CMC Turbine Vane Attachment Radial Offset Design
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Solution Overview
Problem
The connection between ceramic matrix composite distributors and metal support in turbomachines faces challenges due to significant prestress requirements, leading to premature wear at contact zones and stress concentrations, especially under thermal and aerodynamic forces.
Innovation Solution
A segmented annular distributor sector with a central flange and side flanges, and a metallic support sector with central and lateral hooks, where the central flange and hooks are radially offset, allowing for radial contact and support without high prestress, distributing external stresses homogeneously across the edges and hooks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high prestress is applied to the connection between ceramic matrix composite distributor and metal support, then the connection reliability is improved, but the mechanical strength of the ceramic matrix composite distributor deteriorates leading to premature wear
Solution Approach 1:
The connection interface is segmented into multiple contact zones: a first contact zone for the upstream rim and upstream hook, and a second contact zone for the downstream rim and downstream hook. This segmentation distributes the prestress across multiple locations rather than concentrating it at a single interface, reducing the stress burden on the ceramic matrix composite material while maintaining overall connection reliability.
Solution Approach 2:
The ceramic matrix composite distributor is designed with locally optimized features at the connection interface, including specific rim geometries and thickness variations at the upstream and downstream ends. These local structural adaptations enable the material to better withstand the applied prestress without premature wear, addressing the strength limitation at critical locations while preserving the overall lightweight advantage of using ceramic matrix composite.
2Stability of the object's composition
If high prestress is applied to prevent flange separation under thermal and aerodynamic forces, then the connection stability is improved, but the localized forces at interfaces increase causing premature wear
Solution Approach 1:
The connection interface is divided into upstream and downstream contact zones, each handling specific portions of the thermal and aerodynamic loads. This segmentation prevents concentration of localized forces at a single interface by distributing them across multiple separated contact regions, thereby reducing wear while maintaining connection stability under operational forces.
Solution Approach 2:
The connection design incorporates axial extension of the upstream and downstream rims, adding an axial dimension to the force distribution. By extending the contact surfaces axially, the interface area is increased, which distributes the localized forces over a larger area and reduces stress concentration, thereby preventing premature wear while maintaining stability against thermal expansion and aerodynamic forces.
Data Source
Figure 1~2
Figure 3~5
AI summary
Sector (7), made of ceramic matrix composite, of a stator (4) of a turbine (1) of a turbomachine (2) comprising an outer platform (8) and an inner platform (9) that are connected via at least one vane, said outer platform (8) comprising means (10) for attaching to a sector (11) of a metallic support (12), the attachment means (10) comprising at least one central rim and two lateral rims, said central rim being radially offset with respect to said lateral rims along a directrix line such that the central rim is radially on one side of said directrix line and the lateral rims on the other, said central rim and said central hook bearing radially against one another and being located radially on either side of said directrix line, said lateral rim and said corresponding lateral hook bearing radially against one another and being located radially on either side of said directrix line.