Accessory Gearbox Superposition Gearing for Dual-Spool Power Split
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Solution Overview
Problem
Existing accessory gearboxes in gas turbine engines face inefficiencies due to excessive power extraction from a single spool, which limits overall engine performance and degrades efficiency.
Innovation Solution
An accessory gearbox with a superposition gear system that distributes power from both the low and high speed spools, utilizing a superposition gear system with mechanical clutches to automatically distribute torque and provide tailored speed outputs to individual accessory components based on engine conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If power is extracted from a single spool to drive accessory components, then accessory components can be driven, but engine performance is limited and efficiency degrades
Solution Approach 1:
The power extraction system is segmented into two independent power sources (low speed spool and high speed spool) instead of relying on a single spool. Each spool can independently drive accessory components through separate drive shafts, allowing parallel power extraction that prevents any single spool from being overloaded and maintaining overall engine performance.
2Power
If power is extracted from a single spool, then accessory components can operate, but thermal efficiency, transfer efficiency, and propulsive efficiency are degraded
Solution Approach 1:
Power extraction is divided between two spools to distribute the energy demand. This segmentation allows each spool to operate within optimal efficiency ranges, preventing excessive power extraction from one spool that would cause thermal losses and efficiency degradation.
Solution Approach 2:
The system can dynamically change operating parameters by selectively engaging or disengaging clutches to connect different spools to different accessory groups. This allows optimization of power distribution based on real-time engine conditions, maintaining thermal efficiency across varying operating regimes.
3Productivity
If a superposition gear system with mechanical clutches is used to distribute power from both spools, then power distribution is optimized and accessory components operate efficiently at varying speeds, but device complexity increases
Solution Approach 1:
The superposition gear system serves multiple functions: it combines power from two spools, distributes power to multiple accessory groups, provides speed transformation, and enables clutch-controlled power routing. This multi-functionality consolidates what would otherwise require separate systems into a single integrated gearbox structure.
Solution Approach 2:
The superposition gear system acts as an intermediary mechanism that receives power from both spools through separate drive shafts and distributes it to accessory components. The mechanical clutches serve as intermediaries to selectively engage or disengage power flow paths, enabling flexible power distribution without direct mechanical coupling between all components.
Data Source
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AI summary
A turbofan engine (20) includes a first spool (30) including a first turbine (46); a second spool (32) including a second turbine (54) disposed axially forward of the first turbine (46), a first tower shaft (76) engaged to the first spool (30), a second tower shaft (78) engaged to the second spool (32) and an accessory gearbox (68) supporting a plurality of accessory components (72 ... 82) and a superposition gear system (66) disposed within the accessory gearbox (68). The superposition gear system (66) includes a plurality of intermediate gears (104) engaged to the sun gear (102) and supported in a carrier (106) and a ring gear (108) circumscribing the intermediate gears (104). The second tower shaft (78) is engaged to drive the sun gear (102); a starter (70) selectively coupled to the sun gear (102) through a starter clutch (112); a first clutch (114) for selectively coupling the first tower shaft (76) to the ring gear (108); a second clutch (116) for selectively coupling the ring gear (108) to a static structure (36) of the engine (20).