Patent Application
20130302169
The invention relates to a rotor assembly for an axial turbine, in particular having a propeller-shaped rotor for a tidal power plant or a wind power plant having horizontal axis of rotation.
Tidal power plants having a horizontally aligned drive shaft, which revolves on a nacelle, and which is driven by a propeller-shaped turbine, are known and correspond to the design of wind power plants in horizontal rotor construction. For tidal power plants, the rotors of axial turbines of this type are either implemented as units having free flow around them or are encased by a jacket housing having Venturi geometry for flow acceleration. The rotor assembly described hereafter may also be transferred to further axial fluid-flow machines, such as fans.
For efficient energy utilization of slow currents in bodies of water, such as continuous ocean currents or tidal currents, large-scale rotors are required. Corresponding requirements result in the field of wind power, in particular for offshore plants. High forces and torques result therefrom on the region of the rotor blade attachment at the hub, which is in rotationally-fixed connection to the drive shaft. Correspondingly, the highly loaded components for the rotor blade attachment must be designed with a sufficient safety reserve for tidal power plants, since the cyclic variations of the tidal current caused by the phase of the moon are strongly overlaid by weather influences. Thus, depending on the waves, the wind direction, and the existing topography on the floor of the body of water for the respective plant location, meteorologically influenced currents occur, which result in a fluctuating load on the rotor.
Furthermore, a simplified plant concept having rigidly linked rotor blades is preferable for tidal power plants because of the accessibility for maintenance work, which is more difficult. In many cases, a device for rotating the plant around a vertical axis is additionally omitted and instead a rotor having rotor blades which can have bidirectional incident flow is used. This has the result that upon the occurrence of the overload, the rotor blades cannot be transferred by means of a pitch angle adjustment into the vane position, as is typically the case in the design used for wind power plants. The entire plant also cannot be rotated out of the current. Accordingly, a high standard results for the structural stability of the rotor blade attachment for tidal power plants, which results in heavy, large-scale, and expensive fastening components.
The heretofore known rotor design for axial turbines of tidal power plants is directed to a modularly constructed rotor, for which the individual rotor blades are installable separately on a hub. For this purpose, the hub has receptacles for blade fastening sections of the rotor blades. Such blade fastening sections are typically applied cylindrically, wherein a transition region to the profiled rotor blade sections, which interact with the current field, having higher structural stability is provided. For this purpose, reference is made, for example, to WO 2010/125478 A1. The cylindrical blade fastening sections typically have a diameter which is less than the chord length of the directly adjoining profiled rotor blade sections and is greater than the profile thickness in this region. There is thus a constriction, from which a notch effect results in the event of a load of the rotor blades, which must be secured by additional structural reinforcements.
Furthermore, the known blade fastening sections typically have on the hub-side end a fastening flange, which is used to form a screw connection between the blade fastening section of the rotor blade and the hub part of the revolving unit adjoining thereon. Such a rotor blade fastening is disclosed for wind power plants by U.S. Pat. No. 6,305,905 B1, for example. Corresponding fastening flanges for rotor blades on a hub of a tidal power plant result from GB 2467226 A, wherein a flange-shaped blade fastening section, which is formed in one piece with the profiled rotor blade section, is covered by means of a fastening ring for securing on the hub part. Reference is made to U.S. Pat. No. 5,173,023 and GB 502409 for further rotor blade attachments.
The present invention is based on the object of specifying a rotor assembly for an axial turbine having a plurality of individually installable rotor blades, which is distinguished by a high structural stability of the rotor blade fastenings and by an efficient force and torque transmission to an adjoining drive shaft. In addition, a rotor blade design is desired, which allows simple replacement of individual rotor blades. Furthermore, the rotor assembly is to be used in particular for operating a tidal power plant and is preferably to be suitable for implementing an axial turbine which can have bidirectional incident flow. The rotor arrangement must be able to absorb in particular asymmetrical load peaks which only act on individual rotor blades and must be simplified both in design and manufacturing. Furthermore, an installation method for such a rotor blade assembly is sought.
The present invention is achieved by the following features: a rotor assembly, comprising: a driveshaft having an assigned axis of rotation, which establishes an axial direction and a circumferential direction; a rotor having a plurality of rotor blades, which each comprise a profiled rotor blade section, which can have incident flow in the axial direction, and a blade fastening section; wherein each blade fastening section comprises a first contact region and a second contact region and the first contact region is at least indirectly supported on the blade fastening section of a first adjacent rotor blade and the second contact region is at least indirectly supported on the blade fastening section of a second adjacent rotor blade; the blade fastening sections are fastened in a formfitting manner and/or by means of a screw connection on the driveshaft, so that there is a connection between rotor blade and drive shaft on an axial end face of the blade fastening section, which is opposite to an axial terminus face on the driveshaft in the installed position; and for each rotor blade, the transition from the profiled rotor blade section to the blade fastening section has an external contour which is free of constrictions; the invention is characterized in that intermediate elements having an elastic intermediate layer are provided between the blade fastening sections of adjacent rotor blades.
