Unitary CMC Flow Path Assembly for Gas Turbine Thermal Expansion
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Solution Overview
Problem
Gas turbine engines face complexity, weight, and leakage issues due to the use of separate components for the inner and outer boundaries of the flow path, which can lead to thermal expansion mismatches between ceramic matrix composite (CMC) and metallic materials, affecting the positioning and efficiency of the flow path assembly.
Innovation Solution
A flow path assembly with a unitary outer wall and an integrated inner band, utilizing a hub and spoke configuration with nozzle airfoils to position and restrain the inner band, and optionally a tiered hub and spoke configuration with a backing ring, allowing for thermal growth while maintaining proper positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate components are used to form the inner and outer boundaries of the flow path, then the assembly can be manufactured from different materials, but the number of parts increases requiring seals at each interface which increases complexity and weight without eliminating leakage points
Solution Approach 1:
The patent combines the inner band and outer band into a single unitary flow path assembly made from CMC material, eliminating the need for separate components and seals at interfaces. This merging reduces the number of parts while maintaining the ability to select appropriate materials for the application.
2Adaptability or versatility
If separate components are used for the flow path boundaries, then material diversity is enabled, but seals are required at each interface to minimize leakage which increases complexity and weight
Solution Approach 1:
By merging the inner and outer boundaries into a single unitary CMC flow path assembly, the patent eliminates interface seals that would be required between separate components. This unified structure inherently prevents leakage without requiring additional sealing mechanisms.
3Temperature
If CMC flow path assembly is used, then high temperature resistance is improved, but thermal expansion mismatch with non-CMC support components affects positioning of the flow path assembly
Solution Approach 1:
The patent applies local quality by creating a unitary CMC flow path assembly that is thermally coupled to the support structure, allowing the CMC components to expand freely with thermal growth while maintaining their relative positioning through the integrated design.
Solution Approach 2:
The patent addresses thermal expansion by designing the flow path assembly to accommodate thermal growth of CMC materials. The unitary construction allows for controlled thermal expansion while maintaining positioning accuracy through the integrated structure that moves as a single thermal unit.
4Device complexity
If a unitary flow path assembly is used, then the number of components and weight are reduced, but the assembly must accommodate thermal growth of CMC materials while maintaining proper positioning
Solution Approach 1:
The patent applies dynamics by designing the unitary flow path assembly to accommodate thermal growth. The integrated structure allows for controlled expansion and movement while maintaining proper positioning through the inherent flexibility and thermal coupling of the CMC material throughout the assembly.
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 reduces the number of components, weight, and leakage, while allowing for thermal expansion, thereby improving the positioning and efficiency of the flow path assembly and reducing operational complexity.
Implementation Method 1
CMC materials have a different rate of thermal expansion than, e.g., metallic materials such as metals or metal alloys. Therefore, where components supporting the CMC flow path assembly are made from one or more non-CMC materials, the CMC flow path assembly and the support components may thermally expand at different rates
Data Source
AI summary
Flow path assemblies and methods for assembling a flow path assembly of a gas turbine engine are provided. For example, a flow path assembly comprises a unitary outer wall including combustor and turbine portions that are integrally formed as a single unitary structure; a single piece, generally annular inner band; and a plurality of nozzle airfoils extending from the unitary outer wall to the inner band. Each nozzle airfoil interfaces with the inner band to position the inner band within the assembly. An exemplary assembly method comprises inserting an inner band into a flow path having a unitary outer wall as its outer boundary; inserting a plurality of nozzle airfoils into the flow path; and securing the nozzle airfoils with respect to the unitary outer wall. The inner band interfaces with an inner end of each nozzle airfoil to radially locate the inner band within the flow path.