漸縮式氣體流道對質子交換膜燃料電池的應用

Abstract

本論文可分為三部分。第一部份為一維之電池之模擬；在此一維的模型中，我們模擬氧氣濃分佈與其電池之性能曲線，再將此結果與Gurau [13]之結果作比較，結果顯示當氣體擴散層中設定與Gurau [13] 一樣之孔隙度時，所獲得的氧氣濃度分佈與Gurau [13]是一樣的，當氣體擴散層之孔隙度固定為0.3時，在氣體擴散層的氧氣濃度分佈較Gurau [13]之結果為低，這是因為孔隙度氧氣較難穿越氣體擴散層之故。在二維的模型中，本文模擬在不同漸縮比例流道(100%， 75%， 50% 與25%)之氧氣、水、壓力以及電池性能曲線分佈以及對電池性能曲線之影響，其結果顯示電池之性能曲線在較低之漸縮比時有較好的表現，這是因為氧氣能有效的進入觸媒層而進行反應。接著本文比較一維與二維之性能曲線，其結果顯示二維之性能曲線較一維模擬差，因為在二維模擬中，氧氣會往另一方向擴散。在三維的模型中，其結果與二維模擬之結果相似，同樣的其結果顯示電池之性能曲線在較低之漸縮比時有較好的表現。最後我們比較二維與三維模擬之電池性能曲線，結果顯示三維模擬之電池性能曲線較二維之模擬的差，原因同前。

The thesis consists of three parts. The first one is the simulation of 1-D model. The obtained results of oxygen distribution and cell polarization curve are compared with these of Gurua [13]. In the oxygen distribution, they are almost identical with the same application of three different porosities in GDL. On the other hand, with single value of porosity, 0.3 in GDL, the present study predicts a lower oxygen concentration. The polarization curve obtained from the present study is exactly the same as the one by Gurau [13]. The second part is the 2-D model. In this model, the distributions of oxygen, water, pressure and the cell polarization curves are compared with four different tapering ratios (100%, 75%, 50% and 25%). The results indicate that the cell performance is improved with a lower tapering ratio. The cell polarization curves in present 1-D model and 2-D model are compared each other, and it shows that the performance of 2-D model is lower than 1-D model due to the lower reaction of oxygen, resulting from one additional diffusion. The third one is the 3-D model. In this 3-D model, we also compare the distributions of oxygen, water, pressure and cell polarization curves with four different ratios. The results are similar to the ones in 2-D model and the cell performance is better with the lower ratio. Finally, we compare the cell polarization curves in present 2-D and 3-D models. The results show that the performance of 3-D model is lower than 2-D model with the same reason mentioned previously.