Rotor blade twist distribution for a high speed rotary-wing aircraft
원문보기
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
B64C-027/46
B64C-027/32
출원번호
UP-0508414
(2006-08-23)
등록번호
US-7600976
(2009-10-28)
발명자
/ 주소
Bagai, Ashish
Kreuscher, Lauren
출원인 / 주소
Sikorsky Aircraft Corporation
대리인 / 주소
Carlson Gaskey & Olds
인용정보
피인용 횟수 :
3인용 특허 :
12
초록▼
Main rotor blades of the dual, counter-rotating, rigid coaxial rotor system exhibit a unique unconventional combination of positive and negative twist gradients in which the rotor system rotor Figure of Merit (hover efficiency) is improved by providing a dissimilar twist distribution between the low
Main rotor blades of the dual, counter-rotating, rigid coaxial rotor system exhibit a unique unconventional combination of positive and negative twist gradients in which the rotor system rotor Figure of Merit (hover efficiency) is improved by providing a dissimilar twist distribution between the lower rotor blade and the upper rotor blades. This improvement is specifically a result of reduced profile drag of the lower rotor system, achieved by driving the effective operating condition of the lower rotor blades to be similar to the upper rotor blade such that the tip drag losses of the lower main rotor have been reduced considerably using a mathematically vigorous approach. While minimal induced power consumption resulted due to the dissimilar lower main rotor twist, a significant profile power benefit is realized, resulting in the improved hover efficiency with essentially no reduction in rotor forward flight performance.
대표청구항▼
What is claimed is: 1. A main rotor blade assembly for a rotary wing aircraft comprising: a main rotor blade root region containing a root region twist within said main rotor blade root region transverse to a feathering axis, said root region twist having a positive twist gradient; a main rotor bla
What is claimed is: 1. A main rotor blade assembly for a rotary wing aircraft comprising: a main rotor blade root region containing a root region twist within said main rotor blade root region transverse to a feathering axis, said root region twist having a positive twist gradient; a main rotor blade inboard region outboard of said main rotor blade root region, said main rotor blade inboard region containing an inboard chord within said main rotor blade inboard region transverse to said feathering axis; a main rotor blade main region outboard of said main rotor blade inboard region, said main rotor blade main region containing a main region twist within said main rotor blade main region transverse to said feathering axis, said main region twist having a negative twist gradient; a main rotor blade tip region outboard of said main region, said tip, region containing a tip region twist within said main rotor blade tip region transverse to said feathering axis, said tip region twist having a negative twist gradient more negative than said main region twist gradient; and a blade chord defined between a leading edge and a trailing edge, said trailing edge defined along a root trailing edge of said main rotor blade root region, an inboard region trailing edge of said main rotor blade inboard region, a main region trailing edge of said main rotor blade main region and a tip region trailing edge of said main rotor blade tip region, said inboard region trailing edge defining a point A and a point B, said point B outboard of said point A, said main region trailing edge defining a point C and a point D, said point D outboard of said point C, said blade chord increasing between said point A and said point B and decreasing between said point C and said point D, said main rotor blade maximum chord located between said point B and said point C from said root attachment section to said main region section and decreasing from said main region section to said tip region section. 2. The main rotor blade assembly as recited in claim 1, wherein said root region twist gradient is greater than approximately 14 degrees/x (r/R). 3. The main rotor blade assembly as recited in claim 2, wherein said root region twist gradient transitions to said main region twist gradient at approximately 0.4x (r/R). 4. The main rotor blade assembly as recited in claim 1, wherein said root region twist gradient transitions to said main region twist gradient between 0.3x and 0.5x (r/R). 5. The main rotor blade assembly as recited in claim 1, wherein said main region twist gradient is between-14 and 0 degrees/x. 6. The main rotor blade assembly as recited in claim 5, wherein said main region twist gradient transitions to said tip region twist gradient at 0.865x (r/R). 7. The main rotor blade assembly as recited in claim 1, wherein said main region twist gradient transitions to said tip region twist gradient at above 0.8x (r/R). 8. The main rotor blade assembly as recited in claim 1, wherein said tip region twist gradient is less than-35 degrees/x (r/R). 9. The main rotor blade assembly as recited in claim 1, wherein a 0 degree twist occurs at approximately 0.20x and 0.75x (r/R). 10. The main rotor blade assembly as recited in claim 1, wherein said main region chord defines a maximum chord of said blade chord. 11. A dual, counter-rotating, coaxial rotor system comprising: an upper main rotor blade having an upper main rotor blade positive twist gradient which transitions to an upper main rotor blade negative twist gradient between 0.3 and 0.5 x (r/R); and a lower main rotor blade having a lower main rotor blade positive twist gradient which transitions to a first lower main rotor blade negative twist gradient between 0.3 and 0.5 x (r/R) which then transitions to a second lower main rotor blade twist gradient above 0.8 x (r/R) more negative than the first lower main rotor blade negative twist gradient, said upper main rotor blade and said lower main rotor blade each define a blade chord defined between a leading edge and a trailing edge, said trailing edge defined along a root trailing edge of a main rotor blade root region, an inboard region trailing edge of a main rotor blade inboard region outboard of said root trailing edge, a main region trailing edge of a main rotor blade main region outboard of said inboard region trailing edge, and a tip region trailing edge of a main rotor blade tip region outboard of said mm region trailing edge, said inboard region trailing edge defining a point A and a point B, said point B outboard of said point A, said main region trailing edge defining a point C and a point D, said point D outboard of said point C, said blade chord increasing between said point A and said point B and decreasing between said point C and said point D, said main rotor blade maximum chord located between said point B and said point C from said root attachment section to said main region section and decreasing from said main region section to said tip region section. 