重气云团瞬时泄漏扩散的数值模拟研究

事故性泄漏多形成重气云团 ,其扩散行为与非重气云团有很大的不同 ,主要包括重力沉降、空气卷吸、云团加热和向非重气云团转变四个阶段。文中从控制重气云团扩散行为的微分方程入手 ,根据箱模型(boxmodel)及其他一些重气扩散模型 ,如IITHeavyGasModels模型和虚点源模型 ,采用向前插分和牛顿迭代的方法 ,针对ThorneyIslandTrialNo .0 0 8试验进行了数值模拟 ,得到了重气云团外形尺寸 (云团半径和云团高度 )和空气卷吸量随时间的变化关系以及下风向固定点处地面最大浓度值。数值模拟结果较好地反映了重气云团所特有的扩散行为。针对数值模拟结果与试验实测值之间存在的偏差进行了分析 ,结果表明 ,采用该方法进行重气云团瞬时泄漏扩散模拟是可行的 ,且模拟精确度高于IITHeavyGasModels模型     

危险有害物质泄漏扩散风险分析

介绍有害物质泄漏扩散数学模型：高斯模型和重气扩散模型，并分别运用高斯烟团模型和重气盒子模型对液氯泄漏扩散案例进行了模拟计算，反映出有害物质扩散半径、温度、高度及浓度等参数的变化规律，并对两种模型计算结果进行比较。认为泄漏介质密度大于空气的应运用“重气扩散模型”，制定风险对策时应结合当地实际情况对计算结果进行修正。     

氯气泄漏扩散影响因素的数值模拟研究

基于FLUENT的物质传输模型建立氯气泄漏扩散模型,针对不同泄漏速率、外界风速、障碍物类型等对氯气泄漏扩散进行数值模拟.结果表明,泄漏速率较大时,重气效应明显增大,下风向形成的高浓度区增大;外界风速对重气扩散浓度和扩散危险性区域有很大影响,风速较大时,重气云在下风向的扩散速率增大,在水平侧风向的扩散速率减小,在泄漏源和障碍物附近的停留时间减少,形成的危险区域较小;不同的地表条件是影响重气扩散的重要因素.     

石油化工气体泄漏扩散模型研究进展

综述了国内外气体泄漏扩散模型的研究进展,简述了重气扩散模型及其发展情况,讨论了各类模型的优势及局限性,指出了扩散模拟未来可能的发展趋势,以及后续研究的方向。     

LNG垂直喷射源连续泄漏扩散的模拟

对液化天然气(LNG)扩散的物理过程进行了理论分析。针对垂直喷射源连续泄漏扩散特点,将液化天然气扩散过程分为重气扩散与被动扩散两个阶段。结合烟羽抬升计算,在两个阶段分别采用SLAB稳态烟羽模型与高斯烟羽模型,建立了液化天然气扩散过程数学模型。研究了垂直喷射源泄漏形式和不同环境条件下的扩散情形。对液化天然气泄漏后混合云团扩散形成的浓度场、温度场和其他特征参数进行了模拟。得到重气扩散阶段随下风向距离增大,扩散云团高度、宽度、温度、密度、云团中液化天然气蒸气含量、水含量的变化规律,被动扩散阶段云团中液化天然气质量分数的变化情况。可以为事故危害范围的测定、事故后人员的疏通和补救工作的指导提供帮助。     

液化天然气水平连续泄漏重气的扩散过程

结合SLAB稳态烟羽模型,针对液化天然气(LNG)连续泄漏、水平喷射源的重气扩散过程进行了模拟研究,分析了液化天然气泄漏后混合云团扩散形成的浓度场、温度场和其它特征参数。利用MATLAB语言编制液化天然气连续泄漏扩散模拟程序,对两种试验环境条件(不同风速、大气温度、大气稳定度、相对湿度和地表粗糙度等环境参数)下扩散云团的特性参数进行模拟计算,得到各云团参数随下风向距离的变化规律。     

Research on the LNG dense gas diffusion: A continuous horizontal jet release

结合SLAB稳态烟羽模型,针对液化天然气（LNG）连续泄漏、水平喷射源的重气扩散过程进行了模拟研究,分析了液化天然气泄漏后混合云团扩散形成的浓度场、温度场和其它特征参数。利用MATLAB语言编制液化天然气连续泄漏扩散模拟程序,对两种试验环境条件（不同风速、大气温度、大气稳定度、相对湿度和地表粗糙度等环境参数）下扩散云团的特性参数进行模拟计算,得到各云团参数随下风向距离的变化规律。     

重质气体泄漏扩散模型研究综述

扼要概括和评价了重质气体泄漏扩散的三种主要模型：唯象模型、工程模型、三维传递现象模型,唯象模型和工程模型由于使用方便、概念清晰且计算量较小,主要用于风险评估和环境评估系统,是应急咨询和安全设计的重要工具。而三维传递现象模型能够更好地描述重气在复杂地形和气象条件下的扩散过程。通过各类模型的介绍指出了近几年重气泄漏扩散模型将向多组分重气在复杂地形、气象条件下的扩散模拟研究等方向发展。     

扩散和化学反应的多物质格子气自动机模型

运用细胞自动机模型方法,建立了多物质格子气自动机模型,并对混合体系中的扩散传质和简单气固相化学反应现象进行了模拟.结果表明,作为一种从微观离散运动论角度模拟宏观现象的方法,多物质格子气自动机模型可以定性模拟一些典型的扩散和化学反应现象.     

