摘要
質子交換膜燃料電池有低溫、低污染、高效率及高能量密度等優勢，一般以為不僅適用於分散式電源與中型動力載具上，也適合作為無人載具及消費性電子產品之能量來源。對小型載具來說，採用呼吸式質子交換膜燃料電池可省掉陰極氧氣供應系統，提高系統的體積及重量功率密度。由於所需的氧氣來自於外部空氣，外部氣流條件便成了影響呼吸式質子交換膜燃料電池性能的重要條件之一。本研究之目的即為探討不同的陰極外部流場對呼吸式質子交換膜燃料電池性能的影響。
本研究成功製作出一嵌入平板表面呼吸式質子交換膜燃料電池，並裝置於循環式風洞中，探討在不同電池擺放方式、陽極氫氣增溼條件、攻角以及外界風速下，對呼吸式質子交換膜燃料電池性能的影響。
由本研究中可發現，外界氣流狀態會影響呼吸式質子交換膜燃料電池陰極氧氣濃度與水平衡，進而影響對其極化曲線。低風速(2.5 m/s)的情況下，可持續供應陰極新鮮氧氣，並將陰極多餘之水分帶走，減少濃度極化現象並提高性能；但強制對流過於旺盛時，反而加速質子交換膜中水分蒸散，增加阻抗而降低電池性能。在0度攻角、陰極端朝下、30 ℃陽極增溼溫度、2.5 m/s風速下達到最大功率密度，89.76 mW/cm2 at 0.406 V。

The advantages of proton exchange membrane fuel cells (PEMFCs), are the lower
operation temperature, the lower pollution, the higher efficiency, the higher energy density,
and suitable for both automotive applications and distributed power generators. PEMFC
might also be an adaptive solution as the power source of unmanned vehicles and
consumer electronics. For small vehicles, to get the oxygen by using air-breathing
PEMFCs would increase the volume and weight power density because oxygen supply
system was not required. While using ambient air as oxygen source, the ambient flow
condition plays an important role in the performance of air-breathing PEMFCs.
In this study, an air-breathing PEMFC was made and embedded into a flat plate which
was further setup into a closed-circuit wind tunnel. By changing the fuel cell position,
anode humidification, angle of attack of plate and ambient flow speed, the influences of
ambient flow field of cathode to the performance of an air-breathing PEMFC will be
discussed respectively.
Results shown that ambient flow condition would affect the oxygen concentration and
water balance of air-breathing PEMFC, and affect the polarization curve. Under the low
wind tunnel speed (2.5 m/s), the forced convection constantly supplies fresh air to cathode
and vaporizes excess water at cathode, abates the phenomenon of concentration
polarization and enhances the performance of fuel cell. However, while the force
convection grows strongly, it would aggravate the vaporization of water in proton
exchange membrane, and increase the impedance of cell and then lower cell power
performance. Under 0° angle of attack, cathode faced up, 2.5 m/s flow speed can reach the
maximum power density, 89.76 mW/cm2 at 0.406 V.

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