JPS608404A - Low pressure casing of steam turbine - Google Patents

Abstract

PURPOSE:To enable the captioned casing to be made compact and light-weight by constructing a low pressure casing through uniting a casing in which exhaust chambers are formed on both end parts in the direction of the axis of a turbine and a concave part is formed in the central part, an external body which forms the bottom part of said concave part, and an internal body which has a static blade inside said external body. CONSTITUTION:The low pressure casing of a steam turbine is constructed by uniting the following three in a body; a casing 31 in which exhaust chambers 32 are formed on both end parts in the direction of the axis of a turbine and a concave part is formed on the central part, an external body 34 which forms the bottom part of said concave part, and an internal body 35 which has a static blade 27. A steam introducing part 15 is provided in the external body 34. And bleeding chambers 43 and 44 are formed between the external body 34 and the internal body 35.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a low-pressure casing for a steam turbine. [Technical Background of the Invention] A conventional low-pressure casing for a steam turbine is illustrated in FIGS.
This will be explained using figures.

In FIGS. 1 and 2, the double-flow type low-pressure casing consists of an outer casing 1 and an inner casing 2, which are constructed separately from each other. This outer casing l is divided into an upper half outer casing/A and a lower half outer casing/B, and similarly, the inner casing/ is divided into an upper half inner casing 2A and a lower half inner casing 2.
It is divided into upper and lower parts B. These upper and lower half outer casings /A and /B and upper and lower half inner casings 2A
and 2B are fixed to each other by tightening horizontal flanges 3 and V formed on each casing support part with multiple screws, as shown in FIG. The inner casing 2 is supported by an inner casing support 6 that projects inside the outer casing. Outer casing/
The relative fixation of the inner casing and the inner casing is carried out by means of a fixing key 7. This fixing key 7 is fitted into the outer and inner casings in the direction perpendicular to the turbine shaft g, and at the center of the inner casing, and fixes both at the center. In this way, the relative fixation of both casings is carried out at the center of both in the direction perpendicular to the turbine axis, so relative movement due to the difference in the amount of thermal expansion of each casing is carried out from the center of the casing. be exposed. As shown in FIG. 7, the turbine shaft r
A center keyer is provided between the outer casing / and the inner casing λ in the axial direction, and the outer casing l receives the counter torque of the inner casing λ. As shown in FIG. 2, a fixing key // that can be fitted and fixed is provided on the frame io at the center of the outside of the outer casing l in the direction perpendicular to the turbine axis direction. Thereby, the displacement of the outer casing/with respect to the gantry IO due to thermal expansion in the above-mentioned right angle direction is performed with the above-mentioned central portion as a base point.

Similarly, a fixed key is also provided between the outside of the outer casing l in the turbine axial direction and the pedestal 10, and receives the counter torque of the outer casing. Further, this low-pressure casing is supported on the pedestal 10 by a casing support portion 13 provided at the outer edge of the lower half outer casing l.

Referring again to FIG. 1, a steam introduction section /S is disposed in the center of the outer casing / via a Perot / 4, and one end of this steam introduction section 13 is connected to a cross-auto pipe / via a flange / 6. The other end is connected to the inner casing 2, and the high temperature and high pressure steam from the cross-over pipe /7 is introduced into the inner casing λ.The outer casing 1 also has exhaust chambers at both ends in the turbine axial direction. This exhaust chamber 7g is connected to a condenser (not shown).This outer casing is made of thin steel plate and is large in size. are provided with ribs 19 and a number of stays (not shown).An atmosphere discharge plate J is installed on the upper surface of the outer casing/in which the exhaust chamber /g is formed.This atmosphere discharge plate J is Exhaust chamber 1g
When the vacuum inside is broken, high pressure steam is released into the outer casing l.
discharge outside. The bearing 2/ of the turbine shaft r is supported by the outer casing/ via a reinforcing stay (not shown), and a bearing cover is provided on the outside of the bearing 2/. Further, a backing 3 is provided between the turbine shaft t and the outer casing.

