基于个人风险的土地利用规划在LNG储备库的应用

对基于个人风险的土地利用规划进行研究,确定方法的框架和程序,并应用于某拟建液化天然气储备库周边的土地利用与布局调整。对拟建天然气储备库可能发生的事故,选取蒸气云爆炸及沸腾液体扩展蒸气爆炸进行讨论。在确定事故发生概率及事故后果的基础上,对拟建液化天然气储备库的个人风险进行计算。借鉴英国土地利用规划中个人风险的可接受标准,在液化天然气储备库周围划分三个风险区域,根据各区域的功能规定及储备库周围土地利用现状,对储备库周围的土地利用进行规划与调整。结果表明,液化天然气储备库附近有两处居民区、一个工厂需要搬迁。基于个人风险的土地利用规划方法在合理确定重大工程选址及周边建筑与设施的布局上是行之有效的方法。     

液化石油气泄漏的危险性分析及其事故后果评价方法

液化石油气（LPG）在其运输和存储过程中存在着各种与火灾和爆炸相关的危险性。由于LPG的泄漏可能导致包括闪火，不可控蒸气云爆炸，沸腾液体膨胀蒸汽爆炸等一系列灾害的发生，针对上述的各种灾害的具体发生条件及其危险性进行了分析；在事故后果评价中采用量化风险分析，提出了沸腾液体膨胀蒸汽爆炸和不可控蒸气云爆炸对周围人员可能造成伤害的评价方法。     

低温容器的蒸汽爆炸现象初探

拟讨论的蒸汽爆炸现象定义为液体因处于较大的过热度而急剧汽化，介质所处空间因大量气体得不到及时释放而使压力骤然升高引发的一种物理爆炸，在低温容器中，液氮，液等介质可能处于数兆帕的压力下，如果容器的某一位置因某种外在原因出现裂口，则其内部的压力会迅速降低，导致液体过热，如果过热度较大，则不能排除低温容器发生蒸汽爆炸的可能性，本文从介绍蒸汽爆炸的机理入手，建立了过热液体中产生均匀核化时汽泡的形成，生长模型，并利用该模型对低温容器的介质发生蒸汽爆炸的可能性进行了探讨。     

小型MRC天然气液化装置中板翅式换热器动态特性仿真研究

针对采用混合制冷剂液化流程(MRC)的小型天然气液化装置(LNG)中的板翅式换热器建立了动态特性仿真数学模型,基于气液两相流理论及气液相平衡理论,对多股流、多组分、有相变的板翅式换热器进行了动态仿真研究,并对该MRC-LNG装置中某换热器在非稳态工况下进行了仿真分析.结果表明:在小型MRC液化天然气装置设计和调试过程中,该模型对提高换热器设计效率、降低运行成本有指导意义.     

水底爆炸气泡脉动特性

为研究水底爆炸气泡脉动特性,采用PAMFLOW软件和基于JWL状态方程的气泡脉动计算程序对水底爆炸气泡脉动特性进行了数值计算,并用经验公式对自由水域爆炸气泡脉动特性进行了计算.计算结果表明水底爆炸在整个气泡运动过程中,气泡的中心向海底贴附,并形成指向海底的高速射流,气泡被压扁;水底爆炸的气泡膨胀半径大于在无限水域中爆炸;2种数值计算结果比较吻合,且与经验公式计算结果相符,说明采用这2种数值计算方法来研究水底爆炸气泡脉动特性合理.     

小型氮膨胀天然气液化流程的设计及优化分析

根据气源条件,设计了3套氮膨胀天然气液化流程,选择PR(Peng-Robinson)方程进行混合物的相平衡计算,采用大型数值模拟软件Aspen Plus进行了数值模拟计算;分析比较了不同液化流程的关键热力学参数,并进行了关键设备的可行性分析.结果表明:丙烷预冷氮膨胀液化天然气流程的比功耗比无预冷的单级氮膨胀天然气液化流程的低,比无预冷的两级氮膨胀天然气液化流程的稍高,两级氮膨胀天然气液化流程较难实现.综合分析结果,选用了丙烷预冷氮膨胀液化天然气流程.     

