Rotary kinetic fluid motors or pumps – Working fluid passage or distributing means associated with... – Plural distributing means immediately upstream of runner
Reexamination Certificate
2000-04-03
2001-12-25
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Working fluid passage or distributing means associated with...
Plural distributing means immediately upstream of runner
C415S199500
Reexamination Certificate
active
06332754
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a steam turbine in which at least two turbine sections, in combination, selected from a high pressure turbine section, an intermediate pressure turbine section and a low pressure turbine section is accommodated in a single turbine casing.
There has been attempted to realize a steam turbine having a main steam pressure of 100 kg/cm
2
or more, a main steam temperature of 500° C. or more, and a rated output (power) of 100 MW or more, which are rotated at a rotation speed of 3,000 rpm in the case of being equipped with a last-stage movable blade of turbine having an effective blade length of 36 inches or more, or which are rotated at a rotation speed of 3,600 rpm in the case of being equipped with a last-stage movable blade of turbine having an effective blade length of 33.5 inches or more. In such steam turbine, a set of a high pressure turbine section, an intermediate pressure turbine section and a low pressure turbine section or a set of a high pressure turbine section and a low pressure turbine section is provided on a single turbine rotor (turbine shaft) supported by two journal bearings placed on a pedestal, each of these turbine sections being integrally accommodated in a single turbine casing. However, such steam turbine has not yet been bought into practice at present and remain on the drawing board because of their technical difficulty, particularly, difficulty of preventing shaft vibrations caused by insufficient stiffness of the shafting in association with the increased bearing span.
A steam turbine satisfying the above-mentioned design requirements may have a configuration as shown in
FIG. 17
, for example.
In this steam turbine, a turbine casing
1
has a double casing structure consisting of an outer casing
1
a
and an inner casing
1
b,
and in the inner casing
1
b
of the double casing structure, for example, a high/intermediate pressure integrated turbine rotor
4
having a high pressure turbine section
2
and an intermediate pressure turbine section
3
is accommodated. On the other hand, a low pressure turbine casing
5
also has a double casing structure consisting of an outer casing
5
a
and an inner casing
5
b,
and a low pressure turbine rotor
7
having low pressure turbine sections
6
a,
6
b,
in which steams flow in directions opposing to each other, is accommodated in the inner casing
5
b
of the double casing structure. The low pressure turbine rotor
7
and the high/intermediate pressure integrated turbine rotor
4
are connected with each other through a coupling
8
.
In another steam turbine, for example, as shown in
FIG. 18
, a high/intermediate pressure integrated turbine rotor
4
is accommodated in the inner casing
5
b
of the double casing structure such as describe above, while a low pressure turbine rotor
7
having a low pressure turbine section
6
, in which a steam flows as a single flow, is accommodated in an inner casing
5
b
of a low pressure turbine casing
5
.
The low pressure turbine casings
5
shown in
FIGS. 17 and 18
both are formed with a conical recess portion
11
at the position where the low pressure turbine rotor
7
is inserted in a turbine exhaust hood
10
(chamber or section) defined by a partition wall
9
to ensure an installation area for a journal bearing
12
, and the turbine exhaust hood
10
is connected to a condenser (not shown) on its downstream side.
Furthermore, in the steam turbines shown in
FIGS. 17 and 18
, the high/intermediate pressure integrated turbine rotor
4
and the low pressure turbine rotor
7
are supported by three or four journal bearings
12
.
On the other hand, even in the case of a steam turbine which employs, for example, the high/intermediate pressure integrated type turbine which does not satisfy the above-mentioned design requirements, for example, as shown in
FIG. 19
, a high/intermediate/low pressure integrated turbine rotor
4
a
having a high pressure turbine section
2
, an intermediate pressure turbine section
3
and a low pressure turbine section
6
is supported by journal bearings
12
placed on pedestals
13
a,
13
b.
The turbine exhaust hood
10
defined by a partition wall
9
is formed with a conical recess portion
11
and connected to a condenser, not shown, on its downstream side. In this case, since a bearing span S of the journal bearings
12
supporting the high/intermediate/low pressure integrated turbine rotor
4
a
is relatively short, it is possible to satisfactorily handle the problem of vibrations that occur during the operation.
Generally, in a steam turbine, as the output power increased because of increase in the pressure and temperature of the steam to be supplied, the number of turbine stages consisting of combination of turbine nozzles and turbine movable blades is increased to thereby respond to the increased power, so that the bearing span S of the turbine rotor is inclined to become long. For this reason, in the case of the high/intermediate/low pressure integrated turbine
4
a
having e.g., the high pressure turbine section
2
, the intermediate pressure turbine section
3
and the low pressure turbine section
6
on a single shaft, the bearing span S becomes long. Accordingly, providing that a shaft diameter of the high/intermediate/low pressure integrated turbine
4
a
is defined as D
O
, as the ratio of the shaft diameter with respect to the bearing span S (S/D
O
) becomes higher, the stiffness of the shaft becomes lower, and according to the lowering of the eigenvalue (characteristic value) frequency of the shaft, the critical speed becomes lower, thus, making it difficult to satisfactorily operate the steam turbine.
Particularly, for bringing such a steam turbine into practice that has a main steam pressure of 100 kg/cm
2
or more, a main steam temperature of 500° C. or more, and a rated output of 100 MW or more, rotated at a rotation speed of 3,000 rpm in the case of being equipped with a last-stage movable blade of turbine having an effective blade length of 36 inches or more or rotated at a rotation speed of 3,600 rpm in the case of being equipped with a last-stage movable blade of turbine having an effective blade length of 33.5 inches or more, and that employs a single turbine rotor supported by two journal bearings placed on pedestals, if the conventional technique is directly applied, the bearing span S becomes long to lower the critical speed, and in particular, as the secondary critical speed approaches the rated rotation speed, vibrations of the shaft is increased, which can hinder the operation.
SUMMARY OF THE INVENTION
The present invention was conceived in view of the the problems or defects encountered in the prior art mentioned above and an object of the invention is to provide a steam turbine capable of producing larger amount of work per one turbine stage, as well as allowing stable operation by shortening the bearing span.
This and other objects can be achieved according to the present invention by providing, in one aspect, a steam turbine which comprises, in combination, at least two of a high pressure turbine section, an intermediate pressure turbine section and a low pressure turbine section in a single turbine casing and which satisfies design requirements of: a main steam pressure of 100 kg/cm
2
or more; a main steam temperature of 500° C. or more; a rated output of 100 MW or more; and a unit rotated at a rotation speed of 3,000 rpm equipped with a last-stage movable blade of the turbine having an effective blade length of 36 inches or more, or a unit rotated at a rotation speed of 3,600 rpm equipped with a last-stage movable blade of the turbine having an effective blade length of 33.5 inches or more,
where in a turbine exhaust chamber of the low pressure turbine section has a structure extending towards both sides of a transverse direction of the turbine casing.
In another aspect, there is provided a steam turbine which comprises, in combination, at least two of a high pressure turbine section, an intermediate pressure turbine section and a l
Kikuchi Masataka
Kitaguchi Kouichi
Matsuda Minoru
Okita Nobuo
Kabushiki Kaisha Toshiba
Look Edward K.
McAleenan James M
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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