Fuel Cell Column Stress Mitigation for Thermal Expansion Mismatch
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Solution Overview
Problem
Fuel cell stacks face challenges due to stress from shape mismatch and coefficient of thermal expansion mismatch between the stack and the manifold plate, leading to potential cracking and reduced performance, particularly in high-temperature solid oxide fuel cell systems.
Innovation Solution
Incorporating a mitigation structure, including a compliant layer and a peripheral seal with a high-temperature tribological coating, to reduce thermal stress and maintain electrical contact between the stack and the manifold plate, while also using a chromium-iron alloy interconnect with a nickel mesh for improved conductivity and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a rigid connection is used between the stack and manifold plate, then structural stability is improved, but thermal stress and cracking risk increase due to shape mismatch and coefficient of thermal expansion mismatch
Solution Approach 1:
A flexible membrane is introduced between the stack and manifold plate, allowing relative movement and stress absorption while maintaining the seal and structural integrity. This flexible element accommodates thermal expansion differences without causing cracking in the rigid components.
Solution Approach 2:
The flexible membrane acts as an intermediary layer between the stack and manifold plate, mediating the thermal expansion mismatch. This intermediate element absorbs stress and prevents direct stress transmission that would cause cracking in the rigid components.
2Strength
If a flexible membrane is used to accommodate thermal expansion, then stress reduction is improved, but electrical conductivity may deteriorate
Solution Approach 1:
The flexible membrane is constructed as a composite material combining elastomer and conductive fabric layers. This composite structure provides both the flexibility needed for stress accommodation and the electrical conductivity required for reliable current collection from the stack.
Solution Approach 2:
The membrane's electrical conductivity is enhanced by incorporating conductive fabric with specific conductivity properties. The conductive fabric network within the elastomer matrix allows electrical current to pass through while maintaining the flexible, stress-absorbing characteristics of the membrane.
3Ease of manufacture
If conventional sealing methods are used, then manufacturing simplicity is maintained, but seal reliability deteriorates under thermal cycling and stress conditions
Solution Approach 1:
The sealing system uses a composite flexible membrane combining elastomer and conductive fabric, which maintains reliability under thermal cycling and stress while remaining manufacturable through standard bonding processes. The composite structure provides both sealing and electrical functionality in a single integrated component.
Solution Approach 2:
The flexible membrane serves multiple functions simultaneously: sealing the interface between stack and manifold plate, accommodating thermal expansion differences, and providing electrical conductivity for current collection. This multi-functionality reduces the need for separate components while maintaining reliability.
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
The mitigation structure effectively reduces thermal stress and electrical disconnections, enhancing the durability and performance of the fuel cell stack by accommodating thermal expansion differences and maintaining contact under varying conditions.
Implementation Method 1
peripheral seal with a high-temperature tribological coating
Implementation Method 2
coefficient of thermal expansion mismatch between the stack and the manifold plate
Implementation Method 3
chromium-iron alloy interconnect with a nickel mesh for improved conductivity
Data Source
AI summary
A fuel cell column includes a stack of alternating fuel cells and interconnects, where the interconnects separate adjacent fuel cells in the stack and contain fuel and air channels which are configured to provide respective fuel and air to the fuel cells. a manifold plate containing a bottom inlet hole and a bottom outlet hole located in a bottom surface of the manifold plate, top outlet holes and top inlet holes formed in opposing sides of a top surface of the manifold plate, outlet channels fluidly connecting the top outlet holes to the bottom inlet hole, and inlet channels fluidly connecting the top inlet holes to the bottom outlet hole, and a mitigation structure configured to reduce stress applied to the stack due to at least one of a shape mismatch or coefficient of thermal expansion mismatch between the stack and the manifold plate.