초록 ▼

The twist distribution of torsionally-flexible rotor blades is adjusted by exploiting centrifugal effect on inertial torquers affixed at one or more stations along the blade span. Twist is thereby made to vary passively as a function of rotor speed and hub incidence angle. With inertias of appropria

The twist distribution of torsionally-flexible rotor blades is adjusted by exploiting centrifugal effect on inertial torquers affixed at one or more stations along the blade span. Twist is thereby made to vary passively as a function of rotor speed and hub incidence angle. With inertias of appropriate size and location, the twist variation is such that high rotor efficiency is maintained over a wide range of operating conditions. Satisfactory dynamic behavior of the blade, including cyclic-pitch response and flutter resistance, is simultaneously achieved.

대표청구항 ▼

The invention is claimed as follows: 1. A rotor blade comprising: (A) an elongated body (a) having a root, a tip, a span from the root to the tip, and a spanwise axis extending between the root and the tip, (b) having a leading edge, a trailing edge, and a chordwise axis extending between the leadi

The invention is claimed as follows: 1. A rotor blade comprising: (A) an elongated body (a) having a root, a tip, a span from the root to the tip, and a spanwise axis extending between the root and the tip, (b) having a leading edge, a trailing edge, and a chordwise axis extending between the leading edge and the trailing edge, (c) being flexible in twist about the spanwise axis along at least some of the span, (d) having a twist distribution across the span when in a state of rest, and (e) configured to be attachable at the root to a rotor hub which is operable (i) to spin the elongated body about an axis of rotation, said axis of rotation being transverse to the spanwise axis, and (ii) to variably set a hub incidence angle of the elongated body, said hub incidence angle being the angle between a plane normal to said axis of rotation and a root chordwise line, the root chordwise line being a chordwise line through the root of the elongated body; and (B) an inertial torquer attached to a station of the span of the elongated body, the inertial torquer: (a) having a moment of inertia and a principal axis of inertia, (b) including a first section and a second section positioned coaxially along said principal axis of inertia, (i) the first section having a first axis positioned along said principal axis of inertia, (ii) the second section having a second axis positioned along said principal axis of inertia, (c) including a first mass attached to the first section, and a second mass attached to the second section, (i) the first mass extending at a first designated distance from the spanwise axis of the elongated body, (ii) the second mass extending at a second designated distance from the spanwise axis of the elongated body, (iii) the first mass and the second mass extending from opposite surfaces of the elongated body, (d) positioned with said moment of inertia about said spanwise axis and with said principal axis of inertia angled relative to a station chordwise line, said station chordwise line being a chordwise line extending between the leading edge and the trailing edge of the elongated body at said station, (e) defining a first relative incidence angle, said first relative incidence angle being the angle between said station chordwise line and said first axis, (f) defining a second relative incidence angle, said second relative incidence angle being the angle between said station chordwise line and said second axis, (g) positioned such that said first relative incidence angle and said second relative incidence angle are each less than ninety degrees, and (h) configured such that (i) the centrifugal effect on the inertial torquer twists the elongated body such that the incidence distribution across the span of the elongated body varies with the rotational speed of the rotor hub about said axis of rotation and varies with said hub incidence angle of the elongated body, and (ii) in at least one operating condition of the rotor hub, a torsional equilibrium of the incidence distribution is substantially stiffened by the centrifugal effect on the inertial torquer. 2. The rotor blade of claim 1, which includes a plurality of the inertial torquers attached at radially-spaced positions along the elongated body. 3. The rotor blade of claim 2, wherein at least one of the first mass and the second mass is connected to the elongated body by at least one strut. 4. The rotor blade of claim 1, wherein at least one of the first masses and the second mass of the inertial torquer is connected to the elongated body by at least one strut. 5. The rotor blade of claim 1, wherein the rotor hub is capable of spinning the rotor blade about the spin axis at a first rotational speed and a second rotational speed, the first rotational speed being lower than the second rotational speed, the spanwise distribution of the elongated body twist at the state of rest being configured to maximize the generation of thrust at the first rotational speed. 6. The rotor blade of claim 1, said incidence distribution being variable, said variable incidence distribution varying with the spin rate and hub pitch of the elongated body so as to maximize thrust efficiency of the rotor. 7. The rotor blade of claim 1, wherein the inertial torquer has a mass center located forward of said span-wise axis. 8. The rotor blade of claim 1, wherein said inertial torquer has a streamlined configuration to minimize aerodynamic drag. 9. The rotor blade of claim 1, wherein the torsional stiffness of the elongated body, the inertia of the inertial torquer, and the position of said span-wise axis relative to the aerodynamic center of the elongated body, are such that when installed and spinning in a rotor, the lowest natural frequency of the elongated body when oscillating in torsion is faster than the spin frequency of the rotor. 