Variable Stator Vane Non-Structural Fairing
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Solution Overview
Problem
Variable stator vanes in turbine engines face stress issues due to transition area design, leading to aerodynamic inefficiencies and high manufacturing costs, as well as challenges in minimizing stress while maintaining aerodynamic efficiency and structural integrity.
Innovation Solution
The use of a non-structural fairing, which is a molded cylindrical member with an airfoil-shaped aperture and a tab, surrounds the airfoil and interfaces with the flat surface to bury a larger structural fillet, reducing stress concentrations without impacting aerodynamic performance and allowing for larger fillets to be used for manufacturability and stress reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a transition fillet is provided between the airfoil and platforms to minimize stress, then stress concentrations are reduced, but aerodynamic performance deteriorates due to blockage in the flowpath and cavities caused by flat surfaces
Solution Approach 1:
The patent introduces a radial dimension solution by providing a radial gap between the airfoil and the platform overhang, rather than attempting to eliminate the fillet entirely. This radial positioning allows the fillet to exist without blocking the axial flowpath, effectively moving the stress relief feature to a different spatial dimension where it no longer interferes with aerodynamic flow.
Solution Approach 2:
The patent extracts the harmful flat surfaces and cavities from the flowpath by redesigning the transition area. Instead of having flat fillet surfaces that block flow, the design uses curved transitions and positions features radially outward, removing the obstructive elements while retaining the stress relief function.
2Reliability
If excessive trailing edge overhang is used for aerodynamic efficiency, then aerodynamic performance is improved, but structural integrity deteriorates due to stress risers and susceptibility to stress
Solution Approach 1:
The patent applies curvature to the transition areas between the airfoil and platforms, using rounded fillets instead of sharp corners or flat surfaces. This curvature distributes stress more evenly across the transition zone, reducing stress concentration points while accommodating the necessary trailing edge overhang for aerodynamic performance.
Solution Approach 2:
The patent applies different geometric qualities to different regions: the airfoil maintains its aerodynamic shape with necessary overhang, while the transition areas use curved, stress-distributing geometries. This localized differentiation allows each region to optimize for its primary function—aerodynamics or structural integrity.
3Strength
If three-dimensional blends are used to optimize structure, then stress resistance is improved, but manufacturing complexity increases and costs significantly due to hand production requirements
Solution Approach 1:
The patent segments the stator vane into distinct components: the airfoil, the platforms, and the transition fillets. This segmentation allows each component to be manufactured separately using standard processes, then assembled together, avoiding the need for complex hand-formed three-dimensional blends while achieving the necessary stress relief through the fillet design.
4Strength
If radial gaps are present between the overhung airfoil and static structure, then stress is reduced, but aerodynamic performance deteriorates due to flow leakage and efficiency loss
Solution Approach 1:
The patent uses thin fillet structures as flexible transition elements between the rigid airfoil and platform. These thin curved surfaces provide stress relief while minimizing flow leakage, as their thin nature reduces the gap effect compared to thicker transition structures.
Data Source
Figure 1
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AI summary
A variable stator vane assembly for a gas turbine engine includes a variable stator vane and a non-structural fairing on the variable stator vane.