Variable Fan Blade Mechanism Using Linear Actuators and Spider Ring
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Solution Overview
Problem
Existing aircraft gas turbine engines with variable pitch fan blades lack a lightweight, simple, and reliable mechanism to efficiently vary the pitch of fan blades across different flight conditions, impacting overall engine performance.
Innovation Solution
A variable pitch fan assembly featuring rotatable fan blades with a blade turning lever, non-rotatable linear actuators connected to a spider ring through thrust bearings, and spider arms that use a pin and slot joint mechanism to pivot the blades, allowing for axial displacement and optimal pitch adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a variable pitch fan blade system is implemented, then engine performance is improved by setting optimal blade angles for each flight condition, but the mechanism complexity increases
Solution Approach 1:
The mechanism is divided into discrete functional segments: linear actuators for axial movement, spider arms for radial transmission, and turning levers for pitch control. Each component performs a specific function, allowing the complex variable pitch system to be managed through modular, independently controllable units.
Solution Approach 2:
The spider arm acts as an intermediary mechanism that translates the simple axial linear motion from the actuator into the rotational pitch movement required by the fan blade. This intermediate conversion mechanism simplifies the overall control architecture while achieving the desired blade angle variation.
2Ease of manufacture
If a lightweight and simple variable pitch mechanism is used, then ease of manufacture and reliability improve, but the ability to achieve optimal pitch variation across all flight conditions may be compromised
Solution Approach 1:
The mechanism employs dynamic elements including the linear actuator that can vary its axial position, the spider arm that rotates about the drive shaft axis, and the turning lever that pivots about the pitch axis. This dynamic configuration allows continuous pitch adjustment across the full range of required flight conditions while maintaining a relatively simple mechanical structure.
Solution Approach 2:
The mechanism transforms motion from one dimension to another: the linear actuator moves axially (along the drive shaft axis), the spider arm translates this axial motion into radial/rotational motion, and the turning lever converts this into pitch angle variation. This dimensional transformation allows a simple linear actuator to control complex blade pitch behavior.
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
Enables efficient and reliable pitch variation of fan blades, enhancing engine performance by optimizing blade angle for various flight conditions while maintaining a lightweight and simple design.
Implementation Method 1
The actuator is connected to a spider ring through a thrust bearing for transmission of axial displacement of a non-rotatable actuator rod of the actuator when the fan blade is rotating
Data Source
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AI summary
A variable pitch fan assembly 38 includes variable pitch fan blades 60 circumscribed about engine centerline axis 12 coupled to a drive shaft 26 centered about the engine centerline axis 12. Each blade 60 pivotable about pitch axis (P) perpendicular to centerline axis 12 and having blade turning lever 210 connected thereto. One or more linear actuators 70 non rotatably mounted parallel to engine centerline axis 12 and operably linked to fan blades 60 for pivoting fan blades and connected to spider ring 214 through thrust bearings 80 for transmission of axial displacement of non-rotatable actuator rods 220 of actuators 70 while the fan blades 60 are rotating. Spider arms 216 extending away from spider ring 214 towards blade roots 204 and each spider arm 216 connected to one of the turning levers 210. Turning levers 210 may be connected and cammed to spider arms 216 by pin and slot joint 224. Each spider arm 216 may include joint pin 226 disposed through joint slot 228 of turning lever 210. Joint slot 228 may be angled or curved.