Composite Airfoil Frangible Tip Design for Gas Turbine Rub
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Solution Overview
Problem
Existing composite airfoils in gas turbine engines face challenges with tip rub, leading to increased weight, complexity, and cost due to the need for reinforcing materials, which do not effectively prevent rotor unbalance during events like fan blade out (FBO).
Innovation Solution
The development of composite airfoils with frangible tips, featuring a body section with a higher fiber volume than the tip section, and a tip cap with tapered thickness walls, designed to fail under specific loading conditions, reducing rub and unbalance by allowing controlled disintegration of the tip section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fan casing is reinforced to accommodate blade rub, then the durability against blade rub is improved, but the weight and complexity of the fan module increase
Solution Approach 1:
The airfoil is divided into two distinct sections: a body section with high fiber volume for structural integrity and a tip section with low fiber volume for controlled failure. This segmentation allows the tip to fracture independently during rub events, protecting the main airfoil structure while reducing the need for extensive reinforcement of the entire fan module.
Solution Approach 2:
Different fiber volume ratios are applied to different regions of the airfoil. The body section uses high fiber volume (greater than 60%) for maximum strength and durability, while the tip section uses low fiber volume (less than 40%) to enable controlled frangibility. This local differentiation optimizes both protection against rub and avoidance of unnecessary reinforcement.
2Reliability
If the fan casing is reinforced to accommodate blade rub, then the durability against blade rub is improved, but the complexity of the fan module increases
Solution Approach 1:
The airfoil is divided into two distinct sections: a body section with high fiber volume for structural integrity and a tip section with low fiber volume for controlled failure. This segmentation allows the tip to fracture independently during rub events, protecting the main airfoil structure while reducing the need for extensive reinforcement of the entire fan module.
Solution Approach 2:
Different fiber volume ratios are applied to different regions of the airfoil. The body section uses high fiber volume (greater than 60%) for maximum strength and durability, while the tip section uses low fiber volume (less than 40%) to enable controlled frangibility. This local differentiation optimizes both protection against rub and avoidance of unnecessary reinforcement.
3Reliability
If reinforcing materials are added to the fan casing, then the resistance to blade rub is improved, but the cost of the fan module increases
Solution Approach 1:
The airfoil is divided into two distinct sections: a body section with high fiber volume for structural integrity and a tip section with low fiber volume for controlled failure. This segmentation allows the tip to fracture independently during rub events, protecting the main airfoil structure while reducing the need for extensive reinforcement of the entire fan module.
Solution Approach 2:
Different fiber volume ratios are applied to different regions of the airfoil. The body section uses high fiber volume (greater than 60%) for maximum strength and durability, while the tip section uses low fiber volume (less than 40%) to enable controlled frangibility. This local differentiation optimizes both protection against rub and avoidance of unnecessary reinforcement.
4Strength
If the tip section has high fiber volume, then the strength of the airfoil is improved, but the ability to prevent rotor unbalance during FBO events is reduced
Solution Approach 1:
The airfoil is divided into two distinct sections: a body section with high fiber volume for structural integrity and a tip section with low fiber volume for controlled failure. This segmentation allows the tip to fracture independently during rub events, protecting the main airfoil structure while reducing the need for extensive reinforcement of the entire fan module.
Solution Approach 2:
Different fiber volume ratios are applied to different regions of the airfoil. The body section uses high fiber volume (greater than 60%) for maximum strength and durability, while the tip section uses low fiber volume (less than 40%) to enable controlled frangibility. This local differentiation optimizes both protection against rub and avoidance of unnecessary reinforcement.
Data Source
AI summary
Composite airfoils and methods for forming composite airfoils are provided. For example, a composite airfoil of a gas turbine engine comprises opposite pressure and suction sides extending radially along a span from a root to a tip, which define opposite radial extremities of the airfoil. The composite airfoil further comprises a body section and a tip section, which includes the tip, that each extend radially along the span. The composite airfoil is formed from a composite material comprising fibers disposed in a matrix material. The tip section has a tip fiber volume, and the body section has a body fiber volume that is greater than the tip fiber volume. Another composite airfoil comprises a tip cap applied over the tip that tapers from a first end to a second end such that each of the pressure and suction side walls of the tip cap narrows from a first thickness to a second thickness.