The Experts below are selected from a list of 9 Experts worldwide ranked by ideXlab platform
Jiaqi Yang - One of the best experts on this subject based on the ideXlab platform.
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computational study of gas solid flow in a horizontal Stepped Pipeline
Mathematical Problems in Engineering, 2019Co-Authors: Kaiwei Chu, Renhu Pan, Jiaqi YangAbstract:In this paper, the mechanism governing the particle-fluid flow characters in the Stepped Pipeline is studied by the combined discrete element method (DEM) and computational fluid dynamics (CFD) model (CFD-DEM) and the two fluid model (TFM). The mechanisms governing the gas-solid flow in the horizontal Stepped Pipeline are investigated in terms of solid and gas velocity distributions, pressure drop, process performance, the gas-solid interaction forces, solid-solid interaction forces, and the solid-wall interaction forces. The two models successfully capture the key flow features in the Stepped Pipeline, such as the decrease of gas velocity, solid velocity, and pressure drop, during and after the passage of gas-solid flow through the Stepped section. What is more important, the reason of the appearance of large size solid dune and pressure surge phenomena suffered in the Stepped Pipeline is investigated macroscopically and microscopically. The section in which the blockage problem most likely occurs in the Stepped Pipeline is confirmed. The pipe wall wearing problem, which is one of the most common and critical problems in pneumatic conveying system, is analysed and investigated in terms of interaction forces. It is shown that the most serious pipe wall wearing problem happened in the section which is just behind the Stepped part.
Li Zhengquan - One of the best experts on this subject based on the ideXlab platform.
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Numerical study of particle-fluid flow in complex pipe systems
2017Co-Authors: Li ZhengquanAbstract:In recent years, numerical approaches have become indispensable in studies on particle-fluid flows. In this thesis, various numerical models have been developed and applied to study the particle-fluid flows in three typical complex pipe systems which are widely encountered in many industry sectors such as energy, chemical, and mineral, to name a few. The systems considered here are: industrial scale circulating fluidized beds (CFBs), long-distance high-pressure dense-phase (LHD) pneumatic conveying systems, and novel and complex bypass pneumatic conveying systems. The numerical models used are: the two fluid model (TFM), combined model of computational fluid dynamics and discrete element method (CFD-DEM), and coarse-grained CFD-DEM model. The numerical results of the simulations are validated either qualitatively or quantitatively depending on the availability of experimental data and simulation results for comparison. The work is useful to understand, design, control and optimize the considered systems. Specifically, for industrial-scale CFBs, it is shown that the typical flow structures in the CFBs can be captured by the coarse-grained CFD-DEM approach. The particle clustering phenomenon near walls, phenomenon of solids back-mixing, and core-annular flow structure are observed. Gas-solid flow regime is a bulk behaviour resulting from the collective interactions between particles, particles and particles, particles and wall, particles and gas. Therefore, analysis of the interaction forces in conjunction with the flow behaviour of individual particles can help understand the underlying mechanisms. There is a reasonable agreement between the simulation results and experimental ones for the interaction forces. The effects of some influential variables on the gas-solid flow pattern are also studied to investigate to what extent the coarse-grained model can be used to study the large scale CFB riser and to identify the limitations and weaknesses of this model. In investigating the LHD pneumatic conveying systems, both TFM and CFD-DEM are used. Some key flow features in a Stepped-pipe are captured by the developed models and analysed. The mechanisms governing the complex gas-solid flow in the Stepped-pipe have been identified by the numerical results. The forces governing the motion of gas and solids have also been obtained by simulations and their importance investigated. Further, to improve the performance of pneumatic conveying by lowering the chance of pipe blockage in the Stepped-pipe, a new method using inserts is proposed and tested for the first time. The effect of inserts in a conventional single pipe and a Stepped Pipeline has been investigated. The effects of different insert shapes on the conveying performance of a single pipe have also been studied. The results show that the conveying performance of both the single pipe and Stepped pipe can be improved by implementing the inserts method. In the last part of the thesis, the CFD-DEM method is used to study the particle-fluid behaviour in a bypass system for the first time. It is shown that this model can satisfactorily capture the key features of gas-solid two-phase flow in a bypass system. The forces governing the motion of gas-solid phases have also been investigated. The simulation results are in good agreement with experimental ones. In addition, the particle-fluid flow characteristics for different geometrical conditions are also studied. The numerical results have been analysed in terms of distribution of static pressure, gas and solid velocity, gas-solid flow pattern, and interaction forces. Overall, the numerical simulation methods are proven to be vital in understanding flow mechanisms in various particle-fluid systems
Kaiwei Chu - One of the best experts on this subject based on the ideXlab platform.
