U.S. patent application number 13/125978 was filed with the patent office on 2011-10-20 for gas turbine having cooling insert.
Invention is credited to Fathi Ahmad, Christian Lerner.
Application Number | 20110255956 13/125978 |
Document ID | / |
Family ID | 40474905 |
Filed Date | 2011-10-20 |
United States Patent
Application |
20110255956 |
Kind Code |
A1 |
Ahmad; Fathi ; et
al. |
October 20, 2011 |
Gas turbine having cooling insert
Abstract
A gas turbine including a plurality of rotor blades assembled
into rotor blade rows and arranged on a turbine shaft and including
a plurality of guide vanes assembled into guide van rows and
mounted on a turbine housing by means of a guide van carrier is
provided. The guide vane carrier includes a plurality of cooling
air holes, and has a particularly high efficiency, while
maintaining maximum operating reliability. Therefore, a cooling
insert is introduced into a cooling air hole.
Inventors: |
Ahmad; Fathi; (Kaarst,
DE) ; Lerner; Christian; (Dorsten, DE) |
Family ID: |
40474905 |
Appl. No.: |
13/125978 |
Filed: |
September 4, 2009 |
PCT Filed: |
September 4, 2009 |
PCT NO: |
PCT/EP2009/061461 |
371 Date: |
June 28, 2011 |
Current U.S.
Class: |
415/115 |
Current CPC
Class: |
F01D 5/189 20130101;
F05D 2260/201 20130101; F01D 25/14 20130101 |
Class at
Publication: |
415/115 |
International
Class: |
F01D 5/08 20060101
F01D005/08 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 27, 2008 |
EP |
08018754.5 |
Claims
1.-8. (canceled)
9. A gas turbine, comprising: a plurality of rotor blades; a
plurality of stator blades; a turbine shaft; a turbine casing; a
stator blade carrier; and a cooling insert, wherein the plurality
of rotor blades are assembled to form rotor blade rows and are
arranged on the turbine shaft, and wherein the plurality of stator
blades are assembled to form stator blade rows and are fastened on
the turbine casing by means of the stator blade carrier, wherein
the stator blade carrier includes a plurality of cooling air holes,
and wherein a cooling insert, which is of tubular design and is
equipped with a plurality of wall openings arranged in a tube wall,
is introduced into at least one cooling air hole for the tube wall
cooling.
10. The gas turbine as claimed in claim 9, wherein the plurality of
wall openings are separated from each other by means of a plurality
of ribs.
11. The gas turbine as claimed in claim 9, wherein the respective
cooling insert comprises a turbulator.
12. The gas turbine as claimed in claim 9, wherein the plurality of
wall openings are formed as impingement cooling holes.
13. The gas turbine as claimed in claim 9, wherein the respective
cooling insert comprises screw thread-like structures.
14. The gas turbine as claimed in claim 9, wherein the respective
cooling insert is produced from the same material as the stator
blade carrier.
15. The gas turbine as claimed in claim 9, wherein a cooling air
feed to the plurality of cooling air holes is adapted to the
cooling characteristics of the respective cooling insert.
16. A gas and steam turbine plant, comprising: a gas turbine,
comprising: a plurality of rotor blades, a plurality of stator
blades, a turbine shaft, a turbine casing, a stator blade carrier,
and a cooling insert, wherein the plurality of rotor blades are
assembled to form rotor blade rows and are arranged on the turbine
shaft, and wherein the plurality of stator blades are assembled to
form stator blade rows and are fastened on the turbine casing by
means of the stator blade carrier, wherein the stator blade carrier
includes a plurality of cooling air holes, and wherein a cooling
insert, which is of tubular design and is equipped with a plurality
of wall openings arranged in a tube wall, is introduced into at
least one cooling air hole for the tube wall cooling.
17. The gas and steam turbine plant as claimed in claim 16, wherein
the plurality of wall openings are separated from each other by
means of a plurality of ribs.
18. The gas and steam turbine plant as claimed in claim 16, wherein
the respective cooling insert comprises a turbulator.
19. The gas and steam turbine plant as claimed in claim 16, wherein
the plurality of wall openings are faulted as impingement cooling
holes.
20. The gas and steam turbine plant as claimed in claim 16, wherein
the respective cooling insert comprises screw thread-like
structures.
