Gas Turbine Flowpath Assembly Using Segmented CMC Ducts
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Solution Overview
Problem
Ceramic matrix composites (CMCs) used in gas turbine engines face challenges due to their difficulty in fabrication and mechanical fastening, low tensile ductility, and mismatched thermal expansion coefficients compared to metal alloys, making them hard to substitute directly for metallic components in flowpath structures.
Innovation Solution
A flowpath assembly is designed using an array of ducts with a perimeter wall structure and a support structure, allowing for the assembly of CMCs in configurations such as rings and arrays, which can include annular central members, radial members, and rings to position and maintain ducts, thereby facilitating their use in gas turbine engines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If CMC materials are used to replace metal alloys in flowpath structures, then weight is reduced, but ease of manufacture and mechanical fastening capability deteriorates
Solution Approach 1:
The flowpath structure is divided into multiple separate duct components that can be individually manufactured from CMC materials using appropriate fabrication processes, then assembled together using the support structure with fastening elements
Solution Approach 2:
A support structure acts as an intermediary component between the CMC ducts, providing a framework that facilitates assembly and mechanical fastening of the CMC components without requiring the CMC material itself to be easily fastened
2Weight of moving object
If CMC materials are used to replace metal alloys in flowpath structures, then weight is reduced, but tensile ductility and strain to failure deteriorates
Solution Approach 1:
The design changes the structural parameters by using a distributed array of individual ducts supported by a support structure, which alters the load distribution and stress patterns to compensate for the lower tensile ductility of CMC materials
Solution Approach 2:
By segmenting the flowpath into multiple individual ducts, the structure can better manage and distribute stresses, preventing catastrophic failure and compensating for the lower strain to failure of CMC materials
3Weight of moving object
If CMC materials are used to replace metal alloys in flowpath structures, then weight is reduced, but thermal expansion compatibility deteriorates
Solution Approach 1:
The support structure serves as a thermal expansion intermediary, providing a mechanical framework that can accommodate the different thermal expansion characteristics of CMC ducts while maintaining overall structural integrity across temperature variations
Solution Approach 2:
Segmenting the structure into individual ducts mounted on a support framework allows each component to expand and contract independently according to its thermal properties, reducing thermal stress and compatibility issues
4Ease of manufacture
If ducts are assembled into an array configuration with support structure, then CMC materials can be effectively used despite manufacturing challenges, but device complexity increases
Solution Approach 1:
The support structure performs multiple functions simultaneously: it provides mechanical support for the ducts, enables assembly and disassembly, facilitates fastening of CMC components, and accommodates thermal expansion, thereby managing complexity through multi-functionality
Data Source
AI summary
A flowpath apparatus for a gas turbine engine includes: a plurality of ducts arranged in an array, each duct including a peripheral wall structure having a closed perimeter that defines a flow channel from an upstream end to a downstream end thereof; and a support structure positioning a the plurality of ducts in an array configuration.