Seal Runner Density Gradient for Stable Turbine Seal Clearance
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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 runner with a density gradient is used, featuring a less dense outer section made of cellular material to compensate for centrifugal forces, while the inner section is solid, maintaining a controlled gap and preventing lubricant leakage through a radially decreasing density design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform density seal runner is used, then the structure is simple and easy to manufacture, but the sealing efficiency decreases under thermal growth and centrifugal force conditions
Solution Approach 1:
The seal runner is designed with a density gradient where the outer section has lower density than the inner section. This local quality variation allows the outer section to expand less under centrifugal force and thermal growth, maintaining a consistent gap dimension with the sealing ring and improving sealing efficiency without requiring a completely complex structure.
Solution Approach 2:
The density parameter of the seal runner is changed radially, creating a gradient from high density at the inner section to low density at the outer section. This parameter change enables differential thermal and centrifugal expansion characteristics that maintain optimal gap dimensions under operating conditions, resolving the contradiction between reliability and structural simplicity.
2Stability of the object's composition
If the outer section density is reduced to compensate for centrifugal force, then the gap dimension stability improves, but the material strength may be compromised
Solution Approach 1:
Different sections of the seal runner are assigned different density qualities appropriate to their functional requirements. The inner section maintains high density for structural strength and mounting integrity, while the outer section uses lower density to reduce centrifugal expansion and maintain gap stability, thus resolving the contradiction between dimensional stability and strength.
Solution Approach 2:
The seal runner is constructed as a composite structure with varying material densities across its radius. This composite approach allows optimization of each section's properties - the inner section provides structural integrity while the outer section provides dimensional stability under rotation, simultaneously achieving both strength and gap dimension stability.
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 design effectively maintains a consistent gap dimension under varying conditions, reducing leakage and heat generation, thereby enhancing sealing efficiency and engine performance.
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
Implementation Method 3
a density of the outer section being less than that of the inner section, the density defined as a mass per unit of volume of the seal runner
Data Source
AI summary
An aircraft engine, has: a shaft rotatable about a central axis; a housing mounted around the shaft; and a seal assembly disposed radially between the shaft and the housing relative to the central axis, the seal assembly having: a sealing ring mounted to the housing, and a seal runner secured to the shaft, the seal runner extending radially relative to the central axis from an inner face facing the shaft to an outer face facing the sealing ring and being radially spaced apart from the sealing ring by a gap, the seal runner having an inner section extending from the inner face towards the outer face, and an outer section extending from the outer face towards the inner face, a density of the outer section being less than that of the inner section, the density defined as a mass per unit of volume of the seal runner.