21. The gas and steam turbine plant as claimed in claim 16, wherein
the respective cooling insert is produced from the same material as
the stator blade carrier.
22. The gas and steam turbine plant as claimed in claim 16, wherein
a cooling air feed to the plurality of cooling air holes is adapted
to the cooling characteristics of the respective cooling insert.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the US National Stage of International
Application No. PCT/EP2009/061461, filed Sep. 4, 2009 and claims
the benefit thereof. The International Application claims the
benefits of European Patent Office application No. 08018754.5 EP
filed Oct. 27, 2008. All of the applications are incorporated by
reference herein in their entirety.
FIELD OF INVENTION
[0002] The invention refers to a gas turbine with a number of rotor
blades which in each case are assembled to form rotor blade rows
and arranged on a turbine shaft, and with a number of stator blades
which in each case are assembled to form stator blade rows and
fastened on a turbine casing by means of a stator blade carrier,
wherein the stator blade carrier has a number of cooling air
holes.
BACKGROUND OF INVENTION
[0003] Gas turbines are used in many fields for driving generators
or driven machines. In this case, the energy content of a fuel is
used for producing a rotational movement of a turbine shaft. For
this, the fuel is combusted in a combustion chamber, wherein
compressed air is fed from an air compressor. The operating medium,
under high pressure and under high temperature, which is produced
in the combustion chamber as a result of combusting the fuel is
directed in this case through a turbine unit, which is connected
downstream of the combustion chamber, where it expands, performing
work.
[0004] For producing the rotational movement of the turbine shaft,
in this case a number of rotor blades, which customarily are
assembled into blade groups or blade rows and drive the turbine
shaft via an impulse transfer from the operating medium, are
arranged on this turbine shaft. For flow guiding of the operating
medium in the turbine unit, moreover, stator blades, which are
connected to the turbine casing and assembled to form stator blade
rows, are customarily arranged between adjacent rotor blade
rows.
[0005] The combustion chamber of the gas turbine can be constructed
as a so-called annular combustion chamber, in which a multiplicity
of burners, which are arranged around the turbine shaft in the
circumferential direction, lead into a common combustion chamber
space which is enclosed by a high temperature-resistant surrounding
wall. For this, the combustion chamber in its entirety is designed
as an annular structure. In addition to a single combustion
chamber, provision may also be made for a multiplicity of
combustion chambers.
[0006] A first stator blade row of a turbine unit as a rule
directly adjoins the combustion chamber and together with the
directly following rotor blade row, as seen in the flow direction
of the operating medium, forms a first turbine stage of the turbine
unit to which further turbine stages are customarily connected.
[0007] The stator blades in this case are fixed in each case on a
stator blade carrier of the turbine unit via a blade root which is
also referred to as a platform. In this case, the stator blade
carrier can comprise an insulating segment for fastening the
platforms of the stator blades. Between the platforms--which are
arranged in a spaced apart manner in the axial direction of the gas
turbine--of the stator blades of two adjacent stator blade rows, a
guide ring is arranged in each case on the stator blade carrier of
the turbine unit. Such a guide ring, by means of a radial gap, is
at a distance from the blade tips of the rotor blades of the
associated rotor blade row which are fixed on the turbine shaft at
the same axial position. As a result, the platforms of the stator
blades and the guide rings, which in their turn are possibly of a
segmented construction in the circumferential direction of the gas
turbine, form a number of wall elements of the turbine unit,
constituting the outer limit of a flow passage for the operating
medium.
[0008] The aforesaid guide rings, as known from U.S. Pat. No.
3,864,056, for example, in this case can be of a cooled design.
According to U.S. Pat. No. 3,864,056, the guide ring segments are
hooked to the stator blade carrier. In its wall, provision is made
for a feed of cooling air to the guide rings in the form of a
through-opening. A pretensioned sleeve, which presses the guide
ring segment against the hooks, is screwed in the through-opening,
wherein the cooling air which flows inside the sleeve can transfer
via openings into the cold gas-side rear space of the guide ring
segment and is further used there for cooling the guide ring
segment. GB 1 524 956 shows a fastening and cooling of guide ring
segments which is alternative to this.
[0009] Furthermore, provision can also be made in the stator blade
carrier for holes through which are guided measuring lances with
which the radial gap between guide ring segment and rotor blade tip
is recorded. A cooled measuring lance is known from US 2006/0140754
A1 in this case.
