混合气体爆炸性现场测试实验研究

为测定现场可燃混合气体的爆炸性,对比分析了国内外实验室爆炸极限的测定装置及爆炸性判定方法,设计研制了混合气体爆炸性现场测试装置。装置实现了爆炸性环境现场的自动采样、超高温点火、高速压力和温度测定及爆炸性自行判定。开展了丙烷、乙烯和液化石油气等典型可燃气体爆炸性实验,提出了基于压力和火焰温度变化相结合的气体爆炸性判定指标,改变了传统目测判定方式。研究结果表明:20 L球和1 L爆炸腔以爆炸压力提升来判定,比管式法测定的爆炸极限范围窄,以压力提升量5%~10%判定较适宜;1 L爆炸腔以爆炸过程温度提升量来判定,爆炸极限范围比以爆炸压力提升量判定宽,与目测观察的管式测定法相比,略宽于管式测定法和大部分文献数据。     

城市综合管廊燃气舱室输气管道泄漏扩散规律研究

为了掌握输气管道在城市综合管廊舱室泄漏扩散的基本规律,采用FLUENT软件,针对管廊正常通风—泄漏报警—事故通风—警报解除的全过程进行动态分析。首先在正常通风速度建立的稳态风场中,模拟天然气在不同管输压力下发生小孔泄漏后的报警时间,根据首个响应的报警器的位置判断泄漏源位置。结果表明,当泄漏孔径为20 mm,通风速度为1.92 m/s,且泄漏源处于2个报警器中间时,管输压力为200,400,800 kPa时对应的报警时间分别为10.4,6.7,4.5 s。事故通风速度下,对不同管输压力的天然气扩散进行分析,当天然气朝逆风侧扩散时,随动量逐渐减小而到达不同的边界坐标。同时,环境大气压的降低不仅会缩短报警器的首次报警时间,还能延长总扩散距离。预测所得的天然气爆炸上下限浓度区移动速度有助于动态了解处于爆炸上下限浓度之间气体的实时位置。解除报警时间与进风口风速呈近似线性关系,可为现场救援队伍选择经济通风量提供理论指导。     

埋地输氢管道泄漏爆炸事故后果模拟分析

为了输氢管道的安全建设与运营,基于计算流体力学FLACS软件,模拟了埋地输氢管道在半受限空间内的泄漏爆炸事故后果,探讨了泄漏孔径、泄漏时长、输氢压力和环境风速对爆炸事故后果的影响规律,并得出相应的危险区域。结果表明:泄漏孔径、输氢压力和最大爆炸超压均与危险区域呈正相关关系,泄漏时长对事故后果几乎无影响;随着输氢压力的增大,危险区域受建筑物和风速的影响更为明显,在建筑物附近形成了狭长的危险区域带;最大爆炸超压和危险区域随环境风速的增大均呈现出先增大后减小的趋势。     

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。     

Effect of ignition position on vented hydrogen–air deflagration in a 1 m3 vessel

This study investigates the effect of the ignition position on vented hydrogen-air deflagration in a 1 m³ vessel and evaluates the performance of the commercial computational fluid dynamics (CFD) code FLACS in simulating the vented explosion of hydrogen-air mixtures. First, the differences in the measured pressure-time histories for various ignition locations are presented, and the mechanisms responsible for the generation of different pressure peaks are explained, along with the flame behavior. Secondly, the CFD software FLACS is assessed against the experimental data. The characteristic phenomena of vented explosion are observed for hydrogen-air mixtures ignited at different ignition positions, such as Helmholtz oscillation for front ignition, the interaction between external explosion and combustion inside the vessel for central ignition, and the wall effect for back-wall ignition. Flame-acoustic interaction are observed in all cases, particularly in those of front ignition and very lean hydrogen-air mixtures. The predicted flame behavior agree well with the experimental data in general while the simulated maximum overpressures are larger than the experimental values by a factor of 1.5–2, which is conservative then would lead to a safe design of explosion panels for instance. Not only the flame development during the deflagration was well-simulated for the different ignition locations, but also the correspondence between the pressure transients and flame behavior was also accurately calculated. The comparison of the predicted results with the experimental data shows the performance of FLACS to model vented mixtures of hydrogen with air ignited in a lab scale vessel. However, the experimental scale is often smaller than that used in practical scenarios, such as hydrogen refueling installations. Thus, future large-scale experiments are necessary to assess the performance of FLACS in practical use.     

