Aircraft rotor blade sleeve having a protuberance in its rear zone, and a rotor provided with such a sleeve

Abstract

A sleeve connecting a blade to the hub of a rotor of a rotary wing aircraft. The sleeve has a leading edge and a trailing edge, together with a protuberance arranged on the trailing edge. The dimensions of the protuberance are linked to the dimensions of the sleeve. The presence of the protuberance serves to improve the aerodynamic behavior of the sleeve and of the rotor during rotation of the rotor while the aircraft is moving forwards, both when the sleeve is advancing and when it is retreating. The presence of the protuberance also serves to reduce the vibration generated by a wake of the rotor on a tail boom or on a horizontal and/or vertical stabilizer of the aircraft.

Claims

1. A thick aerodynamic envelope for connecting to a rotary hub of an aircraft, the thick aerodynamic envelope extending firstly spanwise in a longitudinal direction from a first end zone to a second end zone, and secondly in a transverse direction between two transverse edges, the two transverse edges being a leading edge and a trailing edge, the thick aerodynamic envelope having a first suction-side surface and a first pressure-side surface, the thick aerodynamic envelope being defined by a first length L equal to a distance between the first end zone and the second end zone along the longitudinal direction; the thick aerodynamic envelope being formed by a succession of first profiles situated in planes parallel to a transverse plane perpendicular to the longitudinal direction, each first profile being defined in a plane parallel to the transverse plane by a thickness h equal to a maximum distance between the first suction-side surface and the first pressure-side surface; wherein the thick aerodynamic envelope includes at least one protuberance arranged on at least one of the transverse edges, the at least one protuberance being secured to the thick aerodynamic envelope, the at least one protuberance having a second suction-side surface and a second pressure-side surface, the at least one protuberance extending transversely from the transverse edge on which the at least one protuberance is arranged to a transverse end of the at least one protuberance where the second suction-side surface meets the second pressure-side surface, the at least one protuberance being configured to improve the aerodynamic behavior of the thick aerodynamic envelope when the thick aerodynamic envelope impacts a stream of air either with the leading edge or with the trailing edge, the at least one protuberance being defined by a second length L′ equal to a distance between a third end zone and a fourth end zone of the at least one protuberance along the longitudinal direction, the second length L′ lying in a range 0.5 to 1 times the first length L of the thick aerodynamic envelope, the at least one protuberance being formed by a succession of second profiles situated in planes parallel to the transverse plane, each second profile being defined by: a height h′ equal to a distance between the second suction-side surface and the second pressure-side surface, the height h′ lying in a range 0.2 to 0.6 times the thickness h of the thick aerodynamic envelope; a width ′ equal to a distance between the succession of first profiles and the transverse end along the transverse direction, the width ′ being equal to 0.5 to 2 times the height h; non-zero connection radii between the succession of first profiles and the succession of second profiles; and a radius of curvature of the transverse end of the at least one protuberance between the second suction-side surface and the second pressure-side surface that is greater than a minimum radius R.sub.mini.

2. The thick aerodynamic envelope according to claim 1, wherein the thick aerodynamic envelope and the at least one protuberance form a single part such that the first suction- and pressure-side surfaces and the second suction- and pressure-side surfaces form a single envelope.

3. The thick aerodynamic envelope according to claim 1, wherein the at least one protuberance is an element added on the thick aerodynamic envelope.

4. The thick aerodynamic envelope according to claim 1, wherein the second suction-side surface and the second pressure-side surface include a respective point of inflection.

5. The thick aerodynamic envelope according to claim 1, wherein the non-zero connection radii between firstly the first suction-side surface and the second suction-side surface, and secondly between the first pressure-side surface and the second pressure-side surface are greater than or equal to 25% of the height h′ of the at least one protuberance, and are configured in such a manner that a tangentially continuous connection exists between firstly the first suction-side surface and the second suction-side surface and secondly between the first pressure-side surface and the second pressure-side surface.

6. The thick aerodynamic envelope according to claim 1, wherein the minimum radius R.sub.mini is greater than or equal to 15% of the height h′ of the at least one protuberance.

