Abstract:
A rotor blade for a wind turbine comprising a blade root to be fastened to a rotor hub, a blade tip opposite the blade root, a rotor blade longitudinal axis extending from the blade root to the blade tip, an inner rotor blade part on the near side of the blade hub, especially encompassing the blade root, and an outer blade part on the far side of the blade hub, especially encompassing the blade tip. The inner rotor blade part and the outer rotor blade part are joined to one another in a joining zone which forms a bulge in the rotor blade.

Description:
BACKGROUND 
       [0001]    Technical Field 
         [0002]    The present disclosure relates to a wind turbine rotor blade and to a wind turbine having such a rotor blade. The present disclosure moreover relates to a method for producing a wind turbine rotor blade. 
         [0003]    Description of the Related Art 
         [0004]    Wind turbines are known and the currently most common type of wind turbine is a so-called horizontal-axis wind turbine, usually having three rotor blades. The dimensions of such wind turbines are getting bigger and bigger, namely in particular they have a higher hub or axis height and a larger rotor diameter with a correspondingly larger generator and greater feed-in power. Larger rotor diameters mean larger rotor blades which need to be transported from where they are manufactured to the respective site of erection. In particular the need to transport such long rotor blades, which can now have lengths as great as approximately 60 meters, regularly makes it necessary to use multi-part rotor blades. 
         [0005]    Such multi-part rotor blades, which have at least two parts in the longitudinal axis, are known. For example, a type E-126 ENERCON wind turbine uses a rotor blade with a steel part close to the hub and a GFRP part remote from the hub. The structure is shown, for example, in U.S. Pat. No. 8,192,170. 
         [0006]    The use of multi-part rotor blades can make transport easier. There is furthermore a growing desire to construct rotor blades that are as light and thin as possible so as thereby to save costs, to be precise not only the costs of the blade but also the cost of the subsequent support structures of the wind turbine and also the cost of erecting the wind turbine. In this sense, rotor blades are today being increasingly optimized, wherein a particularly good aerodynamic design is of course also important and needs to be taken into account when constructing a rotor blade. 
         [0007]    WO2013/083451 shows an alternative of an assembled rotor blade consisting of a part close to the hub and a part remote from the hub, both parts being made substantially of GFRP. This example shows a very efficient solution for connecting the two rotor blade parts. Multiple connecting bolts are arranged in a peripheral row in the rotor blade, can be accessed there and in particular tightened and even prevent fatigue by virtue of pretensioining. This solution provides a particularly strong peripheral region at the connecting point of the two rotor blade parts, in which this connecting and bolting together is carried out by means of the said bolts. This shown connecting region which receives the multiple bolts must correspondingly absorb the entire load of the outer blade part, i.e., the one close to the hub. Both the corresponding connecting region at the rotor blade part close to the hub and the corresponding connecting region at the part of the rotor blade remote from the hub in practice have to absorb these forces completely and reliably. The force or load which occurs on these connecting regions also has to be introduced correspondingly into the respective part, i.e., the part of the rotor blade which is close to the hub or remote from the hub, respectively. The loads which need to be introduced can be considerable, which can sometimes also affect durability and at least be a potential point of weakness. The German Patent and Trademark Office has conducted a search as part of the priority application for the present application and found the following prior art: US 2011/0293432 A1, WO 01/42647 A2, WO 2006/ 002 621 A1, WO 2006/ 056 584 A1. 
       BRIEF SUMMARY 
       [0008]    One or more embodiments are directed to a rotor blade having a blade root for fastening to a rotor hub, and a blade tip. The blade tip is at the end of the rotor blade which is averted from the rotor hub, in other words radially to the outside relative to the rotor. A rotor blade longitudinal axis extends from the blade root to the blade tip. 
