Gas Turbine Combustor Wall Assembly Thermal Mismatch
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Solution Overview
Problem
Combining ceramic matrix composite (CMC) parts with metallic parts in gas turbine combustors is challenging due to their different coefficients of thermal expansion, leading to thermal mismatch and potential stress issues.
Innovation Solution
A double-wall combustor design featuring a metallic outer shell and ceramic inner panels with a damper disposed between them to accommodate thermal expansion, reducing thermal mismatch and stress through a flexible connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC parts are combined with metallic parts in combustors, then heat resistance is improved, but thermal mismatch and stress issues occur due to different coefficients of thermal expansion
Solution Approach 1:
The combustor wall is divided into multiple segments including inner panels, outer shell, and intermediate structures. This segmentation allows each component to expand and contract independently, accommodating the different thermal expansion coefficients of CMC and metallic materials while reducing thermal stress.
Solution Approach 2:
A metallic intermediate structure is introduced between the CMC inner panels and the outer shell. This intermediary component serves as a buffer that accommodates the thermal expansion difference between the ceramic and metallic materials, preventing direct stress transmission and enabling successful integration of dissimilar materials.
2Temperature
If CMC parts are combined with metallic parts in combustors, then heat resistance is improved, but integration challenges occur due to different coefficients of thermal expansion
Solution Approach 1:
The combustor is divided into separable modules including inner panels, outer shell, and intermediate structures. This modular segmentation simplifies manufacturing and assembly processes by allowing each component to be manufactured independently and then assembled, reducing the integration challenges of combining dissimilar materials.
Solution Approach 2:
The metallic intermediate structure acts as a coupling element that facilitates the integration of CMC and metallic parts. This intermediary component provides standardized interfaces and connection mechanisms that simplify the assembly process while accommodating the fundamental material differences.
3Strength
If a rigid connection is used between outer shell and inner panels, then structural strength is improved, but thermal stress increases due to constrained thermal expansion
Solution Approach 1:
The connection between the outer shell and inner panels transitions from a rigid fixed connection to a dynamic flexible connection. This allows the structure to adapt to thermal expansion and contraction, maintaining structural integrity while accommodating dimensional changes during thermal cycling.
Solution Approach 2:
Flexible connection elements are introduced between the rigid outer shell and inner panels. These flexible components allow for relative movement and dimensional change while maintaining the structural connection, reducing thermal stress without compromising overall structural strength.
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 design effectively mitigates thermal mismatch and stress between CMC and metallic components, enhancing the integration and performance of combustor components by allowing for relative movement and maintaining sealing functionality.
Implementation Method 1
the CMC parts and the metallic parts may have different coefficients of thermal expansion and therefore combining CMC parts with metallic parts in combustors can be challenging
Implementation Method 2
a damper disposed between the outer shell and at least one of the inner panels
Data Source
AI summary
Wall assemblies for a combustor of a gas turbine engine are disclosed. A wall assembly comprises an outer shell made of a metallic material, adjacent first and second inner panels mounted to the outer shell via an insert and a damper disposed between the outer shell and at least one of the first and second inner panels. The first and second inner panels may be spaced apart from the outer shell to define a double-wall configuration with the outer shell. The first and second inner panels may be made of a composite material. The insert may be made from substantially the same or other type of composite material.