透明PEMFC陰極水管理對性能穩定度影響之研究

The study of cathode water management on performance stability of transparent PEMFC

徐俊英(Chun-Ying Hsu)

指導教授 ： 蘇艾

共同指導教授 ： 翁芳柏

元智大學/工程學院/機械工程學系/博士(2007年)

https://doi.org/10.6838/YZU.2007.00183

摘要

本文主要研究在不同的陰極氣體當量比、氣體外部加濕與否、氧氣濃度及陰極流道積水對PEMFC性能之影響，本研究製作透明燃料電池模型以CCD攝影機拍攝並觀察陰極流道內之積水模式。
結果發現柵狀流道及指叉流道較易發生積水，若要減少積水現象，流道路徑的設計要盡量符合流線模式。在高電壓(0.7V以上)、低陰極氣體當量比或低電池操作溫度條件下，陰極流道均易發生積水；電池達到最佳輸出性能之條件為電壓介於0.45~0.55V、電池溫度50℃、氣體加濕溫度70℃、陰極氣體當量比達到6；在低電壓(0.4~0.6V)，電池溫度固定在50℃，在陰極氣體有外部加濕時，性能與陰極氣體當量比成正比關係，直到當量比達到臨界值6止。當陰極氣體改為氧氣不加濕時，電池性能與陰極氣體當量比則呈現相反之趨勢。
樹枝狀流道對於液態水有較佳的保存能力，在加濕溫度大於電池溫度條件下流道卻反而容易出現積水現象。實驗也發現當流道內壓力較小時，上游區開始積水並導致壓力上升，當流道內之壓力達到排水的臨界點時，積水隨即被推至下游區並由流道出口排出，流道內的壓力亦隨即下降，液態水再次重複開始累積。
由暫態電流負載實驗發現，當電池切換為大電流負載時，GDL內的氫氣及薄膜內的氫離子濃度不足以及時供應反應所需，造成電壓下降。

關鍵字

質子交換薄膜燃料電池 ； 水管理 ； 可視化燃料電池 ； 暫態現象

並列摘要

The study investigates the effect of cathode water flooding, gas stoichiometries and humidified temperature on PEMFC performance. In order to observe the flooding pattern, the transparent experiment model is used in this study.
It is found that the parallels and interdigitated flow channels are easily flooding. In order to remove the flooding, the path of flow channel should be fitted the streamline. The results indicated that the cathode channel is easily flooding at high cell voltage (above 0.7V), low cathode stoichiometry or low fuel cell temperature. The performance will reach the best when the output voltage is between 0.45~0.55V, cell temperature 50℃, gases humidified temperature 70℃ and cathode stoichiometry is at 6. The performance and the cathode stoichiometry have positive relation till the stoichiometry is at 6 under the cell temperature is fixed at 50℃, low output voltage between (0.4~0.6V) and gases have external humidity; The relation has an inverse trend when the cathode gas is replaced by dry oxygen.
It is found that the ramification flow field has a better ability of keeping water in the flow channel. The water flooding is appeared more easily in this flow field due to this feature under high gas inlet RH. It is also found that the upstream began has flooding when the pressure is small. But it will result in the pressure increasing. The flooding will be removed when the pressure is large enough and the pressure will decrease. The flooding will began again.
The output voltage appears undershoot in current density step increase. The reason is that the gases are insufficient to supply the reaction in the fuel cell.

並列關鍵字

PEMFC ； water management ； visible fuel cell ； transient phenomenon

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