DK2741069T3 - Prøvebænk til rotorblade eller rotorbladesegmenter, arrangemenet omfattende sådan prøvebænk og prøvefremgangsmåde - Google Patents

Description

TEST BENCH FOR A ROTOR BLADE OR A ROTOR BLADE SEGMENT, ARRANGEMENT COMPRISING SUCH A TEST BENCH AND TEST

METHOD

Description [0001] The invention relates to a test bench for a rotor blade or a rotor blade segment, especially a rotor blade or a rotor blade segment for a wind turbine, according to the preamble of Patent Claim 1. The invention moreover relates to an arrangement with such a test bench and a rotor blade or a rotor blade segment as well as a method for operating the test bench. A test bench of the mentioned kind is known from WO 2008/145727 Al.

[0002] The known test bench is used in vibration testing of rotor blades, wherein the rotor blade is mounted on a foundation of the test bench in horizontal position. At a distance from the foundation there is provided an excitation unit, which is secured to the floor of the test bench and which transmits an excitation oscillation by a lever to the rotor blade. The excitation unit is designed in the form of a hydraulic cylinder for this purpose. Thanks to the lever arrangement between the hydraulic cylinder and the rotor blade, the vibrating mass is reduced. Specifically, an upward movement of the hydraulic cylinder means a downward movement of the rotor blade. The deflection of the rotor blade under the action of the hydraulic cylinder is limited by the lever length. Furthermore, the known test bench only inadequately takes into account the operating loads occurring in real operation and acting on the rotor blade. In real operation, a buoyancy force is created due to the oncoming flow against the rotor blades, which cannot be simulated with the known test bench.

[0003] Similar test benches are disclosed by WO 2011/091081 Al, WO 2004/005879 Al and WO 2010/000711 A2. From WO 2012/097475 Al there is known an apparatus for carrying out inspections of rotor blades of a windmill, which can be braced by arms arranged in the manner of a tripod against the inner wall of a rotor blade and can thus perform measurements on the inside of the rotor blade.

[0004] Furthermore, test benches for rotor blades or turbine blades are known from the field of aviation. Such test benches are described for example in WO 2009/112795 A2 and EP 2 336 744 Al.

[0005] The problem which the invention proposes to solve is to indicate a test bench for a rotor blade or a rotor blade segment which faithfully reproduces the operating loads occurring in the real operation and in particular takes into account the buoyancy forces. Moreover, the problem of the invention is to indicate an arrangement with such a test bench as well as a method for operating such a test bench.

[0006] According to the invention, this problem is solved in regard to the test bench by the subject matter of Patent Claim 1, in regard to the arrangement by the subject matter of Patent Claim 7, and in regard to the operating method by the subject matter of Patent Claim 8.

[0007] In particular, the problem is solved by a test bench for a rotor blade or a rotor blade segment, especially a rotor blade or a rotor blade segment for a wind turbine, wherein the test bench comprises at least one support structure to which it is possible to attach one axial end of the rotor blade or of the rotor blade segment, and wherein at least one excitation unit is provided, which can be connected to the rotor blade or the rotor blade segment in order to excite an oscillation of the rotor blade or of the rotor blade segment. A loading means is attached to a fixed articulation point. The loading means can be connected to the rotor blade or the rotor blade segment for the testing operation such that a static prestress force, whose force direction comprises at least one component oriented perpendicular to the rotor blade or rotor blade segment, can be applied to the rotor blade or the rotor blade segment.

[0008] The loading means as a component of the test bench makes the testing more realistic. In particular, with the loading means it is possible to apply a static prestress force to the rotor blade or the rotor blade segment, so that for example the buoyancy force occurring in real operation can be simulated. Thus, with the test bench according to the invention, it is possible to perform testing which is overall more realistic than that with the test benches known in the prior art. The test bench according to the invention thus enables a relatively accurate modelling of the static operating loads occurring in the real operation.

[0009] It should be noted that the articulation point for the test bench according to the invention may be fixed only in the test operation. Between individual test cycles, the articulation point may be variable. In other words, the articulation point can be shifted and displaced when the test bench is not in operation. In operation, the articulation point remains fixed, in particular, so as to apply a uniformly repeatable loading to the test body.

[0010] In one preferred embodiment of the test bench according to the invention there are provided multiple loading means which are attached to mutually spaced apart fixation points such that the rotor blade or the rotor blade segment can be subjected to identical or different prestress force. Thanks to multiple loading means, different points of application of the static force can be established along the entire length of the rotor blade. This further improves the realistic nature of the rotor blade testing. It may be provided that different prestress forces are exerted on the rotor blade at different loading means. Thus, for example, the static bending form of the rotor blade which occurs in real operation can be reproduced. On the whole, the set-up options of the test bench are improved in this way and the variation options are increased for the testing.

