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An analysis of the chaotic motion of particles of different sizes in a gas fluidized bed

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Particuology 2008年第6期6卷 549-556页

作者： Y.Q. Feng A.B. Yu lab for simulation and Modelling of particulate systems School of Materials Science and Engineering University of New South Wales Sydney NSW 2052 Australia

The dynamic behavior of individual particles during the mixing/segregation process of particle mixtures in a gas fluidized bed is analyzed. The analysis is based on the results generated from discrete particle simulation, with the focus on the trajectory of and forces acting on individual particles. Typical particles are selected representing three kinds of particle motion： a flotsam particle which is initially at the bottom part of the bed and finally fluidized at the top part of the bed; a jetsam particle which is initially at the top part of the bed and finally stays in the bottom de-fluidized layer of the bed; and a jetsam particle which is intermittently joining the top fluidized and bottom de-fluidized layers. The results show that the motion of a particle is chaotic at macroscopic or global scale, but can be well explained at a microscopic scale in terms of its interaction forces and contact conditions with other particles, particle-fluid interaction force, and local flow structure. They also highlight the need for establishing a suitable method to link the information generated and modeled at different time and length scales.

关键词： Fluidization Segregation Discrete particle simulation Granular dynamics

DEM simulation of particle percolation in a packed bed

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Particuology 2008年第6期6卷 475-482页

作者： Mahbubur Rahman Haiping Zhu Aibing Yu John Bridgwater lab for simulation and modeling of particulate systems School of Materials Science and Engineering The University of New South Wales Sydney NSW 2052 Australia Department of Chemical Engineering University of Cambridge Cambridge CB2 3RA UK

The phenomenon of spontaneous particle percolation under gravity is investigated by means of the discrete element method. Percolation behaviors such as percolation velocity, residence time distribution and radial dispersion are examined under various conditions. It is shown that the vertical velocity of a percolating particle moving down through a packing of larger particles decreases with increasing the restitution coefficient between particles and diameter ratio of the percolating to packing particles. With the increase of the restitution coefficient, the residence time and radial dispersion of the percolating particles increase. The packing height affects the residence time and radial dispersion. But, the effect can be eliminated in the analysis of the residence time and radial dispersion when they are normalized by the average residence time and the product of the packing height and packing particle diameter, respectively. In addition, the percolation velocity is shown to be related to the vertical acceleration of the percolating particle when an extra constant vertical force is applied. Increasing the feeding rate of percolating particles decreases the dispersion coefficient.

关键词： Discrete element method Particle percolation Residence time Radial dispersion

Mixing of particles and powders:Where next?

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Particuology 2010年第6期8卷 563-567页

作者： John Bridgwater University of Cambridge Department of Chemical Engineering and BiotechnologyCambridge CB2 3RAUK laboratory for simulation and modeling of particulate systems School of Materials Science and EngineeringUniversity of New South WalesSydneyNSW 2052Australia

Industrial mixers for powders and granular materials operate with no effective control of mixture quality and lack scientific design. The last twenty years have seen growth in understanding of mixing and mixers. However, research falls far short of what is needed for on-line characterisation of mixture quality. Secondly, although theoretical descriptions of a few mixer types have been reported, these fall far short of what is needed for equipment design. Two thrusts could revolutionise this situation. One is a scientific characterisation of mixer structure applicable to industrial scale as well as laboratory scale equipment; this is now within our grasp using digital imaging. The other is the development of ideas to overcome the restricted number of particles that can be used in the Distinct Element Method （DEM） for mixers. The goal should be to take the designer through a sequence of steps to the most appropriate mixer size, configuration and operating conditions for a given process duty.