港口水下爆炸荷载冲击特性研究

采用数值仿真方法研究港口水下爆炸荷载的冲击特性,并与经验公式及实验结果比较验证数值模拟方法的正确性;分析水下爆炸冲击波传播过程与气泡膨胀规律。研究表明,港口水下爆炸气泡膨胀荷载不可忽略,由比冲量知,大部分区域气泡膨胀荷载大于冲击波荷载;自由水面对冲击波荷载与气泡膨胀荷载均影响较大,越接近水面二者比冲量越小,气泡膨胀荷载衰减越快,在水面附近其冲量甚至会小于冲击波荷载。水底对气泡膨胀荷载影响不大,而对冲击波荷载影响较大。受水底反射波影响,冲击波作用时间缩短,导致比冲量迅速减小。水底有淤泥层时,冲击波在泥层与水体交界面反射不显著,水底反射冲击波主要来自泥层底部与岩石层分界面。     

水深和药量的变化对水下爆炸气泡射流的影响研究

假设水下爆炸气泡脉动阶段的流场是无旋、不可压缩的理想流体,运用势流理论导出气泡边界面运动的控制方程,应用气泡动力学模型,用时边界积分法求解得到气泡等边界的变形及位置,在气泡坍塌后运用环状数值模型模拟气泡的非球状回弹,并开发了相应的计算程序,计算结果与精确解吻合很好。运用该文开发的程序计算自由场中环状气泡的运动,计算了流场中滞后流的速度以及压力随时间的变化,并讨论了水深和药量的变化对水下爆炸气泡坍塌形成的射流速度以及气泡脉动周期的影响,得到一些有规律性的曲线,旨在为相关水下爆炸气泡动态特性研究提供参考。     

B型LNG模拟舱内低温流体两相流动与相变传热数值研究

本文以内容积为40 m3，绝热层厚度为400 mm的新型独立B型液化天然气船模拟舱为研究对象，对模拟舱内低温流体的两相流动及相变传热问题进行了非稳态三维CFD模拟。采用流体体积函数（VOF）模型追踪气液相界面，利用Lee模型作为相变模型，在相变模型中考虑了静压的影响，对模拟舱的温度分布及静态BOG生成速率进行了计算。研究了在不同液位以及绝热层存在破损的情况下模拟舱的温度分布及静态BOG生成速率的变化，同时研究了当模拟舱密闭时的增压特性。对比模拟结果与实验结果，偏差在10%以内，模型对模拟舱内的低温液体的蒸发过程模拟较好，可为新型独立B型液化天然气实船的设计和改进提供参考。     

水下爆炸气泡脉动的数值研究磁

利用AUTODYN软件模拟PETN药柱和TNT球形装药水下爆炸气泡脉动的过程,分析了脉动周期与最大半径随装药量、爆炸深度的变化规律。结果表明：当炸药所处的爆炸深度一定时,气泡膨胀最大半径与初始半径的比值、气泡脉动周期与初始半径的比值均为一个定值;一定质量的TNT装药水下爆炸时,气泡最大半径随爆炸深度呈指数形式变化且该变化规律与装药量无关;在不考虑重力的影响下,装药的爆炸深度一定时,当装药的初始半径成倍增加时,气泡脉动最大半径亦成相同倍数增加。     

Experimental investigation on no-vent fill process using tetrafluoromethane (CF4)

This paper investigates the transfer of liquid cryogens using a no-vent fill (NVF) process experimentally to identify the dominant NVF parameters. The experimental apparatus has been fabricated with extensive instrumentations to precisely study the effects of each NVF parameter. Liquid tetrafluoromethane (CF₄) is selected as the working fluid due to its similar molecular structures and similar normal boiling point and triple point with liquid methane which has been considered as an attractive future cryogenic propellant. The experimental results show that the initial receiver tank wall temperature and the incoming liquid temperature are the primary factors that characterize the (non-equilibrium) thermodynamic state at the start of a NVF transfer. The supply pressure is also critical as it indicates the ability to condense vapor in the receiver tank. A non-dimensional map based on energy balance is proposed to find acceptable initial conditions of the filling volume at the desired final tank pressure. The non-dimensional map shows good agreement with the NVF data not only in this paper but also in the previous research.     

外部空间与初始温度对氢气与空气混合气体爆炸过程的影响

为了研究容器形状和初始温度对氢气与空气预混气体爆炸过程的影响,分别采用20 L球形容器和20 L圆柱形容器对氢气与空气混合气体的爆炸过程进行了研究。首先,通过壁面压力传感器获取了两种容器内的最大爆炸压力,并采用高速摄影装置拍摄了球形容器内部爆炸火球的发展变化过程。其次,利用计算流体力学方法对氢气爆炸过程进行了数值模拟,获取了三维爆炸压力场、火焰温度场等爆炸参数,对比分析了容器内不同位置处的压力曲线,并探讨了初始温度对氢气爆炸压力的影响。实验结果表明:在常温下,最大爆炸压力出现在氢气体积分数为30.0%的条件下,略高于理论当量浓度。数值模拟结果表明:两种容器内,火焰传播初期均呈球面往外发展;容器内上壁面的压力均低于右壁面的压力;由于壁面不规则的反射作用,圆柱形容器第1个压力峰值后的压力振荡周期不同步;在体系初始压力不变的情况下,初始温度提高20%,容器内部总的物质的量减少,最大爆炸压力下降15%。     

