WO2008095707A2 - Device for the detection of vibrations or bending of rotor blades of a wind power plant - Google Patents

Abstract

The invention relates to a device for detecting vibrations or bending of a rotor blade (1) of a wind power plant. Said device comprises a deflection mechanism (4) that is provided with a linear element (9). The linear element (9) is arranged parallel to the internal wall of the aerodynamic rotor shell (2) in the longitudinal direction (Z) of the blade and is mounted on the internal wall of the rotor shell (2) at a fastening point (16) located at a distance from the root region. At the other end, the linear element (9) is connected to a sensor unit (5) which detects the lateral deflection of the linear element (9) and emits a signal indicating excessive bending of the rotor shell (2) or evaluates further at least when the rotor shell (2) is bent beyond a predefined measure. The invention is characterized in that the linear element (9) is embodied as a linear thread (9) that is mounted between the sensor unit (5) and the fastening point (16). Furthermore, the sensor unit (5) is attached at a non-bendable reference point (17) outside the aerodynamic rotor shell (2).

Description

Device for detecting vibrations or deflections of rotor blades of a wind turbine

The invention relates to a device for detecting vibrations or deflections of rotor blades of a wind turbine according to the preamble of patent claim 1.

In wind turbines in particular the rotor blades are among the most heavily loaded components. These usually consist of a glass fiber reinforced plastic (GRP) and are designed as a hollow wing, which is clamped on one side at its root area. Such rotor blades are about 30 to 80 m long and have a surface width of their aerodynamic shell of 2 to 3 m and are exposed in the operating state strong lateral wind loads. Due to the wind loads on the one hand clamped rotor blades caused strong bending moments within the aerodynamic shell which these rotor blades can bend preferably in the wind direction to about 20 cm or more. In addition, such rotor blades are delivered by their rotation and centrifugal forces, sunlight, different temperature influences and ice accumulation, which they need to hold many years in continuous operation to allow economic operation of the wind turbine.

For this reason, early detection of damage or overloads is necessary both in the aerodynamic shell of the rotor blade and on the supporting components within the rotor hub or its drive shaft. Because a series of damage, especially cracks or breaks in the shell,

Visual detachments, belt and web detachments as well as spalling could be detected early by a monitoring of the rotor blades and eliminated in order to avoid total damage to the entire system. For such rotor blades therefore numerous measures and facilities for monitoring and testing the operational and safety-relevant areas known, which are based mostly on the acquisition of relevant physical quantities of the relevant component areas.

Thus, from DE 10 2005 017 054 Al a method and a

Device for monitoring the state of rotor blades on wind turbines known. For this purpose, an accelerometer is mounted in the interior of the rotor blade in the first third of the root area on the inner shell, which is connected to a located in the rotor hub evaluation via a shielded

Cable is connected. In the evaluation unit, the structure-borne sound signals detected by the accelerometer are converted into their frequency spectrum and, by comparison with defined damage or reference spectra, possible rotor blade damage or overloads are determined therefrom. Since the actual transducer elements are mounted with their supply voltage and measurement lines within the rotor blade, this can lead to disturbances of the monitoring device or failure of the acceleration sensor at lightning overvoltages.

From DE 197 39 162 Al an adjusting device for rotor blades of a wind turbine is known in which the Blattanstellwinkel is adjusted according to the wind load. This invention is based on the finding that under strong wind loads, the rotors are heavily loaded on bending. Due to the increase of the wind load with the height of the rotor circuit, an aerodynamic thrust force of a rotor blade located in the upper half is considerably higher than in the lower rotor half circle near the ground. This leads to a cyclical course of the bending moments in the individual rotor blades with each revolution, which contribute to an increase in material fatigue and thus to a reduction in the service life. Therefore, near the root area of the Rotor blades strain gauges mounted on the inner wall of the aerodynamic shell, which the

Detecting the bending strain curve at each rotor revolution and feeding it through a cable connection in a gondola-mounted control device. To avoid such bending load fluctuations of the rotor blades, the angle of attack is therefore readjusted during each revolution on the basis of the determined bending load, so that it comes to a homogenization of the cyclic bending load, whereby the life of the rotor blades is to be extended. In this wind turbine, however, it is not intended to determine with the strain gauges detectable strain gauges maximum permissible wind loads or rotor damage.

