Bidirectional Oil Pump Gear Train for Fan Windmilling Lubrication
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Solution Overview
Problem
Gas turbine engines face challenges in lubricating gear reductions during windmilling operations, where the fan rotor can rotate in either direction, requiring efficient lubrication systems that occupy large package spaces and must function under adverse conditions such as windmilling in flight or on the ground with varying wind speeds.
Innovation Solution
A gear train assembly with a main input drive gear connected to an oil pump through first and second pinion gears, utilizing directional clutches to ensure lubrication in either direction of fan rotation, allowing the engine to operate under windmill conditions for extended periods and in negative gravity conditions, with the oil pump rotatable about a common axis with the pinion gears and utilizing sprag clutches for efficient rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a gear reduction is included between the turbine and fan rotor to enable windmilling operation in either direction, then the engine can operate under windmill conditions, but the package space required increases
Solution Approach 1:
The gear train is segmented into multiple independent pathways: a first pinion gear and first gear for one rotation direction, and a second pinion gear and second gear for the opposite rotation direction. This segmentation allows each pathway to be optimized independently and enables bidirectional windmilling operation without requiring a single complex gear system that would occupy larger space.
Solution Approach 2:
The system dynamically switches between different gear pathways based on the direction of fan rotation. During windmilling, the appropriate pinion-gear pair is engaged depending on whether the fan rotates in the first or second direction, allowing the system to adapt to varying operational conditions while maintaining a compact structure.
2Reliability
If directional clutches are used to enable lubrication during bidirectional windmilling, then continuous lubrication is ensured, but the device complexity increases
Solution Approach 1:
The sprag clutches are designed to automatically engage and disengage based on the direction of rotation, without requiring external control mechanisms. When the fan rotates in a specific direction, the corresponding clutch automatically engages to transmit power to the oil pump, ensuring continuous lubrication without adding complex control systems.
Solution Approach 2:
The sprag clutches act as intermediary elements between the pinion gears and the oil pump, selectively transmitting rotational power in the appropriate direction. This intermediary mechanism simplifies the overall system by providing automatic directional control without requiring complex valve systems or external actuation mechanisms.
3Volume of moving object
If a compact gear train is designed to reduce package space, then the engine size is reduced, but the ability to handle adverse windmilling conditions is compromised
Solution Approach 1:
The patent merges multiple functions into a single compact gear train assembly: bidirectional windmilling capability, automatic directional clutch engagement, and oil pump drive are all integrated into one unified structure. This merging allows the system to handle adverse windmilling conditions while maintaining a reduced engine size compared to separate systems.
Solution Approach 2:
The gear train assembly serves multiple functions simultaneously: it provides gear reduction for normal operation, enables bidirectional windmilling, drives the oil pump for lubrication, and incorporates directional clutches for automatic adaptation. This multi-functionality allows a compact design to handle various windmilling conditions without requiring additional specialized components.
Data Source
AI summary
A gas turbine engine including a fan and an oil pump operatively connected to the fan by a main input drive gear, the drive gear rotating when the fan rotor rotates in either a first or second direction of the fan. Further included is a gear train intermediate the main input drive gear and the oil pump, the gear train including a first and second pinion gear, the first and second pinion gear each driven by the main input drive gear, the first pinion gear driving a first gear through a first clutch, the second pinion gear driving a second gear through a second clutch. Only one of the clutches transmits rotation from the respective pinion gear to the respective gear when the fan is rotating in the first direction, with the only the other clutch transmitting rotation when the fan is rotating in the second direction.