基于S-A模型的气田井喷失控射流数值模拟的研究

为研究气田井喷失控污染物扩散规律,建立了井喷失控射流的Spalart Allmaras(S-A)湍流模型,应用FLUENT软件进行数值模拟.以"12·23"井喷失控事故案例进行验证,与实际情况比较.结果表明,数值模拟结果与实际情况相符,说明了数值模拟方法的实用性和有效性.     

井喷后硫化氢扩散数值模拟研究现状

随着含硫天然气藏的勘探与开发,井喷后硫化氢扩散的研究显得非常重要.通过查阅大量文献资料,从井喷后硫化氢扩散数值模拟的不同模型入手,对箱及相似模型、API模型、浅层模型、高斯烟羽模型和CFD模型进行了阐述和分析,对比了各类模型的基本原理和优缺点,指出了硫化氢数值模拟的研究方向和完善措施.     

井喷失控点火时间与方位探讨

利用计算流体力学方法(CFD)对井喷失控后天然气扩散过程进行研究,在有限元基础上建立模型,采用κ-ε紊流模型求解得出井喷失控后可燃性蒸气云随时间、风速变化的影响情况,求出稳态以后易爆区域的蒸气云形状。取5.0%和15%作为甲烷的爆炸上、下限,在不同区域进行点火求解爆燃结果,通过比较给出推荐的点火时间和点火方位。该研究成果可对井喷失控蒸气云爆燃危害性进行预测,有助于指导井喷失控进行点火放喷工作,避免爆燃事故的发生。     

基于Fluent的井喷失控有毒气体扩散模拟研究

井喷是石油工业生产中比较常见的一种事故,特别是高含硫气井井喷后会造成重大的人员伤亡,研究H2S气井井喷后毒气扩散规律具有重要现实意义.基于重庆开县“12·23”井喷事件的初始数据,建立了具有障碍物的含H2S气井井喷事故模型.运用Fluent软件对不同高度的障碍物、不同风速、不同井口释放速率三种工况下的含H2S气井井喷扩散情况进行了模拟研究,得出了三种工况下1000ppmH2S的最远扩散距离,为高含硫气井的应急疏散和安全规划提供参考.     

基于CFD的井喷失控喷射火温度场和辐射场模拟仿真

采用CFD方法研究了井喷失控喷射火,阐述了模拟仿真所需的定解条件,论述了模拟仿真采用的数值计算方法,通过模拟仿真得出了井喷失控喷射火温度场和热辐射场的分布规律.结论表明采用CFD方法研究井喷失控喷射火是切实可行的.     

气田井喷硫化氢风洞模拟试验研究

为研究高含硫气田发生井喷事故后硫化氢的扩散运动规律,以重庆开县"12·23"井喷事故为研究对象,利用北京大学的2号环境风洞,制作了1∶2000的比例模型,利用乙烯和丙烯的混合气为示踪气体,采用长采样管方法测量浓度,首次在国内进行了井喷事故后硫化氢扩散的风洞试验,获得了低风速下(源处10m高风速为0.5m/s)N,NE,E,SE,S,SW,W,NW8个风向情况下的硫化氢浓度分布随时间的演化动画,定量地给出了各风向情况下硫化氢的最大浓度分布和各点的浓度时间序列,认为在低风速下,最大硫化氢浓度区域在撞山爬坡时出现,而爬过山坡后在背风区的硫化氢浓度会迅速降低。研究成果将为气田的井喷风险分级以及井喷事故后的应急处理提供参考。     

关于井喷H2S扩散数值模拟初步研究

井喷发生时,在复杂地形和气象条件下,用普通方法很难精确计算出场的时空分布.CFD(Computational Fluid Dynamics)方法虽然理论上能够计算,但是受限于目前的数学基础以及计算机计算能力的限制,CFD方法还很难在大范围地域条件下得到推广和应用.本文的目标就是如何在这些条件下采用合理的假设改进CFD算法,计算出井喷发生后的场的时空分布.在算例中,本文计算维多辛斯基曲线喷嘴射流的流场分布,并与实验值比较.结果证明,所采用的模型和计算方法的计算结果与实际情况基本相符,模型和计算方法可以适用井喷的数值模拟.     

