Variable Guide Vane Bushing Mounting for Vibration and Wear Reduction
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Solution Overview
Problem
In gas turbine engines, variable guide vane assemblies experience issues with vibrations and premature wear due to loose fits between bushings and casing components, leading to increased energy losses and potential costly replacements of expensive inner casings.
Innovation Solution
The use of resilient members, such as elastomeric O-rings or C-seals, is introduced between the inner casing and bushings to minimize contact and rotation, reducing vibrations and wear by centering and holding bushings in place, thus accommodating tolerance stack-up and thermal growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a loose fit is used between bushings and casing components, then assembly is easier and tolerance stack-up is accommodated, but vibrations increase and wear accelerates
Solution Approach 1:
A resilient member (such as a resilient ring or elastomeric seal) is introduced as an intermediary element between the bushing and the casing. This resilient member acts as a mediator that provides vibration damping and wear protection while accommodating the loose fit necessary for assembly ease and tolerance stack-up.
Solution Approach 2:
The resilient member is pre-installed between the bushing and casing to provide beforehand cushioning against vibrations and wear. This cushioning effect is built into the assembly before operation, preventing direct metal-to-metal contact and reducing harmful vibrations during engine operation.
2Reliability
If resilient members are added between inner casing and bushings, then vibrations and wear are reduced, but device complexity increases
Solution Approach 1:
The resilient member is implemented as a flexible ring or elastomeric seal that can be easily deformed during installation and then maintains its shape during operation. This flexible structure provides vibration damping and wear protection without requiring complex assembly procedures or additional fastening mechanisms.
3Ease of operation
If bushings are allowed to rotate freely in pockets, then ease of operation is improved, but contact with peripheral walls causes wear and energy losses
Solution Approach 1:
The resilient member serves as an intermediary between the bushing and the pocket peripheral walls. It allows the bushing to rotate freely for ease of operation while simultaneously preventing direct contact between the bushing and the rigid peripheral walls, thereby eliminating wear and energy losses from friction.
4Reliability
If tight fit is used between bushings and casing, then wear is minimized, but tolerance stack-up and thermal growth are restricted
Solution Approach 1:
The resilient member changes its physical parameters (compression, deformation) in response to thermal growth and tolerance variations. As temperature increases or tolerances vary, the resilient member deforms to accommodate these changes while maintaining continuous contact that prevents wear, thus adapting to different operational conditions.
Solution Approach 2:
The resilient member is designed to accommodate thermal expansion of the bushing and casing components. As temperature increases during engine operation, the resilient member deforms to allow for thermal growth while maintaining sufficient contact pressure to prevent wear and vibration.
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 design reduces vibrations, minimizes wear, and extends the operational range of the compressor section by reducing energy losses and delaying the need for costly replacements of the inner casing, while allowing for the use of materials with larger thermal coefficient differences.
Implementation Method 1
resilient members, such as elastomeric O-rings or C-seals, is introduced between the inner casing and bushings to minimize contact and rotation, reducing vibrations and wear by centering and holding bushings in place
Implementation Method 2
The use of resilient members, such as elastomeric O-rings or C-seals, is introduced between the inner casing and bushings to minimize contact and rotation, reducing vibrations and wear by centering and holding bushings in place, thus accommodating tolerance stack-up and thermal growth
Data Source
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AI summary
A gas turbine engine (10) has: an annular gaspath (20) extending around a central axis (11), the annular gaspath (20) defined between a first casing (28) and a second casing (26), the first casing (28) defining pockets (28a); and a variable guide vane assembly (40) having: variable guide vanes (42) circumferentially distributed around the central axis (11), the variable guide vanes (42) having airfoils (42a) extending into the annular gaspath (20) and extending between first and second pivot members (42f, 42g) at respective first and second ends of the airfoils (42a), the variable guide vanes (42) rotatable about respective spanwise axes (A), bushings (46) received within the pockets (28a) of the first casing (28), the first pivot members (42f) of the variable guide vanes (42) rollingly engaged to the bushings (46), and resilient members (50) disposed radially between surfaces of the first casing (28) and the bushings (46) relative to the spanwise axes (A), the resilient members (50) in abutment against both of the surfaces of the first casing (28) and the bushings (46).