Geared Annular Airflow Actuation for Variable Cycle Engines
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Solution Overview
Problem
Variable cycle gas turbine engines require an effective actuation system to vary the bypass airflow cycle efficiently across different operating conditions, which is challenging due to the need for precise control of airflow paths and vanes to achieve high thrust and fuel efficiency.
Innovation Solution
An annular airflow control system with contra-rotatable variable vanes between an outer and inner ring, driven by a sync ring actuated by a gear system, allowing for precise control of airflow through the engine by rotating the sync ring and segment gears to adjust the position of the vanes between open, closed, and intermediate positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional actuation system is used to control bypass airflow, then the system can operate the engine at various cycle points, but the device complexity and actuator power requirements increase
Solution Approach 1:
The airflow control system is divided into multiple independent controllable elements including first and second variable area openings with respective actuators, and multiple contra-rotatable variable vanes. Each element can be controlled independently to achieve different cycle points, allowing complex airflow management through simpler modular components rather than a single complex actuation system
Solution Approach 2:
The patent employs contra-rotatable variable vanes that rotate in opposite directions to control airflow. This inverted approach where vanes rotate against each other creates balanced forces that reduce the net actuator power requirement while maintaining effective airflow control capability across multiple cycle points
2Productivity
If precise control of airflow paths and vanes is implemented, then thrust and fuel efficiency are optimized, but the actuator power requirements and system complexity increase
Solution Approach 1:
The contra-rotatable variable vanes are configured to rotate in opposite directions, creating counterbalancing forces that offset each other. This counterweight effect reduces the net actuator power required to achieve precise vane positioning, enabling optimized thrust and fuel efficiency without proportionally increasing energy consumption
Solution Approach 2:
The system employs multiple variable elements including variable area openings and contra-rotatable variable vanes that can dynamically adjust their positions. This dynamic configuration allows precise control of airflow paths to optimize thrust and fuel efficiency across different operating conditions while distributing the control effort across multiple simpler moving parts rather than requiring high power for single-point control
3Measurement precision
If multiple contra-rotatable variable vanes are used to control third stream airflow, then airflow control precision is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple control functions into a unified system where a single sync ring coordinates the rotation of multiple contra-rotatable variable vanes. This merging approach maintains precise airflow control by synchronizing multiple vanes while reducing overall system complexity compared to controlling each vane independently through separate actuation mechanisms
Solution Approach 2:
The gear system is segmented into multiple gear racks engaged with the sync ring, with each gear rack controlling specific vanes. This segmentation allows the complex task of controlling multiple vanes to be divided into simpler modular gear interactions, maintaining precision while managing complexity through distributed mechanical control
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 enables efficient control of airflow, enhancing engine operability and performance by minimizing actuator power requirements and optimizing thrust and fuel efficiency across various flight conditions.
Implementation Method 1
The first variable area opening is defined by a first gear rack and pinion assembly
Implementation Method 2
A third stream airflow path is defined radially outward from the second airflow path
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
An annular airflow control system for a gas turbine engine includes a sync ring rotatable to move the multiple of contra-rotatable variable vanes through a respective multiple of geared interfaces to throttle an airflow through the multiple of contra-rotatable variable vanes.