         [0009]    The rotor blade is multi-part and has a rotor blade inner part and a rotor blade outer part. The rotor blade inner part faces the blade hub, and can therefore be referred to as the blade part close to the hub, and comprises in particular the blade root. Correspondingly, the rotor blade outer part is averted from the blade hub, and can therefore be referred to as the blade part remote from the hub, and it comprises in particular the blade tip. The terms inner and outer relate here to the rotor and a radial direction. Inner, in other words radially inner, is towards the axis of rotation and outer, or radially outer, is to the outside relative to the axis of rotation. The rotor blade is preferably composed of only two parts, viewed in the longitudinal direction, to be precise of the rotor blade inner part which then has the rotor blade root, and of the rotor blade outer part which then has the rotor blade tip. Alternatively, however, the rotor blade tip can also, for example, form a separate part, but this is not the case here. As is also explained further below, other elements can also be present on the rotor blade or the rotor blade can be divided into further elements but these are preferably not further divided in the longitudinal direction. It is now proposed that the rotor blade inner part and the rotor blade outer part are connected to each other in a connecting region, and the connecting region forms a thickened portion in the rotor blade. The surface of the rotor blade is then therefore, not completely continuously from the blade root to the blade tip, a more or less straight but if need be slightly curved surface and instead has a markedly thickened portion in the connecting region. This thickened portion is essentially designed as a type of completely or partially peripheral web or wall. 
         [0010]    It preferably extends in a plane along the connecting region and hence transversely to the rotor blade longitudinal axis. It extends at least from high-pressure side to the low-pressure side and vice versa, in other words over the leading edge of the rotor blade. The trailing edge of the rotor blade is usually designed to be extremely sharp, at any rate in comparison with the leading edge of the rotor blade, and although the thickened portion can extend as far as there, it does not extend around this edge, at any rate not preferably. This thickened portion and this peripheral or partially peripheral web can have a beveled region so that it merges via this angled region with the remaining rotor blade surface of the corresponding side. For example, the surface of the rotor blade therefore extends, starting from the blade root and moving radially outwards, initially flat or if need be slightly curved, then meets this beveled region and rises correspondingly as far as the thickest or highest region of the thickened portion which likewise can have a certain width such as, for example, 10 to 30 cm or the like. The surface then runs down the slope to the essentially no longer thickened blade surface and extends from there in an essentially familiar fashion as far as the rotor blade tip. 
         [0011]    By virtue of this thickened portion it is now possible to produce a stable connection between the two blade parts, in other words the rotor blade inner part and the rotor blade outer part. It has been shown that this solution has very good aerodynamic properties. The thickened portion extends namely parallel to the expected airflows when the rotor blade is in operation. Because this thickened portion is arranged parallel to these airflows, it not only does not have a negative effect on the aerodynamics and these airflows but even has a positive effect. The situation can namely be facilitated by the airflows or any turbulence not drifting along the rotor blade, i.e., from the rotor blade hub to the rotor blade tip or vice versa. Instead a flow which is as laminar as possible and parallel is facilitated. 
         [0012]    At the same time it was also recognized that this thickened portion is advantageous despite a general desire to design rotor blades which are as thin as possible. However, the thickened portion does not change the aerodynamics and can, as described, on the contrary act as a boundary layer fence. Moreover, although a rotor blade which had the dimensions in the region of the thickened portion over its entirety would be too heavy, or at least undesirably heavy, the weight does not play a role in this connecting region. This is not only because the region is small relative to the total length of the rotor blade but also because the fastening between these two blade parts is thickened and hence shifted outwards, which creates better lifting conditions for the fastening and as a result can even be realized with less, or at least comparatively less material. 
         [0013]    Lastly, it was also recognized that a part of the fastening can take place in this thickened portion without there being any need for access from outside. This outward thickening is also helpful despite the fastening, in particular using screws, taking place on the inside. 
         [0014]    The connection between the rotor blade inner part and rotor blade outer part is preferably effected in the connecting region using screws and/or bolts. 
         [0015]    A solid connection can be achieved hereby and if necessary also tightened up at maintenance intervals. 
         [0016]    The thickened portion preferably rises by at least lcm, in particular by at least 2 cm, above the blade surface. Moreover or alternatively, the thickened portion thickens the rotor blade by at least one percent, in particular by at least two percent, relative to the profile depth or chord length in the connecting region. 
         [0017]    Moreover or alternatively, such a completely or partially peripheral thickened portion has an essentially constant width of 100 to 200 cm, in particular approximately 1.5 m. The desired stability and at the same time a boundary layer fence-type effect can be achieved hereby. 
