Bearing Compartment Seal Oil Routing for Negative-Gravity Events
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Solution Overview
Problem
Gas turbine engines face issues with oil distribution and scavenging during negative gravity events, where oil is not effectively collected and redirected to bearing compartments, leading to reduced oil pressure and availability for cooling and lubrication, especially in compartments without gutters.
Innovation Solution
Incorporating a gutter with a V-shaped channel radially outward of the seal assembly to collect and redirect oil to a scavenge line, and a valve system that ensures continuous oil supply to critical components by prioritizing oil flow during negative gravity events, preventing low oil pressure situations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a scavenge pump is used to collect and redirect oil during negative gravity events, then oil collection and redistribution capability is improved, but system complexity increases due to additional components and control mechanisms
Solution Approach 1:
The gutter is pre-positioned radially outward of the seal assembly to capture oil before it can be lost during negative gravity events. This preliminary positioning ensures oil is collected and redirected to the scavenge pump system before starvation occurs, maintaining reliability without requiring complex real-time detection systems.
Solution Approach 2:
The gutter acts as an intermediary component between the seal assembly and the scavenge pump. It captures oil radially outward of the seal and channels it to the scavenge pump, simplifying the overall system by providing a passive collection mechanism that reduces the burden on the active pump system.
2Reliability
If a valve system is implemented to prioritize oil flow to critical components, then oil pressure stability is improved, but device complexity increases due to additional valve components and control logic
Solution Approach 1:
The valve system implements local quality control by selectively directing oil flow to specific bearing compartments based on their criticality. The first bearing compartment (with seal assembly) receives prioritized oil supply through the first supply line, while the second bearing compartment receives oil through the second supply line controlled by the valve. This localized differentiation maintains pressure stability without requiring system-wide complex control.
Solution Approach 2:
The oil supply system is segmented into separate supply lines with independent control. The first supply line serves the first bearing compartment continuously, while the second supply line to the second bearing compartment is controlled by the valve that closes during negative gravity events. This segmentation allows simple binary control logic to achieve reliable pressure management.
3Reliability
If gutters are installed in all bearing compartments, then oil collection capability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
Gutters are selectively installed only in the first bearing compartment that contains the seal assembly, rather than in all bearing compartments. This localized approach addresses the specific oil collection need at the seal assembly location during negative gravity events, while avoiding unnecessary complexity and cost in other compartments that do not require this level of protection.
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
Ensures continuous oil supply and pressure to critical components like seal assemblies, maintaining effective cooling and lubrication even during negative gravity events, thereby preventing component starvation and ensuring engine operation.
Implementation Method 1
A scavenge pump is in communication with a first supply line configured to supply the first bearing compartment and a second supply line configured to supply the second bearing compartment
Implementation Method 2
A valve between the scavenge pump and the second supply line is configured to close in response to a dry port event, such that the closing the valve stops oil supply to the second supply line
Implementation Method 3
The gutter includes a channel on its radially inner face. The channel feeds the gutter scavenge line through an air/oil separation ramp
Data Source
AI summary
A gas turbine engine includes a first bearing compartment and a seal assembly within the first bearing compartment that includes a rotatable seal seat, a gutter radially outward of the seal seat and fixed against rotation. The gutter includes a channel on its radially inner face. A second bearing compartment is also included. A scavenge pump is in communication with a first supply line configured to supply the first bearing compartment and a second supply line configured to supply the second bearing compartment. The gutter is in communication with the scavenge pump through a gutter scavenge line. A valve between the scavenge pump and the second supply line is configured to close in response to a dry port event, such that closing the valve stops oil supply to the second supply line, while allowing oil supply to the first supply line.