液氯瞬时泄漏扩散的数值模拟

在箱模型的基础上,用适当简化方式对高压常温液化贮存的液氯泄漏扩散进行了数值模拟,充分说明了重气效应的影响;通过数值模拟,认为云团液滴汽化、温度变化的这一短暂过程可近似看成是云团在泄漏源处的重力沉降,以一合适的初始半径高度比,作常态氯气泄漏扩散考虑,使得计算简化。这种近似模拟结果与液氯泄漏扩散模拟结果基本相近,如下风向距离浓度等。以常态氯气泄漏扩散近似高压液化贮存氯气扩散,其初始半径高度比取决于风速,与泄漏介质的量及大气稳定度无关。     

Molecular simulation,experiments and modelling of single adsorption capacity of 4A molecular sieve for CO2–CH4 separation

Monte Carlo simulation of CO₂ and CH₄ adsorption on zeolite 4A is carried out in grand canonical Monte Carlo (GCMC) simulation. LTA framework was used to reproduce the structure of zeolite 4A. A comparison between the structure and properties of this zeolite and 13X, ZSM-5, 4A and 3A is performed and the results are included in the article. Universal force field was used for calculation of intermolecular forces. Our own experiments were also carried out to reinvestigate the simulation results. Ewald summation method was used for calculating electrostatic forces and atom based method was applied for van der Waals forces. The simulation results show good agreement with experimental results. Highest CO₂ adsorption capacity of zeolite 4A was in good agreement with experiments at the same pressure ranges, and was found to be 3.17 mol/kg from GCMC. Isosteric heat of adsorption was calculated to find the heat released during adsorption of each gas. Finally simulation results were fitted to four isotherms to find the best fit.     

汽车保险盒上盖注射成型的数值模拟

利用Moldflow软件对汽车保险盒上盖的注射成型过程进行了数值模拟.通过分析填充过程中各时间段熔体的流动情况及最终的填充时间和填充效果,得出了制品的最佳填充时间和保压时间;通过分析成型过程中型腔的温度变化,预测了制品的熔接痕和气穴的分布,以及缩水、翘曲变形等成型缺陷,并通过实际注射成型对模拟进行了验证.实验证明,模拟结果非常真实地表现了制品实际的成型过程,其对成型缺陷的预测也比较准确,证明了注射成型数值模拟结果的可靠性.     

A methodology to evaluate coal ash content using Siderite Mössbauer spectral area

A methodology was used to evaluate Low Temperature Ash (LTA) and High Temperature Ash (HTA) through Mössbauer Spectroscopy (MS). Siderite was the only Mössbauer Spectral presenting a good correlation between the spectral area and the ash content obtained by LTA and HTA. The calibration curves obtained for HTA and LTA gave a correlation coefficient of 0.968 and 0.988, respectively. The LTA results present the best correlation, given that this process does not change the original mineral phases. This methodology was the advantageous for easily obtaining coal ash content, through curve ash content vs. MS area, without carrying out ashing processes.     

Electrical conductivity of LTA‐zeolite in the presence of poly(vinyl alcohol) and poly(vinyl pyrrolidone) polymers

In this work we studied the electrical behavior of Linde type A zeolite (K⁺) in the presence of two polymers, poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP), with excellent film forming properties. Homogeneous composite thin films of PVA/LTA‐zeolite and PVP/LTA‐zeolite were prepared with different zeolite concentrations. The current?voltage (I?V) characteristics of the composites were measured at different applied voltages. The results show that the conductivity properties are composition‐ratio‐dependent and are also related to the type of polymers. Moreover, a well‐defined step‐like change was detected in the I?V curve of PVP/LTA‐zeolite at very high applied voltage. © 2013 Society of Chemical Industry     

In Situ Ultrasonic Measurements as a Tool to Characterize the Stages of the Zeolite A Crystallization Process

Zeolite A (LTA) was synthesized at 80 °C under hydrothermal conditions from a gel with the molar composition of 2.5 Na₂O : 2 SiO₂ : Al₂O₃ : 80 H₂O. In the present study, we report the use of home-made ultrasound devices as a real-time, in situ diagnostic tool for monitoring the progress of zeolite formation. In addition, the specific aim of this study was to show that the measured ultrasound parameters – ultrasonic (US) velocity and attenuation – simultaneously provide independent information about the changes in the liquid and solid phase, respectively, during the crystallization process. Both views are necessary for extracting kinetic data about the zeolite crystallization processes and allow elucidating the different stages of zeolite LTA formation process. The obtained in situ US data were compared with conventional ex situ powder X-ray diffraction measurements following the formation of zeolite LTA from dense gels. The results demonstrate that a good correlation exists between the crystallization progress of zeolite LTA in terms of crystallinity changes and the ultrasonic attenuation and velocity.     