From EP 1 075 600 Bl a wind turbine with a monitoring device for the rotor blades is known, which can determine damaging vibrations or strains in consequence to large or uneven forces. For this purpose, a triaxial acceleration sensor is preferably mounted in each rotor blade on the inside of the rotor shell at a predetermined distance from the rotor base. This can be accelerations of the aerodynamic shell are displayed, resulting from leaf or edge vibrations. With a signal evaluation unit, the natural frequencies of the rotor blades can also be estimated from the sensor signals. The triaxial acceleration sensors are incorporated in a battery powered black box, which apparently transmits the vibration signals from the interior of the rotor blade via a radio link to the signal processing unit, which indicates possible overloads or damage by comparison with known signal patterns. However, arranged in the rotor blade electrical Aufnehmersysteme are exposed to lightning very strong overvoltages and shocks that difficult to prevent or can be filtered out and so easily cause interference with this monitoring device.

From DE 198 47 982 C2 is another device for detecting vibrations on the rotor blades of a

Wind turbine known. In this device, a longitudinal bar is provided within the aerodynamic shell in the area near the rotor root. This longitudinal bar is mounted in two spaced-apart holding blocks, which are attached directly to the inner rotor blade wall. At one of the holding blocks, a distance sensor spaced apart by a defined air gap is arranged in front of the bar end. In a lateral deflection of the rotor blades as a result of strong wind load therefore also displaces the rigid longitudinal bar within its holding blocks, so that this can be detected by the distance sensor as a result of a change in the defined air gap. By specifying appropriate displacement limits, this can be displayed as overload or as rotor damage, which can be caused by extreme loads and shutdowns. This device requires at least for the distance sensor, the laying of a fault-prone cable connection within the aerodynamic rotor shell.

The invention is therefore based on the object, a

To provide a device for detecting vibrations or deflections of the rotor blades of a wind turbine, which is as immune to disturbance as possible and detects the rotor vibrations and deflections within a larger rotor blade area as accurately as possible.

This object is solved by the invention specified in claim 1. Further development and advantageous embodiments of the invention are specified in the subclaims. The invention has the advantage that a deflectable linear thread of the deflection device, a larger rotor blade area can be monitored or tested from the rotor root to the rotor tip, although this no wired and fault-prone transducer elements must be secured within the aerodynamic rotor shell. At the same time, such a deflection device with a linear thread has the advantage that it basically has only a small acceleratable mass, and therefore the measurement result of the detected rotor blade vibrations or deflections can not be adversely affected by the rotating and vibrated rotor blades due to an inherent acceleration.

The invention also has the advantage that the electrical or optical transducer elements are not arranged within the unshielded rotor blade, so that additional shielding or surge arrester can largely be dispensed with.

By arranged outside the aerodynamic inner shell reference point is advantageously achieved that it is unaffected by the vibrations and deflections of the rotor blade and thus is not changeable by opposing vibrations or deflections in its position to the measuring location. In this case, it is particularly advantageous that the mechanical detection of the rotor deflection can not lead to interference signals in the transducer elements which would have to be separated from the useful signals by means of complex filtering.

A particular embodiment of the invention with a linear yarn made of a high-strength fiber-reinforced plastic (GRP) has the advantage that this approximately the same temperature behavior Like the aerodynamic rotor blade shell, so that temperature compensation measures are not necessary because of different expansion.

In a further particular embodiment of the invention with a arranged on the bearing ring of the rotor blade transducer unit has the advantage that thereby the position of the deflection of the transducer unit even with an adjustment of the angle of attack can not change, so that automatically always the same direction of the deflection of the rotor blade is detected.

An additional special embodiment of the invention has a Wandlereiheit in which the deflection of the rotor blade is detected in two or all three spatial axes, which has the advantage that almost all possible operating conditions and damage to the rotor shell can be detected and evaluated. In particular, this means that both impermissible wind loads, excessive rotor speeds, impermissible imbalances, ice stocking and abrupt decelerations or damage to the hubs or in the generator area can be determined.

The invention will be explained in more detail with reference to an embodiment that is shown in the drawing. Show it:

Fig. 1: a schematic representation of a rotor blade with monitoring device arranged thereon, and

Fig. 2 is a schematic representation of one with a

Rotor root associated bearing ring and a pickup unit arranged thereon of a monitoring device. In Fig. 1 of the drawing, a monitoring device is schematically shown, which includes a deflection device 4 within the rotor blade 1 and a pickup unit 5 outside the aerodynamic shell of the rotor 1, wherein the deflection device 4 detects the lateral deflection of the rotor blade 1 and this on the pickup unit. 5 transmits, which converts them by means of a transducer element 7 in a rotor deflection proportional signal.

