Duct-Fed Circumferential Seal Assembly to Prevent Hot Gas Backflow
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Solution Overview
Problem
Existing circumferential sealing assemblies in gas turbines suffer from backflow of hot gas through grooves, leading to mixing with lubricant oil and increasing the risk of oil coking and engine fires.
Innovation Solution
A circumferential sealing assembly with duct-fed grooves and ducts that redirect hot gas to form a hydrodynamic flow, creating a thin film to prevent lubricant migration and avoid backflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grooves are used to redirect hot gas for sealing, then sealing effectiveness is improved, but backflow of hot gas occurs causing lubricant migration
Solution Approach 1:
The sealing assembly is divided into multiple functional segments: stationary sealing rings, rotatable runners with grooves, and duct systems. Each segment performs a specific function - the grooves redirect hot gas while the ducts deliver additional hot gas to prevent backflow, collectively solving the sealing problem without the harmful effects of a single design
Solution Approach 2:
Hot gas acts as an intermediary substance to achieve sealing between the lubricant-containing compartment and the other compartment. The hot gas flows through grooves and is supplemented by ducts, creating a protective barrier that prevents direct contact between lubricant and environments where it could cause harm, thus resolving the contradiction between sealing effectiveness and preventing harmful backflow
2Reliability
If hot gas is redirected through grooves to form thin film, then lubricant migration is prevented, but mixing of hot gas and lubricant increases risk of oil coking
Solution Approach 1:
The invention uses pneumatic principles by utilizing hot gas flow through grooves and ducts to create a hydrodynamic thin film barrier. This gas-based sealing mechanism prevents lubricant migration while the controlled flow patterns and rapid redirection minimize the time for hot gas-lubricant mixing, thereby reducing oil coking risk while maintaining reliable sealing
3Reliability
If circumferential sealing is used to separate compartments, then isolation is achieved, but structural complexity increases
Solution Approach 1:
The sealing assembly components, particularly the rotatable runners with grooves and the duct systems, serve multiple functions simultaneously: they guide hot gas flow, create sealing barriers, prevent lubricant migration, and maintain structural integrity. This multi-functionality achieves reliable compartment isolation while minimizing the number of separate components needed, thus reducing overall structural complexity
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 assembly effectively prevents lubricant migration and reduces the risk of oil coking and engine fires by maintaining a stable thin film between the sealing ring and rotatable runner or sleeve.
Implementation Method 1
The hot gas entering the grooves in use via the ducts in combination with rotation of the grooves with the rotatable runner cause the hot gas to form a hydrodynamic flow within the grooves
Implementation Method 2
The grooves redirect the hot gas in the direction of the inner sealing surface to form a thin film between the outer sealing surface and the inner sealing surface
Data Source
AI summary
A circumferential sealing assembly for use between a lower-pressure oil side and a higher-pressure gas side is presented. The assembly includes a sealing ring interposed between either a rotatable runner or a sleeve and a housing within a turbine engine. Ducts communicate the hot gas into grooves to form a thin film between the ring and the runner or the sleeve. Embodiments include grooves on the runner and ducts through the runner; grooves on the ring and ducts through the runner; grooves on the ring and ducts through the ring; grooves on the runner and ducts through the ring; grooves on the sleeve and ducts through the sleeve; grooves on the ring and ducts through the sleeve; grooves on the ring and ducts through the ring adjacent to the sleeve; and grooves on the sleeve and ducts through the ring. Grooves and/or ducts may rotate with the component(s) thereon.