Large Eddy Simulation of Liquid Flow in a Stirred Tank with Improved Inner-Outer Iterative Algorithm

In this study, the large eddy simulation technique was applied on the flow in a baffled stirred tank driven by a Rushton turbine at Re=29000. The interaction between the rotating impeller and the static baffles was accounted for by means of the improved inner-outer iterative algorithm. The sub-grid scale model was a conventional Smagorinsky model. The numerical solution of the governing equations was conducted in a cylindrical staggered grid. The momentum and the continuity equations were discretized using the finite difference method, with a third-order QUICK scheme used for convective terms. The phase-resolved predictions were compared with the experimental data of Wu and Patterson and good agreement was observed for both the mean and the turbulence quantities. They were much better than the Reynolds-averaged Navier-Stokes model including the Reynolds Stress Model for simulating the turbulence. The study also suggests the feasibility of LES in combination with the improved inner-outer iterative algorithm for the simulation of turbulent flow in stirred tanks.

Large Eddy Simulations of Flow Instabilities in a Stirred Tank Gen-erated by a Rushton Turbine

The aim of this work is to investigate the flow instabilities in a baffled, stirred tank generated by a single Rushton turbine by means of large eddy simulation （LES）. The sliding mesh method was used for the coupling between the rotating and the stationary frame of references. The calculations were carried out on the ＂Shengcao-21C＂ supercomputer using a computational fluid dynamics （CFD） code CFX5. The flow fields predicted by the LES simulation and the simulation using standard κ-ε model were compared to the results from particle image velocimetry （PIV） measurements. It is shown that the CFD simulations using the LES approach and the standard κ-ε model agree well with the PIV measurements. Fluctuations of the radial and axial velocity are predicted at different frequencies by the LES simulation. Velocity fluctuations of high frequencies are seen in the impeller region, while low frequencies velocity fluctuations are observed in the bulk flow. A low frequency velocity fluctuation with a nondimensional frequency of 0.027Hz is predicted by the LES simulation, which agrees with experimental investigations in the literature. Flow circulation patterns predicted by the LES simulation are asymmetric, stochastic and complex, spanning a large portion of the tanks and varying with time, while circulation patterns calculated by the simulation using the standard κ-ε model are symmetric. The results of the present work give better understanding to the flow instabilities in the mechanically agitated tank. However, further analysis of the LES calculated velocity series by means of fast Fourier transform （FFT） and/or spectra analysis are recommended in future work in order to gain more knowledge of the complicated flow phenomena.

Floating-roof steel tanks under harmonic settlement: FE parametric study and design criterion

Large vertical steel tanks for fluid storage are usually constructed on soft foundations, so it is not surprising that the tank wall will settle unevenly with the settlement of the foundation, thus inducing deformations and stresses in the tank. This work investigates the linear static behavior of floating-roof tanks under harmonic settlement through finite element (FE) analyses. The influences of the radius-to-thickness ratio, the height-to-radius ratio and the wind girder stiffness on the structural behavior are first analyzed. Comparisons between the circumferential stresses in the wind girder and the vertical stresses in the tank bottom are then made. The displacement and the stress along the tank height are also discussed, and the concept of tank division along its height is presented. Finally, a design approximation for the radial displacement at the tank top is developed based on FE results, and a settlement criterion based on the top radial displacement is proposed which can be used in practical design.

Influence of Wind Deviation Angle on n-Hexane Evaporation Loss of Internal Floating-Roof Tanks

With the increasing attention to environmental protection,it is still necessary to strictly control the oil evaporation loss from the IFRT(internal floating-roof tank)to the atmosphere.Upon using n-hexane as a representative of light oil,the effects of the WDAs(wind deviation angles)on airflow distribution,the wind speed,the n-hexane vapor concentration,and the evaporation loss rate in the IFRT were investigated,and the mass transfer of the vapor-air was analyzed.The results are shown as follows:when the WDA is 0°,the vapor concentration in the gas space above the floating deck is the lowest;when the WDA is 22.5°,the oil evaporation loss rate is the largest;when the WDA is 45°,the vapor concentration is the highest,but the evaporation loss rate is the smallest.It is recommended to arrange the vent to the wind direction with an angle of 45°to reduce the evaporation loss and protect the atmospheric environment.

