Variable Pitch Airfoil Balancing Insert for Vibration Reduction
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Solution Overview
Problem
Turbine engines with variable pitch airfoil assemblies face challenges in balancing, leading to unbalanced conditions and resulting vibration stresses when the pitch is adjusted.
Innovation Solution
The airfoil assembly includes a balancing insert, which can be provided along a portion of the sleeve or within the spar, to balance the airfoil assembly and reduce vibration stresses across a range of pitches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable pitch airfoil assembly is used to adjust flow characteristics, then adaptability is improved, but device complexity increases
Solution Approach 1:
The airfoil assembly employs a dynamic pitch adjustment mechanism where the airfoil can rotate about a spanwise axis to change its pitch angle. This dynamic capability allows the airfoil to adapt to different operating conditions while maintaining a relatively simple structural implementation through the use of a trunnion-mounted spar system.
2Adaptability or versatility
If pitch adjustment mechanism is added to enable variable pitch, then adaptability is improved, but weight increases
Solution Approach 1:
A balancing insert is provided within the airfoil assembly to counterbalance the weight changes that occur during pitch adjustment. This counterbalancing mechanism reduces the effective weight variation and minimizes the additional weight required for the pitch adjustment system itself, allowing the airfoil to rotate more efficiently between different pitch angles.
3Adaptability or versatility
If variable pitch airfoil assembly is implemented, then adaptability is improved, but vibration stresses increase
Solution Approach 1:
The balancing insert serves as a counterweight that compensates for the unbalanced forces and vibrations generated during pitch adjustment. By strategically positioning this balancing mass within the airfoil assembly, the system minimizes vibration stresses on the rotating components and reduces harmful oscillations that would otherwise occur during variable pitch operation.
Solution Approach 2:
The pitch adjustment mechanism is designed to dynamically balance the airfoil assembly during rotation. The balancing insert is positioned to maintain dynamic equilibrium as the airfoil changes pitch angles, thereby reducing vibration stresses and ensuring smooth operation across the full range of motion.
4Reliability
If balancing insert is added to reduce vibration stresses, then reliability is improved, but device complexity increases
Solution Approach 1:
The balancing insert is nested within the existing structure of the airfoil assembly, specifically integrated into the spar or airfoil body. This nested configuration allows the balancing function to be added without significantly increasing external complexity, as the balancing mass is housed within the existing structural envelope of the airfoil assembly.
Data Source
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AI summary
A turbine engine (10) comprising a fan section (18), a compressor section (22), a combustion section (28), and a turbine section (32) in serial flow arrangement and defining a stator portion and a rotor portion, which rotates about an engine centerline (12). The rotor portion comprising a variable pitch airfoil assembly (130). The variable pitch airfoil assembly (130) having an airfoil (132) and a balancing insert (170).