Zhao Zhenjiang, Zhou Ling, Bai Ling, Lv Wanning, Agarwal Ramesh K
Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013, China.
Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, Missouri 63130, United States.
ACS Omega. 2023 Feb 8;8(7):7151-7162. doi: 10.1021/acsomega.3c00118. eCollection 2023 Feb 21.
The complex multiscale characteristics of particle flow are notoriously difficult to predict. In this study, the evolution process of bubbles and the variation of bed height were investigated by conducting high-speed photographic experiments to verify the reliability of numerical simulations. The gas-solid flow characteristics of bubbling fluidized beds with different particle diameters and inlet flow rates were systematically investigated by coupling computational fluid dynamics (CFD) and discrete element method (DEM). The results show that the fluidization in the fluidized bed will change from bubbling fluidization to turbulent fluidization and finally to slugging fluidization, and the conversion process is related to the particle diameter and inlet flow rate. The characteristic peak is positively correlated with the inlet flow rate, but the frequency corresponding to the characteristic peak is constant. The time required for the Lacey mixing index (LMI) to reach 0.75 decreases with increasing inlet flow rate; at the same diameter, the inlet flow rate is positively correlated with the peak of the average transient velocity; and as the diameter increases, the distribution of the average transient velocity curve changes from "M" to linear. The results of the study can provide theoretical guidance for particle flow characteristics in biomass fluidized beds.
颗粒流复杂的多尺度特性极难预测。在本研究中，通过进行高速摄影实验来研究气泡的演化过程和床层高度的变化，以验证数值模拟的可靠性。通过耦合计算流体动力学（CFD）和离散元方法（DEM），系统地研究了不同粒径和入口流速的鼓泡流化床的气固流特性。结果表明，流化床内的流化状态将从鼓泡流化转变为湍动流化，最终转变为节涌流化，且转变过程与粒径和入口流速有关。特征峰值与入口流速呈正相关，但特征峰值对应的频率是恒定的。莱西混合指数（LMI）达到0.75所需的时间随入口流速的增加而减少；在相同粒径下，入口流速与平均瞬态速度峰值呈正相关；并且随着粒径的增加，平均瞬态速度曲线的分布从“M”形变为线性。该研究结果可为生物质流化床中颗粒流特性提供理论指导。