         [0018]    An embodiment proposes that the rotor blade outer part is composed of an outer core and outer trailing edge box, and that the rotor blade inner part is correspondingly composed of an inner core and inner trailing edge box. Here too the terms outer and inner relate to the radial direction of the rotor, in other words the direction of the axis of rotation, towards the outside or inside respectively with respect to the axis of rotation. The rotor blade outer part and the rotor blade inner part are assembled in the region of the outer and inner core. The connecting means such as screws or bolts or the like are provided there. The outer and inner trailing edge boxes are then each attached only at their corresponding outer and inner core. The outer and inner trailing edge boxes are thus not, or not substantially, fastened to each other. 
         [0019]    The rotor blade and correspondingly the rotor blade outer part and the rotor blade inner part correspondingly have the thickened portion in the region of the outer and inner core, namely at the point where they are assembled. However, the thickened portion moreover extends at least partially from the outer and inner core, respectively, to the outer and inner trailing edge box, respectively, in order thereby to influence the aerodynamics positively. 
         [0020]    The inner and outer core can each take the form of a wound core and/or have an oval shape in cross-section. Providing a wound core means that the core is produced from wound layers, in particular that fiber materials, in particular fiber mats made of glass fiber or carbon fiber, are wound to produce the core in order thereby to produce a core of fiber-reinforced plastic. A particularly stable core can be produced as a result. An oval shape can make allowance for the forces which occur and be adapted successfully to the rotor blade which is to be produced. The oval shape also allows production by winding for a non-circular shape and an advantageous force distribution can be achieved. Nevertheless, the oval shape should not be selected to be too thin in order to be able ensure good stability in multiple directions. For this purpose, a ratio between the smallest and largest diameter of the oval of 1:1.2 to 1:2 is proposed, in particular from 1:1.4 to 1:1.7, in particular a ratio of approximately 1:1.5. Furthermore, a cross-section here refers to a cross-section transverse to the longitudinal axis of the rotor blade. 
         [0021]    Fastening means are preferably enclosed in laminate in the region of the thickened portion. Openings, passages and anchors or sockets for anchors are in particular provided already fixed or enclosed in laminate during the production of these elements. For example, multiple anchoring elements can be enclosed in laminate in the rotor blade outer part in the connecting region, in particular around the periphery. In addition or alternatively, fixtures and passages for screws or threaded bolts can be provided in the rotor blade inner part in the connecting region for connection to the anchoring elements. Uniform edges, bearing surfaces or the like can also be provided in the rotor blade inner part in order to receive fastening or connecting fixtures, to mention just a few examples. Likewise, the functionality of the rotor blade outer part and rotor blade inner part can also be swapped so that the anchoring elements can therefore be arranged in the rotor blade inner part and the said passages or supporting edges can be arranged in the rotor blade outer part. Alternatively, however, these same passages, namely bores and sockets for anchoring elements, can be introduced subsequently, in particular can be bored. A clean supporting edge, bores, slots or the like can also be milled at a later point in time. 
         [0022]    A fiber-reinforced plastic, in particular GFRP or CFRP, is correspondingly provided as essential material for the rotor blade outer part and the rotor blade inner part. These two rotor parts can of course have other materials but the essential material, in particular the material which gives them their profile, in particular the outer sleeve which defines the profile and to a large extent provides the stability, is manufactured from this material. The elements which are required in the connecting region for connection purposes, such as anchoring elements, pins and bolts, can, however, be manufactured from a different material, in particular from steel or another type of iron. 
         [0023]    An outer and an inner row of threaded rods are preferably provided in order to fasten the rotor blade parts to each other. The terms outer and inner hereby refer to the rotor blade such that the outer row extends continuously essentially directly below the surface of the blade, whereas the inner row extends continuously inside this outer row, i.e., closer to the center axis of the rotor blade. Good fastening of the two blade parts to each other can be achieved as a result. Moreover, the forces which occur can be better spread by this design with two rows. 
