Wind turbine blade and method of controlling the lift of such a blade

Abstract

Wind turbine blade comprising a shape modifiable airfoil section that extends both chordwise and spanwise and has a not modified default shape, a conduit that extends from the inside of the blade towards the outside of the blade, and an outer part comprising a flow regulator that is located at the shape modifiable airfoil section and blocks the conduit when the shape modifiable airfoil section presents its default shape, and does not block the conduit when the shape modifiable airfoil section presents a modified shape. In the latter situation the conduit is opened to the outside of the blade and a device for exchanging a fluid between the inside and the outside of the blade is thus defined.

Claims

1. A wind turbine blade comprising: a shape modifiable airfoil section that extends both chordwise and spanwise and has an undeformed default shape, a conduit that extends from an inside of the blade to an outside surface of the blade, and an outer part of the conduit comprising a flow regulator located at the shape modifiable airfoil section, the flow regulator blocking the conduit when the shape modifiable airfoil section presents the default shape, and in a deformed shape, the shape modifiable airfoil section comprising an increased curvature that causes the flow regulator to move and unblock the conduit, thereby allowing an air exchange between the inside and the outside of the blade.

2. The wind turbine blade according to claim 1, wherein the outer part comprises a portion made of a deformable material.

3. The wind turbine blade according to claim 1, further comprising a plurality of outer parts distributed in a scattered fashion over the blade.

4. The wind turbine blade according to claim 1, wherein the conduit extends from a first outside surface of the blade to a second outside surface of the blade.

5. The wind turbine blade according to claim 4, wherein the second outside surface of the blade is located outside of the shape modifiable airfoil section.

6. The wind turbine blade according to claim 1, further comprising a plurality of conduits distributed along a substantially longitudinal slot which is closed by the outer part when the shape modifiable airfoil section presents the default shape and is not closed by the outer part when the shape modifiable airfoil section presents the deformed shape.

7. The wind turbine blade according to claim 6, wherein the plurality of conduits are distributed in a scattered fashion.

8. The wind turbine blade according to claim 6, further comprising a plurality of slots which are spanwise distributed in a scattered fashion.

9. The wind turbine blade according to claim 6, further comprising a plurality of slots which are chordwise distributed in a scattered fashion.

10. The wind turbine blade according to claim 1, further comprising a chamber located at the inside of the blade and connected to the conduit.

11. The wind turbine blade according to claim 10, further comprising more than one conduit extending from the chamber to different locations at the surface of the blade.

12. The wind turbine blade according to claim 1, wherein the shape modifiable airfoil section is located within a third of the chord of the blade corresponding to a trailing edge.

13. The wind turbine blade according to claim 1, wherein the shape modifiable airfoil section is located within a third of the chord of the blade corresponding to a leading edge.

14. A wind turbine comprising a blade according to claim 1.

15. A wind turbine blade comprising: a shape modifiable airfoil section that extends both chordwise and spanwise and has an undeformed default shape, a conduit that extends from an inside of the blade to an outside surface of the blade, and an outer part of the conduit comprising a flow regulator located at the shape modifiable airfoil section, the flow regulator being suited to block the conduit when the shape modifiable airfoil section presents the default shape, and not suited to block the conduit when the shape modifiable airfoil section presents a deformed shape, thereby allowing an air exchange between the inside and the outside of the blade; a chamber located at the inside of the blade and connected to the conduit; and wherein the chamber is provided with a membrane suited to vibrate when actuated by the air exchange.

16. The wind turbine blade according to claim 15, wherein the chamber, the membrane and the conduit form a synthetic jet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Some particular embodiments of the present invention will be described in the following, only by way of non-limiting example, with reference to the appended drawings, in which:

(2) FIG. 1 schematically shows the cross-section shape of a blade (i.e. the airfoil) with different deformations of the trailing edge section thereof;

(3) FIG. 2 schematically shows a deformation of the leading edge section;

(4) FIG. 3 schematically shows a different conduit configuration;

(5) FIG. 4 schematically shows a longitudinal view of a blade provided with some slots on its surface; and

(6) FIG. 5 schematically shows some conduits reaching one of said slots.

DESCRIPTION OF PARTICULAR EMBODIMENTS

(7) In the embodiment shown in FIG. 1 only the trailing edge section 1 of the blade is provided with some air-exchanging devices. Any such device comprises a chamber 20 located inside the blade and a conduit 15 that can connect said chamber with the outside of the blade; the inner end of the conduit 15 opens to the chamber 20 and the outer end of the conduit 15 almost reaches the blade surface 5 (the conduit actually reaches the outer surface when it is opened). The chamber 20 can be provided with a membrane 21 which divides the chamber in two regions, an outer region 22 connected to the conduit 15 and an inner region 23, thus forming, together with the conduit 15, a synthetic jet.

