U.S. patent application number 15/359793 was filed with the patent office on 2017-06-01 for casing for a turbomachine, installation safeguard and turbomachine.
The applicant listed for this patent is MTU Aero Engines AG. Invention is credited to Lothar ALBERS, Vitalis MAIRHANSER, Georg ZOTZ.
Application Number | 20170152857 15/359793 |
Document ID | / |
Family ID | 54707687 |
Filed Date | 2017-06-01 |
United States Patent
Application |
20170152857 |
Kind Code |
A1 |
ALBERS; Lothar ; et
al. |
June 1, 2017 |
CASING FOR A TURBOMACHINE, INSTALLATION SAFEGUARD AND
TURBOMACHINE
Abstract
Disclosed is a casing of a turbomachine which comprises at least
a first casing portion comprising a first material having a first
coefficient of thermal expansion and a second casing portion
comprising a second material having a second coefficient of thermal
expansion. The second casing portion comprises a casing structuring
with flow-guiding elements and is connected in a force-fitting
manner to the first casing portion by a radial press fit. Also
disclosed are an installation safeguard and a turbomachine
comprising the casing.
Inventors: |
ALBERS; Lothar; (Munich,
DE) ; ZOTZ; Georg; (Haimhausen, DE) ;
MAIRHANSER; Vitalis; (Sigmertshausen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MTU Aero Engines AG |
Munich |
|
DE |
|
|
Family ID: |
54707687 |
Appl. No.: |
15/359793 |
Filed: |
November 23, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 29/54 20130101;
F01D 25/246 20130101; Y02T 50/60 20130101; F04D 29/644 20130101;
F05D 2260/37 20130101; F04D 29/023 20130101; F04D 29/526 20130101;
Y02T 50/672 20130101; F04D 29/685 20130101 |
International
Class: |
F04D 29/02 20060101
F04D029/02; F04D 29/54 20060101 F04D029/54; F04D 29/64 20060101
F04D029/64; F04D 29/52 20060101 F04D029/52 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2015 |
EP |
15196937.5 |
Claims
1. A casing of a turbomachine, wherein the casing comprises at
least a first casing portion comprising a first material having a
first coefficient of thermal expansion (.alpha..sub.1) and a second
casing portion comprising a second material having a second
coefficient of thermal expansion (.alpha..sub.2), the second casing
portion comprising a casing structuring with flow-guiding elements
and being connected in a force-fitting manner to the first casing
portion by a radial press fit.
2. The casing of claim 1, wherein the second coefficient of thermal
expansion (.alpha..sub.2) is different from the first coefficient
of thermal expansion (.alpha..sub.1).
3. The casing of claim 2, wherein the second coefficient of thermal
expansion (.alpha..sub.2) is higher than the first coefficient of
thermal expansion (.alpha..sub.1).
4. The casing of claim 1, wherein the first coefficient of thermal
expansion (.alpha..sub.1) is lower than or equal to
10.times.10.sup.-6 per Kelvin in a temperature range of from at
least 20 degrees Celsius to 90 degrees Celsius.
5. The casing of claim 1, wherein the second coefficient of thermal
expansion (.alpha..sub.2) is higher than 10.times.10.sup.-6 per
Kelvin in a temperature range of from at least 20 degrees Celsius
and 90 degrees Celsius.
6. The casing of claim 4, wherein the second coefficient of thermal
expansion (.alpha..sub.2) is higher than 10.times.10.sup.-6 per
Kelvin in a temperature range of from at least 20 degrees Celsius
and 90 degrees Celsius.
7. The casing of claim 1, wherein the first material is or
comprises a titanium alloy.
8. The casing of claim 1, wherein the second material is or
comprises a titanium alloy or a steel.
9. The casing of claim 8, wherein the second material is or
comprises a titanium alloy or a steel.
10. The casing of claim 1, wherein the flow-guiding elements are
integrally connected to the casing structuring.
11. The casing of claim 1, wherein the second casing portion is in
one part or in one piece.
12. The casing of claim 1, wherein the second casing portion is
segmented in multiple parts in circumferential direction.
