采用改进的曳力模型模拟2D鼓泡流化床的流化特性
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摘要
针对特定颗粒浓度范围颗粒团聚作用导致的曳力下降问题,基于传统曳力模型在不同颗粒浓度段的特性分析,选择适用于不同颗粒浓度区间的曳力模型,通过光滑函数得到改进的曳力模型,并耦合欧拉双流体模型对2D鼓泡流化床进行数值模拟.结果表明,与Gidaspow和Syamlal?O'Brien模型相比,改进的曳力模型对床层局部压降的预测结果更好;随表观气速增加,改进的曳力模型能更准确地预测床层膨胀;当表观气速Ug?0.46 m/s时,改进的曳力模型对径向颗粒浓度分布的模拟结果明显好于Syamlal?O'Brien模型.
Based on the characteristic analysis of existing drag models for different particle concentration segments, three traditional drag models, which are adaptive for specific concentration ranges, are chosen for the drag force reduction caused by particle agglomeration. The smooth function is used to connect the drag models, then a modified drag model is proposed. Coupling with the Eulerian?Eulerian model, the modified drag model is applied for simulation of 2D bubbling fluidized bed. The result shows that the modified model has better prediction of partial pressure drop than Gidaspow and Syamlal?O'Brien models. Along with the increase of superficial gas velocity, the modified drag model can predict more accurately bed expansion. When Ug?0.46 m/s, the modified model leads to a better simulation result of particle concentration than Syamlal?O'Brien model apparently.
Based on the characteristic analysis of existing drag models for different particle concentration segments, three traditional drag models, which are adaptive for specific concentration ranges, are chosen for the drag force reduction caused by particle agglomeration. The smooth function is used to connect the drag models, then a modified drag model is proposed. Coupling with the Eulerian?Eulerian model, the modified drag model is applied for simulation of 2D bubbling fluidized bed. The result shows that the modified model has better prediction of partial pressure drop than Gidaspow and Syamlal?O'Brien models. Along with the increase of superficial gas velocity, the modified drag model can predict more accurately bed expansion. When Ug?0.46 m/s, the modified model leads to a better simulation result of particle concentration than Syamlal?O'Brien model apparently.
引文
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[14]陈程,祁海鹰.EMMS曳力模型及其颗粒团模型的构建和检验[J].化工学报,2014,65(6):2003?2012.
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[17]戴群特,陈程,祁海鹰.介尺度非均匀曳力模型的流动自适应性研究[J].工程热物理学报,2015,36(4):785?790.
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[2]朱卫兵,李锦时,王猛,等.提升管内湿颗粒流动特性的离散元模拟[J].中国电机工程学报,2013,33(35):81?88.
[3]Mazzei L,Marchisio D L,Lettieri P.New Quadrature-based Moment Method for the Mixing of Inert Polydisperse Fluidized Powders in Commercial CFD Codes[J].AICh E J.,2012,58(10):3054?3069.
[4]Bakshi A,Altantzis C,Bates R B,et al.Eulerian?Eulerian Simulation of Dense Solid?Gas Cylindrical Fluidized Beds:Impact of Wall Boundary Condition and Drag Model on Fluidization[J].Powder Technol.,2015,277:47?62.
[5]李德波,樊建人,罗坤,等.气固两相流动大规模并行直接数值模拟算法研究进展与展望[J].中国电机工程学报,2013,33(23):107?117.
[6]Ge W,Zhang J Y,Li T H,et al.Pseudo-particle Simulation of Multi-scale Heterogeneity in Fluidization[J].Chinese Science Bulletin,2003,48(7):634?636.
[7]Ding J,Gidaspow D.A Bubbling Fluidization Model Using Kinetic Theory of Granular Flow[J].AICh E J.,1990,36(4):523?538.
[8]Gidaspow D,Jung J,Singh R K.Hydrodynamics of Fluidization Using Kinetic Theory:An Emerging Paradigm:2002 Flour-Daniel Lecture[J].Powder Technol.,2004,148(2):123?141.
[9]Lu H L,Gidaspow D.Hydrodynamics of Binary Fluidization in a Riser:CFD Simulation Using Two Granular Temperatures[J].Chem.Eng.Sci.,2003,58(16):3777?3792.
[10]Syamlal M,O'Brien T J.The Derivation of a Drag Coefficient Formula from Velocity-voidage Correlations[R].Morgantown:US Department of Energy,Office of Fossil Energy,1987.
[11]Vejahati F,Mahinpey N,Ellis N,et al.CFD Simulation of Gas?Solid Bubbling Fluidized Bed:A New Method for Adjusting Drag Law[J].Can.J.Chem.Eng.,2009,87(1):19?30.
[12]祁海鹰,戴群特,陈程.大型流态化多相流数值模拟的关键科学问题?曳力模型的理论分析[J].力学与实践,2014,36(3):269?277.
[13]沈志恒,陈巨辉,王帅,等.高固体流率循环流化床内气体?颗粒团聚物流动特性[J].中国电机工程学报,2009,29(29):25?29.
[14]陈程,祁海鹰.EMMS曳力模型及其颗粒团模型的构建和检验[J].化工学报,2014,65(6):2003?2012.
[15]Wang Y C,Zou Z,Li H Z,et al.A New Drag Model for TFM Simulation of Gas?Solid Bubbling Fluidized Beds with Geldart-B Particles[J].Particuology,2014,15:151?159.
[16]Taghipour F,Ellis N,Wong C.Experimental and Computational Study of Gas?Solid Fluidized Bed Hydrodynamics[J].Chem.Eng.Sci.,2005,60(24):6857?6867.
[17]戴群特,陈程,祁海鹰.介尺度非均匀曳力模型的流动自适应性研究[J].工程热物理学报,2015,36(4):785?790.
[18]Arastoopour H,Pakdel P,Adewumi M.Hydrodynamic Analysis of Dilute Gas?Solids Flow in a Vertical Pipe[J].Powder Technol.,1990,62(90):163?170.
[19]Wen C Y,Yu Y H,Wen C Y,et al.Mechanics of Fluidization[J].Chem.Eng.Prog.Symposium Series,1966,62(6):100?111.
[20]Ergun S.Fluid Flow through Packed Columns[J].Chem.Eng.Prog.,1952,48(2):89?94.
[21]金涌,祝京旭,汪展文,等.流态化工程原理[M].北京:清华大学出版社,2001.17?21.