Triangular Pin Attachment for CMC Turbine Blades
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Solution Overview
Problem
The existing attachment mechanisms for ceramic matrix composite (CMC) blades in gas turbine engines, such as the pin and clevis type, often result in high stresses due to line contact, which can be undesirable and may not effectively utilize the strength of the CMC material.
Innovation Solution
A triangular cross-sectional attachment pin is used to provide a surface contact interface between the pin and the blade, minimizing stresses and avoiding reliance on the interlaminar capability of the CMC material, with the pin extending from the pressure side of the blade around a pin hole to the suction side, ensuring a surface contact interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a round cross-section pin is used for attachment, then the attachment mechanism is simple to manufacture, but the contact stress between the pin and blade becomes excessively high due to line contact
Solution Approach 1:
The pin cross-section is changed from a round shape (1D line contact) to a triangular shape with flat surfaces (2D surface contact). This dimensional change in the contact interface transforms the stress distribution from concentrated line contact to distributed surface contact, reducing contact stress while maintaining manufacturing feasibility through standard machining processes.
Solution Approach 2:
The geometric parameters of the pin cross-section are changed from circular to triangular with specific flat surface orientations. This parameter change modifies the contact mechanics by increasing the contact area with the blade, thereby reducing contact stress without significantly complicating the manufacturing process.
2Strength
If continuous fiber plies are used in CMC blades, then the blade strength is maximized in the fiber direction, but the attachment mechanism creates high stresses that the interlaminar material cannot withstand
Solution Approach 1:
The triangular pin design creates localized surface contact zones on the blade that are optimized for stress distribution. The flat surfaces of the triangular pin contact specific regions of the blade, creating localized quality in the stress distribution that protects the interlaminar regions while maintaining overall blade strength through the continuous fiber architecture.
Solution Approach 2:
The solution utilizes the composite nature of CMC materials by designing an attachment mechanism that works synergistically with the layered structure. The triangular pin's flat surfaces contact the composite blage, distributing loads across multiple plies without concentrating stresses at interlaminar interfaces, thereby maintaining both blade strength and attachment reliability.
3Force
If a pin and clevis attachment mechanism is used, then the blade can be securely attached to the rotor disk, but the line contact creates undesirably high crush and contact stresses
Solution Approach 1:
The contact interface is transformed from 1D line contact to 2D surface contact by using a triangular pin cross-section with flat surfaces. This dimensional change maintains the attachment force capability while distributing the crush stress over a larger surface area, reducing the stress magnitude without compromising the secure attachment.
Data Source
AI summary
A turbine blade assembly for a gas turbine engine is provided. The turbine rotor blade assembly includes a turbine rotor blade and an attachment pin, and the turbine rotor blade and attachment pin have features for providing a surface interface between the blade and pin. In particular, the attachment pin has a triangular cross-sectional shape, and the blade defines a pin hole for receipt of the attachment pin. An attachment pin for attaching a turbine rotor blade to a turbine rotor disk of a gas turbine engine also is provided. The attachment pin includes a body defining at least one planar surface, and the planar surface provides a surface contact interface between the attachment pin and the turbine rotor blade.