关键词： Design Granular materials Mixing Mixers Powders Quality characterisation Quality measurement

Mixing of powders and granular materials by mechanical means——A perspective

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Particuology 2012年第4期10卷 397-427页

作者： John Bridgwater Department of Chemical Engineering and Biotechnology University of CambridgePembroke StreetCambridge CB2 3RAUK laboratory for simulation and modeling of particulate systems School of Materials Science and EngineeringThe University of New South WalesSydneyNSW 2052Australia

When engineers and scientists encounter the mixing of powders, they enter a subject where it is often difficult to find bearings. This perspective seeks to address this need by setting out the state of prac- tice. It then considers the growing momentum in the area following advances in computation and in measurement that became significant in the 1990s. The mixing of powders and granular materials is of central importance for the quality and performance of a wide range of products. However, process design and operation are very difficult, being largely based on judgement rather than science. There are not even tabulated data to tell how the quality of mixtures depends on mixer selection. Design depends on experience and insight, not science. There are no sound scale-up laws for a given equipment type, largely because particle size needs to be included in any dimensional analysis. Design is not possible by applying physical principles. There is no reliable equation to describe the flow of single component powders, let alone multi-component mixtures. In most cases, measurement has been difficult because the materials are optically opaque. Work in the research literature has been questionable because the results obtained for mixture sampling are affected by sample size. Recently, modern experimental techniques and modelling work have provided a good deal of infor- mation on the behaviour of many of the pieces of equipment, though these have been small in size and often confined to materials of a single size. However, the studies have enhanced knowledge of physical behaviour. For example, for a wide range of equipment when operating at lower velocities, mixing is determined by the number of revolutions of the mixer, not the time. Observations of flow structure have led to a few specific models that should scale with equipment size. Measurement techniques are slowly becoming more effective in giving internal flow patterns and in measuring powder composition. For cohe

关键词： PerspectivePowder mixingMixing of granular materialsCurrent designMixture qualityMixing mechanismsExperiments and computationsResearch trendsOpportunities for advanceSegregationCohesion

An Adaptive Data-driven Method Based on Fuzzy Logic for Determining Power System Voltage Status

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Journal of Modern Power systems and Clean Energy 2024年第3期12卷 707-718页

作者： Sirwan Shazdeh Hêmin Golpîra Hassan Bevrani the SMGRC University of KurdistanSanandajIran Power systems modeling&simulation lab Department of Electrical EngineeringUniversity of KurdistanKurdistanSanandaj 66177-15175Iran

This paper proposes an adaptive method based on fuzzy logic that utilizes data from phasor measurement units(PMUs) to assess and classify generating-side voltage trajectories. The voltage variable and its associated derivatives are used as the input variables of a fuzzy-logic block. In addition, the voltage trajectory is compared with the pre-selected pilot-bus voltage to make a reliable decision about the voltage operational state. Different types of short-term voltage dynamics are considered in the proposed method. The fuzzy membership functions are determined using a systematic method that considers the current situation of the voltage trajectory. Finally, the voltage status is categorized into four classes to determine appropriate remedial actions. The proposed method is validated on a IEEE 73-bus power system in a MATlab environment.

关键词： Fuzzy logic fault-induced delayed voltage recovery phasor measurement unit(PMU) short-term voltage stability situational awareness voltage classification

A FEniCS implementation of the phase field method for quasi-static brittle fracture

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Frontiers of Structural and Civil Engineering 2019年第2期13卷 380-396页

作者： HIRSHIKESH Sundararajan NATARAJAN Ratna Kumar ANNABATTULA Integrated modeling and simulation lab Department of Mechanical EngineeringIndian Institute of Technology MadrasChennai- 600036India

In the recent years, the phase field method for simulating fracture problems has received considerable attention. This is due to the salient features of the method: 1) it can be incorporated into any conventional finite element software;2) has a scalar damage variable is used to represent the discontinuous surface implicitly and 3) the crack initiation and subsequent propagation and branching are treated with less complexity. Within this framework, the linear momentum equations are coupled with the diffusion type equation, which describes the evolution of the damage variable. The coupled nonlinear system of partial differential equations are solved in a 'staggered? approach. The present work discusses the implementation of the phase field method for brittle fracture within the open-source finite element software, FEniCS. The FEniCS provides a framework for the automated solutions of the partial differential equations. The details of the implementation which forms the core of the analysis are presented. The implementation is validated by solving a few benchmark problems and comparing the results with the open literature.

