Accessory Gearbox Layout for Multi-Spool Engines Without Tower Shafts
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Solution Overview
Problem
Multi-spool gas turbine engines with asymmetrically mounted accessory gear boxes increase engine diameter and impact aerodynamic performance due to the extension of the tower shaft through the gaspath.
Innovation Solution
A reverse flow gas turbine engine design with a split compressor system and axially mounted accessory gearbox, utilizing first and second gear trains to connect the LP turbine to the LP compressor and HP spool, eliminating the need for a tower shaft and externally mounted gear train, thereby minimizing engine envelope diameter and improving aerodynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a tower shaft is used to drive an asymmetrically mounted accessory gear box, then the accessory gear box can be driven, but the engine diameter increases and aerodynamic performance deteriorates
Solution Approach 1:
The invention extracts and eliminates the tower shaft from the engine architecture. Instead of using a traditional tower shaft to drive an asymmetrically mounted accessory gear box, the patent integrates the accessory gear box drive directly into the compressor assembly, removing the problematic external shaft structure that increased engine diameter and harmed aerodynamics.
Solution Approach 2:
The invention merges the accessory gear box drive function with the compressor assembly. The accessory gear box is positioned to be driven directly by the compressor rotor through integrated gearing, combining what were previously separate functions (compressor operation and accessory drive) into a unified structure that eliminates the need for a separate tower shaft.
2Ease of operation
If a tower shaft is extended through the gaspath to drive the accessory gear box, then the accessory gear box can be driven, but aerodynamic performance is impacted
Solution Approach 1:
The invention extracts and removes the tower shaft that extended through the gaspath. By eliminating this structural element, the patent prevents the aerodynamic interference that would have been caused by the shaft passing through the airflow path, thereby preserving optimal aerodynamic performance.
Solution Approach 2:
The invention merges the accessory drive mechanism with the compressor housing and rotor assembly, positioning all drive components within the compressor structure rather than extending them through the gaspath. This integration ensures that no shafts or mechanical elements protrude into the airflow path.
3Power
If a tower shaft and upstream transfer case are used, then power can be transmitted to the accessory gear box, but engine weight increases
Solution Approach 1:
The invention extracts and eliminates both the tower shaft and the upstream transfer case from the power transmission system. By removing these intermediate power transmission components, the patent significantly reduces the overall engine weight while maintaining the ability to drive the accessory gear box through a more direct and integrated mechanism.
Data Source
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AI summary
A multi-spool gas turbine engine (10) comprises a low pressure (LP) spool (20) and a high pressure (HP) spool (40). The LP spool (20) and the HP spool (40) are independently rotatable about an axis (17). The LP spool (20) has an LP compressor (22) and an LP turbine (21). The HP spool (40) has an HP turbine (41) and an HP compressor (42). The LP compressor (22) is axially positioned between the HP compressor (42) and an accessory gear box (AGB) (50). The AGB (50) is drivingly connected to the HP spool (40) through the center of the LP compressor (22).