Bidirectional Gear Train Clutching for Windmilling Oil Pump Drive
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Solution Overview
Problem
Gas turbine engines face challenges in lubricating gear reductions during wind milling operations, where the fan rotor can rotate in either direction, requiring a gear train that can efficiently supply oil to the gear reduction under adverse conditions, including wind milling and potential oil system interruptions.
Innovation Solution
A gear train with two sets of gears connected by clutches, where one set has an even number of gears and the other an odd number, ensuring torque transmission in the same direction and slipping in alternate directions, driving an oil pump to supply oil to the gear reduction, even during reverse rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional oil pump is used in the gear reduction, then it can supply oil during normal operation, but it cannot supply oil during wind milling when rotation direction is reversed
Solution Approach 1:
The patent applies the dynamics principle by making the oil pump's drive mechanism adaptable to changing rotation directions. The system dynamically switches between forward and reverse pinion gears based on the input shaft's rotation direction, ensuring the oil pump receives consistent rotational drive regardless of whether the turbine is rotating forward or in reverse during wind milling operations.
Solution Approach 2:
The patent changes the operational parameters of the gear train by introducing two separate pinion gears (forward and reverse) that engage with different sets of gears depending on rotation direction. This parameter change allows the system to maintain proper gear engagement and oil pump operation across varying rotational conditions, transforming a single-direction system into a bidirectional capable system.
2Device complexity
If the fan rotor is directly connected to drive the propulsor rotor, then the structure is simple, but the gear reduction cannot receive adequate lubrication during wind milling
Solution Approach 1:
The patent segments the drive system into two independent pathways: one for normal forward operation and another for reverse wind milling operation. By dividing the gear train into forward-driven and reverse-driven gear sets, each with its own pinion gear, the system ensures that lubrication can be effectively delivered regardless of which pathway is active, resolving the contradiction between structural simplicity and lubrication reliability.
Solution Approach 2:
The patent introduces an intermediary mechanism consisting of the dual pinion gears and associated clutches that mediate between the input shaft and the oil pump. This intermediary system ensures that rotational energy is consistently transmitted to the oil pump regardless of the input direction, acting as a buffer that maintains lubrication reliability while allowing the overall system structure to remain relatively simple.
3Adaptability or versatility
If a gear train with multiple clutches is used to enable bidirectional operation, then oil can be supplied during wind milling, but the device complexity increases
Solution Approach 1:
The patent merges the functions of multiple clutches into a more integrated gear train design where the forward and reverse pinion gears share common structural elements. By combining certain functions and using shared components where possible, the system achieves bidirectional operation capability while minimizing the increase in overall device complexity compared to using completely separate clutch mechanisms for each direction.
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 lubrication of the gear reduction during wind milling in either direction and under various operational conditions, including extended shutdowns and high wind speeds, preventing damage and allowing safe engine operation.
Implementation Method 1
Each clutch transmits rotation driven in a same driving direction and slips in an alternate driving direction
Data Source
AI summary
An oil system for a gas turbine engine includes an oil pump driven by a gear train having a main input drive gear rotating when a propulsor rotor rotates. The gear train includes two sets of gears joined by two connection shafts each having a clutch. The first set of the gears include a forward input gear and a reverse input gear each driven by the main input drive gear. The forward and the reverse input gears drive a pinion gear in the second set of gears through a clutch. Each clutch transmits rotation driven in a same driving direction and slips in an alternate driving direction. The first set of the gears has an even number of the gears, and the second set of the gears has an odd number of the gears.