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。     

有障碍物开敞空间可燃气云爆炸超压场的数值模拟

利用计算流体动力学软件AutoReaGas定量研究障碍物、障碍物阻塞比对开敞空间可燃气云爆炸超压场的影响以及爆燃超压随测点距离变化的分布规律。研究结果表明:当有障碍物存在时,爆炸峰值超压会显著增加,且峰值超压随着障碍物阻塞比的增加而增加。对于有障碍物条件下开敞空间的丙烷气云爆炸,无论是气云内部还是气云外部,随着距爆心距离的增加,峰值超压都有减小的趋势。     

扁平圆环局限空间蒸气云爆炸数值模拟及其在事故调查中的应用

传统方法不能深入描述扁平圆环局限空间蒸气云爆炸过程,笔者利用AutoReaGas软件对这一特殊形状和边界条件的蒸气云爆炸过程进行了数值模拟.其结果表明:对于单一点火源,扁平圆环局限空间蒸气云爆炸冲击波传播方向有2个,相向传播的2个冲击波最后会发生叠加效应而使冲击波超压增大;数值模拟结果和事故现场结果对照相吻合,能为事故调查确定最初起爆点位置等提供依据.     

Forced ventilation effect by Air-Fin-Cooler on flammable gas cloud dispersion

This paper is the second installment of a paper published on Process Safety and Environment Protection in 2013, which evaluates the Air-Fin-Cooler (AFC) forced ventilation effect over natural ventilation inside congested LNG process train, i.e., modularized LNG, considering the Air Change per Hour (ACH) using Computational Fluid Dynamics (CFD) analysis. This second paper evaluates the effect of forced ventilation on gas cloud dispersion using CFD in order to evaluate possible design measures, such as safety distance in trains and whether to shut down the AFC in case of releases. The results of this evaluation show that gas cloud accumulation is reduced by AFC induced air flow in the case of shorter separation distances between modules. Based on the results, two design measures are proposed, i.e., keep AFC running during emergency and train orientation against prevailing wind direction.     

深水内波条件下井喷原油扩散规律数值仿真分析

为研究深水内波条件下井喷原油扩散问题,基于计算流体动力学CFD方法,建立深水内波条件下的溢油扩散后果预测模型,研究深水溢油在内波流场中的扩散规律,评估溢油在内波流中的上浮时间、扩散距离等关键风险参数,探讨内波工况、井喷流量及海况条件对深水溢油扩散行为和后果的影响。研究表明:泄漏原油喷射涌入海水中形成射流和羽流,向下部海流出口方向偏移,上升至250m处原油破碎分散为小油滴,受内波剪切作用,扩散范围增大,并向上部海流出口方向偏移,溢出点位置位于泄漏口正上方附近;内波流速变化对原油运移至海面所需时间无明显影响,对横向扩散参数有较明显影响;泄漏速率变化对原油的溢出时间和横向扩散参数均有较明显影响;海况条件对原油溢出时间、运移过程和扩散范围均有较明显影响,其中内波条件下,井喷溢油造成的危害最大。     

Improving flammable mass estimation for vapor cloud explosion modeling in an offshore QRA

Presence of congestion and confinement in offshore modules due to limited availability of space make Vapor Cloud Explosions (VCEs) a significant contributor to risk. There are several methods available for quantifying the blast overpressure generated over distances and time. The approaches range from one-dimensional analysis using correlation models to 3-D analysis using Computational Fluid Dynamics (CFDs). The correlation models are easy to use and well-suited for assessing a number of credible VCE scenarios. However, the overpressure results predicted by correlation models depend on a good estimate of flammable mass. This paper proposes a method to improve the estimation of flammable mass. The UKOOA Ignition model developed by the Energy Institute London is used to estimate the flammable mass; and is modified to account for the effect of mitigation measures on release rate. A directional probability for wind is also added to the model. The proposed model takes into consideration the platform geometry and offshore conditions for each scenario, release location and direction, and wind direction. An offshore production platform with three deck levels is presented as an example case. The flammable mass is also computed using CFD and the results are compared to that of the proposed and the conventional methods. The results show that the flammable masses for selected scenarios are better estimated by the proposed method, being much lower than estimated by the conventional method, though larger than the CFD results. This paper presents an interim result of a project undertaken to improve QRA studies for VCE events.     

