Leak reducing structure in a steam turbine

Details Leak reducing structure in a steam turbine Leak reducing structure in a steam turbine

1999-10-28

2001-05-29

Look, Edward K. (Department: 3745)

Rotary kinetic fluid motors or pumps

Including means for handling working fluid leakage

Leakage through seal between runner or shaft and static part

C415S058700, C415S059100

Reexamination Certificate

active

06238180

ABSTRACT:

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
1. Field of the Invention
The present invention relates to a leak reducing structure in a steam turbine. More particular, it relates to a leak reducing structure in a steam turbine, which prevents a trouble such that in a steam turbine of a single casing type, high-pressure steam passes through a seal portion of a dummy ring and leaks to the intermediate pressure turbine side, by which the performance is decreased.
2. Description of Related Art
FIG. 3
is a sectional view showing the interior of a conventional steam turbine of a single casing type. In
FIG. 3
, reference numeral
1
denotes a rotor,
2
denotes an external casing covering the whole of the turbine,
3
denotes a high pressure turbine section in which stator blades on the stationary side and rotor blades fixed to the rotor
1
are arranged in a multi-stage form,
4
denotes an intermediate pressure turbine section in which stator blades and rotor blades are arranged in a multi-stage form in the same way, and
5
denotes a similar low pressure turbine section. These high pressure, intermediate pressure, and low pressure turbine sections
3
,
4
and
5
are arranged around the rotor
1
in the axial direction thereof in the single external casing
2
.
A high-pressure steam inlet port
6
supplies high-pressure steam to the high pressure turbine section
3
, and a high-pressure steam outlet port
7
causes the steam that has done work in the high pressure turbine section
3
to flow out to the outside. Also, an intermediate-pressure steam inlet port
8
supplies intermediate-pressure steam to the intermediate pressure turbine section
4
, and a low-pressure steam inlet port
9
supplies low-pressure steam to the low pressure turbine section
5
. A nozzle chamber
13
for high-pressure steam is integrally incorporated in a dummy ring
10
. The dummy ring
10
is disposed between the high pressure turbine section
3
and the intermediate pressure turbine section
4
to provide a seal. The steam that has done work in the intermediate pressure turbine section
4
and the low pressure turbine section
5
is discharged to an exhaust chamber
11
.
In the steam turbine of the above configuration, high-pressure steam
30
flows into the high pressure turbine section
3
through the high-pressure steam inlet port
6
, does work in the high pressure turbine section
3
, and flows out through the high-pressure steam outlet port
7
. Also, intermediate-pressure steam
32
flows into the intermediate pressure turbine section
4
through the intermediate-pressure steam inlet port
8
, and does work in the intermediate pressure turbine section
4
. Thereafter, the steam further flows into the low pressure turbine section
5
. Low-pressure steam
33
flows into the low pressure turbine section
5
through the low-pressure steam inlet port
9
. In the low pressure turbine section
5
, the steam flowing from the intermediate pressure turbine
4
and the steam flowing through the low-pressure steam inlet port
9
are combined to do work, and are discharged to the exhaust chamber
11
.
In the turbine of the above configuration, the rotor
1
is rotated in the high pressure turbine section
3
, the intermediate pressure turbine section
4
, and the low pressure turbine section
5
as described above, by which a generator (not shown) connected to the rotor
1
is rotated. Between the high pressure turbine section
3
and the intermediate pressure turbine section
4
, there is disposed the dummy ring
10
to provide a seal. Therefore, some of the high-pressure steam passes through a seal portion of the dummy ring
10
, and causes a leak to the side of the intermediate pressure turbine section
4
as a leak
34
, resulting in a decrease in performance.
As described above, in the steam turbine comprising the high pressure, intermediate pressure, and low pressure turbine sections in the single casing, the dummy ring
10
for providing a seal is provided between the high pressure turbine section
3
and the intermediate pressure turbine section
4
, and some of high-pressure steam from the high pressure turbine section
3
passes through the seal portion of the dummy ring
10
, causing a leak to the side of the intermediate pressure turbine section
4
. Therefore, if the leak amount is large, the performance is affected adversely, so that there is a fear of decreasing the performance of the high pressure turbine section
3
.
OBJECT AND SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a leak reducing structure in a steam turbine in which measures are taken to prevent a leak of high-pressure steam from a dummy ring for providing a seal between a high pressure turbine section and an intermediate pressure turbine section of the steam turbine to the intermediate pressure side, and the leaking steam is recovered to do work on the upstream side, by which the decrease in performance of the steam turbine can be prevented.
To solve the problem with the above-described prior art, the present invention provides the following means.
In a leak reducing structure in a steam turbine, in which high pressure, intermediate pressure, and low pressure turbine sections are arranged in the axial direction of a rotor in a single casing, and a dummy ring is disposed around the rotor between the high pressure turbine section and the intermediate pressure turbine section to provide a seal, a seal portion between the dummy ring and the rotor surface is caused to communicate with an intermediate point of a steam passage of the high pressure turbine section by a pipe, and steam passing through the seal portion of the dummy ring from the high pressure turbine section and leaking to the side of the intermediate pressure turbine section is recovered to the side of the high pressure turbine section.
In the above-described leak reducing structure in a steam turbine, in the high pressure turbine section, high-pressure steam is introduced, passes through the steam passage, drives the rotor to do work, and flows out through a port on the exhaust side. Some of the high-pressure steam passes through a gap between the dummy ring on the rotor side and the seal portion and attempts to leak to the intermediate pressure turbine side. A pipe is connected to an intermediate portion of the seal portion of dummy seal, and the pipe is connected to a point at an intermediate portion of the steam passage of the high pressure turbine section, where the pressure is lower than that on the dummy ring side, so that the leaking steam is recovered to the steam passage of the high pressure turbine section. The recovered steam combines with the steam of the high pressure turbine section, does work, and then flows out through an exhaust port of the high pressure turbine section. Therefore, the decrease in performance of the high pressure turbine section can be prevented.
The leak reducing structure in a steam turbine in accordance with the present invention is configured such that in a leak reducing structure in a steam turbine, in which high pressure, intermediate pressure, and low pressure turbine sections are arranged in the axial direction of a rotor in a single casing, and a dummy ring is disposed around the rotor between the high pressure turbine section and the intermediate pressure turbine section to provide a seal, a seal portion between the dummy ring and the rotor surface is caused to communicate with an intermediate point of a steam passage of the high pressure turbine section by a pipe, and steam passing through the seal portion of the dummy ring from the high pressure turbine section and leaking to the side of the intermediate pressure turbine section is recovered to the side of the high pressure turbine section. By this configuration, most of the steam that passes through the seal portion of the dummy ring from the high pressure turbine section and attempts to leak to the intermediate pressure turbine section is recovered, and combines with the steam flowing into the high pressure turbine section

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