12. The system as recited in claim 11, wherein said upper main rotor blade negative twist gradient is generally equivalent to said first lower main rotor blade negative twist gradient over a main section. 13. The system as recited in claim 11, wherein said upper main rotor blade positive twist gradient is less than said lower main rotor positive twist gradient over an inboard section. 14. The system as recited in claim 11, wherein said upper main rotor blade positive twist gradient transitions to said upper main rotor blade negative twist gradient and said lower main rotor blade positive twist gradient transitions to said first lower main rotor blade negative twist gradient at a generally equivalent x (r/R). 15. A method of increasing a hover efficiency of a dual, counter-rotating, coaxial rotor system comprising: providing a dissimilar twist on a lower rotor blade relative to an upper rotor blade to change an operational angle of attack of a lower rotor blade tip section relative an operational angle of attack of an upper rotor blade tip section to reduce profile drag and profile power requirements, the upper main rotor blade and the lower main rotor blade each define a blade chord defined between a leading edge and a trailing edge, said trailing edge defined along a root trailing edge of a main rotor blade root region, an inboard region trailing edge of a main rotor blade inboard region outboard of said root trailing edge, a main region trailing edge of a main rotor blade main region outboard of said inboard region trailing edge, and a tip region trailing edge of a main rotor blade tip region outboard of said mm region trailing edge, said inboard region trailing edge defining a point A and a point B, said point B outboard of said point A, said main region trailing edge defining a point C and a point D, said point D outboard of said point C, said blade chord increasing between said point A and said point B and decreasing between said point C and said point D, said main rotor blade maximum chord located between said point B and said point C from said root attachment section to said main region section and decreasing from said main region section to said tip region section. 16. A method as recited in claim 15, further comprising: driving the operational angle of attack of the lower rotor blade tip section to be generally equivalent to the upper rotor blade tip section. 17. A method as recited in claim 15, further comprising: matching an effective angle of attack across a section of the lower rotor blade to be generally equivalent to an effective angle of attack across a section of the upper rotor blade. 18. A method as recited in claim 15, further comprising: providing the dissimilar twist within a tip section of the lower rotor blade. 19. A method as recited in claim 15, further comprising: providing the dissimilar twist on a root section of the lower rotor blade. 20. A method as recited in claim 15, further comprising: determining the dissimilar twist on the lower rotor blades operating in the non-uniform downwash induced by the upper rotor blades in hover to ensure that the lower rotor blades are operating at essentially the same effective angle of attack as the upper rotor blades. 21. A method as recited in claim 15, further comprising: determining the dissimilar twist on the lower rotor blade relative the upper rotor blade such that a negative twist gradient is given by the equation: [θtw]LR=[θ0 +θtw+αi]UR-[θ0 +αi]LR Where, UR is "Upper Rotor," LR is "Lower Rotor,"-θ0 is the specified rotor collective angle, θtw is the blade sectional twist angle, and αi is the sectional induced downwash angle of attack. 22. A method as recited in claim 15, further comprising: matching an effective angle of attack across the tip section of the lower rotor blade to be generally equivalent to an effective angle of attack across the tip section of the upper rotor blade. 23. A method as recited in claim 22, further comprising: locating a 0 degree twist at approximately 0.20x and 0.75x (r/R). 24. A method as recited in claim 15, further comprising: matching an effective angle of attack across a main section of the lower rotor blade to be generally equivalent to an effective angle of attack across a main section of the upper rotor blade. 25. A method as recited in claim 15, further comprising: matching an effective angle of attack across a root section of the lower rotor blade to be generally equivalent to an effective angle of attack across a root section of the upper rotor blade.
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이 특허에 인용된 특허 (12)
Flemming ; Jr. Robert J. (Trumbull CT) Rosen Kenneth M. (Guilford CT) Sheehy Thomas W. (Hamden CT), Ancillary aerodynamic structures for an unmanned aerial vehicle having ducted, coaxial counter-rotating rotors.
Vuillet Alain E. (Bouc Belair FRX) Philippe Jean J. (Versailles FRX) Desopper Andr (Garches FRX), Blade with curved end for a rotary airfoil of an aircraft.
Splettstoesser Wolf R.,DEX ; Van De Wall Berend,DEX ; Delrieux Yves,FRX ; Gardarein Patrick,FRX, Blade with reduced sound signature, for aircraft rotating aerofoil, and rotating aerofoil comprising such a blade.
Cycon James P. (Orange CT) Kohlhepp Fred W. (Hamden CT) Millea Vincent F. (Stratford CT), Coaxial transmission/center hub subassembly for a rotor assembly having ducted, coaxial counter-rotating rotors.
Krauss Timothy A. (Harwinton CT) Hunter David H. (Cheshire CT) Beatty Robert D. (Trumbull CT), Rotor blade subassembly for a rotor assembly having ducted, coaxial counter-rotating rotors.
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