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CFD simulation of internal-loop airlift reactor using EMMS drag model

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Particuology 2015年第2期13卷 124-132页

作者： Tingting Xu Xuedong Jiang Ning Yang Jiahua Zhu State Key Laboratory of Multi-Phase Complex Systems Institute of Process EngineeringChinese Academy of Sciences University of Chinese Academy of Sciences Department of Chemical engineering Xi'an Jiaotong University School of Chemical engineering Sichuan University

The simulation of internal-loop airlift reactors is challenging because complex meso-scale structures exist in different sections of the reactor, separated by the draft tube. This paper reports on the computational fluid dynamics （CFD） simulation of internal-loop airlift reactors using a new drag model derived from the dual-bubble-size （DBS） model, an extended energy-minimization multi-scale （EMMS） approach for gas-liquid flows. Compared with the traditional Schiller-Naumann （S-N） correlation, the new model improves the simulation of gas holdup in the riser and downcomer significantly. In particular, gas holdup and circulation of two-phase flow can be modeled successfully using the new model, whereas traditional drag models such as the S-N correlation show an absence of gas in the downcomer. The simulation demonstrates the advantage and potential of this new model for internal-loop airlift reactors.

关键词： Computational fluid dynamics Internal-loop Airlift Multi-scale Multiphase flow Hydrodynamics

Microstructure Manipulation of Covalent Organic Frameworks(COFs)-based Membrane for Efficient Separations

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Chemical Research in Chinese Universities 2022年第2期38卷 325-338页

作者： MA Hanze WANG Shaoyu REN Yanxiong LIANG Xu WANG Yuhan ZHU Ziting HE Guangwei JIANG Zhongyi Key Laboratory for Green Chemical Technology of Ministry of Education School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300350P.R.China Collaborative Innovation Center of Chemical Science and engineering(Tianjin) Tianjin 300072P.R.China Joint School of National University of Singapore and Tianjin University International Campus of Tianjin UniversityFuzhou 350207P.R.China

Covalent organic framework(COF) membranes have exhibited great potential to become the next-generation membranes for efficient separations due to the diverse structures, ordered framework pores, tunable functionality and excellent stability. This review presents the microstructure manipulation strategies for separation performance enhancement of COF membranes in recent years. Based on the three mechanisms of molecular sieving, surface diffusion, and facilitated transport, the structural modulation methods to enhance the selectivity of COF membranes are analyzed in detail. Next, strategies of realizing ultrashort mass transfer pathways and ultralow mass transfer resistance for the permeability enhancement are elaborated. Furthermore, the framework stability in COFs, interlayer stability between COF nanosheets and interfacial stability between COF layer and substrate are discussed. Finally, we discuss the existing challenges and perspectives on the future development of COF membranes, targeting at identifying the most promising strategies and directions for the engineering of COF membranes.

关键词： Covalent organic framework Organic molecular sieve membrane Membrane separation Microporous material

Evaluation of natural forest regeneration as a part of land restoration in the Khentii massif,Mongolia

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Journal of Forestry Research 2020年第5期31卷 1773-1786页

作者： David Juricka Antonın Kusbach Jana Parılkova Jakub Houska Pavlına Ambrozova Vaclav Pecina Zdena Rosicka Martin Brtnicky Jindrich Kynicky Department of Geology and Pedology Faculty of Forestry and Wood TechnologyMendel UniversityZemedelska 161300 BrnoCzech Republic Department of Forest Botany Dendrology and GeobiocoenologyFaculty of Forestry and Wood TechnologyMendel UniversityZemedelska161300 BrnoCzech Republic Faculty of Civil engineering Institute of Water StructuresBrno University of TechnologyZizkova 1760200 BrnoCzech Republic Central European Institute of Technology Brno University of TechnologyPurkynova 656/12361200 BrnoCzech Republic

Forest stands in the semi-arid environment of northern Mongolia have an essential role in controlling ongoing desertification in the surrounding *** the last decade,the total forest area has decreased *** aim of this study was to evaluate the potential of natural regeneration as an essential element for ensuring sustainability of these *** on field measurements from 120 plots in six sites,our assessment tool revealed five qualitative categories of forest regeneration,allowing us to assess impacts of both grazing and environmental conditions on the regeneration *** is a crucial factor and adversely affects *** sites with relatively low grazing intensity,low soil moisture levels represent the main reason for reduced *** approach to classification proposed in this study allows for the identification and interpretation of stand conditions where natural regeneration has *** study provides an important foundation to inform decisionmaking related to land protection and restoration *** findings could be used in comparative studies and,importantly,may aid further mapping of Mongolian forests.

