CMC Airfoil to Metallic Support Load Transfer
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Solution Overview
Problem
Ceramic matrix composite (CMC) nozzle components in gas turbine engines face shortened life due to localized stresses from moment stresses, differential thermal growth, and concentrated loading at material interfaces with metallic components, leading to mechanical property limitations and reduced durability.
Innovation Solution
The integration of radially outwardly-facing non-compression load-bearing features, such as wedge-shaped cross-sections and complementary mating surfaces, allows for effective load transfer from CMC vane assemblies to metallic support members, distributing forces orthogonally and reducing stress concentrations, thereby enhancing the structural integrity and longevity of CMC components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC materials are used for HPT nozzles to operate at higher temperatures, then engine efficiency is improved, but stress concentrations develop at material interfaces leading to shortened component life
Solution Approach 1:
A metallic transition band is introduced as an intermediary element between the CMC airfoil and the metallic support structure. This transition band serves as a mediator that gradually transitions from CMC to metallic material, distributing thermal and mechanical stresses across the interface rather than concentrating them at a single boundary. The transition band includes a first region with CMC material and a second region with metallic material, creating a gradual material property transition that reduces stress concentrations.
Solution Approach 2:
The invention changes the material composition parameter along the length of the transition band, creating a gradient from pure CMC to pure metallic material. This parameter change allows the structure to accommodate differential thermal expansion between CMC and metallic materials while maintaining structural integrity. The transition band's material properties vary continuously or in discrete steps to optimize stress distribution across the interface.
2Temperature
If CMC materials are used for HPT nozzles, then temperature capability is improved, but differential thermal growth between CMC and metallic parts causes localized stresses
Solution Approach 1:
The transition band is designed with local quality variations, where different sections have different material compositions tailored to specific stress and thermal conditions. The first region contains CMC material optimized for high-temperature exposure, while the second region contains metallic material optimized for structural support and thermal compatibility with the support structure. This local quality differentiation allows each section to handle its specific environmental conditions optimally.
Solution Approach 2:
The transition band itself is a composite structure combining CMC and metallic materials in a single integrated component. This composite approach allows the transition band to simultaneously exhibit the high-temperature resistance of CMC and the ductility and thermal compatibility of metallic materials. The composite structure is designed to manage the differential thermal expansion between the CMC airfoil and the metallic support structure by providing a gradual transition in material properties.
3Temperature
If CMC materials are used for HPT nozzles, then higher operating temperatures are achieved, but moment stresses exceed CMC material capabilities
Solution Approach 1:
The metallic portion of the transition band acts as a mediator that absorbs and redistributes moment stresses away from the brittle CMC airfoil. The metallic material's higher ductility allows it to accommodate bending and moment loads that would be problematic for the CMC material. The transition band's design ensures that moment stresses are transferred gradually from the CMC airfoil through the transition band to the metallic support structure, preventing stress concentrations that would exceed CMC material capabilities.
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 solution extends the service life of CMC nozzle components by efficiently managing thermal expansion differences and load distribution, ensuring reliable operation in high-temperature environments while maintaining structural integrity and reducing stress concentrations.
Implementation Method 1
The load transfer feature includes a wedge-shaped cross-section... distributing forces orthogonally and reducing stress concentrations
Implementation Method 2
CMC materials have a coefficient of thermal expansion which differs significantly from metal alloys used as restraining supports or hangers for CMC type materials
Data Source
AI summary
An airfoil assembly for a gas turbine engine and a method of transferring load from the ceramic matrix composite (CMC) airfoil assembly to a metallic vane assembly support member are provided. The airfoil assembly includes a forward end and an aft end with respect to an axial direction of the gas turbine engine. The airfoil assembly includes a radially outer end component, a radially inner end component, and a hollow airfoil body extending therebetween. The radially outer end component including a radially outwardly-facing end surface having a non-compression load-bearing feature extending radially outwardly and formed integrally with the outer end component, the load-bearing feature configured to mate with a complementary feature formed in a radially inner surface of a first airfoil assembly support structure and selectively positioned orthogonally to a force imparted into the airfoil assembly.