The inventors have recognized that instead of fastening individual rotor blades to a hub, the carrying capacity of a rotor blade mount increases by omitting an integral hub component. According to the invention, individual hub segments are assigned to the replaceable rotor blades. These hub segments form blade fastening sections, which mutually support one another at least in the circumferential direction and at least indirectly.
Preferably, for rotors which can have bidirectional incident flow, not only pressure forces in the circumferential direction between the blade fastening sections are mediated, but rather additionally traction forces in the circumferential direction and axial force components are absorbed by a detachable connection of adjacent blade fastening sections. A screw connection and/or a formfitting connection preferably comes into consideration as the detachable connection, so that in the event of plant maintenance, individual rotor blades can be separately adjusted or replaced. For an advantageous embodiment, the blade fastening sections form a segmented hub part after the execution of the installation on the drive shaft due to the interaction with the respective adjacent blade fastening sections.
Each rotor blade of the rotor blade assembly according to the invention comprises a profiled blade section and a blade fastening section, which is preferably materially joined thereto, and which is supported on and/or detachably connected to a corresponding blade fastening section of an adjacent rotor. The profiled rotor section of the rotor blades represents the part of the rotor blade which interacts with the current field in a usable manner. In the event of a drive by a current in a body of water, the profiled rotor blade section is accordingly the hydrodynamically active part of the rotor blade having an adapted blade profile. In the case of a rotor which can have bidirectional incident flow for a tidal power plant, symmetrical profiles are used for this purpose, wherein an elliptical geometry can be provided for a double-axis symmetrical profile, for example. Alternatively, point-symmetrical profiles having a profile bulge, i.e., reflexed trailing edge profiles, can be used.
Each rotor blade particularly preferably has a one-piece embodiment of the assigned profiled rotor blade section and the assigned blade fastening section. The rotor blade can be produced from GFRP (glass fiber reinforced plastic) or CFRP (carbon fiber reinforced plastic) material or from steel, wherein contact regions on the blade fastening sections, which are used for force transmission to blade fastening sections of an adjacent rotor blade, are preferably reinforced by embedding abrasion-resistant materials, for example, a coupling element made of metal. For a further advantageous design, the blade fastening sections are produced as cast parts. Profiled rotor blade sections which are manufactured from steel, CFRP, or GFRP are materially joined thereon.
For an alternative embodiment, blade stubs, which form a first part of the profiled rotor blade section, are materially joined on the blade fastening section, wherein a second part of the profiled rotor blade section is detachably connected to the blade stub. The transition from the first part to the second part of the profiled rotor blade section can be embodied as an intended breakpoint to secure the entire plant from severe destruction in case of overload. Furthermore, the possibility exists of providing this transition region with an elasticity to implement a bending-rotating coupling of the rotor blade.
The blade fastening sections are fastened in a formfitting manner and/or by means of a screw connection to a drive shaft of the rotor assembly, so that each individual rotor blade is connected in a rotationally-fixed manner to the drive shaft. This connection can be conveyed through one or more of the intermediate elements, so that the rotationally-fixed linkage of the rotor blades is at least indirectly provided. For the rotor blade assembly embodied according to the invention, only a part of the forces and torques introduced from the profiled rotor blade sections are transmitted to the respective connection of the rotor blades to the drive shaft, since a further part of the force action is absorbed by the mutual support of the adjacent blade fastening sections.
For a preferred embodiment, the connection between rotor blade and drive shaft is implemented on an axial end face of the blade fastening section, which in the installation position is opposite to an axial terminus face on the drive shaft. Due to the incident flow on a rotor blade, in particular shear loads arise in the axial direction, which result in force components in the circumferential direction on the contact regions of adjacent blade fastening sections. For this reason, for an advantageous embodiment of the invention, each blade fastening section comprises a first contact region and a second contact region as well as the above-described third contact region to the drive shaft. The first contact region and the second contact region are preferably spatially partitioned. The first contact region and the second contact region alternatively adjoin one another and merge into one another.
