Low-noise multi-propeller system

Patent metadata

Field	Value
Publication number	US-11565790-B2
Application number	US-201916597499-A
Country	US
Kind code	B2
Filing date	Oct 9, 2019
Priority date	Oct 9, 2018
Publication date	Jan 31, 2023
Grant date	Jan 31, 2023

Abstract

A low-noise multi-propeller system includes at least two propellers, each propeller including at least two blades. The propellers rotate in a first direction and define an angular phase relative to one another. A drive system corotates the propellers at substantially equal rotational rates in the first direction. The propellers are substantially phase-locked at a predefined relative phase offset that reduces the overall sound power of the fundamental tone at a blade passage frequency.

First claim

What is claimed is:

1. A low-noise multi-propeller system for aerial vehicles comprising:
at least two propellers, each propeller configured to define an axis of rotation and having at least two blades, the at least two propellers having an equal number of blades, wherein the at least two propellers define an angular phase relative to one another;
a drive system configured to corotate the at least two propellers at substantially equal rotational rates in a first direction, wherein the drive system is configured to substantially phase-lock the at least two propellers at a predefined relative phase offset to reduce radiated sound power at a blade passage frequency, wherein the radiated sound power is the total energy radiated in all directions per unit time.

2. The multi-propeller system of claim 1 , wherein:
the predefined relative phase offset is substantially equal to 180-degrees divided by the number of blades of the at least two propellers.

3. The multi-propeller system of claim 1 , wherein:
the predefined relative phase offset is substantially equal to the difference of 180-degrees divided by the number of blades of the at least two propellers and 180-degrees divided by the product of the number of blades of the at least two propellers and the number of propellers.

4. The multi-propeller system of claim 1 , wherein:
the axes of rotation of the at least two propellers are substantially parallel.

5. The multi-propeller system of claim 4 , wherein:
the at least two propellers consists of two propellers.

6. The multi-propeller system of claim 5 , wherein:
the axes of the two propellers are spaced-apart a distance that is less than one half an acoustic wavelength of a fundamental tone at the blade passage frequency.

7. The multi-propeller system of claim 1 , wherein:
the at least two propellers have substantially identical sizes and shapes.

8. The multi-propeller system of claim 1 , wherein:
the at least two propellers consists of three propellers.

9. The multi-propeller system of claim 8 , wherein:
the three propellers are arranged in a triangle.

10. The multi-propeller system of claim 1 , wherein:
the at least two propellers consists of four propellers.

11. The multi-propeller system of claim 10 , wherein:
the four propellers are arranged linearly.

12. The multi-propeller system of claim 1 , wherein:
the multi-propeller system is configured to provide thrust for an aerial vehicle for at least one of 1) vertical take-off and/or landing; and 2) horizontal flight.

13. The multi-propeller system of claim 1 , wherein:
the at least two propellers are mounted to a wing of an aerial vehicle.

14. An aerial vehicle comprising:
a vehicle body;
a low-noise multi-propeller system having at least two non-overlapping propellers, each propeller configured to define an axis of rotation and having at least two blades, the at least two propellers having an equal number of blades, wherein the at least two propellers define an angular phase relative to one another and the axes of the two propellers are substantially parallel;
a powered drive system corotating the at least two propellers at substantially equal rotational rates in a first direction, wherein the drive system phase-locks the at least two propellers at a predefined relative phase offset, wherein the predefined relative phase offset is specifically precalculated to reduce radiated sound power at a blade passage frequency relative to a radiated sound power at a blade passage frequency of the at least two propellers when the at least two propellers are not phase-locked, wherein the radiated sound power is the total energy radiated in all directions per unit time and wherein the axes of the at least two propellers are spaced-apart a distance that is less than one half an acoustic wavelength of a fundamental tone at a blade passage frequency.

15. The aerial vehicle of claim 14 , wherein;
the predefined relative phase offset is substantially equal to 180-degrees divided by the number of blades of the at least two propellers.

16. The aerial vehicle of claim 14 , wherein;
the at least two propellers comprises an odd number of propellers positioned near the vertices of a normal polygon, and the predefined relative phase offset Δψ r is substantially equal to the difference of 1) 180-degrees divided by the number of blades of the at least two propellers and 2) 180-degrees divided by the product of the number of blades of the at least two propellers and the number of propellers (N p N b ), according to Δψ r =180°/N b −180°/(N p N b ).

17. The aerial vehicle of claim 14 , wherein:
the aerial vehicle comprises a multicopter having a plurality of groups of propellers, each group of propellers comprising at least two phase-locked propellers.

18. The aerial vehicle of claim 17 , wherein;
the rotational rate of each group of propellers is independently controlled.

19. An aerial vehicle comprising:
a vehicle body;
a low-noise multi-propeller system having at least two propellers, each propeller configured to define an axis of rotation and having at least two blades, the at least two propellers having an equal number of blades, wherein the at least two propellers define an angular phase relative to one another and the axes of the two propellers are substantially parallel;
a powered drive system configured to corotate the at least two propellers at substantially equal rotational rates in a first direction, wherein the drive system is configured to phase-lock the at least two propellers at a predefined relative phase offset, wherein the predefined relative phase offset reduces total energy radiated in all directions per unit time at a blade passage frequency, and wherein:
the axes of the at least two propellers are spaced-apart a distance that is less than one half an acoustic wavelength of a fundamental tone at a blade passage frequency.

20. The aerial vehicle of claim 14 , wherein:
none of the blades of the at least two propellers overlap.

21. The aerial vehicle of claim 20 , wherein:
the powered drive system comprises a phase-locked mechanical drive that drives the at least two propellers at the predefined relative phase offset.

Assignees

• Nasa

Inventors

• Schiller Noah H
• Zawodny Nikolas S
• Pascioni Kyle A
• Rizzi Stephen A

Classifications

• B64C11/50 Primary

  Phase synchronisation between multiple propellers · CPC title