Carbon Seal Assembly With Shrink Band for Stable Turbine Gaps
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Solution Overview
Problem
Non-contacting seals in gas turbine engines face challenges in maintaining a constant gap dimension between complementary components under varying operating conditions, leading to potential heat generation and impaired engine operation due to thermal expansion differences between carbon and metal materials.
Innovation Solution
A seal assembly comprising a carbon ring and a shrink band with a similar thermal expansion coefficient to the metal counter component, where the shrink band is heat-shrunk around the carbon ring to maintain the gap dimension and reduce thermal expansion-induced contact, and optimized geometries such as varying radial thickness and axial overlap configurations are used to distribute stress and prevent excessive heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a carbon ring is used as a sealing component, then friction and heat generation are reduced, but thermal expansion mismatch with metal components causes gap dimension instability
Solution Approach 1:
The sealing component is constructed as a composite structure with a carbon ring surrounded by a metallic shrink band. The carbon ring provides low friction and heat generation, while the metallic shrink band compensates for thermal expansion differences between carbon and metal counter components, maintaining stable gap dimensions during operation.
Solution Approach 2:
The shrink band is designed with specific material properties and geometric parameters (thickness, axial length) that enable it to expand thermally at a rate matching the metal counter component. This parameter optimization allows the composite seal to maintain constant gap dimensions despite temperature changes.
2Stability of the object's composition
If the shrink band fully contacts the carbon ring axially, then thermal expansion compensation is maximized, but stress concentration and heat generation increase
Solution Approach 1:
The shrink band is designed with non-uniform axial contact: the central portion contacts the carbon ring to provide thermal expansion compensation, while the axial end portions are spaced apart from the carbon ring. This local differentiation reduces stress concentration and minimizes heat generation at the ends while maintaining gap stability in the critical central region.
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 a controlled gap dimension, reducing heat generation and preventing prolonged contact between seal components, thereby ensuring efficient operation of the gas turbine engine by matching thermal expansion rates and optimizing stress distribution.
Implementation Method 1
the carbon ring is surrounded by a metallic ring referred to as a shrink band
Data Source
AI summary
A seal assembly having: a carbon ring annularly extending about a central axis and having an outer face, and a shrink band annularly extending about the central axis, the shrink band having an inner face, the inner face in contact with the outer face of the carbon ring at a contact interface defined therebetween, the inner face of the shrink band protruding axially beyond the contact interface.