Nucleation and growth history of zeolite LTA synthesized from kaolinite by two different methods

The synthesis of zeolite Linde Type A (LTA) from kaolinite by two different routes: (1) conventional hydrothermal alkaline activation and (2) alkaline fusion prior to hydrothermal reaction, as well as its nucleation and growth history, were investigated. Using the first method, co-crystallization of sodalite and cancrinite, probably via an unstable zeolite LTA intermediate, was observed during treatment of kaolinite in NaOH solutions. The addition of a SiO₂ source promoted the co-precipitation of several zeolite phases, including zeolites LTA, X and P, with traces of sodalite and cancrinite. By fusion with NaOH followed by hydrothermal reaction, kaolinite was converted into zeolite LTA. Synthesized materials appeared stable thermodynamically under the experimental conditions. The synthesis products have been characterized by X-ray diffraction, scanning electron microscopy and Fourier Transform Infrared Spectroscopy.     

A Brownian dynamics simulation method for analyzing particle behavior in nonuniform and alternating electric fields

A new iterative Brownian dynamics simulation (BDS) method for analyzing the diffusive behavior of particles in an alternating electric field is proposed and tested in comparison with several previous techniques, including the most widely used BDS method developed by Ermak. To evaluate the proposed method with other schemes, particle trajectories in constant, AC, nonuniform DC in DMA, and quadrupole electric fields were obtained from each algorithm with various integration time steps. It is shown that the proposed BDS method is much more accurate at predicting the mean and variance of particle position for most cases. With respect to algorithm efficiency, the new scheme is about 5–50 times more efficient than the conventional BDS method for high-frequency AC electric fields. The simulation results for a particle beam generated in a quadrupole electric field show that the selection of a suitable algorithm and the proper size of time step are important for calculating system properties related to the diffusive motion of particles. In addition, a correction to the stochastic term is suggested and its effect investigated.     

Synthesis and Biological Activity of the Lipoteichoic Acid Anchor from Streptococcus sp. DSM 8747

In this study, the role of lipoteichoic acid (LTA) anchors in the activation of the innate immune response was investigated through the chemical synthesis of a series of LTA derivatives and the determination of their ability to induce NO production in bone marrow‐derived macrophages (BMM). To this end, an efficient synthesis of the sn‐3‐O‐(α‐D ‐galactofuranosyl)‐1,2‐di‐O‐acylglycerol LTA core was developed, which was then used as a key structure to produce both phosphate and glycerylphosphate‐funtionalised LTA anchors, as well as galactofuranosyldiglycerides with different fatty acid chain lengths. With a series of LTA anchors in hand, we then determined the effect of these glycolipids on the innate immune response by exploring their capacity to activate macrophages. Here, we report that several of the LTA‐derivatives were able to induce NO production by BMMs. In general, the unnatural (sn‐1) core glycolipid anchors showed lower levels of activity than the corresponding natural (sn‐3) analogues, and the activity of the glycolipids also appears to be dependent on the length of lipid present, with an optimum lipid length of C20 for the sn‐3 derivatives. Interestingly, a triacylated anchor and the 6‐O‐phosphorylated anchor, showed only modest activity, while the 6‐O‐glycerophosphorylated derivative was unable to induce NO production. Taken as a whole, our results highlight the subtle effects that glycolipid length can have on the ability to activate BMMs.     

石油产品颜色测定仪在油品分析中的应用

本文介绍了自动石油产品颜色测定仪的分析原理及测定油品颜色时的注意事项,给出了手动和自动测定同一样品颜色的结果,同时进行了两个方法的结果比较,分析了误差及解决的办法.     

Analysis of the Water Permeability of Linde Type A Zeolites in Reverse Osmosis

In this paper, we apply the Hagan-Poiseuille Model and the resistance model to perform an original analysis of previous experimental studies of water transport through polycrystalline Linde Type A (LTA) zeolite membranes and nanocomposite polymer/LTA membranes. From our analysis we estimate the intrinsic water permeability of LTA zeolites and the zeolite/polymer interface. We find that the permeability of a single LTA crystal is significantly greater than the intrinsic permeability of a commercial seawater reverse osmosis membrane or a commercial cellulose-acetate forward osmosis membrane.