Fuel Cell Stack Bridge Portion Guide for Water Discharge
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Solution Overview
Problem
In internal manifold type fuel cell stacks, water accumulation near the outlet manifold leads to corrosion of metal separators due to potential differences, causing performance degradation and gas shielding capability loss.
Innovation Solution
A fuel cell stack design with a bridge portion that includes a guide portion to break the continuity of condensed water, preventing liquid junction between unit cells, using protrusions or projections to obstruct water flow and reduce corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the width of the gas outlet adjacent to the gas outlet manifold hole is increased to discharge condensed water, then water discharge capability is improved, but liquid junction occurs between unit cells causing corrosion currents
Solution Approach 1:
The gas outlet is divided into multiple outlets instead of a single wide outlet. This segmentation allows condensed water to be discharged through multiple separate paths, reducing the likelihood of continuous liquid junction between unit cells while maintaining effective water discharge capability.
Solution Approach 2:
The gas distribution plate incorporates a hydrophobic coating in the gas outlet region. This local modification creates a water-repellent surface that prevents condensed water from forming continuous liquid junctions between unit cells, thereby reducing corrosion currents while still allowing water discharge.
2Strength
If metal separators are used to construct the fuel cell stack, then structural strength is improved, but corrosion occurs due to potential difference leading to performance degradation
Solution Approach 1:
Hydrophobic coatings are applied specifically to the gas outlet regions of the metal separators and gas distribution plates. This local treatment maintains the overall structural strength of metal components while creating water-repellent zones that prevent corrosion at critical interfaces where liquid junctions would occur.
Solution Approach 2:
The hydrophobic coating acts as an intermediary layer between the metal separator surfaces and condensed water. This coating prevents direct contact between water and metal surfaces at critical interfaces, thereby eliminating the electrochemical cells that cause corrosion while preserving the metal's structural properties.
3Productivity
If condensed water flows continuously through the gas outlet to the gas manifold hole, then water discharge is efficient, but liquid junction causes corrosion and metal ion emission
Solution Approach 1:
The continuous water flow path is segmented into multiple discrete discharge points through the multiple gas outlets. This breaks the continuous liquid junction that would otherwise form between unit cells, preventing corrosion and metal ion emission while maintaining overall water discharge efficiency.
Solution Approach 2:
Hydrophobic coatings are applied to the gas outlet regions to create water-repellent surfaces. This local modification allows efficient water discharge through multiple outlets while preventing the formation of continuous liquid junctions that cause corrosion and metal ion emission.
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
Prevents corrosion currents and maintains gas shielding performance by effectively breaking the continuity of condensed water, ensuring efficient long-term power generation.
Implementation Method 1
The guide portion breaks a continuity of condensed water
Implementation Method 2
a fuel cell stack that generates a required electric power... Each of the unit cells includes a membrane electrode assembly (MEA)... The MEA includes an electrolyte membrane (electrolyte), which is a polymer ion-exchange membrane, and an anode electrode and a cathode electrode sandwiching the electrolyte membrane therebetween
Implementation Method 3
even if a part of water in the gas is condensed in the gas channel groove section
Data Source
AI summary
A fuel cell stack includes a plurality of unit cells stacked in a stacking direction substantially along a direction of gravity. Each of the plurality of unit cells includes a first metal separator, a second metal separator, and a membrane electrode assembly sandwiched between the first metal separator and the second metal. A reactant gas channel allows a reactant gas to flow along a surface of each of the first and second metal separators. A reactant gas inlet manifold and a reactant gas outlet manifold allow the reactant gas to flow the reactant gas inlet manifold and the reactant gas outlet manifold in the stacking direction. A bridge portion forms a connection channel to connect at least the reactant gas outlet manifold to the reactant gas channel. The bridge portion includes a guide portion to break a continuity of condensed water.