The first and the second contact regions are established by respective interaction with the directly adjacent rotor blade. For a first embodiment, the first contact region is at least indirectly supported on the blade fastening section of a first, directly adjacent rotor blade and the second contact region is accordingly at least indirectly supported on the blade fastening section of a second, directly adjacent rotor blade. A rotor, having axial flow from an axial direction, of an axial turbine can thus be implemented in leeward operation. For a rotor which can have bidirectional incident flow, which is capable of both leeward and also windward operation, the first contact region and the second contact region preferably have means for the detachable connection to the respective adjoining blade fastening section of the adjacent rotor blade. These means can be implemented in the form of a screw connection and/or as a formfitting connection.
The contact regions are particularly preferably displaced into the intermediate blade regions, which are less mechanically loaded. These intermediate blade regions are thus defined in that their angular offset in the circumferential direction to a partition plane between adjacent rotor blades is at most ±30° and preferably at most ±15°. The partition plane extends centrally between adjacent rotor planes, which are assigned to individual rotor blades and are respectively spanned by the axis of rotation of the drive shaft and a further straight line, which is characteristic for the transition from the profiled rotor blade section to the blade fastening section. In the simplest case, a rotor blade having a radial beam geometry is provided, i.e., the threading lines of the profiled rotor blade sections follow a straight line in the radial direction. For this case, a rotor plane is established by the threading line and the axis of rotation.
However, the case can occur that the profiled rotor blade sections extend in a sickle shape. An embodiment is thus conceivable for which the profiled rotor blade sections do extend in the rotor plane which is defined as axially-symmetrical to the axis of rotation, but the threading lines do not follow straight lines. Furthermore, it is conceivable that the profiled rotor blade sections are curved such that they leave the rotor plane. For such space-occupying applied profiled rotor blade sections, a characteristic point, for example, the point on the chord line at half profile depth, is selected to establish the rotor plane on a predetermined profile section in the transition from the blade fastening section to the profiled rotor blade section. A straight line extending through this point in the radial direction and also the axis of rotation then define the rotor plane.
In the case of a rotor having more than three rotor blades, the intermediate blade regions are preferably in an angular interval of 40-60% of the angle which is formed by a section of the rotor plane having rotor planes located adjacent to one another. For a rotor on which substantially higher shear forces than torsion forces act, the intermediate blade regions are less loaded in relation to the remaining regions of the blade fastening sections. The connecting elements for the blade fastening sections of adjacent rotor blades advantageously lie in this region. These can represent components which interlock in a formfitting manner, for example, and which are fastenable to one another by a relative movement in the axial direction of the rotor.
According to an advantageous embodiment, an elastic intermediate layer is provided between adjoining blade fastening sections, in particular the contact regions facing toward one another. Elastomeric materials having a high carrying capacity, which are typically used to implement seawater-proof plain bearings, come into consideration for this purpose. These materials are typically loadable with pressure and have a high abrasion resistance for a hard/soft pair. A certain relative movement of adjacent rotor blades, which arises because of impact loads, can be compensated for by the elastic intermediate layer.
For a refinement, it is conceivable to mediate the detachable connection between the blade fastening sections of adjacent rotor blades by way of additional intermediate elements. In contrast to the known hub components, however, these do not form an integral structure, but rather are implemented as separate components which are arranged spatially partitioned. For a refinement of the invention, these intermediate elements are capable of adapting the installation location of the rotor blades to the respective site. This allows the use of standardized rotor blades and a change of the rotor blade geometry, in particular the angle of attack of the profiled rotor blade sections, by a corresponding selection of the intermediate elements.
An embodiment is particularly preferred, for which the entirety of the blade fastening sections of the rotor in the fastened state encloses a central free region, which is used to accommodate a shaft part of a driveshaft adjoining the rotor. The contour of the central free region is particularly preferably designed such that it deviates from the circular contour and transmits the drive torque generated from the rotor through a form fit with a corresponding complementarily implemented shaft connecting part.
In addition to the displacement of the connecting elements into the less loaded intermediate blade regions, the design according to the invention allows the reduction of the notch effect in the transition from the profiled rotor blade sections to the blade fastening sections. This is achieved because the heretofore typical cylindrical design of the blade fastening sections for accommodation in a recess on a hub part is replaced by the assignment of a hub segment to an individual rotor blade. Large-scale blade fastening sections result therefrom, without the segmented hub part, which arises due to the joining together of the rotor blades, experiencing a size growth.
