Buffered Lip Seal Assembly for Thermal Expansion Leakage
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Solution Overview
Problem
Seal assemblies in rotating machines, such as gas turbine engines, face challenges in maintaining an effective seal across varying operating conditions due to thermal expansion differences between components, leading to leakage and increased complexity from heat removal requirements.
Innovation Solution
A seal assembly comprising a ceramic circumferential runner, a carbon seal ring, and an annular seal member with a curvilinear face surface, where the annular seal member is buffered by a flow of buffer air and the components have matched coefficients of thermal expansion to maintain engagement and reduce leakage, eliminating the need for direct oil cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional seal assemblies are used in rotating machines, then sealing function is provided, but thermal expansion differences between components cause leakage and increased complexity from heat removal requirements
Solution Approach 1:
The patent applies parameter changes by selecting materials with matched coefficients of thermal expansion. The ceramic runner and carbon seal ring are specifically chosen because their thermal expansion properties are compatible, allowing them to maintain consistent sealing engagement across varying temperatures without requiring complex thermal management systems.
Solution Approach 2:
The invention extracts the heat removal requirement from the seal assembly system. By using materials that naturally accommodate thermal expansion differences through matched coefficients, the patent eliminates the need for external cooling mechanisms, thereby reducing system complexity while maintaining sealing reliability.
2Reliability
If components with different thermal expansion coefficients are used, then sealing engagement is achieved at certain temperatures, but leakage occurs across varying operating temperatures
Solution Approach 1:
The patent changes the material parameters by selecting ceramic and carbon materials with matched coefficients of thermal expansion. This ensures that both components expand and contract at similar rates across the operating temperature range, maintaining consistent sealing engagement without leakage.
Solution Approach 2:
The invention uses a composite material approach by combining ceramic runner with carbon seal ring. These two materials are specifically selected because their thermal expansion properties are compatible, creating a composite sealing system that adapts reliably across varying temperatures.
3Temperature
If direct oil cooling is applied to the seal assembly, then heat removal is achieved, but system complexity and potential failure points increase
Solution Approach 1:
The patent removes the direct oil cooling requirement from the seal assembly system. By using materials with matched thermal expansion coefficients, the invention eliminates the need for external cooling mechanisms, thereby reducing system complexity and potential failure points while maintaining operational temperature control.
Solution Approach 2:
The sealing system serves itself thermally by using materials that naturally accommodate temperature variations through matched expansion properties. This self-service approach eliminates the need for active cooling systems, reducing complexity while maintaining temperature control.
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 ensures consistent sealing engagement across a range of temperatures, reducing air and oil leakage, wear, and system complexity by using a ceramic runner and carbon seal ring with a buffered annular seal member, enhancing durability and simplifying system design.
Implementation Method 1
The flow of buffer air buffers the annular seal member
Implementation Method 2
components have matched coefficients of thermal expansion to maintain engagement and reduce leakage
Data Source
AI summary
Systems and methods are presented for sealing a higher pressure fluid cavity from a lower pressure fluid cavity in a rotating machine. The cavities are at least partially disposed between a rotatable shaft and a housing. The seal assembly comprises a runner mounting assembly, a circumferential ceramic runner, a carbon seal ring, and an annular seal member. The carbon seal ring is sealing engaged with the housing and at least a portion of the runner to thereby form a boundary between the higher pressure fluid cavity and the lower pressure fluid cavity. The annular seal member is coupled to the housing axially displaced from the seal ring in the lower pressure fluid cavity. The seal member has a curvilinear face surface that engages the runner.