Patent Grant
8926269
The present invention relates generally to seals used in gas turbine engines and, more particularly, to an interstage seal configuration used to reduce secondary flows between rotor wheel-space cavities.
It is well known that turbines extract energy from a hot gas stream as it impinges on the turbine blades mounted on a rotor wheel or disk fixed on a shaft or rotor of an associated rotary apparatus such as a generator. The blades are in the form of airfoils manufactured from materials capable of withstanding extreme temperatures. The mounting and shank portions of the blades are typically made of the same material, but the rotor disk posts between the mounting portions (or dovetails) are made of less capable material. For this reason, it is important to protect the disk posts from the direct impact of the high temperatures of the hot gas stream. Therefore, the blades and adjacent vane elements of the turbine are provided with platforms which axially combine to define a circumferential boundary, thus isolating the radially inner mounting or shank portions from the hot gas stream.
Protection against high temperatures is equally important throughout the rotor cavity. However, it becomes even more pronounced in the interstage region of the high pressure portion of turbine where the boundary of the expanding hot gases comes close to temperature sensitive areas of the rotor cavity, such as the forward and aft cavities bounded by the disk post for the stage one blade wheel, the platform for the stage two stationary nozzle assembly, and by the disc post of the stage two blade wheel.
According to present practice, labyrinth-type seals are often used between the forward and aft cavities. Such seals are well known in the art and include a plurality of circumferential teeth which are contiguous with a circumferential sealing surface made from a high temperature resistant abradable material in, for example, honeycomb form, providing the sealing surfaces with which the labyrinth teeth contact and, due to the deformability of the honeycomb material, the sealing surfaces becomes deformed without injury to the teeth, thereby establishing a minimum clearance required under operating conditions. See, for example, U.S. Pat. No. 5,215,435. Such seals also prevent performance loss due to flow bypassing the stationary airfoils by flowing through the wheel space instead.
Traditional diaphragm and honeycomb carrier designs have a substantially constant inner diameter which requires more radial space for packaging, since the flowpath outboard of the seal is conical in shape. In addition, such designs also involve more intersegment leakage because there is a larger radial gap between the seal teeth on the rotor and the stationary nozzle due to the relatively thick carrier and larger radial height.
Alternatively, some designs have used a cylindrical, sheet metal carrier of uniform diameter, where steps are machined into the honeycomb material.
The problem here is that such machining without damaging the honeycomb material is difficult and, therefore, more expensive and time-consuming methods must be used.
There remains a need therefore, for an interstage seal of simpler construction that also provides improved clearances and sealing over the prior design.
Accordingly, in one exemplary but nonlimiting embodiment, there is provided a seal carrier for a seal used between rotating and non-rotating components comprising an arcuate sheet metal seal carrier body formed to include a stepped, conical configuration wherein an inner diameter at one end is larger than a diameter at an opposite end, with plural stepped sections defined by alternating radial and axial portions between the one end and the opposite end, each axial portion adapted to carry a seal element; and wherein mounting flanges are provided at the one end and the opposite end of the arcuate sheet metal seal carrier body.
In another exemplary but nonlimiting embodiment, there is provided an annular seal for use between rotating and non-rotating components of a gas turbine comprising an annular sheet metal seal carrier body formed to include a stepped, conical configuration wherein a diameter at a forward end is larger than the diameter at an aft end, with plural stepped sections defined by alternating radial and axial portions between said forward end and said aft end, each axial portion carrying a discrete seal element and wherein an outer surface of the annular sheet metal seal carrier body is provided with axially extending ribs, spaced circumferentially about the annular sheet metal seal carrier body.
In still another exemplary but nonlimiting embodiment, there is provided an annular seal for use between rotating and non-rotating components of a gas turbine comprising an annular sheet metal seal carrier body comprised of multiple arcuate segments, each segment formed to include a stepped, conical configuration wherein a diameter at a forward end is larger than the diameter at an aft end, with plural stepped sections defined by alternating radial and axial portions between the forward end and the aft end, each axial portion carrying a discrete honeycomb seal element; and wherein an outer surface of said annular sheet metal seal carrier body is provided with axially extending ribs spaced circumferentially about said annular sheet metal seal carrier body.
