Segmented Metallic Fan Blade Tip for Controlled Shroud Impact
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Solution Overview
Problem
Conventional turbofan engines face significant damage due to rotary unbalance caused by fan blade contact with the shroud, which is exacerbated by the weight and inefficiency of traditional metallic honeycomb trench filler used for containment.
Innovation Solution
The fan blade is designed with a tip region made of a weaker material that separates quickly from the blade body upon contact with the shroud, reducing the risk of catastrophic failure and eliminating the need for extensive trench filler by allowing controlled failure and detachment of the tip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metallic honeycomb trench filler is used to contain fan blade contact with shroud, then engine protection is improved, but engine weight increases and efficiency decreases
Solution Approach 1:
The fan blade is segmented into a body portion and a tip region made of different materials. The tip region is designed as a separate, sacrificial element that can fail independently to protect the engine, eliminating the need for heavy trench filler containment structures.
Solution Approach 2:
The heavy metallic honeycomb trench filler is extracted/removed from the engine design. Instead of using this heavy containment structure, the patent uses a lightweight tip region that fails controllably to provide protection without the weight penalty.
2Reliability
If fan blade tip contacts shroud during operation, then blade containment is improved, but rotary unbalance and fan gyrations increase causing significant damage
Solution Approach 1:
The tip region is pre-configured with reduced stiffness and made of a second material that is intentionally designed to fail at a predetermined load. This preliminary design ensures that when contact with the shroud occurs, the tip fails in a controlled manner before catastrophic damage can occur, preventing the harmful rotary unbalance and fan gyrations.
Solution Approach 2:
The potential harmful contact between the fan blade and shroud is converted into a beneficial controlled failure event. The tip region's designed weakness transforms the harmful impact into a predictable, limited failure mode that protects the engine from more severe damage.
3Strength
If fan blade is made entirely of strong material, then blade strength is improved, but controlled failure capability is reduced
Solution Approach 1:
The fan blade employs local quality by using different materials in different regions. The body portion is made of a first material with high strength, while the tip region is made of a second material with reduced stiffness. This allows the blade to maintain overall strength while having a specific local region capable of controlled failure.
Solution Approach 2:
The fan blade is constructed as a composite structure with two different materials: a first material for the body providing strength, and a second material for the tip region providing controlled failure capability. This composite approach allows both strong overall performance and localized sacrificial behavior.
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
This design reduces engine weight and inefficiencies by allowing the blade to fail in a controlled manner, minimizing damage and debris, and enabling a lighter, more efficient containment structure.
Implementation Method 1
The tip region is configured to fail when a predetermined force is applied to the tip such that the tip separates from the blade and defines a fused tip
Data Source
AI summary
A blade for a propulsion apparatus that includes a body formed of a first material having opposed pressure and suction sides, and extending in span between a root and a boundary, and extending in chord between a leading edge and a trailing edge. A tip region that is formed of a second material and that is positioned such that it extends from the body and defines a tip. The tip region joins the body at the boundary. The tip region is configured to fail when a predetermined force is applied to the tip such that the tip separates from the blade and defines a fused tip.