Planet Carrier Bearing Layout for Geared Turbofan Load Paths
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Solution Overview
Problem
Gas turbine engines, particularly geared turbofan engines, require an effective support system for shaft arrangements driving the gearbox and propulsive fan, as existing designs face challenges in efficiently transmitting torque and axial loads while minimizing load through gear meshes.
Innovation Solution
A gas turbine design featuring a turbine connected via an input shaft to a gearbox with a sun gear, planet carrier, and ring gear, utilizing a rear carrier bearing system and fan shaft bearing system to support the planet carrier and fan shaft, with distinct load paths for torque and axial loads, and incorporating a curvic or spline coupling for decoupling bending between the output shaft and gearbox.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional shaft support system is used to drive the gearbox and propulsive fan, then the structural simplicity is maintained, but the mechanical efficiency decreases due to excessive load through gear meshes
Solution Approach 1:
The shaft support system is segmented into multiple independent bearing devices: a first bearing device supporting the input shaft, a second bearing device supporting the planet carrier, and a third bearing device supporting the output shaft. This segmentation allows each bearing device to independently handle specific loads, optimizing the load path and reducing unnecessary loads through gear meshes, thereby improving mechanical efficiency without requiring a fundamentally complex system architecture.
Solution Approach 2:
The planet carrier is introduced as an intermediary element between the input shaft and the output shaft, forming a planetary gear mechanism. This intermediary allows for optimized torque transmission and load distribution. The second bearing device supporting the planet carrier acts as an intermediary support, enabling the system to achieve better mechanical efficiency by properly distributing loads through the planetary gear set rather than forcing loads through simple gear meshes.
2Stability of the object's composition
If the bearing devices are positioned far from the gearbox device, then the support stability is improved, but the axial distance increases leading to longer shafts and increased bending moments
Solution Approach 1:
The bearing devices are merged with the gearbox device structure, with bearing seats integrated directly into the gearbox housing. The first bearing device is positioned within the gearbox, the second bearing device is integrated with the planet carrier inside the gearbox, and the third bearing device is positioned at the output end of the gearbox. This merging eliminates the need for long external support structures, reducing axial distances and shaft lengths while maintaining support stability through the rigid gearbox structure.
3Device complexity
If a single bearing device supports both input shaft and planet carrier, then the device complexity is reduced, but the load transmission efficiency decreases due to load interference
Solution Approach 1:
The bearing support function is segmented into three distinct bearing devices: the first bearing device exclusively supports the input shaft, the second bearing device exclusively supports the planet carrier, and the third bearing device exclusively supports the output shaft. This segmentation eliminates load interference between different rotating elements, allowing each bearing device to optimize its load path independently, thereby improving load transmission efficiency without requiring an excessively complex multi-bearing configuration for each shaft.
Data Source
AI summary
A gas turbine engine, in particular an aircraft engine, includes: a turbine connected via an input shaft device to a gearbox device having a sun gear, a planet carrier having a plurality of planet gears attached thereto, and a ring gear, the sun gear is connected to the input shaft device, the planet carrier or the ring gear is connected to a propulsive fan via an output shaft device of the gearbox device, with a rear carrier bearing device radially between the planet carrier and a part on the input shaft on the input side of the gearbox device.