13. The casing of claim 1, wherein the first casing portion is an
axially split casing portion of the casing of the turbomachine.
14. An installation safeguard, wherein the safeguard comprises the
casing of claim 1 and wherein the first casing portion comprises an
axial delimitation for positioning the second casing portion as an
installation safeguard of the second casing portion with respect to
the first casing portion.
15. The installation safeguard of claim 14, wherein the axial
delimitation is a radial step.
16. The installation safeguard of claim 14, wherein the second
casing portion comprises at least one radially offset portion,
which extends beyond the axial delimitation of the first casing
portion.
17. A turbomachine, wherein the turbomachine comprises the casing
of claim 1.
18. The turbomachine of claim 17, wherein the turbomachine is a
compressor.
19. The turbomachine of claim 18, wherein the compressor is a
high-pressure compressor.
20. The turbomachine of claim 17, wherein the turbomachine is an
aero engine.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority under 35 U.S.C.
.sctn.119 of European Patent Application No. 15196937.5, filed Nov.
30, 2015, the entire disclosure of which is expressly incorporated
by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a casing for a
turbomachine, to an installation safeguard, and to a
turbomachine.
[0004] 2. Discussion of Background Information
[0005] Casing structurings with flow-guiding elements are often
used in turbomachines, in particular in gas turbines and in the
compressors thereof. A casing structuring of this type with
flow-guiding elements is referred to as "Casing Treatment", CT for
short. Casing structurings have the task of increasing an
aerodynamically stable operating range, in particular in
compressors, through an optimization of a surge margin. An
optimized surge margin allows for higher compressor pressures and
therefore higher compressor loading. The disturbances responsible
for a local and ultimately for the pumping of the compressor arise
at casing-side ends of the rotor blades of one or more compressor
stages or at the hub-side, radially internal ends of the guide
vanes, since it is in these regions that the aerodynamic loading in
the compressor is at its greatest. The flow in the region of the
blade or vane ends is stabilized by the casing structurings.
[0006] In view of the foregoing, it would be advantageous to have
available a further casing with at least one casing structuring in
a turbomachine.
SUMMARY OF THE INVENTION
[0007] The present invention provides a casing of a turbomachine,
which casing comprises at least a first casing portion comprising a
first material having a first coefficient of thermal expansion
(.alpha..sub.1) and a second casing portion comprising a second
material having a second coefficient of thermal expansion
(.alpha..sub.2). The second casing portion comprises a casing
structuring with flow-guiding elements and is connected in a
force-fitting manner to the first casing portion by a radial press
fit.
[0008] In one aspect of the casing, the second coefficient of
thermal expansion (.alpha..sub.2) may be different from the first
coefficient of thermal expansion (.alpha..sub.1). For example, the
second coefficient of thermal expansion (.alpha..sub.2) may be
higher than the first coefficient of thermal expansion
(.alpha..sub.1).
[0009] In another aspect of the casing, the first coefficient of
thermal expansion (.alpha..sub.1) may be lower than or equal to
10.times.10.sup.-6 per Kelvin in a temperature range of from at
least 20 degrees Celsius to 90 degrees Celsius and/or the second
coefficient of thermal expansion (.alpha..sub.2) may be higher than
10.times.10.sup.-6 per Kelvin in a temperature range of from at
least 20 degrees Celsius and 90 degrees Celsius.
[0010] In yet another aspect, the first material may be or comprise
a titanium alloy and/or the second material may be or comprise a
titanium alloy or a steel.
[0011] In a still further aspect of the casing, the flow-guiding
elements may be integrally connected to the casing structuring
and/or the second casing portion may be in one part or in one piece
or may be segmented in multiple parts in circumferential
direction.
[0012] In another aspect, the first casing portion may be an
axially split casing portion of the casing of the turbomachine.
[0013] The present invention also provides an installation
safeguard which comprises the casing as set forth above (including
the various aspects thereof) and wherein the first casing portion
comprises an axial delimitation for positioning the second casing
portion as an installation safeguard of the second casing portion
with respect to the first casing portion.
[0014] In one aspect of the safeguard, the axial delimitation may
be a radial step.
