Aircraft Lift Enhancement With Behind-Below-Wing Rotors
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Solution Overview
Problem
The complex aerodynamic interactions between rotors and wings in eVTOL aircraft negatively influence system performance during hover and low-speed flight, leading to reduced wing lift and increased drag.
Innovation Solution
An aircraft lift enhancement system with rotors positioned behind and below the wing, generating suction over the upper surface to increase lift and counter drag, while maintaining a specific distance and orientation relative to the airfoil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If rotors are mounted on or above the wings for lift enhancement, then wing lift may be increased, but rotor downwash induces flow separation and reduces wing lift
Solution Approach 1:
The rotor is repositioned from a conventional location (on or above the wing) to a novel location (behind and below the wing). This spatial reconfiguration changes the dimension of rotor-wing interaction, allowing the rotor downwash to act on the wing's trailing edge region rather than directly over the upper surface, thereby avoiding flow separation while maintaining lift enhancement benefits
2Force
If rotors are positioned close to the wing for aerodynamic interaction, then lift enhancement is achieved, but rotor-wing aerodynamic interaction degrades wing lift
Solution Approach 1:
The airfoil trailing edge acts as an intermediary element between the rotor and the wing upper surface. The rotor is positioned behind and below the wing, and its induced flow interacts with the trailing edge region, which then influences the upper surface flow field. This intermediary positioning allows beneficial interaction without the direct harmful interaction that occurs when rotors are mounted on or above the wing
3Force
If multiple rotors are used for lift supplementation, then overall lift is increased, but complex aerodynamic interactions reduce system performance
Solution Approach 1:
Multiple rotors are positioned at specific locations behind and below the wing, with each rotor targeting a specific region of the wing's trailing edge. This localized positioning allows each rotor to interact with a specific portion of the wing, reducing complex interactions between rotors while maintaining overall lift enhancement. The rotors are spaced to avoid excessive interference with each other
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 system enhances wing lift by up to 134% and increases the lift-to-drag ratio by up to 49% through rotor-induced suction, despite minor thrust and torque penalties.
Implementation Method 1
The aircraft lift enhancement system includes an airfoil and at least one rotor positioned behind and below the airfoil... generating suction over the upper surface to increase lift and counter drag
Data Source
AI summary
An aircraft lift enhancement system is provided. The aircraft lift enhancement system includes an airfoil and at least one rotor. The airfoil includes a leading edge and a trailing edge defining a longitudinal axis of the airfoil, and a proximal end and a distal end defining a length of the airfoil. The at least one rotor is positioned a first distance substantially behind the trailing edge of the airfoil as measured along the longitudinal axis and a second distance substantially vertically below a lower surface of the airfoil. The at least one rotor includes a hub and a plurality of aerodynamic blades extending outwards from the hub a radial distance R and configured to rotate in a substantially horizontal plane around a center point of the rotor.