Variable Guide Vane Joint With Spherical Links to Reduce Fretting
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Solution Overview
Problem
Existing gas turbine engines face issues with wear and fretting in the mechanisms that control the movement of variable guide vanes and bleed off valves, leading to inaccuracies in positioning and reduced operational efficiency.
Innovation Solution
The implementation of a variable pitch stator vane stage with an actuation assembly that includes an actuation ring and vane links, where each vane link connects a stator vane to the actuation ring via spherical connections, allowing for precise rotation and adjustment of the vanes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If sheet metal arms are used to control variable guide vanes, then the mechanism can achieve movement and positioning, but high loads and wear on pin bushing occur due to twisting during operation
Solution Approach 1:
The patent applies spherical connections (ball joints) at the link ends instead of rigid sheet metal arms. The spherical bearing members allow for multi-directional movement and rotation, eliminating the twisting stresses that cause wear in rigid connections. This curvature-based joint design distributes loads more evenly and prevents fretting wear.
Solution Approach 2:
The patent introduces spherical bearing members as intermediary elements between the link and the vanes/actuation ring. These bearing members act as mediators that accommodate movement discrepancies and reduce direct contact wear between mating components, thereby improving reliability while maintaining movement capability.
2Ease of operation
If composite bushings are used in the mechanism, then movement is achieved, but wear occurs against the counterpart components
Solution Approach 1:
The patent replaces the traditional composite bushing mechanical connection with a spherical bearing mechanism. This substitution eliminates the sliding friction and wear associated with bushings by using rolling element bearings, thereby maintaining movement capability while significantly improving wear resistance and reliability.
3Ease of manufacture
If slop/looseness exists in system components, then assembly is easier, but wear and fretting increase leading to positioning inaccuracy
Solution Approach 1:
The spherical connections provide a self-aligning mechanism that eliminates slop and looseness while maintaining ease of assembly. The ball joint geometry naturally accommodates minor misalignments and tolerances, preventing fretting wear and ensuring accurate positioning without requiring extremely tight manufacturing tolerances.
Solution Approach 2:
The spherical bearing members provide continuous mechanical feedback that maintains precise positioning. The contact geometry ensures that any deviation from the correct position generates restoring forces that keep the vanes accurately positioned, compensating for minor assembly variations and preventing cumulative error.
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 reduces wear and fretting, enhances the accuracy of vane positioning, and improves the operational efficiency and reliability of gas turbine engines by minimizing mechanical stress and loosening in the actuation system.
Implementation Method 1
The first link end includes a first eye, and a first spherical bearing member positioned in the first eye. The vane link is connected to the actuation ring through the first spherical bearing member.
Implementation Method 2
Each vane link operably connects a corresponding stator vane of the plurality of stator vanes to the actuation ring. A vane link of the plurality of vane links includes a link body, and a first link end connected the link body. The first link end includes a first spherical connection to the actuation ring.
Data Source
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AI summary
A variable pitch stator vane stage of a gas turbine engine (10) includes a plurality of stator vanes (52) extending across a flowpath (C) of the gas turbine engine (10), and an actuation assembly (70) operably connected to the plurality of start vanes. The actuation assembly (70) includes an actuation ring (72) extending circumferentially around an engine central longitudinal axis (A) of the gas turbine engine (10), and a plurality of vane links (78). Each vane link (78) operably connects a corresponding stator vane (52) of the plurality of stator vanes (52) to the actuation ring (72). A vane link (78) of the plurality of vane links (78) includes a link body (84), and a first link end (82) connected the link body (84). The first link end (82) includes a first spherical connection to the actuation ring (72). Circumferential movement of the actuation ring (72) about the engine central longitudinal axis (A) urges rotation of the plurality of vanes about their respective vane axes (54).