RU2287063C1 - Steam turbine labyrinth seal - Google Patents

Abstract

FIELD: mechanical engineering; steam turbines.

SUBSTANCE: proposed labyrinth seal for steam turbine contains sealing ring lip on shroud of blades of turbine rotor stage. Small cellular units are installed with sealing radial clearance relative to shroud lip. Holders of cellular units in turbine stator cage are made with roots T-shaped in longitudinal section of turbine. Each root is provided with ring sector installed in ring slot of turbine stator cage. Slot of cage is made T-shaped in longitudinal section of turbine. Diameter of cylindrical surface of ring sector of root enclosing cylindrical surface of stator cage from side of its ring slot exceeds diameter of enclosed surface of slot. Each holder is fixed in radial direction by minimum fit with clearance not exceeding 0.4 mm. Each holder is pressed to projection of slot owing to difference of arcs of holder and cage over location diameter.

EFFECT: improved reliability of seal at reduced cost of its manufacture.

5 dwg

Description

Technical field

The invention relates to a means of increasing the efficiency of steam turbines, limiting the flow of steam through the gaps between the bandage of the blades and the turbine stator.

State of the art

In steam turbines, for the sealing of gaps between the bandage of rotor blades and the stator parts of the turbine housing, various types of over-band seals have been used (Thermal and nuclear power plants, Handbook edited by V.A. Grigoryev and V.M. Zorin, 2nd edition, book 3, M .: Energoatomizdat, p.206 ... 208). For such seals, radial clearances are assigned in such a way as to prevent contact of the sealing combs with sharp edges against the mating solid sealing surface. Operating experience shows that, as a rule, it is not possible to avoid touching during all operating and emergency conditions during the overhaul period. The sharp edges of the combs become dull and the compaction efficiency decreases.

Over-band seals with honeycomb inserts have been used, for example, described in RF patent No. 2150627. In these seals, the radial clearance is chosen so small that in some turbine operating modes, touching the combs of the bandages of the blades on the honeycomb inserts is inevitable. Cell inserts consisting of cells are made of heat-resistant sheet material with a thickness of only 0.05 mm. Touching the scallops leads to the cutting of the grooves on the surface of the honeycomb insert without blunting the sharp edge of the scallop. The fixation of each honeycomb insert in the axial and circumferential directions is carried out by a finger-retainer, in the case of destruction of which, and it is impossible to exclude it for a long period of operation, the honeycomb insert is shifted back along the steam and it falls into the flowing part. This leads to a serious accident.

Usually a mount with a T-shaped ring groove (Thermal and nuclear power plants, Handbook edited by V.A. Grigoriev and V.M. Zorin, 2nd edition, book 3, Moscow: Energoatomizdat, p.206 ... 208, Steam and gas turbines. Atlas of structures, edited by Prof. S. A. Kantora, M .: Mashinostroenie, 1970, pp. 27 ... 30) is used in end and diaphragm seals. These seals consist of 4 or 6 segments, secured against rotation in the circumferential direction by 2 keys installed in the turbine connector. In the radial direction, the segments are pressed against the protrusion of the T-shaped annular groove. The segments of the end and diaphragm seals with a T-shaped annular groove are made so that the based diameters in the groove of the cage and on the segment have the same size. When cutting the end seal ring into segments, because of the cut thickness, it is impossible to produce 4 or 6 finished segments from one workpiece, and each sealing ring is supplemented by one segment from an additional workpiece, which makes the turbine manufacture more expensive.

Disclosure of invention

The invention solves the problem of increasing the reliability of the seal while reducing the cost of its manufacture.

The labyrinth seal for a steam turbine comprises at least one sealing ring scallop made or mounted on the bandage of the blades of the turbine rotor stage. With a radial clearance relative to the annular scallop bandage of the rotor stage vanes, fine-mesh cellular blocks are installed. Each of the holders is used to attach one or more small-cell honeycomb blocks.

Each of the holders of small-cell honeycomb blocks in the holder of the turbine stator is made with an annular sector of a T-shaped in a longitudinal section of the liner turbine. Each of the shanks is installed in the annular groove of the turbine stator holder. The groove in the cage has a T-shape in the longitudinal section of the turbine.

According to the invention, the annular sector of the shank of each holder of small-mesh honeycomb blocks is made with a diameter of a cylindrical surface covering the cylindrical surface of the stator holder from the side of its annular groove, exceeding the diameter of the covered cylindrical surface of the groove with the possibility of elastic deformation of the edges of the annular sector when moving it in the annular groove of the holder in the process mounting seals.

