US-12623775-B2 - Rotorcraft and rotor blade

US12623775B2US 12623775 B2US12623775 B2US 12623775B2US-12623775-B2

Abstract

The disclosed rotorcraft includes a rotor blade and a prime mover. The rotor blade extends in a radial direction. The prime mover is configured to rotate the rotor blade. The rotor blade includes a blade body and a blade end portion. The blade end portion is disposed on an outer side of the blade body in the radial direction. The blade end portion includes a leading edge (i.e., an edge facing the rotational direction) that tilts in a rotational direction to the outer side in the radial direction. The disclosed configuration reduces noise produced by the rotorcraft.

Inventors

Kouzou Mori
Yasunori Kunisaki
Tatsuki Kitada
Masahiro Ohno

Assignees

EXEDY CORPORATION

Dates

Publication Date: 20260512
Application Date: 20250131
Priority Date: 20240229

Claims (14)

1 . A rotorcraft, comprising: a rotor blade extending in a radial direction the rotor blade having a proximal end and a distal end opposite the proximal end; and a prime mover configured to rotate the rotor blade and being configured to be connected to the proximal end, wherein the rotor blade includes a blade body and a blade end portion disposed at a radially outer end of the blade body, the distal end having a distal point being a point farthest from a rotational axis of the rotor blade and a distal edge extending from one side of the blade body to another side of the blade body with the distal point lying on the distal edge, and the blade end portion includes a leading edge facing forward in a rotational direction, a proximal end of the leading edge extending from the blade body and a distal end of the leading edge opposite the proximal end of the leading edge, the entirety of the leading edge being angled forwardly in the rotational direction with a forward sweep angle such that the distal end of the leading edge and the distal edge of the rotor blade have a shared point.
2 . The rotorcraft according to claim 1 , wherein a leading edge of the blade body includes at least one protrusion protruding forwardly in the rotational direction.
3 . The rotorcraft according to claim 1 , wherein the blade end portion is angled upwardly with a positive dihedral angle relative to the blade body.
4 . A rotor blade configured to be rotated in a rotational direction, the rotor blade comprising: a blade body; a proximal end being configured to be attached to a prime mover; a distal end being opposite the proximal end, the distal end having a distal point being a point farthest from a rotational axis of the rotor blade and a distal edge extending from one side of the blade body to another side of the blade body with the distal point lying on the distal edge; and a blade end portion disposed at a radially outer end of the blade body, wherein the blade end portion includes a leading edge facing forward in the rotational direction, a proximal end of the leading edge extending from the blade body and a distal end of the leading edge opposite the proximal end of the leading edge, the entirety of the leading edge being angled forwardly in the rotational direction with a forward sweep angle such that the distal end of the leading edge and the distal edge of the rotor blade have a shared point.
5 . The rotorcraft according to claim 1 , wherein the blade end portion has a trailing edge opposite the leading edge, the trailing edge angles in an identical direction to the leading edge.
6 . The rotorcraft according to claim 5 , wherein the trailing edge and the leading edge are straight.
7 . The rotorcraft according to claim 2 , wherein the least one protrusion is spaced apart from the blade end portion.
8 . The rotorcraft according to claim 7 , wherein the blade body comprises more than one protrusion.
9 . The rotor blade according to claim 4 , wherein a leading edge of the blade body includes at least one protrusion protruding forwardly in the rotational direction.
10 . The rotor blade according to claim 4 , wherein the blade end portion is angled upwardly with a positive dihedral angle relative to the blade body.
11 . The rotor blade according to claim 4 , wherein the blade end portion has a trailing edge opposite the leading edge, the trailing edge angles in an identical direction to the leading edge.
12 . The rotor blade according to claim 11 , wherein the trailing edge and the leading edge are straight.
13 . The rotor blade according to claim 9 , wherein the least one protrusion is spaced apart from the blade end portion.