[0011] The loading means can be connectable to the rotor blade or the rotor blade segment by a flexible tension means, especially a cable or a chain, and/or by a rigid push/pull means, especially a coupling rod. The use of a flexible tension means has the advantage that the force direction can be varied easily and quickly. For example, the flexible tension means can be led across a deflection point, the position of the deflection point being variable. Thus, a prestress force can also be applied to the rotor blade having at least in part a horizontal force component. For example, the flexible tension means may be led at an angle from the rotor blade or from the rotor blade segment to the fixation point. The use of a rigid push/pull means also makes possible the direct application of compression loads to the rotor blade or the rotor blade segment.

[0012] The loading means may be formed by a motor, especially an electrically operated motor. In this way, the prestress force can be easily adjusted, for example, in dependence on the rotor blade or rotor blade segment being tested. Moreover, the prestress force may be varied with the aid of the motor in the test operation, for example, in order to reproduce different operating load variations.

[0013] The test bench according to the invention has a spring element which is connected to the loading means and which can be arranged between the loading means and the rotor blade or the rotor blade segment such that a spring force can be applied to the rotor blade or the rotor blade segment by means of the spring element in order to influence the oscillation behaviour. In this way, the static prestress force acting on the rotor blade or the rotor blade segment can be superimposed with a dynamic oscillation of the rotor blade or rotor blade segment, with the spring elements additionally increasing the frequency of the eigenvibration of the rotor blade or rotor blade segment. This shortens the time needed for the vibration testing. Thus, with the test bench according to the invention the vibration testing of a rotor blade or rotor blade segment can be performed in a relatively brief time, while at the same time taking into account the operating loads occurring in real operation.

[0014] In another preferred embodiment of the test bench according to the invention there is provided, between the loading means and the rotor blade segment, a jib which can be directly connected to the rotor blade segment and is connected to the loading means such that a static prestress force, whose force direction comprises at least one component oriented parallel to the rotor blade segment, can be applied to the rotor blade segment. In general, the test bench according to the invention is not only suitable for the testing of complete rotor blades, but also makes possible the testing of rotor blade segments, such as a rotor blade segment formed from a piece of a complete rotor blade including the rotor blade base. In this way, the length of the object being tested is shortened, while at the same time the eigenvibration frequency is increased. The required testing time is thus reduced. At the same time, thanks to the jib connected to the loading means it is possible to reproduce the forces in the rotor blade segment acting on the entire rotor blade, especially to simulate the effects of the operating loads acting on the rotor blade tip with the aid of a rotor blade segment. This ensures a realistic testing, even though the rotor blade not as a whole but only in a segment is subjected to the testing. For this, in particular, it is provided that a static prestress force is applied to the rotor blade segment having at least one component oriented parallel to the rotor blade segment. In this way, in particular, the centrifugal force acting on the rotor blade base will be reproduced.

[0015] According to a secondary aspect, the invention is based on the idea of indicating an arrangement having a test bench as previously described and a rotor blade or a rotor blade segment, especially for a wind turbine, wherein the rotor blade or the rotor blade segment is secured to the support structure and is connected to the loading means.

[0016] Another secondary aspect relates to a method for operating the test bench as previously described or the arrangement as previously described, wherein the prestress force of the loading means is set so as to reproduce the operational loads acting on the rotor blade or the rotor blade segment in real operation.

[0017] The invention shall now be explained more closely with the aid of exemplary embodiments making reference to the enclosed schematic drawings. There are shown

Fig. 1 a side view of a test bench according to the invention in a preferred exemplary embodiment, wherein the loading means is connected to the rotor blade across a deflected tension means; and

Fig. 2 a side view of a test bench according to the invention in another preferred exemplary embodiment, wherein the loading means is connected to a rotor blade segment across a tension means and a jib.

[0018] The test bench according to the invention finds application in particular in the vibration testing of rotor blades 10. In particular, the test bench is especially suitable for the testing of rotor blades 10 of wind turbines. The rotor blades 10 may be tested as a whole or in a segment.

[0019] The test bench has a support structure 11, which may be formed as a foundation rising up from a floor 15 and fastened to the floor 15. The stable support structure 11 has a fastening device for the rotor blade 10, which is not shown. The rotor blade 10 is joined to the foundation 11 in such a way that the rotor blade 10 extends substantially horizontally. This does not preclude the rotor blade 10 rising up at least partly from the horizontal, for example on account of the geometrical shape of the rotor blade 10. The statement that the support structure 11 is suitable for substantially horizontal fastening of the rotor blade 10 merely indicates that the rotor blade 10 is disposed freely about the floor 15 in terms of its length during the testing process. The rotor blade 10 is fastened to a side surface of the support structure 11 like a cantilever beam.