         [0024]    A threaded rod from the inner row and one from the outer row preferably in each case together form a pair of threaded rods which in turn are part of a fastening pair. Such a pair of threaded rods moreover has a common inner anchoring pin which extends transversely to the threaded rods and is anchored in the rotor blade inner part, and a common outer anchoring pin which likewise extends transversely to the threaded rods. The terms outer and inner here refer to the rotor blade parts so that the inner anchoring pin is thus anchored, namely inserted, in the rotor blade inner part and the outer anchoring pin is correspondingly anchored, i.e., inserted, in the outer rotor blade part. These anchoring pins here point essentially radially outwards with respect to the rotor blade surface, viewed from a rotor blade center axis. 
         [0025]    A corresponding connecting force can thus hereby be exerted between the two rotor blade parts by two anchoring pins which are used by two threaded rods. The two threaded rods essentially extend next to each other through these two anchoring pins and the anchoring pins have a corresponding length and thickness in order to be able to receive the threaded rods, in order to allow their force to absorbed by them and transmitted into the blade. 
         [0026]    According to an advantageous embodiment, one of the two anchoring pins is inserted essentially rigidly in a bore, the size of which, in particular the diameter, is adapted to that of the anchoring pin, the other fastening pin being arranged in an elongated opening which, in particular in plan view, is similar to or is a slot. Clamping means for the threaded rods can be provided in the region of this pin, which is arranged in the elongated opening, so that the threaded rods can be clamped herewith. 
         [0027]    The outer row of threaded rods, or a single row of threaded rods, is preferably arranged in the region below the thickened portion so that the thickened portion covers this row of threaded rods, in particular such that, in the absence of this thickened portion, this row of threaded rods would lie outside the rotor blade, or at least would be flush with or project from the rotor blade surface. 
         [0028]    A very good connection can thus be achieved between the two rotor blade parts, wherein at the same time advantageous aerodynamic properties can occur. 
         [0029]    An embodiment proposes that the threaded rods, in particular all of the threaded rods or all of the outer row, have a slight inclination with respect to the outer blade surface. Such an inclination means a range which in particular extends from 0.5 to 5 degrees, in particular is approximately 1 degree. As a result, the threaded rods and hence in particular the fastening pairs can advantageously be arranged such that the direction of the forces is particularly favorable and can be introduced particularly favorably into the blade parts and also such that access to the clamping means can be improved. 
         [0030]    Multiple fastening pairs are preferably provided and these have an inner anchoring pin, an outer anchoring pin and two threaded rods which are in each case provided with an expansion sleeve and a clamping means. The clamping means can in particular be a clamping nut, wherein the two anchoring pins are preferably arranged between the expansion sleeve, on the one hand, and the clamping means, on the other hand. 
         [0031]    The design is then such that initially a clamping sleeve is provided for each threaded rod and is attached to one of the two fastening pins. The threaded rod then extends from one rotor blade part, which can be the outer or inner part, to the other rotor blade part in which the other anchoring pin is then provided through which the threaded rod extends. Lastly, a clamping means is finally arranged on the threaded rod, in particular a clamping nut which can then be screwed against the anchoring pin in order thereby to pull the two anchoring pins towards each other and thus also pretension the expansion sleeve. It can thus be achieved that the clamping means engages directly with the threaded rod and an anchoring pin and yet an expansion sleeve is provided and can hold the pretension. 
         [0032]    According to an embodiment, the rotor blade is constructed such that the threaded rod, i.e., in particular each threaded rod, cannot, in the assembled state of the rotor blade, be removed but can be clamped. In particular the threaded rod is at least 40 cm long, preferably approximately 80 cm long. As a result, a corresponding gap can be achieved between the two anchoring bolts so that a lot of substance remains in the rotor blade to absorb the necessary forces. Moreover, it is also possible to provide a correspondingly long expansion sleeve when there is a long threaded rod. It has been proved that it is no longer necessary to remove such threaded rods after mounting and instead even the loss of threaded rods can be avoided. 
         [0033]    The two blade parts, i.e., the rotor blade inner part and the rotor blade outer part, are then connected such that a part of the fastening pair, in particular in each case an anchoring pin with two threaded rods and two expansion sleeves, can be already provided, in particular premounted, in one of the two blade parts, in other words for example the rotor blade outer part. Because the threaded rod in each case already sits in an expansion sleeve and additionally in an anchoring pin, it has a very clearly defined position and orientation. Preinstallation is thus readily possible. 
