Brazed Carbon Seal Carrier Assembly for Turbine Engine Stability
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Solution Overview
Problem
The existing seal assemblies in gas turbine engines face issues with carbon seal elements being brittle and prone to shifting due to low interference fit pressures and adhesive degradation at high temperatures, leading to instability during operation and handling.
Innovation Solution
A metal seal carrier with a receptacle and a cylindrical carrier surface, where the carbon seal element is brazed to the carrier surface, providing a robust connection through a braze material like silver or nickel, and a gap between the carrier and element surfaces filled with bonding material to enhance bonding and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an interference fit is used to retain the carbon seal element in the seal carrier, then the seal element can be retained without adhesive, but the connection strength is insufficient due to the brittle nature of carbon and small interference fit pressure
Solution Approach 1:
The patent replaces the mechanical interference fit system with a thermal bonding system. A metal insert with a bonding layer is heated to a temperature where the bonding material becomes pliable or melts, allowing it to flow into the recesses of the carbon seal element. Upon cooling, the bonding material solidifies, creating a strong mechanical interlock between the metal insert and carbon seal element that far exceeds the capability of interference fit alone.
Solution Approach 2:
The patent employs a composite bonding layer consisting of multiple materials with different properties. The bonding layer includes a metal matrix (such as nickel or cobalt-based alloys) combined with ceramic particles or carbon-containing compounds. This composite structure provides both the thermal stability required for high-temperature operation and the bonding characteristics necessary for strong attachment to the carbon seal element.
2Ease of operation
If adhesive is used to temporarily retain the seal element during installation, then the seal element can be held in place, but the adhesive degrades due to high engine operating temperatures
Solution Approach 1:
The patent replaces the chemical adhesive system with a thermal bonding system using a metal insert and bonding layer. This substitution eliminates the temperature degradation issue inherent in adhesive-based retention, as the metal insert and bonding material are specifically selected to maintain their structural and bonding properties at high engine operating temperatures.
Solution Approach 2:
The patent changes the temperature parameter of the bonding process. The bonding layer is applied in a state where it is pliable or molten (high temperature), allowing it to conform to and bond with the carbon seal element. After bonding, the assembly is cooled, and the bonding layer solidifies into a rigid, temperature-resistant connection that can withstand engine operating conditions.
3Device complexity
If a simple interference fit is used, then the assembly is simple, but the seal element shifts within the seal carrier during operation and handling
Solution Approach 1:
The patent applies preliminary action by pre-heating the metal insert before assembly. This thermal preparation causes the bonding material to become pliable or melt in advance, allowing it to flow into and fill the recesses of the carbon seal element before final assembly. This preliminary thermal action ensures that when the components are joined, the bonding material already provides maximum bonding surface area and interlock, preventing any shifting during operation.
Solution Approach 2:
The bonding layer uses a composite material structure that combines a metal matrix with ceramic or carbon particles. This composite provides both the flow characteristics needed for preliminary action (when heated) and the rigid, position-locking properties needed for operational stability. The composite structure creates a mechanical interlock that prevents seal element shifting while maintaining assembly feasibility.
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 provides a secure and stable connection between the carbon seal element and the metal seal carrier, resisting vibrations and impacts, and maintaining sealing effectiveness even under high operational conditions.
Implementation Method 1
The carbon seal element is brazed to the cylindrical carrier surface
Implementation Method 2
The bonding material is disposed in the gap and bonds the carbon seal element to the metal seal carrier
Data Source
Figure 1
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AI summary
An assembly (20) is provided for rotational equipment. This assembly (20) includes a metal seal carrier (72) and a carbon seal element (46). The metal seal carrier (72) includes a receptacle (102) and a cylindrical carrier surface forming an outer peripheral boundary of the receptacle (102). The carbon seal element (46) is seated in the receptacle (102). The carbon seal element (46) includes a cylindrical element surface that is brazed to the cylindrical carrier surface.