[0015] In another aspect, the second casing portion may comprise at
least one radially offset portion, which extends beyond the axial
delimitation of the first casing portion.
[0016] The present invention also provides a turbomachine which
comprises the casing set forth above (including the various aspects
thereof). For example, the turbomachine may be a compressor (e.g.,
a high-pressure compressor), or may he an aero engine.
[0017] As set forth above, the invention proposes a casing for a
turbomachine, which comprises at least a first and a second casing
portion. The first casing portion comprises a first material and
the second casing portion comprises a second material. The second
casing portion has a casing structuring with flow-guiding elements,
in particular for influencing the main flow through the
turbomachine. The second casing portion is connected in a
force-fitting manner to the first casing portion by means of a
radial press fit. The first material has a first coefficient of
thermal expansion and the second material has a second coefficient
of thermal expansion.
[0018] The installation safeguard according to the invention
comprises a casing according to the invention, the first casing
portion having an axial delimitation, in particular a radially
offset step, for positioning and for delimiting the axial
displaceability of the second casing portion. The axial
delimitation can similarly be an additional component which is
introduced into or fixed in the first casing portion or connected
to the first casing portion. A component of this type can be, for
example, a ring, in particular a snap ring, which is mounted into a
groove in the first casing portion and constitutes an axial
delimitation for the second portion. Similarly, the additional
component can be an additional ring, which is pushed into the first
casing portion.
[0019] A structural axial delimitation of this type can be referred
to as a "mistake proof feature", with which it is possible to
achieve a clear assignment of location or assignment of position
between the first and the second casing portion. On account of the
structural configuration of the second casing portion, it would
then not be possible for the casing to be mounted and assembled
given an incorrect or inadmissible second casing portion or second
casing portion rotated through 180 degrees about a radial axis.
Further casing portions, for example an axially subsequent casing
portion which can be configured as a casing portion split over the
circumference (as what is termed a "split case") or as a sealing
segment (as what is termed an "outer air seal"), can prevent or
block installation of the second casing portion given an incorrect
location or positioning of the second casing portion.
[0020] In some embodiments according to the invention, the second
casing portion has at least one radially offset portion, which
extends beyond the axial delimitation of the first casing
portion.
[0021] The turbomachine according to the invention comprises at
least one casing according to the invention. The turbomachine can
be a compressor, in particular a high-pressure compressor.
Similarly, the turbomachine can be an aero engine.
[0022] Advantageous further developments of the present invention
are respectively the subject matter of dependent claims and
embodiments.
[0023] Exemplary embodiments according to the invention can have
one or more of the features specified hereinbelow.
[0024] The casing according to the invention can be designed for
use in a high-pressure compressor, in a low-pressure compressor, in
a high-pressure turbine or in a low-pressure turbine of an aero
engine.
[0025] In a number of embodiments according to the invention, the
turbomachine is an axial turbomachine, in particular a gas turbine,
in particular an aero gas turbine.
[0026] In specific embodiments according to the invention, the
first and/or the second casing portion do not have any components
or connecting elements for connecting the first casing portion to
the second casing portion. Connecting elements of this type may be
screws, pins, rivets, grooves, hooks or similar elements.
[0027] In certain embodiments according to the invention, a casing
portion is an axial and/or a radial portion of the casing. A
portion can be referred to as a segment. A casing segmented into
axial casing portions can simplify or allow for the installation of
individual casing components in the casing. By way of example, flow
ducts for cooling can be provided in the axial divisional plane, or
casing parts segmented over the circumference can be mounted and
used in a divisional plane of axially split casing portions.
Furthermore, the manufacture, the assembly and the transportation
of the casing can be simplified with axially split casing
portions.
[0028] Materials can be metallic materials, plastics, composite
materials, ceramic materials or other materials.
