Compound Epicyclic Gearbox Layout for Turbofan Misalignment Loads
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Solution Overview
Problem
Gas turbine engines face challenges in minimizing angular misalignments and resulting loads on gearboxes when transferring rotational energy from turbines to fans, which can affect durability and lifespan.
Innovation Solution
A compound epicyclic gearbox design with a sun gear, multiple compound gears, and a ring gear is used, where the sun gear has a larger diameter than the compound gears and ring gear, minimizing face widths and angular misalignments by using a compound star configuration without flexible members, allowing for larger gear diameters and reduced centrifugal loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a gearbox is used to transfer rotational energy from the turbine to the fan, then the fan can be rotated at a lower speed compared to the turbine, but various loads are imparted on the gearbox which could affect the durability and life of the gearbox
Solution Approach 1:
The gearbox is divided into multiple stages with compound gears, where each stage handles a portion of the speed reduction. This segmentation distributes the mechanical loads across multiple gear meshes rather than concentrating them in a single stage, thereby improving durability while achieving the required speed reduction ratio.
Solution Approach 2:
The patent employs a three-dimensional compound epicyclic gear arrangement with gears positioned at different radial distances from the axis. This spatial distribution in multiple dimensions allows for optimized load paths and stress distribution, enhancing gearbox reliability while maintaining compact dimensions.
2Manufacturing precision
If the sun gear has a larger diameter than the compound gears and ring gear, then face widths are minimized and angular misalignments are reduced, but the gear ratio and speed reduction capability must be maintained
Solution Approach 1:
The patent optimizes the diameter parameters of the sun gear, compound gears, and ring gear to achieve a specific geometric relationship. By carefully selecting the diameter ratio and face width parameters, the design minimizes angular misalignments while maintaining the required speed reduction ratio through the compound gear arrangement.
Solution Approach 2:
The gear system employs asymmetric diameter relationships where the sun gear has a larger diameter than the compound gears, which in turn have different diameters from the ring gear. This asymmetric configuration allows for minimized face widths and reduced angular misalignments while achieving the necessary speed reduction through the compound arrangement.
Data Source
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AI summary
A gas turbine engine (10) includes an engine core (12), a fan (14) and a gearbox (16) interconnecting the engine core (12) and the fan (14). The engine core (12) is configured to drive rotation of at least one shaft (26). The gearbox (16) is configured to transfer torque from the at least one shaft (26) to an output shaft (30) at a reduced rotational speed. The output shaft (30) is coupled to the fan (14) to drive the fan (14) at the reduced speed and provide thrust for the gas turbine engine (10).