14 . The rotor blade according to claim 13 , comprising more than one protrusion.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is based on and claims the priority benefit of application No. 2024-029525 filed on Feb. 29, 2024, the contents of which are incorporated herein by reference. TECHNICAL FIELD The claimed invention relates to a rotorcraft and a rotor blade. BACKGROUND Rotorcraft such as industrial drones have become ubiquitous in recent years. For example, a drone described in Japan Laid-open Patent Application Publication No. 2023-184048 includes rotor blades and motors for rotating the rotor blades. SUMMARY OF THE INVENTION The rotorcraft described above has a drawback that noise is produced by the rotation of rotor blades. In view of this, it is an object of the claimed invention to provide a rotorcraft in which the production of noise can be reduced. A rotorcraft according to a first aspect includes a rotor blade and a prime mover. The rotor blade extends in a radial direction. The prime mover is configured to rotate the rotor blade. The rotor blade includes a blade body and a blade end portion. The blade end portion is disposed on an outer side of the blade body in the radial direction. The blade end portion includes a leading edge angled in a rotational direction to the outer side in the radial direction. It should be noted that the leading edge of the blade end portion refers to an edge facing the rotational direction. According to this configuration, the leading edge of the blade end portion of the rotor blade is angled in the rotational direction to the outer side in the radial direction; hence, a pressure acting on the upper surface of the blade end portion can be increased in magnitude. Because of this, a difference between the pressure acting on the lower surface and that acting on the upper surface in the blade end portion is made small, whereby generation of a vortex flowing around the blade end portion from the lower surface to the upper surface can be inhibited. As a result, the generation of blade end vortex can be inhibited, whereby production of noise due to the rotation of the rotor blade can be reduced. A rotorcraft according to a second aspect relates to the rotorcraft according to the first aspect and is configured as follows. The blade body includes at least one protrusion protruding in the rotational direction. According to this configuration, a vortex, generated behind the blade body can be inhibited from growing by the at least one protrusion. A rotorcraft according to a third aspect relates to the rotorcraft according to the first or second aspect and is configured as follows. The blade end portion is angled upward to the outer side in the radial direction. A rotor blade according to a fourth aspect is configured to be rotated in a rotational direction. The rotor blade includes a blade body and a blade end portion. The blade end portion is disposed on an outer side of the blade body in a radial direction. The blade end portion includes a leading edge that is angled in the rotational direction to the outer side in the radial direction. It should be noted that the leading edge of the blade end portion refers to an edge facing the rotational direction. Overall, according to the claimed invention, production of noise can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of an embodiment of a rotorcraft in accordance with the claimed invention. FIG. 2 is a plan view of a rotor blade used in the rotorcraft illustrated in FIG. 1. FIG. 3 is a front view of the rotor blade (i.e. a view of the rotor blade leading edge). FIG. 4 is a diagram showing distribution of pressure acting on a configuration of a rotor blade, in which a first, sweep angle α is 30° and a second, dihedral angle β is 0°. FIG. 5 is a diagram showing distribution of pressure acting on another configuration of a rotor blade, in which the first, sweep angle α is 0° and the second, dihedral angle β is 0°. FIG. 6 is a diagram showing distribution of pressure acting on another configuration of a rotor blade, in which the first, sweep angle α is 30° and the second, dihedral angle β is 15°. FIG. 7 is a diagram showing distribution of pressure acting on another configuration of a rotor blade, in which the first, sweep angle α is 0° and the second, dihedral angle β is 15°. FIG. 8 is a diagram showing distribution of pressure acting on another configuration of a rotor blade, in which the first, sweep angle α is −30° and the second, dihedral angle β is 15°. FIG. 9 is a diagram showing distribution of pressure acting on another configuration of a rotor blade in which the blade end portion thereof is increased in length as compared to a rotor blade for which FIG. 6 shows pressure distribution. FIG. 10 is a diagram showing a distribution of pressure acting on another configuration of rotor blade in which the blade end portion thereof is reduced in length as compared to a rotor blade for which FIG. 6 shows pressure distribution. FIG. 11 is a diagram showing a distribution of press