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

Patent metadata

Field	Value
Publication number	US-10220943-B2
Application number	US-201615370426-A
Country	US
Kind code	B2
Filing date	Dec 6, 2016
Priority date	Dec 21, 2015
Publication date	Mar 5, 2019
Grant date	Mar 5, 2019

Abstract

A blade of a rotor for a rotary wing aircraft. The blade presents a combination of relationships for variation in the sweep, the chord, and the twist of the airfoil profiles of the sections of the blade in order, firstly to improve the aerodynamic performance of the blade both in forward flight and in stationary flight, and secondly to reduce the noise given off during approach flight. The blade is double-tapered and presents three sweeps. The twist relationship is substantially constant over a first portion of the blade, and then decreases over the remainder of the blade in linear or in non-linear manner. Suitable variation in the gradient of the twist of the blade makes it possible to improve the aerodynamic performance of the blade in forward flight and in hovering 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 c over 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 its chord and in its twist, the twist being formed by angular variations between the airfoil profiles of the blade, 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 the twist decreasing between a second section S 2 situated at a second distance from the axis of rotation (A) lying in the range 0.3R to 0.4R and the blade tip, a first gradient of the twist lying in the range −25°/R to −4°/R 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 0.4R to 0.6R, a second gradient of the twist lying in the range −25°/R to −4°/R between the third section S 3 and a fourth section S 4 situated at a fourth distance from the axis of rotation (A) lying in the range 0.65R to 0.85R, a third gradient of the twist lying in the range −16°/R to −4°/R between the fourth section S 4 and a fifth section S 5 situated at a fifth distance from the axis of rotation (A) lying in the range 0.85R to 0.95R, a fourth gradient of the twist lying in the range −16°/R to 0°/R between the fifth section S 5 and the blade tip,
wherein the relationship for variation in its chord and in its twist are combined with a relationship for variation in its sweep, the sweep, which is the angle between the leading edge and the blade axis (B) being directed towards the front of the blade between the start of the airfoil portion and a ninth section S 9 situated at an eleventh 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 towards the front of the blade between the ninth section S 9 and a tenth section S 10 situated at a twelfth 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 towards the rear of the blade between the tenth section S 10 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).

2. A blade according to claim 1 , wherein the twist varies piecewise linearly between adjacent pairs of sections from the second, third, fourth, and fifth sections S 2 , S 3 , S 4 , and S 5 , and between the fifth section S 5 and the blade tip.

3. A blade according to claim 2 , wherein the first gradient of the twist is less than the second gradient of the twist, the third gradient of the twist is greater than the third gradient of the twist, and the third gradient of the twist is less than the fourth gradient of the twist.

4. A blade according to claim 1 , wherein the twist varies in non-linear manner over the airfoil portion, the first gradient of the twist reaching a first plateau lying in the range −25°/R to −15°/R in the vicinity of the third section S 3 , the second gradient of the twist reaching a second plateau lying in the range −14°/R to −4°/R in the vicinity of the fourth section S 4 , the third gradient of the twist reaching a third plateau lying in the range −16°/R to −6°/R in the vicinity of the fifth section S 5 , and the fourth gradient of the twist lying in the range −10°/R to 0°/R in the vicinity of the blade tip.

5. A blade according to claim 4 , wherein the first plateau is equal to −18°/R, the second plateau is equal to −6°/R, the third plateau is equal to −13°/R, and the fourth plateau of the twist is equal to −8°/R at the blade tip.

6. A blade according to claim 1 , wherein the variation of the twist is less than or equal to 2° between the start of the airfoil portion and the second section S 2 .

7. A blade according to claim 1 , wherein the second distance is equal to 0.35R, the third distance is equal to 0.48R, the fourth distance is equal to 0.78R, and the fifth distance is equal to 0.92R.

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

9. A 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 .

10. A blade according to claim 1 , wherein the chord decreases in non-linear manner beyond an eighth section S 8 situated at a tenth distance from the axis of rotation (A) lying in the range 0.9R to 0.95R to the blade tip.

11. A blade according to claim 10 , wherein the chord decreases in parabolic manner beyond the eighth section S 8 .

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

13. A blade according to claim 1 , wherein the forward first sweep angle α 1 is different from the forward second sweep angle α 2 .

14. A blade according to claim 13 , wherein the forward first sweep angle α 1 is strictly less than the forward second sweep angle α 2 .

15. A blade according to claim 1 , 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 ninth section S 9 , between the ninth section S 9 and the tenth section S 10 , and between the tenth section S 10 and the blade tip.

16. A 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°.

17. A 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:

Assignees

• Airbus Helicopters

Inventors

• Leusink Debbie
• Alfano David
• Gareton Vincent

Classifications

• B64C27/04

  Helicopters · CPC title

• B64C27/473 Primary

  Constructional features · CPC title

• B64C27/467 Primary

  Aerodynamic features · CPC title

• B64C27/463

  Blade tips · CPC title