U.S. patent application number 10/552213 was filed with the patent office on 2006-09-28 for inlet coating for gas turbines.
This patent application is currently assigned to MTU Aero Engines GmbH. Invention is credited to Christian Friedrich.
Application Number | 20060213435 10/552213 |
Document ID | / |
Family ID | 33394727 |
Filed Date | 2006-09-28 |
United States Patent
Application |
20060213435 |
Kind Code |
A1 |
Friedrich; Christian |
September 28, 2006 |
Inlet coating for gas turbines
Abstract
An abradable coating for gas turbines is provided. The abradable
coating is used for sealing a radial gap between a casing (11) of
the gas turbine and rotating blades (10) of the same. The abradable
coating (13) is applied to the casing. The abradable coating (13)
is at least single-layered, at least one outer layer of the
abradable coating (13) being produced from a material having a
magnetoplumbite structure, preferably lanthanum hexaaluminate.
Inventors: |
Friedrich; Christian;
(Munich, DE) |
Correspondence
Address: |
DAVIDSON, DAVIDSON & KAPPEL, LLC
485 SEVENTH AVENUE, 14TH FLOOR
NEW YORK
NY
10018
US
|
Assignee: |
MTU Aero Engines GmbH
Dachauer Strasse 665
Muenchen
DE
80995
|
Family ID: |
33394727 |
Appl. No.: |
10/552213 |
Filed: |
April 17, 2004 |
PCT Filed: |
April 17, 2004 |
PCT NO: |
PCT/DE04/00808 |
371 Date: |
October 6, 2005 |
Current U.S.
Class: |
118/302 ;
277/415; 415/173.4 |
Current CPC
Class: |
C23C 28/347 20130101;
C23C 28/044 20130101; C23C 28/322 20130101; F01D 5/288 20130101;
F01D 5/20 20130101; C23C 30/00 20130101; C23C 28/042 20130101; Y02T
50/60 20130101; C23C 28/3455 20130101; F01D 11/122 20130101; C23C
28/345 20130101; F05D 2300/15 20130101 |
Class at
Publication: |
118/302 ;
415/173.4; 277/415 |
International
Class: |
F01D 5/20 20060101
F01D005/20 |
Foreign Application Data
Date |
Code |
Application Number |
May 17, 2003 |
DE |
103 22 339.8 |
Claims
1-7. (canceled)
8. An abradable coating for application to a casing of a gas
turbine, comprising a coating produced from a material having a
magnetoplumbite structure.
9. The abradable coating as recited in claim 8, wherein the
material is produced from lanthanum hexaaluminate.
10. The abradable coating as recited in claim 8, wherein the
abradable coating is a single-layer coating, and wherein the only
layer of the single layer coating abradable coating is produced
from lanthanum hexaaluminate.
11. The abradable coating as recited in claim 8, wherein the
abradable coating is a multi-layered coating, and an outermost
layer of the abradable coating is produced from lanthanum
hexaaluminate.
12. The abradable coating as recited in claim 11, wherein the
multi-layered coating includes an interior layer, disposed between
the outer layer of lanthanum hexaaluminate and a casing to which
the coating is applied.
13. The abradable coating as recited in claim 12, wherein the
interior layer is an adhesion-promoting layer.
14. The abradable coating as recited in claim 12, wherein the
multi-layered coating further includes an intermediate layer of
zirconium dioxide disposed between the interior layer and the outer
layer of lanthanum hexaaluminate.
15. A gas turbine comprising a plurality of rotating blades, a
casing enclosing the plurality of rotating blades; and an abradable
coating on the casing, the abradable coating sealing a radial gap
between the casing and the rotating blades, wherein the coating is
produced from a material having a magnetoplumbite structure.
16. The gas turbine as recited in claim 15, wherein the material is
produced from lanthanum hexaaluminate.
17. The gas turbine as recited in claim 15, wherein the abradable
coating is a single-layer coating, and wherein the only layer of
the single layer coating abradable coating is produced from
lanthanum hexaaluminate.
18. The gas turbine as recited in claim 15, wherein the abradable
coating is a multi-layered coating, and an outermost layer of the
abradable coating is produced from lanthanum hexaaluminate.
19. The gas turbine as recited in claim 18, wherein the
multi-layered coating includes an interior layer, disposed between
the outer layer of lanthanum hexaaluminate and the casing.
20. The gas turbine as recited in claim 19, wherein the interior
layer is an adhesion-promoting layer.
Description
[0001] The present invention is directed to an abradable coating
for gas turbines according to the definition of the species in
claim 1.