[0029] The term "casing structuring" as is used herein denotes a
structuring or configuration of the casing or of a casing portion
for influencing the main flow through the turbomachine. Casing
structurings can be referred to as circulation structures or
recirculation structures. Casing structurings are often used in gas
turbines and in particular in compressors, for example in
high-pressure compressors of aero engines. With the aid of casing
structurings, it is possible to achieve or improve an
aerodynamically stable operating behavior of the turbomachine. This
can be achieved, for example, by what is termed optimization of a
surge margin. The surge margin can be designated in simplified
terms as the margin between the operating point of the turbomachine
and a critical operating point with, for example, greatly unstable
behavior with considerable pressure surges. At this critical
operating point, it is possible, for example, for flow separation
to arise at the radially outer blade or vane edge. The maximum
stage pressure ratio is often achieved in a compressor stage of the
turbomachine shortly before the critical operating point. The surge
margin can be, for example, from about 5% to about 25%. Given a
surge margin of 5%, the current operating point lies close to the
critical operating point, and given a surge margin of 25% it lies
correspondingly further away. With casing structurings as are
proposed according to the invention, the critical operating point
can be improved or shifted, such that an optimized surge margin is
made possible and higher compressor pressures and therefore higher
compressor loading are permitted. The flow in the region of the
blade or vane ends can be stabilized by the casing structurings
with flow-guiding elements.
[0030] The term "fit" as is used herein denotes a dimensional
relationship between two paired, tolerance-affected parts. In
particular, the two parts have the same nominal dimension. The
location and size of the tolerance zones can be different. Fits or
fitting systems can be standardized, for example in accordance with
DEN or ISO standards. Similarly, fits or fitting systems may not be
standardized. If the fits or fitting systems are not standardized,
the tolerances or fit specifications for nominal dimensions can
deviate from the values of the ISO standards. In particular, the
fits or fitting systems deviate from the ISO standards when using
non-ISO dimensional units, for example when using the length
dimension "inch" instead of "meter".
[0031] The term "press fit" as is used herein denotes a
force-fitting connection of two components. The press fit can be
formed by way of different diameters and/or by way of a suitable
material pairing of the two components. In particular, a suitable
material pairing comprises different materials with different
coefficients of thermal expansion a. A press fit with different
diameters can comprise components with identical or different
nominal dimensions. The components can have identical or different
interference fits, in addition to or as an alternative to the
identical or different nominal dimensions. A press tit connects two
components to one another in a force-fitting manner, such that the
two components are in contact without relative movements in
relation to one another.
[0032] In some embodiments according to the invention, the material
of the first casing portion and the material of the second casing
portion are the same. In other embodiments according to the
invention, the two materials are different.
[0033] Exemplary examples for materials of the first and/or of the
second casing portion are listed hereinbelow (coefficient of
thermal expansion .alpha.[10.sup.-6 m/(m*K)]): [0034] titanium
alloy Ti-6A1-4V [0035] (for short Ti-6-4; 6 percent by weight (% by
weight) aluminum and 4% by weight vanadium) [0036] at 20 degrees
(20.degree.) Celsius (C): .alpha.=9.times.10.sup.-6 m/(m*K) between
20.degree. C. and 200.degree. C. (20.degree.-200.degree.);
.alpha.=9.5.times.10.sup.-6 m/(K) [0037] titanium alloy
Ti-6A1-2Sn-4Zr-2Mo (Ti-6-2-4-2; 6% by weight aluminum, 2% by weight
tin, 4% by weight zirconium, 2% by weight molybdenum) [0038]
20.degree.: .alpha.=8.5.times.10.sup.-6 m/(m*K) [0039]
20.degree.-200.degree.: .alpha.=9.times.10.sup.-6 m/(m*K) [0040]
stainless steel, X5CrNiCuNb17-4-4, material DIN/EN No. 1.4548, 17-4
PH.RTM. [0041] 20.degree.-100.degree.: .alpha.=10.9.times.10.sup.-6
m/(m*K) [0042] 20.degree.-300.degree.: .alpha.=11.1.times.10.sup.-6
m/(m*K) [0043] stainless steel, X5CrNiCuNb15-5, material DIN/EN No.
1.4545, LW, 15-5 PH.RTM. [0044] 20.degree.-200.degree.:
.alpha.=10.8.times.10.sup.-6 m/(m*K) [0045] 20.degree.-200.degree.:
.alpha.=11.3.times.10.sup.-6 m/(m*K) [0046] stainless steel,
X12CrNiMoV12-3, material DIN/EN No. 1.4939, Jethete M 152.TM.
