JPS58133402A - Rotor cooling mechanism of axial flow turbine - Google Patents

Abstract

PURPOSE:To improve a cooling effect, by differently forming a dimensional shape of balance holes in a pair of the first stage discs placed at a face-to-face position to each other in a double flow axial turbine. CONSTITUTION:Balance holes 5a, 5b are provided to the first stage discs 4a, 4b, and labyrinth packings 7a, 7b mounted to the first stage nozzle inner wheel 6 are located at a face-to-face position in the radially outside of said holes. Size of the holes 5a, 5b is formed different to decrease pressure in a space 8 lower than pressure in a space 14a. In this way, a flow in one-way is generated in the space 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a rotor cooling mechanism for an axial flow turbine, and more particularly to a rotor cooling mechanism for a double flow type multi-stage axial flow turbine.

[Technical background of the invention and its problems]

In axial flow turbines that use high-temperature steam or gas as a working medium, the inlet section is exposed to high temperatures due to the high-temperature fluid flowing into the turbine, and the rotor, which is a rotating component, is particularly stressed, so it is necessary to cool the rotor. often occurs.

FIG. 1 illustrates a rotor cooling mechanism of a conventionally used double-flow multi-stage steam turbine, and shows the first and second stages immediately after fluid flows into the turbine.

In this example, by setting the degree of reaction at the root of the first stage N2 of the rotor 1 to be negative, the pressure at the root of the rotor blade outlet is made higher than that at the root of the rotor blade inlet. A part of the fluid flowing in from the nozzle 3 and exiting the first stage rotor blade 2 is guided to the front side of the first stage disc 4 through the balance hole 5 provided in the first stage disc 4, and then transferred to the first stage nozzle inner ring 6. The fluid flows out to the outlet of the first stage nozzle 6 through a gap between the labyrinth packing 7 provided on the side and the first stage disc 4, and the first stage disc 4 is cooled by this flow of fluid.

This mechanism has a simple structure and is often used, but since the recoil at the base of the first stage is negative, there is a risk of deteriorating the stage performance. Since there is almost no flow of steam, the temperature of the fluid increases due to friction caused by the rotation of the rotor, resulting in insufficient cooling of the rotor near the intermediate portion 8.

In another conventional example shown in FIG.
The outlet spaces 11 of the stage nozzles 10 are communicated with each other, and a part of the fluid at the outlet of the first stage rotor blade 2 is guided to the front side of the disc through the balance hole 5 of the first stage disc 4. After that, it is cooled through the hole 9.

In such a mechanism, two rows of holes pass through portions of different diameters of one disk, which poses a problem in terms of structural strength.

[Purpose of the invention]

The object of the present invention is to eliminate the above-mentioned difficulties in conventional rotor cooling mechanisms and to provide an axial flow turbine with a simple structure (i.e., a large cooling effect).

[Summary of the invention]

In order to achieve the above object, the present invention includes a pair of first-stage disks facing each other (both of which are provided with a balance hole,
In a double flow type axial flow turbine C2, in which a pair of labyrinth packings are provided in the inner ring of the first stage nozzle so as to face positions outside the balance holes of the pair of first stage disks, one of the first stage The size and shape of the balance hole of the disk are different from the balance hole of the other first stage disk, so that the fluid flowing into the space formed by the first stage nozzle inner ring and the rotor through the balance hole of the other balance hole is different from the balance hole of the other first stage disk. The main feature is that it is configured to flow out of the space through a hole.

[Embodiments of the invention]

The present invention will be described in detail below with reference to FIGS. 6 and 4.

In the embodiment shown in FIG. 13, the first stage disk 4 a t4
B has a balance hole 5m and 5b,
Radially outward from the position of these balance holes,
Labyrinth packings 7m and 7b attached to the inner ring 6 side of the first stage nozzle face each other.

8 indicates a space created by the first stage nozzle inner ring 6 and the rotor 1.

Further, the first stage disk 4b on one side (the right side in the figure) faces the labyrinth packing 10 attached to the second stage nozzle inner ring 12b (two on the downstream side).

In this embodiment with such a configuration, the right first stage disk 4
The pressure in the space 14b on the right side of the balance hole 1v5b is approximately equal to the outlet pressure of the second stage nozzle 10b, and by appropriately combining the balance holes 5m and 5b with different sizes, The pressure in the space 8 formed by the nozzle inner ring 6 and the rotor 1 is transferred to the outlet section 14 of the first stage rotor blade 2m.
The pressure can be adjusted to be slightly lower than the pressure of 11.

