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为了更准确、直观研究油水两相流流体流动规律,确定PIV技术的适用范围是尤为重要的。通过高速摄像机对管径内流体进行拍摄,可以得到瞬态流体流动特性视频和图像,与传统性测量相比更为直观地反映出流体流动的流态。运用PIV粒子图像测速技术对水平井小管径进行拍摄计算,并对其结果进行评估,得到了PIV技术在水平井中的具体适用范围,分析影响适用范围的因素是流型和流态:也为评定数值模拟时所采用的各种模型的优劣性提供了实验的依据,对今后研究多相流流体的运动规律有着重要意义。 相似文献
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基于离散元法的锥形筒仓中颗粒流体的数学模拟 总被引:2,自引:0,他引:2
采用离散元法对ABS塑料球在筒仓内的流动进行数值模拟,并测定了ABS球的回弹及休止角等微观物性参数,验证了离散元模型中颗粒接触参数的正确性. 基于正交实验法考察了锥形改流体参数对料流的影响,分析了仓壁压力分布规律. 结果表明,锥形改流体参数对物料流型的影响顺序为锥形改流体倾角>锥形改流体距卸料口的高度>锥形改流体高度;锥形改流体倾角<120o时中心流无法转变为整体流. 添加合适的改流体后仓壁所受最大压力减小为原来的一半,最大压力位置上移. 相似文献
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《高校化学工程学报》2017,(4)
为了深入了解纵向涡流对喷动床内气固两相流动特性的影响规律,采用计算流体力学方法对喷动床内气固两相流动的纵向涡流效应进行三维数值模拟。采用RUC曳力系数模型描述气、固相间作用力,通过欧拉-欧拉双流体模型和颗粒动力学理论对气固两相流动进行模型处理。分别对无扰流件、加入一对小球扰流件及加入一对纵向涡流发生器喷动床结构进行了模拟分析及对比。研究表明:加入球体扰流件及纵向涡流发生器之后,喷泉区的喷动高度明显下降,并在球形扰流件及纵向涡流发生器附近产生了二次漩涡。纵向涡流的存在显著地增加了喷动床内环隙区颗粒相的径向速度,增加了喷射区及喷泉区内颗粒体积分数及其密集度,有效增强了喷动床内气体、颗粒沿径向与轴向的湍动能及拟温度值,进而强化了环隙区与喷射区内颗粒、流体两相的横向混合效果及颗粒间的动量交换过程。 相似文献
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射流流化床中锥形分布板对流动的影响 总被引:1,自引:0,他引:1
给出了具有锥形分布板的射流流化床中浓密气固两相流动的多相流体力学基本方程组. 采用二维正交曲线坐标并生成了数值网格,用改进的IPSA方法求解二维正交曲线坐标中的多相流基本方程组,并编制了大型通用程序,流场可视化使用Tecplot软件. 对于给定的模拟计算,计算结果与实验值吻合. 模拟计算中改变了锥形筛板的角度、射流管的直径、床层高度、分布板开孔率的分布、射流气速、床层表观气速等,通过模拟得到床内的流动图像,考察了射流高度及颗粒循环的影响. 相似文献
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<正>由于气体的搅动,筛孔塔板上的流动是极其复杂的气液两相流。目前两相流理论尚不成熟,未见运用此理论对塔板流速场的研究报道,Zhang和Yu的研究虽考虑了气相对液相流动的影响,但由于利用单相流理论,计算结果与实际情况有较大偏差。本文利用Elghobashi等建立的两相流双流体模型,建立了塔板上气液两相流二维流速场计算模型。在此基础上,通过调整模型参数,考虑了液层高度对塔板上返流区二维流型的影响,建立了模型参数值与液层高度的关系,实现了考虑液层高度影响的二维流动——拟三维流动的模拟。计算结果与Porter的实验结果基本相符。 相似文献
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为考察孔内扩散对模拟移动床分离过程的作用,采用综合速率模型对其进行研究,其中流动相模型为轴向扩散活塞流,颗粒相为Fiek定律描述的扩散方程,液相和固相之间的吸附平衡采用改进的Langmuir吸附等温线.对流动相和颗粒相分别采用有限元Galerkin法和正交配置法,沿空间方向离散化后的常微分方程组运用MATI。AB的ODE求解器求解.在验证了模型和离散方法对模拟移动床吸附分离过程计算的可靠性的基础上,模拟了EMD53986对映体的模拟移动床分离过程,跟文献中使用忽略孔内传质过程的模型得到的计算值相比,模拟值与实验值吻合得更好,表明孔内扩散传质过程对模拟移动床模拟计算的重要性. 相似文献
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液固两相磨蚀研究主要集中于圆管弯头和射流工况,板式换热器等狭窄矩形通道内液固两相磨蚀特性的研究鲜见报道。在Fluent软件及其二次开发框架内构建了描述稀疏颗粒液固两相磨蚀特性的CFD-DPM-磨蚀耦合数学模型框架,研究了存在圆柱体阻挡物的狭窄矩形通道内两相流动特性和壁面磨蚀特性,揭示了壁面和固体颗粒的相互作用机制。研究结果表明:阻挡物的存在显著改变了狭窄矩形通道壁面的磨蚀行为;磨蚀速率随液固流速和壁面粗糙度的增加而增加,因此,保证设备较低的入口流速和壁面粗糙度对延长设备寿命至关重要;磨蚀速率随颗粒粒径的增加先增加后降低,在60μm左右时达到极大值;球形度系数对磨蚀行为影响较小。引入量纲为1颗粒尺寸,阐述了液相边界层束缚颗粒运动的作用机制;与光滑壁面工况相比,颗粒以较大能量高频撞击粗糙壁面,导致了壁面磨蚀较快。液固两相以较低的角度和速度撞击壁面,壁面材料去除机理以微切削为主。 相似文献
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引 言流化床换热器具有防、除垢和强化传热等优点 ,在化工、食品、海水淡化、废水处理等领域具有广阔的应用前景[1].目前 ,流化床换热器历经散式流化床、内循环流化床 ,已发展到外循环流化床换热器[2 ],它要求在较稀的颗粒浓度 (颗粒浓度小于 5% )、较高的流速 ( 1~ 3m·s- 1)下操作 .流化床换热器中液体流动及颗粒运动状态的研究对流化床换热器的设计和操作具有重要意义 ,但人们对循环流化床换热器中颗粒运动情况的研究还很缺乏 .考虑到循环流化床换热器中的每根换热管都可作为一个独立的循环流化床对待[3].本文试图建立一滑移速度模型… 相似文献