[0047] 20.degree.-200.degree.: .alpha.=11.times.10.sup.-6 m/(m*K)
[0048] 20.degree.-400.degree.: .alpha.=12.times.10.sup.-6 m/(m*K)
[0049] stainless steel, material AMS 5616 (US), ATI 418 SPL.TM.
alloy (Greek Ascoloy) [0050] 26.7.degree.-93.degree.:
.alpha.=10.5.times.10.sup.-6 m/(m*K) [0051]
26.7.degree.-204.degree.: .alpha.=11.times.10.sup.-6 m/(m*K) [0052]
26.7.degree.-427.degree.: .alpha.=11.5.times.10.sup.-6 m/(m*K)
[0053] stainless steel, material UNS N19909, INCOLOY.RTM. 909 (UNS
number: abbreviation for "Unified Numbering System for Metals and
Alloys") [0054] 20.degree.-204.degree.: .alpha.=8.times.10.sup.-6
m/(m*K) [0055] 20.degree.-425.degree.: .alpha.=7.7.times.10.sup.-6
m/(m*K) [0056] stainless steel, G-NiCr 12 Al 6 MoNb, material
DIN/EN 2.4671, IN 713C, UNS N 07713, AMS 5391 [0057]
21.degree.-93.degree.: .alpha.=5.9.times.10.sup.-6 m/(m*K) [0058]
21.degree.-204.degree.: .alpha.=6.6.times.10.sup.-6 m/(m*K) [0059]
21.degree.-425.degree.: .alpha.=7.3.times.10.sup.-6 m/(m*K)
[0060] In principle, any material can be used for the first and
second casing portion provided that the press fit is maintained
over the entire intended operating range.
[0061] The coefficient of thermal expansion, abbreviated to a, can
be referred to as the coefficient of thermal linear expansion. The
value and the unit of the coefficient of thermal linear expansion a
of, for example, 6*10.sup.-6 per Kelvin can be given as 6*10.sup.-6
m/(m*K).
[0062] In certain embodiments according to the invention, the first
coefficient of thermal expansion is different to the second
coefficient of thermal expansion. The first casing portion
comprising the first material can have a higher or a lower
coefficient of thermal expansion than the second casing portion
comprising the second material. By way of example, a second casing
portion comprising a material having a higher coefficient of
thermal expansion than the first casing portion can have the effect
that, at elevated operating temperatures, the second casing portion
undergoes greater expansion than the first casing portion. This can
have the effect that the force-fitting connection between the two
casing portions leads to an increased force fit.
[0063] In specific embodiments according to the invention, the
second coefficient of thermal expansion is lower than the first
coefficient of thermal expansion.
[0064] In some embodiments according to the invention, the first
coefficient of thermal expansion is lower than or equal to
10.times.10.sup.-6 per Kelvin in a temperature range of between at
least 20 degrees Celsius and 90 degrees Celsius.
[0065] In certain embodiments according to the invention, the
second coefficient of thermal expansion is higher than
10.times.10.sup.-6 per Kelvin in a temperature range of between at
least 20 degrees Celsius and 90 degrees Celsius.
[0066] In some embodiments according to the invention, the first
material is a titanium alloy and/or the second material is a
titanium alloy or a steel. By way of example, both materials can be
the same or different titanium alloys. In the case of different
titanium alloys, the coefficients of thermal expansion can be the
same or different.
[0067] In certain embodiments according to the invention, the
flow-guiding elements are integrally connected to the casing
structuring of the first casing portion. By way of example, the
shapes or structurings of the casing structurings including the
flow-guiding elements can be machined from a semifinished material,
for example a disk, by a cutting process, for example by milling.
Machining operations of this type can be carried out in CNC
machining centers. Alternatively, the casing structurings including
the flow-guiding elements can be produced by a generative process.
A generative process is, for example, a laser sintering process. A
generative process can be referred to as a rapid prototyping
process. A further possible process for producing flow-guiding
elements which are integrally connected to the casing structuring
of the first casing portion is the casting process.