The rotor blade 1 shown schematically is part of a wind turbine, not shown, and forms with another offset by 180 ° wing the rotor, which is connected with its hub via a drive shaft with a generator. The rotor blade 1 has, for example, a length of about 50 m and at its root a circular

Inner diameters of about 2 m. The rotor blade 1 is hollow inside and has an aerodynamic rotor shell 2, which usually consists of a glass fiber reinforced plastic (GRP) and which is attached to a metal bearing ring 3.

Such a bearing ring 3 is shown in detail in Fig. 2 of the drawing. The bearing ring 3 is rotatably mounted in a bearing housing 8 within a nacelle, not shown, to align the rotor blade 1 in the desired angles of attack to the wind direction. Since such a rotor blade 1 is exposed in continuous operation different wind loads, wind turbulence and a Eisbesatz, arise at its aerodynamic shell 2 low-frequency vibrations and deflections in all three spatial axes, which can lead to material damage or material overloads or are caused by them. In particular, abrupt deflections in the edge direction X or in the direction of the blade Y can cause a breakage of the rotor shell 2 or an impermissible wind load as the cause. At longer service life can also by a relatively low cyclic alternating load material fatigue occur, which manifests itself in the long term in a change in the rotor blade deflection or the vibration behavior. In order to detect these damaging loads or damage already occurred, the device according to the invention is used.

In Fig. 1 of the drawing, such a monitoring device is shown schematically, which detects only one bending direction and preferably the rotor blade oscillations or -blattdurchbiegungen in the Y direction and that in the wind direction transverse to the flat shell surface. For this purpose, a deflection device 4 is mounted within the aerodynamic rotor shell 2 on the reinforced synthetic material, which consists essentially of a linear high-strength thread 9 made of a fiber-reinforced plastic. This linear yarn 9 preferably has a diameter of 0.5 to 1.5 mm and is firmly connected within the rotor shell 2 in the longitudinal direction of a fastening unit 10 with one of its two ends. The fastening unit 10 is approximately 15 m away from the bearing ring 3 in the blade interior mounted on a wall of the flat rotor shell side preferably in the middle. As a result, the fastening unit 10 is deflected in accordance with the deflection of the rotor blade 1 mostly in the wind direction with the rotor blade 1. The distance is dependent on the flexibility of the rotor blade and in practice is usually between 2 m and 15 m. Preferably, the synthetic fiber thread 9 is still arranged on a tension spring 11 so that it always remains linearly aligned with a given clamping force. For this purpose, the fixing unit 10 is formed so that the linear thread 9 is spaced from the inner wall of the rotor shell 2 and indeed so far that it can not touch the rotor shell 2 at maximum lateral deflection. With its opposite second end of the synthetic fiber thread 9 is fixed in the pickup unit 5. In this, a tension roller 12 is provided, which is locked against the spring force of the fastening unit 10 via a toothed ratchet, so that the thread 9 is always stretched with a predetermined clamping force linearly between the pickup unit 10 and the attachment point 16 on the rotor inner wall. In this case, the clamping force of the circular tension roller 12 can be specified as a fastening element by a specific torque, with which the sensitivity of the device is adjustable. In a particular embodiment of the invention, a Spannkrafteinstellvorrichtung is provided, in which via a geared motor, the clamping force can be set automatically with a predetermined value and readjusted at certain intervals.

To protect the linear yarn 9, in a further particular embodiment, the latter may preferably be surrounded by a protective tube (not shown) between the pick-up unit 5 and the fastening unit 10, which is hingedly connected to the fastening unit 10 and / or the pick-up unit 5. As a result, the monitoring device forms a structural unit, which is given a thread length. Through the protective tube of the linear yarn 9 can be biased, wherein the assembly preferably has a length of 1 to 5 m. For larger monitoring sections and longer units are executable that can be provided with telescopic tubes for transport reasons.

In the pickup unit 5 is still a transducer element 7 is provided, which is connected to the linear yarn 9. This transducer element 7 may represent a sensitive force transducer, which is non-positively or positively connected via a transverse web 13 with the linear thread 9 spaced from the tension roller 12. In this case, the force transducer 7 with its force introduction side 14 with the transverse web 13 and with its force receiving side 15 connected to the housing of the pickup unit 5. The longitudinal distance between the tension roller 12 and the transverse web 13 is selected so that the force causes a sufficient signal resolution in a side deflection of the linear yarn 9, with a distance of about 5 to 10 cm from the second clamping end is sufficient. At least during the initial assembly, the pickup unit 10 must be aligned such that the linear thread 9 has a straight alignment from its clamping end the reference point 17 to the attachment point 16, so that no force is introduced into the force transducer 7 without a rotor blade deflection. For such a calibration of the force transducer, the circular tension roller 12 may also be arranged on an eccentric mounting plate or the tension roller 12 may be formed in eccentric shape to its axis of rotation. By a corresponding rotation of the eccentric mounting plate or the eccentric tension pulley then the force transducer could be calibrated in which he gives no or no defined output signal without deflection of the rotor blade 1. By means of a motor-driven adjustment of the eccentric mounting plate or the eccentric tension roller 12, such a calibration could also be carried out automatically and can be repeated at regular intervals as a new calibration. This would lead to a considerable simplification in the installation and calibration of the monitoring device.

