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作者： Jayasundara, C.T. Yang, R.Y. Yu, A.B. Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering University of New South Wales Sydney NSW 2052 Australia

Particle flow in a stirred mill was modeled using discrete element method, focusing on the effect of mill properties and stirrer configurations, such as particle-wall friction, the size of disc holes, distance between stirrers, and stirrer shape, on the flow properties of grinding media. The flow properties were analyzed in terms of velocity field, porosity distribution, collision frequency, collision energy, impact energy, and power draw. The results indicate that although particle-wall sliding friction coefficient affects the energy transfer from discs to particles, too high a sliding friction may lead to a decrease in energy efficiency. The distance between discs significantly affects the circulation of grinding media between discs. Among the different stirrer types considered, energy transfer is more effective when disc holes are present. Pin stirrer shows increased grinding rates which also results in relatively high power consumption. Although different collision environments exist with different stirrer types, it is shown that the grinding rate can be determined by the first-order kinetics where the rate constant is dependent on the impact energy, for a given material. Grinding efficiency has been compared for different grinding materials under different operating conditions. The results suggest that selection of stirrer geometry also depends on the feed size and the type of material to be ground. Discussion has also been made of the usefulness of particle scale information in the design and control of stirred mills of different types. © 2011 American Chemical Society.

关键词： Grinding (machining)

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Effect of the size of media on grinding performance in stirred mills

Effect of the size of media on grinding performance in stirr...

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This work investigated the effect of grinding medium size on the wet milling performance in stirred mills using a combined numerical and experimental approach. Physical experiments were performed in a 1.4L stirred mill with the discs rotating at different speeds to grind aluminium hydroxide powders with different sized glass beads. The results showed that the grinding process followed the first order kinetics and the grinding rate increased with increasing disc speeds. While 4 mm glass beads had slightly larger grinding rates than 2 mm and 6 mm glass beads, the differences were generally within 5%, indicating their weak dependence. On the other hand, the energy consumption increased significantly for the large grinding media. simulations based on the combined discrete element method (DEM) and computational fluid dynamics (CFD) approach were performed under similar conditions. The simulated flow patterns and power draws were comparable to those measured. The total impact energy, which is the summation of all collision energy, had a unified power law relationship with the grinding rate for all grinding conditions. It is expected that the ratio of total impact energy and input power, which decreased for larger grinding media in the present study, can be used to describe the grinding efficiency. © 2011 Elsevier Ltd. All rights reserved.

关键词： Computational fluid dynamics

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modelling in-furnace phenomena of pulverized coal injection in ironmaking blast furnace: Effect of coke bed porosities

Modelling in-furnace phenomena of pulverized coal injection ...

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作者： Shen, Yansong Yu, Aibing Austin, Peter Zulli, Paul Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering University of New South Wales Sydney NSW 2052 Australia BlueScope Steel Research P.O. Box 202 Port Kembla NSW 2505 Australia

In order to understand the complicated in-furnace phenomena of pulverized coal injection in ironmaking blast furnaces, a three-dimensional CFD model has been developed to simulate the gas-particle behaviors in not only raceway cavity but also the surrounding coke packed bed under practical conditions. The model considers two different fuels, pulverized coal and coke bed. The model is validated against the measurements in terms of coal burnout and gas composition, respectively. The typical in-furnace phenomena are simulated. Then an array of parametric study is carried out to evaluate the effects of local porosities of different coke bed zones. The qualitative and quantitative analysis is conducted. The results indicate that the local porosities of different coke bed zones can affect the coal burnout and gas composition differently: significantly in the deadman zone but insensitive in the dripping zone. In addition, the present model is able to provide a more reliable indicator to describe coal burnout, i.e. burnout over raceway surface, rather than burnout only along the centerline. The model is expected to be useful for understanding the flow-thermo-chemical behaviors and then optimizing the PCI operation in full-scale blast furnaces. © 2011 Elsevier Ltd. All rights reserved.

关键词： Computational fluid dynamics

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Particle scale modelling of the multiphase flow in a dense medium cyclone: Effect of fluctuation of solids flowrate

Particle scale modelling of the multiphase flow in a dense m...

