燃料電池陰極流道表面結構效應之研究

A Study of the Effect of Surface Structure in the Oxidant Channel of Fuel Cell Cathodes

傅清揚(Chen-Yan Fu)

指導教授 ： 蔡瑞益

中原大學/工學院/機械工程研究所/碩士(2001年)

https://doi.org/10.6840/cycu200100306

摘要

本文主要研究燃料電池陰極流道經加入連續週期性凸塊後流場的傳輸現象與其產生的效應。燃料電池為未來極具有潛力的能源之一，而提昇其功率密度也是目前極欲突破的目標；在陰極氣體流道中，水的產生將會阻礙氧化劑擴散至陰極。本文將藉由改變陰極流道內的氣體傳輸機制以增加陰極壁面的剪應力與流道內壓力，進而帶走更多陰極流道的水氣藉以提高燃料電池效率；但相對的，壓降(-dp)也會隨著增加，意味著必須多加入一些額外的功。本文將從所設計的幾種流道內找到較適合的流道機制，以供燃料電池設計人員參考設計。
本文以套裝軟體(PHOENICS)來模擬燃料電池陰極流道，流體取層流(Re=1500)與紊流(Re=3000)模式做為研究，並取氧化劑消耗率(λ= 0、0.1、0.2、0.3)的流道部分，在流道內加入週期性凸塊(h/H=1/9、2/9、1/3、1/2；h:凸塊高度，H:流道寬度)，以數值的方法模擬以上不同狀況流道的流場傳輸現象，最後將所得的結果加以計算，並估計是否能移除更多的水，增加氧化劑擴散至陰極的效率。
結果顯示：(1)具有凸塊的流道比傳統無凸塊流道有較大的陰極壁面剪應力與流道內總壓，故在流道內加入凸塊確實比原流道可移除更多的液態水，更有利於燃料電池運轉。(2)流道內加入的凸塊愈大，陰極壁面的剪應力、流道總壓、壓力降愈大；即凸塊愈大可移除愈多的液態水，但相對的要加入的功也愈大。(3)在氧化劑消耗率較高的流道，陰極壁面的剪應力、流道總壓、壓力降較小。(4)紊流狀態比層流狀態有較大的剪應力、流道總壓與壓力降。

關鍵字

淹沒 ； 擴散損耗 ； 陰極流道 ； 加凸塊流道 ； 氧化劑

並列摘要

The purpose of the thesis is to study the effects of the oxidant transport in a ribbed channel of fuel cell cathode. Water produced inside the cathode will arrest the oxidant diffusion into the electrolyte and lead lower power generating performance. In this study, we focus on the effect of enhancing the shear stress and the total pressure to take water away from the fuel cell cathode channel. Examining the flow profiles in the channel may give a better channel structure that can solve the problem of cathode flooding.
PHOENICS software package is employed to simulate the oxidant transport in a cathode channel. Both laminar (Re=1500) and turbulent (Re=3000) flow are examined. The geometry of the channel is either smooth or with ribbed 1/9 to 1/2 height of the channel width. Oxidant consuming rate is a ranging from 10% to 30%.
The results show that: (1) channel with ribs has higher shear stress, total pressure, and pressure drop than smooth channel, which means ribbed channel can take away more liquid water than nonribbed channel，so that can improve the performance of fuel cell. (2)The shear stress, total pressure, and pressure drop are increased as the rib height is raised. (3) The shear stress, total pressure, and pressure drop is smaller as oxidant consumed ratio is higher. (4)Turbulent flow case has higher shear stress, total pressure, and pressure drop than laminar flow.

並列關鍵字

ribbed channel ； cathode channel ； flooding ； diffusion loss ； oxidant

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