Elliptical Separator Embossing for Fuel Cell Contact Resistance
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Solution Overview
Problem
The existing fuel cell separator designs face a trade-off between reducing contact resistance and minimizing reactant gas pressure loss, which affects the power generation performance, and there is a need for a structure that can effectively manage both at the gas outlet/inlet portion and cooling water passage.
Innovation Solution
A fuel cell design featuring a gas passage with an uneven shape on the gas diffusion layer side of the separator, where the embossed portion has an elliptical shape with a major axis inclined relative to the connecting continuous portions, and the cooling water passage has circular embossed portions, allowing for increased contact area and reduced pressure loss without compromising gas flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the embossed portion area is enlarged to reduce contact resistance, then the contact resistance between separator and gas diffusion layer is reduced, but the gas passage area is decreased and gas pressure loss increases
Solution Approach 1:
The embossed portion is designed with an elliptical shape instead of a circular shape, creating asymmetry in the geometry. This allows the major axis to extend in the gas flow direction, providing sufficient contact area for low contact resistance while the minor axis remains compact to maintain adequate gas passage area and minimize pressure loss.
Solution Approach 2:
The embossed portion extends primarily in the longitudinal direction (gas flow direction) rather than expanding equally in all directions. This dimensional differentiation allows the contact area to be sufficient along the flow path while maintaining adequate cross-sectional area for gas passage, effectively resolving the trade-off between contact resistance and pressure loss.
2Reliability
If the embossed portion area is increased to improve contact resistance, then the contact area with gas diffusion layer is enlarged, but the reactant gas collision area increases and fluidity decreases
Solution Approach 1:
The elliptical shape with asymmetric dimensions allows the embossed portion to provide sufficient contact area in the longitudinal direction for low contact resistance, while the limited transverse dimension minimizes obstruction to gas flow and maintains gas fluidity.
Solution Approach 2:
The embossed portion is designed with different dimensional characteristics in different directions: extended length in the gas flow direction for contact resistance reduction, and limited width in the perpendicular direction to minimize impact on gas fluidity. This local quality differentiation resolves the contradiction between contact resistance and fluidity.
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 configuration reduces contact resistance and suppresses gas pressure loss at both the gas and cooling water passages, enhancing the overall power generation efficiency of the fuel cell.
Implementation Method 1
the separator is brought into contact with a neighboring gas diffusion layer at the embossed portion and the reactant gas flows in the area other than the embossed portion of the separator. Accordingly, to adequately maintain the contact resistance between the gas diffusion layer and the separator, it is desired to enlarge the contact area between the embossed portion and the gas diffusion layer
Implementation Method 2
The fuel gas and the oxidant gas supplied to respective electrodes pass through a fuel gas passage and an oxidant gas passage formed on a gas diffusion layer side surface of the separator. Each of the fuel gas passage and the oxidant gas passage is a groove having an uneven shape
Data Source
AI summary
A fuel cell includes a separator having an uneven shape integrally formed on the front and the back surfaces thereof, so that gas can flow in a recessed portion of one surface and cooling water can flow in a recessed portion of the other surface. The separator has a gas passage portion connected to a manifold via a gas outlet/inlet portion. A first continuous portion that connects the gas outlet/inlet portion to the manifold is different from a second continuous portion that connects the gas outlet/inlet portion to the gas passage in communicating width. The gas outlet/inlet portion has an elliptical embossed portion that protrudes toward the gas passage side. A major axis direction of the embossed portion inclines relative to a straight axis connecting one end of the first continuous portion and one end of the second continuous portion toward a straight axis connecting the other ends of the first and second continuous portions.