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作者： Chu, K.W. Kuang, S.B. Yu, A.B. Vince, A. Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering University of New South Wales Sydney NSW 2052 Australia Elsa Consulting Group Pty. Ltd. PO Box 8100 Mt. Pleasant QLD 4740 Australia

Dense medium cyclone (DMC) is widely used to upgrade run-of-mine coal in the coal industry. The flow dynamics/fluctuation in a DMC is important but has not been studied previously. In this work, the dynamics is studied by numerically with special reference to the effect of the fluctuation of solid mass flowrate. The simulation is carried out by use of a combined approach of Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM). In the model, the motion of discrete mineral particle phase is obtained by DEM which applies Newton's equations of motion to every individual particle and the flow of medium (mixture of water, air and fine magnetites) phase by the traditional CFD which solves the Navier-Stokes equations at a computational cell scale. The simulated results are analysed in terms of medium and coal flow patterns, and particle-fluid, particle-particle and particle-wall interaction forces. It is shown that under high fluctuation frequency and current conditions, the performance of DMC is not sensitive to both the fluctuation amplitude and period of coal flow at the DMC inlet. However, under low fluctuation frequency, as fluctuation amplitude increases, the separation performance deteriorates slightly and the flow is obviously affected at the spigot. A notable finding is that the near-gravity particles that tend to reside at the spigot and/or have longer residence time in the DMC would be affected more than other particles. The work shows that this two-way coupled CFD-DEM model could be a useful tool to study the dynamics of the flow in DMCs. © 2011 Elsevier Ltd. All rights reserved.

关键词： Computational fluid dynamics

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Some Challenging Problems in Discrete Element modelling of particulate systems

Some Challenging Problems in Discrete Element Modelling of P...

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中国力学学会2012颗粒材料计算力学学术会议

作者： Yu Ai-Bing Laboratory for Simulation and Modelling of Particulate Systems (Simpas)School of Materials Science and Engineering The University of New South Wales Sydney NSW 2052 Australia

Particle science and technology is a rapidly developing interdisciplinary research area with its core being the understanding of the relationships between micro-and macro-scopic properties of particulate/granular matter-a state of matter that is widely encountered but poorly *** macroscopic behaviour of particulate matter is controlled by the interactions between individual particles as well as interactions with surrounding fluids and wall.

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Aggregation Kinetics of Inclusions in Swirling Flow Tundish for Continuous Casting

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Journal of Iron and Steel Research International 2010年第5期17卷 6-10页

作者： YUE Qiang ZOU Zong-shu HOU Qin-fu School of Materials and Metallurgy Northeastern University Shenyang 110004 Liaoning China Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering University of New South Wales Sydney NSW 2052 Australia

The mechanism of inclusion aggregation in liquid steel in swirling flow tundish is analyzed by applying the theory of flocculation which was developed in the field of colloid engineering. The gas bridge forces due to the micro bubbles on hydrophobic inclusion surfaces were responsible for the inclusion collision and agglomeration, which can avoid the aggregation to breakup. The quantity of micro bubbles on hydrophobic inclusion particle is more than that on hydrophilic one. The trend of forming gas bridges between micro bubbles on particles is strong in the course of collision. The liquid film on hydrophobic particles is easy to break during collision process. Hydrophobic particles are liable to aggregate in collision. According to the analysis of forces on a nonmetallic inclusion particle in swirling chamber, the chance of inclusion collision and aggregation can be improved by the centripetal force. Hydropbobic particles in water are liable to aggregate in collision. Hydrophilic particles in water are dispersed although collision happens. The wettability can be changed by changing solid-liquid interface tension. The nonmetallic inclusion removal in swirling flow tundish is studied. The result shows that under certain turbulent conditions, *** concentration and the wettability between particles and liquid steel are the main factors to induce collision and aggregation.

