Rotary kinetic fluid motors or pumps – Selectively adjustable vane or working fluid control means – Separate means upstream and downstream of blade set
Reexamination Certificate
2001-03-12
2002-09-03
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Selectively adjustable vane or working fluid control means
Separate means upstream and downstream of blade set
C415S151000, C415S159000
Reexamination Certificate
active
06443695
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a steam turbine in which two or more turbine-pressure sections including a high pressure turbine, an intermediate pressure turbine and a low pressure turbine are combined and accommodated into one turbine casing.
In a conventional steam turbine, in order to increase an output power thereof, a turbine casing is divided into a high pressure turbine casing, an intermediate pressure turbine casing and a low pressure turbine casing, and a turbine rotor (turbine shaft) provided with a turbine nozzle and a turbine movable blade are accommodated in each of the casings to constitute a high pressure turbine section, an intermediate pressure turbine section and a low pressure turbine section, and the turbine rotors of the respective turbine sections are directly connected in their shafts in so-called a power train connection for operation.
If the high, intermediate and low pressure turbines are arranged as the power train, although depending on its output power, the steam turbine has a long span of at least about 30 m or longer. Therefore, two or more of the high, intermediate and low pressure turbines are combined and accommodated in one casing to shorten the span, thereby realizing a so-called high-low (high-and-low) pressure integrated type turbine or a high-intermediate (high-and-intermediate) pressure integrated type turbine.
If the steam turbine is formed into any of the high-low pressure integrated type turbine and the high-intermediate pressure integrated type turbine, the turbine rotor must inevitably handle steam having different pressures and temperatures. However, in recent years, there is realized a high-low pressure integrated turbine rotor or a high-intermediate pressure integrated turbine rotor, in which a portion of the turbine rotor which is exposed to steam having high pressure and temperature is made stronger against high-temperature, and a portion of the turbine rotor which is exposed to steam having low pressure and temperature is provided with tensile strength and toughness against low temperature by changing thermal treatment conditions.
Further, in a recent thermal power plant, there has been widely used a combined cycle power plant in which a steam turbine and a heat recovery means are combined with a gas turbine instead of a conventional power plant.
As a steam turbine applied to this combined cycle power plant, one having output power of 100 MW or more is selected in view of output power of 100 MW of a current gas turbine, the steam pressure is set to 100 kg/cm
2
, the steam temperature is set to 500° C., the blade height of the turbine movable blade of the final stage of the lower pressure turbine is made to 36 inches or higher in a region of 50 Hz at the revolution number of 3,000 rpm and is made to 33.5 inches or higher in a region of 60 Hz at the revolution number of 3,600 rpm. In this case, since the steam turbine is made into a so-called single-shaft type turbine in which the shaft is directly coupled to the gas turbine, the high-low pressure integrated type or the high-intermediate pressure integrated type is employed to shorten the shaft span and to reduce the site or space required for installation.
As described above, in the combined cycle power plant, which has widely and mainly utilized instead of the conventional power plant, the number of shafts directly coupling the steam turbine to the gas turbine is made five or more to increase the total output power to 1,000 MW or greater, and the steam turbine is made into the high-low pressure integrated type or the high-intermediate pressure integrated type, and the area required for installing the five shafting, i.e. shaft-alignment, is further reduced so as to effectively utilize the site or space.
In a recent thermal power plant, even if the high-low pressure integrated type or the high-intermediate pressure integrated type is employed for a steam turbine applied to the combined cycle power plant so as to further reduce the area required for installation, there provide several problems such as followings in its structure.
Problem 1
For example, in the case of a steam turbine employing the high-low pressure integrated type, as shown in
FIG. 10
, turbine nozzles
2
and turbine movable blade
3
of the high-low pressure integrated type rotor
1
are combined to form a pressure stage
4
, and the stage
4
is arranged in a multistage manner along a flowing direction of steam, and the stage
4
is accommodated in a turbine casing
5
.
The turbine casing
5
is divided into a high pressure turbine casing section
6
made of cast steel and a low pressure turbine casing section
7
made of steel plate. When the low pressure turbine casing section
7
is connected to the high pressure turbine casing section
6
, a high pressure turbine casing flange
9
a
and a low pressure turbine casing flange
9
b
provided downstream of a low pressure steam inlet
8
are connected with each other by means of stud bolt
10
inserted from the side of the high pressure turbine casing section
6
.
The turbine casing
5
including both the high and low pressure turbine casing sections
6
and
7
is formed into a split type comprising upper half portion and a lower half portion.
In such turbine casing
5
, when the high pressure turbine casing flange
9
a
which is the lower half portion and the low pressure turbine casing flange
9
b
which is the lower half portion are connected to each other, since the stud bolt
10
is inserted from the side of the high pressure turbine casing section
6
, there is a problem that the low pressure steam inlet
8
constitutes an obstacle for the connecting operation, and this requires much labor for a worker.
Especially in a recent combined cycle power plant, it is required to increase both the output powers of the gas turbine and the steam turbine and to reduce the number of shaft connection or alignment to reduce the area required for installation. Accordingly, the diameter of the low pressure steam inlet
8
tends to be greater and thus, its connecting operation takes much labor for the worker, and a new or improved countermeasure has been required.
Problem 2
In the conventional steam turbine, as shown in
FIG. 12
, the turbine casing
5
has a double cylindrical structure comprising an outer (external) casing
11
and an inner (internal) casing
12
, and for example, a high-intermediate pressure integrated turbine rotor
15
comprising a turbine high pressure portion
13
and a turbine intermediate pressure portion
14
is accommodated in the internal casing
12
. Similarly, a low turbine casing
16
is formed into a double cylindrical structure comprising an outer casing
16
a
and an inner casing
16
b
, a low pressure turbine rotor
18
including turbine low pressure portions
17
a
and
17
b
having opposite directions of stream flow is accommodated in the inner casing
16
b
, and the low pressure turbine rotor
18
and the high-intermediate pressure integrated turbine rotor
15
are connected with each other through a coupling
19
.
In the case of another type steam turbine as shown in
FIG. 13
, for example, the high-intermediate pressure integrated turbine rotor
15
is accommodated in the inner casing
12
as in the above case, and the low pressure turbine rotor
18
including a turbine low pressure portion
20
having a single current of steam is accommodated in the inner casing
16
b
of the low pressure turbine casing
16
. In each of the low pressure turbines
16
shown in
FIGS. 12 and 13
, a turbine exhaust chamber
21
is formed in a cone-like recess
22
and is connected to a steam condenser (not shown).
In each of the steam turbines shown in
FIGS. 12 and 13
, the high-intermediate pressure integrated turbine
15
and the low pressure turbine rotor
18
are pivotally supported by three or four journal bearing
23
to elongate the spans of the turbine casings
5
and
16
, and a difference in temperature (expansion work load) per one turbine stage is relatively reduced to provide a margin in design.
However, in
Kikuchi Masataka
Takahashi Toru
Kabushiki Kaisha Toshiba
Look Edward K.
Nguyen Ninh
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