Large Storage Tank Structure Design Cases-Based Teaching in Teaching Reform for Major of Oil&Gas Storage and Transportation Engineering

As one of the compulsory courses of oil and gas storage and transportation engineering,“Strength Design and Safety Management of Storage and Transportation Facilities”is a comprehensive course of both practicality and theory.In order to solve the unbalanced distribution of theoretical and applied content in the teaching process,the teaching team reformed the teaching mode of the structure design of large storage tanks in the course of“Strength Design and Safety Management of Storage and Transportation Facilities”and introduced case-based teaching.On the basis of the original course,practical engineering case analysis such as wind-induced buckling of large storage tank and uneven settlement of tank foundation was added,which increased the proportion of application content.It is a new type of discussion teaching integrating case collection,group discussion and afterclass experience exchange.According to the recent three years of teaching practice,students’interest in this course has increased greatly and teaching quality has improved significantly,which fully verified the feasibility of engineering case-based teaching in teaching reform.The teaching team has gradually improved the teaching process according to the relevant experience and lessons in classroom practice and made a successful attempt in the teaching reform of storage and transportation structure safety courses,which is of positive significance for training application-oriented composite talents with the ability to solve practical problems in the new era.

The Research Application of 3D Laser Scanning Technology in the Deformation Detection of Large Cylindrical Oil Tank

In order to ensure the safety in using a large cylindrical storage tank,it is necessary to regularly detect its defonnatioii.The traditional total station method has high accuracy in determining the deformation,however,it has a low measxirement efficiency.Long-term observation means,there are more risks in the petrochemical plant,therefore,this paper proposes the usage of the 3D laser scanner,replacing the traditional total station to determine the defbnnation of a large cylindrical storage tank.The Matlab program,is compiled to calculate the point cloud data,while the tank deformation is analyzed from two different points which are,the local concave convex degree and the ovality degree.It is concluded that,the difference between the data obtained by 3D laser scanning,and total station is within the range of oil tank deformation limit,therefore,3D laser scanner can be used for oil tank deformation detection.

Numerical simulation of stirred tanks using a hybrid immersed-boundary method

Conventionally, multiple reference frame(MRF) method and sliding mesh(SM) method are used in the simulation of stirred tanks, however, both methods have limitations. In this study, a hybrid immersed-boundary(IB)technique is developed in a finite difference context for the numerical simulation of stirred tanks. IBs based on Lagrangian markers and solid volume fractions are used for moving and stationary boundaries, respectively, to achieve optimal efficiency and accuracy. To cope with the high computational cost in the simulation of stirred tanks, the technique is implemented on computers with hybrid architecture where central processing units(CPUs) and graphics processing units(GPUs) are used together. The accuracy and efficiency of the present technique are first demonstrated in a relatively simple case, and then the technique is applied to the simulation of turbulent flow in a Rushton stirred tank with large eddy simulation(LES). Finally the proposed methodology is coupled with discrete element method(DEM) to accomplish particle-resolved simulation of solid suspensions in small stirred tanks. It demonstrates that the proposed methodology is a promising tool in simulating turbulent flow in stirred tanks with complex geometries.

Review on the Progress and Issues in Liquid Tank Sloshing of Ships

With the development of large liquid cargo ships,liquid tank sloshing has gradually become a hot research topic in the area of shipping and ocean Engineering.Liquid tank sloshing,characterized by strong nonlinearity and randomness,not only affects the stability of the ship but also generates a huge impact force on the wall of the tank.To further investigate liquid tank sloshing,a comprehensive review is given on the research process of the most focused subjects of liquid sloshing.Summarizing the existing research will help to identify issues in the current field and provide useful references.The methods for investigating sloshing,the research progress and the situations worldwide are discussed.The advantages and defects of experiments and numerical simulations are also explored.The problems which need to be explored in the future are subsequently proposed.

