JP4572399B2 - Axial plug-in dovetail segment for securing a closure bucket to a turbine wheel and its mounting method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an axial plug-in dovetail attachment between a bucket and a turbine rotor wheel, in particular fixing a final or closure bucket of a series of axially inserted buckets on a turbine rotor wheel. To dovetail segments inserted axially.
[0002]
[Prior art]
An axial plug bucket, or rotor blade, is assembled on the turbine wheel by sliding the bucket along the rotor axis and into the meshing dovetail of the turbine wheel. In conventional assemblies, the turbine bucket has a radially inward projecting male dovetail for mating engagement with a radially inward facing female dovetail of the turbine wheel. The wheel dovetails are spaced circumferentially around the wheel. Turbine wheel axial plug buckets have been found to be very satisfactory in assembly and use.
[0003]
[Problems to be solved by the invention]
However, certain turbine designs require an integral cover or shroud at the bucket tip. Generally, shrouds have partially overlapping protrusions that are nested with the shrouds of adjacent buckets. For example, some shrouds may have a generally Z shape when viewed radially inward. When this bucket is assembled continuously around the wheel using an axial plug-in dovetail system, it is assembled one adjacent previous shroud, generally the first assembled bucket and one last. However, the protrusions on the bucket prevent the assembly of the last axial plug-in bucket from the upstream or downstream side of the wheel. The shroud protrusions that prevent this cannot be removed because the shrouds must be in contact with each other in order to maintain a continuous circumferential coupling of the buckets at their tips during use. Thus, there is a problem in securing the final or closure bucket with the shroud to an otherwise completed wheel assembly by an axial plug-in assembly method.
[0004]
[Means for Solving the Problems]
In accordance with the present invention, the axial difference that allows the final or closure bucket to be easily secured to the rotor wheel after all buckets except the final closure bucket are secured to the rotor wheel by the axial insertion method. A built-in dovetail segment is provided. The present invention is particularly useful for securing the final bucket to the rotor wheel in an axial insertion scheme where the shroud at the bucket tip prevents axial insertion and fixation of the final bucket. In order to achieve the foregoing, an axial plug-in dovetail segment is provided having generally radially opposed male dovetails extending generally axially. The rotor wheel includes a normal female dovetail at circumferentially spaced positions around the wheel, including a circumferential position that receives the final bucket. However, instead of having a protruding male dovetail for engaging in a complementary relationship with the female dovetail of the rotor wheel at the final bucket position around the wheel, the final bucket includes a female dovetail. The radially inner male dovetail in this dovetail segment is the same as the male dovetail geometry in the bucket except the final bucket. The male dovetail on the opposite or radially outer side of the segment has a generally complementary shape with the female dovetail of the final bucket.
[0005]
To assemble the bucket against the rotor wheel, a bucket with a conventional male dovetail is inserted axially into the female dovetail of the rotor wheel. This insertion takes place continuously around the rotor wheel. Once all buckets are fixed to the rotor wheel except the last bucket, the final bucket is then inserted radially between adjacent buckets, one before the first assembled bucket and the last bucket. It can basically be placed on the wheel between the assembled buckets. Once the final bucket is properly positioned, the axial plug-in dovetail segment is inserted axially to engage the final bucket and the female dovetail of the rotor wheel, respectively. By allowing the final bucket to be inserted radially, the shroud of the final bucket can be nested radially with the cover of the adjacent bucket to form a continuous circumferential connection of the cover. Maintain the integrity of the integrated cover design.
[0006]
In a preferred embodiment according to the present invention, a rotor wheel with at least one axially plugged female wheel dovetail, a bucket with a female bucket dovetail adjacent to its radially inner end, and a bucket into one wheel dovetail. A turbine having an axial plug-in dovetail segment for securing to the shaft, generally extending axially and being axially received in a bucket dovetail and a wheel dovetail, respectively, generally axially A turbine is provided that includes a segment body having elongated, generally radially opposed, male dovetails.
[0007]
In another preferred embodiment according to the present invention, a rotor wheel comprising axially inserted female wheel dovetails circumferentially spaced from each other, and a wheel at each circumferential position of the wheel dovetails In a turbine having a plurality of buckets, a method of mounting one of the buckets on a wheel, the step of providing a female dovetail at the radially inner end of one bucket and fixing the one bucket and the wheel together To do so, a method is provided that includes inserting a segment having male dovetails that are generally radially opposed to each other axially and into one of the bucket dovetail and the wheel dovetail.
[0008]
In yet another preferred embodiment according to the present invention, a rotor wheel comprising an axially inserted female wheel dovetail circumferentially spaced from each other, and fixed to the wheel In a turbine having a predetermined number of buckets, a method of mounting the buckets, wherein the plurality of buckets are provided in a plurality of buckets at least one smaller than the predetermined number of buckets in order to fix the plurality of buckets to the wheel. Inserting the dovetails axially into a corresponding number of female wheel dovetails, and fixing the one dovetail segment substantially radially opposite male dovetails to the female A method comprising: inserting a dovetail and a female dovetail of one bucket respectively. That.
