探討區域分割型質子交換膜燃料電池不同溫濕度下對性能穩定性之研究

Dependence of Gas Stoichiometries and humidity on the Uniformity and Stability of Segmented PEM Fuel Cell

陳長慶(Chang-Ching Chen)

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/碩士(2006年)

https://doi.org/10.6838/YZU.2006.00127

摘要

PEMFC性能取決於許多相互依賴參數，觀察局部區域電流分佈，是診斷燃料電池內部現象與未來發展重要量測工具，可帶來許多一般燃料電池無法觀測之現象。本文探討區域分割型質子交換膜燃料電池(PEMFC)不同溫濕度下對性能穩定性之研究，藉由電池溫度可加熱至所需要之不同操作條件並瞭解其特性，實驗中探討了電池本身內部接觸阻抗、整體動態阻抗、質傳現象、燃料與氧化劑當量、雙邊加濕燃料相對溼度之效應、上下游濃度分佈均勻性及穩定性。由實驗結果顯示可發現，區域電流密度強烈受到操作過程中雙邊燃料相對濕度､空氣當量影響。電池操作50℃，雙邊燃料相對濕度處於34.38%與0%狀態，此時，在入口區域乾空氣進入流道導致入口處乾膜效應增加，明顯地發現MEA上游區域有乾膜現象，且空氣濕度沿著流道路徑逐步地增加，由於累積反應生成水至下游區域，故下游區域電流密度增加，導致出口處(下游區域)電流密度高於入口處(上游區域)電流密度，故導致電池整體電流密度降低。
實驗結果顯示，隨著電池燃料當量降低，濃度極化現象會越明顯，且最先出現在下游區域，並隨著負載增加，其濃度極化現象將會往上游區域明顯影響且越小之空氣當量亦將會導致濃度極化現象提早發生，本實驗中亦發現陰極端當量對於電池極重要且積水現象會比陽極端更顯而易見。

關鍵字

區域分割型質子交換膜燃料電池,電流密度分佈,溼度效應,燃料當量。

並列摘要

The performance of a PEM-fuel cell depends on many interdependent parameters. Measuring local currents in PEM-fuel cells is an important tool for diagnostics and development. A segmented cell has been developed, which can serve as a key instrument to investigate different phenomena in cells and stacks of technical relevance. In this paper, using completely segmented regions of PEMFC (Proton Exchange Membrane Fuel Cells) to different feed gas humidity, operation temperature, investigate into steady-state performance, and analyze the properties of PEMFC with differerent cell teperatures. In the experiment, probing into internal resistance of this cell, dynamic resistance, mass-transfer limitation, flow channel flows in direction, flow rate of fuel and oxidant, relative humidity of fuel, concentration of swimming from head to foot. These results show, that the local current distribution is strongly influenced by the relative humidity of fuel, the stoichiometry of the process air and the mode of operation. Operation at a cell temperature of 50℃, relative humidity of 34.38% and 0%,This is due to the drying of the membrane (and increasing its resistance) early in the air path due to the passage of the high mass flow of comparably dry air. The relative humidity of the air increases along the path due to the product water and therefore current density increases as well. The last segment in the air path carries the highest current, account decelerate entire cell current density.
These results show, the concentration polarization is clearer with lower fuel flow rate, and it occurs the first in the downstream of flow channel and extends to the upstream of flow channel with increasing loading. The lower air flow rate also makes the concentration polarization occur early. The air flow rate has the very important effect for PEMFC, because the cathode is flooded easily by the water brought by humidity and produced by the electrochemistry reaction. Therefore, the cathode’s flooding occurs clearer than anode’s flooding.

並列關鍵字

PEMFC, segmented region, relative humidity, flow rate of fuel.

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