         [0034]    By virtue of this preinstallation, the two rotor blade parts can now be assembled such that the two threaded rods of each fastening pair each project into an elongated opening or recess which is similar to a slot. In succession, the other fastening pin can now be placed there first and then the clamping means, in particular clamping nuts, are arranged and lastly clamped as well. A fastening pair is moreover proposed, as has already been explained in at least one embodiment above in connection with the two-part rotor blade. 
         [0035]    A wind turbine is moreover proposed which has at least one rotor blade according to one of the above-described embodiments. The wind turbine can thus profit from the benefits of these rotor blades and be installed relatively cost-effectively as the rotor blades are supplied in two parts. 
         [0036]    A method for producing a rotor blade of a wind turbine is moreover proposed. This method comprises at least the step of producing a rotor blade inner part and producing a rotor blade outer part, including a connecting region with a thickened portion, and the method comprises the step of connecting the rotor blade inner part to the rotor blade outer part at an erection site of a wind turbine. The disclosure can thus advantageously be used to produce a rotor blade and as a result construct a wind turbine. 
         [0037]    During production, a barrier plate or barrier disc can be provided in the connecting region between the rotor blade outer part and rotor blade inner part relative to which the rotor blade longitudinal axis thus extends essentially perpendicularly. This barrier plate or barrier disc is here preferably dimensioned such that it projects above the thickened portion in the manner of a boundary layer fence. A boundary layer fence can thus be provided in a simple fashion. 
         [0038]    A method for producing a rotor blade of a wind turbine is moreover proposed, wherein in particular a rotor blade is produced as was described in at least one of the preceding embodiments. It is correspondingly also proposed that, before the rotor blade inner part is assembled with the rotor blade outer part, threaded rods are used for connection in one of the two rotor blade parts, in particular are in this respect used or premounted in each case together with an expansion sleeve. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0039]    The disclosure is now explained in detail below with the aid of exemplary embodiments by way of example with reference to the attached drawings, in which: 
           [0040]      FIG. 1  shows a wind turbine in a perspective view. 
           [0041]      FIG. 2  shows a portion of a connecting region of a rotor blade in which a rotor blade outer part and a rotor blade inner part are connected to each other. 
           [0042]      FIG. 3  shows a perspective portion of the connecting region according to 
           [0043]      FIG. 2 . 
           [0044]      FIG. 4  also shows a portion of a connecting region according to  FIG. 2  in a different view. 
           [0045]      FIG. 5  shows in a perspective view a portion of an inner core assembled with an outer core. 
           [0046]      FIG. 6  shows a rotor blade inner part in a perspective view. 
           [0047]      FIG. 7  shows a rotor blade outer part in a perspective view. 
           [0048]      FIG. 8  shows a connecting region of an inner core of a rotor blade inner part in a perspective view. 
           [0049]      FIG. 9  shows a portion of a rotor blade outer part in a perspective view. 
       
    
    
     DETAILED DESCRIPTION 
       [0050]      FIG. 1  shows a wind turbine  100  with a tower  102  and a nacelle  104 . A rotor  106  with three rotor blades  108  and a spinner  110  is arranged on the nacelle  104 . The rotor  106  is set in rotational motion by the wind and as a result drives a generator in the nacelle  104 . 
         [0051]      FIG. 2  shows a portion of a rotor blade  1  with a rotor blade inner part  2  and a rotor blade outer part  4 . The drawing also shows the division of the section of the rotor blade  1  shown into multiple more or less rectangular areas, which serves for the computational splitting-up into regions with the same material coordinate systems but does not need to explained in more detail here. 
         [0052]    Apart from that, the rotor blade inner part  2  and the rotor blade outer part  4 , which can also be referred to more simply as the inner blade  2  and the outer blade  4  respectively, are connected to each other in the region of a joint  6 . A separating disc or the like could also be arranged in this region as a boundary layer fence. 
         [0053]      FIG. 2  shows, in the region in the joint, a thickened portion  8  in which the blade wall  12  of the inner blade  2 , or  14  of the outer blade  4 , projects far beyond this thickened portion  8 . In this respect this thickened portion  8  forms a peripheral web or wall which has beveled regions  16  on both sides. 