10. The rotor blade of claim 1, wherein the rotor hub variably sets the hub incidence angle of the elongated body in a collective or cyclical manner. 11. The rotor blade of claim 1, wherein the rotor hub variably sets the hub incidence angle of the elongated body in both a collective and cyclical manner. 12. The rotor blade of claim 1, wherein the masses of said first mass and said second mass are different. 13. The rotor blade of claim 1, wherein the first designated distance and the second designated distance are different. 14. The rotor blade of claim 1, wherein the inertial torquer has a mass center located behind said spanwise axis. 15. A rotor comprising: a rotor hub; and at least one rotor blade including: (A) an elongated body (a) having a root, a tip, a span from the root to the tip, and a span wise-axis extending between the root and the tip, (b) having a leading edge, a trailing edge, and a chordwise axis extending between the leading edge and the trailing edge, (c) being flexible in twist about the span wise axis along at least some of the span, (d) having a twist distribution across the span when in a state of rest, and (e) attached at the root to the rotor hub which is operable (i) to spin the elongated body about an axis of rotation, said axis of rotation being transverse to the spanwise axis, and iii) to variably set a hub incidence angle of said elongated body, said hub incidence angle being an angle between a plane normal to said axis of rotation and a root chordwise line, the root chordwise line being a chordwise line through the root of the elongated body, and (B) an inertial torquer attached to a station of the span of the elongated body, the inertial torquer: (a) having a moment of inertia and a principal axis of inertia, (b) including a first section and a second section positioned coaxially along said principal axis of inertia, (i) the first section having a first axis positioned along said principal axis of inertia, (ii) the second section having a second axis positioned along said principal axis of inertia, (c) including a first mass attached to the first section, and a second mass attached to the second section, (i) the first mass extending at a first designated distance from the spanwise axis of the elongated body, (ii) the second mass extending at a second designated distance from the spanwise axis of the elongated body, (iii) the first mass and the second mass extending from opposite surfaces of the elongated body, (d) positioned with said moment of inertia about said spanwise axis and with said principal axis of inertia angled relative to a station chordwise line, said station chordwise line being a chordwise line extending between the leading edge and the trailing edge of the elongated body at said station, (e) defining a first relative incidence angle, said first relative incidence angle being the angle between said station chordwise line and said first axis, (f) defining a second relative incidence angle, said second relative incidence angle being the angle between said station chordwise line and said second axis, (g) positioned such that said first relative incidence angle and said second relative incidence angle are each less than ninety degrees, and (h) configured such that (i) the centrifugal effect on the inertial torquer twists the elongated body such that the incidence distribution across the span of the elongated body varies with the rotational speed of the rotor hub about said axis of rotation and varies with said hub incidence angle of the elongated body, and (ii) in at least one operating condition of the rotor hub, a torsional equilibrium of the incidence distribution is substantially stiffened by the centrifugal effect on the inertial torquer. 16. The rotor of claim 15, which includes a plurality of the inertial torquers attached at radially-spaced positions along the elongated body. 17. The rotor of claim 16, wherein at least one of the first mass and the second mass is connected to the elongated body by at least one strut. 18. The rotor of claim 15, wherein at least one of the first mass and the second mass of the inertial torquer is connected to the elongated body by at least one strut. 19. The rotor of claim 15, wherein the rotor hub is capable of spinning the rotor blade about the spin axis at a first rotational speed and a second rotational speed, the first rotational speed being lower than the second rotational speed, the spanwise distribution of elongated body twist at the state of rest being configured to maximize the generation of thrust at the first rotational speed. 20. The rotor of claim 15, said incidence distribution being variable, said variable incidence distribution varying with the spin rate and hub pitch of the elongated body so as to maximize of thrust efficiency of the rotor. 21. The rotor of claim 15, wherein the inertial torquer has a mass center located forward of said spanwise axis. 22. The rotor of claim 15, wherein the inertial torquer has a streamlined configuration to minimize aerodynamic drag. 23. The rotor of claim 15, wherein the torsional stiffness of the elongated body, the inertia of the inertial torquer, and the position of said spanwise axis relative to the aerodynamic center of the elongated body, are such that when installed and spinning, the lowest natural frequency of the elongated body when oscillating in torsion is faster than the spin frequency of the rotor. 24. The rotor of claim 15, wherein the rotor hub is configured to vary said hub incidence angle of the elongated body cyclically once per rotor revolution. 25. The rotor of claim 15, wherein the rotor hub variably sets the hub incidence angle of the elongated body in a collective or cyclical manner. 