Planetary Gearbox Layout for High-Ratio Turbine Speed Reduction
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Solution Overview
Problem
Aircraft gas turbine engines require a reduction gearbox to match the high rotational speed of the turbine with the propeller, which adds weight and complexity, indicating a need for a more efficient and lightweight solution.
Innovation Solution
A planetary gearbox with a sun gear, planet gear assemblies, and ring gears is used, where the planet carrier and one of the ring gears are configured to drive the load, while the rotation of the remaining ring gear is limited, achieving a high speed reduction ratio with fewer moving parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a reduction gearbox is used to match turbine speed with propeller speed, then the rotational speed compatibility is improved, but the weight and complexity of the engine increases
Solution Approach 1:
The planet gear assembly is segmented into multiple independent planet gears (first, second, third, and fourth planet gears) that can rotate independently about the sun gear. This segmentation allows each planet gear to handle specific load paths, enabling the gearbox to achieve high speed reduction ratios while distributing mechanical stresses across multiple separate components rather than requiring a single complex gear train
Solution Approach 2:
The planet carrier serves multiple functions: it supports all four planet gears, transmits torque from the sun gear to the planet gears, and simultaneously serves as an output component that can be directly coupled to the propeller shaft. This multi-functionality reduces the need for additional intermediate components, thereby reducing overall gearbox complexity while maintaining effective speed reduction
2Speed
If a reduction gearbox is used to match turbine speed with propeller speed, then the rotational speed compatibility is improved, but the weight of the engine increases
Solution Approach 1:
By segmenting the planet gear assembly into four independent planet gears that rotate independently, the design achieves high speed reduction ratios without requiring multiple stages of gear reduction. This single-stage multi-planet configuration reduces the cumulative weight that would result from multiple gear stages, each adding their own gears, bearings, and housing requirements
Solution Approach 2:
The planet carrier is merged with the output transmission path, allowing it to serve both as a support structure for the planet gears and as the direct coupling element to the propeller shaft. This merging eliminates the need for separate output shafts and additional bearing supports, thereby reducing the overall weight of the gearbox assembly while maintaining structural integrity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces the weight and complexity of the engine by achieving a high speed reduction ratio with fewer parts, requiring less lubrication and heat management, and can be adapted for various applications requiring rotational speed changes.
Implementation Method 1
a sun gear, a plurality of planet gear assemblies, each planet gear assembly having a main gear meshed with the sun gear, a fore lateral gear and an aft lateral gear disposed on opposite sides of the main gear and rotating therewith
Data Source
AI summary
In one aspect, there is provided a planetary gearbox, comprising a sun gear, a plurality of planet gear assemblies, each planet gear assembly having a main gear meshed with the sun gear, a fore lateral gear and an aft lateral gear disposed on opposite sides of the main gear and rotating therewith, a diameter of the main gear being different than a diameter of the fore and aft lateral gears, a planet carrier rotatably supporting at least some of the planet gear assemblies, and at least one fore ring gear meshed with the fore lateral gears, at least one aft ring gear meshed with the aft lateral gears, wherein one of the sun gear, the planet carrier, and the ring gears is configured to be operatively connected to an input, one is configured to be operatively connected to an output, and rotation of a remaining one is limited.