Abstract:

The bubble formation and detachment behaviors on the surface layer of packed particles were studied experimentally. The effects of nozzle diameter, packed bed height and particle size on the bubble detachment diameter and the formation period were revealed by using the high-speed camera technology. The differences of bubble formation and detachment behaviors on the surface layer of packed bed and the nozzle were analyzed. The results showed that the initial shape of the bubble generated on the surface of packed bed with the particle size in the range of 1500—3000μm was relatively flat and small, and the evolution of bubble to flat shape was faster. The effect of intake flow rate on the bubble shape was weakened with the increase of particle size. And the increase of nozzle diameter and packed bed height could effectively promote the growth of bubble detachment diameter, but delayed the formation and detachment of bubble and increased the bubble formation period. The effect of particle size on the bubble formation period diminished gradually with the increase of intake flow rate. There was a significant difference between the bubble formation and detachment behaviors on the surface of packed bed and the nozzle. In contrast, the packed bed with the particle size in the range of 150—300μm had a more obvious hindering effect on the formation and detachment of bubble, and the detachment diameter and the formation period of bubble were relatively large.

Key words: bubble, multiphase flow, bubble column reactor, detachment diameter, formation period

摘要：

试验研究了气泡在颗粒床层表面的生成脱离过程及其行为特性，利用高速摄像技术揭示了进气管管径、颗粒床层高度、颗粒粒径等因素对气泡脱离直径及其生成周期的影响规律，对比分析了颗粒床层表面和进气管管口的气泡生成脱离行为差异。研究结果表明：在1500～3000μm粒径范围的床层表面所生成气泡的初始形态相对更扁小，气泡也更快向扁平状演变；颗粒粒径的增大使得进气流量对气泡形态的影响减弱；管径和颗粒床层高度的增大可以有效促进气泡脱离直径的增长，但延缓了气泡的生成脱离，增加了气泡的生成周期；颗粒粒径对气泡生成周期的影响随着进气流量的增大而逐渐减弱；气泡在颗粒床层表面和管口的生成脱离行为存在显著差异，相比之下，150～300μm粒径范围的颗粒床层对气泡的生成脱离具有更明显的阻碍作用，其表面所生成气泡的脱离直径和生成周期相对较大。

关键词: 气泡, 多相流, 鼓泡反应器, 脱离直径, 生成周期