Mid-Turbine Frame Buffer System Oil Containment
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Solution Overview
Problem
Conventional mid-turbine frame buffer systems in gas turbine engines face inefficiencies due to the need for high buffer air pressure to contain oil within the bearing compartment, leading to air leakage and energy loss, which negatively impacts engine performance.
Innovation Solution
A mid-turbine frame buffer system with a seal assembly and air compartment design that uses pressurized air from the compressor section to maintain buffer air pressure, incorporating carbon contact seals and labyrinth or brush seals to minimize air leakage, and a lubrication pump connected via a scavenge line to manage airflow and lubrication effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high buffer air pressure is used to contain oil within the bearing compartment, then oil containment is improved, but air leakage and energy loss increase
Solution Approach 1:
A seal assembly is introduced as an intermediary component between the bearing compartment and the air compartment. The seal assembly includes a first seal and a second seal that work together to prevent air leakage while maintaining the necessary buffer air pressure for oil containment, thereby resolving the contradiction between reliable oil containment and energy loss from air leakage.
Solution Approach 2:
The system utilizes pressure differential as a key parameter, where the buffer air pressure is maintained at a specific level relative to the air compartment pressure. By carefully controlling this pressure relationship and using seals designed for specific pressure differentials, the system achieves effective oil containment while minimizing air leakage and associated energy losses.
2Reliability
If high buffer air pressure is maintained to contain oil, then oil containment is improved, but air leakage into the compartment increases
Solution Approach 1:
The seal assembly acts as an intermediary barrier between the bearing compartment and the air compartment. It is specifically designed to resist the pressure differential and prevent air from leaking into the bearing compartment while still allowing the buffer air pressure to remain high enough for effective oil containment.
Solution Approach 2:
The seal assembly incorporates carbon material in at least one of the seal members, creating a composite structure that combines the sealing effectiveness of carbon with the structural support of other materials. This composite approach enhances the seal's ability to prevent air leakage under high buffer air pressure conditions.
3Device complexity
If conventional breather air tubes are used, then system simplicity is maintained, but energy loss and performance impact occur
Solution Approach 1:
The invention extracts and eliminates the conventional breather air tube from the system. By removing this component entirely and replacing it with a seal assembly that prevents air leakage at the source, the system achieves better energy efficiency and performance without the drawbacks associated with breather air tubes.
Solution Approach 2:
Instead of using breather air tubes that allow air leakage (a harmful effect), the invention converts the approach by using seals to prevent air leakage entirely. The buffer air pressure system, which could potentially cause leakage, is now harnessed to work in conjunction with the seals to actively prevent air from entering the bearing compartment, turning a potential harm into a benefit.
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
This design reduces air leakage and energy loss by maintaining buffer air pressure within the bearing compartment, enhancing engine performance by capturing energy in the downstream turbo machinery and eliminating the need for conventional breather air tubes.
Implementation Method 1
The buffer air pressure outside of the bearing compartment must remain higher than the pressure inside the compartment so that air always leaks into the compartment, not out
Implementation Method 2
seals are used to contain the oil at static-to-rotating interfaces
Implementation Method 3
The air seals includes at least one of a labyrinth seal and a brush seal
Implementation Method 4
a lubrication pump is fluidly connected to the bearing compartment by a scavenge line
Data Source
AI summary
A mid-turbine frame buffer system for a gas turbine engine includes a mid-turbine frame that supports a shaft by a bearing. An air compartment and a bearing compartment are arranged radially inward of the mid-turbine frame. The bearing compartment is arranged within the air compartment and includes first and second contact seals arranged on either side of the bearing. The air compartment includes multiple air seals. A high pressure compressor is fluidly connected to the air compartment and is configured to provide high pressure air to the air compartment. A method of providing pressurized air to a buffer system includes sealing a bearing compartment with contact seals, surrounding the bearing compartment with an air compartment, and supplying high pressure air to the air compartment.