Inverted CMC Shroud Hanger Assembly for Gas Turbine Engines
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Solution Overview
Problem
Ceramic matrix composite (CMC) materials used in gas turbine engines face challenges due to their low tensile ductility and mismatched thermal expansion coefficients with metal alloys, leading to stress concentrations and reduced component life when subjected to tensile or moment loads, particularly in high-temperature environments.
Innovation Solution
A two-piece CMC shroud hanger assembly with a forward and aft hanger portion, configured to clamp across a forward vertical wall of the shroud, utilizing a diagonal web member and mechanical fasteners to maintain the CMC material in compression, transferring nozzle loads through the shroud hanger assembly into the engine casing while sealing potential leakage points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC materials are used in high-temperature environments, then temperature capability and engine efficiency are improved, but stress concentrations develop due to thermal expansion mismatch leading to shortened component life
Solution Approach 1:
The patent changes the mechanical state parameter of the CMC shroud from tension to compression by inverting the hanger design. The inverted hanger allows the shroud to hang from the turbine nozzle rather than being supported from below, placing the CMC material in compression where it can better withstand thermal stresses and expansion mismatches, thereby improving component life in high-temperature environments
Solution Approach 2:
The patent applies inversion by flipping the conventional hanger configuration upside down. Instead of a traditional support structure bearing upward on the shroud, the inverted hanger allows the shroud to be suspended from the turbine nozzle, fundamentally changing the load direction and placing CMC materials in their more favorable compression state
2Temperature
If CMC materials are used instead of metallic materials, then temperature capability is improved, but tensile ductility and strain to failure are reduced
Solution Approach 1:
The patent inverts the conventional support configuration to place CMC materials in compression rather than tension. By allowing the shroud to hang from the turbine nozzle through the inverted hanger, the design exploits the superior compressive strength of CMC materials while avoiding their weakness in tensile loading
Solution Approach 2:
The patent changes the stress state parameter from tensile to compressive by inverting the hanger configuration. This parameter change allows the CMC material to operate in its stronger regime, effectively compensating for its lower tensile ductility compared to metallic materials
3Force
If complex hanger assemblies are used to transfer nozzle load, then load transfer capability is improved, but device complexity increases
Solution Approach 1:
The patent extracts the load transfer function from a complex multi-component hanger assembly and concentrates it into a single inverted hanger structure. This simplified design directly transfers the turbine nozzle load through the inverted hanger to the engine casing, eliminating the need for additional sealing components and complex arrangements
Solution Approach 2:
The inverted hanger assembly performs multiple functions simultaneously: it transfers the turbine nozzle load, provides sealing at the shroud interface, and maintains the shroud in compression. This multi-functionality eliminates the need for separate dedicated sealing components and complex load transfer mechanisms
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 design effectively maintains CMC components in compression, enhancing their strength and longevity by transferring loads directly through the shroud, thereby extending the service life of the shroud and hanger assemblies in a cost-effective manner.
Implementation Method 1
CMC materials have a coefficient of thermal expansion which differs significantly from metal alloys used as restraining supports or hangers for CMC type materials
Implementation Method 2
This design effectively maintains CMC components in compression, enhancing their strength and longevity by transferring loads directly through the shroud
Data Source
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AI summary
A shroud 206 and shroud hanger assembly 200 for a gas turbine engine and a method of transferring load from a ceramic matrix composite (CMC) shroud 206 to a CMC shroud hanger assembly 200 are provided. The shroud 206 and shroud hanger assembly 200 includes a shroud hanger assembly 200 formed of a first material having a first coefficient of thermal expansion, the shroud hanger assembly 200 having a forward hanger portion 202 and a separate aftward hanger portion 204 and a shroud 206 formed of a second material having a second coefficient of thermal expansion, the forward hanger portion 202 and the aftward hanger portion 204 configured to couple together to clamp across a forward radially extending wall 208 of the shroud 206.