Variable Area Fan Nozzle Wall Structure for Flutter Resistance
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Solution Overview
Problem
Gas turbine engines face issues with flutter-induced vibrations in the variable area fan nozzle, leading to potential damage and reduced durability due to aerodynamic forces and natural vibration modes.
Innovation Solution
A variable area fan nozzle with a strategically designed wall thickness distribution and mechanical property distribution, utilizing fiber-reinforced composite materials and varying curing conditions to minimize flutter by altering stiffness and vibration characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the fan nozzle wall is made thin to reduce weight, then the weight of the moving object is reduced, but the nozzle becomes more susceptible to flutter-induced vibrations and potential damage
Solution Approach 1:
The patent applies local quality by varying the wall thickness distribution across different sections of the fan nozzle. The wall thickness is strategically increased in regions prone to flutter and vibration while maintaining thinner sections where structural demands are lower. This non-uniform thickness distribution optimizes the balance between weight reduction and flutter resistance, allowing the nozzle to be lighter overall while maintaining durability in critical areas.
Solution Approach 2:
The patent utilizes composite materials with fiber reinforcement to achieve high strength-to-weight ratio. The composite structure provides enhanced stiffness and vibration resistance compared to conventional materials, allowing the nozzle to maintain durability with reduced weight. The composite material properties are optimized to suppress flutter-induced vibrations while minimizing the overall mass of the moving component.
2Reliability
If the wall thickness is increased to reduce flutter, then the reliability is improved, but the weight of the moving object increases
Solution Approach 1:
Rather than uniformly increasing wall thickness throughout the entire nozzle, the patent applies local quality by concentrating thicker sections only in areas where flutter is most problematic. This targeted approach increases reliability where needed while avoiding unnecessary weight addition in regions where the thinner wall is sufficient, thus resolving the contradiction between durability and weight.
3Reliability
If the mechanical property distribution is optimized to minimize flutter, then the reliability is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent implements local quality through spatially varying mechanical properties in the nozzle wall, such as varying fiber orientation, material composition, or wall thickness. This creates non-uniform mechanical properties that specifically address flutter-prone regions. While this increases manufacturing complexity compared to uniform structures, the targeted approach provides significant durability benefits that justify the added complexity.
Solution Approach 2:
The patent optimizes mechanical property distribution by varying key parameters such as wall thickness, material composition, or fiber reinforcement patterns across different sections of the nozzle. These parameter changes are designed to suppress flutter vibrations while maintaining manufacturability through controlled variations rather than overly complex structures.
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 solution effectively reduces flutter and enhances the durability of the nozzle and engine by minimizing stress and preventing contact with the fan nacelle, thereby improving operational reliability.
Implementation Method 1
a computer-simulated vibration profile of a flutter characteristic of the VAFN
Implementation Method 2
flutter-induced vibrations in the variable area fan nozzle
Implementation Method 3
a cured polymeric material and a variation in curing of the cured polymeric material defines the mechanical property distribution
Data Source
Figure 1~2
Figure 3~4
Figure 5~8B
AI summary
A gas turbine engine, comprising a core engine (CE) including at least a compressor section (24), a combustor section (26) and a turbine section (46, 54) disposed along a central axis; a fan (42) coupled to be driven by the turbine section; a fan nacelle (58) around the fan, and a bypass passage extending between the fan nacelle and the core engine; and a variable area fan nozzle (VAFN) (62) extending at least partially around the central axis and defining an exit area (64) of the bypass passage, the VAFN being selectively movable to vary the exit area, the VAFN including a body defining an airfoil cross-section shape, the VAFN including a wall (72, 74) having a mechanical property distribution, or a wall stiffness distribution, or a wall thickness in accordance with a computer-simulated vibration profile of a flutter characteristic of the VAFN; wherein the wall includes a fiber-reinforced composite and a configuration of the fibers defines the mechanical property distribution.