ASSEMBLY AND METHOD FOR MONITORING AIR FLOW AT A SURFACE OF A ROTOR BLADE OF A WIND TURBINE

Abstract

An assembly for monitoring air flow at a surface of a rotor blade of a wind turbine is provided. The assembly includes (a) a surface module adapted to be arranged at a predetermined location of the rotor blade surface, the surface module including two air inlets facing opposite directions along an axis, (b) a sensor module including two pressure sensors, wherein one of the two pressure sensors is in fluidic communication with one of the two air inlets and the other one of the two pressure sensors is in fluidic communication with the other one of the two air inlets, wherein the sensor module is adapted to output two pressure signals indicative of the pressures sensed by the two pressure sensors, and (c) a processing unit adapted to determine at least one of a flow direction and a flow speed along the axis based on the two pressure signals.

Claims

1. An assembly for monitoring air flow at a surface of a rotor blade of a wind turbine, the assembly comprising: a surface module configured to be arranged at a predetermined location on the surface, the surface module comprising two air inlets facing opposite directions along an axis; a sensor module comprising two pressure sensors, wherein one of the two pressure sensors is in fluidic communication with one of the two air inlets and the other one of the two pressure sensors is configured in fluidic communication with the other one of the two air inlets, wherein the sensor module is configured to output two pressure signals indicative of pressures sensed by the two pressure sensors; and a processing unit configured to determine at least one of a flow direction and a flow speed along the axis based on the two pressure signals; wherein the surface module comprises two additional air inlets facing opposite directions along the axis and being located above the two air inlets; wherein the sensor module comprises two additional pressure sensors, one of the two additional pressure sensors being in fluidic communication with one of the two additional air inlets and the other one of the two additional pressure sensors being in fluidic communication with the other one of the two additional air inlets, the sensor module being configured to output two additional pressure signals indicative of the pressures sensed by the two additional pressure sensors; wherein the processing unit is configured to determine at least one of an additional flow direction and an additional flow speed based on the two additional pressure signals.

2. The assembly according to claim 1, wherein the processing unit is configured to determine the flow direction along the axis by determining the sign of the difference between the two pressure signals.

3. The assembly according to claim 1, wherein the processing unit is configured to determine the flow speed along the axis by determining a magnitude of a difference between the two pressure signals.

4. The assembly according to claim 1, wherein one of the two air inlets is facing a leading edge of the rotor blade and the other one of the two air inlets is facing a trailing edge of the rotor blade.

5. The assembly according to claim 1, wherein: the surface module comprises two further air inlets facing opposite directions along a further axis; the sensor module comprises two further pressure sensors, one of the two further pressure sensors being in fluidic communication with one of the two further air inlets and the other one of the two further pressure sensors being in fluidic communication with the other one of the two further air inlets, the sensor module being configured to output two further pressure signals indicative of the pressures sensed by the two further pressure sensors; and the processing unit is configured to determine at least one of a further flow direction and a further flow speed along the further axis based on the two further pressure signals.

6. The assembly according claim 5, wherein the axis and the further axis extend in a plane parallel to the surface of the rotor blade and with a predetermined angle therebetween.

7. The assembly according to claim 6, wherein the predetermined angle is selected from the group consisting of: 15°, 30°, 45°, 60° and 90°.

8. The assembly according to claim 1, wherein the sensor module and the processing unit form an integrated module configured to be arranged within the rotor blade.

9. The assembly according to claim 1, wherein the sensor module is configured to be arranged at a first location within the rotor blade, wherein the processing unit is configured to be arranged at a second location, and wherein the sensor module and the processing unit are configured for wired or wireless data communication with each other.

10. The assembly according to claim 1, further comprising at least two chambers for collecting and draining water that enters through the two air inlets.

11. A wind turbine comprising a rotor having a plurality of rotor blades and configured to drive a generator arranged within a nacelle on top of a tower, the wind turbine comprising at least one assembly according to claim 1 for monitoring air flow at a surface of each of the rotor blades.

