Variable Area Fan Nozzle Axial Translation and Radial Tilting
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Solution Overview
Problem
Existing gas turbine aircraft engine designs face inefficiencies and noise issues due to fixed fan nozzles, complex and heavy actuation systems, and interference challenges with thrust reversers, particularly in varying flight conditions.
Innovation Solution
A Variable Area Fan Nozzle (VAFN) design that translates and tilts about shifting axes, using a short actuator stroke, anchored to the nacelle structure, with integrated actuators and position sensors, allowing for reduced fairing size and weight, and customizable trackway profiles to optimize nozzle area and clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed fan nozzle is used, then the engine is simple and reliable, but the engine efficiency and noise performance deteriorate under varying flight conditions
Solution Approach 1:
The patent applies dynamics by making the fan nozzle variable in area through axial translation and radial tilting of nozzle segments. The nozzle transitions from a fixed structure to a dynamic one that can adjust its geometry to optimize performance under different flight conditions, directly resolving the contradiction between adaptability and complexity.
Solution Approach 2:
The fan nozzle is divided into multiple movable segments that can independently translate axially and tilt radially. This segmentation allows each segment to be controlled separately, providing fine-grained adaptability while maintaining manageable system complexity through modular design.
2Productivity
If a translating VAFN structure is added aft of the T/R sleeve, then the engine efficiency improves, but the device complexity and interference challenges increase
Solution Approach 1:
The patent merges the actuation of the T/R sleeve and the VAFN segments into a single integrated actuator system. This combined actuation mechanism reduces the number of separate actuation systems needed, thereby improving fuel efficiency through VAFN operation while minimizing the increase in device complexity.
Solution Approach 2:
The actuator system is designed to perform multiple functions: it can actuate both the T/R sleeve and the VAFN segments, and it provides both axial translation and radial tilting capabilities. This multi-functionality reduces the overall complexity by eliminating the need for separate actuators for each function.
3Reliability
If multiple components are used to transmit motive force to the T/R sleeve and VAFN, then the actuation is reliable, but the weight and complexity increase
Solution Approach 1:
The patent combines multiple force transmission components into an integrated actuator assembly that directly couples the motive force to both the T/R sleeve and VAFN segments. This merging reduces the total number of components and their associated weights while maintaining reliable actuation through direct mechanical coupling.
4Measurement precision
If a dedicated position sensing system is installed, then the nozzle position is accurately sensed, but the weight penalty increases
Solution Approach 1:
The patent integrates the position sensing function directly into the actuator system itself, rather than installing a separate dedicated sensing system. The actuator's mechanical structure serves dual purposes: actuation and position sensing, thereby achieving accurate position measurement without the weight penalty of additional sensing components.
Solution Approach 2:
The actuator system provides its own position sensing capability through its mechanical design, eliminating the need for external sensing systems. The actuator's internal mechanics directly provide position information, allowing the system to sense its own state without additional weight.
Data Source
AI summary
An aircraft engine variable area fan nozzle structure disposed abaft a thrust reverser, including a sleeve translatable over a cascade array, comprises two semi cylindrical segments that can be axially translated and radially tilted to enlarge the fan duct exhaust area in order to optimize exhaust pressure and associated noise in high thrust circumstances such as on take-off, and to constrict that area under lower thrust conditions such as cruise. The segments are moved by actuators anchored to the fixed engine framework and independently of the thrust reverser translating sleeve. Each actuator incorporates a linear variable differential transformer acting as a fan nozzle position sensor. The tilting movement is imposed by the pivoting links of each segment to carriages that ride in a non-linear trackway secured to a thrust reverser translating sleeve slider. In an alternate embodiment of the invention, the thrust reverser sleeve actuator and the variable area fan nozzle actuator are coaxially mounted in a compact assembly anchored to stationary components of the nacelle.