关键词： Mongolia Natural forest regeneration Seedlings Larix sibirica Land restoration Desertification

A transient fiuid–structure interaction analysis strategy and validation of a pressurized reactor with regard to loss-ofcoolant accidents

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Nuclear Science and Techniques 2020年第6期31卷 11-21页

作者： Ying-Chao Ma Xie-Lin Zhao Xian-Hui Ye Nai-Bin Jiang Jin-Xiong Zhou State Key Laboratory for Strength and Vibration of Mechanical structures School of AerospaceXi’an Jiaotong UniversityXi’an 710049China Key Laboratory of Nuclear Reactor System Design Technology Nuclear Power Institute of ChinaChengdu 610200China Sino-French Institute of Nuclear engineering and Technology Sun Yat-Sen UniversityZhuhai 519082China

A loss-of-coolant accident(LOCA)is one of the basic design considerations for nuclear reactor safety analysis.A LOCA induces propagation of a depressurization wave in the coolant,exerting hydrodynamic forces on structures viafiuid–structure interaction(FSI).The analysis of hydrodynamic forces on the core structures during a LOCA process is *** describe the implementation of a numerical strategy for prestressed *** consists of an initialization and a restarted transient analysis process,all implemented via the ANSYS Workbench by system coupling of ANSYS and *** strategy is validated by making extensive comparisons of the pressures,displacements,and strains on various locations between the simulation and reported *** approach is appealing for dynamic analysis of other prestressed structures,owing to the good popularity and acknowledgement of ANSYS and Fluent in both academia and industry.

关键词： Loss-of-coolant accident(LOCA) Fluid–structure interaction(FSI) Finite element method Prestressed structure Structural dynamics

Interaction Between Large-scale Vortex Structure and Dispersed Particles in a Three Dimensional Mixing Layer

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Chinese Journal of Chemical engineering 2003年第4期11卷 377-382页

作者：罗坤郑友取樊建人岑可法 Institute for Thermal Power engineering Zhejiang University Hangzhou 310027 China Department of Mechanical engineering Zhejiang University of Science and Technology Hangzhou 310012 China Institute for Thermal Power engineering Zhejiang UniversityHangzhou 310027 China

In order to understand the interaction between large-scale vortex structure and particles, a two-way coupling temporal mixing layer laden with particles at a Stokes number of 5 with different mass loading planted initially in the upper half region is numerically studied. The pseudospectral method is used for the flow fluid and the Lagrangian approach is employed to trace particles. The momentum coupling effect introduced by a particle is approximated to a point force. The simulation results show that the coherent structures are still dominant in the mixing layer, but the large-scale vortex structure and particle dispersion are modulated. The length of large-scale vortex structure is shortened and the pairing is delayed. At the same time, the particles are distributed more evenly in the whole flow field as the mass loading is increased, but the particle dispersion along the transverse direction differs from that along the spanwise direction, which indicates that the effect by the addition of particle on the suanwise large-scale vortex structure is different from the streamwise counterpart.

关键词：三维混合层大涡结构颗料扩散相互作用流体运动

Hierarchically Porous Carbon Membranes Derived from PAN and Their Selective Adsorption of Organic Dyes

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Chinese Journal of Polymer Science 2016年第1期34卷 23-33页

作者：吴青芸 Hong-qing Liang Meng Li Bo-tong Liu 徐志康 Department of Polymer Science and engineering Faculty of MaterialsScience and Chemical EngineeringNingbo UniversityNingbo 315211China MOE Key Laboratory of Macromolecular Synthesis andFunctionalization Department of Polymer Science and EngineeringZhejiang UniversityHangzhou 310027China

Porous carbon membranes were favorably fabricated through the pyrolysis of polyacrylonitrile（PAN） precursors, which were prepared with a template-free technique-thermally induced phase separation. These carbon membranes possess hierarchical pores, including cellular macropores across the whole membranes and much small pores in the matrix as well as on the pore walls. Nitrogen adsorption indicates micropores（1.47 and 1.84 nm） and mesopores（2.21 nm） exist inside the carbon membranes, resulting in their specific surface area as large as 1062 m2/g. The carbon membranes were used to adsorb organic dyes（methyl orange, Congo red, and rhodamine B） from aqueous solutions based on their advantages of hierarchical pore structures and large specific surface area. It is particularly noteworthy that the membranes present a selective adsorption towards methyl orange, whose molecular size（1.2 nm） is smaller than those of Congo red（2.3 nm） and rhodamine B（1.8 nm）. This attractive result can be attributed to the steric structure matching between the molecular size and the pore size, rather than electrostatic attraction. Furthermore, the used carbon membranes can be easily regenerated by hydrochloric acid, and their recovery adsorption ratio maintains above 90% even in the third cycle. This work may provide a new route for carbon-based adsorbents with hierarchical pores via a template-free approach, which could be promisingly applied to selectively remove dye contaminants in aqueous effluents.