The invention will now be described in detail in connection with the drawings identified below.
With reference initially to
The forward and aft ends 22, 24 are provided with axially-extending mounting flanges 38, 40 that enable the segments to be slidably inserted within opposed grooves (not shown) in the stationary component.
The outer surface 20 of the seal carrier body, between the mounting flanges 38, 40, is formed with a substantially uniform diameter surface portion 42 with an annular groove 44 located adjacent the mounting flange 38 at the forward end 22. A forward edge 46 extends radially between the flange 38 and a location mid-way along the radial length of the forwardmost honeycomb seal element 32. As will be appreciated, this design requires more radial space for packaging, because it does not follow the contour of the flowpath outboard of the seal.
Reinforcement of the segments 50 of the seal carrier body 48 is provided by a plurality of stiffening features, for example, axially-aligned gussets or ribs 70 extending along the outside surface 54 of each of the axially-extending portions 64 and engaged by the respective radial shoulders 66. It will be appreciated that two or more similar arrangements of axially-oriented reinforcement ribs 70 may be found at circumferentially spaced locations on each seal carrier segment. The ribs taper substantially uniformly from the forward end to the aft end, consistent with the stepped taper of the seal carrier body.
Mounting flanges 74, 76 are formed at the forward and aft ends of the carrier body, the flanges bent back approximately 180° and received in grooves 78, 80 in inner shroud 82 of the stationary nozzle 84. This arrangement permits each segment 50 to be installed in the grooves 78, 80 of an associated nozzle segment, after which the nozzle segments are installed in sequence on the turbine case (not shown) until the full annular seal carrier body of
The stiffening ribs as described above enable the use of sheet metal for the carrier. It will be appreciated that circumferentially oriented ribs could also be used to provide a measure of circumferential stiffness. In addition, other stiffening features could be embossed in the sheet metal in combination with or as alternatives to the stiffening ribs.
It will be appreciated that the relative dimensions, including radial height and axial length of the seal engaging surfaces of the carrier body may vary for different applications. For example, the dimensions will depend largely on the location of the opposed seal teeth 98 on the opposed rotating component (e.g. rotor 100) relative to the non-rotating component (e.g., nozzle 102). Similarly, the carrier body is not limited to use with honeycomb seals, but may also support other known seal elements. The number of arcuate segments in each annular seal carrier body may vary from two to as many as about seventy, and preferably between sixteen and twenty-four.
The sheet metal seal carrier described herein has packaging and sealing benefits, and in addition, the seal carrier is less costly versus machined castings/forgings typically used for such carriers.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3514112 | Pettengill, Jr. | May 1970 | A |
| 3589475 | Alford | Jun 1971 | A |
| 3986720 | Knudsen et al. | Oct 1976 | A |
| 4213296 | Schwarz | Jul 1980 | A |
| 4257222 | Schwarz | Mar 1981 | A |
| 4314792 | Chaplin | Feb 1982 | A |
| 4466239 | Napoli et al. | Aug 1984 | A |
| 5044881 | Dodd et al. | Sep 1991 | A |
| 5096376 | Mason et al. | Mar 1992 | A |
| 5152666 | Stripinis et al. | Oct 1992 | A |
| 5215435 | Webb et al. | Jun 1993 | A |
| 5236302 | Weisgerber et al. | Aug 1993 | A |
| 5346362 | Bonner et al. | Sep 1994 | A |
| 5462403 | Pannone | Oct 1995 | A |
| 5950308 | Koff et al. | Sep 1999 | A |
| 7291946 | Clouse et al. | Nov 2007 | B2 |
| 7334983 | Alvanos et al. | Feb 2008 | B2 |
| 8182210 | Khanin et al. | May 2012 | B2 |
| 20060275107 | Alvanos et al. | Dec 2006 | A1 |
| 20070059158 | Alvanos et al. | Mar 2007 | A1 |
| 20090142189 | Kovac et al. | Jun 2009 | A1 |
| Entry |
|---|
| Search Report and Written Opinion from EP Application No. 12182825.5 dated Oct. 30, 2012. |
| Number | Date | Country | |
|---|---|---|---|
| 20130058764 A1 | Mar 2013 | US |