[0010] In the design of such gas turbines, in addition to the
achievable output, a particularly high efficiency is customarily a
design aim. An increase of the efficiency in this case can be
achieved, for thermodynamic reasons, basically by increasing the
exit temperature at which the operating medium flows out of the
combustion chamber and flows into the turbine unit. Therefore,
temperatures of about 1200.degree. C. to 1500.degree. C. are aimed
at and also achieved for such gas turbines.
[0011] With such high temperatures of the operating medium,
however, the components and parts which are exposed to this are
subjected to high thermal loads. Therefore, particularly the stator
blade carrier of the gas turbine is customarily produced from cast
steel since this is suitable for withstanding the high temperatures
inside the gas turbine. Furthermore, provision is customarily made
in the stator blade carrier for cooling air holes through which
cooling air from the outer regions of the gas turbine flow into the
interior and cool the stator blade carrier in the process. In this
case, a plurality of cooling air reservoirs at different
temperatures and pressures are customarily provided between turbine
casing and stator blade carrier.
[0012] Adequate cooling of the stator blade carrier inter alia is
therefore required since excessively high temperatures and
consequently excessively high temperature differences in different
operating states result in thermal deformations of the stator blade
carrier which have to be taken into consideration in the
construction of the gas turbine. In this case, the gap dimensions
especially of the radial gaps between rotor blade tips and inner
wall must be correspondingly large in their selection in order to
compensate for variances which are created as a result of
deformation of the stator blade carrier and so to prevent damage to
the gas turbine. Enlarging the gaps, however, results in a lowering
of the efficiency of the gas turbine. Consequently, adequate
cooling should always be ensured for reducing deformation of the
stator blade carrier.
[0013] On the other hand, intense cooling of the stator blade
carrier also means high consumption of cooling air which then flows
into the interior of the gas turbine. This lowers the temperature
inside the gas turbine and can therefore also lower the efficiency
of the gas turbine.
SUMMARY OF INVENTION
[0014] The invention is therefore based on the object of disclosing
a gas turbine which has particularly high efficiency while
maintaining the best possible operational reliability.
[0015] This object is achieved according to the invention by a
cooling insert being introduced into at least one cooling air hole
for its wall cooling.
[0016] The invention in this case starts from the consideration
that particularly high efficiency can be achieved by increasing the
temperature inside the gas turbine. This can be effected by
reducing the cooling air consumption, i.e. by reducing the amount
of cooling air which is introduced into the interior of the gas
turbine. A reduction of the amount of cooling air, however, results
in an increase of the temperature of the stator blade carrier since
less air then flows through its cooling air holes and consequently
less heat is transported away from the stator blade carrier. This,
however, can result in deformation of the stator blade carrier
which would then have to be taken into consideration in the
construction of the gas turbine. Therefore, the available cooling
air should be used particularly effectively for cooling, i.e. a
largest possible amount of heat should be transported away with a
smallest possible amount of cooling air. Based on the knowledge
that a turbulent flow enables a better heat transfer than a laminar
flow, it is therefore advisable to create a flow vortex in the
cooling air holes for more efficient wall cooling. This can be
achieved by a cooling insert being introduced into the cooling air
holes. The more efficient wall cooling compensates for the reduced
stator blade carrier cooling which would occur in the cooling air
holes on account of the reduced cooling air flow rate.
[0017] The cooling insert is of tubular design and equipped with
window-like wall openings arranged in its tube wall. As a result of
this, it is possible that the cooling air which flows through the
cooling insert can furthermore come into contact with the wall of
the cooling air holes of the stator blade carrier in order to
extract the heat energy from these.
[0018] According to an especially preferred embodiment, the wall
openings are separated from each other over a large area and by
means of ribs, as a result of which the cooling air can come into
contact with the wall of the cooling air hole over a large
area.
[0019] In an advantageous embodiment, the respective cooling insert
comprises at least one turbulator. Turbulators are small
projections, i.e. generally applied surface interruptions which
allow a laminar flow to be converted into a turbulent flow. These
can be formed by the ribs, for example, or in the form of raised
wires, sheet metal corners or the like. Even if the flow in the
cooling air hole is already turbulent, these turbulators ensure an
even better heat transfer and therefore overall ensure better
cooling of the stator blade carrier with reduced cooling air
consumption.
