Abstract:

The behavior of bubbling from anode diffusion layer into anode channel in passive DMFC was simplified as the formation and detachment of CO₂ bubbles at orifices immersed in a stagnant liquid，and was experimentally investigated by using a visual system. The effects of as flux，orifice submergence，gas nozzle size，liquid concentration were investigated. The results showed that in the process of bubble growth，the contact angle decreased sharply at first and then increased rapidly，then was maintained at a constant value until detachment. With the increase of gas flux，bubble departure diameter changed little and the detaching time tended to be constant after the first rapid decline. Bubble departure diameter decreased and bubble frequency increased with the increase of submergence，and there was a fall in detaching time at first and then became constant in the process. The impact of gas flux on detaching time was weakened with the increase of submergence. As aperture increased，bubble departure diameter increased，resulting in decreasing bubble frequency，and bubble detachment time decreased. When the concentration of methanol was increased，the bubbles produced became smaller and the fluctuation of bubble size became significant，and bubble frequency grew faster. In addition，detaching time decreased first and then became constant especially at a low concentration.

摘要：

将被动式DMFC阳极通道内气泡形成过程简化为CO₂气体注入充满静态甲醇溶液中形成气泡的过程。利用可视化实验研究了气体垂直注入静态甲醇溶液中形成气泡以及气泡脱离的过程，考察了气体流量、液层高度、孔径大小、甲醇浓度对气泡形成及长大脱离过程的影响。结果表明：在气泡的生长过程中，接触角先是快速下降后又迅速上升，然后趋于稳定值直到脱离。随着气体流量的增加，脱离时气泡的直径变化甚微，脱离时间先下降较快后趋于稳定。随着液层高度的增加，气泡的脱离直径变小，产生的频率加快，脱离时间先是减小后趋于稳定；气体流量在此条件下对脱离时间的影响减弱。随着孔径的增加，气泡的脱离直径增加，产生气泡的频率减慢，气泡的脱离时间减小。随着甲醇浓度的增加，气泡的脱离直径变小且波动明显，气泡产生的频率变快，脱离时间先是减小后趋于稳定，对低浓度的溶液影响较为明显。