Patent Description:
In wind turbines, an activation system may be provided for activating an active aerodynamic device provided on a surface of a wind turbine blade. The active aerodynamic device typically consists of a flap element installed on the external surface of the blade, which can be either retracted on the blade surface or lifted to modify the blade aerofoil properties.

The control of the retraction and lifting may be done by using a pressure supply system, for example a pneumatic pressure system, including a plurality of pressure ducts for feeding a pressure hose beneath the flap. By varying the pressure in the pressure hose, the flap may be lifted or retracted respectively away from and towards the blade surface. The pneumatic system is mainly installed inside the blade, but it may include at least an external portion (outer supply line) on the blade for reaching the hose.

The external portion of the pneumatic system may be positioned either on the pressure side or on the suction side of the blade, between the leading edge and the trailing edge. The positioning of the external portion on the blade may present a plurality of inconveniences. On an area close to the leading edge the presence of ducts may influence the flow of air around the blade, thus significantly reducing the performances of the turbine. Close to the trailing edge is a plurality of areas may not be used, due to the facts that:.

In addition to that the outer supply line needs to be longer when mounted closer to the trailing edge than when mounted closer to the leading edge of the blade section.

<CIT> discloses an actuator arrangement for moving an aerodynamic device of the above-described type.

The above considerations may apply also to any other type of energy distribution system, which may be installed on the blade and which include an external portion protruding from the suction side or the pressure side. Such energy distribution system may be, for example, an electrical or communication circuit comprising at least one external electric of optic fibre cable protruding from the suction side or the pressure side. In particular, such electrical circuit may be the lightening protection system, including on or more electric cables to be placed on the external surface of the blade.

Hence, it is desirable to overcome the above inconveniences by providing an improved blade where the above described ducts or cables or similar devices may be installed on a plurality of positions on the blade, without determining the above described inconveniences.

This scope may be met by the subject matter according to the independent claim.

According to the present invention, it is provided a blade for a wind turbine including:.

According to embodiments of the present invention, the aerodynamic element may cover the external portion of the energy distribution system with respect to airflow flowing around the blade. According to other embodiments of the present invention, the aerodynamic element may be attached to the external portion of the energy distribution system, so that the aerodynamic properties of such external portions are improved. According to other embodiments of the present invention, the aerodynamic element may be integrated in the external portion of the energy distribution system, so that the aerodynamic properties of such external portions are improved.

The present invention permits to remove a plurality of constraints when positioning the external portion of the energy distribution system. Such external portion may be for example positioned close to the leading edge, where less stresses are present in the blade panel. The aerodynamic element positioned over the external portion permits to conveniently reduce or avoid disturbances to the flow of air around the blade. The positioning may be optimized so that the overall length of the energy distribution system is made as short as possible. The aerodynamic element may be used for shielding any kind of duct, hose, and in non-claimed embodiments any kind of cable or wire. The aerodynamic element may provide anti-stall properties. In wind turbine blades, crossflows of airflow sometimes propagate along the longitudinal length of the wind turbine blade, from the root end of the blade. Such crossflows act to negatively impact on blade performance, in particular by contributing to airflow detachment from the surface of the blade, thereby affecting blade lift. By providing an aerodynamic element which extends across the surface of a wind turbine blade, transverse to its longitudinal axis, the formation of such cross-flows may be prevented.

Further advantages are achieved when positioning the external ducts of a pressure supply system for activating active aerodynamic devices. In such cases, the present invention permits to conveniently install the external portion on a leading-edge side of the blade section, which is normally free from conductors of the lightning protection system. The present invention therefore permits minimizing the conflicts between the pressure supply system of the aerodynamic devices and the lightning protection system. Positioning the external portion on a leading-edge side of the blade section may benefit from the fact that the blade panels are thinner at the leading-edge side than at the trailing edge side.

The drawings are in schematic form. Similar or identical elements are referenced by the same or different reference signs.

<FIG> shows a conventional wind turbine <NUM> for generating electricity. The wind turbine <NUM> comprises a tower <NUM> which is mounted on the ground <NUM> at one end. At the opposite end of the tower <NUM> there is mounted a nacelle <NUM>. The nacelle <NUM> is usually mounted rotatable with regard to the tower <NUM>, which is referred to as comprising a yaw axis substantially perpendicular to the ground <NUM>. The nacelle <NUM> usually accommodates the generator of the wind turbine and the gear box (if the wind turbine is a geared wind turbine). Furthermore, the wind turbine <NUM> comprises a hub <NUM> which is rotatable about a rotor axis Y. When not differently specified, the terms axial, radial and circumferential in the following are made with reference to the rotor axis Y.