12. A method of monitoring air flow at a surface of a rotor blade of a wind turbine, the method comprising: arranging a surface module at a predetermined location on surface, the surface module comprising two air inlets facing opposite directions along an axis and two additional air inlets facing opposite directions along the axis and being located above the two air inlets; providing a sensor module comprising two pressure sensors, wherein one of the two pressure sensors is in fluidic communication with one of the two air inlets and the other one of the two pressure sensors is in fluidic communication with the other one of the two air inlets, wherein the sensor module is configured to output two pressure signals indicative of the pressures sensed by the two pressure sensors, the sensor module further comprising two additional pressure sensors, one of the two additional pressure sensors being in fluidic communication with one of the two additional air inlets and the other one of the two additional pressure sensors being in fluidic communication with the other one of the two additional air inlets, the sensor module being configured to output two additional pressure signals indicative of pressures sensed by the two additional pressure sensors; and determining at least one of a flow direction and a flow speed along the axis based on the two pressure signals and determining at least one of an additional flow direction and an additional flow speed based on the two additional pressure signals.

Description

BRIEF DESCRIPTION

[0036] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0037] FIG. 1 shows a side view of an assembly according to an exemplary embodiment of the present invention;

[0038] FIG. 2 shows a top view of a surface module according to an exemplary embodiment of the present invention;

[0039] FIG. 3 shows an illustration of air flow at the surface of a rotor blade of a wind turbine;

[0040] FIG. 4 shows a side view of an assembly according to an exemplary embodiment of the present invention;

[0041] FIG. 5 shows a rotor blade of a wind turbine comprising an assembly in accordance with an exemplary embodiment of the present invention; and

[0042] FIG. 6 shows a side view of an assembly according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

[0043] FIG. 1 shows a side view of an assembly according to an exemplary embodiment of the present invention. More specifically, FIG. 1 shows an assembly comprising a surface module 10, a sensor module 20, and a processing unit 30.

[0044] The surface module 10 is arranged at the surface 1 of a rotor blade 2 and comprises two air inlets 11 and 12 facing in opposite directions along an axis. More specifically, the air inlet 11 is facing in a direction towards the leading edge as indicated by arrow LE, i.e., towards the incoming wind W. The other air inlet 12 faces in the opposite direction, i.e., against the trailing edge of the rotor blade 2, as indicated by arrow TE. In the embodiment shown in FIG. 1, the air inlets 11, 12 are formed as flat passageways between a lower plate 15 and an upper plate 16. The air inlet 11 is in fluid communication with the sensor module 20 through a suitable conduit 21, such as a hose or pipe. Similarly, the air inlet 12 is in fluid communication with the sensor module 20 trough conduit 22.

[0045] The sensor module 20 is arranged within the rotor blade 2 and comprises pressure sensors (not shown) arranged to measure the respective pressures at the ends of conduits 21 and 22. Two corresponding pressure signals are transmitted to the processing unit 30 by wireless transmission 25. In an alternative embodiment, a wired data transmission may be utilized.

[0046] The processing unit 30 may be a separate unit (e.g., part of a wind turbine controller) or it may be integrated with the sensor module 20. The processing unit 30 determines a flow direction and/or a flow speed along the axis, i.e., in the direction from the leading-edge LE to the trailing edge TE, based on the received pressure signals. More specifically, the processing unit 30 determines whether the pressure difference between the two air inlets 11, 12 is positive or negative. If it is positive, i.e., if the pressure measured through air inlet 11 is higher than the pressure measured through air inlet 12, the processing unit 30 determines that the flow along the axis is directed from the leading-edge LE towards the trailing edge TE. On the other hand, if the pressure difference is negative, i.e., if the pressure measured through air inlet 11 is less than the pressure measured through air inlet 12, the processing unit 30 determines that the flow along the axis is directed in the opposite direction, i.e., from the trailing edge TE towards the leading-edge LE. Furthermore, the processing unit may determine the flow speed along the axis by determining the magnitude of the pressure difference. The larger the magnitude of the pressure difference is, the larger is the flow speed and vice versa.

[0047] FIG. 2 shows a top view of a surface module 10 according to an exemplary embodiment of the present invention. More specifically, the surface module 10 comprises the two air inlets 11, 12 already discussed above in conjunction with the embodiment shown in FIG. 1 and two further air inlets 13 and 14 facing opposite directions along a further axis which is perpendicular to the axis of air inlets 11 and 12. The separation between the air inlets 11, 12, 13, 14 is provided by two walls 17 and 18 extending perpendicular to each other along respective diameters in the space between the lower plate 15 and the upper plate 16. The two further air inlets 13, 14 are in fluidic communication with respective pressure sensors (not shown) within sensor module 20 in the same or in a similar way as described above with regard to the two air inlets 11 and 12. Hence, the processing unit 30 received two further pressure signals and is capable of determining a further flow direction and/or a further flow speed along the further axis, i.e., in a direction perpendicular to the main flow direction which extends between the leading edge LE and the trailing edge TE. A significant flow in this transverse direction would be an indication of undesirable flow conditions and could be used correspondingly in the control of the wind turbine.

