U.S. patent application number 14/236396 was filed with the patent office on 2014-07-17 for steam turbine comprising a thrust balance piston.
This patent application is currently assigned to SIEMENS AKTIENGESELLSCHAFT. The applicant listed for this patent is Martina Holder, Christian Lenz, Norbert Pieper, Rudolf Potter, Dominic Schlehuber, Uwe Zander. Invention is credited to Martina Holder, Christian Lenz, Norbert Pieper, Rudolf Potter, Dominic Schlehuber, Uwe Zander.
Application Number | 20140199161 14/236396 |
Document ID | / |
Family ID | 45002221 |
Filed Date | 2014-07-17 |
United States Patent
Application |
20140199161 |
Kind Code |
A1 |
Holder; Martina ; et
al. |
July 17, 2014 |
STEAM TURBINE COMPRISING A THRUST BALANCE PISTON
Abstract
A cooling mechanism for a steam turbine is provided, which has,
in the area of the valve connection a cooling channel, into which
cooling steam flows from the flow channel, the steam then being fed
as cooling steam in the area of the thrust balance piston.
Inventors: |
Holder; Martina; (Essen,
DE) ; Lenz; Christian; (Herzogenaurach, DE) ;
Pieper; Norbert; (Duisburg, DE) ; Potter; Rudolf;
(Essen, DE) ; Schlehuber; Dominic; (Oberhausen,
DE) ; Zander; Uwe; (Mulheim an der Ruhr, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Holder; Martina
Lenz; Christian
Pieper; Norbert
Potter; Rudolf
Schlehuber; Dominic
Zander; Uwe |
Essen
Herzogenaurach
Duisburg
Essen
Oberhausen
Mulheim an der Ruhr |
|
DE
DE
DE
DE
DE
DE |
|
|
Assignee: |
SIEMENS AKTIENGESELLSCHAFT
Munich
DE
|
Family ID: |
45002221 |
Appl. No.: |
14/236396 |
Filed: |
August 1, 2012 |
PCT Filed: |
August 1, 2012 |
PCT NO: |
PCT/EP2012/065065 |
371 Date: |
January 31, 2014 |
Current U.S.
Class: |
415/104 |
Current CPC
Class: |
F01D 3/04 20130101; F05D
2260/20 20130101; F01K 3/04 20130101; F05D 2220/31 20130101 |
Class at
Publication: |
415/104 |
International
Class: |
F01K 3/04 20060101
F01K003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 4, 2011 |
EP |
11176574.9 |
Claims
1. A steam turbine having an outer housing and an inner housing,
comprising: a rotor, comprising a plurality of rotor blades, which
has a thrust compensating piston being arranged in a rotationally
mounted manner within the inner housing, the inner housing having
an inner housing end region which is formed around the thrust
compensating piston, a seal which seals a third pressure space
which is arranged between the inner housing end region and the
outer housing, the inner housing having a feed channel which
connects a first pressure space to a thrust compensating piston
pre-space which is arranged between the thrust compensating piston
and the inner housing, the first pressure space being arranged
between the inner housing and the outer housing, wherein the steam
turbine has a connection which connects the third pressure space in
terms of flow to the thrust compensating piston pre-space, a
further seal being provided which is arranged between the inner
housing and the outer housing, the third pressure space being
arranged between the seal and the further seal.
2. The steam turbine as claimed in claim 1, the seal being
configured as a piston ring.
3. The steam turbine as claimed in claim 1, the connection opening
into the feed channel.
4. The steam turbine as claimed in claim 1, further comprising: a
flow channel having a plurality of blade stages being formed
between the inner housing and the rotor, the inner housing having
an outward channel which is formed as a communicating line between
the flow channel downstream of a blade stage and the first pressure
space.
5. The steam turbine as claimed in claim 1, further comprising: a
valve for feeding steam into the flow channel, and an annular
cooling channel being formed in the valve, which wherein the
annular cooling channel is connected in terms of flow to the first
pressure space.
6. The steam turbine as claimed in claim 5, wherein the annular
cooling channel is connected in terms of flow to the third pressure
space.
7. The steam turbine as claimed in claim 5, wherein the valve
comprising comprises a valve diffuser, and the annular cooling
channel is arranged between the valve diffuser and the outer
housing.
8. The steam turbine as claimed in claim 5, comprising a further
cooling channel being arranged in the outer housing as a space
connection to the third pressure space.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the US National Stage of International
Application No. PCT/EP2012/065065 filed Aug. 1, 2012, and claims
the benefit thereof. The International Application claims the
benefit of European Application No. EP 11176574.9 filed Aug. 4,
2011. All of the applications are incorporated by reference herein
in their entirety.
