Compression Ring for Exhaust Nozzle Attachment
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Solution Overview
Problem
The challenge in attaching exhaust components made of ceramic or ceramic matrix composite (CMC) materials to metallic structures in gas turbine engines lies in the disparate thermal expansion properties, leading to interlaminar tensile stresses and potential delamination, especially under high-temperature conditions.
Innovation Solution
The proposed solution involves a radial attachment flange and inner/outer rings with specific thermal expansion coefficients, applying compressive loads to manage thermal expansion and stress, and using coatings to protect materials from oxidation. The radial inner ring expands more than the flange, applying outward compressive force, while the outer ring expands less, applying inward compressive force, with both rings secured via bolts through apertures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ceramic or CMC materials are used for exhaust components to withstand high temperatures, then temperature resistance is improved, but thermal expansion mismatch with metallic structures causes interlaminar tensile stresses and potential delamination
Solution Approach 1:
The patent applies parameter changes by modifying the stress state through mechanical preloading. Compression rings are installed to apply compressive forces to the CMC component, changing the stress parameters from tensile to compressive. This compensates for the thermal expansion mismatch that would otherwise create damaging interlaminar tensile stresses during thermal cycling.
Solution Approach 2:
The patent implements preliminary anti-action by applying compressive preloads before thermal exposure occurs. The compression rings are installed and adjusted to create initial compressive stresses that counteract the tensile stresses that will develop during thermal expansion. This preliminary counter-action prevents delamination before the thermal problem manifests.
2Ease of manufacture
If metallic components are used for attachment structures, then ease of manufacture is improved, but greater thermal expansion compared to ceramic components creates stress and movement during operation
Solution Approach 1:
The patent introduces compression rings as intermediary elements between the metallic attachment structures and the CMC exhaust component. These rings act as mediators that accommodate the dimensional differences caused by thermal expansion mismatch. The intermediaries allow the metallic structures to expand freely while maintaining stable attachment to the CMC component through controlled compressive contact.
3Stability of the object's composition
If compression rings with higher thermal expansion coefficient than the CMC component are used, then thermal expansion mismatch is compensated, but additional stress management requirements increase device complexity
Solution Approach 1:
The patent applies local quality by creating zones of different mechanical properties within the attachment system. The compression rings have specific local characteristics (higher thermal expansion coefficient) that are strategically placed at the interface between metallic and CMC components. This localized property differentiation allows thermal expansion compensation without requiring the entire attachment system to be complex.
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 configuration effectively mitigates thermal expansion discrepancies, reduces interlaminar stresses, and enhances the structural integrity of CMC components by applying radial compressive and tensile forces, thereby preventing delamination and improving the durability of exhaust system components.
Implementation Method 1
the radially inner ring is configured to apply a radially outwardly facing compressive load against the radially inner surface of the radial attachment flange upon being exposed to a hot exhaust stream
Implementation Method 2
the radially outer ring is configured to apply a radially inwardly facing compressive load against the radially outer surface of the radial attachment flange upon being exposed to elevated temperatures
Implementation Method 3
the radially outer ring includes a coating configured to protect a parent material from oxidation or oxidative erosion due to exposure to a hot exhaust stream
Data Source
Figure 1
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Figure 2B
AI summary
An attachment system for an exhaust component is disclosed. In various embodiments, the attachment system includes a radial attachment flange of the exhaust component; and a radial ring having at least one of a radially outer surface configured for engagement with a radially inner surface of the radial attachment flange or a radially inner surface configured for engagement with a radially outer surface of the radial attachment flange.