DAMAGE DETECTION OF A ROTOR BLADE OF A WIND TURBINE

Abstract

A method is proposed for detecting damage to at least one rotor blade of a wind turbine, including the following steps, monitoring during rotation of the at least one rotor blade at least one internal air condition inside a blade root of the at least one rotor blade, wherein the internal air condition is affected by a centrifugal effect pumping the air inside the at least one rotor blade from a root end towards a tip end and out of at least one hole of the at least one rotor blade, detecting damage to the at least one rotor blade based on the at least one monitored internal air condition. Further, a wind turbine and a device as well as a computer program product and a computer readable medium are suggested for performing the method.

Claims

1. A method for detecting damage to at least one rotor blade of a wind turbine, comprising the following steps: monitoring during rotation of the at least one rotor blade at least one internal air condition inside a blade root of the at least one rotor blade, wherein the internal air condition is affected by a centrifugal effect pumping the air inside the at least one rotor blade from a root end towards a tip end and out of at least one hole of the at least one rotor blade, and detecting damage to the at least one rotor blade based on the at least one monitored internal air condition.

2. The method according to claim 1, wherein the damage is detected when the at least one monitored internal air condition is different from a predetermined internal air condition.

3. The method according to claim 1, comprising: monitoring at least one further internal air condition inside the blade root of at least one further rotor blade, comparing the at least one monitored internal air condition with the at least one further monitored internal air condition, and detecting the damage to the at least one rotor blade based on the comparison.

4. The method according to claim 3, wherein the damage is detected when a difference between the compared internal air conditions is equal to or beyond a predetermined difference.

5. The method according to claim 1, comprising determining an internal air pressure value representing an internal air pressure inside the blade root of the at least one rotor blade, determining an ambient air pressure value representing an ambient air pressure outside the at least one rotor blade, determining an air pressure difference value between the internal air pressure value and the ambient air pressure value, detecting the damage to the at least one rotor blade based on the determined air pressure difference value.

6. The method according to claim 5, wherein the damage is detected when the determined air pressure difference value is equal to or below a predetermined threshold value.

7. The method according to claim 5, comprising determining at least one further internal air pressure value representing the air pressure inside a blade root of at least one further rotor blade, determining at least one further air pressure difference value between the at least one further internal air pressure value and the ambient air pressure value, comparing the air pressure difference value with the at least one further air pressure difference value, and detecting the damage to the at least one rotor blade based on the comparison.

8. The method according to claim 7, wherein the damage is detected when a difference between the compared air pressure difference values is equal to or beyond a predetermined threshold value.

9. The method according to claim 1, comprising determining an internal air flow value inside the blade root of the at least one rotor blade, and detecting the damage to the at least one rotor blade based on the determined air flow value.

10. The method according to claim 9, comprising comparing the internal air flow value with a predetermined air flow value, wherein the damage is detected when a difference between the compared air flow values is equal to or beyond a predetermined threshold value.

11. The method according to claim 9, comprising: determining at least one further internal air flow value inside a blade root of at least one further rotor blade, comparing the internal air flow value with the at least one further internal air flow value, detecting the damage to the at least one rotor blade based on the comparison.

12. The method according to claim 11, wherein the damage is detected when a difference between the compared internal air flow value and the at least one further internal air flow value is equal to or beyond a predetermined threshold value.

13. The method according to claim 9, wherein the internal air flow value is a wind speed value.

14. A wind turbine, comprising: at least one rotor blade, and a processing unit that is arranged for monitoring during rotation of the at least one rotor blade an internal air condition inside a blade root of the at least one rotor blade, wherein the internal air condition is affected by a centrifugal effect pumping the air inside the at least one rotor blade from a root end towards a tip end and out of at least one hole of the at least one rotor blade, and detecting damage to the at least one rotor blade based on the monitored internal air condition.

15. A computer program product, said computer program product having a non-transitory computer readable storage medium having instructions, which when executed by a processor, perform actions, directly loadable into a memory of a digital computer, comprising software code portions for performing the steps of the method of claim 1.

Description

BRIEF DESCRIPTION

[0082] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0083] FIG. 1 shows a schematically front view of a wind turbine including a functional extract of an exemplary embodiment of the inventive damage detection based on air pressure measurement; and

[0084] FIG. 2 shows a schematically front view of a wind turbine including a functional extract of an exemplary embodiment of the inventive damage detection based on air flow measurement.

DETAILED DESCRIPTION

[0085] FIG. 1 shows a schematically front view of an exemplary embodiment of a wind turbine 100 comprising a nacelle (not shown) being rotatable mounted on top of a tower 110. A rotor 111 is attached to an upwind side of the nacelle. The rotor 111 includes a central rotor hub and a plurality of rotor blades 120, . . . , 122 mounted to and extending radially from the rotor hub defining a rotor plane. Each rotor blade 120, . . . , 122 comprises a drain hole 125 at the tip end side.

[0086] According to an exemplary embodiment an air pressure sensor device 140, . . . , 142 is located inside a hollow space of a root section (blade root) of each rotor blade 120, . . . , 122. Each air pressure sensor device 140, . . . , 142 is measuring and determining the air pressure inside each root section. A resulting air pressure information like, e.g., an air pressure value 145, . . . , 147 is provided via a respective connection line 150 to a respective determination unit 151, . . . , 153.

[0087] The resulting air pressure information 145, . . . , 147 may be provided by use of any kind of communication system based on wire line or wireless data transmission technology.

