Undersized Dovetail Rotor Blade Retention in Turbofan Spools
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Solution Overview
Problem
Modern turbofan engines face challenges in efficiently and effectively retaining rotor blades, particularly when fabricated from lightweight materials like carbon fiber reinforced polymer (CFRP), due to the complexity of assembling and maintaining these components.
Innovation Solution
The use of an annular spool with radially insertable rotor blades featuring a dovetail root portion undersized relative to the blade opening, combined with secondary dovetail members positioned within the opening to achieve an interference fit, ensures secure coupling and reduced assembly complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rotor blades are individually inserted into circumferential slots in the booster spool, then the rotor blades can be retained in the spool, but the assembly complexity increases and weight efficiency decreases
Solution Approach 1:
The patent combines multiple retention features into a single integrated retaining member that engages with the rotor blade root. This merging of retention functions reduces the number of separate components and simplifies the assembly process while maintaining reliable rotor blade retention in the booster spool.
Solution Approach 2:
The patent introduces a retaining member as an intermediary component between the rotor blade and the booster spool. This retaining member features a dovetail shape that interfaces with the rotor blade root and engages with the spool structure, providing an effective retention mechanism that simplifies assembly compared to individual insertion methods.
2Weight of moving object
If rotor blades are made from lightweight materials like CFRP, then weight efficiency improves, but the complexity of assembling and maintaining these components increases
Solution Approach 1:
The patent changes the geometric parameters of the retaining member, specifically designing it with a dovetail shape that has optimized dimensions and angles. This parameter optimization enables effective retention of lightweight CFRP rotor blades while simplifying the assembly process and reducing maintenance complexity through a straightforward insertion and engagement mechanism.
3Weight of moving object
If the root portion is undersized relative to the blade opening, then weight efficiency improves, but secure coupling under centrifugal forces becomes more difficult
Solution Approach 1:
The patent employs composite material structures in the retaining member design, combining materials with different properties to achieve both weight reduction and high coupling strength. The dovetail-shaped retaining member uses composite construction that maintains structural integrity under centrifugal forces while keeping the root portion undersized for weight efficiency.
Solution Approach 2:
The patent utilizes curved and tapered geometries in the dovetail shape of the retaining member. The curved surfaces and gradual transitions in the dovetail structure distribute stresses effectively, enabling secure coupling of the undersized root portion to the blade opening while maintaining strength under centrifugal loading conditions.
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 solution enhances weight efficiency, simplifies assembly, enables the use of composite materials, improves damping characteristics, and reduces maintenance complexity while securely retaining rotor blades under centrifugal forces.
Implementation Method 1
At least one secondary dovetail member is positioned within the blade opening and configured to couple the root portion within the blade opening with an interference fit
Data Source
AI summary
A rotor assembly for use in a turbofan engine is provided. The rotor assembly includes an annular spool including a blade opening defined therein, and a rotor blade radially insertable through the blade opening. The rotor blade includes a rotor blade radially insertable through the blade opening. The rotor blade includes a root portion having a dovetail shape, and the root portion is undersized relative to the blade opening. At least one secondary dovetail member is positioned within the blade opening and configured to couple the root portion within the blade opening with an interference fit.