JP3029930B2 - Steam turbine casing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casing for a steam turbine, and more particularly to a cooling structure for a horizontal flange of a high-to-medium pressure casing.

[0002]

2. Description of the Related Art FIG. 11 is a cross-sectional view showing an example of a horizontal flange portion of a conventional steam turbine high-medium pressure casing cut along a plane perpendicular to a rotation axis. The casing is divided into two by a horizontal plane into a casing upper half (1A) and a casing lower half (1B), and the horizontal flanges (2A) and (2
B). A number of studs (3) are set in the lower horizontal flange (2B), and the upper half of the casing (1) is set.
A) is tightened by a nut (4) and is formed integrally with the lower casing half (1B). In order to facilitate the tightening of the bolts and to control the tightening force, bolt heating is usually performed by heating the bolts and utilizing the thermal expansion thereof.

The above horizontal flange bolts (3), especially the bolts for tightening the inner casing and the horizontal flange, are heated by the influence of high-temperature steam during operation, and when the bolts are tightened for a long period of time, the bolts and flanges are not tightened. Is loosened by high-temperature creep, which causes a problem that steam leaks from the horizontal flange surface. For this reason, relatively low-temperature steam is caused to flow through the bolt holes (5) to cool the bolt holes (5), thereby securing bolt tightening force after long-time use at high temperatures.

[0004]

The conventional steam turbine casing has the following problems to be solved. 1) When the temperature of the casing is low at start-up, the steam supplied to the bolt holes causes the temperature of the bolt to rise before the casing, the bolt tightening force decreases, and the cooling steam leaks from the horizontal flange surface. was there. 2) Stress corrosion cracking (Stress C)
orrosion Crack: Stress corrosion that accelerates corrosion under stress occurs, which causes cracks. ) May occur or cooling steam may leak from the threaded portion.

[0005]

The present invention proposes the following steam turbine casing to solve the above-mentioned conventional problems. 1) It halves and the casing lower half portion on the casing
Independent, respectively in cross-section along a plane substantially parallel to Ke pacing inner surface inside the horizontal flange bolts of the horizontal flange
A steam turbine casing, wherein a long cooling steam flow path is formed. 2) The steam turbine casing according to the above 1), wherein a pipe for supplying cooling steam to the flow passage from an arbitrary cascade outlet in the steam turbine is provided. (3) The steam turbine casing according to (1) or (2), wherein an obstacle is provided such that a flow velocity distribution of the cooling steam is uniform in the flow path.

[0006]

Since the present invention has the above-described configuration, the following effects can be obtained. 1) The heat flux transmitted from the high-temperature steam to the horizontal flange and the bolt is blocked by cooling steam flowing through the steam flow path inside the bolt. Therefore, the horizontal flange and the bolt are not heated to a high temperature, and the bolt and the flange are not distorted by creep and the bolt tightening force is not reduced. 2) No stress corrosion cracking occurs in the horizontal flange bolts even after a long operation, and no cooling steam leaks from the threaded portions.

[0007] 3) When the steam turbine is started, the bolts are in a bolt warming state in which the bolts warm up before the flanges, so that the bolt tightening force is reduced and the steam does not leak from the horizontal flange surface. 4) When the steam turbine is started, the cooling steam flow path blocks an excessive heat flux flowing from the inside of the flange, so that the temperature of the casing does not rise prior to the bolt. Therefore, the bolt tightening force becomes excessive, and the bolt tightening force decreases due to the yield of the bolt or flange,
There is no leakage of steam from the horizontal flange surface.

5) Since the temperature difference in the rotation axis direction is reduced, the bolt stress does not become excessive on the low temperature side.

[0009]

FIG. 1 is a cross-sectional view showing a horizontal flange portion of a first embodiment in which the present invention is applied to a high- and medium-pressure casing, cut along a plane perpendicular to a rotation axis. In this figure, the same parts as those of the prior art described with reference to FIG. 11 are denoted by the same reference numerals to avoid redundancy, and detailed description is omitted.

In the present embodiment, the horizontal flanges (2A) of the upper half (1A) and the lower half (1B) of the casing are provided.
(A), (2B) By forming a groove in the inner surface of each and welding the lids (6A), (6B) to the inner surface, a surface substantially parallel to the inner surface of the casing (inside the stud bolt (3)). The cross section along the (almost vertical plane) is long and independent from each other
Cooling steam passages (17A), to form a (17B). Then, a relatively low-temperature steam is caused to flow through the cooling steam flow paths (17A) and (17B) for cooling. No cooling steam is supplied to the bolt holes (5). The pair of cooling steam passages (17
A) and (17B) are to prevent the generation of thermal stress.
It is provided in a vertically symmetric and left-right symmetric position.

[0011] Cooling steam is supplied by piping from any cascade outlet in the steam turbine. Therefore, the temperature of the cooling steam can be freely selected depending on from which stage the air is extracted. Further, the temperature of the cooling steam can be controlled by extracting air from a plurality of paragraphs at the same time, so that effective cooling can be performed when the turbine is started and stopped.

FIG. 2 is a cross-sectional view showing a horizontal flange portion according to a second embodiment of the present invention cut along a plane perpendicular to the rotation axis (II-II cross section in FIG. 3), and FIG. 4 is a plan view showing the lower half with the upper half removed, FIG. 4 is a side view of the same seen from the inside of the casing (right side of FIG. 2), and FIG. 5 is a perspective view of the same. Also in these figures, the same parts as those described above are denoted by the same reference numerals, and detailed description is omitted.