7. The thick aerodynamic envelope according to claim 1, wherein, in each plane parallel to the transverse plane, each second profile of the at least one protuberance is arranged perpendicularly to a straight line connecting together the two points of intersection between one first profile of the succession of first profiles of the thick aerodynamic envelope and one second profile of the succession of second profiles of the at least one protuberance.

8. The thick aerodynamic envelope according to claim 1, wherein, in each plane parallel to the transverse plane, each second profile of the at least one protuberance is arranged so as not to be perpendicular to a straight line connecting together the two points of intersection between one first profile of the succession of first profiles of the thick aerodynamic envelope and one second profile of the succession of second profiles of the at least one protuberance.

9. The thick aerodynamic envelope according to claim 1, wherein in each plane parallel to the transverse plane, one second profile of the succession of second profiles of the at least one protuberance has an axis of symmetry.

10. The thick aerodynamic envelope according to claim 1, wherein a chord of the thick aerodynamic envelope is equal to a maximum distance between the leading edge and the trailing edge, and a relative thickness of the thick aerodynamic envelope equal to a ratio of the thickness h divided by the chord lies in a range 40% to 100%.

11. The thick aerodynamic envelope according to claim 1, wherein the width ′ varies in application of a spanwise variation relationship along the longitudinal direction.

12. The thick aerodynamic envelope according to claim 1, wherein the height h′ varies in application of a spanwise variation relationship along the longitudinal direction.

13. The thick aerodynamic envelope according to claim 1, wherein the at least one protuberance comprises one protuberance arranged on the trailing edge of the thick aerodynamic envelope.

14. A rotor of an aircraft, the rotor having a hub, at least two blades, and thick aerodynamic envelopes, each thick aerodynamic envelope connecting a respective blade to the hub, wherein each thick aerodynamic envelope is in accordance with claim 1, and the at least one protuberance being configured in such a manner as to reduce the production of a wake of the at least one rotor and to limit an amplitude of unsteadinesses contained in the wake, and also to reduce a frequency signature of the wake.

15. A rotary wing aircraft having a fuselage, a tail boom, at least one vertical stabilizer, and at least one rotor, wherein the at least one rotor is in accordance with claim 14, the at least one protuberance being configured such that firstly it reduces the production of the wake of the at least one rotor and the unsteadinesses of the wake, and secondly it limits the appearance of vibrations in the tail boom and/or in the vertical stabilizer as generated by the wake.

16. An aerodynamic envelope for connecting to a rotary hub of an aircraft, the aerodynamic envelope extending spanwise in a longitudinal direction from a first end zone to a second end zone, and in a transverse direction between two transverse edges, the two transverse edges being a leading edge and a trailing edge, the aerodynamic envelope having a first suction-side surface and a first pressure-side surface, the aerodynamic envelope being defined by a first length L equal to a distance between the first end zone and the second end zone along the longitudinal direction; the aerodynamic envelope being defined by a succession of first profiles situated in planes parallel to a transverse plane perpendicular to the longitudinal direction, each first profile being defined in a plane parallel to the transverse plane by a thickness h equal to a maximum distance between the first suction-side surface and the first pressure-side surface; wherein the aerodynamic envelope includes a protuberance disposed on one of the transverse edges, the protuberance secured to the aerodynamic envelope, the protuberance having a second suction-side surface and a second pressure-side surface, the protuberance extending transversely from the transverse edge on which the protuberance is arranged to a transverse end of the protuberance where the second suction-side surface meets the second pressure-side surface, the protuberance defined by a second length L′ equal to a distance between a third end zone and a fourth end zone of the protuberance along the longitudinal direction, the second length L′ lying in a range 0.5 to 1 times the first length L of the aerodynamic envelope, the protuberance being defined by a succession of second profiles situated in planes parallel to the transverse plane, each second profile being defined by: a height h′ equal to a distance between the second suction-side surface and the second pressure-side surface, the height h′ lying in a range 0.2 to 0.6 times the thickness h of the aerodynamic envelope; a width ′ equal to a distance between the succession of first profiles and the transverse end along the transverse direction, the width ′ being equal to 0.5 to 2 times the height h; non-zero connection radii between the succession of first profiles and the succession of second profiles; and a radius of curvature of the transverse end of the protuberance between the second suction-side surface and the second pressure-side surface that is greater than a minimum radius R.sub.mini.

