Actuation System for Variable Area Fan Nozzle
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Solution Overview
Problem
Existing variable area nozzle systems for turbofan aircraft engines are heavy, expensive, and complex, requiring coordinated movement of multiple components with complex drive mechanisms, making them inefficient for cost-effective control of engine output under varying flight conditions.
Innovation Solution
A variable area fan nozzle assembly with a translating thrust reverser sleeve and fan nozzle, utilizing a power drive unit, extensible actuators, and telescoping couplings to efficiently move the nozzle between stowed and deployed positions, allowing for adjustment of bypass flow characteristics to optimize engine performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If prior variable area nozzle systems are used to adjust fan nozzle exit area, then engine performance can be optimized under various flight conditions, but the system becomes heavy, expensive and complex with multiple components and complex drive mechanisms
Solution Approach 1:
The patent combines the thrust reverser sleeve and fan nozzle into a single integrated translating assembly. The thrust reverser sleeve and fan nozzle move together as one unit along the translation axis, eliminating the need for separate drive mechanisms for each component. This merging reduces the overall number of parts and simplifies the drive system while maintaining the ability to adjust the effective nozzle exit area for performance optimization.
Solution Approach 2:
The single translating assembly serves multiple functions: it acts as both the thrust reverser sleeve and the fan nozzle, and it performs both thrust reversal and variable area adjustment. By making the thrust reverser sleeve and fan nozzle move together, the system achieves multi-functionality with a single actuation system, reducing complexity while maintaining adaptability for different flight conditions.
2Adaptability or versatility
If prior variable area nozzle systems with multiple components are used, then nozzle exit area can be varied, but the system requires coordinated movement of multiple components which increases cost and complexity
Solution Approach 1:
The patent merges the thrust reverser sleeve and fan nozzle into a single translating assembly that moves together. This consolidation reduces the number of parts that need to be manufactured and assembled, lowering production costs. The single assembly approach eliminates the need for complex coordination mechanisms between multiple components, simplifying both manufacturing and maintenance.
3Productivity
If fan pressure ratio is reduced to improve propulsive efficiency, then exhaust velocity decreases and efficiency increases, but engine fan stall, blade flutter or compressor surge may occur
Solution Approach 1:
The patent implements a dynamic variable area nozzle system that can adjust the effective exit area in real-time based on operating conditions. By translating the integrated thrust reverser sleeve and fan nozzle assembly along the translation axis, the system dynamically modifies the nozzle geometry to maintain optimal flow characteristics across different flight conditions, preventing stall, flutter, and surge while preserving propulsive efficiency.
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 provides a cost-effective and simple actuation system that efficiently adjusts the fan nozzle exit area, increasing stall margins and avoiding engine malfunctions by bleeding excess fan flow, thereby enhancing engine performance and reliability under different flight conditions.
Implementation Method 1
Rotation of the telescoping coupling at a first rotational speed causes rotation of the jack screw at a second rotational speed that is different from the first rotational speed
Implementation Method 2
The extensible actuator includes a jack screw and a threaded sleeve that is threadably engaged with the jack screw
Data Source
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Figure 5
AI summary
A variable area fan nozzle assembly for a turbofan engine includes a nacelle having an aft edge and a translating thrust reverser sleeve with a trailing edge. The thrust reverser sleeve is movably disposed aft of the nacelle's aft edge and is movable between a forward position and an aft position. A translating fan nozzle having a forward edge is movably disposed behind the trailing edge, and is movable between a stowed position and a deployed position. An upstream bypass flow exit is defined between the trailing edge and the forward edge when the fan nozzle is in the deployed position. An extendable actuation system is configured to move the fan nozzle between the stowed position and the deployed position.