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Studies in the expansion behaviour of tapered fluidized bed systems are important for specifying the height of the bed. Data have been obtained on the expanded heights of tapered fluidized beds and bed expansion ratios for spherical and non-spherical particles have been calculated. Based on dimensional analysis, models have been developed as a function of geometry of tapered bed, static bed height, particle diameter, density of solid and gas and superficial velocity of the fluidizing medium. The data used to derive the models cover a wide range of operating conditions, with varying fluidization velocities. Effects of static bed height, particle diameter, density, tapered angle and superficial gas velocity over minimum fluidization velocity on bed expansion ratios have been investigated experimentally. A comparison has been made between the calculated values of bed expansion ratios using proposed models and the experimental data. It has been seen that calculated values by models agree well with the experimental values. Models have also been compared with literature data of conventional bed and found its applicability at higher gas velocities with good accuracy. 相似文献
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In this article, computational fluid dynamics (CFD) technology is used to model a spouted bed(SB). The multifluid Eulerian-Eulerian approach based on kinetic theory of granular flows and Gidaspow's drag model for the interaction between gas and particles are applied in the modeling. The effects of the SB properties—that is, cone angle, particle size, cylinder diameter, and static bed height of particles—on its dynamics performance are investigated. The simulated results—that is, flow pattern of particles, fountain height, voidage, and particle velocity of the spout zone—are presented. It is shown that periodic fluctuation of spouting appears in an SB with conical angle of 30° and inlet velocity at 16.6 m/s. When the SB cylinder diameter becomes 0.52 m, periodic fluctuation appears, too. The stable spouting of the SB with a 90° cone angle could be obtained at an inlet air velocity of 24.3 m/s. The fountain height of particles decreased with an increase in particle size and the static bed height of particles. It is kept at about 0.19 m when different SB cylinder diameters in the range of 0.36 to 0.48 m are used. In the spouting region, the voidage decreased with static particle height in bed, but the particle velocity increased. For a certain particle size, the voidage decreased with an increase in particle height, but the velocity of the particles increased. It was also found that the cylinder diameter did not affect the volume fraction of particles except for the cylinder diameter 0.52 m and the change in particle velocity was minimal in the spout zone. With the different static bed height of particles used, the voidage and particle velocity did not change much at the same level of spout zone. 相似文献
