JP3603911B2 - Centrifugal compressor casing structure - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a two-stage centrifugal compressor for a gas turbine, and more particularly, to a casing structure of a centrifugal compressor.
[0002]
[Prior art]
As schematically shown in FIG. 4, the gas turbine includes an air compressor, a combustor, and a turbine, compresses air with the air compressor, and uses the compressed air to burn fuel in the combustor. A turbine is driven by the combustion gas, and a part of the driving force drives the compressor and also drives an external load (a generator, a propeller, etc.).
[0003]
In such a gas turbine air compressor, a two-stage centrifugal compressor schematically shown in FIG. 5 has been conventionally used. The two-stage centrifugal compressor 1 includes two impellers 5a and 5b axially mounted in series on a rotor 4 rotationally driven by a turbine, and a casing 6 surrounding the impeller. The impeller includes a disk-shaped main plate and a plurality of blades attached thereto. The casing 6 includes a shroud portion 6a surrounding the blade portion, and a diffuser portion 6b for flowing air compressed by the impeller in a radially outward direction. And a return portion 6c for returning this flow to a flow inward in the radial direction. In the case of a two-stage centrifugal compressor, the return portion 6c is provided between the first-stage impeller 5a and the second-stage impeller 5b, and the air compressed by the first-stage impeller 5a is provided inside the second-stage impeller 5b. Has the role of supply.
[0004]
[Problems to be solved by the invention]
In a two-stage air compressor for a gas turbine, the air compressed by the second-stage impeller 5b has a high temperature and a high pressure. As shown in FIG. 4, the casing is divided into a plurality of parts in order to incorporate each impeller into the casing. In particular, the inner ends of the first and second casings are simply connected by fitting. It is just being done. Therefore, when the second stage compressor is exposed to the above-described severe environment in both pressure and temperature, complicated deformation occurs due to the temperature distribution of the casing itself and the pressure difference between before and after, and the tip clearance of the second stage impeller becomes large. However, there is a problem that rubbing (rubbing) occurs partially and the compression performance is greatly reduced.
[0005]
For this reason, the tip clearance of the second-stage impeller has been reduced and the operating pressure and temperature have been set low by, for example, using a material having a small thermal expansion coefficient for the second-stage casing. There was a problem that the material and processing cost of the material were high, and the structural restrictions were large, and the performance of the compressor could not be improved.
[0006]
The present invention has been made to solve such a problem. That is, an object of the present invention is to reduce the deformation of the casing at a high operating pressure and operating temperature without using a special material, thereby constantly reducing the tip clearance of the impeller, thereby reducing cost. An object of the present invention is to provide a casing structure of a centrifugal compressor capable of improving performance.
[0007]
[Means for Solving the Problems]
According to the present invention consists of a first and a second impeller which rotates coaxially a plurality of blades attached thereto a disc-shaped main plate, a casing surrounding these impellers, the casing 1 consists of a stage casing and the second stage casing, the air compressed by the first impeller and the second supplying the impeller return portion, a shroud portion surrounding the blade portion of the second impeller, compressed by the second impeller a diffuser portion air to flow radially outward, in the casing structure of a centrifugal compressor for a gas turbine having both ends thereof extending in the axial direction is connected to the shroud portion and the return portion, the first-stage second stage casing and suppressing the inner support axial displacement relative to the casing, both ends extending in the axial direction is connected to the diffuser portion and the return portion, within the elastic range Comprising an outer support to absorb the radial displacement between the first stage casing and the second stage casing by Mukoto casing structure of the centrifugal compressor is provided, characterized in that.
[0008]
According to a preferred embodiment of the present invention, the inner support and the outer support are formed in a ring shape.
[0009]
[Action]
According to the configuration of the present invention described above, an inner support and an outer support extending in the axial direction are provided. At both ends of the inner support, the inner support is connected to the second-stage shroud portion and the first-stage return portion. Since the support is connected to the second-stage diffuser and the first-stage return, the inner inner support can suppress the axial displacement of the casing between the first and second stages, and the outer outer support Accordingly, by bending the support within the elastic range, the radial displacement between the first and second stages can be absorbed to prevent the generation of thermal stress, and at the same time, the clearance at the outer peripheral portion of the impeller can be kept uniform.
[0010]
That is, the outer outer support functions as a guide when the second casing moves in the radial direction, and the inner inner support displaces the second casing in the axial direction due to pressure and temperature with respect to the first casing. Suppress Therefore, the casing surrounding the second-stage impeller can maintain a stable displacement (not including a fall of the surface) and an appropriate clearance.
[0011]
【Example】
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the drawings, common parts are denoted by the same reference numerals.
FIG. 1 is a partial configuration diagram of a centrifugal compressor for a gas turbine having a casing structure according to the present invention. In this figure, the centrifugal compressor is a two-stage centrifugal compressor 10, which includes a first impeller 5a and a second impeller 5b, and a casing 12 surrounding these impellers. Each of the impellers 5a and 5b includes a disk-shaped main plate and a plurality of blades attached to the main plate, and rotates coaxially.