Due to these differences, each insert is fixed in the radial direction with a minimum (no more than 0.4 mm) fit with a gap between the groove in the insert shank and the protrusion of the ring groove of the cage. Moreover, each insert is pressed against the protrusion of the groove due to the difference in the curvature of the arcs of the insert and the holder based on the diameter.

Brief Description of the Drawings

The invention is further illustrated by a specific example of its implementation with reference to the accompanying drawings, which depict:

Figure 1 - patented seal, longitudinal section.

Figure 2 - section aa of figure 1.

Figure 3 - section BB of figure 1.

Figure 4 is a longitudinal section through the holder.

Figure 5 is a longitudinal section along the cage in the area of the groove.

The thickness of the edges of the annular sectors in figures 1, 2 and 4 is shown without observing the scale - a greater thickness than is necessary to ensure their elasticity when moving the holder in the annular groove of the holder during installation of the seal.

The implementation of the invention

The labyrinth seal for a steam turbine contains sealing ring combs 1. The comb 1 is made or installed on the band 2 of the blades 3 of the rotor stage 4 of the turbine. With a radial sealing gap 5 relative to the scallop 1, fine-meshed honeycomb blocks 6 are installed. Each of the holders 7 of the fine-meshed honeycomb blocks 6 in the ferrule 8 of the turbine stator 9 is made with an annular sector 10. Sector 10 is a part of a shank 11 of the holder 7 in the longitudinal section of the turbine of the turbine. Sector 10 is installed in the annular groove 12 of the casing 8. The groove 12 has a T-shape in the longitudinal section of the turbine shape.

The annular sector 10 of the shank 11 of each holder 7 is made with a diameter of the cylindrical surface 13 covering the cylindrical surface 14 of the sleeve 8 from the side of its groove 12, exceeding the diameter of the covered cylindrical surface 14 of the groove with the possibility of elastic deformation of the edges of the annular sector 10 when moving it in the annular groove 12 of the holder during installation of the seal.

The holder 7 is fixed in the circumferential direction by the pin 15. To prevent the pin 15 from falling out, the notch 16 is made. Figure 2 shows (without respecting the scale) that due to the difference in the diameters of the surfaces 13 and 14, the holder 7 in places 17, 18 and 19 abuts annular protrusion 20 of the holder 8. In the middle there is a gap of not more than 0.1 mm The holder 7 due to the elastic deformation of the edges of the annular sector 10 is constantly pressed against the protrusion 20. The friction from the clamp holder is small. This allows you to push it along the groove of the clip 8 with little effort.

Due to the difference in the width of the groove 21 and the width of the protrusion 20, the joint has a gap of not more than 0.4 mm, which also allows the seal to be assembled by pushing the holder 7 along the groove of the holder 8 and at the same time does not allow the holder 7 to have significant axial displacements.

When the turbine rotor rotates, the scallops 1, sealing the gap along which the steam flows, can touch the honeycomb blocks 6. The sharp edge of the scallop 1 cuts a groove in the honeycomb block 6 without blunting its sharp edge, i.e. honeycomb blocks allow you to automatically set the minimum possible radial clearance of the seal. An additional chamber is created in which expansion and turbulization of the flow of the flowing steam takes place, as a result of which the hydraulic resistance to flow increases. The result is increased turbine efficiency.

Holders 7 of small-mesh honeycomb blocks 6 for one turbine stage are made from one workpiece. This leads to lower costs. Fixing the holders in the groove of the holder eliminates their loss in the flowing part in case of breakage of the pin. Fastening each holder with a pin, instead of two keys along the turbine connector, eliminates the formation of an increased clearance at the ends in two places along the turbine connector.

Claims (1)

Labyrinth seal for a steam turbine containing a sealing ring comb made or mounted on the bandage of the blades of the turbine rotor stage, small cell honeycomb blocks installed with a radial sealing gap relative to the annular scallop bandage of the rotor stage vanes, holders of small-cellular honeycomb blocks in a turbine stator holder, each of which is made with a T-shaped annular sector in a longitudinal section of a shank turbine installed in an annular groove of a turbine stator holder, having a T-shape in a longitudinal section of a turbine, characterized in that the annular sector of the shank of each holder of small-mesh honeycomb blocks is made with a diameter of a cylindrical surface covering the cylindrical surface of the stator holder from the side of its annular groove, exceeding the diameter of the covered cylindrical surface of the groove, with the possibility of elastic deformation of the edges of the annular sector when moving it in the annular groove of the holder during installation of the seal .

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