Variable Pitch Fan Blade Centrifugal Torque Offset
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Variable pitch fans face significant loading due to centrifugal pitching torque, which increases the overall weight when counterweights are used to mitigate this issue, necessitating a solution that reduces torque without increasing the fan's weight.
Innovation Solution
The fan blade is offset from its pitching axis, acting as its own counterweight to reduce or eliminate centrifugal pitching torque, potentially used in conjunction with counterweights to minimize their size and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If counterweights are used to reduce centrifugal pitching torque, then the pitching torque is reduced, but the overall weight of the fan increases
Solution Approach 1:
The patent merges the counterweight function with the blade structure itself by integrating a counterbalancing element into the blade. This eliminates the need for separate counterweight components, thereby reducing the overall fan weight while still achieving torque reduction through the integrated mass distribution
Solution Approach 2:
The patent applies asymmetry by distributing mass non-uniformly within the blade structure, creating an intentional imbalance in one direction to counteract the centrifugal pitching torque. The counterbalancing element is positioned to create an opposing moment arm, achieving torque reduction through asymmetric mass placement rather than symmetric counterweights
2Force
If the blade mass is increased to create counterbalancing torque, then the pitching torque is reduced, but the fan drive mechanism becomes overloaded
Solution Approach 1:
The patent addresses the torque balance problem by moving from a one-dimensional approach (adding mass along the blade span) to a two-dimensional approach (positioning mass perpendicular to the chord line at a specific offset distance). This dimensional shift allows torque reduction through strategic mass placement rather than simply increasing total blade mass
Solution Approach 2:
The patent implements a counterweight mechanism by positioning a counterbalancing element at a specific offset from the pitch axis, creating a moment that opposes the centrifugal pitching torque. The counterbalancing element functions as an anti-weight system where the product of its mass and offset distance equals the required counterbalancing moment
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
This approach reduces the pitching torque by up to 30% while maintaining a lightweight fan design, making it suitable for applications where a lightweight fan is crucial.
Implementation Method 1
A pitching torque is created by a spinning a fan blade/propeller due to centrifugal effects
Implementation Method 2
This torque varies with the mass, the shape of the blade the square of the rpm, and the pitch of the blades
Data Source
AI summary
A fan blade is mounted on a shaft or arranged to vary in pitch via rotation about a pitching axis. The fan blade is mounted with a center of mass offset from the shaft or pitching axis. This offset reduces torque around the shaft or pitching axis.