[0012]
Further, the casing 12 includes a return portion 13 that supplies the air compressed by the first impeller 5a to the second impeller 5b, a shroud portion (second shroud portion 14) surrounding the blade portion of the second impeller 5b, and a second portion. And a diffuser section (second diffuser section 15) for flowing air compressed by the impeller 5b outward in the radial direction. In this drawing, reference numerals 7 and 8 denote a first shroud portion and a first diffuser portion, respectively.
[0013]
Further, in FIG. 1, the casing structure of the centrifugal compressor for a gas turbine according to the present invention includes an inner support 16 and an outer support 17 extending in the axial direction, respectively. Both ends of the inner support 16 are connected to the second shroud portion 14 and the return portion 13, and both ends of the outer support 17 are connected to the second diffuser portion 15 and the return portion 13. In addition, in this figure, the inner support 16 is formed integrally with the return portion 13, but the present invention is not limited to this, and may be configured separately. Further, in this embodiment, the inner support 16 and the outer support 17 are formed in a ring shape to ensure sufficient rigidity and airtightness. The outer support 17 prevents the pressurized air 2 compressed by the second impeller 5b and supplied to the combustor (not shown) from flowing back into the gap between the return portion 13 and the second diffuser portion 15. it can.
[0014]
FIG. 2 shows an analysis result of thermal deformation of the two-stage centrifugal compressor shown in FIG. 1, and FIG. 3 shows a similar thermal deformation analysis result of a conventional casing structure. 2 and 3 are shown on the same scale. In FIGS. 2 and 3, broken lines indicate before deformation, and solid lines indicate after deformation. From FIG. 3, in the conventional casing structure (FIG. 3), the axial displacement of the second-stage second shroud portion 14 and the second diffuser portion 15 is large, and the tip clearance of the second-stage impeller becomes large. Rubbing (rubbing) may occur. On the other hand, in the casing structure (FIG. 2) of the present invention, the axial displacement of the second-stage second shroud portion 14 and the second diffuser portion 15 in the second stage is small, and the overall displacement is substantially uniform in the axial direction. This shows that the casing surrounding the second-stage impeller can be maintained at a stable displacement (not including the falling down of the surface) and an appropriate clearance can be maintained.
[0015]
It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the spirit of the present invention.
[0016]
【The invention's effect】
As described above, according to the configuration of the present invention, the axial displacement of the casing between the first and second stages can be suppressed by the inner inner support, and the support can be bent within the elastic range by the outer outer support. By doing so, the radial displacement between the first and second stages can be absorbed to prevent the generation of thermal stress, and at the same time, the clearance at the outer peripheral portion of the impeller can be kept uniform. That is, the outer outer support functions as a guide when the second casing moves in the radial direction, and the inner inner support displaces the second casing in the axial direction due to pressure and temperature with respect to the first casing. Suppress Therefore, the casing surrounding the second-stage impeller can maintain a stable displacement (not including a surface tilt) and an appropriate clearance.
[0017]
Therefore, the casing structure of the centrifugal compressor of the present invention can suppress the deformation of the casing at a high working pressure and a high working temperature without using a special material, thereby always reducing the tip clearance of the impeller. It has excellent effects such as reduction of cost and improvement of performance.
[Brief description of the drawings]
FIG. 1 is a partial configuration diagram of a centrifugal compressor having a casing structure according to the present invention.
FIG. 2 is an analysis result of thermal deformation of the two-stage centrifugal compressor shown in FIG.
FIG. 3 is a result of thermal deformation analysis in a conventional casing structure.
FIG. 4 is a schematic view of a gas turbine.
FIG. 5 is a conventional casing structure diagram of a two-stage centrifugal compressor.
[Explanation of symbols]
1 air compressor (two-stage centrifugal compressor)
2 Pressurized air 4 Rotor 5a First-stage impeller (first impeller)
5b Second stage impeller (second impeller)
6 Casing 6a Shroud part 6b Diffuser part 6c Return part 7 First shroud part 8 First diffuser part 10 Two-stage centrifugal compressor 12 Casing 13 Return part 14 Second shroud part 15 Second diffuser part 16 Inner support 17 Outer support

Claims (2)

It comprises first and second impellers, each comprising a disk-shaped main plate, a plurality of blades attached thereto, and rotating coaxially, and a casing surrounding these impellers. The casing comprises a first-stage casing and a second-stage casing. consists eyes casing, the air compressed by the first impeller and the second return supplies the impeller, the shroud portion and, radially outwardly compressed air in the second impeller surrounding the blade portion of the second impeller In the casing structure of a gas turbine centrifugal compressor having a diffuser portion flowing through,
An inner support that extends in the axial direction and has both ends connected to the shroud portion and the return portion, and that suppresses axial displacement of the second-stage casing with respect to the first-stage casing ;
An outer support extending in the axial direction, both ends of which are connected to the diffuser portion and the return portion, and which bends within an elastic range to absorb radial displacement between the first-stage casing and the second-stage casing ; A casing structure for a centrifugal compressor, characterized in that: The casing structure of a centrifugal compressor according to claim 1, wherein the inner support and the outer support are formed in a ring shape.

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