Variable Area Fan Nozzle with Elastomeric Seals
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Solution Overview
Problem
Bypass turbofan engines face challenges in reducing noise during high-thrust events like takeoff and maintaining engine performance due to lack of effective fan nozzle throat position control and air leakage issues in variable area fan nozzles.
Innovation Solution
The implementation of an array of elastically deformable or pivotable rigid petals attached to the thrust reverser sleeve, actuated by cables or composite materials, with elastomeric seals between petals to prevent air leakage and control fan nozzle exit area, allowing for adjustable throat area modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If movable flaps or petals are used to increase fan nozzle throat area during high-thrust events, then noise generated by exhaust is reduced, but fan flow leakage radially outward between petals degrades engine performance
Solution Approach 1:
The patent extracts the sealing function from the petal structure itself by introducing separate elastomeric seals positioned between adjacent petals. These seals are specifically designed to prevent radial leakage of fan flow while allowing the petals to maintain their noise-reducing variable area configuration. The seals are mounted on the pressure side of the petals and extend into the gaps between them, creating an effective barrier against flow leakage without interfering with the petal deflection mechanism.
Solution Approach 2:
The elastomeric seals act as intermediary elements between adjacent petals, filling the gaps that would otherwise allow fan flow to leak radially outward. These seals are made of elastomeric material that can deform to accommodate petal movement while maintaining sealing contact. The seals are positioned intermediate the petals and are biased to engage with both petals, creating a flexible barrier that prevents energy loss while allowing the variable geometry mechanism to function.
2Object-affected harmful factors
If petals are deflected outwardly to enlarge throat area, then exhaust velocity is reduced and noise decreases, but control of throat position becomes difficult leading to petal flutter
Solution Approach 1:
The patent incorporates a control system that monitors the position and state of the petals and adjusts the actuation forces accordingly. This feedback mechanism detects when petals are approaching unstable configurations and modifies the cable tension or actuator output to maintain stable positioning. The control system receives input from sensors that monitor petal deflection and provides real-time adjustments to prevent flutter conditions, ensuring stable operation across the full range of throat area configurations.
Solution Approach 2:
The patent employs cable actuation forces as a controllable parameter to maintain petal stability during deflection. By adjusting the tension in the cables that actuate the petals, the system can counteract aerodynamic forces that would otherwise cause flutter. The cable forces are modulated based on the desired throat area configuration, allowing stable positioning of petals at various deflected states while preventing unwanted oscillations during transitions between configurations.
3Device complexity
If fixed throat area fan nozzle is used, then engine structure is simpler, but noise during high-thrust events increases due to higher exhaust velocity
Solution Approach 1:
The patent divides the fan nozzle into multiple discrete petal segments that can be independently deflected to vary the throat area. Each petal is hinged to the thrust reverser sleeve and can be controlled by cable actuation, allowing the nozzle to transition from a fixed configuration to a variable geometry structure. This segmentation enables the nozzle to adapt its throat area to different operating conditions, reducing exhaust velocity and noise during high-thrust events while maintaining a relatively simple overall structure compared to fully movable nozzle systems.
Solution Approach 2:
The patent transforms the fixed fan nozzle into a dynamic structure with movable petals that can adjust the throat area in real-time. The petals are hinged to allow rotation and deflection, and are actuated by cables that can change the nozzle geometry during operation. This dynamic capability allows the engine to optimize exhaust flow velocity and reduce noise during high-thrust events like takeoff, while the petals can be biased or controlled to return to a neutral position for cruise conditions.
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 reduces noise during high-thrust events by adjusting the fan nozzle exit area and prevents air leakage, thereby enhancing engine performance and fuel efficiency.
Implementation Method 1
an array of elastically deformable or pivotable rigid petals attached to a lip area at a downstream end of a thrust reverser sleeve with an actuation system configured to deflect the petals inward or outward between outer and inner limit positions, wherein an elastomeric seal is provided between adjacent petals to prevent air leakage
Data Source
AI summary
An apparatus installed on an aircraft, comprising: a sleeve or duct having a trailing lip area; a plurality of petals arranged side by side with gaps therebetween, one end of each petal being attached or pivotably coupled to the lip area; and a plurality of elastomeric seals configured and disposed to close the gaps between adjacent petals. Each elastomeric seal comprises a first portion that moves with a portion of a first petal that is in contact therewith, a second portion that moves with a portion of a second petal that is in contact there, and a third portion which is stretched as the first and second petals move further apart from each other. Petal deflection is actuated by a system comprising a flexible member, a motor, a shaft driven by the motor, and an arm projecting from the shaft. One end of the flexible member is attached to the arm, the flexible member being movable to deflect the petals inward in response to a shaft rotation. Said apparatus comprising a core nacelle having a core nozzle at one end, wherein said sleeve is a thrust reverser sleeve that surrounds a portion of said core nacelle.