Dual-Spool Differential Assembly 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 transmissions to condition output speeds.
Innovation Solution
A turbomachine dual spool transmission system with a direct drive assembly and dual spool differential that combines low and high pressure spool inputs to provide a reduced output speed range, allowing selective engagement of the low pressure spool to directly drive or be driven by a rotational member, using a gear assembly and clutch mechanism to achieve desired speed ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If power is extracted from the low pressure spool to meet accessory power requirements, then power extraction capability is improved, but the speed ratio mismatch between the low pressure spool and accessories causes high torque at low speeds
Solution Approach 1:
A dual-spool differential assembly is introduced as an intermediary device between the low pressure spool and the accessories. This differential combines inputs from both the low pressure spool and high pressure spool, acting as a mediator that reconciles the speed ratio mismatch. The differential's gear assembly transforms the wide speed range of the low pressure spool into a narrower output speed range that better matches accessory requirements, thereby reducing the torque burden while maintaining power extraction capability.
Solution Approach 2:
The patent merges the power inputs from two separate spools (low pressure and high pressure) into a single combined output through the dual-spool differential. By combining these inputs, the system leverages the advantages of both spools: the high power availability of the low pressure spool and the higher speed of the high pressure spool, resulting in a balanced output that reduces torque requirements for accessory驱动.
2Speed
If a multi-speed or variable-speed transmission is used to condition the low pressure spool output speed, then speed matching for accessories is improved, but the transmission size increases due to high torque at minimum speed
Solution Approach 1:
The dual-spool differential serves as a preliminary intermediary that conditions the speed range before power reaches the main transmission. By reducing the speed range ratio from the wide low pressure spool range (up to 10:1) to a narrower differential output range, the torque burden on the transmission is significantly reduced, allowing for a more compact transmission design.
Solution Approach 2:
The speed conditioning function is segmented into two stages: first, the dual-spool differential performs initial speed range reduction by combining spool inputs; second, the main transmission performs final speed adjustment. This segmentation allows each component to be optimized for its specific function, with the differential handling the high-torque wide-range conditioning and the transmission handling the narrower-range final adjustment, resulting in a smaller overall transmission size.
3Adaptability or versatility
If the low pressure spool operates over a wide speed range to meet varying engine conditions, then adaptability is improved, but the torque variation and speed conditioning complexity increase
Solution Approach 1:
The dual-spool differential provides a universal solution that handles multiple operating conditions through a single mechanism. It simultaneously manages wide speed range adaptation, torque limitation, and speed conditioning for various accessory requirements. The ability to draw power from both spools makes the system multi-functional, capable of adapting to different power demands without requiring separate conditioning systems for each operating regime.
Data Source
AI summary
A turbomachine dual spool transmission system can include a direct drive assembly configured to selectively allow bypassing of a dual spool differential combination output to allow selective direct engagement of a low pressure spool to directly drive a rotational member or to be directly driven by the rotational member. The system can include the dual spool differential. The dual spool differential can include a gear assembly 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.