To reduce the notch effect, there are preferably no constrictions in the region of a radial section of the rotor blade which establishes a transition region between the profiled rotor blade sections and the blade fastening section. A transition region which results in a continuous tapering of the rotor blade above a limiting radius in the direction radially outward is particularly preferred. An alternative embodiment is also conceivable, for which the profile regions which are essential for structural stability, i.e., the profile lugs, protrude somewhat beyond the transverse extension of the blade fastening section on the profiled rotor blade section. The profile chord in this attachment region can exceed the transverse extension of the blade fastening section by up to 20%, without a substantial growth of the notch effect resulting.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
For the rotor blade 2.1, the profiled rotor blade section 3.1 is materially joined to the assigned blade fastening section 4.1 for the illustrated, preferred design. The further rotor blades 2.2, 2.3 are accordingly designed such that there is a material bond between the respective profiled rotor blade section 3.2, 3.3 and the assigned blade fastening section 4.2, 4.3. The rotor blades 2.1, 2.2, 2.3 can be produced from different construction materials. In addition to cast parts, steel and fiber composite materials based on GFRP and CFRP come into consideration for this purpose. Connecting different materials to implement the rotor blades 2.1, 2.2, 2.3 is also conceivable.
Each blade fastening section 4.1, 4.2, 4.3 comprises a first axial end face 24 and a second axial end face 25, which are formed by plate-shaped elements spaced apart from one another. The plate-shaped elements are connected by a terminus plate, which extends in the installed state in an axial sectional plane of the driveshaft 21, at a first contact region 7.1, 7.2, 7.3 and at a second contact region 8.1, 8.2, 8.3, so that a light-construction but torsion-resistant structure results, which offers easy accessibility for installation work through the side openings 32 in the box-shaped structure.
In the installed state, the first contact region 7.1, 7.2, 7.3 for a first rotor blade 2.1, 2.2, 2.3 is opposite to the second contact region 8.1, 8.2, 8.3 on the blade fastening section 4.1, 4.2, 4.3 of a respective directly adjacent rotor blade 2.1, 2.2, 2.3. The first contact regions 7.1, 7.2, 7.3 and the second contact regions 8.1, 8.2, 8.3, which face toward one another in the installed state, are used for the mutual support of the blade fastening sections 4.1, 4.2, 4.3 in the circumferential direction 23.
For the incident flow direction 28 shown in
A further embodiment is shown in
Furthermore, it is apparent from
Furthermore,
A further structural reinforcement results from an advantageous design of the transition regions 19.1, 19.2, 19.3 between the profiled rotor blade sections 3.1, 3.2, 3.3 and the blade fastening sections 4.1, 4.2, 4.3. The advantageous embodiment according to
In the installed state, the blade fastening sections 4.1, 4.2, 4.3 of the rotor blades 2.1, 2.2, 2.3, which are detachably connected to one another, form a segmented hub part 5, which has a central free region 14 for an advantageous embodiment. For the embodiment shown in
For the exemplary embodiment shown in
In addition, an embodiment is conceivable for which intermediate elements 13.1, 13.2, 13.3 which are adapted specifically for the plant are used, which implement a tilted setting of the rotor blades 2.1, 2.2, 2.3. The irregularities resulting for this case on the end face of the rotor 20, which faces toward the adjoining driveshaft 1, must be supported with appropriately adapted wedge elements for secure contact.
While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
1 driveshaft
2.1, 2.2, 2.3 rotor blade
3.1, 3.2, 3.3 profiled rotor blade section
4.1, 4.2, 4.3 blade fastening section
5 segmented hub part
6 fastening element
7.1, 7.2, 7.3 first contact region
8.1, 8.2, 8.3 second contact region
9.1, 9.2, 9.3 longitudinal axis
10.1, . . . , 10.6 formfitting fastening element
11.1, 11.2 threaded bolts
12.1, 12.2, 12.3 elastic intermediate layer
13.1, 13.2, 13.3 intermediate blade region
14 central free region
16 shaft connecting part
17.1, . . . , 17.n borehole
18.1, 18.2, 18.3 rotor blade intermediate spaces
19.1, 19.2, 19.3 transition region
20 rotor
21 axis of rotation
22 axial direction
23 circumferential direction
24 first axial end face
25 second axial end face
26 axial terminus face
27.1, . . . , 27.n threaded boreholes
28 incident flow direction
29.1, 29.2,
29.3, 29.4 force components
30.1, 30.2, 30.3 shear forces
31 lateral opening
32 partition plane
33 angular offset
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2011 013 547.2 | Mar 2011 | DE | national |
This is a continuation of PCT application No. PCT/EP2012/001019, entitled “ROTOR ARRANGEMENT FOR AN AXIAL TURBINE AND A METHOD FOR MOUNTING SAME”, filed Mar. 8, 2012, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2012/001019 | Mar 2012 | US |
| Child | 13943413 | US |
