Bubble size is an important variable in aerated stirred tanks as it determines the surface area available for reactions. In the bubble break-up process, impellers play a key role. Despite this importance, research into the effect of impeller design on bubble size is scarce. In this work we study the effect of two impellers, with and without a stator, as well as the effect of airflow rate, impeller speed and surfactant concentration on bubble size.

Results show that there is a critical impeller speed above which bubble size is not further decreased, regardless of the airflow. Operating at this critical speed results in the smallest bubble size possible without additional turbulence. The reduction in bubble size caused by a stator was quantified for the first time and, interestingly, it was found that the stator also reduced the critical coalescence concentration. The implications of these findings for the design, evaluation and optimisation of impellers are discussed.

Bubble size is an important variable in aerated stirred tanks as it determines the surface area available for reactions. In the bubble break-up process, impellers play a key role. Despite this importance, research into the effect of impeller design on bubble size is scarce. In this work we study the effect of two impellers, with and without a stator, as well as the effect of airflow rate, impeller speed and surfactant concentration on bubble size.

结果表明，存在临界叶轮速度，高于该速度时，无论气流如何，气泡大小都不会进一步减小。以该临界速度运行会导致气泡尺寸最小，而不会产生额外的湍流。第一次量化了由定子引起的气泡尺寸的减小，有趣的是，发现定子也减小了临界聚结浓度。讨论了这些发现对叶轮设计，评估和优化的意义。