Variable camber and stagger airfoil and method
Aerodynamically efficient air flow management in axial flow-turbines is provided by utilizing a variable stagger and camber airfoil. In an exemplary embodiment of the invention, this is accomplished by providing a two-piece airfoil including a strut and a flap, each of which is mounted to articulate about a common, radially oriented axis. The strut and flap are respectively positioned by a strut gear and a flap gear, located at the radial end of the airfoil and, in an exemplary embodiment, are driven by a stepped synchronizing ring.
1. A compressor stator vane for a gas turbine engine comprising:
a leading edge part and a trailing edge part, each said part having a shaft-like portion extending through an outer diameter case wall of said gas turbine compressor, said leading edge part and said trailing edge part being mounted to articulate about a common, radially, oriented axis;
a strut gear for selectively varying an angle of said leading edge part with respect to an inlet air flow vector by rotating said leading edge part with respect to said axis of rotation; and
a flap gear for selectively rotating said trailing edge part about said axis of rotation to vary an angle of said trailing edge part with respect to said air flow vector.
2. A compressor stator vane as in claim 1 , wherein said flap gear and said strut gear have different radiuses thereby to determine a stagger to camber geometric relationship.
3. A compressor stator vane as in claim 2 , further comprising a stepped, synchronous ring for being driven to position said leading edge and trailing edge parts via said respective gears.
4. A compressor stator vane as in claim 3 , wherein the flap angle is determined from the stepped synchronous ring motion as follows:
Θ
Flap
=
D
Sync
360
2
Π
R
Flap
where R Flap is the radius of the flap gear and D Sync is the arc length of the circular movement of the stepped synchronous ring.
5. A compressor stator vane as in claim 3 , wherein the strut angle is determined from the stepped synchronous ring motion as follows:
Θ
Strut
=
D
Sync
360
2
Π
R
Strut
where R Strut is the radius of the strut gear and D Sync is the arc length of the circular movement of the stepped synchronous ring.
6. A compressor stator vane as in claim 1 , wherein the stagger angle is determined as follows:
Θ
Stagger
=
tan
-
1
[
Y
b
-
Y
a
X
b
-
X
a
]
,
where X a ,Y a is the coordinate of the tip of the leading edge part, and where X b ,Y b is the coordinate of the tip of the trailing edge part.
7. A compressor stator vane as in claim 1 , wherein the camber angle is determined as follows:
Θ
Camber
=
sin
-
1
[
X
b
Y
a
-
Y
b
X
a
C
Flap
C
Strut
]
,
where X a ,Y a is the coordinate of the tip of the leading edge part, where X b ,Y b is the coordinate of the tip of the trailing edge part, C Flap is the length of the trailing edge part and C Strut is the length of the leading edge part.
8. A compressor stator vane as in claim 1 , wherein the shaft-like portion of the leading edge part is fitted within the shaft-like portion of the trailing edge part.
9. A method for changing stagger angle and camber angle of a compressor stator vane, comprising:
providing an airfoil including:
a leading edge part and a trailing edge part, each said part having a shaft-like portion extending through an outer diameter case wall of said gas turbine compressor, said leading edge part and said trailing edge part being mounted to articulate about a common, radially, oriented axis;
a strut gear for selectively varying an angle of said leading edge part with respect to an inlet air flow vector by rotating said leading edge part with respect to said axis of rotation; and
a flap gear for selectively rotating said trailing edge part about said axis of rotation to vary an angle of said trailing edge part with respect to said air flow vector;
the method comprising driving said strut gear and said flap gear to determine a stagger angle and a camber angle of said airfoil.
10. A method as in claim 9 , wherein said flap gear and said strut gear have different radii thereby to determine a stagger to camber geometric relationship.
11. A method as in claim 10 , further comprising a stepped, synchronous ring for being driven to position said leading edge and trailing edge parts via said respective gears.
12. A method as in claim 11 , wherein the flap angle is determined from the stepped synchronous ring motion as follows:
Θ
Flap
=
D
Sync
360
2
Π
R
Flap
where R Flap is the radius of the flap gear and D Sync is the arc length of the circular movement of the stepped synchronous ring.
13. A method as in claim 11 , wherein the strut angle is determined from the stepped synchronous ring motion as follows:
Θ
Strut
=
D
Sync
360
2
Π
R
Strut
where R Strut is the radius of the strut gear and D Sync is the arc length of the circular movement of the stepped synchronous ring.
14. A method as in claim 9 , wherein the stagger angle is determined as follows:
Θ
Stagger
=
tan
-
1
[
Y
b
-
Y
a
X
b
-
X
a
]
,
where X a ,Y a is the coordinate of the tip of the leading edge part, and where X b ,Y b is the coordinate of the tip of the trailing edge part.
15. A method as in claim 9 , wherein the camber angle is determined as follows:
Θ
Camber
=
sin
-
1
[
X
b
Y
a
-
Y
b
X
a
C
Flap
C
Strut
]
,
where X a ,Y a is the coordinate of the tip of the leading edge part, where X b ,Y b is the coordinate of the tip of the trailing edge part, C Flap is the length of the trailing edge part and C Strut is the length of the leading edge part.
16. A method as in claim 9 , wherein the shaft-like portion of the leading edge part is fitted within the shaft-like portion of the trailing edge part.