[0009]
The main object of the present invention is therefore to allow the final bucket with the cover to be assembled radially, while using the axial plug-in dovetail so that the shroud integrity can be maintained, around the rotor wheel. To provide a bucket for a wheel dovetail design for an integral shroud covered bucket while completing a circumferentially extending cover.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
With reference to the drawings, and in particular with reference to FIG. 1, a portion of a rotor wheel 10 is shown, which forms part of a turbine. The rotor wheel 10 is rotatable about an axis and has a series of female dovetails 12 spaced circumferentially around the circumference of the wheel. The female dovetail 12 extends axially, i.e. parallel to the axis of the rotor wheel, and receives a mating male dovetail 14 formed at the inner end of the bucket 16. The bucket 16 constitutes a series of blades or vanes, and receives the action of the hot gas in the turbine flow path to rotate the rotor wheel. Each radially inner end of the bucket 16 is provided with a male dovetail 14 that allows the axial insertion of the bucket relative to the female dovetail when assembling the bucket onto the rotor wheel.
[0011]
The buckets 16 also include shrouds or covers 18 at their radially outer ends that contact each other in the final assembly and form a continuous circumferential shroud assembly around the bucket tip. Of course, the cover 18 rotates together with the bucket 16 and the rotor wheel 10. As shown, the cover 18 is generally Z-shaped when viewed in the radial direction, and therefore engages, ie, nests, with an adjacent cover. Although a Z-shaped cover shape is preferable, a cover shape other than the Z shape may be used. For example, the cover can have a straight beveled edge. The specific shape of the cover is largely determined by the torsion and curvature of the bucket 16 that causes a circumferential shift between the front and rear edges of the bucket.
[0012]
As previously indicated, the male dovetail 14 of the bucket 16 is inserted axially into the female dovetail 12 when the bucket is assembled to the rotor wheel. Thus, the bucket 16 is assembled continuously around the wheel. For example, the first bucket 16a is assembled to the rotor wheel 10 by moving the male dovetail 14a axially into the female dovetail 12a. The next bucket 16b is similarly assembled to the rotor wheel 10 by moving the male dovetail 14b axially into the female dovetail 12b of the rotor wheel. It will be appreciated that the covers 18a and 18b in the buckets 16a and 16b are nested within each other upon such axial insertion, respectively. The other buckets are fixed to the rotor wheel continuously around the wheel 10 in the same manner, and finally the last previous bucket 16x inserts the male dovetail 14x into the female dovetail 12x. By doing so, it is mounted on the rotor wheel 10. Thus, it can be seen that the buckets are inserted axially into the rotor wheel and mounted completely around the rotor wheel, with the cover 18 being nested with respect to each other, except for one final bucket. Let's go. However, from the study of FIG. 1, the final or closure bucket 16y cannot be inserted into the rotor wheel from any axial direction because the cover 18y cannot pass through the opening defined by the adjacent covers 18a and 18x. You will understand. Thus, another type of connection and assembly procedure is required to mount the final bucket 16y onto the rotor wheel 10.
[0013]
In order to accomplish this, instead of providing the final bucket 16y with a male dovetail similar to the male dovetail 14 at the radially inner end of the other bucket 16, the final bucket 16y is provided along its radially inner end. A female dovetail 20 extending in the axial direction is provided. Further, as best shown in FIG. 2, an axial plug-in dovetail segment 22 is provided to couple the final bucket 16y to the rotor wheel 10 with a female dovetail connection 12y. Needless to say, this dovetail connection 12y is identical to the dovetail connection 14 spaced circumferentially around the rotor wheel 10. The axial plug-in dovetail segment 22 includes protruding male dovetails 24 and 26 along both radial sides of the segment, and the segment is axially spaced by a distance corresponding to the axial length of the male dovetail of the bucket 16. Extending in the direction. The male dovetail 24 radially inward of the segment 22 has a generally complementary shape with the female dovetail 14y, while the dovetail 26 radially outward of the segment 22 is the female dovetail of the final bucket 16y. 20 and the shape of a complementary relationship as a whole. By using the axial plug-in dovetail segment 22, the final bucket 16 y is assembled from the radial direction, the first bucket 16 a assembled to the rotor wheel 10 and the last one assembled to the rotor wheel 10. It can be placed between the previous bucket 16x. It can be seen that by inserting the bucket 16y in the radial direction, the radially inner base of the bucket can be easily placed between the radially inner bases of the adjacent buckets 16a and 16x. Further, the cover 18y of the final bucket 16y is nested between adjacent bucket covers 18a and 18x. In order to secure the final or closure bucket 16y to the rotor wheel 10, the axial plug-in dovetail segment 22 engages the segment's male dovetail with the final bucket 16y and the female dovetail of the rotor wheel 10, respectively. Pushed in the axial direction.
