Epicyclic Auxiliary Pump Drive for Bidirectional Windmilling
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Solution Overview
Problem
Existing gas turbine engine drive trains for auxiliary pumps require significant circumferential space due to the design of circumferentially spaced gears, which is inefficient and does not ensure continuous lubricant supply during windmilling operations when the primary lubricant system fails or is not powered.
Innovation Solution
An epicyclic gear train is used to drive the auxiliary pump, with a ring gear and clutches that allow rotation in either direction, reducing the space requirement and ensuring lubricant supply through an auxiliary pump, utilizing sprag clutches for directional rotation control and a separate main gear reduction system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If circumferentially spaced gears are used to drive the auxiliary pump, then the pump can be driven during windmilling operation, but a good deal of circumferential space is required
Solution Approach 1:
The auxiliary pump epicyclic gear train is nested within the outer peripheral envelope of the ring gear, allowing the pump and its drive mechanism to occupy the same circumferential space rather than requiring additional space outward from the ring gear
Solution Approach 2:
The design transitions from a circumferential arrangement of multiple spaced gears to a compact epicyclic gear train that utilizes radial and axial dimensions more efficiently, packing the drive mechanism within the ring gear's envelope rather than extending circumferentially
2Productivity
If the primary lubricant system is used to supply lubricant to the main gear reduction, then lubrication is provided during normal operation, but the system could fail or not operate during windmilling
Solution Approach 1:
The auxiliary pump serves as an intermediary lubrication system that activates when the primary lubricant system fails or cannot operate, providing backup lubrication through a separate pump and epicyclic gear train mechanism
Solution Approach 2:
The system changes operational parameters by switching from the primary lubricant system during normal operation to the auxiliary pump system during windmilling or failure conditions, ensuring continuous lubrication across different operational states
3Adaptability or versatility
If sprag clutches are used for directional rotation control, then rotation in either direction can be controlled, but the device complexity increases
Solution Approach 1:
The sprag clutches automatically engage and disengage based on the direction of rotation without requiring external control mechanisms, allowing the auxiliary pump to self-regulate its operation during windmilling versus powered operation
Solution Approach 2:
The clutch mechanism dynamically adapts to different rotational directions, automatically providing the appropriate engagement state for each direction without requiring complex control systems
Data Source
AI summary
A gas turbine engine includes a fan drive turbine driving a fan rotor through a main gear reduction. A primary lubricant system supplies lubricant to the main gear reduction. An auxiliary oil pump supplies oil to the main gear reduction. An auxiliary pump epicyclic gear train drives the auxiliary pump when the fan rotor is rotating in either direction. The main gear reduction is separate from the auxiliary pump epicyclic gear train.