FIELD OF INVENTION
[0002] The invention relates to a steam turbine having an outer
housing and an inner housing, a rotor, comprising a plurality of
rotor blades, which has a thrust compensating piston being arranged
in a rotationally mounted manner within the inner housing, the
inner housing having an inner housing end region which is formed
around the thrust compensating piston, a seal which seals a third
pressure space which is arranged between the inner housing region
and the outer housing, the inner housing having a feed channel
which connects the first pressure space to a thrust compensating
piston pre-space which is arranged between the thrust compensating
piston and the inner housing.
BACKGROUND OF INVENTION
[0003] In the context of the present application, a steam turbine
is understood to be every turbine or part turbine, through which a
working medium in the form of steam flows. In contrast to this, gas
and/or air flows through gas turbines as working medium which,
however, is subject to completely different temperature and
pressure conditions than the steam in a steam turbine. In contrast
to gas turbines, for example, the working medium which flows to a
part turbine and is at the highest temperature at the same time has
the highest pressure in steam turbines. An open cooling system
which is open to the flow channel can also be realized without
external supply of cooling medium in gas turbines. An external
supply of cooling medium should be provided for a steam turbine.
The prior art concerning gas turbines therefore cannot be used for
this reason to assess the subject matter of the present
application.
[0004] A steam turbine usually comprises a rotatably mounted rotor
which is fitted with blades and is arranged inside a housing or
housing shell. If heated and pressurized steam flows through the
interior of the flow channel, which interior is formed by the
housing shell, the rotor is set in rotation by the steam via the
blades. The blades of the rotor are also called rotor blades.
Moreover, stationary guide blades are usually fixed on the inner
housing, which guide blades reach into the intermediate spaces of
the rotor blades along an axial extent of the body. A guide blade
is usually held at a first point along an inner side of the steam
turbine housing. Here, it is usually part of a guide blade row
which comprises a number of guide blades which are arranged on the
inner side of the steam turbine housing along an inner
circumference. Here, each guide blade points radially to the inside
with its turbine blade. A guide blade row at said first point along
the axial extent is also called a guide blade cascade or guide
blade ring. A number of guide blade rows are usually connected one
behind another. Accordingly, a further second blade is held along
the inner side of the steam turbine housing at a second point along
the axial extent behind the first point. A pair of a guide blade
row and a rotor blade row is also called a blade stage.
[0005] The housing shell of a steam turbine of this type can be
formed from a number of housing segments. The housing shell of the
steam turbine is understood as being, in particular, the stationary
housing component of a steam turbine or of a part turbine, which
housing component has an interior along the longitudinal direction
of the steam turbine in the form of a flow channel which is
provided for the working medium in the form of steam to flow
through. Depending on the type of steam turbine, this can be an
inner housing and/or a guide blade carrier which does not have an
inner housing or a guide blade carrier.
[0006] For reasons of efficiency, the design of a steam turbine of
this type for what are known as "high steam parameters", that is to
say, in particular, high steam pressures and/or a high steam
temperature, can be desirable. However, a temperature increase, in
particular, is not possible to an unlimited extent for material
reasons. In order to make reliable operation of the steam turbine
possible here, even in the case of particularly high temperatures,
cooling of individual structural elements or components can
therefore be desirable. The temperature resistance of the
components is usually limited depending on the choice of material.
Without efficient cooling, substantially more expensive materials
(for example, nickel-based alloys) would be necessary in the case
of rising temperatures.
[0007] In the case of the previously known cooling methods, in
particular for a steam turbine body in the form of a steam turbine
housing or a rotor, a distinction is to be made between active
cooling and passive cooling. In the case of active cooling, cooling
is brought about by a cooling medium which is fed to the steam
turbine body separately, that is to say in addition to the working
medium. In contrast, passive cooling takes place merely by suitable
routing or use of the working medium. Up to now, steam turbine
bodies have preferably been cooled passively.
[0008] In order to achieve higher degrees of efficiency in the case
of electricity generation by way of fossil fuels, there is the need
to use higher steam parameters in a turbine than previously
customary, that is to say higher pressures and temperatures. In
high temperature steam turbines, temperatures partly far above
500.degree. C. are provided in the case of steam as working
medium.
[0009] The previously known cooling methods for a steam turbine
housing provide, insofar as they are active cooling methods at all,
at any rate targeted incident flow of a separate turbine part to be
cooled, and are restricted to the inflow region of the working
medium, at any rate with incorporation of the first guide blade
ring. In the case of loading of customary steam turbines with
higher steam parameters, this can lead to increased thermal loading
which acts on the entire turbine and could be reduced only
insufficiently by an above-described customary cooling arrangement
of the housing. Steam turbines which operate in principle with
higher steam parameters in order to achieve higher degrees of
efficiency require improved cooling, in particular of the housing
and/or of the rotor, in order to compensate to a sufficient extent
for higher thermal loading of the steam turbine. There is the
problem here that, if previously customary turbine materials are
used, the increasing loading of the steam turbine body by increased
steam parameters can lead to disadvantageous thermal loading of the
steam turbine which reduces the service life. As a consequence of
this, it is scarcely possible any more to produce steam turbines of
this type economically.
