Accessory Gearbox Radial Packaging in Gas Turbine Nacelle
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Solution Overview
Problem
Conventional gas turbine engines with geared fan-drive architectures face challenges in packaging the accessory gearbox and accessories, particularly due to space constraints and exposure to high temperatures, especially when the gearbox is located near the aft of the engine, requiring a long driveshaft and complex mounting configurations.
Innovation Solution
The gas turbine engine design includes a driveshaft extending through the inner wall, with a bevel gear coupling the driveshaft to the accessory drive, and multiple accessory drives positioned at various angles relative to the central axis, allowing for a 'T' or 'I' shaped gearbox configuration within the nacelle to efficiently package and cool the accessory gearbox, with driveshafts and gearboxes positioned to optimize space and thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the accessory gearbox is located near the aft of the engine, then the packaging space is available, but the driveshaft becomes relatively long and the gearbox is exposed to high temperatures
Solution Approach 1:
The accessory gearbox is repositioned from a longitudinal arrangement (aft of engine) to a radial arrangement (circumferential side of compressor), changing the spatial dimension of packaging. This allows the gearbox to be located in a cooler region while maintaining compact packaging through the radial伸出 configuration
2Device complexity
If the accessory gearbox is mounted to the fan case, then the packaging is simplified, but the driveshaft length increases and thermal management becomes difficult
Solution Approach 1:
The accessory gearbox is mounted to an intermediate structure (compressor case or nacelle) rather than directly to the fan case, serving as a mediator that reduces the driveshaft length while maintaining packaging simplicity. This intermediate mounting location provides a more favorable position for the gearbox
3Temperature
If a long driveshaft is used to connect the compressor to the accessory gearbox, then the gearbox can be positioned for better cooling, but the device complexity and space requirements increase
Solution Approach 1:
The driveshaft connection is segmented into multiple sections with intermediate support bearings, allowing the driveshaft to be extended radially while maintaining structural integrity and reducing complexity. This segmentation enables better thermal management through distributed support points
Data Source
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AI summary
An example gas turbine engine (20) includes, among other things, a nacelle (66) having an inner wall (70) providing a bypass duct (78) of a gas turbine engine (20), and an outer wall (74); an accessory gearbox (86) is received between the inner wall (70) and the outer wall (74) of the nacelle (66); and an accessory drive (D4, D5) of the accessory gearbox (86) is configured to rotate about an accessory drive axis (AT) that is transverse to a central axis (A) of the gas turbine engine (20).