Sacrificial Graphitic Carbon Liners for Gas Turbine Vane Trunnions
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Solution Overview
Problem
The harsh operating environment of gas turbine engines, including extreme vibrations and high temperatures, leads to significant wear on variable vane trunnions, necessitating frequent replacement and increasing maintenance costs and engine weight.
Innovation Solution
A split engine shroud system featuring annular-shaped shrouds with inner pockets containing graphitic carbon liners, which absorb wear instead of the trunnion, eliminating the need for a carbon steel bushing and reducing maintenance costs, using a lightweight titanium material for the shroud.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon steel bushing and carbon steel split liner are used to encase trunnions, then structural strength is maintained, but trunnion wear increases due to vibration-induced contact
Solution Approach 1:
The patent introduces a sacrificial graphitic carbon liner that is intentionally designed to wear preferentially rather than the expensive trunnion. This disposable liner absorbs wear damage, protecting the permanent trunnion from degradation and extending its operational life.
Solution Approach 2:
The graphitic carbon liner acts as an intermediary between the trunnion and the carbon steel bushing/liner assembly. It provides a low-friction, self-lubricating interface that reduces direct metal-to-metal contact and wear on the trunnion while withstanding high temperatures.
2Reliability
If carbon steel bushing is used around vane trunnion, then wear protection is provided, but device complexity and maintenance requirements increase
Solution Approach 1:
The patent extracts the wear-protection function from the complex carbon steel bushing and liner assembly and consolidates it into a single graphitic carbon liner component. This simplifies the overall structure while maintaining wear protection through the liner's inherent low-friction properties.
Solution Approach 2:
The graphitic carbon liner is designed as a replaceable sacrificial component that can be easily discarded when worn and replaced without affecting the permanent trunnion or other engine components, thereby simplifying maintenance procedures.
3Strength
If traditional carbon steel components are used, then structural integrity is maintained, but overall engine weight increases
Solution Approach 1:
The patent employs a composite structure combining a titanium shroud with a graphitic carbon liner. The titanium provides structural strength and weight reduction compared to carbon steel, while the graphitic carbon liner provides wear protection and self-lubrication, achieving both strength and weight optimization.
Solution Approach 2:
The patent changes the material parameters from traditional carbon steel to titanium alloy for the shroud, significantly reducing density and weight while maintaining structural integrity through titanium's high strength-to-weight ratio properties.
4Reliability
If hard coating is applied to trunnion wear surface, then wear resistance is improved, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of applying expensive hard coatings to the permanent trunnion, the patent uses a sacrificial graphitic carbon liner that provides wear resistance through its self-lubricating properties. This approach is more cost-effective and simpler to manufacture than hard coating processes.
Solution Approach 2:
The patent replaces the mechanical hard coating system with a self-lubricating graphitic carbon liner system. The liner's layered structure provides inherent lubrication without requiring external lubricants or complex coating applications, simplifying manufacturing.
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
The graphitic carbon liners effectively reduce trunnion wear, extend operational life, and lower engine weight, while self-lubrication properties eliminate the need for hard coatings and allow for easy replacement or reuse, thereby minimizing maintenance and reducing overall engine costs.
Implementation Method 1
self-lubrication properties eliminate the need for hard coatings
Implementation Method 2
graphitic carbon liners effectively reduce trunnion wear, extend operational life
Data Source
AI summary
A split shroud system for a gas turbine engine having a pair of annular-shaped shrouds (170a,170b) that each have an inner pocket; to form a pair of inner pockets (185a,185b). Each of the pair of pockets having liner parts (150a,150b) that form a circle. Liner parts of one of the pair of pockets facing liner parts of the other of the pair of pockets to form liner part pairs. One of each of said of pair of liner parts has a mutual abutting surface that forms a plurality of slots (158) for accepting a plurality of vane inner trunnions (135).