Staggered seal assembly

The present invention relates to an improved labyrinth seal design, and more particularly to a labyrinth seal design in which a well-known linear seal design and a well-known staggered seal design are mixed.

Machines that utilize airflow, such as fans, turbines and compressors, typically have a rotating air seal that separates the high fluid pressure region and the low fluid pressure region within the machine. Due to the rotation, it is not possible to form a perfect seal that is 100% preventive of leakage between the high pressure area and the low pressure area. The fluid passage that leaks from the high pressure region to the low pressure region is called the "leakage flow path".

In the prior art, two types of seals have been used to reduce the amount of fluid passing through the leak flow path. The first type of seal uses a linear leak flow path and is called a linear seal. The linear leak flow path leaks more than other types of seals. However, it is easy to assemble and consists of parts that are considerably simpler and cheaper than other well-known seals.

The second type of seal used in the prior art is a staggered seal. The staggered seal forms a much more restricted flow path than the linear seal. In the staggered seal, the stationary element is provided with a series of fins, and the rotating element of the seal is also provided with a series of fins. The fins are staggered, with each fin on the rotating element adjacent to two fins on the stationary element. This allows the leak flow path to pass through a relatively complex and winding path, and the leak flow path is narrowed to reduce pressure leakage between the high pressure region and the low pressure region as compared to a linear design.

<p> The staggered seal design is relatively complicated to assemble due to the need to arrange the fins in the correct pattern and the small tolerances. In addition, the staggered seal uses relatively expensive parts and has a relatively large number of parts. The combination of these two features makes the manufacture and assembly of staggered seals considerably more costly than other relatively simple seal designs.</p>

<p> A seal assembly is disclosed having a rotating element housed within the stationary seal element. A staggered element is provided adjacent to the stationary seal element, and this staggered element also surrounds the rotating element. The stationary element has at least one fin extending radially inward towards the rotating element, and the rotating element has at least one fin extending radially outward from the rotating element. The staggered element has at least one fin extending radially outward from the rotating element to the stationary element.</p><p> Cylindrical seals with multiple notches and at least one fin are also disclosed. The seal is cylindrical with an internal through hole extending axially through the cylinder.</p><p> The above and other features of the invention are best understood by the following detailed description and drawings.</p>

<figref num="1">It is explanatory drawing of the labyrinth seal of the prior art using a linear leakage flow path.</figref><figref num="2">It is explanatory drawing of the labyrinth seal of the prior art using a staggered leakage flow path.</figref><figref num="3">It is explanatory drawing which shows the steam cycle compressor utilizing the improved staggered seal assembly.</figref><figref num="4">It is explanatory drawing which shows the hybrid staggered seal assembly of the steam cycle compressor of FIG. 3 in more detail.</figref><figref num="5">FIG. 5 is a notched explanatory view of a cylindrical seal used with the seal assembly of FIG.</figref><figref num="6">It is a perspective view of the cylindrical seal of FIG.</figref>

Figures 1 and 2 show the labyrinth seal of the prior art. FIG. 1 shows a labyrinth seal with a stationary element 10 that separates the high pressure region 20 from the low pressure region 22. The stationary element 10 surrounds the rotating element 30 in the radial direction. The rotating element 30 has a set of fins 32. These fins 32 are adjacent to the end 24 of the stationary element 10. The gap between the fin 32 and the rest element 10 is a leak flow path 40 that allows a portion of the fluid in the high pressure region 20 to leak into the low pressure region 22. The fins 32 and the leak flow path 40 in FIG. 1 are shown enlarged for illustration purposes.

Instead of the linear seal in Figure 1, some prior art systems use the staggered seal assembly shown in Figure 2. The staggered seal assembly has a stationary element 110 with fins 112 protruding radially inward towards the rotating element 130. The rotating element 130 also has fins 132, which extend radially outward toward the stationary element 110. The stationary element fins 112 and rotating fins 132 are arranged in a staggered pattern with gaps between them to form a complex leak flow path 140. The complex leak flow path 140 slows leakage from the high pressure region 120 to the low pressure region 122 compared to the linear leak flow path of FIG. Similar to FIG. 1, fins 112, 132 and leak channels are shown enlarged for illustration.

FIG. 3 schematically illustrates a steam cycle compressor 198 using the improved staggered seal assembly 200. The seal assembly 200 has a stationary element 210 that forms the seal and limits the air flow from the high pressure side 202 of the seal to the low pressure side 204 of the seal. The stationary element 210 is ring-shaped and surrounds the shaft 212. The stationary element 210 is held in place by contact with the thrust plate 230. The impeller 240 is attached to the shaft 212 and rotates with the shaft 212. The impeller 240 further provides a staggered element 340 (shown in FIG. 4) that assists in the formation of the seal. The seal assembly 200 has a leak flow path that allows some of the fluid on the high pressure side 202 to move through the gap between the rest element 210 and the rotor 212 to the low pressure side 204. There is.

