JPH0441906A - Steam turbine - Google Patents

Abstract

PURPOSE:To make an inner casing compact by supporting the inner casing on an outer casing via support legs extended from flange sections of a lower- half casing in a steam turbine constituted of double casings of the inner casing and the outer casing. CONSTITUTION:In a steam turbine with a double-casing structure constituted of an inner casing 2 and an outer casing 10 surrounding a turbine rotor l to mitigate the thermal deformation and thermal stress when the fed steam has a high pressure and a high temperature, key-shaped support legs 25 extended on the right and left sides of a turbine rotor l from flange sections of the lower- half casing 4 of the inner casing 2 are mounted on flange faces of the lower-half casing 12 of the outer casing 10 to be overlapped with an upper-half casing 11 and fastened with bolts 26 via liners 23. The diameter of flange bolts 5 fastening the upper-half casing 3 and the lower-half casing 4 of the inner casing 2 can be reduced, and the inner casing 2 can be made compact.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a steam turbine having a double casing consisting of an inner casing and an outer casing, and particularly to a support structure for the inner casing.

[Conventional technology]

Steam turbines are known in which a casing surrounding a turbine rotor has a double casing structure consisting of an inner casing and an outer casing in order to alleviate thermal deformation and thermal stress when the supplied steam is at high pressure and high temperature. FIG. 4 shows this type of steam turbine, and FIG. 5 is a detailed enlarged view of section A in FIG. 4. In FIGS. 4 and 5, an inner casing 2 is provided that surrounds a turbine rotor 1 that is equipped with rotor blades (not shown) and that includes stationary blades (not shown) that form a blade stage with the rotor blades. The internal casing 2 has a two-part structure, and the upper half casing 3 and the lower half casing 4 are overlapped at the axial center level of the turbine rotor 1, and the flange portions of the upper half and lower half casings 3.4 are connected with flange bolts. 5 has been concluded. A steam supply hole 6 for supplying steam to the blade stages is provided in the upper part of the upper half casing 3.

The outer casing 10 is constructed by splitting an upper half casing 11 and a lower half casing 12, which are overlapped at the axial center level of the turbine rotor 1 and tightened by a fastening means (not shown).

The inner casing 2 has support legs 9 extending from the flange of the upper half casing 3 to the left and right sides with respect to the turbine rotor 1, and a liner 13 on the flange surface of the lower half casing 12 of the outer casing 10 with the upper half casing 11. It is supported by being tightened by a bolt 14 via the bolt 14.

In the upper part of the upper half casing 11 of the outer casing 10, there is a steam inflow chamber 1 into which steam flows through a main steam stop valve 15.
6 is installed internally. A plurality of steam control valves 17 are provided penetrating the earthen wall of the steam inflow chamber 16. Note that in order to introduce the steam in the steam inflow chamber 16 to the steam supply hole 6 of the upper half gauging 3 of the internal casing 2 by opening the steam control valve 17, an air introduction hole 19 is provided which penetrates the lower wall of the steam inflow chamber 16. is provided.

The elastic airtight ring 22 has a cross-sectional shape, and the steam introduction hole 19
It surrounds the steam outlet of the steam supply hole 6 and the steam inlet of the steam supply hole 6, and is inserted between the outer casing lO and the upper half casing 3 of the inner casing 2.

With this structure, the steam that flows into the steam inflow chamber 16 after opening the king steam stop valve 15 passes through the steam control valve 17 whose valve opening is adjusted according to the load of the turbine, and then flows into the steam introduction hole 19. The steam flows through the elastic airtight ring 22 and is led to the steam supply hole 6 of the inner casing 2.

Note that when the turbine load reaches full load, all the steam control valves 17 are fully opened, and the steam pressure inside the internal casing 2 is at its maximum.

The steam that has passed through the steam supply hole 6 in this manner flows into the blade stage, performs work in the blade stage, rotates the turbine rotor 1, and generates power. Note that the steam discharged from the blade stages is discharged to the outside from an exhaust port of the outer casing 11 (not shown).

By the way, since the steam that performs work in the blade stage flows inside the internal casing 2, the flange bolt 5 is fixed so that the mating surfaces of the flanges of the upper half casing 3 and the lower half casing 4 of the inner casing 2 are fixed at full load. Strength is maintained to maintain airtightness against steam pressure.

(Problems to be Solved by the Invention) As described above, the conventional inner casing 2 is connected to the outer casing l via the support I!j9 of the upper half casing 3.
O, the strength of the flange bolt 5 that fastens the upper half casing 3 and the lower half casing 4 of the internal casing 2 at the flange is limited to the internal A problem arises in that thick flange bolts are required which have sufficient sealing force to counteract the forces due to steam pressure within the internal casing commensurate with the total area of the mating surfaces of the casing 2.

An object of the present invention is to provide a steam turbine in which the inner casing can be made more compact by reducing the size of the flange bolts that fasten the upper half and lower half of the inner casing at the flange portions.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, a turbine rotor including moving blades, surrounding this rotor, and! An upper half casing and a lower half casing each having a stator vane forming a vane stage are fastened at a flange portion with a tightening member, and the upper half casing has a steam supply hole for supplying steam to the vane stage. A casing, an outer casing that surrounds the casing, includes a steam inlet chamber into which steam from the outside flows, and has a steam introduction hole that guides the steam in the steam inlet chamber to the blade stage via a steam control valve; In a steam turbine including an airtight ring inserted between the inner casing and the inner casing so as to surround the steam outlet of the steam introduction hole and the steam inlet of the steam supply hole, the inner casing is connected to a flange portion of the lower half casing. The support 7+1 (1) extending from the turbine rotor to the left and right sides of the turbine rotor is supported by a tightening portion H on the outer casing.

