Planetary Reduction Gearbox Lubrication Baffles for Windage Control
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Solution Overview
Problem
Aircraft engine gearboxes, particularly those in turboprop engines, face challenges due to their weight and complexity, which are exacerbated by the need for a reduction gearbox to manage the high rotational speed of turbines for propeller drive, leading to inefficiencies and increased temperature due to windage and churning in lubrication systems.
Innovation Solution
A reduction gearbox with a planetary gear arrangement and an advanced lubrication handling system featuring baffles and apertures to manage lubrication oil flow, reducing windage and churning, and enhancing oil scavenging, thereby improving efficiency and reducing temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a reduction gearbox is used to reduce turbine rotational speed for propeller drive, then the propeller can be driven at appropriate speed with increased torque, but the gearbox adds weight and complexity to the engine
Solution Approach 1:
The planetary gear system is divided into multiple independent planet gear assemblies, each handling specific gear meshing zones. This segmentation allows for modular design and maintenance while achieving the overall speed reduction function
Solution Approach 2:
Multiple planet gear assemblies are combined in a single gearbox housing, with their outputs merged to drive the propeller shaft. This consolidation achieves speed reduction while minimizing the overall number of separate components
2Speed
If a reduction gearbox is used to reduce turbine rotational speed for propeller drive, then the propeller can be driven at appropriate speed with increased torque, but the gearbox adds weight to the engine
Solution Approach 1:
The gear tooth geometry and material properties are optimized to achieve the required torque transmission with minimal material usage, reducing the overall weight of the gearbox while maintaining strength
Solution Approach 2:
Advanced composite materials are used in the gear components and housing to reduce weight while maintaining or improving mechanical strength and durability compared to traditional materials
3Reliability
If lubrication oil is used in the gearbox, then gear friction is reduced, but windage and churning increase temperature and reduce efficiency
Solution Approach 1:
Baffles with selectively positioned apertures create localized lubrication zones at critical gear meshing points, providing lubrication only where needed rather than filling the entire gearbox, thereby reducing windage and churning losses
Solution Approach 2:
The baffle structure acts as an intermediary between the lubrication system and gear components, controlling oil flow to deliver lubrication precisely at the gear contact zones while preventing excessive oil movement that causes windage
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 solution effectively reduces the weight and complexity of the gearbox while improving lubrication efficiency, leading to increased engine performance and reduced temperature, thus addressing the inefficiencies and challenges posed by existing systems.
Implementation Method 1
a first set of baffles including a fore ring gear baffle disposed on a fore side of the planetary gear arrangement proximate the fore ring gear, and an aft ring gear baffle disposed on an aft side of the planetary gear arrangement proximate the aft gear ring
Implementation Method 2
The main gear has a main gear pitch diameter and the fore and aft lateral gears have a lateral gear pitch diameter. The fore ring gear is meshed with the fore lateral gears. The aft ring gear is meshed with the aft lateral gears.
Implementation Method 3
a lubrication handling system. The planetary gear arrangement includes a sun gear, planet gear assemblies, a fore ring gear, and an aft ring gear
Data Source
Figure 1
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AI summary
A reduction gearbox (38) is provided that includes a planetary gear arrangement (42) disposed in a casing (44) and a lubrication handling system (96). The planetary gear arrangement (42) includes a sun gear (46), planet gear assemblies (48), and independent fore and aft ring gears (50A, 50B). Each planet gear assembly (48) has fore and aft lateral gears (60, 62) respectively disposed on opposite sides of a main gear (58) and rotating therewith. The main gear (58) has a main gear pitch diameter (PDMG) and the fore and aft lateral gears (60, 62) having a lateral gear pitch diameter (PDLG). The fore ring gear (50A) is meshed with the fore lateral gears (60). The aft ring gear (50B) is meshed with the aft lateral gears (62). The planet gear assemblies (48) are in communication with an output (40). The lubrication handling system (96) includes a fore ring gear baffle (98A) and an aft ring gear baffle (98B).