[0068] The first casing portion can have a different number of flow
ducts (as casing structurings) and flow-guiding elements over the
circumference. Purely by way of example, about 50, about 70, about
80, about 100, about 120 or another number of flow ducts and/or
flow-guiding elements can be arranged over the circumference. The
flow ducts and/or the flow-guiding elements can be arranged
symmetrically with identical intervals to one another or
asymmetrically with different intervals to one another.
[0069] In some embodiments according to the invention, the second
casing portion is in one part or in one piece. A one-piece second
casing portion is produced from one piece. Both a second casing
portion produced in one piece from a semifinished product by a
cutting process and a second casing portion produced by a
generative process can be referred to as being produced in one
piece. In particular, no individual parts or individual components
such as, for example, flow-guiding elements are connected by means
of cohesive and/or form-fitting connections to the second casing
portion. Cohesive processes are, for example, welding or soldering,
and form-fitting connections are, for example, screws, rivets,
hooks or the like.
[0070] In specific embodiments according to the invention, the
second casing portion is segmented in multiple parts in the
circumferential direction. By way of example, the second casing
portion can have segments with circumferential angles of about 180
degrees (two segments), about 120 degrees (three segments), about
90 degrees (four segments) or about 60 degrees (six segments). The
segments can likewise have other circumferential angles. Similarly,
the circumferential angles of the segments can be different, for
example two segments with about 120 degrees and two segments with
about 60 degrees.
[0071] In some embodiments according to the invention, the first
casing portion is an axially split casing portion of the casing of
the turbomachine. An axially split first casing portion can
advantageously simplify the mounting of the second casing portion
in that the second casing portion can be inserted into the first
casing portion in the axial direction or can be connected to the
first casing portion.
[0072] Some or all of the embodiments according to the invention
can have one, several or all of the advantages specified above
and/or hereinbelow.
[0073] By means of the casing according to the invention, it is
advantageously possible to dispense with separate components or
connecting elements for connecting the first casing portion to the
second casing portion. It is thereby possible to realize a design
which is cost-effective and simple in terms of construction and
manufacturing. It is possible to constructively dispense with
further connecting elements such as, for example, screws, pins,
rivets or similar elements. On account of the press fit according
to the invention between the first and the second casing portion,
it is advantageously possible to dispense with further or
alternative anti-rotation devices of the second casing portion with
respect to the first casing portion. In particular, there is no
need for a hook or another form-fitting anti-rotation device on the
first casing portion and/or on the second casing portion in order
necessary a relative movement, in particular during the intended
operational use of the casing. The production costs can thereby
advantageously be reduced. A hook or another component is not
required if there is a press fit. Furthermore, the mounting of the
second casing portion on or at the first casing portion can
advantageously be embodied in simplified form, since, for example,
there is no need for an exact circumferential positioning for a
form-fitting connection as an anti-rotation device.
[0074] By means of the installation safeguard according to the
invention for the casing according to the invention, it is
advantageously possible to prevent erroneous installation through
an incorrect or unintended location and positioning of the second
casing portion with respect to the first casing portion. An
installation safeguard can be formed by means of an axial
delimitation in or on the first casing portion, in particular by
means of a radially offset step.
BRIEF DESCRIPTION OF THE DRAWING
[0075] The present invention will be explained by way of example
hereinbelow with reference to the appended drawing.
[0076] FIG. 1 shows a casing according to the invention of a
turbomachine having a first and a second casing portion, the second
casing portion having a flow-guiding element.
DETAILED DESCRIPTION OF EMBODIMENT OF THE INVENTION
[0077] The particulars shown herein are by way of example and for
purposes of illustrative discussion of the embodiments of the
present invention only and are presented in the cause of providing
what is believed to be the most useful and readily understood
description of the principles and conceptual aspects of the present
invention. In this regard, no attempt is made to show details of
the present invention in more detail than is necessary for the
fundamental understanding of the present invention, the description
in combination with the drawing making apparent to those of skill
in the art how the several forms of the present invention may be
embodied in practice.
