Patent Application
20140255169
This invention relates in general to seals for multistage turbomachines and, more particularly, to an anti-rotation structure for a seal provided between adjoining disks in a multistage turbomachine.
In various multistage turbomachines used for energy conversion, such as turbines, a fluid is used to produce rotational motion. In a gas turbine, for example, a gas is compressed through successive stages in a compressor and mixed with fuel in a combustor. The combination of gas and fuel is then ignited for generating combustion gases that are directed to turbine stages to produce the rotational motion. The turbine stages and compressor stages typically have stationary or non-rotary components, e.g., vane structures, that cooperate with rotatable components, e.g., rotor blades, for compressing and expanding the operational gases.
The rotor blades are typically mounted to disks that are supported for rotation on a rotor shaft. Annular arms extend from opposed portions of adjoining disks to define paired annular arms. A cooling air cavity is formed on an inner side of the paired annular arms between the disks of mutually adjacent stages, and a labyrinth seal may be provided on the inner circumferential surface of the stationary vane structures for cooperating with the annular arms to effect a gas seal between a path for the hot combustion gases and the cooling air cavity. The paired annular arms extending from opposed portions of adjoining disks define opposing end faces located in spaced relation to each other. Typically the opposing end faces may be provided with a slot for receiving a sealing band, known as a “bellyband seal”, which bridges the gap between the end faces to prevent cooling air flowing through the cooling air cavity from leaking into the path for the hot combustion gases. The sealing band may be formed of multiple segments, in the circumferential direction, that are interconnected at lapped or stepped ends.
When the sealing band comprises plural segments positioned adjacent to each other, in the circumferential direction, the sealing bands may shift circumferentially relative to each other. Shifting may cause one end of a sealing band segment to increase the overlap with an adjacent segment, while the opposite end of the sealing band segment will move out of engagement with an adjacent segment, opening a gap for passage of gases through the sealing band. Hence, it is typically desirable to provide a mechanism for preventing relative circumferential shifting of the sealing band segments.
In accordance with an aspect of the invention, a turbine is provided comprising a plurality of stages, each stage comprising a rotatable disk and blades carried thereby. At least one pair of adjacent rotatable disks define an annular gap therebetween and have respective opposing sealing band receiving slots aligned with the gap. A sealing band is located in the opposing sealing band receiving slots to seal the annular gap, and the sealing band comprises band engagement structure. Disk engagement structure is defined in the pair of adjacent rotatable disks. The disk engagement structure extends axially into the pair of adjacent rotatable disks and circumferentially aligns with the band engagement structure. A clip member is positioned in engagement with the sealing band through the band engagement structure and in engagement with the pair of adjacent rotatable disks through the disk engagement structure. The clip member restricts movement of the sealing band in only a circumferential direction of the slots.
The band engagement structure may comprise a pair of circumferentially aligned band notches in opposing edges of the sealing band.
The clip member may comprise a U-shaped member having a pair of legs, each leg including an outer end extending through one of the band notches. The sealing band may include opposing radially outer and inner sides, and an attachment structure may be provided affixing the outer ends of the legs to the radially outer side of the sealing band. Further, the attachment structure may include a welded joint between the outer ends of the legs and the radially outer side of the sealing band.
The clip member may include a base portion extending between the legs adjacent to the radially inner side of the sealing band, the base portion having a length no greater than a distance between the legs.
The base portion may have a thickness in the radial direction that is about equal to a thickness of the sealing band.
The sealing band may include a hole located between the opposing edges of the sealing band, and a post may be affixed to the base portion and extend through the hole for retaining the clip member in engagement with the sealing band prior to the attachment structure affixing the outer ends of the legs to the sealing band.
The disk engagement structure may comprise a pair of circumferentially aligned disk notches in the pair of adjacent rotatable disks.
The clip member may comprise a substantially planar base portion and two legs, the legs cooperating with the band engagement structure and the disk engagement structure to prevent rotation of the sealing band. The clip member may be formed so as not to extend radially beyond the disk engagement structure.
In accordance with a further aspect of the invention, a turbine is provided comprising a plurality of stages, each stage comprising a rotatable disk and blades carried thereby. At least one pair of adjacent rotatable disks define an annular gap therebetween and have respective opposing sealing band receiving slots aligned with the gap. A sealing band is located in the opposing sealing band receiving slots to seal the annular gap. The sealing band defines opposing radially outer and inner sides and has opposing edges, and band notches are formed in the edges to define a band engagement structure. A pair of circumferentially aligned disk notches are formed in the pair of adjacent rotatable disks to define a disk engagement structure. The disk notches extend axially into the pair of adjacent rotatable disks and are circumferentially aligned with the band notches. A U-shaped clip member is provided including a base portion and a pair of legs. The base portion is positioned in engagement with the radially inner side of the sealing band and the legs include outer ends extending through the band notches and engaged in the disk notches to prevent movement of the sealing band in a circumferential direction within the slots. The base portion defines a width dimension in a circumferential direction of the slots that is no greater than a width dimension of the disk notches in the circumferential direction.
While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying Drawing Figures, in which like reference numerals identify like elements, and wherein:
In the following detailed description of the preferred embodiment, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, a specific preferred embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention.