大型集装箱船甲醇燃料舱结构设计

针对甲醇作为船舶替代燃料的特点,提出一种适用于大型集装箱船的甲醇燃料舱设计方案,以一艘大型集装箱船为例,采用有限元方法来验证甲醇燃料舱区域的结构强度,同时探讨燃料舱端部节点设计对船体结构强度的影响。为大型集装箱船甲醇燃料舱的结构设计提供参考。

黄酒在大罐微氧贮存中挥发酯和总酸的变化

通过对黄酒大罐微氧贮存过程中挥发酯的变化及其影响因素的跟踪检测分析。结果表明:在保证酒质的前提下,通过对大罐酒温度变化的控制,实现微氧循环,提高了挥发酯的含量,从而提高大罐贮存效率,降低了生产成本。

风荷载作用下储罐罐壁的力学性能

为研究大型钢制储罐在风荷载作用下的力学特性,借助有限元软件ABAQUS,建立了静力风荷载作用下储罐有限元模型,对比分析裸罐(不含抗风结构)与加强罐(含抗风结构)在风荷载作用下迎风面与侧风面罐壁的应力与变形结果,以及储液对储罐抗风性能的影响。结果表明:迎风面罐壁受风压力作用,罐壁内凹,侧风面罐壁受风吸力影响,罐壁外凸;风荷载对空罐影响较大,抗风结构可以有效地减弱空罐状态下罐壁顶部的变形;充液状态下,风荷载对罐壁的作用效果不明显,在储液压力作用下罐壁最容易破坏的位置出现在距离罐底高度2.42 m处。

央企智库数智化能力建设探索

[目的/意义]数字经济已经成为经济社会发展的新范式。中央企业智库(央企智库)作为中央企业智力资源的重要载体,亟需提升数智化能力,以适应数字化时代信息环境、知识生产及决策支持的新要求。[方法/过程]基于对国内外数字化建设领先的智库的访谈调研和天翼智库能力建设的实践探索,本文从央企智库的定位和研究人员对数智化能力的核心需求出发,分析了央企智库数智化能力建设的必要性,并提出建设目标和规划框架,同时,探索性研究了类ChatGPT人工智能技术赋能智慧决策的主要场景和落地模式,总结提炼了央企智库能力建设和持续运营的关键要素。[结果/结论]央企智库数智化能力建设需要以用户为中心,以需求和问题为导向,充分利用人工智能等数字技术,构建以数据为基础、以知识为核心、以服务为宗旨的数智化智库能力平台,同时还需要加强组织和机制建设,以保障央企智库可持续发展。这将有助于智库整合优势资源,提升智慧决策支持能力和水平。

车载液氢瓶不同局部大热流位置对自增压规律影响研究

液氢因储氢密度高、安全性能好等优势,在氢能汽车领域受到了人们的重点关注,尤其在长距离、大规模运输过程应用。车载液氢瓶作为液氢燃料车的核心部件之一,其无损储存时间将直接影响整车的续驶里程。在车载液氢瓶管路结构设计中,管路与内容器连接处会存在较大的局部热流,其会对液氢瓶无损储存时间产生显著影响。通过建立三维数值模型,在总漏热量相同的前提下,研究了顶部、中间、底部三种局部大热流位置和均匀漏热条件对液氢瓶自增压过程中热物理场变化规律的影响。研究结果表明:均匀漏热和顶部、中间、底部三种局部大热流工况在1000 s内的平均增压速率分别为4.51、3.01、15.08和6.08 kPa·h^(-1)。由于顶部大热流工况下的增压速率最慢,中间大热流工况下的增压速率最快,因此在设计管路与内容器连接口位置时建议将连接位置设置于内容器顶部,以延长液氢瓶的无损储存时间。