[0048] Under normal operating conditions, the channel facing the air stream W, i.e., the air inlet 11, will experience the greatest pressure while the channel exactly opposite to that, i.e., the air inlet 12, experiences the least pressure. Hence, the pressure difference between the two would indicate which of the air inlets 11, 12 is facing the airflow. The simplest representation of this sensor would consist of a number of pitot tubes pointing in different direction at the same height from the surface 1.

[0049] FIG. 3 shows an illustration of air flow at the surface 1 of a rotor blade 2 of a wind turbine. This illustration is useful for understanding the principle behind using the flow direction as a measure of the flow quality on the rotor blade 2. Under normal conditions of attached flow, the flow along the surface 1 of the rotor blade 2 is moving towards the trailing edge TE as is the case in the front region A of the blade section shown in FIG. 3. However, under some conditions, such as soiling, high shear, yaw errors, etc., the flow might separate from the blade surface 1. In this case, the flow along the surface 1 of the rotor blade 2 reverses direction and starts flowing towards the leading edge LE as can be seen on the aft part of the blade section in region B. Thus, the flow direction in point P is useful for determining the state of the boundary layer on the rotor blade 2.

[0050] FIG. 4 shows a side view of an assembly according to an exemplary embodiment of the present invention. As can be seen, this embodiment is similar to the embodiment depicted in FIG. 1 but differs therefrom in that the surface module 10 comprises two additional air inlets 11a and 12a arranged above the air inlets 11 and 12, i.e., further above the blade surface 1. The additional air inlets 11a and 12a are in fluidic communication with corresponding pressure sensors (not shown) within sensor module 20 through corresponding conduits 23 and 24. In addition to the lower plate 15 and upper plate 16, the surface module comprises an intermediate plate 19 that separates the air inlets 11, 11a and 12, 12a in the vertical direction. The processing unit is hence capable of determining an additional flow direction and/or an additional flow speed along the axis (from leading edge LE towards trailing edge TE) but at a further elevated level above the surface 1 of the rotor blade 2. The knowledge on flow direction and/or flow velocity in several layers above the blade surface provides additional information on the state of the boundary layer, in particular on whether the flow is starting to separate or has completely separated.

[0051] FIG. 5 shows a rotor blade 2 of a wind turbine comprising an assembly in accordance with an exemplary embodiment of the present invention. As shown, the surface module 10 is arranged at the surface 1 of the rotor blade and in fluidic (or electric) communication with the sensor module 20 through conduits (or wires) 21 and 22. The sensor module 20 is located within the rotor blade 2 and may communicate with the processing unit 30 (not shown) utilizing wireless or wired data transmission.

[0052] FIG. 6 shows a side view of an assembly according to an exemplary embodiment of the present invention. This embodiment is a variation of the embodiment shown in FIG. 1 and discussed above. More specifically, the conduits providing fluidic communication between the air inlets 11, 12 of the surface module 10 and the sensor module 20 extend through respective chambers 41 and 42 that serve to collect and drain water entering through the air inlets 11 and 12. As shown, the fluidic communication between air inlet 11 and the sensor module 20 is provided by a pair of conduits 21a and 21b and the chamber 41, while the fluidic communication between air inlet 12 and the sensor module 20 is provided by another pair of conduits 22a and 22b and the chamber 42. The tube 21a extends from air inlet 11 into an upper part of chamber 41 while the tube 21b has an open end that is within the chamber 41 at an elevated position above the bottom of the chamber 41 and continues to the sensor module 20. Similarly, the tube 22a extends from air inlet 12 into an upper part of chamber 42 while the tube 22b has an open end that is within the chamber 42 at an elevated position above the bottom of the chamber 42 and continues to the sensor module 20. The chamber 41 has a drain 43 through which water is removed (by a pump or by gravity or centrifugal forces). Similarly, the chamber 42 has a drain 44 for removing water. The chambers 41 and 42 assures that water getting in through the air inlets 11 and 12 cannot reach the pressure sensors within the sensor module 20.

[0053] Although the present invention has been disclosed in the form of embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0054] For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.