Fuel Cell Separator Spring Design for Thermal Stress
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Solution Overview
Problem
Conventional electrochemical reaction units, such as solid oxide fuel cells and electrolysis cells, face issues with gas leakage and cracking of glass sealing members due to thermal cycles or heat shocks, which generate excessive stress in brittle components like the glass sealing members and electrolyte layers.
Innovation Solution
The electrochemical reaction unit incorporates a separator with a connection portion that acts like a spring, allowing deformation in a specific direction to reduce stress on the glass sealing member, and specific geometric relationships between the bonding member, connection portion, and separator thickness are maintained to prevent cracking, including L>3, H·L≥0.5, 0.1≤H≤0.6, t≤0.2, and H>t, ensuring effective stress reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a glass sealing member is provided to seal between the air chamber and fuel chamber, then gas leakage is prevented, but excessive stress is generated in the glass sealing member during thermal cycles or heat shock, leading to cracking
Solution Approach 1:
The separator is designed with a connection portion that can dynamically deform in the planar direction during thermal cycles or heat shock. This dynamic deformation capability allows the separator to absorb thermal stress without transmitting excessive stress to the glass sealing member, thereby preventing cracking while maintaining gas sealing performance.
Solution Approach 2:
The separator's structural parameters are optimized by introducing a connection portion with specific geometric characteristics (different position in the first direction compared to flat portions). This parameter change enables the separator to exhibit spring-like behavior, reducing stress on the glass sealing member during thermal variations.
2Stability of the object's composition
If the separator is made rigid to maintain structural stability, then gas leakage is prevented, but the glass sealing member cracks due to excessive stress during thermal cycles or heat shock
Solution Approach 1:
The separator is segmented into distinct functional portions: flat portions for maintaining structural stability and gas sealing, and a connection portion for absorbing thermal stress through deformation. This segmentation allows the separator to simultaneously achieve structural stability and stress reduction.
Solution Approach 2:
Different portions of the separator are designed with different local qualities: the flat portions provide rigidity for structural stability, while the connection portion provides flexibility for stress absorption. This local quality differentiation resolves the contradiction between structural stability and stress resistance.
3Strength
If the connection portion height H is increased to improve stress reduction, then glass sealing member cracking is prevented, but the unit cell height increases
Solution Approach 1:
The connection portion height H is optimized within a specific range (0.1≤H≤0.6 mm) to achieve the balance between stress reduction effect and unit cell height. This parameter optimization ensures sufficient stress absorption capability while controlling the overall dimensions of the fuel cell unit.
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 effectively reduces stress in the glass sealing member and electrolyte layer, preventing cracking and maintaining the structural integrity and gas flow efficiency of the unit cells during thermal cycles or heat shocks.
Implementation Method 1
the connection portion of the separator functions like a spring which readily expands and contracts in the second direction, and the separator readily deformed in the second direction at the connection portion
Implementation Method 2
a portion of the separator surrounding the through hole is bonded to a peripheral portion of the unit cell by means of a bonding member containing a brazing material
Data Source
AI summary
An electrochemical reaction unit including a unit cell; a separator bonded to a peripheral portion of the unit cell by means of a bonding member containing a brazing material; and a glass sealing member which is in contact with both the surface of the separator and the surface of the unit cell, thereby sealing between an air chamber and a fuel chamber. The separator has a first flat portion approximately parallel to a second direction perpendicular to a first direction; a second flat portion approximately parallel to the second direction; and a connection portion having a portion whose position in the first direction is different from that of the first flat portion and the second flat portion and connecting the first flat portion and the second flat portion.