Non-Contacting Seal Coating for Stable Turbine Gap Control
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Solution Overview
Problem
Non-contacting seals in gas turbine engines face challenges in maintaining a consistent controlled gap and preventing contact between sealing components, which can lead to excessive heat generation and operational impairment due to thermal expansion and pressure differentials.
Innovation Solution
A non-contacting seal assembly with a metallic sealing ring and counter component, both made of similar thermal expansion materials, featuring a controlled gap with at least one sealing face coated with a non-abradable material to prevent direct contact and maintain a pressure differential, while allowing for rotational movement and thermal expansion without inducing contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a carbon sealing ring is used to reduce friction and heat generation, then the degree of friction against the runner is reduced, but the thermal expansion coefficient mismatch with the metal runner causes the controlled gap to become inconsistent
Solution Approach 1:
The sealing ring is made from a metal material having a coefficient of thermal expansion similar to that of the runner, creating homogeneous thermal expansion characteristics. This ensures that both components expand at similar rates when subjected to thermal conditions, maintaining a consistent controlled gap between the sealing faces throughout operation.
Solution Approach 2:
The sealing ring combines a metal base material with a non-abradable coating applied to the sealing face. The metal portion provides thermal expansion compatibility with the runner, while the non-abradable coating prevents direct metal-to-metal contact and material transfer, creating a composite structure that addresses both thermal and tribological requirements.
2Manufacturing precision
If a metallic sealing ring is used to match thermal expansion with the runner, then the controlled gap remains consistent during thermal expansion, but direct metal-to-metal contact causes excessive heat generation upon contact
Solution Approach 1:
The sealing ring combines a metal base material with a non-abradable coating applied to the sealing face. The metal portion provides thermal expansion compatibility with the runner, while the non-abradable coating prevents direct metal-to-metal contact and material transfer, creating a composite structure that addresses both thermal and tribological requirements.
Solution Approach 2:
A non-abradable coating is applied to the sealing face of the metal sealing ring. This coating acts as an intermediary layer between the metal sealing ring and the metal runner, preventing direct metal-to-metal contact. The coating has properties that reduce friction and prevent material transfer while allowing the underlying metal structure to maintain thermal expansion compatibility.
3Manufacturing precision
If a carbon sealing ring surrounded by a metallic shrink band is used, then thermal expansion is limited to maintain gap consistency, but the structural complexity and manufacturing difficulty increase
Solution Approach 1:
The sealing ring is made from a metal material having a coefficient of thermal expansion similar to that of the runner, creating homogeneous thermal expansion characteristics. This ensures that both components expand at similar rates when subjected to thermal conditions, maintaining a consistent controlled gap between the sealing faces throughout operation.
Solution Approach 2:
The sealing ring combines a metal base material with a non-abradable coating applied to the sealing face. The metal portion provides thermal expansion compatibility with the runner, while the non-abradable coating prevents direct metal-to-metal contact and material transfer, creating a composite structure that addresses both thermal and tribological requirements.
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 consistent controlled gap and prevents excessive heat generation, ensuring efficient operation by using metallic components with similar thermal expansion and non-abradable coatings to manage thermal growth and pressure differentials.
Implementation Method 1
carbon, which has a relatively low degree of friction against the runner
Implementation Method 2
carbon does not have the same thermal expansion coefficient as the runner which was typically made of a metal, and for the gap to remain relatively constant during typical operating conditions, the carbon ring is surrounded by a metallic ring referred to as a shrink band and which limited the thermal expansion of the carbon ring relative to the runner
Data Source
AI summary
There is provided a non-contacting seal assembly for a gas turbine engine, having a housing that houses a sealing ring; and a counter component cooperating with the sealing ring. The sealing ring and the counter component are rotatable relative to each other about a central axis and define sealing faces circumferentially extending around the central axis. The sealing faces face each other and are spaced apart from each other by a controlled gap. At least one of the sealing faces is coated with a non-abradable material. A method of operating a non-contacting seal assembly is also provided.