(8) FIG. 1A shows the blade in a relaxed state, i.e. not deformed. In this situation, one or more deformable outer parts (not shown), that may be a skin of the blade or some outer elements thereof (like a plurality of tiles), block the outer end of every conduit 15, effectively closing them, and there is no air-exchange between any chamber 20 and the outside of the blade.

(9) FIG. 1B shows the blade with a deformed trailing edge section 1. This deformation causes the outer parts to unblock the outer end of at least one conduit 15, effectively opening it, so that there can be an air-exchange between the chamber 20 and the outside of the blade in order to thwart the risk of flow separation at that area of the blade. If the chamber 20 comprises a membrane 21 (as in FIG. 1B), said membrane can be actuated to enhance the air-exchange; for example, the membrane can be made to oscillate by means of a piezoelectric actuator (not shown), for example at a high frequency.

(10) In general, the conduits 20 are opened in the areas of the blade where the curvature of the airfoil is highest, or at least above a certain level, which can be different from one area to another. The outer parts act like valve means than open and close the outer ends of the conduits. For example, some outer parts may be like a lid covering, and uncovering, the outer end of the conduits, in which case the outer part is itself a valve, or the valve means may be a narrow perforation in a deformable outer part, said perforation being closed when the outer part is in a relaxed condition and being opened when the outer part undergoes a certain deformation.

(11) FIG. 1C shows the blade with a further deformation in the trailing edge section 1, said further deformation causing the aperture of a further conduit 15 that is located nearer to the trailing edge than the previously opened conduit (FIG. 1B), and FIG. 1D shows a different deformation, this time causing the aperture of a conduit 15 that is farther from the trailing edge than the previously opened conduit (FIG. 1B). Note that the opened conduit 15 shown in FIG. 1D is the only one that is opened, meaning that the curvature of the airfoil is highest where the outer end of said conduit is located and is not quite enough to require flow control elsewhere.

(12) Also note that the chamber 20 which is shown connected to the outside of the blade in FIG. 1D is not provided with any membrane, the air-exchange thus being less intense than in the previous situations. This depends on the particular situation but in principle it does not depend on the chamber being nearer to or farther from the trailing edge.

(13) In the embodiment shown in FIG. 2 both the trailing edge section 1 and the leading edge section 2 are provided with synthetic jets, each of the latter comprising a conduit 25 and a chamber 30 provided with a membrane 31, analogously to the previous embodiment, although some chambers 30 might again not comprise any membrane.

(14) FIG. 2A shows the blade in a relaxed state, with all the conduits 25 blocked by the outer parts, and FIG. 2B shows the blade with the leading edge section 2 deformed, so that some conduits 15 are opened and there can be an air-exchange between one or more chambers 30 and the outside of the blade.

(15) FIG. 3 shows an embodiment that is not provided with any chamber and in which a conduit 35 and a conduit 36 meet inside the blade through a membrane 41. Said membrane can be actuated just like in the synthetic jets described above.

(16) FIG. 3A shows the blade in a relaxed state, with the conduits 35 and 36 blocked by the outer parts, and FIG. 3B shows the blade with the trailing edge section deformed and the conduits 35 and 35 opened to the outside.

(17) Alternatively, the conduits 35 and 36 can be connected without any membrane between them, so that the air-exchange between is just naturally established between the outer end area of the conduit 35 and the outer end area of the conduit 36.

(18) Another alternative to the embodiment of FIG. 3 is a chamber provided between the conduits 35 and 36 and comprising a membrane similar to the membrane 41.

(19) FIG. 4 shows a blade having a trailing edge section 1 and a leading edge section 2 and comprising a plurality of longitudinal slots 50 on its surface, either on the suction side or the pressure side or on both. As shown in FIG. 5, which is an enlarged view of a portion of FIG. 4, the outer ends of some conduits 45 reach said slots, i.e., they are opened to the outside through the slots 50. In this case, depending on the curvature of the airfoil along a slot 50, the outer parts will block or unblock it, thus closing or opening the conduits 45.

(20) As shown in FIGS. 4 and 5, the slots 50 can be distributed in a scattered fashion on the blade and the outer ends of the conduits 45 can be scattered along any such slot.

(21) Although only particular embodiments of the invention have been shown and described in the present specification, the skilled man will be able to introduce modifications and substitute any technical features thereof with others that are technically equivalent, depending on the particular requirements of each case, without departing from the scope of protection defined by the appended claims.

(22) For example, the drawings show only conduits opened to the suction side of the blade, but, depending on the circumstances, there can also be conduits opened to the pressure side of the blade.

(23) Or the described embodiments can be combined in any suitable way.

(24) Also, the slots 50 can have a direction other than the longitudinal one.