Geared Turbofan Coupling Isolating Radial Loads
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Solution Overview
Problem
The introduction of reduction gearing in geared turbofan engines complicates the bearing support system, requiring additional support for the low pressure spool, gear train, and fan, leading to increased complexity and potential structural issues.
Innovation Solution
A torsionally rigid but radially flexible coupling is used to connect the fan shaft to the reduction gear train, with axially separated bearing locations and a support shaft passing through the sun gear, reducing direct contact and load transmission to the gearbox, thereby simplifying the bearing support system and reducing structural loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If reduction gearing is introduced to improve engine efficiency and bypass ratio, then engine efficiency and bypass ratio are improved, but bearing support system complexity increases
Solution Approach 1:
The patent combines the bearing support functions for the low pressure spool, gear train, and fan into a single integrated bearing support system. The low pressure spool is supported by bearings positioned within the gear train structure, while the fan is supported by bearings mounted on the gear train housing. This merging of support functions reduces the number of separate bearing support structures needed and simplifies the overall system architecture while maintaining the benefits of reduction gearing.
Solution Approach 2:
The gear train structure serves multiple functions: it provides the speed reduction mechanism, houses the bearings for the low pressure spool, supports the fan assembly, and transmits power from the turbine to the fan. This multi-functionality reduces the need for separate structural components and simplifies the bearing support system while maintaining engine efficiency improvements from the reduction gearing.
2Reliability
If additional bearing support is added for the gear train and fan, then bearing support is enhanced, but device complexity and structural loads increase
Solution Approach 1:
The patent merges the bearing support functions into the existing gear train structure. The low pressure spool bearings are positioned within the gear train, and the fan bearings are mounted on the gear train housing, combining multiple support functions into a single structural system rather than adding separate support structures.
Solution Approach 2:
The gear train structure is designed to serve multiple purposes: power transmission, speed reduction, and bearing support for both the low pressure spool and fan. This multi-functional design provides enhanced bearing support without proportionally increasing device complexity, as the same structural elements perform multiple functions.
3Power
If direct contact between fan shaft and gear train is maintained, then torque transmission is efficient, but radial and torsional excursions increase gearbox loading
Solution Approach 1:
The patent introduces a coupling as an intermediary element between the fan shaft and the gear train output. This coupling allows torque transmission while accommodating radial and torsional excursions, protecting the gearbox from excessive loading. The coupling acts as a buffer that transmits power efficiently while isolating the gearbox from harmful dynamic loads.
Solution Approach 2:
The coupling design allows for changes in relative position and orientation parameters between the fan shaft and gear train output. By permitting small radial and torsional movements, the coupling maintains effective torque transmission while preventing these excursions from being transmitted directly to the gearbox, thereby reducing gearbox loading.
Data Source
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AI summary
A gas turbine engine comprising: a low pressure spool, a reduction gear train (232) having a sun gear (324), a carrier (328) having a plurality of planet gears (326) attached thereto, and a ring gear (330). One of the sun gear, carrier or ring gear is connected to the low pressure shaft, and another of the sun gear, carrier and ring gear provides an output drive. A propulsive fan (212) is mounted fore of the gear train and coupled to a fan shafting arrangement (242) comprising a fan shaft (312). The coupling connects the fan shaft at a first end to the gear train at a second end and wherein the first end and second end are axial separated and radially separated and the axial separation is greater than the radial separation.