[Effect]

The inner casing, which surrounds the turbine rotor, is fastened to the upper half casing and the lower half casing by a tightening member at the flange section, and is tightened by support legs extending from the flange section of the lower half casing to the left and right sides of the turbine rotor. Since it is supported by a member, the strength given to the tightening member that fastens the flange parts to maintain airtightness from the mating surfaces of the flange parts of the upper half casing and the lower half casing is the total area of the mating surfaces of the inner casing. It is sufficient to counteract the steam pressure force applied within the inner casing corresponding to the area obtained by subtracting the area of the airtight ring through which the steam supplied to the blade stage flows. Therefore, the force due to steam pressure applied to the inner casing, which opposes the strength of the tightening member, is smaller than that of the conventional upper half casing supported on the outer casing, and therefore the flange bolt as the tightening member can be made smaller. .

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view of a steam turbine according to an embodiment of the present invention;
FIG. 2 is a detailed enlarged view of section B in FIG. 1. In addition, the first
FIG. 4 in FIG. 2.

Components that are the same as those in the conventional example shown in FIG. 5 are given the same reference numerals, and their explanations will be omitted. What is different from the conventional example in FIGS. 1 and 2 is that the key-shaped support legs 25 extending from the flange part of the lower half casing 4 of the inner casing 2 to the left and right sides of the turbine rotor 1 are attached to the upper half casing of the outer casing 10. 11
12fL is fastened to the flange surface of the lower half casing 12, which is overlapped with the liner 23, using bolts 26.

Note that the surface where the support leg 25 of the lower half casing 4 of the inner casing 2 is supported by the lower half casing 12 of the outer casing 10 is at the axial center level of the turbine rotor 1, that is, the mating surface of the inner casing 2 and the outer casing 10. are on the same level.

With this structure, the strength of the flange bolt 5 that fastens the upper half casing 3 and the lower half casing 4 of the inner casing 2 at the flange portion is determined by subtracting the area of all the elastic airtight rings 22 from the area of the mating surfaces of the inner casing 2. Since it is sufficient to counter the force corresponding to the steam pressure applied within the internal casing 2 at full load commensurate with the subtracted area, the diameter of the flange bolt 5 becomes small, and therefore the internal casing 2 can be made compact.

FIG. 3 is a cross-sectional view of an internal casing support of a steam turbine according to a different embodiment of the invention. When supporting the lower half casing shingle of the inner casing 2 in FIG.
The support leg 25a extending horizontally from the flange portion of the lower half casing 4 is positioned below the level of the mating surface of the lower half casing 12 and the upper half casing 11 of the outer casing 10 by the thickness of the support leg 25a. supported surface 1
2a is the same as in FIG. 1 except that it is supported by bolts 26 via a liner 23.

Even if the inner casing 2 is supported below the mating surface of the outer casing 10 by such a method, the same effect as described above can be obtained.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the inner casing, in which the upper half casing and the lower half casing are overlapped and fastened at the flange part with a tightening member, is connected to the turbine from the flange part of the lower half casing. A tightening member that fastens the upper half casing and the lower half casing of the inner casing to maintain airtightness at the flange by supporting the outer casing with the support legs extending on the left and right sides of the rotor. The strength applied within the inner casing is equal to the area of the mating surfaces of the inner casing minus the area through which steam flows in the airtight ring surrounding the outlet of the steam inlet hole in the outer casing and the inlet of the steam supply hole in the inner casing. All you have to do is counter the force caused by steam pressure, so
The tightening member that tightens the upper half casing and the lower half casing of the inner casing at the flange portion is small (and accordingly, the inner casing can be made compact).

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a steam turbine according to an embodiment of the present invention;
2 is a detailed partial sectional view of part B in FIG. 1, FIG. 3 is a partial sectional view of an internal casing support of a steam turbine according to a different embodiment of the present invention, and FIG. 4 is a sectional view of a conventional steam turbine. , FIG. 5 is a partially detailed sectional view of section A in FIG. 4. 1: Turbine rotor, 2: Internal casing, 3: Upper half casing, 4: Lower half casing, 5: Flange bolt, 6: Steam supply hole, 9.25: Support leg, 10: External casing, 16: Steam Inflow chamber, 17: Steam control valve,
19: Steam introduction hole, 22: Elasticity] Fig. 2 Fig. 3 Article 19, previous introduction Fig. 4

Claims (1)

[Claims] 1) A turbine rotor equipped with moving blades, an upper half casing and a lower half casing that surround this rotor and include stator vanes that form a blade stage with the moving blades, are fastened at the flange portion with a tightening member, and the upper half casing The inner casing is equipped with a steam supply hole that supplies steam to the blade stage, and a steam inflow chamber that surrounds this casing and into which steam from the outside flows in. An outer casing having a steam introduction hole leading to a paragraph, and an airtight ring inserted between the outer casing and the inner casing so as to surround the steam outlet of the steam introduction hole and the steam inlet of the steam supply hole. 1. A steam turbine characterized in that an inner casing is supported by a tightening member on an outer casing via support legs extending from a flange portion of a lower half casing to left and right sides of a turbine rotor.