[0020] During the testing process, the rotor blade 10 is excited in vibrations in order to simulate the cyclical loads occurring in the real operation. The excitation of the vibrations occurs preferably by an excitation unit, which is designed in the exemplary embodiment of Fig. 1 as a cable winch 22. Alternatively, it may be provided that the excitation unit is secured to the rotor blade 10 as an unbalance exciter 12.

[0021] The cable winch 22 generally forms a loading means 31 for applying a static prestress force to the rotor blade 10. The cable winch 22, which may have an electric drive, can apply a prestress to the flexible tension means 17 which is connected to the rotor blade 10. The flexible tension means 17 or cable, especially a wire cable, transmits the prestress force applied by the cable winch 22 to the rotor blade 10, so that the latter is statically loaded perpendicular to its longitudinal axis. Instead of a flexible tension means 17 it is also possible to use a rigid push/pull means, such as a coupling rod. In this way, compression loads can also be transmitted to the rotor blade 10.

[0022] In general, the cable winch 22 used as the loading means 31 ensures that the entire rotor blade 10 can be subjected to a static load during the testing process, and with different prestresses at different holders 16 it is possible to simulate for example the buoyancy force occurring in operation or more generally the static operating loads. This improves a realistic simulation or testing in which the static and cyclical loads are superimposed on each other.

[0023] In the test bench of Fig. 1, the tension means 17 or cable is deflected on a deflection roller 19 and led horizontally to the cable winch 22, so that the test bench has a compact construction. For reasons of clarity, only a single tension means 17 is represented. In actuality, several such tension means 17 as well as loading means 31 may be arranged along the rotor blade 10.

[0024] Between the rotor blade 10 and the cable winch 22, especially between the deflection roller 19 and the cable winch 22, there is arranged a spring element 13. The spring element 13 comprises a cylinder 24, in which a piston 23 travels. A compression spring 13a extends between the piston 23 and a cylinder base 24a. The piston 23 has a piston rod 23a, which is coupled to the tension means 17 or cable. The cable runs across the cable roller 22, which is firmly connected to the floor 15. The firm connection between the cable roller 22 and the floor 15 forms an articulation point 14 of the tension means 17.

[0025] The cylinder 24 is likewise coupled to a cable 17, which is led across a deflection roller 19 to a holder 16. The holder 16 can be connected to a rotor blade 10 or is connected to the rotor blade 10 during the testing process. The spring element 13 or the spring assembly comprising the compression spring 13a, the cylinder 24 and the piston 23 is arranged substantially horizontal between the cable roller 22 and the deflection roller 19. In this way, the support structure 11 can have a relatively low height, without impairing the spring travel path of the spring element 13.

[0026] In the exemplary embodiment of Fig. 1, the spring element 13 is coupled to a single holder 16. Alternatively, it may be provided that two or more holders 16, especially 3 or 4 of them, are connected by a loading harness 18 to an individual spring element 13. This is indicated in Fig. 1 in the region of the blade tip 10b of the rotor blade 10.

[0027] In order to reduce the time needed for a test, it is proposed that the rotor blade 10 is coupled by at least one spring element 13 to the floor 15. In this way the stiffness is increased, so that the eigenfrequency is increased. Thus, a predefined number of oscillations can be performed in a relatively short test period. The positioning of the spring element 13 between the rotor blade 10 and the floor 15 can be done in various ways.

[0028] With the proposed test bench, several different simulation parameters can be easily adjusted. Thus, for example, it is possible, by adjusting the prestress force, i.e., by increasing the cable tension, to shift the centre position of the possible bending lines. In other words, the centre position of the bending lines can be changed by shifting the base points or articulation points. Furthermore, the proposed test bench enables a setting of individual, especially predetermined target bending lines. The form of the bending lines is determined by the spring stiffnesses of the spring elements 13. The spring stiffnesses of the individual spring elements 13 may be set differently. In particular, the spring stiffnesses can be set differently for spring elements 13 engaging at points on the rotor blade 10 situated next to each other along the span of the rotor blade 10. By specific adapting of the spring stiffnesses, different individual bending line curves can be set and used for the test operation. If a hydropneumatic cylinder is used as the spring element 13, it is also conceivable to regulate the spring stiffnesses during the test operation, so that the bending line can be corrected and fine tuned. Thus, deviations of the system parameters may be balanced out in the course of the testing process.