[0013] Also in this embodiment, the horizontal flange of the casing upper half (1A) and the casing lower half (1B) (2A), on the inner side of the (2B) each of the horizontal flange bolts, substantially parallel to the inner surface of the casing Along independent surfaces, the flow paths of cooling steam (flat cooling chambers) independent of each other (2)
7A) and (27B) are formed.
A relatively low-temperature steam flows from the cooling steam inlet (7) to (27B). (8) is a cooling steam outlet. In the present embodiment, a flat cooling chamber (a cooling steam flow path having a vertically long cross section) (2 )
7A), so that a uniform flow velocity distribution in (27B), Cold
An anti- friction plate (9) is provided in the steam passages (27A) and (27B) .

FIG. 6 is a cross-sectional view (sectional view taken along the line VI-VI of FIG. 7) of the third embodiment of the present invention, showing a horizontal flange section cut along a plane perpendicular to the rotation axis. VII-VII is a horizontal sectional view, and FIG. 8 is a perspective view of a high-temperature pipe that is inserted. Also in these figures, the same parts as those described above are denoted by the same reference numerals, and detailed description is omitted.

In this embodiment, the casing (1
A), inside the bolt holes (5) of the horizontal flange portions (2A) and (2B) of (1B) and along a plane substantially parallel to the inner surface of the casing, a high-temperature pipe (see FIG. 8). 1
0) is cast-in at the time of manufacturing the casing to form cooling steam passages (37A) and (37B). In this case, in the vicinity of the cross section having the steam inlet hole (11) shown in FIG.
A large number of bends as shown in a) are provided to increase the density of the cooling steam flow paths (37A) and (37B).

The cooling steam passages (37A), (3
7B), low-temperature steam is introduced from the downstream side, and is spontaneously discharged to the low-pressure chamber (13) isolated by the dummy ring (12). When controlling the flow rate of the cooling steam in accordance with the operation state, as shown in FIG. 9, the cooling steam flow path (37B) is once taken out of the casing (1B) and controlled by the control valve (14). Can also.

FIG. 10 is a diagram showing an example of an analysis result performed to quantitatively confirm the effect of the present invention. FIG.
10A is a radial temperature distribution in the case of a conventional horizontal flange portion shape, and FIG. 10B is a radial temperature distribution in a case where a thermal shield and a cooling steam flow path are provided.

[0018]

According to the present invention, the horizontal flange and the bolt can be effectively cooled without the steam leaking from the horizontal flange surface or the flange bolt thread portion and without causing the stress corrosion cracking of the bolt. The reliability of the high and medium pressure steam turbine inner casing and outer casing is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a horizontal flange portion of a first embodiment of the present invention, cut along a plane perpendicular to a rotation axis.

FIG. 2 is a cross-sectional view showing a horizontal flange portion according to a second embodiment of the present invention cut along a plane perpendicular to the rotation axis (FIG. 3);
II-II section).

FIG. 3 is a plan view showing the lower half of FIG. 2 by removing the upper half;

FIG. 4 is a side view as viewed from the right side of FIG. 2;

FIG. 5 is a perspective view of the second embodiment.

FIG. 6 is a cross-sectional view showing a horizontal flange portion according to a third embodiment of the present invention cut along a plane perpendicular to the rotation axis (FIG. 7);
VI-VI section).

FIG. 7 is a VII-VII horizontal sectional view of FIG. 6;

FIG. 8 is a perspective view of a high-temperature pipe which is inserted in the third embodiment.

FIG. 9 is a view showing a modification of the third embodiment.

FIG. 10 is a diagram showing an example of an analysis result performed to quantitatively confirm the effect of the present invention.

FIG. 11 is a cross-sectional view showing an example of a horizontal flange portion of a conventional steam turbine high- and medium-pressure casing cut along a plane perpendicular to a rotation axis.

[Explanation of symbols]

 (1A) Upper casing half (1B) Lower casing half (2A), (2B) Horizontal flange (3) Stud bolt (4) Nut (5) Bolt hole (6A), (6B) Lid (7) Cooling steam Inlet (8) Cooling steam outlet (9) Flame plate (10) High temperature piping (11) Steam inlet hole (12) Dummy ring (13) Low pressure chamber (14) Control valve (17A), (17B) Cooling steam flow Road (27A), (27B) Cooling steam flow path (cooling chamber) (37A), (37B) Cooling steam flow path

Continuation of the front page (72) Inventor Toru Kobayashi 2-1-1, Shinhama, Arai-machi, Takasago-shi, Hyogo Mitsubishi Heavy Industries, Ltd. Takasago Research Laboratory (56) References JP-A-62-265408 (JP, A) 167801 (JP, U) JP-A-59-7204 (JP, U) JP-A-57-58322 (JP, Y2) US Patent 3,390,830 (US, A) (58) Fields investigated (Int. Cl. ⁷ , (DB name) F01D 25/12 F01D 25/24 F01D 25/26

Claims (3)

(57) [Claims] 1. A along a plane substantially parallel to Ke pacing inner surface inside the horizontal flange bolts independent horizontal flange portion in each of the halves and the casing lower half portion on the casing
A steam turbine casing, wherein a cooling steam flow path having a long vertical section is formed. 2. A steam turbine casing according to claim 1, further comprising a pipe for supplying cooling steam from an arbitrary cascade outlet in the steam turbine to the flow path. 3. The steam turbine casing according to claim 1, wherein an obstacle is provided such that a flow velocity distribution of the cooling steam is uniform in the flow path.