Expanded Metal Gas Flow Path for Fuel Cell Water Management
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Solution Overview
Problem
Fuel cells experience uneven electric power generation and decreased output voltage due to drying at the oxidizing gas inlet, particularly at high temperatures, caused by excessive water evaporation from the gas diffusion layer, leading to concentration overpotential issues at normal temperatures.
Innovation Solution
The fuel cell design incorporates expanded metal with varying opening sizes in the gas flow path, where the upstream side has smaller openings to reduce water carryover and the downstream side has larger openings to ensure adequate oxygen supply, maintaining output voltage at both normal and high temperatures by optimizing the ratio of first to second expanded metal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contact rate or contact area between the expanded metal and the gas diffusion layer is increased to suppress water evaporation, then the electric power generation capability at high temperatures is maintained, but the output voltage decreases at normal temperatures due to concentration overpotential caused by lack of oxygen
Solution Approach 1:
The expanded metal is designed with different opening sizes in different regions: smaller openings in the upstream region (near gas inlet) to reduce water carryover and larger openings in the downstream region (near gas outlet) to ensure adequate oxygen supply. This local differentiation allows the structure to simultaneously maintain high temperature performance and normal temperature output voltage.
Solution Approach 2:
The gas flow path is divided into multiple regions along the gas flow direction, with each region having expanded metal with appropriately sized openings. This segmentation allows independent optimization of each region's function: water management in the upstream region and oxygen supply in the downstream region.
2Power
If larger openings are used in the expanded metal to ensure oxygen supply, then the output voltage at normal temperatures is maintained, but water carryover increases causing drying at the gas inlet at high temperatures
Solution Approach 1:
Different regions of the expanded metal have different opening sizes tailored to their specific functional requirements. The upstream region uses smaller openings to prevent water carryover, while the downstream region uses larger openings to facilitate oxygen supply, resolving the contradiction between these two opposing requirements.
Solution Approach 2:
The expanded metal structure is segmented into multiple zones along the gas flow path, with each zone having optimized opening dimensions. This allows the system to simultaneously achieve water management in the inlet region and oxygen supply in the outlet region without compromise.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively suppresses output decrease due to drying at the gas inlet, ensuring consistent output voltage at normal and high temperatures by balancing gas flow and oxygen availability, thereby improving the distribution of electric power generation.
Implementation Method 1
oxidizing gas that flows on the gas diffusion layer side with oxidizing gas that flows on the separator side
Data Source
AI summary
A cathode-side gas flow path of a cell that forms part of a fuel cell is formed by a first expanded metal arranged on a gas inlet side, and a second expanded metal arranged on a downstream side. The first expanded metal is such that mesh is arranged in a straight line, and gas that flows on a gas diffusion layer side is separated from gas that flows on a separator side. The gas flowrate on the gas inlet side is reduced, so the amount of produced water that is carried away is reduced. As a result, the gas inlet side is inhibited from becoming dry at high temperatures.