Variable Area Fan Nozzle Control Using String Potentiometer Feedback
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Solution Overview
Problem
Variable area fan nozzles face challenges in precisely controlling nozzle areas due to poor actuator feedback and interference from other factors, leading to inefficiencies and stability issues in turbofan engines, especially during different operating regimes.
Innovation Solution
A control system for variable area fan nozzles that uses a cable connected to a linear displacement measuring device, such as a string potentiometer, to measure changes in nozzle circumference and adjust petal positions, combining inputs from sensors like linear variable differential transducers and thermocouples to accurately estimate and control nozzle area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a cable-actuated system with traditional feedback is used to control petal positions, then the nozzle area can be adjusted, but the control precision is insufficient due to poor actuator feedback
Solution Approach 1:
The patent implements a feedback mechanism where a linear displacement measuring device (string potentiometer) measures the actual position of the cable, and this measurement is fed back to the control system. The control system compares the measured position with the desired position and generates corrective actuator commands to minimize the error, thereby improving control precision and reliability
Solution Approach 2:
The patent replaces traditional mechanical feedback mechanisms with an electrical measurement system. Instead of relying on mechanical linkages or visual inspection to determine petal position, the system uses a string potentiometer to convert mechanical displacement into an electrical signal that can be precisely measured and processed by the control system
2Measurement precision
If photogrammetry systems are used to measure nozzle circumference, then measurement accuracy can be achieved, but the system complexity and maintainability deteriorate
Solution Approach 1:
The patent extracts the essential measurement function from the complex photogrammetry system and implements it through a simple linear displacement measuring device attached to a cable. Instead of using multiple cameras and complex image processing, the system directly measures cable displacement which correlates to nozzle circumference changes, achieving the same measurement goal with much simpler hardware and processing requirements
Solution Approach 2:
The patent employs a cost-effective string potentiometer instead of expensive photogrammetry equipment. While the string potentiometer may have limited lifespan compared to optical systems, it provides adequate measurement precision for the application at a fraction of the cost and with significantly reduced system complexity, making it suitable for environments where extreme long-term durability is not the primary constraint
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 provides precise and accurate control of nozzle areas, improving thermodynamic and aerodynamic efficiencies, reducing fuel consumption, and addressing fan stability issues, while being simpler and more maintainable than photogrammetry systems.
Implementation Method 1
A linear displacement measuring device measures changes in a length of the reference portion of the cable
Implementation Method 2
combining inputs from sensors like linear variable differential transducers and thermocouples to accurately estimate and control nozzle area
Data Source
Figure 1
Figure 2A~2B
Figure 2C
AI summary
Provided are methods and systems for measuring and controlling nozzle areas of variable area fan nozzles. A control system attached to a nozzle includes a cable having one end connected to a linear displacement measuring device, such as a string potentiometer. The other end of the cable is connected to a petal. A reference portion of the cable extends across multiple petals of the nozzle and substantially parallel to the nozzle circumference. The linear displacement measuring device measures any changes in the length of this reference portion as the petals actuate outwardly or inwardly during operation of the nozzle. The output of the linear displacement measuring device may be used to control actuators that move the petals. In some embodiments, potentiometer's output may be combined with one or more outputs from other sensors, such as a linear variable differential transducer and/or thermocouple.