Variable Geometry Lift Fan Mechanism for Drag Reduction
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Solution Overview
Problem
Powered-lift aircraft lift fans experience significant aerodynamic drag due to flow separation and large frontal area when fan blades are stationary, reducing aircraft performance, and existing solutions cannot efficiently transition multiple-bladed fans to a configuration that minimizes drag during forward flight.
Innovation Solution
A variable geometry lift fan mechanism that transitions between a deployed and collapsed configuration using the motor that drives the fan, with mechanical stops, friction, and detents to control blade positioning, allowing blades to align in-line for reduced drag and easier storage, without requiring additional motors or actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If fan blades are stationary with large chords and high twist for vertical thrust, then lift capability is improved, but aerodynamic drag increases due to flow separation and large frontal area
Solution Approach 1:
The fan blade configuration is made dynamic by enabling rotation of individual blades relative to the fan hub. This allows the blade geometry to change from a stationary high-lift configuration to a rotated low-drag configuration, resolving the contradiction between lift capability and aerodynamic drag through temporal separation of functions
Solution Approach 2:
The effective parameters of the fan blades (frontal area, chord orientation, twist angle) are changed by rotating the blades to different angular positions. This parameter change transforms the blade configuration from one optimized for vertical thrust to one optimized for minimal aerodynamic drag during forward flight
2Object-generated harmful factors
If individual fan blades are aligned with flow direction to reduce drag, then aerodynamic performance is improved, but this configuration is not achievable with fans of more than two blades
Solution Approach 1:
The fan blade system is segmented into independently rotatable individual blades rather than a rigid multi-blade assembly. This segmentation allows each blade to be independently positioned at optimal angles, enabling four or more blades to achieve drag-reduced configurations that would be impossible with fixed symmetric blade arrangements
Solution Approach 2:
The blade system transitions from a static fixed-geometry configuration to a dynamic variable-geometry configuration where each blade can independently adjust its angular position. This dynamic capability provides the adaptability needed to achieve optimal drag reduction while maintaining the multi-blade structure necessary for vertical thrust
3Ease of operation
If additional motors or actuators are added to transition fan blades between configurations, then blade positioning control is improved, but device complexity increases
Solution Approach 1:
The primary motor that drives the lift fan for vertical thrust is made multi-functional by enabling it to also control the relative rotation of individual blades. This universal application of the existing motor eliminates the need for separate actuators, reducing device complexity while maintaining precise blade positioning control
Solution Approach 2:
The lift fan motor serves itself by performing dual functions: generating the rotational force for vertical thrust and simultaneously controlling the angular positioning of individual blades. This self-service approach eliminates the need for additional control systems and reduces overall system complexity
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 mechanism significantly reduces aerodynamic drag and overall width of the aircraft, enhancing performance and transportability by aligning fan blades during forward flight and storing them compactly when not in use.
Implementation Method 1
the torque of the electric motor can be precisely controlled and used to move the lift fan blades between the deployed and collapsed configurations
Implementation Method 2
Friction and damping between the blades may be employed to affect the dynamics of the deploying and collapsing action and/or to resist rotation of the blades out of either the collapsed configuration or deployed configuration
Implementation Method 3
Friction and damping between the blades may be employed to affect the dynamics of the deploying and collapsing action
Data Source
AI summary
A vertical takeoff and landing aircraft includes rotors that provide vertical and horizontal thrust. During forward motion, the vertical lift system is inactive. A lift fan mechanism positions the fan blades of the aircraft in a collapsed configuration when the vertical lift system is inactive and positions the fan blades of the aircraft in a deployed configuration when the vertical lift system is active.