Dual-Spool Differential Transmission for Low-Speed Torque Reduction
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Solution Overview
Problem
Aircraft engine manufacturers face challenges in extracting accessory power from the low pressure spool due to differences in optimum speed ratios between accessories and the low pressure spool, leading to high torque at low speeds and the need for complex multi-speed or variable-speed transmissions to condition output speeds.
Innovation Solution
A turbomachine dual spool differential system with a gear assembly comprising a ring gear, sun gear, and planetary gears, along with a clutch that selectively engages the carrier and ring gear to achieve a reduced output speed range by combining low and high pressure spool inputs, allowing for adjustable gear ratios to match accessory speed requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If power is extracted from the low pressure spool, then accessory power availability is improved, but the speed ratio mismatch causes high torque at low speed requiring complex transmissions
Solution Approach 1:
The patent combines the low pressure spool and high pressure spool into a dual-input planetary gear system where both spools drive the planetary gears simultaneously. This merging of power sources allows the system to achieve the required output speed range without complex transmissions, as the combined input provides sufficient torque across all operating conditions while maintaining simpler gear architecture.
Solution Approach 2:
The patent changes the operating parameters by utilizing both low pressure and high pressure spools with different speed characteristics. By varying the contribution of each spool based on operating conditions, the system can maintain optimal speed ratios for accessories across the full operating range, eliminating the need for complex multi-speed transmissions.
2Adaptability or versatility
If complex multi-speed transmissions are used to condition LS output speed, then accessory speed matching is improved, but transmission size increases due to high torque at minimum speed
Solution Approach 1:
The dual spool planetary gear system merges two power sources to provide sufficient torque at all operating speeds, eliminating the need for large, heavy transmission components that would be required to handle high torque from a single low pressure spool alone.
Solution Approach 2:
The planetary gear system serves multiple functions simultaneously: it combines power from two spools, provides speed conditioning for accessories, and handles torque variation across the operating range. This multi-functionality reduces the need for separate heavy-duty components.
3Power
If constant power extraction is required from LS, then accessory power supply is improved, but torque at minimum speed increases requiring larger transmissions
Solution Approach 1:
The system merges power from both low pressure and high pressure spools to maintain constant power extraction for accessories. The high pressure spool contributes additional torque, especially at minimum speeds, allowing the system to meet power requirements without generating excessive torque that would require larger transmission components.
Data Source
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AI summary
A turbomachine dual spool transmission system can include a transmission assembly (600) configured to connect to a combination output (107) of a dual spool differential (100) at a transmission input (603) to be driven by the combination output to turn a transmission output (605). The transmission assembly can be configured to provide a first output gear ratio in a first state and a second output gear ratio in a second state. The system can include the dual spool differential (100). The dual spool differential can include a gear assembly (101) configured to combine a low pressure spool input and a high pressure spool input into a combination output to provide an output speed range smaller than a low pressure speed range alone.