Assembled Ring Shroud for Gas Turbine Blade Outer Air Seal
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Solution Overview
Problem
The exclusive use of unidirectional Ceramic Matrix Composite (CMC) plies in blade outer air seals of gas turbine engines limits the creation of full hoop rings due to stress concentrations and tensile stress issues, particularly affecting the end ply, which restricts the allowable stress significantly.
Innovation Solution
An assembled ring shroud with multiple layers, including a first ring layer, a key layer, a second ring layer, and a cover, all made of CMC materials with unidirectional fibers oriented tangentially or perpendicularly to the circumferential axis, providing enhanced strength and resistance to both compressive hoop and tensile stresses by increasing fiber density and eliminating weak interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If unidirectional CMC plies are used exclusively, then the structure can be simple and manufacturing can be easier, but the strength and allowable stress are significantly limited due to stress concentrations in the end ply
Solution Approach 1:
The ring shroud is divided into multiple discrete unidirectional CMC plies stacked in sequence, each ply being a separate manufacturable unit. This segmentation allows the end ply stress concentration issue to be isolated to specific layers rather than affecting the entire structure, while maintaining manufacturing simplicity for each individual ply.
Solution Approach 2:
Multiple unidirectional CMC plies are combined to form a composite structure where the collective arrangement of plies provides enhanced strength compared to single-ply configurations. The composite nature allows stress distribution across multiple layers, mitigating the limitations of individual plies.
2Strength
If a full hoop CMC ring is created, then the structural integrity should be improved, but the end ply contains stress concentrations that limit the allowable stress significantly
Solution Approach 1:
The hoop ring is segmented into multiple plies with different orientations and positions. By dividing the structure into discrete plies, the stress concentration in any single end ply is isolated and does not compromise the overall structural integrity of the complete ring structure.
Solution Approach 2:
Different plies are positioned and oriented to provide locally optimized properties. The end plies are specifically positioned where stress concentrations occur, while intermediate plies provide structural continuity. This local quality differentiation allows the structure to maintain high allowable stress despite localized stress concentrations.
Data Source
Figure 1
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Figure 3A
AI summary
An assembled ring shroud (205) is provided. The assembled ring shroud (205) may comprise a cover (310), a first ring layer (320), a key layer (330), and a second ring layer (340). The cover (310) may operatively wrap around, contain, and secure the first ring layer (320), the key layer (330), and the second ring layer (340). The key layer (330) may comprise a key (335) that may act for position and anti-rotation. The key layer (330) may comprise spacers (331) to hold the keys (335) in place. The first ring layer (320) and the second ring layer (340) may be configured to provide further strength and support to the assembled ring shroud (205).