Ellipsoid Attachment Pin for CMC Blade Outer Air Seal
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Solution Overview
Problem
Existing attachment pins for ceramic matrix composite (CMC) blade outer air seal (BOAS) segments in gas turbine engines concentrate load on the edge of CMC holes, leading to bending moments and reduced ultimate strength due to differences in curvature between the CMC segments and the carrier, potentially causing part fracture.
Innovation Solution
A unitary attachment pin with an ellipsoid portion is used, which secures the BOAS segment to the carrier by extending through holes in radially inwardly extending tabs and an aperture, distributing the load and maintaining contact across changing curvatures, thereby reducing peak stresses and preventing bending moments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional attachment pin is used to secure CMC BOAS segments to the carrier, then the segments are held in place, but the load concentrates on the edge of CMC holes causing bending moments and reduced ultimate strength
Solution Approach 1:
The attachment pin incorporates an ellipsoid portion with a curved surface that contacts the radially extending wall of the CMC segment. This curved geometry allows the pin to accommodate differences in curvature between the CMC segment and carrier, distributing the load along the curved contact surface rather than concentrating it at a single point, thereby eliminating bending moments and improving both strength and reliability
2Adaptability or versatility
If the CMC segments and carrier have different curvatures, then the assembly can accommodate thermal expansion differences, but conventional pins create bending moments due to this curvature mismatch
Solution Approach 1:
The ellipsoid portion of the pin provides a curved contact surface that can adapt to the curvature differences between the CMC segment and carrier. This allows the assembly to accommodate thermal expansion differences while maintaining uniform contact and distributing stresses, eliminating the bending moments that would otherwise occur with straight pins
3Reliability
If conventional attachment pins are used, then the BOAS segments are secured to the carrier, but peak stresses are concentrated leading to potential fracture
Solution Approach 1:
The curved surface of the ellipsoid portion distributes the attachment load along its length, reducing peak stresses at any single point. This load distribution improves the durability and reliability of the CMC components by preventing stress concentration that would lead to fracture
Data Source
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AI summary
A flow path component assembly includes a carrier (112) that has at least one radially extending tab (114; 116). The flow path component (104) has a base portion (124) and a first wall (120) that extends radially from the base portion (124). The first wall (120) has an aperture (130). A pin (150) extends through a hole (113; 118) in the radially extending tab (114; 116) and the aperture (130). The pin (150) has an ellipsoid portion (156) between a first end (152) and a second end (154). Also, a turbine section (28) for a gas turbine engine (20), comprises a turbine blade (102) extending radially outwardly to a radially outer tip (103) and for rotation about an axis of rotation (A); a flow path component (104) having a plurality of segments (105) is mounted on a carrier (112) and arranged circumferentially about the axis of rotation (A) , at least one of the plurality of segments (105) having a radially extending wall (120, 122) with an aperture (130); and a pin (150) extending through the aperture (130) and a hole (113, 118) in the carrier (112), the pin (150) having an ellipsoid portion between a first end (152) and a second end (154).