【作者】 张波；

【导师】 许松林； 刘志滨；

【作者基本信息】 天津大学 ， 制药工程， 2018， 硕士

【摘要】 粒子填料床广泛应用于化工、冶金、农业等诸多领域,研究其中的流体动力学特性可以为填料床使用中出现的问题提供解决方案,并为填料床设备的设计和制造提供理论基础。本文利用计算流体力学软件FLUENT,对球形粒子填料床内的单相流体流动进行了模拟,主要工作及结论如下:首先,建立了球形粒子填料床的二维模型,对于填料床中的流动特性进行了模拟,分析了粒子间隙大小、进口速度及粒子排布方式三个因素对于流动的影响,结论包括:压力在轴向上呈递减分布,压降、流速和涡流情况与粒子间隙大小成反比;压降和出口速度与进口速度大小成正比;三角形排布时,管壁附近的区域流速较大,相较于四边形排布,三角形排布的压降更大,但流动更加均衡,涡流情况较弱。其次,对带有扩径区和凹陷区的球形粒子填料床的二维模型进行了模拟,两类填料床的压力分布与正常管柱的填料床相同,都是在轴向上压力大小递减,径向上大小相等;进出口压降则由于变径区的存在而增大,带扩径区时压降增大的幅度在10%左右,带凹陷区时压降增大的幅度超过10%;扩径段内的流动速度则由于流动区域的增加相对减小,涡流情况也相应减弱;随着扩径区直径d_ex的增大,压降先增大后减小;凹陷段内的流动速度因为流动通道尺寸的减小而增大,相应的涡流情况也更加严重;压降随着凹陷区直径增大而增大。最后,对直径比D/d在1³之间的几种填料床的三维模型进行了模拟,分析了填料床孔隙率与直径比的关系,发现直径比D/d<2时,得到的孔隙率与直径比成正比,直径比D/d=2.3时,孔隙率的大小受到粒子填充方式的影响,三种填充方式对应的孔隙率大小顺序为（C）>（A）>（B）;填料粒子与管壁之间的宽阔空隙构成了流动的主要通道,这些较大的空隙内,压力和流速较大,涡流情况较弱,而填料粒子之间的间隙内和粒子与管壁之间的狭窄空隙内,压力和流速较小,涡流情况严重;直径比D/d在1³之间的填料床的压降与Ergun^[47]方程偏差很大,不能用Ergun^[47]方程来预测压降;根据压降数据得到的修正方程与计算结果基本吻合,与文献方程偏差不超过5%,因此可以来预测压降。更多还原

【Abstract】 Particle packed bed has been applied widely in many fields,such as chemical engineering,metallurgical engineering,agriculture and so on.The research on fluid dynamics characteristics of packed bed can provide solutions for problems of packed bed in use,and provide theoretical basis for the designing and manufacturing of packed bed equipment.The single-phase flow in spherical particle packed bed were simulated by using computational fluid dynamics software FLUENT,and main works and conclusions were as follows:First,the two-dimensional physical model of spherical particle packed bed was established,and fluid flow was simulated.The influence of interparticle void size,inlet velocity and particle packing method on flow characteristics were analyzed.According to the simulation results,pressure decreased by degrees in the axial direction.Pressure drop,flow velocity and eddy current were inversely proportional to the size of interparticle void.Pressure drop and outlet velocity were proportional to inlet velocity.Flow velocity near wall were bigger under triangle arrangement of particles,and compared with quadrilateral arrangement,triangle arrangement can make fluid flow more effective and more stable,thus weaken eddy diffusion,but higher pressure drop.Secondly,the two-dimensional physical models of spherical particle packed bed with diameter-expansion zone and diameter-reduction zone were simulated and analyzed respectively.Pressure distribution in two packed bed above mentioned were same as packed bed with normal column.But pressure drop increased because of existence of diameter-variation zones,pressure drop of packed bed with diameter-expansion zone increased by about 10%,and pressure drop of packed bed with diameter-reduction zone increased by over 10%.Flow velocity and eddy current weakened in diameter-expansion zone and enhanced in diameter-reduction zone.With the increase of diameter of diameter-expansion zone,the pressure drop increased first and then decreased,and with the increase of diameter of diameter-reduction zone,it increased all the time.At the end,the three-dimensional physical models of several spherical particle packed bed at 1<D/d<3 were simulated and analyzed.Porosity was proportional to D/d at D/d<2,while porosity was influenced by packing method at D/d=2.3,and the sequence of the corresponding porosity of the three packing methods is(C)>(A)>(B).Pressure and flow velocity in main flow channel composed of wide voids between particles and wall were bigger,and eddy current was weaker,while in interparticle void and narrow void between particles and wall,pressure and flow velocity were smaller and eddy current was more violent.The deviation between pressure drop of packed bed at 1<D/d<3 and Ergun equation was very large,and pressure drop of packed bed at 1<D/d<3 can not be predicted by Ergun equation precisely.According to the simulation results,modified pressure drop equation was proposed.更多还原