Variable-Pitch Fan Module With Flyweight Feathering Control
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Solution Overview
Problem
Existing systems for changing the pitch of blades in turbomachines require bulky and heavy mechanisms, impose high actuation forces, and suffer from mechanical stress and fluid leakage issues, particularly in the case of axial movement and lever counterweight mechanisms.
Innovation Solution
A fan module with variable-pitch blades featuring a control device with an annular actuator and a connection mechanism, coupled with a feathering device using an annular row of fly-weights connected by ball-and-socket joints, allowing translational and rotational movement without external torque provision, reducing mass and bulk, and eliminating fluid leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional lever counterweight mechanisms are used for blade feathering, then blade pitch control is achieved, but the system becomes bulky and heavy with high mechanical stress
Solution Approach 1:
The patent replaces the traditional lever counterweight mechanism with a direct ball-and-socket joint connection between the synchronizing ring gear and flyweights. This substitution eliminates the intermediate lever mechanism, reducing the number of moving parts, decreasing mass, and lowering mechanical stress while maintaining the blade feathering function through direct force transmission from centrifugal force to the ring gear.
Solution Approach 2:
The patent extracts and removes the lever mechanism from the feathering system, retaining only the essential elements (flyweights and ball-and-socket joints) needed for blade pitch control. This extraction simplifies the overall structure, reduces complexity, and eliminates unnecessary components that contributed to the bulk and weight of traditional systems.
2Adaptability or versatility
If axial movement mechanisms are used for pitch change, then blade pitch variation is achieved, but fluid leakage and mechanical stress increase
Solution Approach 1:
The patent replaces axial movement mechanisms with a rotational mechanism based on ball-and-socket joints that convert centrifugal force directly into pitch variation. This substitution eliminates the need for fluid-filled axial actuators, thereby eliminating fluid leakage while maintaining adaptability in blade pitch control through the rotational degrees of freedom provided by the spherical joints.
3Reliability
If traditional connection mechanisms are used between actuator and blades, then pitch control is achieved, but the system requires high actuation forces
Solution Approach 1:
The patent uses flyweights that generate centrifugal force during rotation to automatically counterbalance and drive the blade pitch variation. This counterweight mechanism converts the rotational kinetic energy of the flyweights directly into the force needed for pitch control, eliminating the need for high actuation forces from external actuators while maintaining reliable pitch control throughout the operational range.
Solution Approach 2:
The feathering system becomes self-actuating through the flyweights that automatically generate the necessary centrifugal force during rotor rotation. The system serves itself by converting its own rotational motion into the pitch control force, eliminating the need for external high-force actuators and reducing the overall force requirements for pitch variation.
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 efficient passive feathering with reduced mass and mechanical stress, enabling a lighter and less bulky pitch change system with improved kinematics and no fluid leakage, while maintaining effective blade control.
Implementation Method 1
each of the fly-weights being connected to the synchronizing ring gear by a connecting rod, a first and a second end of which comprise ball-and-socket joints
Implementation Method 2
the fly-weights being configured, under the centrifugal effect, to move into a position in which the synchronizing ring gear imposes a feathered position on the blades
Data Source
AI summary
A fan module having variable-pitch blades is configured for use with for a propulsion unit having a longitudinal axis. The fan module includes a rotary casing carrying the blades and a pitch-changing system. The pitch-changing system includes a control device that includes an annular actuator having a stationary body added onto the rotary casing and a body configured to translate with respect to the stationary body along the longitudinal axis. A linking mechanism includes a synchronizing ring coupled to the mobile body, connected to the blades and configured to be translated along the longitudinal axis by the mobile body so as to change the pitch of the blades. A feathering device includes fly-weights coupled to the ring by a connecting rod of which the ends include ball-and-socket joints.