Fan Drive Gear Control for Variable Turbofan Speed Ratio
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Solution Overview
Problem
Current geared architectures in gas turbine engines have limitations in achieving optimal thermal, transfer, and propulsive efficiencies, as they rely on fixed speed reduction ratios and static structures, which do not allow for dynamic adjustments to fan section speeds based on varying operating conditions.
Innovation Solution
A gear controller system that allows the controlled portion of the geared architecture to rotate between a static and a free condition, enabling a variable speed reduction ratio by using impellers or electric/hydraulic devices to generate resistance forces, thereby adjusting the speed of the fan section relative to the input shaft, allowing for increased flexibility and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a fixed speed reduction ratio is used in the geared architecture, then torque transfer efficiency is improved, but adaptability to varying operating conditions deteriorates
Solution Approach 1:
The patent applies the dynamics principle by enabling the geared architecture to transition between static and rotating states. The controlled portion can rotate relative to the static structure, allowing the speed reduction ratio to vary dynamically based on operating conditions. This resolves the contradiction by maintaining fixed ratio efficiency when needed while enabling adaptability when operating conditions change.
2Loss of energy
If the geared architecture is grounded to a static structure, then torque transfer efficiency is improved, but flexibility in speed adjustment deteriorates
Solution Approach 1:
The patent segments the geared architecture into a static structure portion and a controlled portion that can rotate independently. This segmentation allows the static structure to maintain torque transfer efficiency while the controlled portion provides flexibility for speed adjustment by rotating relative to the static structure.
3Adaptability or versatility
If a variable speed reduction ratio is implemented, then adaptability to operating conditions is improved, but device complexity increases
Solution Approach 1:
The patent introduces a gear controller as an intermediary device that manages the rotation of the controlled portion. This intermediary component enables variable speed reduction ratio and adaptability while keeping the overall system complexity manageable through a dedicated control mechanism rather than complexing the entire geared architecture.
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
This solution enhances the propulsive efficiency of the turbofan engine by allowing the fan section to operate at speeds tailored to specific conditions, improving overall engine performance by dynamically adjusting the speed reduction ratio and maintaining efficient torque transfer.
Implementation Method 1
the gear controller includes impellors extending into a flow path for generating a resistance force for controlling rotation of the controlled portion of the geared architecture
Implementation Method 2
the gear controller includes an electric device generating a resistance force for controlling rotation of the controlled portion of the geared architecture
Implementation Method 3
the gear controller includes a hydraulic device for generating a resistance force for controlling rotation of the geared architecture
Data Source
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AI summary
A fan drive gear system for a turbofan engine includes a geared architecture and a gear controller supporting the geared architecture and controlling rotation of the geared architecture relative a static structure.