26. The rotor of claim 15, wherein the rotor hub variably sets the hub incidence angle of the elongated body in both a collective and cyclical manner. 27. The rotor of claim 15, wherein the masses of said first mass and said second mass are different. 28. The rotor of claim 15, wherein the first designated distance and the second designated distance are different. 29. The rotor of claim 15, wherein the inertial torquer has a mass center located behind said spanwise axis. 30. An aircraft comprising: a frame; a rotor hub supported by the frame; and at least one rotor blade having: (A) an elongated body (a) having a root, a tip, a span from the root to the tip, and a spanwise axis extending between the root and the tip, (b) having a leading edge, a trailing edge, and a chordwise axis extending between the leading edge and the trailing edge, (c) being flexible in twist about the spanwise axis along at least some of the span, (d) having a twist distribution across the span when in a state of rest, and (e) attached at the root to the rotor hub which is operable (i) to spin the elongated body about an axis of rotation, said axis of rotation being transverse to the spanwise axis, and (ii) to variably set a hub incidence angle of the elongated body, said hub incidence angle being an angle between a plane normal to said axis of rotation and a root chordwise line, the root chordwise line being a chordwise line through the root of the elongated body; and (B) an inertial torquer attached to a station of the span of the elongated body, the inertial torquer: (a) having a moment of inertia and a principal axis of inertia, (b) including a first section and a second section positioned coaxially along said principal axis of inertia, (i) the first section having a first axis positioned along said principal axis of inertia, (ii) the second section having a second axis positioned along said principal axis of inertia, (c) including a first mass attached to the first section, and a second mass attached to the second section, (i) the first mass extending at a first designated distance from the spanwise axis of the elongated body, (ii) the second mass extending at a second designated distance from the spanwise axis of the elongated body, (iii) the first mass and the second mass extending from opposite surfaces of the elongated body, (d) positioned with said moment of inertia about said spanwise axis and with said principal axis of inertia angled relative to a station chordwise line, said station chordwise line being a chordwise line extending between the leading edge and the trailing edge of the elongated body at said station, (e) defining a first relative incidence angle, said first relative incidence angle being the angle between said station chordwise line and said first axis, (f) defining a second relative incidence angle, said second incidence angle being the angle between said station chordwise line and said second axis, (q) positioned such that said first relative incidence angle and said second relative incidence angle are each less than ninety degrees, and (h) configured such that (i) centrifugal effect on the inertial torquer twists the elongated body such that the incidence distribution across the span of the elongated body varies with the rotational speed of the rotor hub about said axis of rotation and varies with said hub incidence angle of the elongated body, and (ii) in at least one operating condition of the rotor hub, a torsional equilibrium of the incidence distribution is substantially stiffened by the centrifugal effect on the inertial torquer. 31. The aircraft of claim 30, which includes a plurality of the inertial torquers attached at radially spaced positions along the elongated body. 32. The aircraft of claim 31, wherein at least one of the first mass and the second mass is connected to the elongated body by at least one strut. 33. The aircraft of claim 30, wherein at least one of the first mass and the second mass of the inertial torquer is connected to the elongated body by at least one strut. 34. The aircraft of claim 30, wherein the rotor hub is capable of spinning the rotor blade about the spin axis at a first rotational speed and a second rotational speed, the first rotational speed being lower than the second rotational speed, the spanwise distribution of elongated body twist at the state of rest being configured to maximize the generation of thrust at the first rotational speed. 35. The aircraft of claim 30, said incidence distribution being variable, said variable incidence distribution varying with the spin rate and hub pitch of the elongated body so as to maximize thrust efficiency of the rotor. 36. The aircraft of claim 30, wherein the inertial torquer has a mass center located forward of said spanwise axis. 37. The aircraft of claim 30, wherein the inertial torquer has a streamlined configuration to minimize aerodynamic drag. 38. The aircraft of claim 30, wherein the torsional stiffness of the elongated body, the inertia of the inertial torquer, and the position of said spanwise axis relative to the aerodynamic center of the elongated body, are such that when installed and spinning, the lowest natural frequency of the elongated body when oscillating in torsion is faster than the spin frequency of the rotor. 39. The aircraft of claim 30, wherein the rotor hub is configured to vary said hub incidence angle of the elongated body cyclically once per rotor revolution. 40. The aircraft of claim 30, wherein the rotor hub variably sets the hub incidence angle of the elongated body in a collective or cyclical manner. 41. The aircraft of claim 30, wherein the rotor hub variably sets the hub incidence angle of the elongated body in both a collective and cyclical manner. 42. The aircraft of claim 30, wherein the masses of said first mass and said second mass are different. 