[0020] The cooling insert can advantageously also be formed as an
impingement cooling insert, for example when the wall openings are
formed as impingement cooling holes which are distributed in a
grid-like manner. The cooling air which flows through the cooling
insert can discharge through the impingement cooling holes in a
radial manner and in so doing impinge transversely upon the cooling
air hole walls of the stator blade carrier. As a result of this,
particularly efficient cooling of the stator blade carrier is
achieved.
[0021] The respective cooling insert advantageously comprises a
screw thread-like structure. As a result of a screw thread-like
structure, a swirl can be imposed upon the flow inside the cooling
air hole, which on the one hand ensures a flow vorticity, and on
the other hand results in longer residence of the cooling air in
the cooling air hole. As a result, a better heat transfer from the
material of the stator blade carrier to the cooling air flowing
through is also ensured.
[0022] The respective cooling insert is advantageously produced
from the same material as the stator blade carrier. As a result,
possible complications on account of different material selection
of the cooling insert and of the stator blade carrier, such as a
different thermal expansion, can be avoided and overall a
comparatively simpler construction is possible.
[0023] By introducing cooling inserts into the cooling air holes of
the stator blade carrier, the cooling characteristics of these
cooling air holes are altered. For achieving the same cooling
effect, a smaller amount of cooling air which is introduced is
necessary. Consequently, the cooling air feed to the cooling air
holes should advantageously be adapted to the cooling
characteristics of the respective cooling insert. This means that
temperature and pressure of the cooling air which is introduced are
optimized to the new, altered characteristics with regard to
cooling by means of the cooling inserts.
[0024] Such a gas turbine is advantageously used in a gas and steam
turbine plant.
[0025] The advantages which are associated with the invention are
especially that by introducing cooling inserts into the cooling air
holes of the stator blade carrier an altogether better efficiency
of the gas turbine is achieved as a result of the improved cooling
with reduced amount of cooling air at the same time. Furthermore,
such inserts can be introduced particularly simply and can also be
applied correspondingly relatively simply in the manner of a
retrofit in the case of older gas turbines. The cooling inserts can
also be flexibly adapted to the respective requirements with regard
to cooling and cooling air consumption.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] An exemplary embodiment of the invention is explained in
more detail with reference to a drawing. In the drawing:
[0027] FIG. 1 shows a half section through a gas turbine,
[0028] FIG. 2 shows a half section through the lower half of a
cooling insert, and
[0029] FIG. 3 shows a plan view of a cooling insert.
[0030] Like parts are provided with the same designations in all
the figures.
DETAILED DESCRIPTION OF INVENTION
[0031] The gas turbine 1 according to FIG. 1 has a compressor 2 for
combustion air, a combustion chamber 4 and also a turbine unit 6
for driving the compressor 2, and a generator or a driven machine,
which is not shown. In addition, the turbine unit 6 and the
compressor 2 are arranged on a common turbine shaft 8 which is also
referred to as a turbine rotor to which the generator or the driven
machine is also connected, and which is rotatably mounted around
its center axis 9. The combustion chamber 4 which is constructed in
the style of an annular combustion chamber is equipped with a
number of burners 10 for combusting a liquid or gaseous fuel.
[0032] The turbine unit 6 has a number of rotatable rotor blades 12
which are connected to the turbine shaft 8. The rotor blades 12 are
arranged on the turbine shaft 8 in a ring-like manner and therefore
form a number of rotor blade rows. Furthermore, the turbine unit 6
comprises a number of fixed stator blades 14 which are also
fastened in a ring-like manner on a stator blade carrier 16 of the
turbine unit 6, forming stator blade rows. The rotor blades 12 in
this case serve for driving the turbine shaft 8 as a result of
impulse transfer from the operating medium M which flows through
the turbine unit 6. The stator blades 14 on the other hand serve
for flow guiding of the operating medium M between two consecutive
rotor blade rows or rotor blade rings in each case, as seen in the
flow direction of the operating medium M. A consecutive pair,
consisting of a ring of stator blades 14 or a stator blade row and
a ring of rotor blades 12 or a rotor blade row, in this case is
also referred to as a turbine stage.
[0033] Each stator blade 14 has a platform 18 which, for fixing of
the respective stator blade 14 on a stator blade carrier 16 of the
turbine unit 6, is arranged as a wall element. The platform 18 in
this case is a thermally comparatively heavily loaded component
which forms the outer limit of a hot gas passage for the operating
medium M which flows through the turbine unit 6. Each rotor blade
12 is fastened in a similar way on the turbine shaft 8 via a
platform 19 which is also referred to as a blade root.
