CMC Gas Turbine Shroud Assembly Segmentation
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Solution Overview
Problem
The shroud in a gas turbine, made of ceramic matrix composite (CMC), faces challenges in forming complex three-dimensional shapes while maintaining strength, and existing solutions struggle with heat resistance and load distribution, leading to difficulties in manufacturing and stabilizing tip clearance.
Innovation Solution
A shroud assembly design featuring a CMC shroud main body and insertion member that can be formed in simple shapes, with the insertion member made of CMC, which contacts the holder from the inner side to secure positioning and prevent vibration, and a holder made of metal to protect it from heat, while the CMC shroud covers the holder to enhance heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the shroud is formed in a complex three-dimensional shape to cover the inner peripheral surface of the support, then the shroud can properly fit the support structure, but it becomes difficult to form the shape using CMC while maintaining material strength
Solution Approach 1:
The shroud is divided into multiple segments that can be manufactured separately as simpler shapes and then assembled together to form the complete complex three-dimensional structure, making CMC manufacturing feasible while maintaining strength
Solution Approach 2:
The shroud is designed to cover the holder from the radially inner side, creating a nested structure where the shroud envelops the holder, allowing the shroud to conform to the support structure while maintaining its own manufacturable geometry
2Reliability
If a hook portion with large curvature is provided at the CMC shroud to attach to the support, then the shroud can be secured to the support, but it becomes difficult to form the long fiber preform required for CMC manufacturing
Solution Approach 1:
The attachment function is segmented from the shroud body, with the insertion member serving as a separate attachment component that can be manufactured with simpler geometry suitable for CMC preform fabrication, while still providing secure attachment capability
Solution Approach 2:
Instead of forming the hook portion directly in the CMC shroud, the design inverts the approach by using a separate insertion member that engages with the shroud, allowing the CMC shroud to maintain its manufacturable simple shape while achieving secure attachment through the insertion member
3Ease of operation
If the support exposing to thermal space is used to hold the CMC shroud, then the support can be easily accessed for assembly, but heat deterioration of the support progresses
Solution Approach 1:
The holder serves as an intermediary component between the support and the CMC shroud, positioned at the radially outer side to bear the brunt of thermal exposure and protect the support from direct heat contact, while still allowing easy assembly access
4Reliability
If a rod-shaped metal fixture is inserted into a fixing hole of the CMC shroud to fix it to the support, then the shroud can be securely attached, but the load concentrates on the peripheral edge of the fixing hole and acts in a shearing direction, compromising CMC strength
Solution Approach 1:
The design inverts the attachment approach by having the insertion member engage with the shroud from the radially inner side rather than inserting into the shroud, reversing the load path to act perpendicular to the shroud thickness where CMC exhibits superior strength
Solution Approach 2:
The attachment geometry is changed from a point-contact insertion method to a surface-contact method where the insertion member contacts both the peripheral edge and the flange portion, distributing the load over a larger area and changing the load direction to perpendicular compression rather than shear
5Strength
If the CMC shroud is made thin to maintain strength, then the material strength is preserved, but the tip clearance stabilization becomes difficult
Solution Approach 1:
The design adds the axial dimension to the attachment mechanism by incorporating a flange portion that extends axially, allowing the thin CMC shroud to achieve stable positioning through multi-dimensional contact (radial edge contact plus axial flange contact) rather than relying solely on radial thickness
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A shroud assembly of a gas turbine includes: a holder including an insertion hole; a plate-shaped shroud main body covering the holder from a radially inner side and made of a ceramic matrix composite; and a plate-shaped insertion member made of the ceramic matrix composite. The shroud main body includes a main body portion, a flange portion, and an insertion hole formed at the main body portion. The insertion member includes: an insertion portion inserted into the insertion hole of the shroud main body and the insertion hole of the holder in an axial direction; and a head portion arranged at the radially inner side of the flange portion of the shroud main body and configured to be brought into contact with the flange portion from the radially inner side.