LNG spill during the LNG carrier offloading process. The simulations will demonstrate different approaches that can be taken to evaluate a vapor cloud explosion scenario in a partially confined and partially congested geometry.     

空间阻塞对室内燃气泄漏爆炸影响研究

以餐饮企业的熟食操作间为例建立物理模型,通过CFD方法模拟不同空间阻塞度下天然气泄漏爆炸情形。研究结果表明:阻塞率在99.95%~100%时,燃气浓度呈现反抛物线式上升。空间阻塞率在99.982%时（开敞面积1 m2）,泄漏1 200 s,熟食操作间燃气浓度值可达6%;空间阻塞率在99.955%（开敞面积2.5 m2）~100%时,燃气爆炸后熟食操作间内产生的超压最大值均大于30 kPa;当空间阻塞率在99.991%（开敞面积0.5 m2）~100%时,设定工况下爆炸超压随空间阻塞率呈指数式增加。研究认为,空间阻塞率在99.95%以上,燃气泄漏极易形成可燃蒸汽云,发生爆炸产生冲击波超压能够毁坏建筑物,在生产和生活中,对于有燃气使用的空间,应尽可能降低空间阻塞率,以避免可能的燃气泄漏形成危险域和爆炸形成过高冲击波超压。     

Analysis and assessment of the Qingdao crude oil vapor explosion accident: Lessons learnt

A devastating crude oil vapor explosion accident, which killed 62 people and injured 136, occurred on November 22, 2013. It was one of the most disastrous vapor cloud explosion accidents that happened in Qingdao's storm drains in China. It was noted that blast overpressure and flying debris were the main causes of human deaths, personal injuries and structure damages. Two months after the accident, it was reported that there were three contentious issues in the investigation report. First issue was the discrepancy between the temperature of the crude oil vapor explosive limits which were measured by the investigation panel and the temperature reported by the local fire department. Second issue was the contradiction between the upper explosive limit and vapor pressure of the crude oil vapor. The last issue was the location of the ignition source which led to the explosion.In the present study some specific features of this accident and various causes led to the explosion, high casualties and severe damages were analyzed. Three contentious issues in the official investigation report were investigated and tested in detail. The first element tested was the explosive limits and limiting oxygen concentration of the crude oil vapor at different temperatures. Based on theoretical analysis and field investigations, the last two elements in the report were analyzed from multiple perspectives. Based on the TNO Multi-Energy model and PROBIT equations, damage probability of affected people at the leaking site was also estimated. The investigation concluded with a result that precautions need to be taken to prevent flammable gas explosions in the drainage systems. Key steps were explicitly discussed for improving the hazard identification and risk assessment of similar accidents in the future.     

A CFD based explosion risk analysis methodology using time varying release rates in dispersion simulations

A full probabilistic Explosion Risk Analysis (ERA) is commonly used to establish overpressure exceedance curves for offshore facilities. This involves modelling a large number of gas dispersion and explosion scenarios. Capturing the time dependant build up and decay of a flammable gas cloud size along with its shape and location are important parameters that can govern the results of an ERA. Dispersion simulations using Computational Fluid Dynamics (CFD) are generally carried out in detailed ERA studies to obtain these pieces of information. However, these dispersion simulations are typically modelled with constant release rates leading to steady state results. The basic assumption used here is that the flammable gas cloud build up rate from these constant release rate dispersion simulations would mimic the actual transient cloud build up rate from a time varying release rate. This assumption does not correctly capture the physical phenomena of transient gas releases and their subsequent dispersion and may lead to very conservative results. This in turn results in potential over design of facilities with implications on time, materials and cost of a project.In the current work, an ERA methodology is proposed that uses time varying release rates as an input in the CFD dispersion simulations to obtain the fully transient flammable gas cloud build-up and decay, while ensuring the total time required to perform the ERA study is also reduced. It was found that the proposed ERA methodology leads to improved accuracy in dispersion results, steeper overpressure exceedance curves and a significant reduction in the Design Accidental Load (DAL) values whilst still maintaining some conservatism and also reducing the total time required to perform an ERA study.     

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.     

气体二氧化氯爆炸特性参数的测定

利用20L圆柱形可燃气体(蒸气)爆炸测试实验装置,用预先配制好浓度的盐酸溶液和亚氯酸钠溶液现场发生反应生成二氧化氯气体,对二氧化氯气体爆炸特性参数进行测定。采用TST6150动态数据储存仪和压力传感器等实验设备获得了高清晰度的二氧化氯气体爆炸压力变化曲线。通过综合分析实验结果,得到了二氧化氯气爆炸极限和爆炸压力变化规律。根据该研究结果,对于预防二氧化氯气体爆炸事故的发生提供数据参考,对指导安全生产和使用,均具有实际意义。