Segmented Shrouding for Multirotor Drag Reduction
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Solution Overview
Problem
Conventional multirotor aircraft thrust producing units experience significant drag and weight penalties in transversal air flow conditions due to their axial design, which decreases efficiency and increases power requirements during forward flight.
Innovation Solution
A thrust producing unit with a shrouding that accommodates at most one rotor assembly, featuring a cylindrical air duct with an undulated geometry, reducing overall height and drag, and allowing for variable design elements such as height, radius, and lifting surface arrangement to optimize performance in both hover and forward flight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a shrouding is provided around a rotor assembly to improve efficiency in axial air flow conditions, then thrust production efficiency is improved, but drag increases significantly in transversal air flow conditions
Solution Approach 1:
The shrouding is segmented into multiple sections along the rotor axis, with at least one section being movable relative to others. This segmentation allows the shrouding configuration to be adjusted between different operational states (hover/axial flight vs. forward/transversal flight), enabling the system to optimize efficiency in axial conditions while reducing drag in transversal conditions by reconfiguring the segmented sections.
Solution Approach 2:
The shrouding incorporates movable sections that can change position relative to each other along the rotor axis. This dynamic capability allows the shrouding to adapt its configuration based on flight conditions - maintaining an extended configuration for axial air flow efficiency while retracting or reconfiguring to reduce drag during transversal air flow conditions.
2Productivity
If a shrouding is provided around a rotor assembly to improve aerodynamics, then efficiency in axial air flow is improved, but weight increases
Solution Approach 1:
The shrouding is divided into multiple sections that can be independently positioned, allowing the structure to achieve aerodynamic efficiency only where necessary while minimizing overall material usage and weight through selective placement of shrouding sections.
Solution Approach 2:
The movable sections of the shrouding can change their position parameters along the rotor axis, allowing the system to optimize aerodynamic parameters (such as shrouding extent and positioning) based on operational conditions, thereby achieving high efficiency with reduced weight compared to a fixed, continuously extended shrouding.
3Productivity
If the shrouding height is increased to improve performance in axial air flow, then thrust efficiency increases, but drag in transversal air flow increases
Solution Approach 1:
The shrouding height is made dynamic through movable sections that can adjust their position along the rotor axis. This allows the effective shrouding height to be increased when operating in axial air flow conditions to maximize thrust efficiency, and reduced or reconfigured when operating in transversal air flow conditions to minimize drag.
Solution Approach 2:
By segmenting the shrouding into movable sections, the height can be selectively extended or retracted in different regions along the rotor axis, allowing optimization of thrust efficiency in axial conditions while reducing the projected area that contributes to drag in transversal conditions.
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 significantly reduces drag in transversal air flow conditions, lowers weight, and maintains efficiency in axial air flow conditions, while providing improved aerodynamics, reduced power consumption, and enhanced safety features like foreign object protection and reduced noise.
Implementation Method 1
the air inlet region exhibits in circumferential direction of the cylindrical air duct an undulated geometry
Data Source
AI summary
A thrust producing unit for producing thrust in a predetermined direction, comprising at least two rotor assemblies and a shrouding that accommodates at most one of the at least two rotor assemblies, wherein the shrouding defines a cylindrical air duct that is axially delimited by an air inlet region and an air outlet region, and wherein the air inlet region exhibits in circumferential direction of the cylindrical air duct an undulated geometry.