[0014]
Referring to FIG. 2, the geometry of the male dovetail 24 radially inward of the segment 22 is the same as the female dovetail 12 of the rotor wheel. That is, the dovetail hooks 25 are substantially complementary to each other. Similarly, the radially outer male dovetail 26 of segment 22 is complementary in shape to the female dovetail of the final or closure bucket 16y. That is, the male dovetail hook 27 is substantially complementary to the female dovetail hook. Note also the protrusions or tongues 28 in the segment 22. These tongues 28 provide a tangential constraint at the mating final or closure bucket female dovetail. Of course, the hooks 25 and 27 engage the corresponding hooks with the wheel dovetail and the female dovetail of the final bucket in the final assembly.
[0015]
Although the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, the invention is not limited to the disclosed embodiments, but conversely, the appended claims It should be understood that various modifications and equivalent arrangements included in the technical scope and technical scope of the present invention are intended to be protected.
[Brief description of the drawings]
FIG. 1 is a partial perspective view showing the connection between a bucket and a rotor wheel in addition to the axial plug-in dovetail segment of the present invention used to secure a final bucket.
FIG. 2 is an end view of an axial plug-in dovetail segment.
FIG. 3 is a perspective view of an axial plug-in dovetail segment.
[Explanation of symbols]
10 Rotor Wheel 12 Female Dovetail 14 Male Dovetail 16 Bucket 18 Cover 20 Bucket Female Dovetail 22 Segment 24 Radial Inner Male Dovetail 25, 27 Hook 26 Radially Outer Male Dovetail

Claims (6)

A rotor wheel (10), a plurality of axial plugin that may each secured to the rotor wheel (10) by a first male dovetail which is inserted into the first female dovetail of the rotor wheel (12) (14) A turbine comprising buckets (16a, 16b,... 16x) such that each bucket is telescopically engaged with a shroud (18) of an adjacent bucket to form a continuous circumferential shroud assembly. (I) so that the attached shroud telescopes with the shroud of the adjacent axial plug-in bucket. An additional bucket (16y) configured to be attached to the rotor wheel from a radial direction, with a radially inner end An additional bucket (16y) with a second female dovetail (20), and (ii) a shape and rotor complementary to the second female dovetail (20) at the radially inner end of the additional bucket (16y) A second male dovetail (22) having a complementary shape with the first female dovetail (12) of the wheel (10), inserted into the first and second female dovetails (12, 20) A turbine , further comprising a second male dovetail (22) by which an additional bucket (16y) can be attached to the rotor wheel (10) . The second male dovetail (22) is a segment body having radially opposite male dovetails (24, 26), with one dovetail (24) protruding at each side of the segment body. The turbine according to claim 1, comprising two hooks. Each of said shroud, according to claim 1 or claim 2, wherein the benzalkonium provided adjacent shroud and partially overlapping projections turbine. The rotor wheel (10) comprising a first Mesuda Buteru axial plugin which are spaced apart from one another circumferentially around the rotor wheel (12), a method of mounting a turbine bucket, Each of the first female dovetails (12) is configured to receive a plurality of buckets (16a, 16b,... 16x, 16y) one by one and attach to the rotor wheel (10), each bucket comprising: A shroud (18) configured to telescopically engage a shroud (18) of an adjacent bucket to form a continuous circumferential shroud assembly, the method comprising:
Providing a second female dovetail (20) at a radially inner end of a last bucket (16y) of the plurality of buckets ;
A first bucket for attaching each of the remaining buckets (16a, 16b, ... 16x) to the rotor wheel (10) at the radially inner end of the remaining buckets (16a, 16b, ... 16x) of the plurality of buckets. Providing a male dovetail (14);
Each of the first male dovetails (14) is inserted axially into the first female dovetail (12) and the remaining buckets (16a, 16b,... 16x) of the plurality of buckets are inserted into the rotor wheel (10). Attach to the stage
Plugging the last bucket (16y) of the plurality of buckets from the radial direction toward the rotor wheel such that its associated shroud telescopes with the shroud of an adjacent axial plug-in bucket;
A second male dovetail (22) is inserted axially into the first female dovetail (12) and the second female dovetail (20) of the last bucket (16y) of the plurality of buckets; Fixing the last bucket (16y) and the rotor wheel (10) of the plurality of buckets to each other . The second male dovetail (22) is a segment body having radially opposite male dovetails (24, 26), with one dovetail (24) projecting to each side of the segment body. The method of claim 4 including one hook. 6. A method according to claim 4 or claim 5, wherein each of the shrouds comprises a protrusion that partially overlaps an adjacent shroud.

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