On the non-monotonic wind influence on flammable gas cloud from CFD simulations for hazardous area classification

Hazardous areas are defined as a result of a variety of variables as storage temperature, pressure, leak orifice size, physical properties of flammable substance, and wind characteristics. The potential formation of an explosive atmosphere must be accurately assessed to ensure process safety. Therefore, computational fluid dynamics (CFD) arises as an important tool for accurate predictions as recommended by the international standard IEC 60079-10-1 (2015). This study aims to analyze the influence of wind velocity magnitude and direction on the hazardous area classification. The authors evaluated the extent and volume for methane, propane, and hydrogen leakages from a CFD model. For each flammable gas, the wind velocity magnitude and direction were regularly varied. The outcomes show that the behavior of the plume size as the wind varies mainly depends on the gas concentration. Counter-flow wind directions lead to zero relative velocity closer to the release point, which concentrates the gas, and wind in the release direction promotes a higher dilution of the gas cloud increasing the hazardous extent while decreases the volume. As a consequence, the wind also influences the zone type, which was accurately predicted from CFD simulations and significant differences were found when compared to the standard analyses. These differences are, to some extent, related to the consideration of wind velocity effects on the gas jet release.     

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。     

基于BSMPKU的高分辨率大气扩散数值模拟研究

为了检验北京大学街区尺度模式BSMPKU(Block Scale Model of Peking University)在城市大气环境研究中的适用性,首先利用Thompson风洞试验的数据集对BSMPKU模式进行了验证,并将其模拟结果与OpenFOAM(Open Source Field Operation and Manipulation)的模拟结果进行比较,然后将BSMPKU模式应用在复杂的实际建筑物群中,进行了3种不同交通线源排放的理想数值模拟研究.结果表明:1)对于单个建筑物,随建筑物宽度增加,建筑物迎风面回流区和建筑物背风面的尾流涡区范围增大;2)BSMPKU和OpenFOAM对单个建筑物周围的流场及浓度场有较好的模拟能力;3)与基于高斯扩散理论的AERMOD相比,BSMPKU和OpenFOAM能更好地模拟出建筑物周围的浓度场,但两个模式的模拟结果都与实测值存在一定误差;4)在实际小区中,受建筑物群影响,建筑物群内的流场分布比较复杂,大部分地区风速大幅下降,建筑物群内污染物浓度场的分布受排放源位置和走向的影响很大;5)BSMPKU能较好地模拟出实际城区的流场和浓度场分布,具有一定模拟和预报复杂城区污染物扩散过程的能力.     

A multivariable model for estimation of vapor cloud explosion occurrence possibility based on a Fuzzy logic approach for flammable materials

In this paper, a new method based on Fuzzy theory is presented to estimate the occurrence possibility of vapor cloud explosion (VCE) of flammable materials. This new method helps the analyst to overcome some uncertainties associated with estimating VCE possibility with the Event Tree (ET) technique. In this multi-variable model, the physical properties of the released material and the characteristics of the surrounding environment are used as the parameters specifying the occurrence possibility of intermediate events leading to a VCE. Factors such as area classification, degree of congestion of a plant and release rate are notably affecting the output results. Moreover, the proposed method benefits from experts' opinions in the estimation of the VCE possibility. A refrigeration cycle is used as the case study and the probability of VCE occurrence is determined for different scenarios. In this study, sensitivity analysis is performed on the model parameters to assess their effect on the final values of the VCE possibility. Furthermore, the results are compared with the results obtained using other existing models.