Microbubbles are applied in various industrial fields. The bubble size is crucial to the process efficiency. Recent studies have shown that the replacement of steady air supply by oscillatory air supply could significantly decrease the sizes of bubbles formed from submerged orifices, owing to the increased momentum force, which is a lifting force for bubble formation. However, the responses of the momentum force to the oscillatory air supply are not yet clear. This study provides a qualitative model for the momentum force as a function of the characteristics of the oscillatory air supply, including the switching frequency, on/off time ratio, and gas flow rate. The model was experimentally validated by investigating the variations in the momentum force with the characteristics of the oscillatory air supply. In addition, the correlation between the momentum force and bubble size under the oscillatory air supply was also investigated.
Sijia Zhao,Ajuan Song,Yijun Cao,Siyuan Yang,Chao Li
The diameter of bubbles generated from submerged orifices is closely related to the air pressure, which consists of static and dynamic pressures. It has been proven that switching the air supply from a steady to oscillatory flow can improve the dynamic pressure and thus lead to smaller bubbles. To complement the control strategy for bubble size optimization, this study proposes an approach to enhance static pressure by introducing a Y-junction shunting configuration under an oscillatory air supply. A model of gas pressure as a function of the shunting ratio was developed and validated experimentally. A positive correlation was observed between the shunting ratio and static pressure. The bubble size first decreased and then increased as the shunting ratio increased from 0 to 3.0. The smallest bubbles were obtained at a shunting ratio of 1.5 with a diameter reduction of 26% compared with no shunting. By segregating the bubble formation process, the bubble diameter at detachment continuously decreases over the shunting ratio. However, the number of coalesced bubbles first decreased and then increased, and the underlying mechanism is discussed. The findings indicated that the shunting air supply could facilitate bubble size optimization when the shunting ratio was appropriately controlled.
危险品化学品经营许可证（带存储）