Aircraft Engine Dual Oil Circuits for Gearbox Lubrication Warning
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Solution Overview
Problem
Existing gas turbine engines with a single oil circuit are prone to undesirable oil flow reductions, which can lead to gearbox failure and hazardous conditions due to insufficient lubrication, especially during aircraft maneuvers or extended windmill conditions, as they rely on a single point of oil supply for journal bearings.
Innovation Solution
A dual oil circuit system is implemented, where the second oil circuit is positioned higher in the oil tank to ensure a defined oil level is maintained, incorporating a sensor to detect low oil pressure and generate a warning signal before the first oil circuit is affected, ensuring continuous lubrication to the gearbox bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single oil circuit is used to supply oil to the gearbox, then the system complexity is reduced, but the reliability of oil supply to journal bearings deteriorates due to single point failure risk
Solution Approach 1:
The oil supply system is divided into two separate oil circuits (first and second oil circuits) that independently supply oil to the gearbox. This segmentation eliminates the single point of failure present in a single circuit system, as each circuit can independently maintain oil supply to journal bearings even if the other fails.
2Reliability
If the second oil circuit outlet is positioned higher in the oil tank, then the early warning capability is improved, but the device complexity increases due to offset outlet configuration
Solution Approach 1:
The oil tank outlets are positioned at different vertical levels (offset positions) to create distinct functional zones. The higher second outlet serves as an early warning indicator for low oil levels, while the lower first outlet provides continuous supply. This local differentiation in outlet positioning enables both monitoring and supply functions within the same tank structure.
3Reliability
If a dual oil circuit system is implemented, then the reliability of continuous lubrication is improved, but the device complexity increases due to additional circuits and components
Solution Approach 1:
Both oil circuits converge to supply the same gearbox unit, merging their functions into a unified lubrication system. This combining approach allows the system to benefit from redundant supply paths while maintaining a single point of application, balancing reliability improvement with manageable system 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
This configuration prevents premature gearbox failure by maintaining sufficient oil supply and providing an early warning system for the pilot, reducing the risk of a locked fan and minimizing bearing damage, even during extended periods of reduced oil flow.
Implementation Method 1
The offset outlet of the second oil circuit is positioned higher in the oil tank than the offset outlet of the first oil circuit feeding solely to the unit
Implementation Method 2
incorporating a sensor to detect low oil pressure and generate a warning signal before the first oil circuit is affected
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A gas turbine engine (10) for an aircraft comprises a unit (30) supplied with oil from a first oil circuit (43) and a second oil circuit (45). The first oil circuit (43) and the second oil circuit (45) each are fluidly coupled with at least one inlet (48, 49) and with at least one outlet (50, 60) of the unit (30) and with at least one inlet (51, 61) and with at least one outlet (54, 55) of an oil tank (53). The first oil circuit (43) and the second oil circuit (45) are configured to receive oil from the oil tank (53) and to direct the received oil to the unit (30). The oil tank (53) is incorporating offset outlets (25, 29) to each of the oil circuits (43, 45). The offset outlet (29) of the second oil (45) circuit is positioned higher in the oil tank (53) than the offset outlet (25) of the first oil circuit (43). The second oil circuit (45) comprises a sensor (52) for sensing a feeding pressure in the second oil circuit (45). A warning signal is generated when a feeding pressure in the second oil circuit (45) is less than or equal to a predefined value.