         [0054]    A thickened portion  10  is also provided correspondingly on the inside. Both thickened portions  8  and  10  are produced by the application of material, here namely by laminating on GFRP. The advantageous thickened portion can thus also absorb compressive and tensile forces and consequently strengthen the rotor blade  1 , in particular in the region of the joint  6 . The width of the thickened portion  8  applied here is approximately 150 cm, taking into account the beveling of the thickened portion, namely of the material applied. The thickened or beveled portion has a width of approximately 1 meter. The blade walls  2  and  4  can, for their part, also have a slight taper, i.e., an inclination taper towards the thickened portion, but this is not part of the thickened portion. 
         [0055]    The whole thickened portion including the bevel  16  runs around the periphery for the part of the rotor blade  1  shown and here has a constant width. This applies to the region without the beveled region  16  and to the region with it. 
         [0056]    Bores  18  and elongated openings  20  for anchoring bolts are shown in  FIG. 2 , which essentially shows a view inside the cutaway rotor blade  1 . Outer anchoring pins  24  are arranged in the bores  18  and inner anchoring pins  24  are arranged in the elongated openings  20 . The reverse could also occur. 
         [0057]      FIG. 3  and  FIG. 4  show details of the connection, in particular for example a fastening pair  26  with an inner anchoring pin  22 , which is arranged in a bore  18 , and an outer anchoring pin  24 , which is arranged in an elongated opening  20 . The illustrative view in  FIGS. 3 and 4  shows further bores  18  and elongated openings  20  in the portion but without further fastening pairs  26 , but this only serves for illustrative purposes. In an assembled rotor blade  1 , all the bores  18  and elongated openings  20  are preferably equipped with fastening pairs  26 . 
         [0058]    The fastening pair  26  shown additionally has two threaded rods  28  which can also be referred to as expansion bolts or expansion threaded bolts. In any case, preferably expandable threaded rods are proposed here which can further assist the function of the expansion sleeves. 
         [0059]    Expansion sleeves  30  are correspondingly arranged at one end of the threaded rods  28 . Moreover, each threaded rod  28  has a clamping means  32 . Clamping now takes place such that the clamping means  32  are drawn onto their threaded rods  28 , as a result of which the threaded rod  28 , essentially according to the view in  FIGS. 3 and 4 , pulls the respective expansion sleeve  30  against the outer anchoring bolts  24 . The two anchoring pins are consequently pulled towards each other and the respective expansion sleeve  30  is moreover pretensioned. 
         [0060]    For this purpose, the inner anchoring pin  22 , and with it the clamping means  32 , can be reached through the elongated opening  20  and, in the assembled state, the connection can be tightened and hence pretensioning for the clamping sleeves achieved. It is, however, not possible to extract the threaded rods  28 .  FIG. 3  also shows that the elongated opening  20  is closed to the outside with respect to the outer surface  36  of the rotor blade  1  by a seal  34 . The fastening means, in other words in particular elements of the fastening pair, are thus protected against the effects of the weather, at least against rainfall. 
         [0061]      FIGS. 3 and 4  both also illustrate the thickened portion  8 , the outer thickened portion  8  and the inner thickened portion  10  respectively, wherein layers of material are not shown here. It can also be seen that the region of constant thickness  38  of the thickened portions  8  and  10  and the fastening pairs  26  are matched to each other. It can also be seen that both the region of constant thickness  38  and the thickened portion  8  are clearly delimited and have a width which is constant around all or part of their periphery. 
         [0062]      FIG. 5  shows, in a cutaway, an assembled inner core  42  and outer core  44 . Parts of these inner and outer cores  42 ,  44  also directly form the rotor blade surface and hence directly the rotor blade. In this respect, the portions of the rotor blade inner part  2  and the rotor blade outer part  4  in  FIGS. 3 and 4  are identical to the inner and outer cores  42 ,  44 . 
