Planetary Fan Gear Architecture for Turbine Speed Mismatch
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Solution Overview
Problem
Traditional gas turbine engines face limitations in efficiently managing the speed difference between the fan and the fan drive turbine, leading to inefficiencies in energy transfer and potential misalignment stresses in the gear system.
Innovation Solution
A planetary gear system is introduced to drive the fan section, featuring a sun gear, carrier, and ring gear with bearing flanges and flexible shafts, allowing for a gear reduction mechanism that maintains alignment and reduces stress through a rigid support and bearing arrangement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a gear reduction mechanism is introduced between the fan and fan drive turbine, then the fan can rotate at slower speeds improving energy efficiency, but the device complexity increases due to additional gear components
Solution Approach 1:
The patent employs a planetary gear system where planet gears are nested around a sun gear, with the carrier holding the planet gears. This nested configuration achieves gear reduction in a compact arrangement, allowing the fan to rotate at slower speeds while maintaining manageable device complexity through space-efficient design.
Solution Approach 2:
The planetary gear system transitions from a single-stage gear reduction to a multi-dimensional gear arrangement with sun gears, planet gears, and ring gears operating in different spatial dimensions. This enables achieving the desired speed reduction ratio while keeping the overall device footprint compact, balancing energy efficiency improvements against complexity increases.
2Reliability
If a rigid support is used to fix the ring gear, then alignment is maintained reducing stress on components, but the system loses flexibility in accommodating misalignment
Solution Approach 1:
The patent introduces flexibility into the system by allowing the carrier to move dynamically relative to the ring gear through the use of bearings. This dynamic arrangement enables the system to accommodate misalignment while maintaining reliability, as the flexible connection allows for stress distribution and alignment compensation without compromising the rigid support structure.
Solution Approach 2:
The carrier acts as an intermediary element between the planet gears and the ring gear, providing a flexible connection that mediates between the rigid ring gear support and the rotating planet gears. This intermediary allows the system to maintain alignment stability through the rigid ring gear support while simultaneously accommodating misalignment through the flexible carrier connection.
3Manufacturing precision
If multiple bearing flanges are used to support the planet gears, then the gear system maintains better alignment under load, but the manufacturing complexity increases
Solution Approach 1:
The patent segments the bearing support system into multiple bearing flanges distributed around the carrier, with each flange supporting specific planet gears. This segmentation allows for precise alignment of individual planet gears while maintaining overall system manufacturability, as each bearing flange can be manufactured and positioned independently to achieve the required alignment precision.
Data Source
AI summary
A turbofan engine includes a fan section. A turbine section is in driving engagement with the fan section through a planetary gear system. The planetary gear system includes a plurality of planet gears surrounding a sun gear. A carrier supports the plurality of planet gears and includes a first carrier bearing flange. A ring gear surrounds the plurality of planet gears and includes a ring gear bearing flange. At least one ring gear carrier bearing engages the carrier bearing flange and the ring gear bearing flange. A speed change mechanism for a gas turbine is also disclosed.