[0010] To this end, it is important, in addition to the rotor and
the housing including screws, to also design the valve connection
itself to withstand high temperatures and high pressures.
SUMMARY OF INVENTION
[0011] It is an object of the invention to specify a steam turbine
which can be cooled particularly effectively even in the high
temperature range.
[0012] This object is achieved by a steam turbine having the
features as described herein.
[0013] Advantageous developments are specified further herein.
[0014] In one advantageous development, the seal is configured as a
piston ring, which leads to rapid and inexpensive manufacture of
the steam turbine according to the invention.
[0015] In a further advantageous development, the steam turbine
comprises a valve for feeding steam into the flow channel, cooling
channels being formed in the valve connection which are connected
in terms of flow to the first pressure space. The cooling channels
are advantageously connected in terms of flow to the third pressure
space.
[0016] The invention proceeds from the concept that inherent
cooling of components is possible, in which a targeted pressure
flow is made possible or is forced via different pressure levels.
The pressure in the first pressure space is thus greater than the
pressure in the third pressure space. The cooling channels which
are arranged in such a way that they flow around temperature-loaded
components are accordingly flowed around forcibly by cooler steam.
The consequence is that a considerable increase in the cooling
effect for components of the valve connection is possible. Said
cooling effect is achieved by virtue of the fact that the third
pressure space is connected directly to the thrust compensating
piston pre-space.
[0017] The cooling channels are advantageously arranged between a
valve diffuser and the outer housing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The invention will be explained in greater detail using an
exemplary embodiment. Components with identical designations have
substantially the same method of operation. In the drawing:
[0019] FIG. 1 shows a cross-sectional view of a steam turbine
according to the invention, and
[0020] FIG. 2 shows a cross-sectional view, in a section through
the inflow of the steam turbine according to the invention.
DETAILED DESCRIPTION OF INVENTION
[0021] FIG. 1 shows a cross section through a steam turbine 1. The
steam turbine 1 has an outer housing 2 and an inner housing 3. The
inner housing 3 and the outer housing 2 have a fresh steam feed
channel which is described in greater detail in FIG. 2. A rotor 5
which has a thrust compensating piston 4 is arranged in a
rotationally mounted manner within the inner housing 3. The rotor
is usually configured so as to be rotationally symmetrical about a
rotational axis 6. The rotor 5 comprises a plurality of rotor
blades 7. The inner housing 3 has a plurality of guide blades 8. A
flow channel 9 is formed between the inner housing 3 and the rotor
5. The flow channel 9 comprises a plurality of blade stages which
are formed in each case from a row of rotor blades 7 and a row of
guide blades 8.
[0022] Fresh steam flows via the fresh steam feed channel into an
inflow opening 10 and flows from there in a flow direction 11
through the flow channel 9 which extends substantially parallel to
the rotational axis 6. The fresh steam expands and cools in the
process. Thermal energy is converted in the process into rotational
energy. The rotor 5 is set in a rotational movement and can drive,
for example, a generator for electric power generation.
[0023] Depending on the blade type of the guide blades 8 and rotor
blades 7, thrust with a greater or lesser magnitude of the rotor 5
is produced in the flow direction 11. The thrust compensating
piston 4 is usually configured in such a way that a thrust
compensating piston pre-space 12 is formed and is loaded with a
defined pressure. Here, the thrust compensating piston pre-space 12
is upstream of the thrust compensating piston 4 as viewed in the
flow direction 11. A counterforce which counteracts a thrust force
13 of the blade path is produced by steam having a particular
pressure being fed into the thrust compensating piston pre-space
12.
[0024] During operation, steam flows into the inflow opening 10.
The fresh steam feed is shown symbolically by the arrow 13a. Here,
the fresh steam usually has temperature values of, for example, up
to 625.degree. C. and a pressure of up to 350 bar. The fresh steam
flows through the flow channel 9 in the flow direction 11. After a
blade stage, the steam flows into the thrust compensating piston
pre-space 12 via a connection which comprises an outward channel
14, a first pressure space 15 and a feed channel 16.
[0025] In particular, the steam flows into the first pressure space
15 which is formed between the inner housing 3 and the outer
housing 2 via an outward channel 14 which is formed as a
communicating tube between a first pressure space 15 and the flow
channel 9 after a blade stage. A pressure of p.sub.1 prevails in
said first pressure space 15. The steam which is situated in the
first pressure space 15 between the inner housing 3 and the outer
housing 2 then has lower temperature and pressure values. Said
steam flows via a feed channel 16 which is formed as a
communicating tube between the first pressure space 15 and the
thrust compensating piston pre-space 12.