浮式LNG平台串靠卸载泄漏后果影响分析

浮式LNG生产储卸装置(FLNG)作为新兴的深海气田生产装置,集天然气生产、液化、储存和装卸功能于一身,其卸载方式主要有旁靠卸载和串靠卸载2种,其中串靠卸载因能适应恶劣海况而备受深海作业欢迎,但串靠卸载的泄漏后果和影响尚不明确,因此研究恶劣海况下LNG串靠卸载的泄漏风险及后果尤为迫切和重要。考虑海上极端气象条件,采用DNV公司的PHAST软件,定量计算FLNG串靠卸载方式在卸载臂发生小孔、中孔、大孔泄漏及全尺寸破裂时,LNG泄漏后产生的具有火灾爆炸危险性的蒸汽隔离区域,根据伤害阈值明确LNG导致人员低温冻伤和窒息的最小距离,并对可能发生的喷射火、池火和蒸汽云爆炸等恶劣事故造成的后果进行预测。     

串联垂直流人工湿地去除河水中磷的效果

利用在温室内构建的串联垂直流人工湿地模拟装置,以芦苇为湿地植物,填充砾石,研究两种水力负荷(0.2和0.4 m/d)、3个串联级数、有/无植物等对处理北京市清河河水磷去除的影响,试验共持续144 d. 结果表明:①在进水ρ(TP)为0.50~1.77 mg/L(平均值为1.15 mg/L)、ρ(DTP)为0.41~1.53 mg/L(平均值为0.9 mg/L)的条件下,TP去除率随进水ρ(TP)的升高而升高. ②水力负荷为0.2 m/d时,有、无植物3级串联系统磷的去除率分别为38.36%、26.85%;水力负荷为0.4 m/d时,分别为32.42%,23.99%,说明低水力负荷与有植物的条件利于除磷. ③有植物3级串联系统TP去除率平均值为38.36%,大于2级串联系统(28.30%);无植物3级串联系TP去除率平均值为26.85%,大于2级串联系统(21.81%)和1级串联系统(14.98%),串联级数增加,磷去除率升高. 研究显示,水力负荷为0.2 m/d时,有植物3级串联系统的TP去除率最高.      

密闭空间内可燃液体蒸气爆炸强度研究

采用20 L球燃爆实验装置,研究分析了油气浓度、点燃延迟时间的变化对油气环境的爆炸影响因素及变化规律。研究表明,随着油气浓度的增加,油气最大爆炸压力呈现先上升后下降的趋势,点燃延时影响油气-空气混合物爆炸强度,超过一定时间后爆炸猛烈程度降低。     

Explosibility,flammability and the thermal decomposition of Bisphenol A,the main component of epoxy resin

Bisphenol A is one of the basic compounds used in a synthesis of polycarbonates and epoxy resins. Its dust can create an explosive mixture with air under specific circumstances. Therefore, the main goal of this research was to determine explosion characteristics and flammability behaviour of this compound. The complete flammability characteristic requires the determination of the basic parameters of Bisphenol A under fire conditions including Heat Release Rate, speed of combustion, ability to ignite and the temperature of the decomposition range. To establish those parameters, a cone calorimeter was used. The explosion characteristics were tested in a 20-L spherical vessel. Minimum Ignition Energy was tested on MINOR II Apparatus which is a modified Hartman's Tube. In order to identify hazardous substances generated during a fire involving Bisphenol A, a simultaneous thermal analysis that combines thermogravimetry and differential scanning calorimetry was used. The substances obtained from the thermal degradation were analyzed by infrared spectroscope with Fourier transformation. Furthermore, the application of a Purser furnace and gas chromatography with mass spectrometry facilitated the identification of gaseous substances formed during the thermal degradation of Bisphenol A samples.     

Gas explosion analysis of safety gap effect on the innovating FLNG vessel with a cylindrical platform

After investigating gas dispersion on a cylindrical Floating Liquefied Natural Gas (FLNG) platform (Li et al, 2016), this second article focuses on assessment of gas explosion by using Computational Fluid Dynamics (CFD). Gas explosion simulations are carried out to evaluate the explosion overpressure mitigating effect of safety gap. The Data-dump technique, which is an effective tool in resetting turbulence length scale in gas explosion overpressure calculation, is applied to ensure simulation accuracy for the congestion scenario with safety gap. Two sets of different safety gaps are designed to investigate the safety gap on the cylindrical FLNG platform, the overall results indicate that the safety gap is effective in reducing overpressure in two adjacent congestions. However, for the explosion scenario where the flame is propagating through several safety gaps to the far field congestion, the safety gap mitigates overpressure only in certain explosion protecting targets. Two series of artificial configurations are modeled to further investigate the explosion scenarios with more than two safety gaps in one direction. It is concluded that the optimal safety gap design in overpressure mitigation for the cylindrical FLNG platform is to balance the safety gap distance ratio in the congested regions.