Carbon Face Seal Carrier With Wave Split Ring Biasing
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Solution Overview
Problem
Carbon seals in gas turbine engines face challenges with frictional heating and stress distribution, leading to potential fatigue and wear, particularly in dry face seals without cooling, where interference fits can be overly strenuous and prone to vibration-induced displacement.
Innovation Solution
A seal system utilizing a wave-form split ring to bias the carbon seal into engagement with a seal carrier, providing a lighter radial interference fit and compressive stress between 10 MPa to 60 MPa, combined with a fluoroelastomer sealing ring and a rebate coating, to maintain consistent sealing and reduce thermal and tensile stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a traditional interference fit is used to secure the carbon seal to the seal carrier, then the seal is retained securely, but the stress and wear on the seal increases, leading to fatigue and potential failure
Solution Approach 1:
The seal carrier is segmented into a hub and a seal carrier body, with the hub being a separate component that fits into the seal carrier body. This segmentation allows the hub to provide secure retention of the carbon seal through interference fit, while the seal carrier body provides structural support without transmitting excessive stress to the seal, thus resolving the contradiction between secure retention and reduced stress/wear.
2Stability of the object's composition
If a heavy interference fit is used to prevent vibration-induced displacement, then the seal remains stable, but the frictional heating and thermal stress increase
Solution Approach 1:
By segmenting the seal carrier into hub and body components, the interference fit is localized to the hub-seal interface rather than being distributed throughout the entire seal carrier. This provides sufficient stability to prevent vibration-induced displacement while minimizing the overall frictional heating and thermal stress, as the contact area and pressure are concentrated in the hub region where they are better managed.
3Strength
If the seal carrier is made as a single heavy component, then structural strength is sufficient, but the mass increases and stress distribution becomes uneven
Solution Approach 1:
The seal carrier is divided into a hub and a seal carrier body, allowing each component to be optimized for its specific function. The hub can be designed with higher strength materials and features to provide secure seal retention, while the seal carrier body can be lighter in mass. This segmentation reduces the overall mass compared to a single heavy component while maintaining sufficient structural strength through the coordinated design of the segmented parts.
4Reliability
If a lighter interference fit is used to reduce stress, then wear and heat generation decrease, but the seal may become displaced due to vibration
Solution Approach 1:
The hub, as a separate component within the segmented seal carrier design, is specifically engineered to provide the necessary interference fit for secure seal retention. This allows the overall seal carrier system to use a lighter interference fit that reduces stress and wear on the seal, while the hub locally provides sufficient retention force to prevent vibration-induced displacement, thus resolving the contradiction between durability and position 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 solution effectively reduces stress and wear, enhances sealing consistency, and allows for a lighter, more efficient seal design with reduced heat generation and longer longevity, while maintaining effective sealing performance across varying operational conditions.
Implementation Method 1
A wave-form split ring contacts the first sidewall and biases the seal into engagement with the radial wall first surface
Implementation Method 2
the seal is in a radial interference fit with the seal carrier axially-extending wall ID surface
Data Source
AI summary
An apparatus has: a first member; a shaft rotatable relative to the first member about an axis; and a seal system. The seal system has: a seal carried by the first member and having a seal face; a seal carrier; a seat carried by the shaft and having a seat face in sliding sealing engagement with the seal face; and one or more springs biasing the seal carrier relative to the first member so as to bias the seal face against the seat face. The seal carrier has: an axially-extending wall having an inner diameter (ID) surface; and a radially-extending wall having a first surface. The seal carrier axially-extending wall ID surface has a radially inwardly open groove having a first sidewall and a second sidewall and a base. A wave-form split ring contacts the first sidewall and biases the seal into engagement with the radial wall first surface.