关键词： phase field method FEniCS brittle fracture crack propagation variational theory of fracture

Discrete Particle simulation of Gas-Solid Flow in Air-Blowing Seed Metering Device

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Computer modeling in Engineering & Sciences 2021年第6期127卷 1119-1132页

作者： Zhengquan Li Pei Zhang Yongchang Sun Chenglin Zheng Liang Xu Dianyu E Jiangxi Provincial Key laboratory for simulation and Modelling of particulate systems Jiangxi University of Science&TechnologyGanzhou341000China Energy Materials Computing Center Jiangxi University of Science&TechnologyNanchang330013China

In this paper,the gas and seed flow characters in the air-blowing seed metering device are investigated by using the coupled computational fluid dynamics and discrete element method(CFD-DEM)in three dimensions(3D).The method of establishing boundary model based on the computer-aided design(CAD)drawing,has been used to build the boundary model of seed metering *** 3D laser scanning technique and multi-element method are adopted to establish the particle *** a combined numerical and experimental effort,using 3D CFD-DEM software,which is based on the in-house codes,the mechanisms governing the gas and solid dynamic behaviors in the seed metering device have been *** gas velocity field and the effect of different rotational speeds and air pressures on the seeding performance and particle velocity have been studied,similar agreements between numerical and experimental results are *** reveals that the 3D CFD-DEM model established is able to predict the performance of the air-blowing seed metering *** can be used to design and optimize the air-blowing seed metering device and other similar agriculture devices.

关键词： Seed metering device CFD-DEM CAD simulation gas-solid flow

Recent advances on smart grid technology and renewable energy integration

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Science China(Technological Sciences) 2013年第12期56卷 3040-3048页

作者： MEI ShengWei CHEN LaiJun State Key lab of Control and simulation of Power systems and Generation Equipments (Dept. of Electrical Engineering Tsinghua University)

With the integration of renewable energy generations and other related changes,the smart grid,or the future electric power system,is confronted with new challenges and ***,it is a promising subject in electrical engineering and much work has been done on *** paper reviews the recent advances on the technologies of smart grid and renewable energy integration,from the aspects of modeling,simulation,protection and control,stability,operation,and planning.

关键词： smart grid renewable energy integration modeling simulation protection and control stability operation planning

A novel method for modeling the phase change of iron ore particles in the cohesive zone of a blast furnace

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Particuology 2024年第3期86卷 252-261页

作者： Dianyu E Yingming Wen Jiayun Dan Youyuan Jiang Guangchao Wei Jiaxin Cui Jiangxi Provincial Key laboratory for simulation and Modelling of particulate systems Jiangxi University of Science and TechnologyNanchang330013China International Institute for Innovation Jiangxi University of Science and TechnologyNanchang330013China Ironmaking Plant Xiangtan Iron and Steel Corporation of Hunan HualingXiangtan411101China Schoolof Transportation and Vehicle Enginering Shandong University of TechnologyZibo255000China

Cohesive zone plays a vital role in the stable operation of a blast furnace(BF),yet the complex phase change process of iron ore particles in this zone is still not well *** this study,a novel one-dimensional(1D)unsteady phase change model was developed to elucidate the heat transfer and melting mechanisms of iron ore *** model validation,the effects of several key operating parameters(e.g.,particle diameter,gas velocity,initial temperature)on the phase change behavior of iron ore particles were analyzed,and the joint effect of multiple parameters was *** results show that larger-sized iron ore particles possess lower specific surface areas,which in turn reduces their convective heat absorption ***,the distance from the solid-liquid phase interface to the particle surface increases,thereby slowing down the movement of the phase interface and pro-longing the melting duration of the *** the gas velocity and the initial temperature does not have a significant impact on reducing the duration of the complete melting *** the specified conditions,it is observed that increasing the gas velocity by 3-fold and 9-fold results in a reduction of the melting duration by 2.4%and 8.3%,*** the initial temperature of iron ore particles results in a decrease in the core-to-surface temperature difference,a slower heating rate,and a shorter duration to achieve *** the factors affecting the melting process,the particle diameter is found to be the most significant in terms of the liquid phase precipitation,mushy zone thickness,and core-to-surface temperature difference of iron ore particles.

关键词： Blast furnace Iron ore melting Cohesive zone Heat transfer Phase change