SLAT FOR WIND ENERGY CONVERTOR

ENTRE-DEUX D'AUBES POUR EOLIENNE

English Abstract

SLAT FOR WIND ENERGY CONVERTOR

ABSTRACT OF THE DISCLOSURE




The disclosure describes a wind energy convertor
with improved efficiency comprising a common axle, a
plurality of vanes adapted to rotate about the common
axle, the vanes being spaced from the axle, each vane
having a symmetrical airfoil cross-section. A symmetri-
cal slat is spacedly mounted in front of the leading
edge of each vane, thus forming an air passage between
the airfoil and the slat.

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Claims

The embodiments of the invention in which an
exclusive property or privilege is claimed are defined
as follows
1. A wind energy convertor comprising a common
axle, a plurality of vanes adapted to rotate about
said common axle, said vanes being spaced from said
axle, each vane having a symmetrical airfoil cross-
section, and a symmetrical slat spacedly mounted in
front of the leading edge of each vane, thus forming
an air passage between said airfoil and said slat.
2. A wind energy convertor according to claim 1,
wherein said slat has an outer surface approximately
the same form as the form of the leading edge of the air-
foil.

3. A wind energy convertor according to claim 2,
wherein the outer surface of said slat is spaced from
the leading edge by approximately half of the maximum
thickness of the airfoil when measured on center line
of the airfoil.

4. A wind energy convertor according to claims 1,
2 and 3, wherein the slat has an inner surface spaced
from the outer surface so that the area of the air
passage cross-sections do not change abruptly thus re-
ducing turbulence in the air-flow.

Description

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BACKGROUND OF INVENTION
ta) Field of Invention
This invention relates to a slat for a
wind energy convertor. More specifically, the
invention relates to a wind energy convertor having a
main vertical axle, vane mounting members extending
radially from the main axle, vanes perpendicular to
the vane mounting members, and slats disposed in front
of the vanes to improve the efficiency of the wind
energy convertor.
(b) Description of Prior Art
In my Canadian application No. 281,008
filed June 21, 1977, I have described a wind energy
convertor which has a vertical axis of rotation and
a plurality of vanes spaced from the said axis and
rotating around it.
~lthough this system offers many advantages
as a reliable wind energy convertor, it would offer
further advantages if its efficiency could be improved.
On the other hand, slats are known in aviation
and are used to increase the ratio of lift coefficient
to drag coefficient. However, they were developed and
used exclusively on asymmetrical airfoils and were never
applied to wind turbines.

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SUMMARY OF INVENTION
It is an object of the invention to provide
a wind energy convertor with improved efficiency
It is an object of t~e present invention to
increase the amount of energy obtained with a wind
energy convertor by providing slats ahead of the leading
edge of the airfoil of the vanes.
It is yet another object of the present invention
to increase the torque and the power of a wind energy
convertor.
According to the present invention there is
provided a wind energy convertor comprising a common axle,
a plurality of vanes adapted to rotate about the common
axle, the vanes being spaced from the axle, each vane
having a symmetrical airfoil cross-section. A symmetrical
slat is spacedly mounted in front of the leading edge of
each vane, thus forming an air passage between the airfoil
and the slat.
In accordance with a preferred embodiment of
the invention, the outer contour of the slat is about
the same as the contour of the leading edge of the airfoil.
BRIEF DESCRIPTION OF DRA~qNGS
FIGURE 1 is a view of a symmetrical airfoil
provided with a symmetrical slat.
FIGURE 2 is a view of a wind energy con-
vertor wherein the vanes each have
a slat mounted in front of its leading
edge.
Referring to the drawings, it will be seen
that the vane 1 is the same as that described in my

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Canadian application ~o. 281,008. Of course other types of
of vanes could be used without depart ~rom the scope of
of the presènt invention. ~he vane is symmetrical, as
shown and the length of the cord of the vane is represent-
ed by A-s.
Turning now to the slat 3 which appears in
front of the leading edge 11 of the vane L it will be
seen that it is also symmetrical with respect to the
center line 7. B-C represents the distance between the
airfoil and the outer surface of the slat, measured along
the center line of the combination.
- The slat 3 is shaped as shown in the drawings
and has an outer face Sl which is convex so as to have
approximately the same form as the convex leading edge 11
of the vane 1. The inner face S2 of the slat 3 is concave,
as shown, but its radius of curvature is longer than the
radius of the outer face Sl. The inner face S2, shaped as
it is and spaced from outer face Sl is intended to decrease
too abrupt a change in an area of the air passage between
the airfoil and the slat. Also, the pointed ends 15 and 17

of the slat are in line with a tangent of outer face 11 of
the vane which passes at the center line of the vane 1.
The slat 3 is mounted on the vane 1 in any
manner known to those skilled in the art. In the embodi-

ment illustrated, a bolt 19 extends through the slat atthe center line 7 thereof and a spacer 21 keeps the lead-
ing edge 11 of the vane 1 and the inner surface S2 of
the slat 3 at a predetermined distance from one another.
A nut 23 holds the assembly together.

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It will also be noted that the outer ~ace Sl
of the slat is spaced from the leading edge by approxi-
mately half of the maximum thickness of the air~oil
when rneasured on the center line of the airfoil.
The ~unction of the slat is as follows.
When the wind creates a pressure on one side of
the vane 1, the airflow around the airfoil, close to the
leading edge is divided into two streams. The largest
portion of the stream which flows forward in the dir-
ection of the vane movement, enters the space between
the airfoil and the slat. The slat changes the direc-
tion of the airflow and drives it to the low pressure
side of the vane. The change of the airflow direction
creates a force acting on the slat in the direction of
the vane movement and at the same time, reduces the drag.
Furthermore, an increase of the flow on the low pressure
side further decreases the negative pressure and at the
same time, increases the productive force acting on
the vane.
The additional internal surface S2 of the slat
is intended to reduce an abrupt change in the airflow
cross-section area between the airfoil and the slat,
especially in its central portion and at the same time,
to reduce to its minimum the airflow turbulence.