Multi-Circuit Buffer System for Gas Turbine Bearing Lubricant Containment
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Solution Overview
Problem
Gas turbine engines face challenges in maintaining lubricant containment within bearing compartments due to differential pressure requirements across seals, which existing systems struggle to manage effectively across varying power conditions.
Innovation Solution
A buffer system with dual bleed air supplies, including a controller that selects between low and high pressure bleed air to pressurize seals in bearing compartments, ensuring lubricant containment without exceeding temperature limitations, and optionally includes a conditioning device for cooling the buffer supply air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single bleed air supply is used for bearing compartment pressurization, then the system is simpler, but the system cannot effectively maintain lubricant containment across varying power conditions
Solution Approach 1:
The buffer system is divided into multiple independent circuits (first circuit, second circuit, third circuit), each capable of supplying buffer air to different bearing compartments. This segmentation allows each circuit to be optimized for specific power conditions while maintaining overall system reliability for lubricant containment across varying operating conditions.
Solution Approach 2:
The controller dynamically selects which bleed air supply (first, second, or third) to activate based on the current power condition of the gas turbine engine. This dynamic adaptation ensures that the appropriate pressure level is provided to maintain seal effectiveness and lubricant containment regardless of whether the engine is operating at high power, low power, or intermediate conditions.
2Reliability
If high pressure bleed air is used to pressurize seals, then lubricant containment is improved, but temperature limitations may be exceeded
Solution Approach 1:
Different bearing compartments receive buffer air from different bleed air supplies based on their specific requirements. The controller matches the pressure level of the bleed air supply to the local requirements of each bearing compartment, providing high pressure where needed for containment while avoiding excessive temperature in compartments that cannot tolerate it.
Solution Approach 2:
The controller acts as an intermediary that selects and regulates which bleed air supply connects to each bearing compartment. It mediates between the high pressure available in the bleed air system and the temperature sensitivity of the bearing compartment seals and lubricant, ensuring containment without thermal damage.
3Adaptability or versatility
If multiple bleed air supplies are implemented, then adaptability to power conditions is improved, but the device complexity increases
Solution Approach 1:
The buffer system is designed with multiple circuits that can each serve multiple functions depending on the power condition. The same bearing compartment can receive buffer air from different bleed air supplies at different times, making the system universally adaptable to various operating conditions without requiring separate dedicated systems for each condition.
Solution Approach 2:
The system changes the pressure parameter of the buffer air supply by selecting different bleed air supplies based on power condition. At high power, high pressure bleed air is used; at low power, lower pressure bleed air is used. This parameter change allows the system to adapt to varying operating conditions while maintaining a relatively compact 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 system effectively maintains lubricant containment across different power conditions by optimizing pressure and temperature, minimizing lubricant leakage and performance impact on the gas turbine engine.
Implementation Method 1
A predetermined differential pressure must be maintained across the seals so the lubricant cannot leak past the seals
Implementation Method 2
the controller is configured to command cooling of the second buffer supply air by the conditioning device prior to communicating it to the second bearing structure
Data Source
AI summary
A gas turbine engine according to an exemplary aspect of the present disclosure includes, among other things, a shaft and first and second bearing structures that support the shaft. Each of the first bearing structure and the second bearing structure includes a bearing compartment that contains a lubricant and a seal that contains the lubricant within the bearing compartments. A buffer system is configured to pressurize the seals to prevent the lubricant from escaping the bearing compartments. The buffer system includes a first circuit configured to supply a first buffer supply air to the first bearing structure, a second circuit configured to supply a second buffer supply air to the second bearing structure, and a controller configured to select between at least two bleed air supplies to communicate the first buffer supply air and the second buffer supply air.