[0026] The thrust compensating piston pre-space 12 is arranged in
an axial direction 17 between the thrust compensating piston 4 and
the inner housing 3. The thrust compensating piston pre-space 12
can also be called a second pressure space. A pressure p.sub.2
prevails in said second pressure space.
[0027] Fresh steam which flows into the inflow opening 10 flows for
the greatest part through the flow channel 9 in the flow direction
11. A smaller part flows as leakage steam into a leak sealing space
18. This leak sealing space 18 is formed between the inner housing
3 and the rotor 5. Here, the leakage steam flows substantially in a
counterdirection 19. Here, the counterdirection 19 is oriented in
the opposite direction to the flow direction 11. The leakage steam
flows into the flow channel 9 via a crosswise return channel 20
which as a communicating tube between the sealing space 18, which
is formed between the rotor 5 and the housing 3, and an inflow
space 26 which is arranged after a blade stage. Here, with respect
to the flow direction 11, the crosswise return channel 20 is formed
substantially perpendicularly from the sealing space 18 toward the
first pressure space 15, substantially parallel after a deflection
21 and substantially perpendicularly after a second deflection 22,
without, however, connecting the sealing space 18 to the first
pressure space 15.
[0028] In an alternative embodiment, the inner housing 3 and the
outer housing 2 can be configured with an overload inflow line 23
(not shown in greater detail). External steam flows into the
overload inflow line 23 via a separate inflow.
[0029] In one preferred exemplary embodiment, the outward channel
14 is connected to the flow channel 9 after a return blade stage 24
and the crosswise return channel 20 is connected to the flow
channel 9 after a crosswise return blade stage 25. Here, the
crosswise return blade stage 25 is arranged after the return blade
stage 24 in the flow direction 11 of the flow channel 9, with
regard to expansion of the steam.
[0030] In one particularly preferred exemplary embodiment, the
return blade stage 24 is the fourth blade stage and the crosswise
return blade stage 25 is the fifth blade stage.
[0031] A seal 27 is arranged between the inner housing 3 and the
outer housing 2 in the region of the thrust compensating piston 4.
Said seal 27 is configured appropriately for example as a piston
ring and is arranged in a groove 28 in the inner housing 3. As a
result, the seal 27 separates the first pressure space 15 from a
third pressure space 29. A pressure p.sub.3 prevails in the third
pressure space 29. The pressure p.sub.3 can be approximately equal
to the pressure p.sub.1. A further seal 30 delimits the third
pressure space 29. The further seal 30 is arranged between the
inner housing 3 and the outer housing 2 and separates the third
pressure space 29 from the fourth pressure space 31, in which the
pressure p.sub.4 prevails.
[0032] The third pressure space 29 is connected via a direct
connection 32 to the thrust compensating piston pre-space 12. The
pressure p.sub.2 prevails in the thrust compensating piston
pre-space, wherein p.sub.2<p.sub.3. The connection 32 represents
a flow connection and makes it possible that steam which is
situated in the third pressure space 29 can flow into the thrust
compensating piston pre-space 12. The steam present in the fourth
pressure space 31 flows in the inner housing end region 33 onto a
thrust compensating piston surface 34 of the thrust compensating
piston 4.
[0033] FIG. 2 shows a cross section through the steam turbine 1 in
a section through an inflow 35. The inflow 35 comprises a valve
diffuser 36. Fresh steam flows from the valve diffuser 36 into the
inflow opening 10 and from there, as described with respect to FIG.
1, through the flow channel 9. The steam which has flowed into the
first pressure space 15 can flow partially into an annular cooling
channel 37 which is formed between the valve diffuser 36 and the
outer housing 2. At a reversal point 38, the steam flows via a
further cooling channel 39 in the outer housing 2 to the third
pressure space 29. From the third pressure space 29, the steam
flows via the connection 32 into the thrust compensating piston
pre-space 12. Since the pressure p.sub.1>p.sub.3>p.sub.4, a
targeted forcible flow is produced by this component region as a
result which advantageously cools the valve connection 40.
Effective cooling of the valve connection 40 is therefore possible,
without external cooling steam being used. Here, the valve diffuser
36 is arranged sealingly on the inner housing 3.
[0034] Contactless sealing elements, such as sealing bands, which
realize pressure dissipation and separation of the pressure spaces
are usually arranged between the rotor 5 and the inner housing 3 in
the region of the thrust compensating piston 4, in particular in
the leakage sealing space 19 and a second leakage sealing space 41.
In order to ensure the cooling of the valve connection 40, a return
of the steam is necessary from the thrust compensating piston
pre-space 12 via the partial region of the sealing space 18,
further via the crosswise return channel 20 to the inflow space 26
in the flow channel 9.
* * * * *