Aircraft rotor blade of shape adapted for acoustic improvement during an approach flight and for improving performance in forward flight

Patent metadata

Field	Value
Publication number	US-10414490-B2
Application number	US-201615370403-A
Country	US
Kind code	B2
Filing date	Dec 6, 2016
Priority date	Dec 21, 2015
Publication date	Sep 17, 2019
Grant date	Sep 17, 2019

Abstract

A blade of a rotor for a rotary wing aircraft. The blade presents relationships for variation in the sweep and in the chord of the profiles of sections of the blade, in particular in order to improve the twisting stiffness and the bending stiffness of the blade. The blade is then double-tapered and it presents three sweeps, making it possible firstly to improve the aerodynamic performance of the blade in forward flight, and secondly to reduce the noise given off by the blade, in particular during an approach flight.

First claim

What is claimed is:

1. A blade for a rotor of a rotary wing aircraft, the blade being for rotating about an axis of rotation (A), the blade extending firstly along a blade axis (B) between a blade start suitable for being connected to a hub of the rotor and a blade tip situated at a free end of the blade, and secondly along a transverse axis (T) perpendicular to the blade axis (B) between a leading edge and a trailing edge, the blade comprising:
an airfoil portion situated between the blade start and the blade tip, the airfoil portion being constituted by a succession of airfoil profiles, each airfoil profile being situated in a transverse plane substantially perpendicular to the blade axis (B) and defining a section of the blade, the blade tip being situated at a distance equal to a rotor radius R from the axis of rotation (A), a maximum distance between the leading edge and the trailing edge in the transverse plane constituting a chord c for the airfoil profile of each of the sections of the blade, a mean chord c being a mean value of the chord cover the airfoil portion, a forward first direction being defined from the trailing edge to the leading edge, and a rearward second direction being defined from the leading edge to the trailing edge,
the blade presenting a combination of relationships for variation in chord and in sweep, the sweep being the angle between the leading edge and the blade axis (B), the chord increasing between the start of the airfoil portion and a first section S 1 situated at a first distance from the axis of rotation (A) lying in the range 0.6R to 0.9R, the chord decreasing beyond the first section S 1 ; and
wherein the sweep is directed in the forward first direction of the blade between the start of the airfoil portion and a second section S 2 situated at a second distance from the axis of rotation (A) lying between 0.5R and 0.8R, the leading edge forming a forward first sweep angle α 1 that is strictly greater than 0° and less than 10° relative to the blade axis (B), the sweep being directed in the forward first direction of the blade between the second section S 2 and a third section S 3 situated at a third distance from the axis of rotation (A) lying in the range 0.6R to 0.95R, the leading edge forming a forward second sweep angle α 2 lying in the range 1° to 15° relative to the blade axis (B), the sweep being directed in the rearward second direction of the blade between the third section S 3 and the blade tip, the leading edge forming a backward third sweep angle α 3 lying in the range −35° to −15° relative to the blade axis (B),
wherein the forward first sweep angle α 1 is different from the forward second sweep angle α 2 ,
wherein the forward first sweep angle α 1 , the forward second sweep angle α 2 , and the backward third sweep angle α 3 are constant respectively between the start of the airfoil portion and the second section S 2 , between the second section S 2 and the third section S 3 , and between the third section S 3 and the blade tip.

2. The blade according to claim 1 , wherein the forward first sweep angle α 1 is strictly less than the forward second sweep angle α 2 .

3. The blade according to claim 1 , wherein the forward first sweep angle α 1 is equal to 4°, the forward second sweep angle α 2 is equal to 8°, and the backward third sweep angle α 3 is equal to −23°.

4. The blade according to claim 1 , wherein the blade start is situated at a fourth distance lying in the range 0.05R to 0.3R from the axis of rotation (A) and the start of the airfoil portion is situated at a fifth distance lying in the range 0.1R to 0.4R from the axis of rotation (A), the fifth distance being greater than or equal to the fourth distance, and the chord in the vicinity of the start of the blade lying in the range 0.4 c to 0.9 c .

5. The blade according to claim 1 , wherein the chord varies about the mean chord c by ±40% between the start of the airfoil portion and the first section S 1 .

6. The blade according to claim 1 , wherein the chord decreases in non-linear manner beyond a sixth section S 6 situated at an eighth distance from the axis of rotation (A) lying in the range 0.9R to 0.95R to the blade tip.

7. The blade according to claim 6 , wherein the chord decreases in parabolic manner beyond the sixth section S 6 .

8. The blade according to claim 1 , wherein the blade has a dihedral in the vicinity of the blade tip.

9. The blade according to claim 1 , wherein the mean chord c is defined by a radius squared r 2 weighting of the profile of each of the sections of the blade in application of the formula:

c
_

=

∫

R
0

R

⁢

L
⁡

(
r
)

·

r
2

·
dr

∫

R
0

R

⁢

r
2

·
dr

where L(r) is the length of the local chord of a profile of the blade, the local profile being situated at a radius r from the axis of rotation A, R 0 being the radius of the start of the airfoil portion, and R being the radius of the blade tip.

10. A rotor for a rotary wing aircraft, the rotor having at least two blades according to claim 1 .

11. A blade for a rotor of a rotary wing aircraft, the blade rotating about an axis of rotation and extending radially from the axis of rotation along a blade axis to a blade tip a distance equal to a rotor radius R, the blade having a chord dimension perpendicular to the blade axis between a leading edge and a trailing edge, the blade varying in the chord dimension and in sweep, the sweep being the angle between the leading edge and the blade axis, the blade comprising:
an increasing chord section extending from a blade start to a first distance from the axis of rotation located between 0.6R to 0.9R along which the chord dimension continuously increases;
a decreasing chord section extending from the first distance to the blade tip along which the chord dimension continuously decreases;
a first sweep section extending from a start of a blade airfoil shape to a second distance from the axis of rotation located between 0.5R and 0.8R at a forward first sweep angle greater than 0° and less than 10° relative to the blade axis in a forward direction of the blade;
a second sweep section extending from the second distance to a third distance from the axis of rotation located between 0.6R and 0.95R at a forward second sweep angle in the range of 1° to 15° relative to the blade axis in the forward direction of the blade, wherein the forward first sweep angle is different from the forward second sweep angle; and
a third sweep sect

Assignees

• Airbus Helicopters

Inventors

• Leusink Debbie
• Alfano David
• Gareton Vincent

Classifications

• B64C27/467

  Aerodynamic features · CPC title

• B64C27/463 Primary

  Blade tips · CPC title

• B64C27/473 Primary

  Constructional features · CPC title

• B64C27/04

  Helicopters · CPC title