In the center of the inner casing λ, there is a steam chamber 24t that introduces high-temperature, high-pressure steam from the steam introduction section/k to the inlet of the turbine section.
is formed. Also inside the inner casing
K has many turbine diaphragms j installed,
These turbine diaphragms J include stationary blade bodies that correspond to rotor blades 26 protruding from the turbine shaft r. The high-pressure steam introduced into the steam chamber 1 passes through the movable blade 2A and the stator vane 1 and rotates the turbine shaft r, and then enters the exhaust chamber 1 in a nearly vacuum state, from where it recovers. It reaches the water container and becomes condensate.

Furthermore, the C casing λ is provided with a plurality of bleed chambers 9 formed by partition portions 1g on the circumference.
The extracted steam from the bleed chamber Utah is sent via the bleed pipe 30 to a low-pressure feed water heater (not shown).

[Problems with background technology]

As described above, the conventional low-pressure casing has a double casing structure in which the outer casing and the inner casing are constructed separately, and therefore has the essential drawback of being large and complicated. Furthermore, the outer casing itself had the drawbacks of a complicated structure and increased weight due to the large number of reinforcing ribs and stays provided inside, as well as impeding the flow of steam inside the casing. The inner casing itself has a relatively thick plate welded structure due to the need to accurately hold the stationary blades relative to the turbine shaft, and has a structure with an extremely large horizontal flange area, which has the disadvantage of increased weight. Ta.

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of the above-mentioned points, an object of the present invention is to provide a low-pressure casing for a steam turbine that has a simple structure and can be downsized.

[Structure of the invention]

In order to achieve the above object, the present invention provides a casing in which exhaust chambers are formed at both end portions in the axial direction of a turbine, and a recessed portion is formed near the center, and a steam introduction portion that is located in the four portions and introduces high-temperature and high-pressure steam. an outer fuselage integrally constructed with the casing so as to form the bottoms of the four parts; and an inner fuselage integrally constructed inside the outer fuselage and having stator vanes on the inner peripheral side; A steam chamber is formed in the outer body and is connected to the steam introduction section and guides steam from there to the turbine section, and an air bleed chamber is formed between the outer body and the inner body. It is something to do.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a low pressure casing structure according to the present invention will be described below with reference to FIGS.

The same members as those shown in FIG. 1 are given the same reference numerals.

In FIGS. 3 and 5, the low pressure casing 3/ has exhaust chambers 32 formed at both ends in the turbine axial direction, and a four part 33 formed in the central part in the turbine axial direction.

The bottom of the recess 33 is formed by an outer body 3 which is integrally formed with the casing 3, and inside the outer body 31 there is provided an inner body 3 that is integrally formed therewith. Hiko, inside the exhaust chamber 32 of the casing 31, a reinforcing stay (not shown) is provided. In this way, in the present invention, the stay is sufficient as a rigid reinforcement material for the casing 3/, and the ribs as shown in FIG. 7 are no longer necessary. The reason why ribs are no longer needed is that the casing 3/ has an integral structure with the external and internal fuselage 3 and 35, and a recess 33 is formed in the center, so compared to Fig. 1, This is because it has improved significantly. These integrally structured casings 3/, three external fuselages, and internal fuselage 3S have an upper half casing and a lower half casing 37, respectively.
A.

37B, upper half, T genital body 3 da A, J4'B, upper half,
Lower internal torso 3! ; A, , 33B.

As shown in FIG. 3, horizontal flanges 36, 37, and 3g are provided on the dividing surface of the casing 31, the dividing surface of the outer body 3'l, and the dividing surface of the inner body 3S. These horizontal flanges jA, 37, 3
g is tightened by bolt 39, split casing, ? /A...? /B split external fuselage 3'lA, 3'lB
And, 3gB is attached to the divided inner fuselage, 33, to each other.

There are 3 exhaust chambers filled with low-temperature steam, an external body that is relatively hot compared to the exhaust chambers, and an internal fuselage 3'l, 3! Because there is a large difference in the amount of thermal expansion between . This thermal stress may cause cracks or abnormal deformation in the welded portion. In order to prevent the occurrence of such thermal stress, slits xi-o are provided in the flange near the joint between the horizontal flange 36 of the casing 3 and the horizontal flange 37 of the external fuselage. In this way, there is a slip near the joint of the horizontal flange 36.3, which has relatively high rigidity.

