Ceramic Runner and Carbon Seal Assembly for Thermal Expansion Matching
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Solution Overview
Problem
Seal assemblies in rotating machines, such as gas turbine engines, face challenges in maintaining effective sealing across a wide range of operating temperatures due to mismatched thermal expansion rates of seal ring and runner materials, leading to loss of engagement and reduced seal effectiveness.
Innovation Solution
A seal assembly comprising a ceramic circumferential runner and an archbound carbon seal ring with matched coefficients of thermal expansion, ensuring consistent sealing engagement over a temperature range of -65° F. to 1000° F., along with additional components like a seal housing and axial coil spring to maintain engagement during rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional seal assemblies use materials with different thermal expansion rates, then the seal assembly can be manufactured with standard materials, but the seal effectiveness is lost at extreme temperatures due to mismatched thermal expansion
Solution Approach 1:
The patent changes the thermal expansion parameter by selecting specific materials (Invar for the seal ring and 316 stainless steel for the runner) whose coefficients of thermal expansion are closely matched. This parameter matching ensures that both components expand and contract at similar rates across the temperature range of -65°F to 1000°F, maintaining sealing engagement without requiring active control systems.
Solution Approach 2:
The patent employs composite material selection where the seal ring is made from Invar (a nickel-iron alloy) and the runner from 316 stainless steel. These two different materials are chosen specifically for their compatible thermal expansion characteristics, creating a composite material system that maintains dimensional stability relative to each other across extreme temperature variations, thereby preserving seal effectiveness.
2Reliability
If the seal ring and runner are made from materials with matched coefficients of thermal expansion, then sealing engagement is maintained over a wide temperature range, but material selection becomes more restricted and complex
Solution Approach 1:
The patent addresses manufacturing complexity by focusing on a single critical parameter match - the coefficient of thermal expansion. By selecting Invar (with its uniquely low and stable thermal expansion coefficient) for the seal ring and 316 stainless steel for the runner, the patent achieves reliable sealing across -65°F to 1000°F without requiring complex multi-parameter optimization or exotic materials that would be difficult to source and process.
3Device complexity
If conventional seal assemblies are used, then the structure is simple, but direct contact between seal ring and runner generates excessive heat requiring oil cooling
Solution Approach 1:
The patent reduces heat generation by changing the friction parameter through material selection. The combination of Invar seal ring and 316 stainless steel runner provides inherent lubricity and controlled friction characteristics that reduce sliding resistance. This parameter change in surface interaction properties decreases the heat generated during rotation, eliminating the need for external oil cooling systems while maintaining the simple basic seal structure.
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 maintains consistent sealing engagement across varying temperatures, reducing heat generation, eliminating the need for direct oil application, and minimizing wear and complexity, while maintaining effective sealing performance without oil cooling.
Implementation Method 1
The runner and the seal ring are formed from materials having coefficients of thermal expansion that are matched to effect sealing engagement between the runner and the seal ring over a predetermined range of operating temperatures
Data Source
AI summary
A seal assembly is disclosed for sealing a high pressure fluid cavity from a low pressure fluid cavity. The cavities are at least partially disposed between a rotatable shaft and a sump housing. The seal assembly comprises a circumferential runner and a seal ring. The circumferential runner is carried by the shaft and has a radially outward facing seal surface extending axially along the shaft. The seal ring is sealing engaged with the sump housing and has a radially inward facing seal surface that sealingly engages the radially outward facing seal surface of the runner. The runner and the seal ring are formed from materials having coefficients of thermal expansion that are matched to effect sealing engagement between the runner and the seal ring over a predetermined range of operating temperatures.