Dual Spool Transmission Assembly for Accessory Speed Conditioning
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Solution Overview
Problem
Aircraft engine manufacturers face challenges in extracting accessory power from the low pressure spool due to the wide speed range and high torque at low speeds, which complicates the design of transmission systems needed to condition the output speed for accessories.
Innovation Solution
A dual spool transmission system that includes a gear assembly combining low and high pressure spool inputs into a combination output, using a transmission assembly with planetary gears and a clutch to selectively switch between two gear ratios, reducing the output speed range and minimizing torque at low speeds.
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 wide speed range and high torque at low speed increase transmission system complexity
Solution Approach 1:
The transmission system is divided into two distinct gear ratio states: a first gear ratio for high torque conditions and a second gear ratio for normal operating conditions. This segmentation allows the system to handle the wide speed range and high torque at low speed separately from normal operations, reducing overall transmission complexity while maintaining power extraction capability from the low pressure spool
Solution Approach 2:
The transmission system dynamically switches between two gear ratio states based on operating conditions. A clutch mechanism enables transition between the first gear ratio (for high torque at low speed) and the second gear ratio (for normal operations), allowing the system to adapt to varying speed and torque requirements without requiring a continuously variable transmission
2Ease of operation
If a multi-speed or variable-speed transmission is used to condition LS output speed, then accessory speed conditioning is improved, but transmission size increases due to high torque at minimum speed
Solution Approach 1:
The transmission uses a segmented approach with two fixed gear ratios instead of a continuous multi-speed transmission. The first gear ratio handles high torque at minimum speed, while the second gear ratio handles normal operations. This segmentation reduces the overall size and weight compared to a full multi-speed transmission while still providing adequate speed conditioning for accessories
Solution Approach 2:
The system extracts only the essential speed conditioning function needed for accessories by using a simple two-state mechanism with a clutch. Rather than implementing a complete multi-speed transmission, the invention extracts and implements only the specific gear ratio changes necessary to handle high torque at low speed and normal operations, reducing transmission size while maintaining functionality
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves a reduced speed range and torque, simplifying the transmission design, improving engine efficiency, and reducing brake wear, while allowing for more efficient power extraction and stable operation across various aircraft speed settings.
Implementation Method 1
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-spool speed range
Implementation Method 2
a clutch configured to selectively engage the transmission carrier and the transmission ring gear
Data Source
AI summary
A turbomachine dual spool transmission system can include a transmission assembly configured to connect to a combination output of a dual spool differential at a transmission input to be driven by the combination output to turn a transmission output. 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. 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.