Split Accessory Gear Box for Nacelle Radial Thickness Reduction
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Solution Overview
Problem
The radial thickness of the nacelle in gas turbine engines is increased due to a single accessory gear box, which is undesirable with larger fan diameters and increased bypass air volume, necessitating a reduction in nacelle thickness.
Innovation Solution
The accessory gear box is split into two portions, each driven by a separate drive shaft, allowing for a more compact configuration within the nacelle, with one gear box driving fuel and lubricant pumps and the other driving a starter, thereby reducing the radial thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single accessory gear box is provided at one circumferential location in the nacelle, then the accessory drive functionality is maintained, but the radial thickness of the nacelle becomes relatively large
Solution Approach 1:
The single accessory gear box is divided into two separate gear boxes positioned at different circumferential locations within the nacelle. This segmentation allows the accessory drive functions to be distributed, reducing the radial thickness required at any single location while maintaining all necessary accessory drive capabilities through separate drive shafts
2Productivity
If the fan diameter is increased to increase bypass air volume, then propulsion performance is improved, but the inner diameter of the nacelle must increase and the radial thickness becomes undesirable
Solution Approach 1:
By segmenting the accessory gear box into two portions located at different circumferential positions, the design enables larger fan diameters for increased bypass air volume without requiring excessive radial thickness in the nacelle structure
3Length of stationary object
If the accessory gear box is split into two portions driven by separate drive shafts, then the radial thickness of the nacelle is reduced, but the device complexity increases
Solution Approach 1:
The accessory gear box is segmented into two portions, each driven by its own drive shaft, reducing nacelle radial thickness. The segmentation is designed to simplify the overall configuration by allowing independent positioning and driving of each gear box portion
Data Source
Figure 1
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AI summary
A nacelle for incorporation into a gas turbine engine has an inner wall defining a bypass duct, and an outer wall. At least one drive shaft extends through the inner wall. The at least one drive shaft is connected to a gas turbine engine receiving the nacelle. The at least one drive shaft is connected to drive at least two accessory gear boxes, with the at least two accessory gear boxes being received between the inner and outer walls of the nacelle. A gas turbine engine is also disclosed.