Superposition Gearbox for Dual-Spool Accessory Power Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Excessive power extraction from a single spool in a gas turbine engine, such as the high speed spool, limits operation and degrades overall performance and efficiency, particularly due to loads from the accessory gearbox.
Innovation Solution
An auxiliary gearbox drive system with a superposition gearbox that distributes power from both the low and high speed spools using a sun gear, ring gear, and carrier mechanism, coupled with one-way mechanical clutches to automatically adjust torque distribution based on engine operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If power is extracted from a single spool to drive accessory components, then accessory components can be operated, but engine efficiency degrades due to parasitic drag
Solution Approach 1:
The accessory drive system is segmented into two independent power sources (high-speed spool and low-speed spool) that can operate independently or in combination. The high-speed spool drives the accessory gearbox during ground operations, while the low-speed spool drives accessory components during flight, eliminating the need for continuous power extraction from a single spool and reducing parasitic drag.
Solution Approach 2:
The system dynamically switches between different power sources based on engine operating conditions. During ground operations, the high-speed spool provides power to the accessory gearbox. During flight, the low-speed spool takes over to drive accessory components, allowing the system to adapt to varying operational requirements and minimize energy losses.
2Reliability
If the high spool drives the accessory gearbox continuously, then accessory components remain powered, but the high spool operates beyond optimal limits
Solution Approach 1:
The power supply for accessory components is segmented into two sources: the high-speed spool during ground operations and the low-speed spool during flight. This segmentation allows the high-speed spool to operate within optimal limits during flight by transferring the accessory drive burden to the low-speed spool, while maintaining reliable power supply to accessories throughout all operational phases.
Solution Approach 2:
The low-speed spool acts as an intermediary power source that takes over the accessory drive function during flight operations. This intermediary arrangement relieves the high-speed spool of continuous accessory drive burden, allowing it to operate within optimal performance limits while ensuring uninterrupted power supply to accessory components through the low-speed spool.
3Device complexity
If a traditional single-spool drive system is used, then the structure is simple, but power distribution flexibility is limited
Solution Approach 1:
The drive system is segmented into two independent power paths: one from the high-speed spool through the accessory gearbox and another from the low-speed spool directly to accessory components. This segmentation provides flexible power distribution capability, allowing the system to adapt to different operational requirements while maintaining a relatively simple overall structure that leverages existing engine components.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A turbofan engine according to an exemplary embodiment of this disclosure includes, among other possible things, 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); a superposition gearbox (66) including a sun gear (102), 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), wherein the second tower shaft (78) is engaged to drive the sun gear (102); a first clutch (114) for selectively coupling the first tower (76) shaft to the ring gear (108); a second clutch (116) for selectively coupling the sun gear (102) to the carrier (106); and an accessory gearbox (68) driven by an output (118) of the superposition gearbox (66).