Concentric Multi-Rotor System for VTOL Thrust Efficiency

Solution Overview

Problem

Conventional rotor systems for providing thrust in air environments suffer from inefficiencies due to mechanical friction, fluidic turbulences, and noise generation, particularly because the tangential speed of rotor blades approaches the speed of sound, leading to reduced aerodynamic lift and increased drag, resulting in lower thrust efficiency and higher noise levels.

Innovation Solution

A multi-rotor system comprising at least two concentric rotors rotating about a common axis, with the outer radius of one rotor being similar to the inner radius of the other, allowing independent rotational speeds and optimized angular speeds to maintain blade tips at a maximal practical tangential speed of 0.2 Mach or less, thereby reducing noise and improving thrust efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If rotor blade tip speed is increased to provide sufficient thrust, then thrust power increases, but noise increases and aerodynamic efficiency decreases

Engineering Contradiction:

Improvethrust powerVSAvoidnoise

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The rotor system is divided into multiple concentric rotors (first rotor, second rotor, third rotor) with different radii, allowing each rotor to operate at optimized speeds. This segmentation enables the system to achieve sufficient thrust while keeping individual blade tip speeds below the speed of sound, thereby reducing noise and maintaining aerodynamic efficiency.

Inventive Principle:

Principle #1Segmentation

2Power

If rotor blade tip speed is increased to provide sufficient thrust, then thrust power increases, but aerodynamic lift decreases and drag increases

Engineering Contradiction:

Improvethrust powerVSAvoidaerodynamic efficiency

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The rotor system is divided into multiple concentric rotors (first rotor, second rotor, third rotor) with different radii, allowing each rotor to operate at optimized speeds. This segmentation enables the system to achieve sufficient thrust while keeping individual blade tip speeds below the speed of sound, thereby reducing noise and maintaining aerodynamic efficiency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different rotors are designed with different radii and rotational speeds tailored to their specific locations. The first rotor has a larger radius and lower speed, while the third rotor has a smaller radius and higher speed, optimizing the aerodynamic performance of each local region to maximize lift while minimizing drag.

Inventive Principle:

Principle #3Local quality

3Power

If single large rotor is used to provide thrust, then thrust power increases, but moment of inertia increases reducing maneuverability

Engineering Contradiction:

Improvethrust powerVSAvoidmoment of inertia

Core Design Contradiction:

PowerVSWeight of moving object

Solution Approach 1:

The rotor system is divided into multiple concentric rotors (first rotor, second rotor, third rotor) with different radii, allowing each rotor to operate at optimized speeds. This segmentation enables the system to achieve sufficient thrust while keeping individual blade tip speeds below the speed of sound, thereby reducing noise and maintaining aerodynamic efficiency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of using a single large rotor, the system distributes the thrust-generating function across multiple rotors arranged concentrically with different radii. This dimensional redistribution reduces the moment of inertia while maintaining total thrust capability, thereby improving maneuverability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 multi-rotor system enhances thrust efficiency by optimizing the utilization of rotor area, reducing noise through laminar flow management, and providing improved maneuverability and mobility with lower inertia, while maintaining or exceeding the thrust and efficiency of single-rotor systems.

Implementation Method 1

The aerodynamic efficiency of rotating blades decreases as their linear (=tangential) speed decreases or as their linear speed approaches the speed of sound due to the abrupt change in the density of the air

Methodology Applied

Scientific EffectAerodynamic lift: Aerofoil

Implementation Method 2

the aerodynamic lift of the blade at such points reduces until, at points along circle 106, the lift of the blade there is smaller than the aerodynamic drag produced at that point

Methodology Applied

Scientific EffectAerodynamic drag: Drag

Implementation Method 3

reducing noise through laminar flow management

Methodology Applied

Scientific EffectLaminar flow: Laminar Flow

Implementation Method 4

fluidic turbulences resulting non-consumable energy loss

Methodology Applied

Scientific EffectTurbulence: Turbulence

Data Source

PatentUS20240158073A1System, assemblies and methods for mechanical-thrust power conversion multifans

Publication Date: 2024.05.16 N M B MEDICAL APPL

AI summary

A multi-rotor system for providing air thrust is disclosed comprising at least one multi-rotor assembly. The multi-rotor assembly comprising at least two rotors rotatable about a common axis wherein the outer radius of a first rotor is substantially similar to the inner radius of the second rotor. An airborne vehicle is also disclosed that is adapted to perform vertical takeoff and landing (VTOL). The airborne vehicle comprising at least two multi-rotor system disposed substantially symmetrically around the center of gravity of the vehicle.