17. The aerodynamic envelope according to claim 16, wherein the non-zero connection radii between the first suction-side surface and the second suction-side surface, and between the first pressure-side surface and the second pressure-side surface are greater than or equal to 25% of the height h′ of the protuberance, and are configured in such a manner that a tangentially continuous connection exists between firstly the first suction-side surface and the second suction-side surface and secondly between the first pressure-side surface and the second pressure-side surface.

18. The aerodynamic envelope according to claim 16, wherein the minimum radius R.sub.mini is greater than or equal to 15% of the height h′ of the protuberance.

19. A rotary wing aircraft comprising: a fuselage; a tail boom, a vertical stabilizer, and a rotor having a hub, two blades, and two aerodynamic envelopes, each aerodynamic envelope connecting a respective blade to the hub, wherein each aerodynamic envelope extends spanwise in a longitudinal direction from a first end zone to a second end zone, and in a transverse direction between two transverse edges, the two transverse edges being a leading edge and a trailing edge, the aerodynamic envelope having a first suction-side surface and a first pressure-side surface, the aerodynamic envelope being defined by a first length L equal to a distance between the first end zone and the second end zone along the longitudinal direction; the aerodynamic envelope being defined by a succession of first profiles situated in planes parallel to a transverse plane perpendicular to the longitudinal direction, each first profile being defined in a plane parallel to the transverse plane by a thickness h equal to a maximum distance between the first suction-side surface and the first pressure-side surface; wherein the aerodynamic envelope includes a protuberance disposed on one of the transverse edges, the protuberance secured to the aerodynamic envelope, the protuberance having a second suction-side surface and a second pressure-side surface, the protuberance extending transversely from the transverse edge on which the protuberance is arranged to a transverse end of the protuberance where the second suction-side surface meets the second pressure-side surface, the protuberance defined by a second length L′ equal to a distance between a third end zone and a fourth end zone of the protuberance along the longitudinal direction, the second length L′ lying in a range 0.5 to 1 times the first length L of the aerodynamic envelope, the protuberance being defined by a succession of second profiles situated in planes parallel to the transverse plane, each second profile being defined by: a height h′ equal to a distance between the second suction-side surface and the second pressure-side surface, the height h′ lying in a range 0.2 to 0.6 times the thickness h of the aerodynamic envelope; a width ′ equal to a distance between the succession of first profiles and the transverse end along the transverse direction, the width ′ being equal to 0.5 to 2 times the height h′; non-zero connection radii between the succession of first profiles and the succession of second profiles; and a radius of curvature of the transverse end of the protuberance between the second suction-side surface and the second pressure-side surface that is greater than a minimum radius R.sub.mini.

20. The rotary wing aircraft of claim 19, wherein the non-zero connection radii between the first suction-side surface and the second suction-side surface, and between the first pressure-side surface and the second pressure-side surface are greater than or equal to 25% of the height h′ of the protuberance, and wherein the minimum radius R.sub.mini is greater than or equal to 15% of the height h′ of the protuberance.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention and its advantages appear in greater detail from the context of the following description of embodiments given by way of illustration and with reference to the accompanying figures, in which:

(2) FIG. 1 shows an aircraft having a rotor;

(3) FIGS. 2 and 3 are fragmentary views of a rotor;

(4) FIG. 4 is a perspective view of a prior art sleeve;

(5) FIG. 5 is a perspective view of a thick aerodynamic envelope of the invention; and

(6) FIGS. 6 to 8 are transverse views of thick aerodynamic envelopes.

DETAILED DESCRIPTION OF THE INVENTION

(7) Elements present in more than one of the figures are given the same references in each of them.

(8) FIG. 1 shows a rotary wing aircraft 5 having a fuselage 51, a main rotor 10, and a tail boom 52 supporting a yaw anti-torque auxiliary rotor 53 and a vertical stabilizer 54. The rotor 10 has a hub 3, five blades 2, and five sleeves 1, together with a cover 35 and inter-blade dampers 32. The cover 35 serves to protect and to fair the head of the rotor 10.

(9) FIGS. 2 and 3 show the central portion of the rotor 10, the free end of each blade 2 being truncated. Only the root 25 of each blade 2 can be seen in the figures. In FIG. 3, the cover 35 is shown transparently so as to reveal the hub 3 and the dampers 32.