[0029] In general, the adjusting of a predetermined bending line can be made possible by a test bench for a rotor blade 10 or a rotor blade segment 20, especially a rotor blade 10 or a rotor blade segment 20 for a wind turbine, with a support structure 15 and at least one excitation unit, wherein one axial end of the rotor blade 10 or the rotor blade segment 20 can be fastened to the support structure 15 and the excitation unit for exciting an oscillation of the rotor blade 10 or the rotor blade segment 20 can be connected to the rotor blade 10 or the rotor blade segment 20, while multiple spring elements 13 are provided spaced apart from each other in the longitudinal direction of the rotor blade 10 or rotor blade segment 20, being arranged respectively between a fixed articulation point 14 and the rotor blade 10 or the rotor blade segment 20 and having different spring stiffnesses, such that a predetermined target bending line can be adjusted.

[0030] A further reduction in the test time can be achieved by using for the testing, instead of an entire rotor blade 10, a rotor blade segment 20, i.e., a rotor blade 10 which has been shortened by the blade tip 10b. Such a rotor blade segment 20 is also called a blade stump 20a. Due to the shorter length of the rotor blade segment 20 as compared to the entire rotor blade 10, the eigenfrequency is increased and therefore so is the testing speed. The forces acting on the blade tip 10b during the testing of a complete rotor blade 10 can be reproduced by design features of the test bench.

[0031] Fig. 2 shows such a variant of the test bench, in which instead of a complete rotor blade 10 a rotor blade segment 20 is fastened to the support structure 11. The rotor blade segment 20 comprises a portion of the rotor blade leaf as well as the rotor blade base 10a. Through holders 16 the rotor blade segment 20 is coupled to loading harnesses 18. A spring element 13 is arranged respectively between the loading harnesses 18 and each articulation point 14 on the floor 15.

[0032] A jib 21 is fastened to the blade stump 20a of the rotor blade segment 20. The jib 21 extends substantially perpendicular to the rotor blade segment 20 and is connected to a flexible tension means 17, especially a cable. The connection between the jib 21 and the tension means 17 or cable occurs indirectly across a spring element 13. The cable engages at an angle with the jib 21. Thus, the flexible tension means 17 applies not only a vertical, but also a horizontal force component to the rotor blade segment 20. The load acting on the rotor blade segment 20 that would exist if the entire rotor blade 10 were present can thus be reproduced.

[0033] The excitation of the oscillation occurs in the exemplary embodiment of Fig. 2 by an unbalance exciter 12, which is mounted at the level of the jib 21 on the rotor blade segment 20. A different arrangement of the unbalance exciter 12 is possible. Moreover, instead of an unbalance exciter 12 it is possible to use a different excitation unit. Corresponding excitation units or actuators are known to the skilled person.

[0034] Because of the short length and the correspondingly low weight of the rotor blade segment 20 as compared to a complete rotor blade 10, the eigenfrequency is increased at the same time. In this way, the testing of a complete rotor blade 10 can be simulated on the rotor blade segment 20, and this in a shorter time than is possible with conventional methods.

[0035] Basically, multiple holders 16 may be arranged along the rotor blade 10. Holders 16 are preferably arranged at regular intervals between the rotor blade base 10a and the rotor blade tip 10b. The holders 16 are connected to the spring elements 13, wherein each time an individual holder 16 can be coupled to an individual spring element 13. Alternatively, two holders 16 can be coupled to an individual spring element 13, for example via a loading harness 20. Moreover, it may be provided that an individual holder is connected to an individual spring element 13, wherein several combinations of holder 16 and spring element 13 are connected to a single articulation point 14. The individual combinations of holder 16 and spring element 13 are brought together with a loading harness 18 and connected for example by a rigid push/pull means 18 or a coupling rod or a flexible tension means 17 or a cable to the articulation point 14.

[0036] In order to reproduce the bending line of the rotor blade 10 which occurs in real operation, it has furthermore proven to be advantageous for the spring elements 13 arranged along the rotor blade 10 to have respectively lower spring stiffnesses with increasing distance from the foundation 11. Thus, on the whole, the spring elements 13 may have different spring stiffnesses. The spring element 13 closest to the rotor blade tip 10b preferably has the lowest spring stiffness. On the contrary, the spring element situated closest to the rotor base 10a preferably has the highest spring stiffness.

[0037] Accordingly, the static prestress force can be varied along the rotor blade or the rotor blade segment. For example, multiple loading means 31, especially cable winches 22, may be arranged along the rotor blade, applying different prestress forces to the rotor blade 10 or the rotor blade segment 20. The magnitude of the prestress forces may increase toward the rotor blade tip 10b or the blade stump 20a, for example. This faithfully reproduces the actually occurring static loads due to buoyancy forces acting by virtue of the oncoming flow against the rotor blade 10 in operation.

