双联毛细管管口气泡生长可视化实验

Visual Experiments on Bubble Growth and Departure at the Open Tip of Two Capillary Tubes Connected with a Gas Chamber

利用高速摄影仪对双联毛细管管口气泡的生长和脱离特性进行了可视化实验研究。实验结果表明,当液体淹没双联毛细管管口时,在管内无气体流动情况下,管径大和亲水的毛细管易于成为液体通道,而管径小和憎水的毛细管易于成为气体通道;在有气体流动情况下,管径大的毛细管成为气体通道,而管径小的则成为液体通道。当气室的进气流量增大时,双联毛细管端口处气泡脱离直径变化很小,而气泡的脱离周期却随之明显减小,双联毛细管的气泡生长和脱离会发生明显的相互影响。此外,液体流速对气泡的生长和脱离有很大的影响,液体流速越大,气泡脱离越快,气泡的脱离直径则越小;在液体流速较大时,靠近流体进口处的毛细管端口气泡生长和脱离明显加快,从而导致相邻毛细管端口的液体回流现象。

The bubble growth and departure at the open tip of two capillary tubes joined with a gas chamber was investigated by using a high-speed video imaging system. The experimental results showed that the capillary tube with larger size and hydrophilic property act as the liquid flow channel while the one with smaller size and hydrophobic property as the gas flow channel when liquid submerged the tip of the two capillary tubes without internal gas flow. In contrast, the larger capillary tube become a gas flow channel and the smaller one a liquid flow channel when liquid submerges the tip of the two capillary tubes with internal gas flow. The bubble departure period significantly decreases and the bubble departure diameter eeps in gentle increase with the increase of the flow rate of gas injected into the gas chamber. The liquid flow rate in test section has a significant effect on the bubble growth and departure. A larger liquid flow rate led to a higher bubble departure frequency and a larger bubble departure diameter. At a larger liquid flow rate, the bubble growth and departure at the tip of the upstream capillary become faster, which result in the liquid return at the tip of the downstream capillary tube.