By cutting , it is possible to sufficiently absorb the difference in the amount of thermal expansion and prevent the occurrence of the thermal stress.

A steam introduction part /S is provided in the recess 33, and one end of this steam introduction part /g is connected to the flange 1 as in FIG.
It is connected to a cross-auto pipe /7 through a pipe 6, and the other end is connected to a steam chamber /7 formed between an external fuselage 3g and an internal fuselage 3s. This steam room 11. / Is the upper half of the external torso? The size is different between the part +/A located at 4'A and the part lI/B located at lower half external fuselage 3daB, and gradually decreases from the upper part F/A to the lower part 4t/B. It is configured to be. By reducing the steam chamber 4 (/B) of the lower half external fuselage 3'lB in this way, two bleed chambers '13 and 41+ are formed in the lower half external fuselage 3'lB depending on the partition value. These 31 bleed chambers are connected to a low-pressure feed water heater (not shown) via bleed pipes lIs and +x, respectively.

A large number of turbine diaphragms are installed inside the internal fuselage 3s, and these diaphragms are provided with stationary blade cores corresponding to the rotor blades protruding from the turbine shaft l.

The bearing of the turbine shaft t is installed directly on the pedestal 10 of the low pressure casing 31 shown in FIG. The rest of the configuration is the same as that in FIG. 1.

Next, the effect will be explained.

High-temperature, high-pressure steam from the cross-over pipe flows into the turbine section through the steam introduction section S and the steam chamber G, rotates the turbine shaft R, and then enters the exhaust chamber into a vacuum state. 3
2, from where it reaches a low-temperature condenser and becomes condensate. A part of the steam passes through 31 bleed chambers and is led to the low-pressure feedwater heater through bleed pipes d, 4'A.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, there is provided a casing having an exhaust chamber formed at both end portions in the turbine axial direction and a recessed portion formed in the central portion, and an external body forming the bottom of the recessed portion. Since the internal fuselage, which is disposed inside the external fuselage and the stator vanes, are integrated, the structure is simpler and more compact than the conventional double casing structure. Further, the integral structure allows simple reinforcement of the exhaust chamber, and complication of the structure can be avoided.

Furthermore, by forming slits in the horizontal flange as in this embodiment, it is possible to absorb the difference in thermal expansion between the high-temperature external body and the comparatively low-temperature exhaust chamber, thereby preventing the generation of thermal stress.

[Brief explanation of drawings]

Figures 1 and 2 are longitudinal cross-sectional views showing conventional low-pressure casings, partial cross-sections, and Figure 3 are plan views showing the horizontal flange viewed from the 1-1 arrow in Figure 1, respectively. Figure 5 is a vertical cross-sectional view showing an embodiment of the low pressure casing structure according to the present invention, Figure 5 is a plan view showing the horizontal flange seen from the ■-■ arrow direction in Figure G, and Figure 5 is a diagram showing the lower half casing. FIG. ! ...Turbine shaft, /3...Steam introduction part, 27...
・Stator blade, 3/...Casing, 3...Exhaust chamber, 3
3... recess, 3g... external fuselage, 3S... internal fuselage, dao... slit, ri/... steam chamber, l, 71
Matter...Bleed room. Applicant's agent Kiyoshi Inomata

Claims (1)

[Claims] (1) A casing with exhaust chambers formed at both ends in the turbine axial direction and four parts near the center, a steam introduction part that introduces high-temperature and high-pressure steam into the four parts, and a bottom of the recessed part. an outer fuselage integrally constructed with the casing, and an inner fuselage integrally constructed with the casing inside the outer fuselage and having stator vanes on the inner circumferential side; A low-pressure casing for a steam turbine, characterized in that a steam chamber is formed that connects to an introduction section and guides steam from there to a turbine section, and a bleed chamber is formed between the external body and the internal body. G2) Both the casing and the external body are divided into two parts, vertically, and flanges for fixing the divided casing and the external body, respectively, are provided on the casing dividing surface and the external body dividing surface, Claim 1, characterized in that the flange near the connection point between the casing and the external body is formed with a slit for absorbing a difference in thermal expansion between the casing and the external body. The low pressure casing of the steam turbine described in .