JPS5832902A - Steam turbine - Google Patents

Abstract

PURPOSE:To withstand the increased temperature and increased pressure of main steam requirements by forming a high pressure outside casing in a barrel-type structure divided in two in the axial direction and with no horizontal flange in the high pressure section of a high powered steam turbine. CONSTITUTION:Double discharge type nozzle boxes 4c, 4d are arranged at both ends of a high pressure stage group. High pressure outside casing 2a, 2b have no flange and are formed in a barrel-type structure divided in two in the axial direction. The steam passing a nozzle 4b and blade 5b flows between the outside casings 2b, 2a and an inside casing 3, and mixing with the steam flown out of the first high pressure blade 5a, then flows into the second high pressure nozzle. Therefore, the high pressure inside casing 3 is invariably kept at a higher pressure at its outside, thus its strength design is made very easy. Accordingly, the steam turbine can withstand an increase of main steam requirements, and the operability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention solves structural problems of steam turbine casings, particularly high-pressure section casings, which occur as the main steam conditions of steam turbine plants increase in temperature and pressure to improve thermal efficiency. The present invention relates to a steam turbine configured to.

In recent years, as a measure to improve the thermal efficiency of thermal power plants, the main steam pressure and temperature have been changed to 246atg, 83
Measures are being taken in many areas to raise the temperature by 82 degrees above 8 degrees Celsius. The main problem in making turbines higher in temperature and pressure is the structure of the high-pressure casing.

Figures 1 and 3s show the vital air pressure 24 @ mtg, the main steam temperature s 38°C, and the output cuff 00. It is a structural diagram of a high pressure part used in a turbine of #W or higher.

In FIG. 1, steam travels through the high-pressure outer casing 2 and the high-pressure inner casing 3 installed inside it to the double-flow nozzle box 4 through four main steam inlet pipes 1. , the steam of
The result of expanding in the diversion nozzle 4 a m 4 b and flowing into the high pressure inner casing 3's center head; the tip 1 of the provided a-tube 10; the attached high pressure first stage vanes 5 m and 5 b, and doing work. Apply rotational force to the rotor 10. The steam flowing out from the high-pressure first stage vane IIs directly flows in the axial direction and flows into the -8 stage nozzle 6i, which is supported from the inside and outside by the nozzle diaphragm inner ring 6C. On the other hand, the steam flowing out from the high-pressure first-stage vane sb turns around inside the high-pressure internal casing 3 and also flows into the second-stage nozzle 6a.

The steam expanded within the second stage nozzle 6m flows into the third stage vane 7, passes through the high pressure stage group in the same manner, and then passes through the high pressure exhaust stage vane 8.
After flowing out, it is exhausted by two high-pressure exhaust pipes (not shown) provided at the base of the high-pressure outer casing 2 and returns to the boiler reheater (not shown).

The reason why the high-pressure first stage is a double flow is that if it were a single flow, the blade height would increase and the centrifugal stress in the rotating part of the high-pressure first stage would be severe. In a high-temperature, high-pressure supercritical pressure turbine, the casing has a double structure as shown in Fig. 3 to relieve stress in the inner and outer casings (31(2).However, the temperature is still high.

Special for high pressure: It is difficult to design the horizontal flange of cable Ving.In order to withstand high temperature and high pressure and eliminate leakage from the horizontal joint surface, the horizontal flange is made larger and the diameter of the flange joint is increased. It is twisted in pairs. However, as the horizontal flange 2 becomes larger, the non-uniformity of the wall thickness of the casing increases, resulting in non-uniform temperature distribution in the axial and local directions, resulting in thermal stress, especially during startup, shutdown, and load. The thermal stress at the time of change may be too high or too low. It is clear from the above explanation that as the main steam conditions become higher in temperature and pressure, it becomes even more difficult to design a single high-pressure casing.

The object of the present invention is to provide a steam turbine having a high-pressure casing having an advantageous structure in terms of strength, which solves the problems of the prior art as described above, and which can withstand increases in main steam conditions Φ. Width = Yes.

Embodiments of the present invention will be described below with reference to FIGS. 2 and 4. The steam flowing into the nozzle box 4C expands in the nozzle 4 and flows into the high pressure first stage impeller. ' does work and gives rotational force to the a-taper 1G.