43. The aircraft of claim 30, wherein the first designated distance and the second designated distance are different. 44. The aircraft of claim 30, wherein the inertial torquer has a mass center located behind said spanwise axis. 45. A windmill comprising: a frame; a rotor hub supported by the frame; and at least one rotor blade having: (A) an elongated body (a) having a root, a tip, a span from the root to the tip, and a spanwise axis extending between the root and the tip, (b) having a leading edge, a trailing edge, and a chordwise axis extending between the leading edge and the trailing edge, (c) being flexible in twist about the spanwise axis along at least some of the span, (d) having a twist distribution across the span when in a state of rest, and (e) attached at the root to the rotor hub which is operable (i) to spin the elongated body about an axis of rotation, said axis of rotation being transverse to the spanwise axis, and (ii) to variably set a hub incidence angle of the elongated body, said hub incidence angle being the angle between a plane normal to said axis of rotation and a root chordwise line, the root chordwise line being a chordwise line through said root of the elongated body; and (B) an inertial torquer attached to a station of the span of the elongated body, the inertial torquer: (a) having a moment of inertia and a principal axis of inertia, (b) including a first section and a second section positioned coaxially along said principal axis of inertia, (i) the first section having a first axis positioned along said principal axis of inertia, (ii) the second section having a second axis positioned along said principal axis of inertia, (c) including a first mass attached to the first section, and a second mass attached to the second section, (i) the first mass extending at a first designated distance from the spanwise axis of the elongated body, (ii) the second mass extending at a second designated distance from the spanwise axis of the elongated body, (iii) the first mass and the second mass extending from opposite surfaces of the elongated body, (d) positioned with said moment of inertia about said spanwise axis and with said principal axis of inertia angled relative to a station chordwise line, said station chordwise line being a chordwise line extending between the leading edge and the trailing edge of the elongated body at said station, (e) defining a first relative incidence angle, said first relative incidence angle being the angle between said station chordwise line and said first axis, (f) defining a second relative incidence angle, said second relative incidence angle being the angle between said station chordwise line and said second axis, (q) positioned such that said first relative incidence angle and said second relative incidence angle are each less than ninety degrees, and (h) configured such that (i) the centrifugal effect on the inertial torquer twists the elongated body such that the incidence distribution across the span of the elongated body varies with the rotational speed of the rotor hub about said axis of rotation and varies with the hub incidence angle of the elongated body, and (ii) in at least one operating condition of the rotor hub, a torsional equilibrium of the incidence distribution is substantially stiffened by the centrifugal effect on the inertial torquer. 46. The windmill of claim 45, which includes a plurality of the inertial torquers attached at radially spaced positions along the elongated body. 47. The windmill of claim 46, wherein at least one of the first mass and the second mass is connected to the elongated body by at least one strut. 48. The windmill of claim 45, wherein at least one of the first mass and the second mass of the inertial torquer is connected to the elongated body by at least one strut. 49. The windmill of claim 45, wherein the rotor hub is capable of spinning the rotor blade about the spin axis at a first rotational speed and a second rotational speed, the first rotational speed being lower than the second rotational speed, the spanwise distribution of elongated body twist at the state of rest being configured to maximize generation of thrust at the first rotational speed. 50. The windmill of claim 45, said incidence distribution being variable, said variable incidence distribution varying with the spin rate and hub pitch of the elongated body so as to maximize thrust efficiency of the rotor. 51. The windmill of claim 45, wherein the inertial torquer has a mass center located forward of said spanwise axis. 52. The windmill of claim 45, wherein the inertial torquer has a streamlined configuration to minimize aerodynamic drag. 53. The windmill of claim 45, wherein the torsional stiffness of the elongated body, the inertia of the inertial torquer, and the position of said spanwise axis relative to the aerodynamic center of the elongated body, are such that when installed and spinning, the lowest natural frequency of the elongated body when oscillating in torsion is faster than the spin frequency of the rotor. 54. The windmill of claim 45, wherein the rotor hub is configured to vary said hub incidence angle of the elongated body cyclically once per rotor revolution. 55. The windmill of claim 45, wherein the rotor hub variably sets the hub incidence angle of the elongated body in a collective or cyclical manner. 56. The windmill of claim 45, wherein the rotor hub variably sets the hub incidence angle of the elongated body in both a collective and cyclical manner. 57. The windmill of claim 45, wherein the masses of said first mass and said second mass are different. 58. The windmill of claim 45, wherein the first designated distance and the second designated distance are different. 59. The windmill of claim 45, wherein the inertial torquer has a mass center located behind said spanwise axis.