Variable-Density Seal Runner for Stable Turbine Seal Gaps
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Solution Overview
Problem
Gas turbine engines face challenges in maintaining the dimension of controlled gap seals between rotating and static parts due to thermal growth and centrifugal forces, leading to decreased sealing efficiency and potential lubricant leakage.
Innovation Solution
A seal assembly with a seal runner having a density gradient, where the outer section is made of a material with a lower density than the inner section, utilizing cellular materials and a top impermeable layer to compensate for centrifugal forces and maintain the controlled gap, while allowing compressed air to flow through the gap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a controlled gap seal is used between rotating and static parts, then sealing efficiency is improved, but thermal growth and centrifugal force cause dimension changes in the gap, leading to decreased sealing efficiency under certain conditions
Solution Approach 1:
The seal runner is constructed with a density gradient where the outer section has lower density than the inner section. This local variation in material properties allows the outer section to expand less under thermal growth and centrifugal force, maintaining a more stable gap dimension at the critical sealing interface while the inner section provides structural support.
Solution Approach 2:
The patent changes the physical parameter of density within the seal runner structure. By creating a density gradient from the inner to outer section, the material properties are optimized to reduce thermal expansion and centrifugal deformation in the critical outer region, thereby maintaining gap stability.
2Stability of the object's composition
If the seal runner outer section uses lower density material, then centrifugal force effects are reduced and gap stability is improved, but manufacturing complexity increases due to density gradient requirements
Solution Approach 1:
The seal runner is constructed as a composite structure with two distinct material sections: an inner section with higher density material providing structural strength, and an outer section with lower density material minimizing thermal and centrifugal expansion. This composite approach achieves the desired dimensional stability while managing the complexity through material selection rather than geometric complexity.
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 solution effectively maintains the controlled gap, reducing leakage and improving sealing efficiency by compensating for centrifugal forces and thermal expansion, thereby enhancing the performance of gas turbine engines.
Implementation Method 1
thermal growth and centrifugal force affect a dimension of this controlled gap, which may results in a decrease of the sealing efficiency in some conditions
Implementation Method 2
thermal growth and centrifugal force affect a dimension of this controlled gap
Data Source
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AI summary
An aircraft engine (10), has: a shaft (20) rotatable about a central axis (11); a housing (32) mounted around the shaft (20); and a seal assembly (40) disposed radially between the shaft (20) and the housing (32) relative to the central axis (11), the seal assembly (40) having: a sealing ring (42) mounted to the housing (32), and a seal runner (50) secured to the shaft (20), the seal runner (50) extending radially relative to the central axis (11) from an inner face (50I) facing the shaft (20) to an outer face (50O) facing the sealing ring (42) and being radially spaced apart from the sealing ring (42) by a gap (G), the seal runner (50) having an inner section (50A) extending from the inner face (50I) towards the outer face (50O), and an outer section (50B) extending from the outer face (50O) towards the inner face (50I), a density of the outer section (50B) being less than that of the inner section (50A), the density defined as a mass per unit of volume of the seal runner (50).