With appropriate sensitivity is also conceivable, the force transducer 7 directly and articulated between the second

Provide clamping end as a reference point 17 of the linear yarn 9 and its force introduction side 14. As transducer elements 7 and force transducer with optical strain gauges according to DE 10 2005 030 751 Al are used, which are much less sensitive to electromagnetic interference or against surges. In a further conceivable embodiment, the deflection of the linear yarn 9 can also be detected directly by means of distance sensors, preferably by optical or inductive distance sensors.

The pickup unit 5 is preferably made of a shielded metal housing, which is attached as shown in Fig. 2 of the drawing on the inner wall of the bearing ring 3 outside the rotor shell 2 as a reference point 17. The reference point 17 can, however, also be arranged elsewhere outside the aerodynamic rotor shell 2 of the rotor blade 1, but it must be ensured that the deflection of the linear thread 9 does not change even with a change in the angle of attack, such as e.g. on the axis of rotation. By the force transducer 7 is at a lateral

Deflection of the rotor blade 2 in the wing direction Y via the transverse web 13, the introduced force is converted into an electrical signal which is proportional to the deflection or deflection or the low-frequency oscillation of the rotor blade 1. Therefore, the pick-up unit 5 is still electrically connected to an evaluation device 6, in which the Aufnehmersignale can be evaluated, displayed or signaled in any other way. For this purpose, the evaluation device 6 is given corresponding reference or limit values, which are e.g. a maximum allowable lateral

Specify sag Y, in which reach an overload case displayed and / or changed the rotor blades 1 in their angle of attack and / or the wind turbine is to be shut down altogether. In the evaluation device 6 also strong temporal change values can be specified and recorded

Vibration or deflection values are compared, for example, can occur in a known rotor damage and require immediate repair or shutdown. Furthermore, such a device can also be used for test purposes, in which the bending strength of the rotor blade 1 or its fatigue phenomena are determined. In a specific embodiment of the device has also proved to be advantageous to provide a separate monitoring device in each of the two rotor blades 1, whereby damage can be derived by comparing the individual measured values of each blade 1 with the same rotor position. For this purpose, the acquired measured values can be stored in a program-controlled electronic

Evaluation or computing device 6 are detected and stored to compare these measurements with the other rotor readings in the same rotor position.

In a particular embodiment of the invention could be arranged in the rotor blade 1 opposite two separate monitoring devices. For this purpose, two deflecting devices 4 would have to be provided at least on the opposite flat rotor inner surface, whose deflections could be detected both in a common pickup unit 5 or two separate pickup units 5 arranged opposite one another. A different deflection in sheet direction Y would mean a torsion of the rotor blade 1 about one of its longitudinal axes. Therefore, then with an appropriate

Deflection of the rotor blade 1 and the torque about a longitudinal axis of the rotor blade and thus the torsion of the rotor blade 1 are monitored.

In Fig. 2 of the drawing is in particular a

Monitoring device for a rotor blade 1 shown schematically, with which the vibrations and / or deflections of the rotor blade 1 in at least two or all three spatial axes X, Y, Z can be detected. For this purpose, in the pickup unit 5, preferably two or three force transducers 7 are provided, which detect the thread tension not only in a deflection in the wing or wind direction (Y), but also in the direction of the edges (X) and / or in wing longitudinal direction (Z). For this purpose, the force transducers 7 are preferably arranged in two or all three spatial axes (X, Y, Z direction) offset by 90 ° and connected to the linear thread 9 in such a way that they detect their tension force components separately.

It can be concluded from the additional edge deflection (X) to short circuits in the generator or sudden shaft damage of the drive shaft. Therefore, in the special evaluation device 6, first all direction components are detected separately and evaluated and displayed in separate evaluation circuits 18 for each of the two or three spatial directions X, Y, Z or further processed in a subsequent data processing system. Deflections in the edge direction X, which require defrosting and can be displayed separately as edge vibrations or edge deflections ΔX, also occur with strong ice lapping on the rotor blades 2.

