JPS62153504A - Shrouding segment - Google Patents

Abstract

PURPOSE:To aim at the improvement of turbine efficiency by placing within a shrouding segment a sheet metal provided with cooling orifices, and then providing a cooling passage on the moving-blade side peripheral wall. CONSTITUTION:Within a shrouding segment 11 is placed a sheet metal 17 provided with a plurality of cooling orifices 16 so that it is opposite to the moving- blade side peripheral wall 18 at a prescribed distance. On the moving-blade side peripheral wall 18 is provided a cooling passage 24 which connects the inside of the shrouding segment 11 and the upper stream side from a moving blade 14. Hereby, the moving-blade side peripheral wall can be efficiently cooled with only a small quantity of air, and accordingly, the efficiency of a turbine can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a shroud segment, and more particularly to an air-cooled shroud segment suitable for high temperature gas turbines.

[Technical front of the invention and its problems] In general, the shroud segment of a turbine is arranged circumferentially on the inner surface of the turbine casing so as to be close to the outer peripheral end of the rotor blade. The shroud ring is installed to minimize leakage of mainstream gas from the tips of the rotor blades, prevent heat transfer from high temperature gas to the turbine casing, and prevent thermal deformation of the casing. For this reason, the shroud segments are directly exposed to high-temperature gas, so the higher the turbine inlet temperature, the more careful attention must be paid to cooling the shroud segments.

Conventional shroud segments are broadly classified into two types: those that do not cool the segment at all, and those that cool the segment from the inside by introducing cooling air into the shroud segment. However,
In the former case, there was a problem in that the metal temperature of the shroud segment rose to near the mainstream gas temperature, making it impossible to raise the gas temperature and thus making it impossible to obtain high output.

In the latter case, as shown in FIG. 6, openings 2a and 2b are provided in the upstream wall 1a and the downstream wall 1b of the shroud segment 1, respectively, to allow cooling air to flow into the internal space 3 of the segment. There is a form of interrogation. However, in this type, the cooling air A is simply flowed into the internal space 3, so the flow rate of the cooling air A is slow, and the heat transfer rate from the inner wall surface of the segment to the cooling air is low, increasing the temperature of the mainstream gas. In this case, there was a problem in that a large amount of cooling air was required to maintain the metal temperature of the shroud segment 1 at a predetermined temperature. Also, in other formats,
As shown in FIG. 7, the box-shaped shroud segment 4
A box-shaped insert 6 is inserted radially into the pigment through the outer opening 5 of the insert 6, and cooling air A guided from the turbine casing 7 into the shroud segment 4 is inserted into the pigment.
There is a method in which impingement cooling is performed by blowing air onto the inner wall surface of the segment through the opening 8 of the shroud segment 4, and the cooled air is discharged to the outside of the resegment through the opening 9 of the downstream side wall 4b of the shroud segment 4 (Japanese Patent Application Laid-Open No. 1983-1999). (See Publication No. 59030). According to this type, the metal temperature of the shroud segment 4 can be maintained at a predetermined temperature with a small amount of suspended cooling air, but it is necessary to provide a wide opening 5 in the shroud segment 4 in order to insert the insert 6. , a hook 10 that secures the shroud segment 4 to the inner surface of the turbine casing 7 by sandwiching it from the upstream and downstream sides.
There was a problem in that the spacing between the claws became large and the turbine casing 7 became large in the axial direction. In addition, since the insert 6 needs to be formed into a box shape, there is a problem that the shroud segment 4 becomes complicated.Furthermore, if the insert 6 is divided into two in order to make the opening 5 smaller, the structure of the insert 6 itself becomes complicated. There was a problem.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the problems of the prior art described above, and to provide an air-cooled shroud segment that has high cooling efficiency, has a simple structure, and is compact so that it can be used even when the mainstream gas temperature is high. This is what we provide.

