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喷动床内气固两相流体动力行为的数值模拟 总被引:6,自引:4,他引:2
引 言喷动床被广泛应用于不同工业领域中 ,如石油裂解反应 -再生器、煤和农业废弃物气化和燃烧 ,喷动床还被应用于粮食和药品的干燥等[1] .因此 ,喷动床设计应满足不同应用的要求 .喷动床内气相反应物的反应时间和停留时间依赖于床体几何结构和运行参数 .尽管已有许多的实验对喷动床内气固两相流动进行了研究 ,得到了喷射区、环形区和喷泉区内的气固两相流动流体动力特性 ,然而由于喷动床内气固两相流动的复杂性 ,人们对床体几何结构和运行参数对喷动床动力学的影响至今并不清楚 .因此 ,床体几何结构和运行参数等对喷动床动力学的影响成为… 相似文献
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喷动床反应器气固流动模型的研究进展 总被引:3,自引:0,他引:3
首先对喷动床流动特征参数关联式进行了扼要介绍,继而着重总结了近年来喷动床内气固流动模型(喷射区气固稀相流模式、环隙区气体渗流模式以及固体颗粒流模式)、以及喷动床放大规律等基础理论研究的进展。最后,提出了未来喷动床流动模型工作的突破点和相应思路。 相似文献
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A theoretical model of a spouted bed chemical reactor, involving vapour phase reaction in the presence of catalyst or heat carrier particles, is proposed. The hydrodynamic features relevant to the model are described in as generalized a manner as permitted by the available information. The application of the model is then demonstrated by making certain predictions concerning the effect of the major variables on gas conversion for a first order reaction, as well as on the relative performance of spouted, fixed, and fluidized bed systems. 相似文献
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Shuyan Wang Baoli Shao Rui Liu Jian Zhao Yang Liu Yikun Liu Shuren Yang 《中国化学工程学报》2015,23(10):1579-1586
Flowbehavior of gas and particles in conical spouted beds is experimentally studied and simulated using the twofluid gas-solid model with the kinetic theory of granular flow. The bed pressure drop and fountain height are measured in a conical spouted bed of 100mmI.D. at different gas velocities. The simulation results are compared with measurements of bed pressure drop and fountain height. The comparison shows that the drag coefficient model used in cylindrical beds under-predicted bed pressure drop and fountain height in conical spouted beds due to the partial weight of particles supported by the inclined side walls. It is found that the numerical results using the drag coefficient model proposed based on the conical spouted bed in this study are in good agreement with experimental data. The present study provides a useful basis for further works on the CFD simulation of conical spouted bed. 相似文献
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CFD modeling of the gas-particle flow behavior in spouted beds 总被引:1,自引:0,他引:1
Gas-particle flow behavior in a cylindrical spouted bed and a three dimensional spout-fluid bed of spherical particles was simulated using the Eulerian-Eulerian two-fluid modeling approach, incorporating a kinetic-frictional constitutive model for dense assemblies of the particulate solid. The interaction between gas and particles was modeled using the Gidaspow drag model and the predicted hydrodynamic characteristics are compared with published experimental data. The overall flow patterns within the cylindrical spouted bed were predicted well by the model, i.e. a stable spout region, a fountain region and an annular downcomer region were correctly predicted by the model. The flow instabilities which develop in the spout-fluid bed are along with discussion of the mechanisms leading to instabilities. Bubble formation and motion of the bubbles inside the spout-fluid bed are also described. Such predictions can provide important information on the flow field within the spouted beds for process design and scale-up. 相似文献
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Wojciech Sobieski 《Drying Technology》2013,31(12):1331-1343
This article discusses the key aspects of developing a simulation model of a spouted bed grain dryer for an analysis of fluid dynamics. The following aspects have been analyzed: selection of computational space, type of geometry and computational grid, configuration of the mathematical model (based on the Eulerian multiphase model) through the selection of “closures,” turbulence modeling, the simulation model's sensitivity to changes in phase and flow parameters, as well as the configuration of numerical parameters. The presented study makes reference to an earlier experiment carried out by the author, and it sums up the author's previous work in the modeling of a spouted bed grain dryer. This article presents a synthetic overview of the problems that are frequently encountered in the process of developing simulation models of a spouted bed grain dryer and proposes several solutions. 相似文献
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Batches of coal were subjected to comminution in a 152 mm dia. spouted bed using glass beads as the grinding medium. The basic coal comminution mechanisms of attrition, impaction and crushing were also individually studied, each in a different kind of apparatus, and the first two mechanisms were also each successively accentuated in the spouted bed by use of appropriate inserts. The particle size distribution of the coal was determined at frequent intervals for each run. An attempt was made to interpret and model the spouted bed results mechanistically. 相似文献
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Gas-particle flow behavior in a spouted bed of spherical particles was simulated using the Eulerian-Eulerian two-fluid modeling approach, incorporating a kinetic-frictional constitutive model for dense assemblies of the particulate solid. The interaction between gas and particles was modeled using the Gidaspow drag model and the predicted hydrodynamics is compared with published experimental data. To investigate drying characteristics of particulate solids in axisymmetric spouted beds, a heat and mass transfer model was developed and incorporated into the commercial computational fluid dynamics (CFD) code FLUENT 6.2. The kinetics of drying was described using the classical and diffusional models for surface drying and internal moisture drying, respectively. The overall flow patterns within the spouted bed were predicted well by the model; i.e., a stable spout region, a fountain region, and an annular downcomer region were obtained. Calculated particle velocities and concentrations in the axisymmetric spouted bed were in reasonable agreement with the experimental data of He et al. (Can. J. Chem. Eng. 1994a, 72:229; 1994b, 72:561). Such predictions can provide important information on the flow field, temperature, and species distributions inside the spouted bed for process design and scale-up. 相似文献
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A mathematical model of the spouted bed gasifier has been constructed based on simplified first order reaction kinetics for the gasification reactions and the stream tube hydrodynamic model of Mathur and Lim. This two region model treats the spout as an isothermal plug flow reactor with cross flow into a series of streamtubes forming the annulus. Each streamtube is considered as a plug flow reactor. The effects of kinetic and hydrodynamic parameters on model predictions are illustrated, and a comparison made with experimental gas composition profiles obtained in a 0.30-m dia. gasifier. 相似文献
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导向管喷动床是较为常见的一种喷动床改进床型,通过阻断喷动区与环隙区气固接触来提高颗粒循环的规律性与稳定性。本文采用计算颗粒流体力学(CPFD)方法对于直径150mm的柱锥式导向管喷动床进行了数值模拟研究,考察了导向管直径对于喷动床内颗粒流动特性的影响,从环隙区死区分布、颗粒速度分布、固体循环量等方面分析了具有不同直径导向管喷动床的运行状态。结果表明,加入导向管在减少床内死区的同时也降低了运行时的固体循环量,对于本次采用的喷动床结构尺寸与运行参数,只有在导向管直径为40~60mm时才能保证床内具有良好喷动状态,综合考虑各因素,选用直径50~55mm的导向管最为合适。对于具有类似结构与运行条件的柱锥喷动床,导向管直径可考虑选为无导向管运行时喷动区直径的1.2~1.375倍。 相似文献