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computational study of gas solid flow in a horizontal Stepped Pipeline
Mathematical Problems in Engineering, 2019Co-Authors: Kaiwei Chu, Renhu Pan, Jiaqi YangAbstract:In this paper, the mechanism governing the particle-fluid flow characters in the Stepped Pipeline is studied by the combined discrete element method (DEM) and computational fluid dynamics (CFD) model (CFD-DEM) and the two fluid model (TFM). The mechanisms governing the gas-solid flow in the horizontal Stepped Pipeline are investigated in terms of solid and gas velocity distributions, pressure drop, process performance, the gas-solid interaction forces, solid-solid interaction forces, and the solid-wall interaction forces. The two models successfully capture the key flow features in the Stepped Pipeline, such as the decrease of gas velocity, solid velocity, and pressure drop, during and after the passage of gas-solid flow through the Stepped section. What is more important, the reason of the appearance of large size solid dune and pressure surge phenomena suffered in the Stepped Pipeline is investigated macroscopically and microscopically. The section in which the blockage problem most likely occurs in the Stepped Pipeline is confirmed. The pipe wall wearing problem, which is one of the most common and critical problems in pneumatic conveying system, is analysed and investigated in terms of interaction forces. It is shown that the most serious pipe wall wearing problem happened in the section which is just behind the Stepped part.
Renhu Pan - One of the best experts on this subject based on the ideXlab platform.
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computational study of gas solid flow in a horizontal Stepped Pipeline
Mathematical Problems in Engineering, 2019Co-Authors: Kaiwei Chu, Renhu Pan, Jiaqi YangAbstract:In this paper, the mechanism governing the particle-fluid flow characters in the Stepped Pipeline is studied by the combined discrete element method (DEM) and computational fluid dynamics (CFD) model (CFD-DEM) and the two fluid model (TFM). The mechanisms governing the gas-solid flow in the horizontal Stepped Pipeline are investigated in terms of solid and gas velocity distributions, pressure drop, process performance, the gas-solid interaction forces, solid-solid interaction forces, and the solid-wall interaction forces. The two models successfully capture the key flow features in the Stepped Pipeline, such as the decrease of gas velocity, solid velocity, and pressure drop, during and after the passage of gas-solid flow through the Stepped section. What is more important, the reason of the appearance of large size solid dune and pressure surge phenomena suffered in the Stepped Pipeline is investigated macroscopically and microscopically. The section in which the blockage problem most likely occurs in the Stepped Pipeline is confirmed. The pipe wall wearing problem, which is one of the most common and critical problems in pneumatic conveying system, is analysed and investigated in terms of interaction forces. It is shown that the most serious pipe wall wearing problem happened in the section which is just behind the Stepped part.
Kennedy O. C. - One of the best experts on this subject based on the ideXlab platform.
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Pneumatic conveying performance characteristics of bulk solids
'University of Babylon - Department of Mechanical Engineering Faculty of Engineering', 1998Co-Authors: Kennedy O. C.Abstract:This thesis is concerned with the analysis of the performance of bulk solid pneumatic transport systems. A bulk solid parameter, with the potential to characterise materials on the basis of suitability for this mode of transport, is proposed. Procedures for producing conveying characteristics are developed and linked to conveying models and design requirements. A new model based on the power requirements of the pneumatic conveying process is presented. The deaeration behaviour of bulk solids is analysed in some detail. Theoretical aspects, appropriate test rig arrangements and experimental arrangements are discussed. A characterising parameter, the normalised time constant, is proposed. Extensive experimental data are used to clarify the significance of this performance indicator and to assess its capacity to predict the pneumatic conveying potential of a given bulk solid. The process of generating conveying characteristics for the bulk solid/Pipeline configuration from experimental data is discussed. The computerisation of this process and the application of numerical techniques are developed and demonstrated. The advantages and possibilities are explored, and limitations noted. The implementation of a solids friction factor (Barth type) model within the conveying characteristics procedures noted above, is developed and demonstrated. The application of scale up procedures within this model environment is discussed and tested against experimental data. Determination of conveying characteristics for Stepped Pipelines is demonstrated, as is a method for the optimised design of Stepped Pipeline configurations. A power based pneumatic conveying model is proposed. This model considers the power available from the isothermal expansion of the gas down the Pipeline, and the power consumed by the various components of the system. Features of this model include a solids friction factor correlation, the treatment of bends, a new analysis of the air-only component and a method for the identification of invalid conveying regions. The generation of conveying characteristics curves for single and Stepped Pipeline systems within this model is demonstrated. The performance of the model is tested against a selection of experimental data. Trends inherent in the model, and its scaling behaviour, are examined. Potential areas for further development of the model are discussed