(10) Each blade 2 serves to generate an aerodynamic lift force during rotation of the rotor 10 in order to provide the aircraft 5 with lift and with propulsion. Each sleeve 1 is a thick aerodynamic envelope providing aerodynamic fairing for a structural junction device (not shown) connecting the blade 2, and more precisely the blade root 25, to the hub 3 of the rotor 10.

(11) A thick aerodynamic envelope 1 fitted with a protuberance 4 of the invention is shown in perspective in FIG. 5 together with the module root 25, while FIG. 4 shows a prior art thick aerodynamic envelope 1 providing a blade root with aerodynamic fairing.

(12) Each blade 2 and each thick aerodynamic envelope 1 extends spanwise in a longitudinal direction X. A transverse direction Y is perpendicular to the longitudinal direction X, and an elevation direction Z is defined perpendicularly to the longitudinal and transverse directions X and Y so as to form a right-hand rectangular reference frame (X,Y,Z). A transverse plane Pyz perpendicular to the longitudinal direction X is also defined by the transverse and elevation directions Y and Z.

(13) FIGS. 6 to 8 are cross-sections parallel to the transverse plane Pyz in embodiments of thick aerodynamic envelopes 1 provided with one or two protuberances 4.

(14) The thick aerodynamic envelope 1 extends firstly spanwise in the longitudinal direction X from a first end zone 13 situated beside the hub 3 towards a second end zone 14 situated beside the blade root 25, and secondly in the transverse direction Y between a leading edge 15 and a trailing edge 16. The thick aerodynamic envelope 1 has a first suction-side surface 17 and a first pressure-side surface 18.

(15) A first profile 11 of the thick aerodynamic envelope 1 is defined in each plane parallel to the transverse plane Pyz by:

(16) a chord equal to a maximum distance between the leading edge 15 and the trailing edge 16;

(17) a thickness h equal to a maximum distance between the first suction-side surface 17 and the first pressure-side surface 18 in the elevation direction Z; and

(18) a relative thickness equal to the ratio of the thickness h divided by the chord , and lying for example in the range 40% to 100%.

(19) The thick aerodynamic envelope 1 is also defined by a first length L equal to a distance between the first end zone 13 and the second end zone 14 in the spanwise longitudinal direction X.

(20) The thick aerodynamic envelope 1 of the invention includes at least one protuberance 4 that is visible in FIGS. 2, 3, and 5 to 8. Each protuberance 4 has a second suction-side surface 47 and a second pressure-side surface 48, the second suction- and pressure-side surfaces 47 and 48 meeting at a transverse end 46 of the protuberance 4. Each protuberance 4 extends firstly longitudinally along the longitudinal direction X from a third end zone 43 situated beside the hub 3 to a fourth end zone 44 situated beside the blade root 25, and secondly transversely in the transverse direction Y from the transverse edge 15, 16 on which the protuberance 4 is arranged towards the transverse end 46.

(21) The first suction- and pressure-side surfaces 17 and 18 of the thick aerodynamic envelope 1 and the second suction- and pressure-side surfaces 47 and 48 of each protuberance 4 form a single envelope.

(22) A second profile 41 of each protuberance 4 is defined in each plane parallel to the transverse plane Pyz by:

(23) a height h′ equal to a distance between the second suction- and pressure-side surfaces 47 and 48 in the elevation direction Z, the height h′ lying in the range 0.2 to 0.6 times the thickness h of the thick aerodynamic envelope 1;

(24) a width ′ equal to a distance between the transverse edge 15, 16 on which the protuberance 4 is arranged and the transverse end 46 of the protuberance 4 in the transverse direction Y, the width ′ lying in the range 0.5 to 2 times the height h′ of the protuberance 4;

(25) non-zero connection radii, e.g. radii greater than or equal to 25% of the height h′ of the protuberance 4, firstly between the first suction-side surface 17 and the second suction-side surface 47, and secondly between the first pressure-side surface 18 and the second pressure-side surface 48; and

(26) a radius of curvature of the transverse end 46 between the second suction-side surface 47 and the second pressure-side surface 48 that is greater than a minimum radius R.sub.mini, which by way of example is greater than or equal to 15% of the height h′ of the protuberance 4.