[0002] Gas turbines, such as aircraft engines, typically include a
plurality of rotating blades, as well as a plurality of stationary
guide vanes, the blades rotating together with a rotor and the
blades, as well as the guide vanes being enclosed by a fixed casing
of the gas turbine. To boost the performance of an aircraft engine,
it is vitally important that all components and subsystems be
optimized. These also include the so-called sealing systems in
aircraft engines. Maintaining a minimal gap between the rotating
blades and the fixed casing of a high-pressure gas turbine is
especially problematic in the context of aircraft engines. Namely,
in high-pressure gas turbines, the highest absolute temperatures,
as well as the greatest temperature gradients occur. This
complicates the task of maintaining the gap between the rotating
blades and the fixed casing of the compressor. This has to do,
inter alia, with the fact that the shrouds, as are used for
turbines, have been eliminated in the case of compressor
blades.
[0003] As just mentioned, the blades in the compressor are not
provided with a shroud. For that reason, the ends or tips of the
rotating blades are subjected to a direct frictional contact with
the fixed casing when rubbing into the same. Such a rubbing of the
blade tips into the casing is caused by manufacturing tolerances
produced when a minimal radial gap is set. Since the frictional
contact of the tips of the rotating blades against the casing
causes material to be ablated from the tips of the rotating blades,
the gap can become undesirably enlarged over the entire periphery
of the casing and rotor. To overcome this problem, it is already
known from related art methods, to hardface the ends or tips of the
rotating blades with a hard coating or with abrasive particles.
[0004] Another way to ensure that the tips of the rotating blades
to not become worn and to provide an optimized sealing action
between the ends or tips of the rotating blades and the fixed
casing is to coat the casing with a so-called abradable coating.
When material is ablated from an abradable coating, the radial gap
is not enlarged over the entire periphery, but rather, typically,
only in a sickle shape. This makes it possible to avoid a decline
in the engine performance. Casings having an abradable coating are
generally known from the related art.
[0005] The EP 0765 951 B 1 describes an abradable coating for a gas
turbine whose outer layer or top layer of the abradable coating,
which is in contact with the tips of the blades, is produced from
zirconium dioxide. Another abradable coating is known from the U.S.
Pat. No. 4,936,745.
[0006] Against this background, the object of the present invention
is to devise a novel type of abradable coating for gas
turbines.
[0007] This objective is achieved in that the abradable coating
mentioned at the outset is further refined by the features set
forth in the characterizing portion of claim 1.
[0008] The abradable coating according to the present invention for
gas turbines is used for sealing a radial gap between a fixed
casing of the gas turbine and rotating blades of the same. The
abradable coating is applied to the casing. In accordance with the
present invention, the abradable coating is at least
single-layered, at least one outer layer of the abradable coating
being fabricated from a material having a magnetoplumbite
structure, preferably from lanthanum hexaaluminate. Accordingly,
the present invention provides for the outer layer of the abradable
coating, which first comes in contact with the rotating blades, to
no longer be produced from zirconium dioxide, but preferably from
lanthanum hexaaluminate.
[0009] In accordance with one advantageous embodiment of the
present invention, the abradable coating is multi-layered, the
outermost layer of the abradable coating, which is first able to be
contacted by ends of the blades, being fabricated from lanthanum
hexaaluminate. In this case, at least one additional, interior
layer is disposed between the outer layer of lanthanum
hexaaluminate and the casing. A first interior layer is formed as
an adhesion-promoting layer; a second interior layer is produced
from zirconium dioxide and is disposed between the first interior
layer and the layer of lanthanum hexaaluminate. The second interior
layer of zirconium dioxide is provided for increasing the useful
life of the abradable coating.
[0010] Preferred embodiments of the present invention are derived
from the dependent claims and from the following description.
[0011] The present invention is described in greater detail in the
following on the basis of exemplary embodiments, without being
limited thereto. Reference is made to the drawing, whose:
[0012] FIG. 1 shows a very schematized representation of a blade of
a gas turbine, together with a casing of the gas turbine and
including an abradable coating applied to the housing; and
[0013] FIG. 2 shows a very schematized representation of a blade of
a gas turbine, together with a casing of the gas turbine and
including an alternative abradable coating applied to the
casing.
[0014] In a highly schematized view, FIG. 1 illustrates a rotating
blade 10 of a gas turbine, which rotates against a fixed casing 11,
in the direction of arrow 12. An abradable coating 13 is disposed
on casing 11.