The hub <NUM> is often described as being a part of a wind turbine rotor, wherein the wind turbine rotor is capable to rotate about the rotor axis Y and to transfer the rotational energy to an electrical generator (not shown).

The wind turbine <NUM> further comprises at least one blade <NUM> (in the embodiment of <FIG>, the wind rotor comprises three blades <NUM>, of which only two blades <NUM> are visible) mounted on the hub <NUM>. The blades <NUM> extend substantially radially with respect to the rotational axis Y. Each rotor blade <NUM> is mounted to the hub <NUM> at its root section <NUM>. The root section <NUM> is opposed to the tip section <NUM> of the rotor blade.

<FIG> illustrate a portion of a hollow rotor blade <NUM> comprised between the root section <NUM> and the tip section <NUM>, according to a first embodiment of the present invention. According to other embodiments of the present invention (not shown in the attached figures), the rotor blade <NUM> may be solid. According to the conventional naming of blade components, the rotor blade <NUM> comprises a suction side <NUM> and a pressure side <NUM>, both extending from a leading edge <NUM> to a trailing edge <NUM> of the rotor blade <NUM>. The suction side <NUM> and the pressure side <NUM> may be connected by one or more transversal shear webs <NUM> (one shear web <NUM> in the embodiments of the figures), which provide a reinforcement where the distance between the suction side <NUM> and the pressure side <NUM> are greater, i.e. at an intermediate between the leading edge <NUM> and the trailing edge <NUM>. The shear web <NUM> divides the rotor blade <NUM> in a leading-edge side <NUM>, comprised between the leading edge <NUM> and the shear web <NUM>, and a trailing-edge side <NUM>, comprised between the shear web <NUM> and the trailing edge <NUM>. The rotor blade <NUM> comprises on or more aerodynamic devices <NUM> (four aerodynamic devices <NUM> in the embodiment of <FIG>) in the form of an actuated spoiler. The aerodynamic devices <NUM> are arranged on the suction side <NUM> at an intermediate portion between the leading edge <NUM> and the trailing edge <NUM>, over the shear web <NUM>. According to other embodiments of the present invention (not shown in the attached figures), the aerodynamic devices <NUM> are arranged at the leading-edge side <NUM>. According to other embodiments of the present invention (not shown in the attached figures), the aerodynamic devices are in the form of an actuated flap, i.e. an aerodynamic device installed at the trailing edge <NUM> of the rotor blade <NUM>, or at the trailing-edge side <NUM>, close to the trailing edge <NUM>. The aerodynamic device <NUM> are movable by means of a pneumatic actuator <NUM> fed by a pressure supply system <NUM>. The pneumatic actuator <NUM> may be realized as a hose comprising an elastic outer skin, such that it can inflate and deflate reversibly and during many cycles when operated by means of the pressure supply system <NUM>. When the hose <NUM> is inflated the aerodynamic device <NUM> is moved in a protruded active configuration. When the hose <NUM> is deflated the aerodynamic device <NUM> is moved in a retracted inactive configuration, close to the blade.

The pressure supply system <NUM> comprises a plurality of inner supply lines <NUM> inside the leading-edge side <NUM> of the blade. The inner supply lines <NUM> are fixed to the shear web <NUM>. The inner supply lines <NUM> may be fixed to the shear web <NUM> by means of a plurality of fixtures <NUM> glued to the shear web <NUM>. The inner supply lines <NUM> a pressure pneumatic link between the hub <NUM>, where controllers and pumps (not shown) are mounted, to the pneumatic actuator <NUM>. The pressure supply system <NUM> further comprises one or more external ducts <NUM> (two external ducts <NUM> in the embodiment of <FIG> and <FIG>, each external duct being positioned between two adjacent aerodynamic device <NUM>) protruding from the suction side <NUM> at the the leading-edge side <NUM>. The external ducts <NUM> are arranged parallel to the suction side <NUM> and oriented chordwise with respect to the blade <NUM>, i.e. following, in the section view of <FIG>, the ideal line which connects the leading edge <NUM> and the trailing edge <NUM>. The pressure supply system <NUM> further comprises one or more through-shell connectors <NUM>, for connecting each of the external duct <NUM> to a respective inner supply line <NUM>. Each through-shell connectors <NUM> is arranged through a respective shell hole <NUM> provided across the suction side <NUM> of the blade at the leading-edge side <NUM>. Glue may be applied around the through-shell connectors <NUM> for sealing the respective shell hole <NUM>.