关键词： Carbon membranes Polyacrylonitrile Thermally induced phase separation Methyl orange Selective adsorption

Analysing the structure of the optical path length of a supersonic mixing layer by using wavelet methods

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Chinese Physics B 2012年第6期21卷 344-351页

作者：高穹易仕和姜宗福赵玉新谢文科 College of Photon-Electron Science and engineering National University of Defense Technology College of Aerospace and Material engineering National University of Defense Technology

The nano-particle-based planar laser scattering （NPLS） technique is used to measure the density distribution in the supersonic mixing layer of the convective Mach number 0.12, and the optical path difference （OPL）, which is quite crucial for the study of aero-optics, is obtained by post processing. Based on the high spatiotemporal resolutions of the NPLS, the structure of the OPL is ana]ysed using wavelet methods. The coherent structures of the OPL are extracted using three methods, including the methods of thresholding the coefficients of the orthogonal wavelet transform and the wavelet packet transform, and preserving a number of wavelet packet coefficients with the largest amplitudes determined by the entropy dimension. Their performances are compared, and the method using the wavelet packet is the best. Based on the viewpoint of multifractals, we study the OPL by the wavelet transform maxima method （WTMM）, and the result indicates that its scaling behaviour is evident.

关键词： optical path difference aero-optics supersonic mixing layer wavelet coherent struc-tures scaling behavior

Corrosion mechanism of Mg alloys involving elongated long-period stacking ordered phase and intragranular lamellar structure

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Journal of Materials Science & Technology 2023年第20期151卷 190-203页

作者： Jinshu Xie Jinghuai Zhang Zhi Zhang Zijian Yu Zhihao Xu Ru Wang Daqing Fang Xiaobo Zhang Xiaoru Zhang Ruizhi Wu Key Laboratory of Superlight Material and Surface Technology Ministry of EducationCollege of Materials Science and Chemical EngineeringHarbin Engineering UniversityHarbin 150001China Faculty of Materials and Manufacturing Beijing University of TechnologyBeijing 100124China State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology Nanjing Institute of TechnologyNanjing 211167China

It is a long-term challenge to further improve the corrosion resistance while ensuring the strength of magnesium(Mg)*** the effect of potential fluctuation on the micro-galvanic corrosion and the subsequent film formation is important for understanding the corrosion mechanism of Mg alloys with multiple strengthening phases/***,we prepared the high-strength Mg-14.4Er-1.44Zn-0.3Zr(wt.%)alloys containing hybrid structures,i.e.,elongated long-period stacking ordered(LPSO)blocks+intragranular stacking faults(SFs)/LPSO *** Mg alloy with elongated LPSO blocks and intragranular LPSO lamellae(EZ-500 alloy)obtains good corrosion resistance(2.2 mm y^(–1)),while the Mg alloy containing elongated LPSO blocks and intragranular SFs(EZ-400 alloy)shows a significantly higher corrosion rate(6.9 mm y^(–1)).The results of scanning Kelvin probe force microscopy(SKPFM)show the elongated LPSO blocks act as cathode phase(87 mV in EZ-400 alloy),and the SFs serve as the weak anode(30 mV in EZ-400 alloy),resulting in high potential fluctuation in EZ-400 *** the contrary,both elongated blocks and intragranular lamellae are cathodic LPSO phase(67–69 mV)in EZ-500 alloy,leading to a lower potential *** in-situ atomic force microscope(AFM)observation indicates that high potential fluctuation would cause strong micro-galvanic corrosion,and subsequently leads to the failure in rapid formation of corrosion film,finally forming a loose and porous film,while relatively low potential fluctuation could result in more uniform corrosion mode and facilitate the rapid formation of protective ***,we propose that it is an effective way to develop high-strength corrosionresistant Mg alloys by controlling the potential fluctuation to form a“uniform potential”strengthening microstructure。

关键词： Mg alloys Stacking faults LPSO phase SKPFM Quasi in-situ AFM Corrosion behavior Potential fluctuation

Practical considerations of Si-based anodes for lithiumion battery applications

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Nano Research 2017年第12期10卷 3970-4002页

作者： Jaegeon Ryu Dongki Hong Hyun-Wook Lee Soojin Park Department of Energy engineering School of Energy and Chemical Engineering Ulsan National Institute of Science and Technology (UNIST) Ulsan 44919 Republic of Korea

Using Si-based anodes in Li-ion batteries is one of the most feasible approaches to achieve high energy densities despite their disadvantages, such as low conductivity and massive volume expansion, which cause unstable solid electrolyte interphase layers with mechanical failure. The forefront in research and development to address the above challenges suggests the possibility of fully commercially viable cells using various structural and interfacial modifications. In particular, we present a discussion of each dimension of Si-based anodes in multiple controlled systems, including plain, hollow, porous, and uniquely engineered structures, which are further evaluated based on their anode performances, such as initial reversibility, capacity retention for extended cycles with its efficiency, degree of volume expansion tolerance, and rate capabilities, by several practical standards in half cells. With these practical considerations, multi-dimensional structures with uniform size distributions （micrometers, on average） are strongly desired to satisfy the rigorous requirements for widespread applications. Furthermore, we closely examined several full cells composed of Si-based multicomponent anodes coupled with suitable cathodes based on practical standards to propose future research directions for Si-based anodes to keep pace with the rapidly changing market demands for diverse energy storage systems.

关键词： silicon anode dimensional control full celllithium-ion batteries practicality