Upload
docong
View
218
Download
0
Embed Size (px)
Citation preview
Helicopters / Filipe Szolnoky CunhaSlide 1Rotor hubs
• Helicopter blades are attached to the rotor shaft with aseries of hinges:– Flapping hinges (or a soft flex-beam) , that allow blades to
freely flap up or down. This ensures that lift is transferred to theshaft, but not the moments.
– Lead-Lag Hinges. When the blades rotate, and flap, Coriolisforces are created in the plane of the rotor. In order to avoidunwanted stresses at the blade root, lead-lag hinges are used.
– Pitch bearing/pitch-link/swash plate: Used to control the bladepitch.
• The blade loads are affected by the motion of the bladesabout these hinges.
• From an aerodynamic perspective, lead-lag motion can beneglected. Pitching and flapping motions must beincluded.
Introduction
Helicopters / Filipe Szolnoky CunhaSlide 2Rotor hubs
Blade movement
Helicopters / Filipe Szolnoky CunhaSlide 3Rotor hubs
Rotor Hub Types
Boeing AH-64 Apache rotor hub: Fully articulated
Helicopters / Filipe Szolnoky CunhaSlide 4Rotor hubs
Rotor Hub Types
Kamov Ka-29TB Helix: Fully articulated
Helicopters / Filipe Szolnoky CunhaSlide 5Rotor hubs
Fully Articulated Rotor Hub
• Hinges allow the flap and lag movement
• Bearing allow the feathering movement
• Mechanical dampers added to the lag hinge
• Complicated to design and maintain
• Heavy and produces high drag in forward flight
Helicopters / Filipe Szolnoky CunhaSlide 6Rotor hubs
Rotor Hub Types
Bell UH-1D Teetering
Helicopters / Filipe Szolnoky CunhaSlide 7Rotor hubs
Rotor Hub Types
Bell UH-1D Teetering
Helicopters / Filipe Szolnoky CunhaSlide 8Rotor hubs
Rotor Hub Types
Robinson R-22 Teetering
Helicopters / Filipe Szolnoky CunhaSlide 9Rotor hubs
Rotor Hub Types
Robinson R-22 Teetering
Helicopters / Filipe Szolnoky CunhaSlide 10Rotor hubs
Rotor Hub Types
Bell V-22 Osprey 3 blades teetering rotor
Helicopters / Filipe Szolnoky CunhaSlide 11Rotor hubs
Teetering Hub
• No independent flap or lag hinge
• Independent feathering bearing
• Mechanically simple
• High parasitic drag in forward flight
• Variation is the underslung teetering hub
Helicopters / Filipe Szolnoky CunhaSlide 12Rotor hubs
Rotor Hub Types
Westland Lynx: Hingeless
Helicopters / Filipe Szolnoky CunhaSlide 13Rotor hubs
Rotor Hub Types
Westland Lynx: Hingeless
Helicopters / Filipe Szolnoky CunhaSlide 14Rotor hubs
Rotor Hub Types
Eurocopter Bo105M: Hingeless
Helicopters / Filipe Szolnoky CunhaSlide 15Rotor hubs
Hingeless Hub
• No flap or lead hinge
• Blade motion are performed by flexure
• Coupling between the flap and lag motion
• Mechanically simple
• Complicated design
• Low drag in forward flight
• Good manoeuvring capabilities
Helicopters / Filipe Szolnoky CunhaSlide 16Rotor hubs
Rotor Hub Types
Eurocopter AS355 TwinStar : Bearingless
Helicopters / Filipe Szolnoky CunhaSlide 17Rotor hubs
Rotor Hub Types
Helicopters / Filipe Szolnoky CunhaSlide 18Rotor hubs
Bearingless Hub
• No flap or lead hinge
• No feathering bearing
• Motion obtained by bending, flexing and twisting
• Coupling between the all motion
• Mechanically very simple
• Very complicated design
• Low drag in forward flight
Helicopters / Filipe Szolnoky CunhaSlide 19Rotor hubs
Swash Plate
Helicopters / Filipe Szolnoky CunhaSlide 20Rotor hubs
Pitch Control
Helicopters / Filipe Szolnoky CunhaSlide 21Rotor hubs
Controls
• Collective control: Lever (left side)
– Increases (decreases) the same amount of pitch
angle independently of the azimuth angle.
Helicopters / Filipe Szolnoky CunhaSlide 22Rotor hubs
Controls
Helicopters / Filipe Szolnoky CunhaSlide 23Rotor hubs
Pitch Control
Helicopters / Filipe Szolnoky CunhaSlide 24Rotor hubs
Controls
• Cyclic control: Lever
– Changes the pitch angle with the azimuth
position (changes the rotor orientation in space)
Helicopters / Filipe Szolnoky CunhaSlide 25Rotor hubs
Pitch Control
Helicopters / Filipe Szolnoky CunhaSlide 26Rotor hubs
Collective control
Helicopters / Filipe Szolnoky CunhaSlide 27Rotor hubs
Control
Helicopters / Filipe Szolnoky CunhaSlide 28Rotor hubs
Flap motion
Helicopters / Filipe Szolnoky CunhaSlide 29Rotor hubs
Flap motion
• Zero offset
hub
Helicopters / Filipe Szolnoky CunhaSlide 30Rotor hubs
Lead-Lag Motion
Helicopters / Filipe Szolnoky CunhaSlide 31Rotor hubs
Lead-Lag Motion
Helicopters / Filipe Szolnoky CunhaSlide 32Rotor hubs
Lead-Lag Motion
• Shifting the rotor
CM with out of
pattern blades.
Helicopters / Filipe Szolnoky CunhaSlide 33Rotor hubs
Order of hinges
• The order on which the flapping, dragging and
feathering hinges are disposed is subjected to a
certain amount of variation.
• The use of coincident flapping and dragging
hinges is common because is allows a compact
bearing assembly. Feathering bearing is normally
positioned after this hinge
• But the three hinges are not necessarily orthogonal
Helicopters / Filipe Szolnoky CunhaSlide 34Rotor hubs
Order of hinges
Flapping axisDragging axis
Feathering axis
Helicopters / Filipe Szolnoky CunhaSlide 35Rotor hubs
Order of hinges
• Flapping
Hinge
• Coupling
between
flapping and
feathering
Helicopters / Filipe Szolnoky CunhaSlide 36Rotor hubs
Order of hinges
• Coupling between flapping and feathering
Helicopters / Filipe Szolnoky CunhaSlide 37Rotor hubs
Order of hinges
Helicopters / Filipe Szolnoky CunhaSlide 38Rotor hubs
Order of hinges
• No Coupling between flapping and feathering
Helicopters / Filipe Szolnoky CunhaSlide 39Rotor hubs
Order of hinges
• Flapping
Hinge
• Coupling
between
Flapping and
Dragging
Helicopters / Filipe Szolnoky CunhaSlide 40Rotor hubs
Order of hinges
• In a general case:
• Flapping Hinge
• δ3≠0
– Flapping and Feathering
• δ1≠0
– Flapping and Dragging
Helicopters / Filipe Szolnoky CunhaSlide 41Rotor hubs
Order of hinges
• In a general case:
• Dragging Hinge
• α3≠0
– Dragging and Feathering
• α1≠0
– Dragging and Flapping