Two-sweep rotary wing blade with limited taper ratio
View Patent ↗A rotary wing blade of limited taper ratio, comprising in succession along a reference radius: an inner zone; a forward-swept zone; and a back-swept zone. In addition, the beginning of the forward-swept zone lies in the range 0.47 to 0.65 times the reference radius R of the rotary wing. Furthermore, the leading edge of the blade at the reference radius presents an angle γ lying in the range −40° and −65° relative to the general axis of the blade.
1. A blade for a rotary wing which comprises in succession along a reference radius R: an inner zone; a forward-swept zone; and a back-swept zone; wherein the beginning of said forward-swept zone lies in the range 0.47 to 0.65 times said reference radius R, and wherein the leading edge of said blade at said reference radius R presents an angle γ lying in the range −40° to −60° relative to a general axis of said blade, wherein a taper ratio of said backswept zone lies in the range 1 to 2.
2. A blade according to claim 1 , wherein the beginning of said back-swept zone lies in the range 0.75 to 0.90 times said reference radius R.
3. A blade according to claim 1 , wherein said forwards-swept zone presents a sweep angle lying in the range 50° to 10°.
4. A blade according to claim 1 , wherein said back-swept zone presents a sweep angle lying in the range −15° to −30°.
5. A blade according to claim 1 , wherein said back-swept zone presents a chord that is constant and equal to the chord of the outermost section of said forward-swept zone.
6. A blade according to claim 1 , further comprising an outer zone following said back-swept zone, said outermost zone presenting a taper ratio.
7. A blade according to claim 6 , wherein the beginning of said outer zone lies in the range 0.92 to 0.97 times said reference radius R.
8. A blade according to claim 6 , including at least one section presenting a thickness profile lying in the range 6% to 8%, said section being included in said outer zone.
9. A blade according to claim 1 , including a dihedral-forming slope M at its outer tip.
10. A blade according to claim 9 , wherein the angle of inclination 5 of said slope at said reference radius lies in the range 100 to 200.
11. A blade according to claim 1 , wherein the beginning of said inner zone lies in the range 0.15 to 0.30 times said reference radius R.
12. A blade according to claim 1 , wherein said reference radius lies in the range 5.0 m to 10.0 m.
13. A blade according to claim 1 , including at least one segment having a thickness profile lying in the range 8% to 10%, said segment being situated at more than 75% of said reference radius R.
14. A blade according to claim 13 , wherein said segment includes at least one section of thickness equal to 9%.
15. A blade according to claim 1 , wherein said inner zone presents a chord that is constant.
16. A blade according to claim 15 , wherein the chord of said inner zone lies in the range L to 1.1 times L, where L is given by:
L
=
∫
R0
R
L
(
r
)
r
2
ⅆ
r
∫
R0
R
r
2
ⅆ
r
L(r) being the relationship defining how the chord varies along the span, RO being the radius at the beginning of the profiled portion, and R being the reference radius.
17. A blade for a rotary wing which comprises in succession along a reference radius R: an inner zone; a forward-swept zone; and a back-swept zone; the beginning of said forward-swept zone lying in the range 0.47 to 0.65 times said reference radius R, wherein the leading edge of said blade at said reference radius R presents an angle γ lying in the range −40° to −60° relative to a general axis of said blade and wherein said back-swept zone presents a chord that is constant and equal to the chord of the outermost section of said forward-swept zone.
18. A blade for a rotary wing which comprises in succession along a reference radius R: an inner zone; a forward-swept zone; and a back-swept zone; the beginning of said forward-swept zone lying in the range 0.47 to 0.65 times said reference radius R, wherein the leading edge of said blade at said reference radius R presents an angle γ lying in the range −40° to −60° relative to a general axis of said blade and wherein the chord of said inner zone lies in the range L to 1.1 times L, where L is given by:
L
=
∫
R0
R
L
(
r
)
r
2
ⅆ
r
∫
R0
R
r
2
ⅆ
r
L(r) being the relationship defining how the chord varies along the span, R0 being the radius at the beginning of the profiled portion, and R being the reference radius.
19. A blade for a rotary wing which comprises in succession along a reference radius R: an inner zone; a forward-swept zone; and a back-swept zone; wherein the beginning of said forward-swept zone lies in the range 0.47 to 0.65 times said reference radius R, and wherein the leading edge of said blade at said reference radius R presents an angle γ lying in the range −40° to '60° relative to a general axis of said blade, wherein a taper ratio of said backswept zone lies in the range 1 to 2, and wherein said forwardswept zone presents a chord that is constant.
20. A blade according to claim 19 , wherein said chord of said forward-swept zone is equal to the chord of said inner zone.