(27) By way of example, and as shown in FIGS. 6 and 8, the protuberance 4 has a second profile 41 of Gaussian shape with a broad base and a narrow transverse end 46.

(28) The protuberance 4 is also defined by a second length L′ equal to a distance between the third end zone 43 and the fourth end zone 44 in the longitudinal direction X, the second length L′ lying in the range 0.5 to 1 times the first length L of the thick aerodynamic envelope 1.

(29) The presence of this protuberance 4 serves advantageously to improve the aerodynamic behavior of the thick aerodynamic envelope 1 during rotation of the rotor 10, for a thick aerodynamic envelope 1 both when it is advancing and when it is retreating, firstly by reducing the aerodynamic drag and the production of a wake, and secondly by limiting the amplitude of the unsteadinesses contained in the wake and limiting the amplitude of the frequency signature of the wake.

(30) The protuberance 4 is of a shape that tapers from the transverse edge 15, 16 on which the protuberance 4 is arranged and going towards the transverse end 46. As a result, the height h′, which is a maximum distance between the second suction-side surface 47 and the second pressure-side surface 48 in the elevation direction Z, is defined by two junction points A, B: the first junction point A being the point of intersection between the first suction-side surface 17 and the second suction-side surface 47; and the second junction point B being the point of intersection between the first pressure-side surface 18 and the second pressure-side surface 48, as shown in FIGS. 6 and 7.

(31) Furthermore, the second suction-side surface 47 and the second pressure-side surface 48 have a point of inflection between each junction point A, B and the transverse end 46 so as to enable the stream of air to flow continuously and without encountering any sharp edge. As a result, the thick aerodynamic envelope 1 of the invention also limits the appearance of turbulence in the air stream sweeping over it.

(32) In FIGS. 5 to 7, the protuberance 4 is arranged on the trailing edge 17 of the thick aerodynamic envelope 1. In FIG. 8, two protuberances 4 and 4′ are arranged on the thick aerodynamic envelope 1, a first protuberance 4 being arranged on the trailing edge 16, and a second protuberance 4′ being arranged on the leading edge 15. Nevertheless, a protuberance 4 may be arranged on the leading edge 17 only of a thick aerodynamic envelope 1.

(33) The thick aerodynamic envelope 1 shown in the figures is a long thick aerodynamic envelope, however a protuberance 4 may also be arranged on the leading edge 15 and/or the trailing edge 16 of a short thick aerodynamic envelope 1.

(34) In FIGS. 2, 3, and 5, it can be seen that the second length L′ of the protuberance 4 is strictly less than the first length L of the thick aerodynamic envelope 1. Under such circumstances, in order to enable a progressive connection to be made between the transverse end 46 of the protuberance 4 and each of the first suction- and pressure-side surfaces 17 and 18, the thick aerodynamic envelope 1 has two connection zones 45 and 49 arranged respectively going from the third and fourth end zones 43 and 44 towards respectively the first end zone 13 and the second end zone 14. Each connection zone 45, 49 has non-zero connection radii and a slope for connecting the transverse end 46 progressively to the first suction- and pressure-side surfaces 17 and 18 at the third end zone 43 beside the hub 3 and at the fourth end zone 44 beside the blade root 25.

(35) Furthermore, in FIGS. 6 and 8, each protuberance 4 is symmetrical relative to the transverse direction Y, the protuberance 4 being arranged substantially perpendicularly to the trailing edge 16; and in the example of FIG. 8, the protuberance 4′ is arranged substantially perpendicularly to the leading edge 15.

(36) In FIG. 7, the protuberance 4 slopes relative to the transverse direction Y and is arranged in a manner that is not perpendicular to the trailing edge 16. This protuberance 4 thus does not have an axis of symmetry.

(37) Naturally, the present invention may be subjected to numerous variations as to its implementation. Although several embodiments are described, it will readily be understood that it is not conceivable to identify exhaustively all possible embodiments.

(38) For example, a thick aerodynamic envelope 1 having one or more protuberances 4 may be arranged on an anti-torque auxiliary rotor of a rotary wing aircraft, or indeed on a propulsive rotor of an aircraft.

(39) It is naturally possible to envisage replacing any of the means described by equivalent means without going beyond the ambit of the present invention.