[Summary of the invention]

In order to achieve the above object, the present invention provides a hollow shroud segment that is circumferentially connected to the inner surface of a turbine casing so as to be close to the outer peripheral end of the rotor blade, and in which a plurality of hollow shroud segments are provided in the inner space of the shroud segment. A thin plate having cooling holes is provided in the circumferential direction so as to face the rotor blade side circumferential wall of the shroud segment with a predetermined gap, and the rotor blade side circumferential wall communicates the internal space with the upstream side of the vJ blade. A cooling path is formed to efficiently cool the shroud segment.

[Embodiments of the invention]

Embodiments of the shroud segment according to the present invention will be described below with reference to FIGS. 1 to 5. FIG.

In FIG. 1, reference numeral 11 indicates a shroud segment, and this shroud segment 11 is formed with a substantially C-shaped cross section, and is fitted into a circumferential hook 13 with a substantially T-shaped cross section that protrudes from the inner surface of the casing integrally with the turbine casing 12. Combined. By arranging a plurality of shroud segments 11 in a circumferential manner, a shroud ring (not shown) is formed on the inner surface of the turbine casing 12 and is close to the outer peripheral end of the rotor blade 14 . Further, an internal space 15 having a rectangular cross section is formed in the shroud segment 11 that is fitted into the hook 13, and this internal space 15 has a plurality of cooling holes 1.
6 is provided so as to face a peripheral wall 18 of the shroud segment 11 facing the rotor blade 14 (hereinafter referred to as the rotor blade side peripheral wall) with a predetermined gap therebetween. The thin plate 17 is an inner wall surface 11a of the shroud segment 11.
It is inserted in the circumferential direction from the segment end face into a pair of grooves 19 formed in the circumferential direction, and is fixed to the shroud segment 11 by fillet welding 20. Further, as shown in FIG. 2, a substantially C-shaped groove 22 having the same cross-sectional shape as the segment is formed on the end surface 21 of the shroud segment 11, and a sealing material (not shown) is fitted into this groove 22. This prevents leakage of mainstream gas at the joints between the segments. Further, in the rotor blade side circumferential wall 18 of the shroud segment 11, a cooling passage 2 is provided which communicates the internal space 15 with the mainstream gas flow passage 23 on the upstream side of the rotor blade 14.
A plurality of cooling passages 4 are bored, and the cooling passages 24 are bored diagonally in accordance with the rotating direction X of the rotor blades 14, as shown in FIG.

On the other hand, a cooling passage 25 for supplying cooling air is formed in the hook 13 into which the shroud segment 11 is fitted, from the turbine casing 12 side toward the internal space 15, and the cooling air A discharged from the compressor is It is supplied into the shroud segment 11 from the cooling passage 25 through a passage (not shown) in the turbine casing.

Next, the present invention will be explained in detail.

Cooling air A is supplied to the internal space 15 of the shroud segment 11 from the cooling passage 25 of the hook 13, cools the inner wall surface 11a of the segment, and is further blown from the cooling hole 16 of the thin plate 17 toward the rotor blade side circumferential wall 18 to cool the rotor blade side peripheral wall 18. The inner surface 18a of the blade side circumferential wall is cooled by impingement 1. Further, the cooling air that impinges on the rotor blade side circumferential wall 18 is discharged from the cooling passage 24 of the rotor blade side circumferential wall to the mainstream gas flow path 23 on the upstream side of the rotor blade 14 . This cooling air is
is emitted with a circumferential velocity component in the same direction as the rotor blade 14.
It flows through the gap between the rotor blade side circumferential wall 18 and the rotor blade side circumferential wall outer surface 18.
B is film-cooled and then mixed into the mainstream gas B.

In this way, the inner surface 18a of the FJI brass peripheral wall of the shroud segment, where the metal temperature rises when it comes into contact with the high-temperature mainstream gas B, is subjected to impingement cooling, which has a high heat transfer coefficient and high cooling efficiency, and is also a direct heat-receiving surface. Since film cooling is applied to the outer surface 18b of the rotor blade side circumferential wall, only the #J blade side circumferential wall 18, which is the heat receiving part, can be efficiently cooled.
8, it is possible to reduce leakage of mainstream gas from the tips of the rotor blades. In addition, since only the portions that require cooling are cooled, sufficient cooling can be achieved with a small amount of cooling air, and by reducing the amount of cooling air introduced from the compressor, a decrease in turbine efficiency can be reduced.

