Hydrodynamic Analysis on a Slurry Bubble Column Using Ultrasonic Technique

在这项工作中，超声方法已被开发用于分析浆态鼓泡塔中的流体力学。为了建立超声波技术，推导了气-液和液-固体系中以超声波传播时间差表示的速度差、超声波衰减和分散相含率之间的关系。理论与实验结果的比较表明，两者吻合较好。在此基础上，提出了利用两个不同频率的超声波脉冲的速度变化或一个超声波脉冲的速度变化和衰减同时测量三相体系气固含率的模型，并应用该模型研究了浆态鼓泡塔内气固含率的轴向和径向分布。根据浆态鼓泡塔的结构特点，提出了浆态鼓泡塔的宏观流动模型， 关于我们 泡沫的分布。研究了不同操作参数（气速、液速、固载量和颗粒直径）下气泡分布、流动方案和颗粒浓度分布之间的关系。讨论了浆态鼓泡塔中固体颗粒的径向迁移机理，提出了描述浆态鼓泡塔中气泡和固体颗粒径向分布的气泡-尾流-颗粒扩散模型。该模型结合了气泡-尾迹模型和颗粒/气泡扩散模型，考虑了气泡-颗粒、尾迹-颗粒相互作用、颗粒扩散和侧向升力。计算的颗粒分布曲线与超声法测量的颗粒分布曲线相吻合，表明该模型能很好地描述实验观测到的颗粒分布趋势。少

In this work, an ultrasonic method has been developed to analyze the hydrodynamics in a slurry bubble column. To establish the ultrasonic technique, the relationships among velocity difference in term of transmission time difference of ultrasound, the ultrasonic attenuation and the dispersed phase holdups in gas-liquid and liquid-solid systems have been derived. Comparison between the theory and the experimental results showed a good agreement. Based on those relations, a model for simultaneous measurement of gas and solid holdups in three-phase systems has been proposed by utilizing the velocity changes of two ultrasonic pulses with different frequencies or the velocity change and the attenuation of one ultrasonic pulse.The method gas been applied to investigate the axial as well as radial distributions of gas and solid holdups in a slurry bubble column for various operating variables. The macroscopic flow scheme model in the slurry bubble column has been proposed based on the structu … More re of the bubble distribution. The relationships among the gas bubble distribution, the flow scheme and the particle concentration distribution have been investigated for various operating variables including the gas and the liquid velocities, the amount of solid loading and particle diameter. The mechanism of radial migration of solid particles in the slurry bubble column has been discussed.To describe the radial distribution of the gas bubble and the solid particles in the slurry bubble column, a bubble-wake-particle diffusion model has been proposed. The model has been developed by combining the bubble-wake model and the particle/bubble diffusion model and by taking into account of the bubble-particles and wake-particles interactions, the particles diffusion and the lateral lift force. The calculated particles distribution profiles have been aompared with the measured ones by the ultrasonic method, and showed that the model can describe well the trend of the distributions observed experimentally. Less