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基于Fluent的多孔介质模型,建立了变压吸附制氧发生器的立式填充床模型。采用用户自定义函数功能,以反映吸附传质、传热,并将多孔介质单相模型整合为更精确的气固两相耦合模型。在此基础上,模拟了吸附颗粒直径对气相压力、速度、床层压降以及氧气分离浓度、回收率等参数的影响情况。结果表明:床层压降随颗粒直径的增大而减小;床层对入口急流的抗穿透性能随颗粒直径的增大而减小;相同条件下,采用较小颗粒直径能够提高氧气分离浓度、回收率,原因在于小颗粒直径降低了床层内气体的流速,增加了吸附时间,促进了吸附的进行。 相似文献
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提出并优化了一种旋转流强化的膜组件水力学模型。Box-Behnken方法用于进口直径、进口长度、膜壳高度、进/出口端管长度、球突结构直径,进出口倾斜角度的多参数的实验设计,获得了响应变量最优的膜组件设计方案。通过雷诺应力RSM湍流模型与基于Euler-Lagrange算法的离散相DPM模型的耦合计算,模拟研究了三维模型内液固两相流的颗粒停留时间分布、流体力学特征。模拟结果显示,旋流强化的膜组件壳程的速度分布更加均匀,膜面剪切应力高;湍流耗散率、涡量分布不同于传统膜组件。实验结果证实,优化后的膜组件具有高产水量、低压力降,膜污染速率低的特点。 相似文献
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采用欧拉-欧拉双流体模型,基于水-玻璃珠体系,对长×宽×高尺寸为240 mm×12 mm×1800 mm的竖直窄通道充分发展段内液固两相流动特性进行了数值模拟。结果表明,沿窄通道竖直方向0.7 m以上液固两相流动进入充分发展阶段,在充分发展阶段的窄通道截面上,狭长方向与狭窄方向各位置颗粒速度及浓度均呈中心区域高、贴近边壁区域低的分布趋势;随着入口液速提高,截面各位置颗粒速度均提高,而颗粒浓度在流道中心区域降低,在贴近壁面区域升高;随着初始固相体积分数增加,截面各位置颗粒浓度均提高,而颗粒速度在流道中心区域略有降低,在贴近壁面区域略有升高;在窄通道截面狭长方向两端靠近三边壁影响的区域存在颗粒增浓效应,在截面狭窄方向颗粒速度和浓度分布梯度较大的区域无量纲占比随着入口液速的提高而提高,随着初始固相体积分数的提高而减小。 相似文献
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The gas and particle motions in a bubbling fluidized bed both with and without chemical reactions are numerically simulated. The solid phase is modelled as Discrete Element Method (DEM) and the gas phase is modelled as 2-D Navier-Stokes equations for 2-phase flow with fluid turbulence calculated by large Eddy simulation (LES), in which the effect of particles on subgrid scale gas flow is taken into account. The gas/particle flow structure, the mean velocities and turbulent intensities can be predicted as a function of several operating parameters (particle size, bed temperature, and inlet gas velocity). The lower the inlet gas velocity, the higher the ratio of particle collision. The distributions of the particle anisotropic velocity show that the particles have no local equilibrium, and the distribution of gas kinetic energy corresponds to the distribution of gas-particle coupling moment in the fluidized bed. An intensive particle turbulent region exists near the wall, and the gas Reynolds stress is always much higher than the particle stress. The presence of the large reactive particles in the fluidized bed may affect significantly the gas and particle velocities and turbulent intensities. The effects of the bed temperature and inlet gas velocity on the gas particle flow structure, velocity, and turbulent intensity are also studied. 相似文献