From the detection of the yarn tension in the rotor longitudinal direction Z, in particular increased centrifugal forces can be inferred when exceeding a predetermined maximum speed, so that this is determined by comparison with a reference yarn tension at a specific speed specification in a dedicated evaluation circuit 18 and displayed as a speed overshoot. Thus, with the detection of the two or three bending directions X, Y, Z almost all possible rotor damage and / or operating conditions can be detected and ermiccelbar by appropriate specifications and computer programs.

Claims

claims 1. A device for detecting vibrations or deflections of a rotor blade (1) of a wind turbine with a deflection device (4) which contains at least one linear element (9) which extends approximately parallel to the inner wall of the aerodynamic rotor shell (2) and at one of the Root area spaced attachment point (16) on the inner wall of the rotor shell (2) is mounted, wherein the linear element (9) is connected to a pickup unit (5) which detects the lateral deflection of the linear element (9) and at least when exceeding a predetermined deflection the rotor shell (2) signals this, characterized in that the linear element (9) as between the pickup unit (5) and the attachment point (16) clamped linear thread (9) is formed and that the pickup unit (5) outside the aerodynamic rotor shell (2 ) is attached to a non-bending reference point (17). 2. Apparatus according to claim 1, characterized in that in the aerodynamic rotor shell (2) two deflection devices (4) are provided, which are arranged approximately opposite each one of the two flat side of the rotor shell (2) and for determining a Torsionsmoments order a longitudinal axis of the rotor blade (1) are used. 3. Apparatus according to claim 1 or 2, characterized in that the linear thread (9) consists of a high-strength fiber-reinforced plastic whose diameter has at least 0.5 to a maximum of 5 mm. 4. Device according to one of the preceding claims, characterized in that for fixing the linear yarn (9) at the attachment point (16) a fastening unit (10) is provided, which includes a spring element (11) between the end point of the linear yarn (9). and the attachment point (16) on the rotor shell (2) is arranged. 5. Apparatus according to claim 4, characterized in that between the fastening unit (10) and the Receiving unit (5) of the linear thread (9) is surrounded by a protective tube which is at least articulated to the fastening unit (10) and / or the pickup unit (5). 6. Device according to one of the preceding claims, characterized in that the pickup unit (5) is attached to a part of the bearing unit (3) in the root region of the rotor blade (2) or in the hub region, which forms a reference point (17). 7. Device according to one of the preceding claims, characterized in that in the pickup unit (5) transducer elements (7) are provided, which are arranged so that they detect at least one deflection component (X, Y, Z) of the linear yarn (9). 8. Device according to one of the preceding claims, characterized in that the linear thread (9) in the Pick-up unit (5) is attached to a tensionable fastening element (12). 9. Device according to one of the preceding claims, characterized in that the fastening element (12) is arranged on an eccentric mounting plate or as eccentric tension roller (12) and for the calibration of the force transducer (7) or for linearization of the linear yarn (9) , 10. Device according to one of the preceding claims, characterized in that the fastening element is designed as a circular tension roller (12) and is connected to a regulated Spannkrafteinstellvorrichtung, with a predetermined yarn tension and is adjustable. 11. Device according to one of the preceding claims, characterized in that in front of the fastening element (12) in the direction of the rotor shell as a transducer element (7) at least one force transducer is provided whose force introduction side (14) the force at a lateral deflection of the linear yarn (9). detected . 12. Device according to one of the preceding claims, characterized in that the force transducer (7) has a deformation body with electrical strain gauges (DMS) or optical strain gauges. 13. Device according to one of the preceding claims, characterized in that in the pickup unit (5) two transducer elements (7) are provided, wherein the first transducer element (7) detects the deflection in the wing direction Y and the second transducer element, the deflection in the edge direction X. 14. Device according to one of the preceding claims, characterized in that in the pickup unit (5) three transducer elements (7) are provided, wherein the first transducer element (7) the deflection in the wing direction Y and the second transducer element, the orientation in the edge direction X and the third transducer element detects the thread tension in the rotor longitudinal direction Z, wherein all transducer elements (7) are aligned offset in the spatial direction 90 °. 15. Device according to one of the preceding claims, characterized in that the signals of the transducer elements (7) of an evaluation device (6) are supplied, which is designed as electronic computing device and the reference or limits are given, from which they are detected with the help of Vane deflections and / or vane oscillations determined at least compliance with the maximum permissible wind load and signaled when exceeded.