Geared Turbofan Planet Gear Layout With Rolling Bearing Load Sharing
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Solution Overview
Problem
Current geared turbofan engines face limitations in thermal, transfer, and propulsive efficiencies, despite the use of speed reduction devices like epicyclical gear assemblies, necessitating further improvements in engine performance.
Innovation Solution
A gear system for geared turbofan engines is designed with a set of planet gears, a carrier supporting these gears, and rolling element bearing assemblies, including configurations such as multiple rows of roller, ball, or tapered roller bearings, to optimize load distribution and efficiency within a defined design space, allowing for increased power transfer and compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If epicyclical gear assemblies are used to reduce fan speed, then propulsive efficiency is improved, but thermal and transfer efficiencies remain limited
Solution Approach 1:
The patent optimizes gear system parameters including planet gear count (3-5 gears), bearing assembly dimensions, and carrier geometry to minimize energy losses. By carefully selecting and adjusting these parameters, the system achieves improved thermal efficiency while maintaining the propulsive efficiency benefits of speed reduction.
Solution Approach 2:
The patent replaces traditional journal bearings with rolling element bearing assemblies, substituting a mechanical system with higher friction characteristics with one that uses rolling contact to reduce friction and improve transfer efficiency. This substitution directly addresses the thermal efficiency limitation by reducing mechanical energy losses.
2Power
If more planet gears are added to distribute load, then power transfer efficiency improves, but device complexity increases
Solution Approach 1:
The patent applies the principle of partial action by selecting an optimal number of planet gears (3-5) rather than maximizing the number. This partial approach achieves sufficient load distribution and power transfer efficiency without unnecessarily increasing device complexity, maintenance requirements, and space requirements.
Solution Approach 2:
The patent employs composite bearing assemblies that integrate multiple bearing types (tapered roller bearings, spherical bearings) within a single carrier structure. This composite approach consolidates multiple functions into integrated components, reducing overall system complexity while maintaining effective load distribution across the planet gears.
3Loss of energy
If rolling element bearing assemblies are used instead of traditional bearings, then transfer efficiency improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent segments the bearing support function by using multiple rolling element bearing assemblies distributed across different carrier locations. Each bearing assembly handles specific load components, allowing for modular manufacturing and assembly. This segmentation reduces the precision requirement for any single bearing while maintaining overall high transfer efficiency through the collective performance of multiple bearings.
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
The gear system enhances the power transfer efficiency and compactness of the engine by distributing loads effectively through optimized bearing assemblies and planet gear configurations, leading to improved thermal and propulsive efficiencies.
Implementation Method 1
rolling element bearing assemblies, including configurations such as multiple rows of roller, ball, or tapered roller bearings
Data Source
Figure 1
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Figure 4~5
AI summary
A gear system (48) for a geared turbofan engine (20) includes a sun gear (62) defining a sun gear diameter (68). A rotating carrier (70) drives a fan (42). The carrier (70) defines an outer carrier diameter (72) and an inner carrier diameter (74). A non-rotating ring gear (82) defines a ring gear diameter (84) and the ring gear diameter (84) is smaller than the outer carrier diameter (72). A set of planet gears (102) are mounted on rolling element bearing assemblies (90). Each roller element bearing assembly (90) is supported within a space defined between the carrier outer diameter (72) and the carrier inner diameter (74). Each of the sun gear (62), ring gear (82) and planet gears (102) are centered along a gearbox centerline transverse to an engine longitudinal axis (A) and the gear system (48) provides a speed reduction ratio between 3:1 and 5:1.