Variable Stator Vane Extended Fillet Design
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Solution Overview
Problem
Existing variable stator vane designs in gas turbine engines face issues with high vibrations and stresses at the intersection area between the button end and the overhang portion of the vane airfoil, leading to potential cracking and efficiency losses due to airflow disruption and material weight penalties.
Innovation Solution
A variable stator vane assembly with an extended fillet that extends beyond 60% of the overhang portion's length, featuring a constant radius and a cut surface to smoothly transition airflow, reducing local stresses and material usage while maintaining aerodynamic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If local thickening is provided in the intersection area to reduce vibrations and stress concentration, then the vane's flexibility and vibration are reduced, but airflow is disturbed and efficiency is lost
Solution Approach 1:
The patent applies local quality by providing a fillet specifically at the intersection area between the button end and the overhang portion, rather than uniformly thickening the entire vane. This localized geometric modification strengthens the vulnerable intersection area while maintaining the original airfoil shape and airflow path, thus improving reliability without compromising aerodynamic efficiency
Solution Approach 2:
The patent uses a curved fillet geometry with a specified radius (0.05 to 0.15 times the button diameter) to replace the sharp corner at the intersection area. This curvature eliminates stress concentration by distributing stresses smoothly around the rounded transition, reducing vibrations and cracking risk while maintaining streamlined airflow without the need for local thickening that would disrupt the airfoil shape
2Strength
If local thickening is provided in the intersection area, then stress concentration is reduced, but weight increases due to added material
Solution Approach 1:
The fillet is applied locally only at the intersection area where stress concentration occurs, rather than adding material throughout the entire vane structure. This localized approach provides the necessary strength improvement at the critical location while minimizing additional weight
Solution Approach 2:
The curved fillet geometry redistributes stresses through a smooth transition zone, achieving enhanced strength and stress resistance through geometric optimization rather than through material addition, thus improving strength without significant weight penalty
3Ease of manufacture
If a constant radius fillet is used at the intersection area, then manufacturing is simplified, but the overhang portion remains susceptible to high vibrations and stresses
Solution Approach 1:
The patent specifies that the fillet should extend along a sufficient portion of the overhang portion (at least 30% of the overhang length), providing enhanced strength and vibration resistance where needed while maintaining manufacturing simplicity through the use of a constant radius fillet that can be fabricated using standard processes
Solution Approach 2:
The patent optimizes the fillet radius parameter to be between 0.05 and 0.15 times the button diameter, and specifies the fillet extension length as at least 30% of the overhang portion length. These parameter optimizations balance manufacturing ease with improved vibration and stress resistance
Data Source
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AI summary
An example variable stator vane assembly (29) includes at least one button (38), a vane airfoil (40) adjacent to the button (38), and a fillet (52) defined between the button (38) and the airfoil (40). In one example, the fillet (52) defines a constant radius and extends beyond the button (38) at least greater than a distance of 60% of a length of an overhang portion (58) of the vane airfoil (40).