As can be seen from FIGS. 3 and 4, the seal assembly 200 can be assembled by sliding the stationary element 210 along the shaft until the stationary element 210 reaches a fixed position. Subsequently, the thrust plate 230 contacts the rest element 210 and fixes the rest element 210 so that it does not move. Next, the impeller 240 is installed so as to contact the shaft 212 with the staggered element 340 (shown in FIG. 4) adjacent to the stationary element 210, and the leak flow path is further staggered. This installation technique makes it possible to configure the stationary element 210 as a single piece, reducing the cost of parts and the assembly time of the seal assembly 200 as compared to the conventional staggered seal design. Further, by making the stationary element 210 into a single piece, the stationary element 210 can be replaced when it is worn, and the life of the seal assembly 200 is extended.

The stationary element 210 and the shaft 212 separate the high pressure side 202 and the low pressure side 204 by various fins 310,320,330,340. The shaft 212 has a first shaft fin 310 and a pair of second shaft fins 320. The first shaft fin 310 extends into the notch 350 of the stationary element 210 to a position further away from the shaft 212. A pair of second shaft fins 320 extend from the shaft 212 towards the rest element 210 along the central portion 352 of the rest element 310. The stationary element 210 has a stationary fin 330 extending radially inward from the stationary element 210 toward the shaft 212. Adjacent to the stationary fin 330, a staggered element fin 340 is provided. The staggered element fins 340 extend radially outward from the shaft 212 into the second notch 354 of the stationary element 210 and are connected to the impeller. In other applications, the staggered element fins 340 can be connected to other components that are adjacent to the high pressure side 202 of the stationary element 210 and that rotate with the shaft 212.

The stationary element 210 is provided thinner in the radial direction in the notches 350 and 354 than in the central portion 352. This allows the fins 310,320,330,340 to form a staggered leak flow path (shown in FIG. 5) and facilitates the manufacture and assembly of the seal assembly 220 as compared to prior art staggered seal assemblies. The first notch 350 and the second notch 354 further have a first dimension rotor fin 310 (the first notch 350) and a staggered (second notch 354). Allows the element fins 340 to rotate freely without interfering with the stationary element 210. FIG. 4 shows a notched cross-sectional view of the stationary element 210, but in the actual staggered seal assembly 200, the stationary element 210 has a uniform shape and surrounds the rotor in the radial direction, and the cross-sectional shape is the same everywhere. (See Figure 6).

FIG. 5 is a partially enlarged view of the seal assembly 200, with a series of arrows indicating the leak path 400. The leak flow path 400 follows a staggered path around the fins 310,320,330,340 as it travels from the high pressure side 202 to the low pressure side 204 of the stationary element 210. This structure provides the advantages of the prior art staggered seal assembly (shown in Figure 2) by pushing the leaking fluid into the winding flow path, while at the same time providing the prior art linear seal assembly (shown in Figure 1). The ease of assembly can be maintained.

FIG. 6 shows the stationary element 210 in three dimensions. The stationary element 210 has a through hole 602 that fits into the shaft 212 when the stationary element 210 is installed, and a gap is formed between the stationary element fin 330 and the shaft 212. The first end 606 of the stationary element 210 has a first notch 350 and a third notch 604. The second end 608 of the stationary element 210 has a second notch 354 and a fourth notch 610. The third notch 604 and the fourth notch 610 are such that another stationary component of the seal assembly 200 (shown in FIG. 3) grips the rest element 210 and the shaft 212 rotates in the through hole 602. Sometimes it makes it possible to hold the stationary element 210 in a stationary position. The rest element fin 330 extends from the boundary between the second notch 354 and the central portion 352 of the rest element 210. In the first notch 350 and the second notch 354, the first rotor fin 310 (shown in FIG. 4) and the staggered element fin 340 (shown in FIG. 4) interfere with the stationary element 210. Allows you to rotate freely without.

Although one embodiment of the present invention has been disclosed, certain improvements are also included within the scope of the present invention, as will be appreciated by those skilled in the art. Therefore, in order to determine the true scope and content of the present invention, it is necessary to consider the following claims.

202 ... High pressure side 204 ... low pressure side 210 ... stationary element 212 ... shaft 230 ... Thrust plate 240 ... Impeller 310 ... 1st shaft fin 320 ... 2nd shaft fin 330 ... stationary fins 340 ... zigzag elements 350 ... notch 352 ... Central 354 ... 2nd notch