[0078] FIG. 1 shows a casing 100 according to the invention of a
turbomachine having a first casing portion 1 and a second casing
portion 3, the second casing portion 3 having a flow-guiding
element 5. Furthermore, an adjustable guide vane 7, a rotor blade 9
and a main throughflow duct 11 are shown. The first casing portion
1 can be referred to as an intermediate casing (abbreviated to IMC)
or intermediate casing portion. The guide vane 7 can be mounted
rotatably (about a radial axis) in the intermediate casing 1.
[0079] The intermediate casing 1 is adjoined axially downstream by
a further casing portion 13. Said further casing portion 13 is
designed as a casing portion 13 split in the circumferential
direction. FIG. 1 shows the divisional plane in which the screw
connection 15 of the split casing portions is indicated. A casing,
or casing portion, split in the circumferential direction can be
referred to as a "split case". In particular, the casing portion 13
is split into two casing portions 13 comprising 180 degrees, for
example designed in a high-pressure compressor as a portion in a
turbomachine. Instead of 180 degrees, the circumferential angles of
the casing portions 13 split over the circumference can
alternatively comprise 120 degrees, 90 degrees, 60 degrees, 45
degrees or another circumferential angle.
[0080] A further casing component is mounted radially on the inside
of the further casing portion 13. Said further casing component is
referred to in this embodiment as a sealing segment 17. The sealing
segment 17 can be referred to as an "outer air seal" (abbreviated
to OAS). A seal element is fastened radially on the inside of the
sealing segment 17 (or is connected integrally thereto) and is
referred to hereinbelow as a stripping coating 19. By means of the
stripping coating 19, the gap between the radially outer end of the
rotor blade 9 and the sealing segment 17 can be minimized. A casing
intermediate space 21 is furthermore shown between the second
casing portion 3, the further casing portion 13 and the sealing
segment 17 and can be used, for example, as an air gap for cooling
casing components.
[0081] With the aid of the second casing portion 3, the
flow-guiding element 5 and further flow-guiding elements 5 arranged
over the circumference, local flows 23 and/or circulation fields or
recirculation fields are initiated. Said local flows 23 can
influence critical flow fields at the outer end of the rotor blade,
in that, for example, flow separation zones, fields of turbulence
etc. are stabilized and a stable flow behavior is thereby produced
in the turbomachine. Said behavior can be referred to as
aerodynamically stable operating behavior. Particularly in the case
of compressors as turbomachines, it is thereby possible to achieve
optimization of the surge margin. Numerous flow-guiding elements 5
can be arranged in the second casing portion 3 over the
circumference, in particular between 80 and 120 flow-guiding
elements 5. The second casing portion 3 can be referred to as
"casing treatment", abbreviated to CT, or as "casing treatment
ring".
[0082] The second casing portion 3 should be securely fixed in
order to achieve said effect (optimization of the surge margin) and
as a whole for reliable operation of the turbomachine, and should
be firmly connected to the second casing portion 1 without the risk
of rotation in the circumferential direction, i.e. a relative
movement between the first casing portion 1 and the second casing
portion 3. According to the invention, this connection is produced
by a radial press fit in the axial section A between the first
casing portion 1 and the second casing portion 3. The radial press
fit can be referred to as a force-fitting connection.
[0083] According to the invention, the second casing portion 3 is
connected to the first casing portion 1 by means of a radial press
fit within the axial section A. A force-fitting press fit can be
implemented substantially by means of different diameters and/or by
means of different coefficients of thermal expansion firstly of the
material of the first casing portion 1 and secondly of the material
of the second casing portion 3. If the two materials of the first
casing portion 1 and of the second casing portion 3 are the same,
e.g. on account of structural boundary conditions, the press fit is
generally realized by means of different diameters. If the two
materials are different, with different coefficients of thermal
expansion, the press fit can be realized on account of the
different coefficients of thermal expansion. In the latter case,
different diameters may additionally be used.
[0084] A radial press fit according to the invention prevents
rotation, i.e. a relative movement of the second casing portion 3
with respect to the first casing portion 1 during intended
operational use (operating mode). The operating mode can in this
case comprise all intended operating conditions with the
corresponding load situations and operating temperatures. The
operating temperatures may be, for example in an aero engine, 200
degrees Celsius to 300 degrees Celsius, or more.