A review of large-scale LNG spills: experiments and modeling

The prediction of the possible hazards associated with the storage and transportation of liquefied natural gas (LNG) by ship has motivated a substantial number of experimental and analytical studies. This paper reviews the experimental and analytical work performed to date on large-scale spills of LNG. Specifically, experiments on the dispersion of LNG, as well as experiments of LNG fires from spills on water and land are reviewed. Explosion, pool boiling, and rapid phase transition (RPT) explosion studies are described and discussed, as well as models used to predict dispersion and thermal hazard distances. Although there have been significant advances in understanding the behavior of LNG spills, technical knowledge gaps to improve hazard prediction are identified. Some of these gaps can be addressed with current modeling and testing capabilities. A discussion of the state of knowledge and recommendations to further improve the understanding of the behavior of LNG spills on water is provided.     

A simple method for preparing graphene nano-sheets at low temperature

Graphene nano-sheets (GNs) with high quality were successfully synthesized in a Teflon-lined container through a low temperature expansion process. The influence factors of expansion temperature, expansion mode and reduction time on the morphology and structure of products have been systematically investigated, and an optimum experimental condition for the synthesis of GNs has been obtained. The results showed that the Teflon-lined container is an effective apparatus for preparing GNs at relative low temperature (<300 °C). The low temperature synthetic process is simple, inexpensive and easy to scale up in comparison with the traditional method which often consume more energy, use more complicated instruments, or more costly. The electrochemical properties of the as-synthesized products were investigated as anode materials for lithium ion batteries.     

A possible mechanism of triggering a vapor explosion

Relations are derived which enable one to assess the size of fragments of a liquid-metal droplet after its fragmentation formed in the case of instantaneous contact between a hot metal surface and a coolant. The obtained experimental data demonstrate that the amplitude of pressure pulses generated during vapor film collapse (second boiling crisis) is several times lower than the values required for triggering a spontaneous vapor explosion. The assumption is validated according to which progress in studying the process of triggering a spontaneous vapor explosion is associated primarily with advances in understanding the mechanism of fragmentation of individual droplet.     

泄压与隔爆联用的粉尘爆炸压力特性

作为目前市场上运用最广泛的隔爆产品,隔爆翻板阀一般与泄压板联用,以防止粉尘爆炸传播。为了探究粉尘爆炸时泄压与隔爆联用对容器内压力及隔爆效果的影响,进行了工业规模的粉尘爆炸实验。实验结果表明:由于隔爆翻板阀的影响,容器内部出现了二次峰值压力;随着隔爆翻板阀安装距离的增加,容器内两个峰值压力的时间间隔从28.2 ms增加到62.3 ms,且到达隔爆翻板阀前的峰值压力从0.067 MPa上升至0.101 MPa;泄压面积的增大会导致容器内部和隔爆翻板阀前端峰值压力降低,并可能导致隔爆失败。     

泄放阀着火时LNG储罐外容器热-结构耦合分析

针对LNG储罐在泄放阀着火的工况,对受到外界高温火焰辐射的LNG外容器的传热和结构进行了耦合分析研究.建立了16万方LNG大型储罐的实体有限元模型,根据规范和相关文献中的推荐方法,获得了泄放阀火焰高温辐射时罐顶外表面的等效辐射温度,根据正常工作时的稳态传热工况进行储罐外容器内表面等效对流传热系数的计算,得到了正常工作时...     

Performance of the cold transport system utilizing evaporation-freezing phenomena with a cold trap

This paper dealt with the performance of a novel cold transport system for the waste cold from the gasification process of Liquefied Natural Gas (LNG), which has been proposed by one of the authors. The system consists of an evaporator, a cold trap, and a pipeline between them, and the LNG cold poured into the cold trap is transported to the evaporator as a flow of low-pressure water vapor. In this study, cold transport rate of a small-scale system was experimentally examined under various conditions, and the efficiency of cold transport was discussed. The results clearly showed that, as suggested by a theoretical relation based on the pressure drop due to vapor flow in the pipeline, cold transport rate is affected both by the pressure difference between the evaporator and cold trap, and by the length, diameter and friction factor of the pipeline. However it was also shown that the transport rate is hardly influenced by the temperature of pipeline wall. Based on the theoretical relation and the experimental results obtained herein, a guideline for designing the cold transport system was derived.