航油储罐珊瑚砂地基变形特性研究

珊瑚砂广泛应用于岛礁吹填工程中,其与陆源砂的物理力学性质截然不同。为探究吹填珊瑚砂地基变形机制,对珊瑚砂开展了级配、孔隙比和加载方式等因素耦合作用下的侧限压缩试验。珊瑚砂的初始颗粒级配对压缩变形特性影响较大,且颗粒破碎明显。砾砂的初始孔隙比越大压缩性也越大,珊瑚砂的变形主要由孔隙的移动填充为主,伴有少量的颗粒破碎,均为不可恢复的塑性变形,因此,珊瑚砂的回弹指数仅为黏土的1/10。运用Plaxis 3D软件建立了航油储罐的三维模型,基于室内试验获得的力学参数,研究了航油储罐工程珊瑚砂地基在加卸载循环荷载作用下的变形规律,并与马尔代夫易卜拉欣·纳西尔国际机场的航油储罐工程实测数据进行了对比,验证了该模型的准确性。在航油储罐的最大储油量下,珊瑚砂地基达到最大变形量。在该荷载水平下,多次加卸载不会导致变形进一步发展。研究成果对工程安全控制有一定的指导意义。

大型储液罐内外基础环墙抗不均匀沉降性能分析

大型储液罐对地基沉降变形非常敏感,需要采用基础环梁来防止其对上部结构的危害,因此,基础环梁设计是大型储罐建设的重要一环。本文采用有限元软件对大型储罐-基础环梁-地基土层的共同作用进行了数值模拟,主要考察了大型储油罐基础环墙环向拉力的分布,探讨了影响环墙受力的主要因素。研究表明,垫层参数对环墙环向拉力的影响较大,压缩性低,抗剪强度大并经过压实处理的垫层材料对应的环墙环向拉力最小,环墙环向拉力随环墙半径的增大先近似线性增加而后略微减小。

大型LNG储罐预冷模型构建和预冷参数计算

预冷作业是大型液化天然气(Liquified Natural Gas, LNG)储罐投用前最关键的环节。预冷介质用量、预冷时间以及储罐各部分构件降温速率的控制是大型LNG储罐预冷作业得以顺利进行的重要保证。依托某大型LNG接收站项目,旨在较精确地计算预冷介质用量。选取最复杂的大型LNG储罐为研究主体,综合考虑保冷材料比热容变化、储罐日常蒸发、预冷介质输送管道漏热等因素,搭建有限元模型进行数值模拟计算,并利用上述结果计算预冷模型中的参数。预冷模型计算结果表明:大型LNG储罐预冷工作实施过程中,提高预冷降温速率可减少预冷介质用量和预冷时间,同时降低大型LNG储罐漏热所消耗的预冷介质占比,但需要注意储罐内元件的温差;考虑输送管线和机械结构漏热,预冷介质用量增多,与现场实际数据更吻合,相对误差不超过5%。研究结果对指导大型LNG储罐预冷操作具有参考价值。

汽车空调鼓风机左右盖复杂抽芯注塑模设计

根据汽车空调鼓风机左右盖结构特点设计了一副大型、复杂侧向抽芯注塑模具。模具采用热流道浇注系统以及快速和均衡的冷却系统,成型周期缩短了10%,精度提高了一级,达到了MT3级(GB/T 14486—2008)。模具通过采用复合抽芯和延时抽芯有效解决了成型塑件结构复杂、倒扣多的脱模难题。模具导向定位系统采用标准滚珠导套,大大提高了模具的精度和寿命。

大型锻压设备的液压系统设计

本文结合锻压设备的特点及锻压设备的发展,对锻压设备的液压系统设计流程进行了简单的介绍。并以一种典型的大型液压系统为例,对液压分配系统、液压泵站的设计进行了阐述。其中,由于各手册、文献中对液压系统油箱强度设计方面的介绍较少,本文基于有限元分析的方法,研制了50000L大型液压站。该液压系统及液压站经测试、使用,性能符合使用要求。

大型石油储罐主动安全防护技术的应用探析

大型石油储罐浮顶密闭空间属于密封环形油气积聚空间,收发油作业时浮盘升降会积聚大量挥发可燃气体,当浓度超出爆炸极限时,遇到静电、雷击产生的火花就极易引发燃烧或爆炸事故。基于此,通过提出一种混合气体实时监测与惰化技术,在储罐浮顶处安装混合气体探测与保护系统,及时注入氮气类惰性气体降低可燃气体浓度,保障安全生产。通过测试应用,该项技术实用效果较好。