         [0063]    In this respect, much of what can be seen shown in  FIGS. 3 and 4  is also in  FIG. 5  but in an external view. In particular the thickened portion  8  can be seen and within it the bores  18  with the inner anchoring pins  22  contained inside. The elongated openings  20  shown in  FIGS. 3 and 4  cannot be seen in  FIG. 5  because of their cover  34 . The cover  34  is fitted into the surface such that it is not shown in  FIG. 5 . Lastly, the joint  6  can also be seen in  FIG. 5 , and  FIG. 5  also illustrates that the thickened portion  8  forms a peripheral region for these assembled inner and outer cores. The thickened portion  8  here has a constant width  40 . 
         [0064]    A highly efficient rotor can be obtained with the invention shown. A wind turbine with a nominal output of 3 MW can thus be produced which has a rotor diameter of only 115.7 m. The turbine can, however, be operated with a higher output, for example 3.5 MW. 
         [0065]    The rotor blade inner part  602  in  FIG. 6  comprises an inner core  642  and an inner trailing edge box  652 . The inner core  642  comprises a root region  640  for fastening to a rotor hub, and an inner fastening region  662  for fastening to an outer fastening region  664  of a rotor blade outer part  604 , as shown in  FIG. 7 . The rotor blade outer part  604  has an outer core  644  on which an outer trailing edge box  654  is arranged and fastened. When the rotor blade inner part  602  has been assembled with the rotor blade outer part  604  according to  FIGS. 6 and 7 , the inner trailing edge box  652  and the outer trailing edge box  654  are assembled such that they form a functional unit. A possible space or connecting gap between these two elements can optionally be allowed or covered in a simple fashion. The load-bearing fastening of the rotor blade inner part  602  and the rotor blade outer part  604  to each other, and the fastening of the rotor blade outer part  604  to the rotor blade inner part  602  is effected via the inner and outer fastening region  662  and  664 . 
         [0066]    In the case of the rotor blade outer part  604 , the outer core  644  can taper from the outer fastening region  664  to a blade tip  670  and thus provide its oval shape. The outer core  644  and the outer trailing edge box  654  can thus merge into each other. Any explanations about an oval shape of the outer core  644  relate in this respect to the region of the outer fastening region  664 , which refers not only to this embodiment but any oval outer core.  FIGS. 6 and 7  also show a thickened portion  608 ′ and  608 ″, which together form a common thickened portion when the rotor blade outer part  604  and the rotor blade inner part  602  are assembled. 
         [0067]      FIGS. 8 and 9  show, enlarged, the inner fastening region  662  and the outer fastening region  664 .  FIG. 9  shows in rudimentary fashion a further part of the outer trailing edge box  654 , wherein the counterpart thereto on the inner core  642  has been omitted for the sake of greater clarity. 
         [0068]    It can be seen in  FIGS. 8 and 9  that a double-row bolted connection is provided for connecting the two fastening regions  662  and  664 . In each case a reference pair of bores  672  is shown in both Figures, i.e., shown for both fastening regions  662  and  664 . These two reference pairs of bores then come to be positioned against each other, as intended, when the two fastening regions  662  and  664  are connected. 
         [0069]    An outer anchoring pin  624  is inserted into each bore  618  or transverse bore  618  for a connection. A connecting bolt  628 , which can also be referred to as a threaded rod, can in each case be pushed through the longitudinal bores  674  as far as the corresponding transverse bore  618  and there through the corresponding outer anchoring pin  624 . It can further be inserted through an expansion sleeve and then screwed into a fastening nut or the like, as can be seen essentially in the view in cross-section in  FIGS. 3 and 4 . Each transverse bore  618  and each outer anchoring pin  624  then comprise a pair of connecting bolts  628 . By means of this preparation, the outer fastening region  664  and the inner fastening region  662  can then be placed against each other so that the connecting bolts  628  are pushed into the inner longitudinal bores  676 . They can then be screwed, in particular optimally screwed, into the slots  620  shown. As a result, the two blade parts, namely the rotor blade inner part  602  and the rotor blade outer part  604 , can then be connected. The connecting bolts which have been thus inserted can then be screwed tight in the slots  620 , as is also illustrated essentially in  FIGS. 3 and 4 . 
         [0070]    The slots  620  are closed to the outside and can be accessed only from the blade interior or from the interior of the inner core  642 . The transverse bores  618  are each through bores and can be covered from outside by a cover  678  which is illustrated in a rudimentary fashion in  FIG. 9 .