Further, since the thin plate 17 blocks radiant heat from the heat receiving portion of the shroud segment 11 to the turbine casing 12, it is possible to suppress the temperature rise due to the radiant heat of the turbine casing.

Therefore, if the above-mentioned shroud segment 11 is used, it becomes possible to further raise the temperature of the mainstream gas, and it is possible to improve the turbine efficiency.

4 and 5 show another embodiment of the present invention, in which a reinforcing glue 126 is fixed to the segment inner wall surface 11a at the circumferential center of the shroud segment 11 and the inner surface 18a of the rotor blade side peripheral wall. There is. Further, the thin plate 17 having cooling holes provided in the internal space 15 of the shroud segment 11 is divided into two pieces, and the thin plates 17a and 17b are assembled into the shroud segment 11 from both end faces in the circumferential direction.

Therefore, according to this embodiment, even if the shroud segment 11 is formed to have a substantially C-shaped cross section so as to form the internal space 15, there will be no strength problem in the segment body because the rib 26 is provided. , it is possible to obtain the same effects as in the above-mentioned embodiments.

〔Effect of the invention〕

As is clear from the above description, the present invention provides a thin plate having a plurality of cooling holes in the inner space of a shroud segment in the circumferential direction so as to face the circumferential wall on the rotor blade side of the segment with a predetermined gap, and Since a cooling path is provided in the peripheral wall to communicate the internal space of the segment with the upstream side of the rotor blade, only the rotor blade side peripheral wall, which is the heat receiving part of the shroud segment, can be efficiently cooled with a small amount of cooling air. In addition, since the amount of cooling air extracted from the compressor is reduced, it is possible to reduce the decrease in turbine efficiency, and furthermore, the film cooling air flowing on the outer surface of the rotor blade side circumferential wall is connected to the shroud ring and l! Since the leakage of mainstream gas between the I3 blade tip and the I3 blade tip is reduced, turbine efficiency can be improved. Further, since the thin plate blocks radiant heat from the shroud segment heat receiving portion to the turbine casing, the upper limit of the temperature of the turbine casing can be suppressed and thermal deformation of the casing can be prevented. Therefore, it is possible to improve the turbine efficiency by further lowering the mainstream gas temperature, and it is possible to obtain an air-cooled shroud segment with a compact structure in the cylinder while achieving high cooling 1J1 efficiency.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing one embodiment of the shroud segment according to the present invention, FIG. 2 is a perspective view of the shroud segment, FIG. 3 is a front sectional view of the shroud segment, and FIG. 4 is a shroud according to the present invention. FIG. 5 is a perspective view of the shroud segment, and FIGS. 6 and 7 are side sectional views showing conventional shroud segments. DESCRIPTION OF SYMBOLS 11... Shroud segment, 12... Turbine casing, 13... Hook, 14... Moving blade, 15
...Internal space, 16...Cooling hole, 17...Thin plate,
18... vJ wing side circumferential wall of shroud segment, 20
... Fillet welding, 23... Mainstream gas flow path, 24...
・Cold path, Δ...Cold 1J1 efficiency, B...Mainstream gas. Applicant's agent Mr. Sato Figure 3 Figure 4 Figure 5 Figure 7

Claims (1)

[Claims] 1. In a hollow shroud segment that is circumferentially arranged on the inner surface of the turbine casing so as to be close to the outer peripheral end of the rotor blade, a plurality of cooling holes are provided in the inner space of the shroud segment. A thin plate having a thin plate is provided in the circumferential direction so as to face the rotor blade side circumferential wall of the shroud segment with a predetermined gap, and a cooling path is formed in the rotor blade side circumferential wall to communicate the internal space with the upstream side of the rotor blade. A shroud segment characterized by: 2. The shroud segment according to claim 1, wherein the cooling passage is formed toward the rotating direction of the rotor blade.