[0088] Further, an air pressure sensor device 143 is located at a spinner of the rotor 111 measuring an ambient air pressure at a front side of the spinner. A resulting ambient air pressure information like, e.g. an ambient air pressure value 148 is provided via connection lines 156 to each determination unit 151, . . . , 153.

[0089] In the exemplary scenario as shown in FIG. 1 each determination unit 151, . . . , 153 is representing a differential air pressure gauge, each determining a difference between the provided air pressure information 145, . . . , 147 and the provided ambient air pressure information 148. An information 170, . . . , 172 representing the respective air pressure difference is forwarded by each determination unit 151, . . . , 153 via a respective connection line 160 to a monitoring unit 180.

[0090] Different monitoring concepts may be implemented by the monitoring unit 180.

[0091] For further explanation, the following exemplary scenario should be assumed.

[0092] Due to rotation of the rotor blades 120, . . . , 122 and based on the aforementioned centrifugal pump effect air inside the hollow space of each rotor blade 120, . . . , 122 is pumped from the root end to the tip end of each rotor blade 120, . . . , 122 and out of the respective drain hole 125. As a rotor blade 120, . . . , 122 is not air-tight per se, a part of the air pumped out via the drain hole 125 will be replaced by air being permanently sucked inside the hollow space of each rotor blade 120, . . . , 122. Thereby, due to nonstructural characteristic of a rotor blade, air will be mainly sucked through openings or holes at the root section of the rotor blade.

[0093] This results in a air flow inside the hollow space of each rotor blade 120, . . . , 122 from the root section towards the drain hole 125 which finally results in a air pressure difference between the air pressure inside the root section of each rotor blade 120, . . . , 122 and the ambient air pressure.

[0094] A crack 130 is exemplarily located at the rotor blade 120. As a consequence, additional air (also mentioned as false air) is sucked through the crack inside the hollow space of the rotor blade 120. Due to false air is entering the inner space of the rotor blade 120 the air pressure difference between the air pressure inside the root section of the rotor blade 120 and the ambient air pressure will decrease.

[0095] According to a first possible embodiment of the proposed solution, the respective air pressure difference information or value 170, . . . , 172 provided by each determination unit 151, . . . , 153 is monitored by the monitoring unit 180 thereby comparing each air pressure difference value 170, . . . , 172 with a predetermined threshold value. Thereby, if one of the monitored air pressure difference values 170, . . . , 172 drops below the threshold value an alarm signal 185 is generated by the monitoring unit 180 being provided at an output 181 of the monitoring unit 180 indicating a detected damage at the respective rotor blade 120, . . . , 121. In the exemplary scenario of FIG. 1, due the aforementioned decrease of the air pressure difference inside the root section of the rotor blade 120 the alarm signal 185 is indicating the crack 130 detected at the rotor blade 120.

[0096] According to a further possible embodiment, the provided air pressure difference values 170, . . . , 172 are compared by the monitoring unit 180. As an example, the provided air pressure difference value 170 provided by the determination unit 151 is compared with an average air pressure difference value based on the air pressure difference values 171, 172 provided by the other determination units 152, 153. Thereby, if the result of the comparison, i.e., the difference between the air pressure difference value 170 and the average air pressure difference value is beyond a predetermined threshold value the signal 175 is generated indicating a detected damage at a rotor blade.

[0097] FIG. 2 illustrates a schematically front view of a wind turbine including a functional extract of an alternative embodiment of the proposed damage detection, based on air flow measurement.

[0098] According to one further aspect of the proposed solution, by monitoring changes in the air flow inside the blade root of each rotor blade by the monitoring unit, one of more cracks in the shell or surface of the respective rotor blade may be detected.

[0099] The exemplary scenario as shown in FIG. 2 is mainly based on the scenario of FIG. 1, wherein equal reference numbers are used for elements or units having equal or similar functionalities, so reference is made respectively to the relevant elements or units in FIG. 1.

[0100] Instead of the air pressure sensor devices 140, . . . , 142 used in FIG. 1 an air flow measurement device 240, . . . , 242 is placed inside the hollow space of the root section of each rotor blade 120, . . . , 122. Each air flow measurement device 240, . . . , 242 is measuring characteristic of the air flow inside each root section of the respective rotor blade 120, . . . , 122.

[0101] The characteristic of the air flow may be measured by using, e.g., flow meters or ultra-sonic wind speed sensors located inside the hollow space of the rotor blade.

[0102] A respective air flow information or value 270, . . . , 272 representing the respective measured characteristic of the air flow is provided via a respective connection line 250 to a monitoring unit 280 monitoring and processing the provided values 270, . . . , 272.

[0103] According to a possible embodiment the respective air flow information or value 270, . . . , 272 provided by each air flow measurement device 240, . . . , 242 is monitored by the monitoring unit 280 thereby comparing each air flow value 270, . . . , 272 with a predetermined threshold value. If one of the monitored air flow values 270, . . . , 272 drops below the threshold value the alarm signal 185 is generated by the monitoring unit 280 being provided at the output 281 of the monitoring unit 280 indicating a detected damage at the respective rotor blade 120, . . . , 121.

[0104] According to a further possible embodiment, the air flow value (e.g. 270) provided by one air flow measurement device (e.g. 240) is compared with an average air flow value based on the air flow values (e.g. 271, 272) provided by the other air flow measurement devices 241,242. Thereby, if the result of the comparison, i.e. the difference between, e.g., the air flow value 270 and the average air flow value is beyond a predetermined threshold value the signal 185 is generated indicating a detected damage at a rotor blade 120.

[0105] Although the present invention has been disclosed in the form of preferred 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.

[0106] 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. The mention of a unit or a module does not preclude the use of more than one unit or module.