Referring to
Disk cavities 26, 28 are located radially inwardly from the gas passage 24. Purge air is preferably provided from cooling gas passing through internal passages in the vane assemblies 16 to the disk cavities 26, 28 to cool blades 18 and to provide a pressure to balance against the pressure of the hot gases in the gas passage 24. In addition, interstage seals comprising labyrinth seals 32 are supported at the radially inner side of the vane assemblies 16 and are engaged with surfaces defined on paired annular disk arms 34, 36 extending axially from opposed portions of adjoining disks 20. An annular cooling air cavity 38 is formed between the opposed portions of adjoining disks 20 on a radially inner side of the paired annular disk arms 34, 36. The annular cooling air cavity 38 receives cooling air passing through disk passages to cool the disks 20.
Referring further to
Referring to
It may be noted that the radial openings 56, 58 in the disk arms 34, 36 are typically provided for engagement with a prior art anti-rotation structure (not shown) associated with a bellyband seal. For example, a known anti-rotation structure could be a block structure attached to the bellyband seal and extending axially into the openings 56, 58, where engagement between the anti-rotation structure and sides of the openings 56, 58 prevents or limits circumferential movement of the bellyband seal or segments of the seal. Such an anti-rotation structure is illustrated in U.S. Pat. No. 7,581,931, which patent is incorporated herein by reference. As is described below, the present invention provides an anti-rotation device capable of utilizing the existing disk arm structure, including utilizing the radial openings 56, 58 to prevent rotation of the sealing band 68.
Referring to
As seen in
In accordance with an aspect of the invention, it has been noted that prior anti-rotation assemblies incorporating an anti-rotation body welded to a sealing band formed stresses at the weld joint resulting in cracking and possible failure at the weld joint. It is believed that the mass of the anti-rotation body, with an associated substantial centripetal load applied to the anti-rotation body during operation of the engine, is one factor that has contributed to failure of weld joints in anti-rotation assemblies. Further, prior welded anti-rotation bodies included an engagement between the anti-rotation body and inwardly facing surfaces of the rotor disk arms, such engagement providing a restriction on radial movement of the anti-rotation body with a resulting restriction on radial movement of the sealing band, which is believed to have further contributed to stresses at the weld joints. Consequently, an aspect of the present invention includes forming the clip member 78 with a low mass that is also free to move within the disk notches 56, 58.
The low mass and unrestrained radial movement of the present sealing band assembly 46 is embodied by the clip member 78 being formed to effectively cooperate within the disk notches 56, 58 to limit circumferential movement of the sealing band 68, while also having preferred dimensions to only limit movement in the circumferential direction with a minimum of mass in the clip member 78 to minimize centripetal loading association with the clip member 78.
As seen in
In accordance with a particular aspect of the invention, the mass of the clip member 78 is minimized by forming a thickness dimension, TB, of the body portion 80 that is substantially thin. For example, the thickness, TB, of the body portion 80 is preferably substantially equal to the thickness dimension, TL, of the legs 82, 84. Further, the thickness, TB, of the body portion 78 may be close to, or slightly greater than, the thickness of the sealing band 68, such as within about 25% of the thickness of the sealing band 68. Accordingly, the thickness of the body portion 80 is preferably sufficient to provide adequate rigidity to the clip member 78 extending across the width of the sealing band 68 between the legs 82, 84, while minimizing the thickness to provide a low mass structure for coupling the legs 82, 84.
As may be seen in
The radial extent of the legs 82, 84 is sufficient to provide a structure for cooperating with the circumferential sides 54a, 54b and 56a, 56b (
With respect to the configuration of the sealing band assembly 46 described herein, it may be noted that provision of the weld joints 94, 96 as the attachment structure between the clip member 78 and the sealing band 68 substantially ensures that no detachable components, such as fasteners, are available to detach and potentially become destructive debris within the engine. Further, in accordance with an aspect of the invention, the integrity of the connection between the clip member 78 and the sealing band at the opposing weld joints 94, 96 is facilitated by providing a low mass clip member structure configured to reduce or minimize stress at the normally vulnerable weld connections through the provision of a low mass component that restrains movement in only the circumferential direction of the slots 52, 54.
Referring to
The mounting structure additionally includes a post structure 100 configured for threaded engagement with the aperture 98. The post structure 100 includes a threaded shaft 102 and a nut member 104 in threaded engagement on the shaft 102. In a pre-installation configuration of the sealing band 68, the threaded shaft 102 may be positioned through the hole 99 in the sealing band 68 and threaded into the aperture 98 of the cylinder 97, and an outer end of the threaded shaft 102 is prevented from passing through the hole by the nut member 104. During installation of the sealing band 68 into the slots 52, 54, the clip member 78 may be rotated 90 degrees from the position depicted in
It may be understood that the engagement of the cylinder 97 within the hole 99 in the sealing band can facilitate alignment of the clip member 78 to the desired position on the sealing band 68 prior to the welding operation. Further, it should be noted that the cylinder 97 is preferably formed with a height that is no greater than the thickness of the sealing band 68 to avoid providing structure above the sealing band 68 that could potentially be impacted by debris in the area outwardly from the disk arms 34, 36.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