[0038] The test bench is basically suitable for the testing of all kinds of rotor blades 10 or similar winglike elements or generally elongated, bending-flexible structural parts. For example, with the test bench according to the invention, aircraft wings or airfoils could also be subjected to a vibration testing. Especially preferable is the use of the test bench for the testing of rotor blades 10 for wind turbines, especially rotor blades 10 of different length and design. The test bench is altogether flexible in use and also comprises various loading harnesses 18 or holders 16 adapted to different rotor blade cross sections.

List of reference symbols [0039] 10 Rotor blade 10a Rotor blade base 10b Rotor blade tip 11 Support structure 12 Unbalance exciter 13a Compression spring 13 Spring element 14 Articulation point 15 Floor 16 Holder 17 Flexible tension means 18 Loading harness 19 Deflection roller 20 Rotor blade segment 20a Blade stump 21 Jib 22 Cable winch 23 Piston 23a Piston rod 24 Cylinder 24a Cylinder base 31 Loading means

Claims (8)

1. Prøvebænk til et rotorblad (10) eller et rotorbladsegment (20) til en vindmølle - omfattende en støttestruktur (15), hvortil det er muligt at fastgøre en aksial ende af rotorbladet (10) eller af rotorbladsegmentet (20), og - mindst en excitationenhed (12, 21), som kan forbindes til rotorbladet (10) eller rotorbladsegmentet (20) med henblik på at fremkalde en oscillation af rotorbladet (10) eller rotorbladsegmentet (20), hvor et belastningsorgan (21, 31) er fastgjort til et leddelingspunkt (14) og kan forbindes til rotorbladet (10) eller rotorbladsegmentet (20) til udførelse af testen således at en statisk forstresskraft, hvis kraftretning omfatter mindst en komponent orienteret vinkelret til rotorbladet (10) eller rotorbladsegmentet (20), kan tilføres til rotorbladet (10) eller rotorbladsegmentet (20), kendetegnet ved, at prøvebænken har et fjederelement (13), som er forbundet med belastningsorganet (31) og kan arrangeres mellem belastningsorganet (31) og rotorbladet (10) eller rotorbladsegmentet (20) således at en fjederkraft kan tilføres til rotorbladet (10) eller rotorbladsegmentet (20) ved hjælp af fjederelementet (13) med henblik på at påvirke oscillationsvirkningen.

2. Prøvebænk ifølge krav 1, kendetegnet ved, at der forefindes adskillige belastningsorganer (31), som er forbundet til indbyrdes adskilte leddelingspunkter (14), således at rotorbladet (10) eller rotorbladsegmentet (20) kan udsættes for identiske eller forskellige forstresskræfter.

3. Prøvebænk ifølge krav 1 eller 2, kendetegnet ved, at belastningsorganeme (31) kan forbindes med rotorbladet (10) eller rotorbladsegmentet (20) ved hjælp af et fleksibelt trækspændingsorgan eller ved hjælp af stive tryk/trækorganer.

4. Prøvebænk ifølge krav 3, kendetegnet ved, at de fleksible belastningsorganer er et reb eller en kæde og/eller de stive tryk/trækorganer er en koblingsstang.

5. Prøvebænk ifølge et af de foregående krav, kendetegnet ved, at belastningsorganeme (31) består af en motor.

6. Prøvebænk ifølge et af de foregående krav, kendetegnet ved, at der mellem belastningsorganerne (31) og rotorbladsegmentet (20) er tilvejebragt en kranarm (21), der kan blive forbundet direkte til rotorbladsegmentet (20) og er forbundet til belastnings-organerne (31) således at en statisk forstresskraft, hvis kraftretning omfatter mindst en komponent orienteret parallelt med rotorbladsegmentet (20), kan påføres til rotorbladsegmentet (20).

7. Arrangement omfattende en prøvebænk ifølge et af de foregående krav og et rotorblad (10) eller et rotorbladsegment (20) til en vindmølle, hvor rotorbladet (10) eller rotorbladsegmentet (20) er sikret til støttestrukturen (15) og er forbundet med belastningsorganerne (31).

8. Fremgangsmåde til drift af en prøvebænk ifølge et af kravene 1 til 6, eller et arrangement ifølge krav 7, hvor forstresskraften af belastningsorganeme er indstillet således til at reproducere den funktionsbelastning virkende på rotorbladet (10) eller rotorbladsegmentet (20) under virkelig driftsituation.