Frangible Sheath for Gas Turbine Fan Blade Impact Resistance
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Solution Overview
Problem
Existing gas turbine fan blades made from lightweight materials lack the structural strength to effectively resist bird or debris strikes, leading to damage, reduced lifespan, and efficiency issues.
Innovation Solution
A sheath formed from a brittle material, such as an aluminum alloy or fiber-reinforced composite, is applied along the leading edge of the fan blades to absorb impact energy, shatter, or crack instead of bending, thereby protecting the blade from global deflection and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If lightweight materials are used for fan blades, then weight is reduced, but structural strength to resist debris strike is insufficient
Solution Approach 1:
The fan blade is constructed as a composite structure combining lightweight materials (such as aluminum alloys or composites) with a frangible sheath made of brittle material. This composite approach allows the blade to achieve both weight reduction and improved debris strike resistance, as the brittle sheath provides protective functionality while the lightweight core material maintains low weight.
Solution Approach 2:
The fan blade is divided into functional segments: a lightweight core structure and a separate frangible sheath layer. This segmentation allows each component to be optimized independently - the core for weight reduction and the sheath for protective function - resolving the contradiction between lightweight design and strike resistance.
2Object-affected harmful factors
If a ductile sheath is used to protect the blade, then deformation absorbs energy, but global deflection and damage still occur
Solution Approach 1:
The protective function is extracted from the main blade structure and implemented as a separate frangible sheath. This sheath is designed to fail locally through cracking rather than allowing global deformation of the blade, thereby protecting the blade's structural integrity while still providing debris strike protection.
Solution Approach 2:
The frangible sheath acts as a sacrificial protective layer designed to crack and fail locally upon impact. This disposable-like approach protects the valuable blade structure - the sheath takes the damage in the form of localized cracks rather than allowing the expensive blade to suffer global deflection or damage.
3Strength
If a frangible sheath is used, then local cracking protects the blade, but the sheath itself fails
Solution Approach 1:
The inherent brittleness and susceptibility to cracking of the sheath material is converted from a weakness into a protective mechanism. When debris strikes, the sheath is designed to crack locally rather than transmit force to the blade, transforming what would normally be a failure mode into a protective function that preserves blade integrity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The brittle sheath effectively absorbs impact energy, reducing global damage to the fan blades and maintaining engine operability by localizing the impact effects, thus enhancing the structural integrity of lightweight materials used in fan blades.
Implementation Method 1
The sheath is formed from a brittle material having a molecular structure causing the brittle material to shatter or crack upon impact as opposed to bending or deforming
Data Source
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AI summary
In accordance with one aspect of the disclosure, a rotor for a gas turbine engine is disclosed. The rotor may include a rotor disk and a blade extending radially outward from the rotor disk. The blade may have a leading edge and a sheath may extend along the leading edge of the blade. The sheath may be formed from a brittle material.