Composite Rotor Blade Attachment Using Plug and Clamp
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Solution Overview
Problem
Composite rotor blades in gas turbine engines face challenges in force and load transfer to metallic rotor disks, leading to potential damage and compromised strength due to the difference in materials and the machining of traditional 'fir-tree' shapes.
Innovation Solution
A composite rotor blade attachment system featuring a plug, looped portion, and clamp design that distributes compression loads over a larger area, using a metallic or ceramic plug and a looped portion made of ceramic matrix composite, with a clamp that partially surrounds the looped portion to securely attach the blade to the rotor disk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a traditional 'fir-tree' shape is machined on the root section of a composite rotor blade, then the blade can be attached to the rotor disk, but the strength of the composite rotor blade is compromised
Solution Approach 1:
The attachment system is divided into separate components: a metallic or ceramic plug inserted into the composite blade root, and a separate clamp that engages with the plug. This segmentation allows the composite blade to avoid direct machining while still achieving secure attachment to the rotor disk through the plug-clamp mechanism.
Solution Approach 2:
A metallic or ceramic plug serves as an intermediary element between the composite rotor blade and the rotor disk. The plug is inserted into the composite blade root and provides a hardened interface that can be clamped to the rotor disk, thereby protecting the composite material from direct mechanical stress and machining damage while enabling secure attachment.
2Weight of moving object
If composite materials are used for rotor blades, then weight is reduced and strength-to-weight ratio is improved, but force and load transfer to metallic rotor disks causes damage
Solution Approach 1:
The metallic or ceramic plug acts as a mediator that facilitates load transfer from the lightweight composite blade to the metallic rotor disk. The plug's higher strength and stiffness properties allow it to withstand the compression loads and force transfers that would otherwise damage the composite blade root, enabling the use of composite materials while maintaining reliability.
Solution Approach 2:
The attachment system combines different materials (composite blade, metallic/ceramic plug, and clamp) to leverage the advantages of each. The composite blade provides low weight and high strength-to-weight ratio, while the metallic or ceramic plug provides the necessary strength and stiffness for load transfer, creating a hybrid attachment system that resolves the material incompatibility issue.
Data Source
Figure 1
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AI summary
A rotor blade (24) for a gas turbine engine (10) includes an airfoil (28) that extends in span between a tip (30) and a root (32) opposite from the tip (30). The root (32) includes a plug (34), a looped portion (36) that surrounds the plug (34) and a clamp (38). The clamp (38) contacts only a portion of the looped portion (36) on an opposite side of the looped portion (36) from the plug (34).