Compound Epicyclic Gearbox Layout for Turbofan Load Misalignment
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Solution Overview
Problem
Gas turbine engines face durability and life span issues due to loads imparted on gearboxes when transferring rotational energy from turbines to output shafts, particularly when reducing rotational speed for fans, leading to misalignments and increased loading on gearbox components.
Innovation Solution
A compound epicyclic gearbox with a sun gear, multiple compound gears, and a ring gear is used, where each compound gear includes a first-stage and second-stage gear with smaller diameters, and optimized face widths to minimize angular misalignments and loads, allowing for efficient torque transfer from the turbine to the fan at reduced rotational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If rotational energy is transferred from turbine to output shaft using gearbox, then rotational speed reduction is achieved, but loads and misalignments on gearbox components increase
Solution Approach 1:
The patent divides the single-stage gearbox into multiple stages (first-stage gear, second-stage gear, third-stage gear) with compound gears. Each stage handles a portion of the speed reduction, distributing the mechanical loads across multiple gear interfaces rather than concentrating them in a single stage, thereby reducing misalignments and improving reliability.
Solution Approach 2:
The patent introduces axial spacing between gear stages along the power shaft. The first-stage, second-stage, and third-stage gears are positioned at different axial locations, creating a multi-dimensional gear arrangement that allows for better load distribution and reduced misalignments compared to a single-plane configuration.
2Device complexity
If gearbox components are designed with smaller diameters, then device complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the face width-to-diameter ratios for each gear stage within specific ranges (first-stage: 0.05-0.15, second-stage: 0.08-0.18, third-stage: 0.10-0.20). These parameter changes allow the use of smaller diameter gears while maintaining adequate load capacity and alignment tolerance, balancing device complexity with manufacturing precision requirements.
Data Source
AI summary
A gas turbine engine includes an engine core, a fan and a gearbox interconnecting the engine core and the fan. The engine core is configured to drive rotation of at least one shaft. The power gearbox is configured to transfer torque from the at least one shaft to an output shaft at a reduced rotational speed. The output shaft is coupled to the fan to drive the fan at the reduced speed and provide trust for the gas turbine engine.