a presentation about aircraft propeller.ppt

about propeller

1. PROPELLER SYSTEM
1
st
-Look at how lift is generated
Then see how it applies to propellers

2. How lift is generated
PROPELLER SYSTEM

3. In this example
Pressure Remains Constant here
Pressure Decreases here
In this direction
The result is
LIFT
How lift is generated
PROPELLER SYSTEM

4. Small Pressure Increase here
Greater Pressure Decrease
here
The result is
MORE LIFT
How lift is increased
PROPELLER SYSTEM

5. Direction of travel
The difference in direction of traveland aerofoil inclineis called:-
The ANGLE of ATTACK
How lift is increased
PROPELLER SYSTEM

6. How does lift apply toPROPELLORS?
On Propellers, LIFT is called THRUST
And propeller Blades work the same way as aircraft wings
When a propeller spins and the aircraft moves forward, the tips of the
propeller blades move in a ‘corkscrew’ path
This path is called a HELIX
PROPELLER SYSTEM

7. How the HELIX ANGLEis generated

8. How the blade tip travel produces the HELIX ANGLE
PROPELLER SYSTEM

9. How the blade tip travel produces the HELIX ANGLE
PROPELLER SYSTEM

10. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

11. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

12. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

13. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

14. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

15. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

16. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

17. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

18. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

19. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

20. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

21. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

22. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

23. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

24. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

25. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

26. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

27. PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

28. How the blade tip travel produces the HELIX ANGLE
PROPELLER SYSTEM
Forward Speed -Distance Travelled
over One Minute
Rotation -
Number of
Rotations
per Minute

29. Forward Speed
RPM
How the blade tip travel produces the HELIX ANGLE
PROPELLER SYSTEM

30. PROPELLER SYSTEM
Forward Speed
RPM
How the blade tip travel produces the HELIX ANGLE

31. Forward Speed
RPM
PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

32. Forward Speed
RPM
PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

33. Forward Speed
RPM
PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

34. Forward Speed
RPM
PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

35. Forward Speed
RPM
PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

36. How the HELIX ANGLEis changed by engine rpm and forward speed

37. Forward Speed
RPM
How an increase in RPM changes the Helix Angle
Changes in FORWARD SPEED and RPMwill change
the Helix Angle
Faster
RPM
PROPELLER SYSTEM
How the blade tip travel produces the HELIX ANGLE

38. Forward Speed
RPMRPM
Faster Forward Speed
Changes in FORWARD SPEED and RPMwill change
the Helix Angle
How an increase in FORWARD SPEED changes the HELIX ANGLE
PROPELLER SYSTEM

39. Let’s take a closer look at the blade aerofoil and the
Helix Angle and thrust (lift) generation
If the Helix Angle changes,
then we need to change the
blade angle.
Remember (from the comparison with the aircraft wing), the optimum
Angle of Attack is required to maintain most efficient thrust generation.
This is the Helix Angle
This is the
Angle of
Attack
Direction of
rotation
Direction of blade through
the air with forward speed
PROPELLER SYSTEM

40. Mechanical STOPS and blade angles

41. All propeller blades are actuated by the same mechanical linkage
PROPELLER SYSTEM
Sliding Piston
Hard Stops
Fine
Pitch
Coarse
Pitch
Direction
of
Rotation
Direction
of Flight
Propeller
Blade
Actuating
Lever
Actuating
Link

42. Note: -blade angle is relative to piston travel
Fine pitch
Coarse pitch
Or
‘Feathered’
Pistontravels between ‘hard’ stops
Direction
Of
Rotation
Maximum resistance
to rotation
Minimum
resistance
to forward
speed
Minimum
resistance to
rotation
Maximum
resistance
to forward
speed
The blade angle changes through 90deg
with piston travel
At this hard stop
the blade is in
this position
At this hard stop
the blade is in
this position
PROPELLER SYSTEM

43. Easier Starting of engine
Direction of travel
Direction of
Rotation
Good for:-
Running engine with no/minimal thrust
Bad for:-
In-flight –loss of control
High drag –braking effect on ground
Zero pitch –or Ground Fine Pitch
In-flight engine failure –loss of control and
engine disintegration
PROPELLER SYSTEM
Importance of set blade angle
Fine pitch
Minimum
resistance to
rotation
Maximum
resistance
to forward
speed

44. Maximum resistance
to rotation
Minimum
resistance
to forward
speed
Starting of engine
Direction of travel
Direction of
Rotation
Bad for:-
Could cause engine burn-out if running
Low drag –NO braking effect on ground
Maximum pitch –or Feathered
Good for:-
In-flight –loss of control
In-flight engine failure –control maintained
and engine stops
rotating minimizing
damage
PROPELLER SYSTEM
Importance of set blade angle

45. Minimal
resistance to
rotation
Air pushed
forward giving
reverse thrust
Direction of travel
Direction of
Rotation
Used for:-
Bad for:-
In-flight –loss of forward speed, aircraft stalls
High drag –high braking effect on ground
Reverse Pitch
In-flight engine failure –loss of control and
reverse rotation
increasing
engine disintegration
Usually for military
aircraft only
PROPELLER SYSTEM
Importance of set blade angle

46. Direction of travel
Direction of
Rotation
Used for:-
Low drag on final approach
Flight Fine and Cruise Pitch
Used for:-
In-flight descent –faster forward speed than
final approach
Flight
Fine
pitch
Cruise
pitch
Both give minimal drag at
low power settings
PROPELLER SYSTEM
Importance of set blade angle

47. Blade Twist

48. DISTANCE TRAVELLED BY
ROOT, MID-SPAN AND TIP
THICK FOR
STRENGTH
PROPELLER SYSTEM
Blade Twist
ROOT
MID-SPAN
TIP
THINNER FOR
STRENGTH AND
THRUST
THIN FOR
THRUST
COARSE
ANGLE
MEDIUM
ANGLE
FINE
ANGLE
BLADE ANGLE RELATIVE TO DISTANCE (AND THEREFORE SPEED)
TRAVELLED BY ROOT, MID -SPAN AND TIP
Typical Blade
Typical 3
Blade Prop