关键词： collision aggregation wettability inclusion swirling chamber continuous casting tundish

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State estimation for mobile robot using neural networks

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Journal of Applied Sciences 2009年第22期9卷 3957-3965页

作者： Chouraqui, S. Benyettou, M. Simulation and Modelling of Industrial Systems Laboratory Department of Computer Science Facultyty of Science University of Science and Technology of Oran Mohammed Boudiaf USTO P.O. Box 1505 El Menaour Oran Algeria

In this study, we describe a state estimation method using neural networks. The developed method has been applied to the problem of estimating the parameter of a six degree of freedom (DOF) PUMA 560 Robot arm manipulator. The results obtained were compared with the conventional Extended Kalman Filter, showing an improvement in performance and robustness. From the simulations performed, it can be said that the neural filter proposed for the studied application is more consisted and convergent than the EKF filter. © 2009 Asian Network for Scientific Information.

关键词： Neural networks

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Space mapping with adaptive response correction for microwave design optimization

Space mapping with adaptive response correction for microwav...

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作者： Koziel, Slawomir Bandler, John W. Madsen, Kaj School of Science and Engineering Reykjavík University Reykjavík IS-103 Iceland Simulation Optimization Systems Research Laboratory Department of Electrical and Computer Engineering McMaster University Hamilton ON L8S 4K1 Canada Bandler Corporation Dundas ON L9H 5E7 Canada Informatics and Mathematical Modelling Technical University of Denmark DK-2800 Lyngby Denmark

Output space mapping is a technique introduced to enhance the robustness of the space-mapping optimization process in case the space-mapped coarse model cannot provide sufficient matching with the fine model. The technique often works very well;however, in some cases it fails. Especially in the microwave area where the typical model response (e.g., |S21|) is a highly nonlinear function of the free parameter (e.g., frequency), the output spacemapping correction term may actually increase the mismatch between the surrogate and fine models for points other than the one at which the term was calculated, as in the surrogate model optimization process. In this paper, an adaptive response correction scheme is presented to work in conjunction with space-mapping optimization algorithms. This technique is designed to alleviate the difficulties of the standard output space mapping by adaptive adjustment of the response correction term according to the changes of the space-mapped coarse model response. Examples indicate the robustness of our approach. © 2009 IEEE.

关键词： Mapping

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Quality assessment of coarse models and surrogates for space mapping optimization

Quality assessment of coarse models and surrogates for space...

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作者： Koziel, Slawomir Bandler, John W. Madsen, Kaj Simulation Optimization Systems Research Laboratory Department of Electrical and Computer Engineering McMaster University Hamilton ON L8S 4K1 Canada Bandler Corporation Dundas ON L9H 5E7 Canada Informatics and Mathematical Modelling Technical University of Denmark Lyngby DK-2800 Denmark

One of the central issues in space mapping optimization is the quality of the underlying coarse models and surrogates. Whether a coarse model is sufficiently similar to the fine model may be critical to the performance of the space mapping optimization algorithm and a poor coarse model may result in lack of convergence. Although similarity requirements can be expressed with proper analytical conditions, it is difficult to verify such conditions beforehand for real-world engineering optimization problems. In this paper, we provide methods of assessing the quality of coarse/surrogate models. These methods can be used to predict whether a given model might be successfully used in space mapping optimization, to compare the quality of different coarse models, or to choose the proper type of space mapping which would be suitable to a given engineering design problem. Our quality estimation methods are derived from convergence results for space mapping algorithms. We provide illustrations and several practical application examples. © Springer Science+Business Media, LLC 2007.

关键词： Optimization

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Enhanced surrogate models for statistical design exploiting space mapping technology

Enhanced surrogate models for statistical design exploiting ...

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Microwave, MTT-S International Symposium

作者： S. Koziel J.W. Bandler A.S. Mohamed K. Madsen Simulation Optimization Systems Research Laboratory Department of Electrical and Computer Engineering McMaster University Hamilton ONT Canada McMaster University Hamilton ONT Canada Informatics and Mathematical Modelling Technical University of Denmark Denmark

We present advances in microwave and RF device modeling exploiting space mapping (SM) technology. We propose new SM modeling formulations utilizing input mappings, output mappings, frequency scaling and quadratic approximations. Our aim is to enhance circuit models for statistical analysis and yield-driven design. We illustrate our results using a capacitively-loaded two-section impedance transformer, a single-resonator waveguide filter and a six-section H-plane waveguide filter.

关键词： Space technology Samarium Electromagnetic waveguides Statistical analysis Microwave filters Circuit simulation Microwave devices Radio frequency Microwave technology Impedance

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