加压下气泡在液体中的行为

通过物理实验,研究了容器压力、喷嘴孔径和吹气流量对气泡形貌、直径和上升速度的影响.结果表明,在常压下,大孔径喷嘴形成的气泡呈扁平状,其上升过程形状变化大;而在大的压力下,其形成的气泡呈椭球状,上升过程形状稳定.常压下吹气流量对大孔径产生的气泡等效直径影响较小,在小的喷嘴孔径下,吹气流量能明显增加气泡的等效直径,而压力对改变小气泡等效直径的作用不明显.在低的吹气流量和高的容器压力下,较大孔径的喷嘴也能产生较小的气泡.在大孔径下吹气,压力在0.1~0.2 MPa时,不同的吹气流量下的气泡等效直径相差小;而当压力增加到0.3~0.4 MPa时,不同吹气流量的气泡等效直径差别变大.压力增加,气泡的上升速度降低,且在大的吹气流量下,压力对气泡运动速度的影响更为明显;大孔径喷嘴产生的气泡一般有更大的上升速度.在常压下,气体流量对气泡上升速度起着决定性影响,而加压到0.4 MPa,喷嘴孔径对气泡上升速度起着决定性作用.

Behavior of Bottom Injection Bubbles in Liquid Under Elevated Pressures

The influences of vessel pressure， nozzle diameter and gas flow rate on bubble’s behavior， diameter and rising velocity were investigated through physical experiment. The results showed that the bubbles from larger diameter nozzle show flat shape and their shapes change obviously during their up-rising process under atmosphere pressure， while the bubbles show oval-shaped and their shapes are stable in up-rising process under larger pressure. Gas flow rate has small effect on the bubble’s diameter with large diameter nozzle under atmosphere pressure， but it can obviously increase the bubble’s diameter and pressure has little influence on bubble’s diameter from small nozzle. With low gas flow rate and high pressure， the small bubbles can be obtained from the larger diameter nozzle. The difference of bubble’s diameter with different flow rates in injecting gas with the large nozzle is small under 0.1~0.2MPa pressure， while the difference becomes large when the pressure is increased to 0.3~0.4MPa. Rising velocity of bubbles decreases with increase in pressure and the influence of pressure on bubble’s rising velocity is more obvious at large gas flow rate. The bubbles from the large nozzles usually have higher rising velocity. Under atmosphere， the gas flow rate has important effect on rising velocity of bubbles， but under pressure up to 0.4MPa， the nozzle diameter has more important effect on their velocity.