Gas Turbine Nozzle Airfoil Decoupled from Flow Path Boundary
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Solution Overview
Problem
In gas turbine engines, nozzle airfoils bonded to the flow path boundary walls experience stress concentrations that exceed the material capability of high-temperature composite materials like CMCs, limiting their use despite their temperature advantages.
Innovation Solution
The nozzle airfoils are decoupled from the flow path boundary walls and attached via caps and attachment members, allowing loads to be transferred through a separate structure, reducing stress concentrations and enabling controlled cooling or purge flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nozzle airfoils are bonded to flow path boundary walls, then structural support and load transfer are achieved, but stress concentrations exceed the material capability of CMC materials
Solution Approach 1:
The airfoil is segmented into multiple parts: the main airfoil body and a tip section. The tip section is separated from the boundary wall and supported by a wire or rod that passes through the airfoil, allowing the tip to be decoupled from the wall while maintaining structural integrity and reducing stress concentrations at the bonding interface.
Solution Approach 2:
A wire or rod acts as an intermediary element between the airfoil tip and the boundary wall. This intermediary transfers loads from the airfoil tip through the wire/rod to the wall, avoiding direct bonding of the CMC airfoil to the wall and thereby reducing stress concentrations at the interface.
2Temperature
If CMC materials are used for nozzle airfoils, then temperature capability is improved, but stress concentration at bonded connections limits their use
Solution Approach 1:
By segmenting the airfoil into a main body and a tip section connected by a wire/rod, the design allows CMC materials to be used in the airfoil where high temperature capability is needed, while the wire/rod connection avoids creating stress concentrations that would compromise the CMC material's strength.
Solution Approach 2:
The wire or rod serves as an intermediary that transfers loads away from the CMC airfoil material at the bonding interface, enabling the use of CMC materials in high-temperature environments without the stress concentration problem that would otherwise limit their strength and reliability.
3Reliability
If airfoils are decoupled from flow path boundary walls, then stress concentrations are reduced, but additional structures (caps and attachment members) are required
Solution Approach 1:
The wire or rod serving as the attachment member performs multiple functions: it supports the decoupled airfoil tip, transfers loads from the tip to the boundary wall, and eliminates the need for separate caps or complex bonding structures. This multi-functionality reduces overall device complexity while maintaining stress management benefits.
Data Source
AI summary
Flow path assemblies for gas turbine engines are provided. For example, a flow path assembly defining a flow path through a gas turbine engine, as well as axial and radial directions that are orthogonal to one another and a circumferential direction extending about the axial direction, comprises a nozzle airfoil having a first end opposite a second end and a wall defining a flow path boundary. The wall has an opening therein through which the second end of the nozzle airfoil protrudes such that the second end extends outside of the flow path. The flow path assembly further comprises a cap extending over the second end of the nozzle airfoil and an attachment member extending through the second end and the cap to attach the second end to the cap. Other embodiments of a flow path assembly having nozzle airfoils decoupled from the flow path boundary also are provided.