The rotor blade <NUM> further includes a lightning protection system (LPS) including a conducting cable <NUM> positioned along the shear web <NUM> inside the trailing-edge side <NUM> of the blade <NUM>. The lightning protection system (LPS) is therefore separated from the pressure supply system <NUM> by the shear web <NUM>.

The rotor blade <NUM> further includes at least one aerodynamic element <NUM> attached to the suction side <NUM> for aerodynamically shielding the external portion <NUM> of the pressure supply system <NUM>. In the embodiment of <FIG>, each aerodynamic element <NUM> is attached to the suction side <NUM> for covering a respective external duct <NUM>. The aerodynamic element <NUM> avoid or reduce turbulence around external duct <NUM>. The aerodynamic element <NUM> may be glued to the suction side <NUM>. Once aerodynamic element <NUM> is fixed to the rotor blade <NUM>, it further provides protection against weather conditions and pollutants, by preventing water or humidity or dust or similar agents to enter the blade <NUM> through the shell hole(s) <NUM>. This will make it even harder to get water penetration to the inner blade. Optionally, a second aerodynamic element <NUM> may be attached to the pressure side <NUM> at a symmetric position with respect to the aerodynamic element <NUM> on the suction side <NUM>, to create aerodynamic balance.

<FIG> illustrate a portion of a hollow rotor blade <NUM> comprised between the root section <NUM> and the tip section <NUM>, according to a second embodiment of the present invention. The second embodiment differentiates itself from the first embodiment in that the aerodynamic element <NUM> and, eventually, the second aerodynamic element <NUM>, extend from the the leading edge <NUM> to the trailing edge <NUM>.

<FIG> illustrates a portion of a hollow rotor blade <NUM> comprised between the root section <NUM> and the tip section <NUM>, according to a third embodiment of the present invention. The third embodiment differentiates itself from the first embodiment in that the pressure supply system <NUM> comprises a plurality of inner supply lines <NUM> inside the trailing-edge side <NUM> of the rotor blade <NUM> and in that the external ducts <NUM> protrude from the suction side <NUM> at the the trailing-edge side <NUM>. Aerodynamic elements <NUM> and, eventually, second aerodynamic element <NUM> (not shown in the embodiment of <FIG>) are provided similarly as in the first and in the second embodiment for covering the external ducts <NUM>.

According to other embodiments of the present invention (not shown) the aerodynamic elements <NUM> may be use for shielding other types of hoses or ducts protruding from the suction side <NUM> or from the pressure side <NUM>. For example, aerodynamic elements <NUM> may be used in connection with any active add-on, mounted on the trailing-edge side <NUM>, e.g. trailing edge flaps activated by a pneumatic system.

According to other non-claimed embodiments (not shown) the aerodynamic elements <NUM> may be use for shielding other types of components protruding from the suction side <NUM> or from the pressure side <NUM>. Such components may be included in other types of energy distribution systems, for example an electrical or communication circuit comprising at least one external cable protruding from the suction side <NUM> or the pressure side <NUM>. In such non-claimed embodiments, the aerodynamic element is attached to the the suction side <NUM> or the pressure side <NUM> for shielding the external cable(s).

Claim 1:
A blade (<NUM>) for a wind turbine (<NUM>) including:
- a suction side (<NUM>) and a pressure side (<NUM>) extending between a leading edge (<NUM>) and the trailing edge (<NUM>),
- an energy distribution system (<NUM>) having at least one external portion (<NUM>) protruding from the suction side (<NUM>) or the pressure side (<NUM>),
wherein the blade (<NUM>) further includes:
- at least one aerodynamic element (<NUM>) attached to the suction side (<NUM>) or the pressure side (<NUM>) for aerodynamically shielding the external portion (<NUM>) of the energy distribution system (<NUM>),
- at least one active aerodynamic device (<NUM>) and a pneumatic actuator (<NUM>),
wherein the energy distribution system (<NUM>) is a pressure supply system activating the at least one active aerodynamic device (<NUM>) provided on the suction side (<NUM>) or the pressure side (<NUM>), the active
aerodynamic device (<NUM>) being moved by means of the pneumatic actuator (<NUM>) fed by the pressure supply system (<NUM>), the pressure supply system (<NUM>) comprising at least one external duct (<NUM>) protruding from the suction side (<NUM>) or the pressure side (<NUM>), said aerodynamic element (<NUM>) being attached to the suction side (<NUM>) or the pressure side (<NUM>) for covering said external duct (<NUM>).