[0015] Abradable coating 13 is used for sealing a radial gap
between a tip, i.e., an end 14 of rotating blade 10 and fixed
casing 11. The demands placed on such an abradable coating are very
complex. Thus, the abradable coating must exhibit optimized wear
characteristics, i.e., good chip formation and removability of the
abraded material. In addition, there should be no transfer of
material to rotating blades 10. Moreover, abradable coating 13 must
exhibit a low frictional resistance. Abradable coating 13 must also
not ignite in response to rotating blades 10 rubbing against it.
Other demands placed on abradable coating 13 that are mentioned
here exemplarily include erosion resistance, temperature
resistance, resistance to heat exchange, and corrosion resistance
to lubricants and sea water.
[0016] FIG. 1 illustrates ends 14 of blades 10 coming in contact
with abradable coating 13, thereby releasing ablated material 15 in
response to the centrifugal forces occurring during operation of
the gas turbine and heating of the gas turbine. This pulverized
ablated material 15 must be prevented from causing damage to
rotating blades 10.
[0017] Along the lines of the present invention, abradable coating
13 is fabricated from a material having a magnetoplumbite
structure; in the illustrated exemplary embodiment, from lanthanum
hexaaluminate. The exemplary embodiment of FIG. 1 relates to a
single-layered abradable coating 13, the only layer of abradable
coating 13 being produced from the lanthanum hexaaluminate and
being directly deposited on casing 11. Accordingly, the present
invention provides for lanthanum hexaaluminate to be used for
fabricating the outer layer of abradable coatings, instead of the
zirconium dioxide known from the related art.
[0018] FIG. 2 illustrates a second exemplary embodiment of the
present invention. Thus, FIG. 2 shows, in turn, a rotating blade
16, which is rotating in the direction of arrow 17 relative to a
fixed housing 18. An abradable coating 19 is again disposed on
casing 18.
[0019] However, in contrast to the exemplary embodiment of FIG. 1,
abradable coating 19 of the exemplary embodiment according to FIG.
2 is not single-layered, but rather multi-layered. An outer layer
20 of abradable coating 19, which first makes contact with blades
16, is again produced in accordance with the present invention from
lanthanum hexaaluminate.
[0020] In addition, an interior layer 21 is provided between outer
layer 20 and casing 18. Interior layer 21 is an adhesion-promoting
layer, whose purpose is to improve the adhesion between casing 18
and outer layer 20. Adhesion-promoting interior layer 20 may be
metallic.
[0021] An additional intermediate layer (not shown) of zirconium
dioxide may be placed between the adhesion-promoting, interior
layer 21 and outer layer 20 of lanthanum hexaaluminate. The purpose
of this intermediate layer of zirconium dioxide is to improve the
properties of the laminar structure, in particular, to increase its
useful life.
[0022] It is noted here that three- or multi-layer abradable
coatings along the lines of the present invention may, of course,
also be provided. In accordance with the present invention,
however, the outer layer of a multi-layer abradable coating, which
first comes in contact with the rotating blades of the gas turbine,
should be produced from lanthanum hexaaluminate.
[0023] In the exemplary embodiment of FIG. 2, a so-called barrier
coating 23 is provided at end 22, i.e., at the tip of rotating
blade 16. This barrier coating 23 is essentially produced by
hardfacing of the blade tips. In the illustrated exemplary
embodiment, barrier coating 23 encompasses a plurality of
wedge-shaped elements 24, clearance spaces 25 being formed between
adjacent elements 24 of barrier coating 23. In this respect, FIG. 2
depicts a sealing system for a gas turbine, where an abradable
coating 19 according to the present invention that is deposited on
casing 18 of the gas turbine is combined with a barrier coating 23
disposed on the blade tips.
[0024] Underlying both exemplary embodiments of FIGS. 1 and 2 is
the principle according to the present invention whereby an outer
layer of an abradable coating, which comes in contact with the tips
of the rotating blades, is produced from lanthanum
hexaaluminate.
[0025] Especially beneficial properties are able to be achieved
using an abradable coating of this kind. Thus, particularly good
wear characteristics of the abradable coating are obtained. The
other demands made of the abradable coating are also fulfilled or
influenced in a beneficial way. For example, the temperature
stability and useful life of the abradable coatings are
improved.
[0026] Mention is made at this point that the abradable coating
according to the present invention is deposited on the metallic
surface of the casing using thermal spray-coating processes. The
details pertaining to such thermal spray-coating processes are
familiar to one skilled in the art whom this technical teaching
concerns.
* * * * *