Split-Torque Fan Gear Architecture Without a Ring Gear
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Solution Overview
Problem
Existing gas turbine engines face challenges in reducing the rotational speed of the fan efficiently, particularly in high-bypass flow configurations, where traditional gear architectures can be complex and require rigorous lubrication systems.
Innovation Solution
A split torque geared architecture is introduced, utilizing an input and output gear arrangement with multiple idler gears that are axially adjacent and circumferentially mounted, providing a gear reduction ratio of 8:1 without the need for a ring gear, simplifying the design and reducing lubrication requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a traditional epicyclic gear train with sun gear and ring gear is used, then the fan rotational speed can be reduced, but the gear architecture becomes complex and requires rigorous lubrication systems
Solution Approach 1:
The patent extracts and eliminates the ring gear component from the traditional epicyclic gear train, replacing it with a simplified arrangement where planet gears directly mesh with a sun gear. This extraction of the unnecessary ring gear reduces structural complexity while maintaining the speed reduction function through the planet carrier mechanism
Solution Approach 2:
The gear system is segmented into distinct functional components: a central sun gear, multiple planet gears mounted on planet carriers, and a stationary outer ring. This segmentation allows each component to perform its specific function independently, simplifying the overall architecture while achieving the required 8:1 gear reduction ratio
2Speed
If a traditional epicyclic gear train with ring gear is used, then the fan rotational speed can be reduced, but the lubrication requirements become rigorous
Solution Approach 1:
By removing the ring gear component, the patent reduces the number of gear mesh interfaces that require lubrication. The simplified architecture with only sun-planet gear meshes reduces lubrication points and associated system complexity, making the system easier to manufacture and maintain
3Speed
If multiple sets of idler gears are used, then the gear reduction ratio increases, but the device complexity increases
Solution Approach 1:
The planet carriers are configured to rotate on the sun gear axis, creating a dynamic mechanism that achieves high gear reduction ratios without adding multiple static idler gear sets. This dynamic arrangement allows the same components to serve multiple functions across different operational states
Solution Approach 2:
The planet gears and carriers serve multiple functions simultaneously: they provide gear reduction, support radial loads, and enable the desired speed ratio through their rotational motion on the sun gear axis. This multi-functionality eliminates the need for separate idler gear sets that would otherwise be required
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 effectively reduces the fan's rotational speed, enhances thrust efficiency, and simplifies the gear train, leading to improved performance and reduced maintenance needs in high-bypass gas turbine engines.
Implementation Method 1
a first gear in the first set of idler gears meshes with the input gear and a second gear in the second set of idler gears meshes with the output gear
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A gas turbine engine (20) includes a turbine section (28) configured to rotate about an engine axis (X) relative to an engine static structure (36). A fan section (22) is configured to rotate about the engine axis (X) relative to the engine static structure (36). A geared architecture (48) operatively connects the fan section (22) to the turbine section (28). The geared architecture (48) includes an input gear (60; 160) and an output gear (62; 162) both configured to rotate about the engine axis (X). A set of idler gears (66; 166, 266) are arranged radially outward relative to and operatively coupling with the input and output gears (60, 62; 160, 162).