Variable Area Fan Nozzle Dynamic Bypass Adjustment
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Solution Overview
Problem
Turbofan aircraft engines face challenges in varying the bypass duct exit area to match different flight conditions and thrust levels, as existing designs lack efficient mechanisms to adjust fan nozzle exit areas dynamically.
Innovation Solution
A variable area fan nozzle system is introduced, comprising a movable aft structure and a radially-outer and radially-inner sealing elements, allowing the porting flow passage to open or close, thereby adjusting the exit area of the bypass duct by translating the aft structure between stowed and deployed positions, and using sealing elements to maintain a sealed interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable area fan nozzle system is introduced to dynamically adjust the bypass duct exit area, then thrust management and engine performance are improved, but device complexity increases
Solution Approach 1:
The nozzle system is segmented into modular components: a movable aft structure, fixed forward structure, radially-outer sealing element, and radially-inner sealing element. This segmentation allows independent design and optimization of each component while maintaining overall system functionality for variable area adjustment.
Solution Approach 2:
The radially-inner sealing element is nested within the radially-outer sealing element, with the inner sealing element positioned inside the bypass duct and the outer sealing element positioned outside. This nested arrangement provides dual sealing capability in a compact configuration, managing complexity through spatial efficiency.
2Reliability
If sealing elements are added to maintain sealed interface during movement, then reliability is improved, but device complexity increases
Solution Approach 1:
Each sealing element (radially-outer and radially-inner) is designed to perform multiple functions: providing sealed interfaces between the movable aft structure and fixed forward structure, accommodating relative movement between components, and maintaining sealing during both stowed and deployed positions. This multi-functionality reduces the need for additional specialized components.
Solution Approach 2:
The sealing elements are positioned and configured to automatically maintain sealed interfaces through their geometric arrangement and material properties, without requiring active control systems or additional actuation mechanisms. The sealing action occurs passively as the structures move relative to each other.
Data Source
AI summary
A variable area fan nozzle for a turbofan aircraft engine includes a first structure defining a forward portion of a bypass duct of the turbofan aircraft engine and a second structure defining an aft portion of the bypass duct. The second structure is movable relative to the first structure between a deployed position where a porting flow passage defined between the forward portion of the bypass duct and the aft portion of the bypass duct is open, and a stowed portion where the porting flow passage is closed. The movable second structure comprises a vane and a slat attached to the vane and disposed forward of the vane. The porting flow passage extends between the slat and the vane when the second structure is in the deployed position.