The steam -8 exiting the first stage jiii2m on the left side of ζ2 flows into the space 8 through the balance hole 51, and is further guided into the space 14b through the balance hole 5b, and then flows into the second stage nozzle inner ring. 12b and the second stage N15b, and cools the disk 4m, rotor 1, and disk 4b during this time.

In this case, since a unidirectional flow occurs in the space 8, the fluid does not stagnate, and the temperature of the fluid does not rise due to wind damage.

The balance hole provided in the matatisk may be of the same size as that of the subordinate pot, and the structural strength will not be reduced.

Furthermore, since there is no need for the first stage to have a negative recoil degree at the base, there is no deterioration in the performance of the stage.

In the embodiment shown in FIG. 4, compared to the mechanism shown in FIG. 3, a balance hole 16b is provided in the right second stage disc 15b, and the second stage disc 15b has a portion radially outward from the balance hole position on the upstream side. , the labyrinth packing 17 attached to the second stage nozzle inner ring 12b side
The other configurations in FIG. 4 as opposed to b are the same as in FIG. 3.

In this embodiment with such a configuration, the balance hole 16b
If the size of the space 14b is sufficient, the pressure in the space 14b will be approximately equal to the outlet pressure of the second stage rotor blade 17b, and the balance hole 5
By appropriately combining the sizes of a and sb, the pressure in the space 8 can be made slightly lower than the pressure in the outlet space 141 of the first stage rotor blade 2a.

As a result, a part of the fluid exiting the left first stage rotor blade 2a passes through the balance hole 5a and flows into the space 8, and then flows through the balance hole 5b and the space 14b.

Passing through the balance hole 16b, the right second stage rotor blade 17b
During this time, the disc was 4m away.

The rotor 1 and disk 4b are cooled.

In this case, since the cooling fluid passes through the balance hole 16b and flows out into the passage at the stage exit, the main flow is different from the structure in which the cooling fluid flows out into the passage between the second stage nozzle 10b and the vane 17b as in the embodiment shown in FIG. This is advantageous in that there is less possibility of disturbing the

〔Effect of the invention〕

As described above, according to the present invention, by simply making the size of the balance hole slightly different between the left and right first-stage disks,
The rotor can be cooled without reducing the structural strength of the rotor or the stage performance, and an axial flow turbine with high performance and excellent durability can be obtained.

[Brief explanation of the drawing]

FIGS. 1 and 2 are sectional views showing a conventional rotor cooling mechanism, and FIG. 3 and 4 are sectional views showing an embodiment of the rotor cooling mechanism according to the present invention, respectively. 1 ・・・・・・・・・・・・・・・・・・・・・
Rotor 2, 2at 2b--first stage moving blade 3, 3a
t3b...first stage nozzle 4, 4m, 4b...first stage disk 5,
5at 5b...1st stage balance hole 6...
・・・・・・・・・・・・・・・ 1st stage nozzle inner ring 7, 7ae 7b... 1st stage nozzle labyrinth seal 8゛ ・・・・・・・・・・・・・-・・・・・・Space 9 formed by the first stage nozzle inner ring and rotor ・・・・・・・・・・・・・・・・・・ Hole 1
0 = 10a r 1 ob +++ 2nd stage nozzle 1
1 ・・・・・・・・・・・・・・・・・・・・・・・Exit space 12b of second stage nozzle ・・・・・・・・・・・・・・・・・・・・・
Second stage nozzle inner ring 13b ・・・・・・・・・・・・
......2nd stage nozzle labyrinth gasket 14m, 14b...1st stage rotor blade 3
Mouth space 15b ・・・・・・・・・・・・・・・
...Second stage disk 16b ......
・・・・・・・・・・・・Second stage balance hole 17b
・・・・・・・・・・・・・・・・・・・・・Second
Stage nozzle labyrinth packing Fig. 1 d Fig. 2 Fig. 3 Fig. 4 1M b Excitation

Claims (1)

[Scope of Claims] 1. A balance hole is provided in each of the pair of first-stage discs facing each other, and a balance hole is provided in the inner ring of the first-stage nozzle so as to face the outer position of the balance hole of the pair of first-stage discs. In a double flow axial flow turbine provided with a pair of labyrinth backings, the balance hole of one of the first stage disks is different from the balance hole of the other first stage disk, and the first stage is A rotor cooling mechanism for an axial flow turbine, characterized in that fluid flowing into a space formed by a nozzle inner ring and a rotor flows out of the space through the other balance hole. 2. A second valve that allows the fluid that has flowed into the first stage rotor blade mouth space through the balance hole of one of the first stage discs to flow out.
The rotor cooling mechanism for an axial flow turbine according to claim 1, wherein the stage balance hole is provided in the second stage disk.