[0085] Purely by way of example, the first casing portion 1 can be
produced, for example, from a titanium alloy having a first
coefficient of thermal expansion .alpha..sub.1 of from about
7.6.times.10.sup.-6 m/(m*K) to about 10.times.10.sup.-6 m/(m*K), or
can comprise such a titanium alloy, these values relating to a
temperature range of between 20 degrees Celsius and 200 degrees
Celsius. A titanium alloy of this type is, for example, the
material Ti-6A1-4V (titanium alloy comprising 6 percent by weight
aluminum and 4 percent by weight vanadium).
[0086] Similarly purely by way of example, the second casing
portion 3 can be produced, for example, from a steel alloy having a
first coefficient of thermal expansion .alpha..sub.2 of from about
10.times.10.sup.-6 m/(m*K) to about 16.times.10.sup.-6 m/(m*K), or
can comprise such a steel alloy, these values relating to a
temperature range of between 20 degrees Celsius and 200 degrees
Celsius.
[0087] Equally, the first casing portion 1 can comprise another
titanium alloy, i.e. different from the titanium alloy Ti-6A1-4V,
or can be produced therefrom. The further titanium alloy has in
particular a coefficient of thermal expansion which differs from
that of the titanium alloy Ti-6A1-4V.
[0088] Furthermore, the second casing portion 3 can comprise the
same titanium alloy, i.e. likewise the titanium alloy Ti-6A1-4V, or
can be produced therefrom. In this case, it is possible to achieve
a press fit only with different diameters if the intention is to
ensure a sufficient, i.e. for all intended operating states and
temperatures, force-fitting connection.
[0089] In particular in the axial region A, the external diameter
of the second casing portion 3 and the internal diameter of the
first casing portion 1 have the same nominal diameter (given
identical or different materials). The external diameter of the
second casing portion 3 and the internal diameter of the first
casing portion 1 may differ in terms of different fitting
dimensions. En particular, both casing portions have excess
dimensions.
[0090] At its front end region, on the left or upstream in FIG. 1,
the second casing portion 3 has a smaller diameter compared to the
diameter in the region of the press fit (axial section A).
Correspondingly, at its front end region of the cutout or bore for
the second casing portion 3, the first casing portion 1 likewise
has a smaller diameter compared to the diameter in the region of
the press fit (axial section A). A step 25 is arranged between the
two diameters of the first casing portion 1. The second casing
portion 3 can be pushed on in the axial direction only as far as
this step 25 of the first casing portion 1. A second casing portion
3 in one part over the circumference is assumed here. The step 25
delimits the axial displacement path of the second casing portion
3. This structural embodiment of the two casing portions 1, 3
allows for installation of the second casing portion 3 only in the
arrangement shown in FIG. 1. This is referred to as an installation
safeguard for the second casing portion 3 in the first casing
portion 1. If the second casing portion 3 is arranged in a manner
rotated about 180 degrees (about the radial axis r perpendicular to
the axial axis a), installation would no longer be possible, since
the front end region of the second casing portion 3 with the
smaller diameter would then no longer be able to be installed on
account of the sealing segment 17, or would block this. This
structural embodiment therefore allows for a clear assignment of
location or assignment of position of the second casing portion 3
with respect to the first casing portion 1. This structural
embodiment is referred to as what is termed an installation
safeguard or as a "mistake proof feature".
LIST OF REFERENCE NUMBERS
[0091] 100 Casing
[0092] a Axial; axial direction
[0093] r Radial; radial direction
[0094] u Circumferential direction
[0095] A Axial section
[0096] 1 First casing portion
[0097] 3 Second casing portion
[0098] 5 Flow-guiding element
[0099] 7 Guide vane
[0100] 9 Rotor blade
[0101] 11 Main throughflow duct
[0102] 13 Further casing portion
[0103] 15 Screw connection
[0104] 17 Sealing segment
[0105] 19 Stripping coating
[0106] 21 Casing intermediate space
[0107] 23 Local flow
[0108] 25 Step
* * * * *