The disclosure relates generally to rotor assemblies, and more particularly to blade or bucket mounting in turbine rotors.
A rotor includes a plurality of blades or buckets whose roots are typically mounted on a rotating body, such as a shaft or the like, often referred to as a wheel. Each blade or bucket root may include a profile that is typically shaped to be retained against radial motion when mounted in a groove in the body so that the blade may slide in the groove but not come out of the groove. For example, the blade root and groove may include complementary dovetails including a bucket or blade hook and a wheel hook that cooperate to retain the bucket dovetails in the groove. To enable insertion of the bucket roots into the groove, the blade hook region is typically cut to form an assembly gate. The assembly gate is generally one bucket width along the circumference. Special arrangements must be made to retain the blade(s) at the assembly gate. The assembly gate is typically cut through wheel hooks in the groove, which may reduce the load bearing capacity of the gate area. Additionally, natural frequencies of the rotor may be affected by the assembly gate, as may balancing of the rotor.
Embodiments of the invention disclosed herein may take the form of a blade mounting system that may include a blade including a bucket dovetail, the bucket dovetail including a blade hook portion. A wheel dovetail groove formed in a rotor may have a shape complementary to that of the bucket dovetail and include an assembly gate. The bucket dovetail may be configured to have a first orientation in which the blade hook portion will fit through the assembly gate and a second orientation in which the blade hook portion is retained by the wheel dovetail groove. In addition, the bucket dovetail may be configured to rotate between the first orientation and the second orientation at the assembly gate and to be restrained against rotation at other locations in the wheel dovetail groove.
Another embodiment may include a rotor blade mounting arrangement with a rotor that has a substantially cylindrical surface. A wheel dovetail may be formed in the rotor through the substantially cylindrical surface. The wheel dovetail may include a substantially circumferential groove in the rotor, a wheel neck shoulder, and an upper recessed area at an opening of the groove. A rotor blade may include a bucket dovetail configured to support the rotor blade and to be retained against radial movement in and by the wheel dovetail. A blade hook shoulder of the bucket dovetail may be configured to engage and be retained against exit from the wheel dovetail groove by the wheel neck shoulder. An upper shoulder of the bucket dovetail may be configured to at least partly overlie the wheel neck shoulder. An assembly gate may include a cut-out formed in the upper recessed area of the wheel dovetail groove. The cut-out may be configured to allow the blade hook shoulder to be inserted into the wheel dovetail groove in a first orientation of the bucket dovetail and to allow the upper shoulder to pass when the bucket dovetail is rotated into a second orientation.
Another embodiment may take the form of a rotor including a substantially cylindrical surface of a rotor body and a wheel dovetail including a substantially circumferential groove in the substantially cylindrical surface. A plurality of substantially identical rotor blades may each have a bucket dovetail with a blade hook portion. Each blade hook portion may have a first orientation in which the blade hook portion may be inserted into the groove and a second orientation in which the blade hook portion is retained in the groove and retained against rotation in the groove. Each bucket dovetail may include blade hook shoulders in the blade hook portion and upper shoulders in an upper portion of the bucket dovetail. Opposed wheel neck shoulders may be formed in the groove between a wheel hook portion of the groove and an upper portion of the groove, the wheel neck shoulders being configured to retain a respective blade hook portion of each rotor blade via respective blade hook shoulders. Upper recessed areas may be formed in the top portion of the groove and configured to retain respective upper shoulders of each bucket dovetail against rotation. An assembly gate in the groove may be configured to allow the upper shoulders of each bucket dovetail to pass when the bucket dovetail is rotated to a second orientation in which the bucket dovetail is retained in the groove.
Other aspects of the invention provide methods, systems, program products, and methods of using and generating each, which include and/or implement some or all of the actions described herein. The illustrative aspects of the invention are designed to solve one or more of the problems herein described and/or one or more other problems not discussed.
These and other features of the disclosure will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings that depict various aspects of the invention.
It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements between the drawings.
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
As indicated above, aspects of the invention provide a rotor blade arrangement and assembly method.
With reference to
As seen in
A cross section of an example of a bucket or blade 200 including a bucket dovetail 210 and a blade body 220 is seen in
As seen in
In embodiments, blade hook shoulders 214 may be configured to have a width at least as narrow as gap 126 in first orientation 230 to enable insertion of bucket dovetail 210 into dovetail groove 120. Upper shoulders 218 in embodiments may be configured to have a length and an angle selected so that in second orientation 240 they are held against rotation by upper recessed areas 128. Upper shoulders or bucket platform 218 may also have a width narrower than gap 126 in embodiments. Blade hook shoulders 214 may be configured to have a length and an angle selected so that in second orientation 240 they are held against movement out of dovetail groove 120 by wheel neck shoulders 124, but so that rotation from first orientation 230 to second orientation 240 is not impeded by blade hook shoulders 214. It may be that bucket dovetail 210 may be inserted anywhere along dovetail groove 120, but only at assembly gate 130 will bucket dovetail 210 be able to be rotated into second orientation 240.
As mentioned above, assembly gate 130 may include arcuate cut-outs 132, such as in upper recessed areas 128, to accommodate rotation of bucket dovetail 210. In embodiments in which a parallelogram shaped cross section is used for upper shoulders 218, arcuate cut-outs 132 may be diametrically opposed portions of a circle with a diameter equal to diagonal D of upper shoulders 218 and centered midway between upper recessed areas 128. When a smaller diagonal of upper shoulders 218 is used, rotation past second orientation 240 may be prevented by ends of upper shoulders 218. An offset between first orientation 230 and second orientation 240 may be equal to angle θ.
In the example shown in the FIGS., an offset between first orientation 230 and second orientation 240 may be equal to the smallest angle θ between adjacent sides of the cross section of upper shoulders 218. First orientation 230 may be that in which long sides of blade hook shoulders 214 are parallel to walls of dovetail groove 120, though this may vary depending on how much smaller the width of blade hook shoulders 214 is than gap 126. If angle θ is, for example, 65°, then a rotation of 65° may place bucket dovetail 210 in second orientation 240, which may bring short sides of upper shoulders 218 parallel to and, in embodiments, in engagement with walls in the upper recessed areas. Thus, the offset between first orientation 230 and second orientation 240 when a parallelogram shaped cross section having a smaller angle of 65° may be 65°.
Each bucket 200 may be slid along dovetail groove 120, in second orientation 240, to a desired position, and another bucket 200 may be inserted. This may be repeated until all but a final desired bucket 200 have been inserted into and positioned along dovetail groove 120. As seen in
With assembly gate 130 being formed in upper recessed areas 128, wheel neck shoulders 124 are left intact and substantially uniform throughout dovetail groove 120. Embodiments thus do not require cut-outs in wheel neck shoulders 124 and/or special blade attachment arrangements at assembly gate 130 as would be required by some existing solutions. This may, for example, enhance strength and structural integrity of rotor 100, and also may allow all rotor blades 200 in rotor 100 to be substantially identical, whereas existing solutions may require specialized rotor blade assemblies at assembly gates. In addition, assembly gate 130 may be sized so that it has a substantially negligible impact on balancing and natural frequencies of rotor 100, or so that compensation for presence of assembly gate 130 is easily achieved. Further, arrangements according to embodiments allow use of buckets 200 that are all substantially identical, thereby reducing manufacturing, handling, engineering, design, and other costs associated with typical arrangements requiring special buckets at assembly gates.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
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Number | Date | Country | |
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20130170996 A1 | Jul 2013 | US |