Fuel Cell Asymmetric Flow Field and Offset Frame for Sealing
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Solution Overview
Problem
In fuel cells with a frame-equipped membrane electrode assembly, non-uniform pressures applied by separators due to differences in reactant gas flow field heights lead to degraded power generation performance and durability, especially when air is used as the oxygen-containing gas, which contains nitrogen and carbon dioxide.
Innovation Solution
A fuel cell design where the height of the oxygen-containing gas flow field is larger than the fuel gas flow field, with a frame member around the membrane electrode assembly, and the central positions of the membrane electrode assembly and the frame member are offset, ensuring uniform sealing and optimal gas supply despite varying gas compositions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the height of the oxygen-containing gas flow field is increased to supply sufficient oxygen, then the power generation performance is improved, but the sealing uniformity between separators and frame member deteriorates
Solution Approach 1:
The patent applies asymmetry by intentionally designing different heights for the oxygen-containing gas flow field and fuel gas flow field. The oxygen-containing gas flow field height is set larger than the fuel gas flow field height, creating an asymmetric structure that optimizes oxygen supply while the frame member's thicker outer peripheral portion compensates for sealing uniformity
Solution Approach 2:
The frame member is designed with non-uniform thickness, where the outer peripheral portion is thicker than the inner peripheral portion. This local quality variation allows the thicker outer portion to maintain sealing uniformity against the separators while the overall flow field height difference maintains adequate oxygen supply
2Adaptability or versatility
If air is used as the oxygen-containing gas, then the availability and cost are improved, but the quantity of gas required increases due to nitrogen and carbon dioxide content
Solution Approach 1:
The patent changes the parameter of flow field height specifically for the oxygen-containing gas flow field, making it larger to accommodate the higher total gas quantity required when using air. This parameter adjustment ensures sufficient oxygen delivery despite the presence of inert gases like nitrogen and carbon dioxide
Data Source
AI summary
A fuel cell includes an MEA, a first separator, and a second separator. A frame member is provided around an outer peripheral portion of an MEA, and held between the first separator and the second separator. The height of an oxygen-containing gas flow field formed by the second separator, from the MEA is larger than the height of a fuel gas flow field formed by the first separator, from the MEA. The central position of the MEA in the thickness direction and the central position of the frame member outer peripheral portion of the frame member in the thickness direction are offset from each other.