[0034] Between the platforms 18--which are arranged in a spaced
apart manner--of the stator blades 14 of two adjacent stator blade
rows, a guide ring 21 is arranged in each case on a stator blade
carrier 16 of the turbine unit 6. The outer surface of each guide
ring 21 in this case is also exposed to the hot operating medium. M
which flows through the turbine unit 6 and in the radial direction,
as a result of a gap, is at a distance from the outer end of the
rotor blades 12 which lie opposite it. The guide rings 21 which are
arranged between adjacent stator blade rows in this case especially
serve as cover elements which protect the inner casing 16 in the
stator blade carrier or other installed components of the casing
against thermal overstress as a result of the hot operating medium
M which flows through the turbine 6.
[0035] The combustion chamber 4 in the exemplary embodiment is
designed as a so-called annular combustion chamber in which a
multiplicity of burners 10, which are arranged around the turbine
shaft 8 in the circumferential direction, lead into a common
combustion chamber space. For this, the combustion chamber 4 in its
entirety is designed as an annular structure which is positioned
around the turbine shaft 8.
[0036] Since the stator blade carrier 16 is also heated up as a
result of the high temperatures of the operating medium M, cooling
air holes are introduced into the stator blade carrier 16 through
which cooling air of different temperature and different pressure
is guided from different chambers outside the region of the stator
blade carrier 16 through the stator blade carrier 16 into the
interior of the gas turbine 1. This cooling air ensures cooling of
the stator blade carrier 16 so that thermal deformations of the
stator blade carrier 16 are reduced.
[0037] Since a large amount of cooling air, however, reduces the
temperature inside the gas turbine 1 and therefore lowers the
efficiency, the amount of cooling air which is used is to be
minimized as far as possible. In order to ensure adequate cooling
of the stator blade carrier 16, however, cooling inserts 22 are
inserted into the cooling air holes. If the cooling insert 22 is
formed as an impingement cooling insert, its outside diameter is
slightly smaller than the diameter of the cooling air hole.
[0038] A cross section through a half of such a cooling insert 22
is shown in FIG. 2. The cooling insert 22 has an essentially
cylindrical shape in order to be able to be inserted into the
existing cooling air holes. In this way, existing gas turbines can
also be retrofitted with such a cooling insert 22. Moreover, it is
of a tubular form, that is to say it can be exposed to throughflow
along its axial extent. On one side, the cooling insert 22 in this
case comprises a flange 23 for fixing.
[0039] The cooling insert 22 on its tube wall, which is circular in
cross section, has a plurality of window-like wall openings 25
which can be distributed both along its axial extent and on the
circumference. The wall openings are of comparatively large area
and are separated from each other by means of ribs 26. Such a
cooling insert 22, in contrast to the impingement cooling insert,
then has an outside diameter which corresponds to the diameter of
the cooling air hole.
[0040] The ribs 26 which extend in the circumferential direction of
the cooling insert 22 are designed as turbulators 24 on which the
air flow breaks up and the laminar flow is converted into a
turbulent flow. Other shapes and arrangements of turbulators are
also possible in this case. The turbulent flow comes into contact
with the wall of the cooling air hole of the stator blade carrier
in the region of the wall openings 25 for cooling of the wall and
of the stator blade carrier. As a result, a better heat transfer
from the material of the stator blade carrier 16 to the cooling air
is ensured. The ribs 26 and/or the turbulators 24 can also be
arranged in the style of a screw thread so that an additional swirl
is imparted to the cooling air so that the residence time and the
vorticity in the cooling air hole become greater.
[0041] FIG. 3 once more shows the cooling air insert 22 in plan
view. The flanges 23 for fixing in the cooling air holes of the
stator blade carrier 16 are again evident here. Since as a result
of the cooling insert 22 the heat transfer from the material of the
stator blade carrier 16 to the cooling air in the cooling air holes
is improved, the cooling air feed into the stator blade carrier 16
should furthermore still be adapted to the new cooling air
characteristics. As a result, a comparatively better and more
effective cooling of the stator blade carrier 16 is ensured with
lower cooling air consumption at the same time. Consequently, the
efficiency of the gas turbine 1 can be increased overall.
* * * * *