CFD simulation and experiments of dynamic parameters in gas–solid fluidized bed
CFD simulation and experiments of dynamic parameters in gas–solid fluidized bed
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DOI：
10.1016/j.ces.2011.06.035
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发表时间：
2011-11
影响因子：
4.7
通讯作者：
Jingyuan Sun-;Yefeng Zhou;Congjing Ren;Jingdai Wang;Yongrong Yang
中科院分区：
文献类型：
--
作者：
Jingyuan Sun-;Yefeng Zhou;Congjing Ren;Jingdai Wang;Yongrong Yang
颗粒和气泡的运动对决定流态化系统的流体动力学特性起着重要的作用。沸腾床的动力学参数反映了系统中颗粒-颗粒和颗粒-气泡之间的复杂关系。采用结合颗粒流动力学理论的二维欧拉-欧拉模型对气固两相床内气泡和线性低密度聚乙烯(LLDPE)颗粒的动力学行为进行了数值模拟。通过压力脉动实验对模拟方法进行了验证。利用计算的颗粒垂向湍流能谱识别颗粒运动强度和湍流能量耗散的不均匀性。在高频下，能谱在惯性范围内符合Levy-Kolmogorov定律。在此基础上，首次引入颗粒脉动速度小波分解系数的平坦度因子来分析流场中相干结构引起的间歇现象。结果表明，耗散区的间歇性比含能区和惯性区强得多，并且随着径向距离和床层高度的增加而迅速增强。此外，声发射(AE)能量能够指示流型。通过结合颗粒温度和声发射能量，建立了颗粒温度空间分布与流型之间的关系。为了更详细地了解气泡的运动行为，分析了空隙率波动的功率谱。本文的工作为利用CFD模拟气固两相床的动态特性和流场信息提供了有价值的见解。
Particle and bubble motion plays an important role in determining the hydrodynamic characteristics of a fluidized system. The dynamic parameters of a fluidized bed are reflection of the complex correlation between particle–particle and particle–bubble in a system. A two-dimensional Eulerian–Eulerian model integrating the kinetic theory of granular flow is used to simulate the bubble and linear low density polyethylene (LLDPE) particle dynamic behavior in a gas–solid fluidized bed. The simulated method is validated by pressure fluctuation experiment. The computed vertical turbulent energy spectrum of particles is applied to identify the particle motion intensity and the inhomogeneity of turbulent energy dissipation. The energy spectrum captures the Levy–Kolmogorov law in inertial range at high frequency. Furthermore, the flatness factors of wavelet decomposition coefficients of particle fluctuation velocity are for the first time introduced to analyze the intermittence caused by coherent structures in the flow field. The results show that the intermittence in dissipation range is much stronger than that in energy-containing and inertial range, and reinforces rapidly as the radial distance and the bed height increase. Moreover, the acoustic emission (AE) energy is found to be able to indicate the flow regimes. By combing granular temperature and AE energy, the relationship between the spatial distribution of granular temperature and the flow regimes is established. To get more detail of bubble motion behavior, the power spectrum of voidage fluctuation is analyzed. This work provides valuable insights into the dynamic characteristics and the flow field information of a gas–solid fluidized bed by CFD simulation.