The steam flowing out from the high-pressure first stage vane 5 m continues to flow in the axial direction through the high-pressure 2R nozzle 6% high-pressure second-stage vane 1 or less while working through the high-pressure general stage steamer and flows out from the high-pressure first stage vane 8. High-pressure exhaust pipes (not shown) attached to the outer casing and extending outside through the high-pressure outer casing (2 pipes for preparation, or axially spaced (;' If there is no room, measure 2 pipes vertically and 2 pipes apart) 4) and returns to the boiler reheating equipment.

On the other hand, the high-pressure outer casing 2 is connected via four main steam pipes 1b.
The steam that has flowed into the nozzle box 4d via the nozzle 4b passes through the nozzle 4b and the outer casing 2b*
2 m and the high pressure first stage vane S passing between the inner casing 3
The flow is further reversed, mixed with the steam flowing out from the high-pressure initial vane Sm, and flows into the high-pressure two-stage nozzle, whereupon it flows as described above and is exhausted from the high-pressure exhaust pipe.

That is, the fact that the double-flow type nozzle boxes 4c*4d of FIG. 1 are brought to both ends of the high-pressure stage group is the key. In addition, the high-pressure external casing, 2 m long, has a horizontal flange at @b (cylindrical shape with upper and lower halves integrated, with vertical joint flange 11a for assembly and maintenance.

2ms in the direction perpendicular to the axis at flb! It is designed so that it can be divided into two parts. During assembly, the vertical joint flange part 11
a, High pressure internal cage in llb.

After inserting the positioning key 1B of the ring 3, bolt 12,
Tighten with 13 and seal with gasket 14 to completely eliminate the external atmosphere. 4th @ is a view taken along the line A-A in FIG. 2.

Next, the present invention constructed as above will be explained in detail. The reason why the high-pressure first stage was installed at both ends was to allow the steam flowing out from one high-pressure first stage to flow between the high-pressure outer casing 21゜zb and the high-pressure inner casing 3, and to make the atmosphere in this gap similar to that of the high-pressure first stage shell. This is what I encountered. By doing this, the external pressure of the high-pressure internal casing 3 is always higher, so its strength design becomes very easy, and there is no need to worry about increasing the size of the horizontal flank or increasing the diameter of the flange joint bolt.

On the other hand, the high-pressure external casing has a high-pressure exhaust atmosphere inside in the conventional type shown in Fig. 1, but in the present invention, it has a first-stage renyl atmosphere 1; therefore, the horizontal ridge structure has been abandoned and a so-called pot-shaped structure has been adopted. I can do it. However, for assembly and maintenance, it is divided into two parts in the wheel direction, and the ground part 16,
17 is also removable. Although the inner brown atmosphere is higher temperature and pressure than the conventional type, by making it a tail shape, there is no need for a large horizontal flank, and only the required wall thickness needs to be ensured, making it almost completely axially symmetrical. It is very advantageous in terms of thermal stress because it has a good structure and there is no temperature gradient in the axial direction.

As explained above, according to the present invention, the high-pressure outer casing has an axially two-part pot-shaped structure with a horizontal flange, and the inner casing has an external pressure structure, so the casing can be made more compact without impairing maintainability. , it becomes possible to form an axially symmetrical structure, and it is possible to provide a bush air turbine with good operability that can withstand high temperature and high pressure main carbon dioxide conditions.

[Brief explanation of drawings]

FIG. 4 is a sectional view showing a conventional supercritical pressure high output steam turbine, FIG. 2 is a sectional view showing a supercritical pressure high output steam turbine according to the present invention, and FIG.
...High pressure outer casing 3 ...High pressure inner casing 4.4C*4d...Nozzle pock's □4a
*4b...High-pressure first-stage nozzle 5a*5b...High-pressure first-stage blade 6...High-pressure second-stage nozzle 7...High-pressure second-stage blade 8...High-pressure first-stage blade L 16.17--Gland packing 10・
...A-ta 11 heat, 11b...Vertical joint flange 12...Bolt 13...Nara-to 14...Gasket packing 1s.
...Positioning key (7317) Agent: Patent attorney Noriyuki Kon (and 1 others)
given name)

Claims (1)

[Claims] In the high-pressure section of a high-power steam turbine that uses high-pressure first stage as a steam source, a double-flow type nozzle box is used in the high-pressure first stage, and two high-pressure first stages are arranged at both ends of the high-pressure stage group, and the high-pressure outer casing is placed in the axial center. A steam turbine characterized in that it is divided into two in the direction perpendicular to the axis and has a flange joint structure.