Accessory Gearbox Size Reduction via Separate Electric Oil System
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The size and arrangement of prior accessory gearboxes in gas turbine engines create a radially outward bulge in the nacelle, degrading engine efficiency by removing energy from the working medium gas as it travels over the bulged surface, which is particularly problematic in modern high bypass turbofan engines where a large percentage of thrust is produced by the fan section.
Innovation Solution
The accessory gearbox and engine oil system are reconfigured such that the oil system is offset from the gearbox, allowing for a reduced size gearbox arrangement that minimizes the bulge in the nacelle, with the oil system being driven independently, such as by electrical motors, and positioned outside the casing to maintain clearance while reducing radial dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the accessory gearbox and oil system are integrated and arranged radially outward of the main axis, then the gearbox can drive all accessories including the oil system, but the nacelle must accommodate a larger radial dimension creating a bulge that degrades aerodynamic efficiency
Solution Approach 1:
The patent divides the accessory system into two separate drive trains: the gearbox driven by the power take-off shaft for mechanical accessories, and a separate electrically powered oil system. This segmentation allows the oil system to be positioned independently, eliminating the need for it to be housed within the nacelle's radial envelope, thereby eliminating the aerodynamic bulge while maintaining complete accessory drive capability.
Solution Approach 2:
The patent replaces the mechanical drive connection between the gearbox and the oil system with an electrical power transmission system. The oil system is powered by electrical motors independent of the gearbox, allowing it to be positioned outside the nacelle's aerodynamic envelope while still providing lubrication functions, thus eliminating the radial bulge constraint.
2Ease of operation
If the oil system is positioned inside the nacelle radially outward of the gearbox, then it can be driven by the gearbox, but it forces the nacelle to accommodate additional radial space creating inefficiency
Solution Approach 1:
The patent extracts the oil system from the radial envelope defined by the gearbox and nacelle assembly. By decoupling the oil system from the gearbox drive train and positioning it independently with electrical power, the oil system can be located outside the nacelle's aerodynamic envelope, removing the constraint that previously forced the nacelle to accommodate additional radial space.
3Loss of energy
If the gearbox size is reduced by offsetting the oil system, then the nacelle aerodynamic shape is improved, but the oil system requires independent electrical power sources and positioning outside the gearbox
Solution Approach 1:
The patent replaces the mechanical power transmission connection between the gearbox and oil system with an electrical system. Electrical motors power the oil system independently, allowing it to be positioned outside the nacelle's aerodynamic envelope. This substitution eliminates the mechanical coupling that constrained the oil system's position, enabling improved nacelle aerodynamics while using electrical infrastructure already present in the aircraft.
Data Source
AI summary
An accessory system for use in a gas turbine engine, which system includes a gearbox adapted to be arranged radially outward of a main axis of the gas turbine engine and inside a nacelle, one or more engine accessories respectively connected to and driven by the gearbox, and a gas turbine engine oil system driven by a source other than the gearbox.