Title: Moving blade for a turbomachine
Abstract: This arrangement relates to a moving blade (1), cast in one piece, for a turbomachine, in particular a turbine or compressor, comprising an aerodynamically shaped profile body (2) which has a shroud band (5). The shroud band (5) projects beyond the profile body (2) in the circumferential direction (6) and has a fin (12). The fin (12) possesses a base portion (14), a transitional portion (15) and a sealing portion (16). An axially measured wall thickness decreases in a transitional portion (15) from the base portion (14) to the sealing portion (16). To avoid a porous structure in the base portion (14), two depressions (17), which reduce the wall thickness of the base portion (14), are integrally molded on the outside of the base portion (14).
Patent Number: 6,962,484 Issued on 11/08/2005 to Brandl, et al.
| Inventors:
|
Brandl; Herbert (Waldshut-Tiengen, DE);
Hoffs; Alexander (West Palm Beach, FL)
|
| Assignee:
|
ALSTOM Technology LTD (Baden, CH)
|
| Appl. No.:
|
407251 |
| Filed:
|
April 7, 2003 |
Foreign Application Priority Data
| Apr 16, 2002[CH] | 2002 0636/02 |
| Current U.S. Class: |
416/192; 416/190; 416/191; 415/173.4; 415/173.5; 415/173.6 |
| Intern'l Class: |
F01D 005/20 |
| Field of Search: |
416/189,190,191,192
415/173.1,173.4,173.5,173.6,228
|
References Cited [Referenced By]
U.S. Patent Documents
| 3867060 | Feb., 1975 | Huber.
| |
| 4643645 | Feb., 1987 | Robbins et al.
| |
| 6068443 | May., 2000 | Aoki et al.
| |
| 6241471 | Jun., 2001 | Herron.
| |
| Foreign Patent Documents |
| 11-350902 | Dec., 1999 | JP.
| |
| 2001/-193405 | Jul., 2001 | JP.
| |
Other References
EPO Search Report, dated May 8, 2003.
Patent Abstracts Of Japan, vol. 2000, No. 03, Mar. 30, 2000, -& JP 11 350902
A (Ishikawajima Harima Heavy Ind Co Ltd), Dec. 21, 1999, Zusammenfassung Abbildungen
1A, 1B (5 pp).
Patent Abstracts Of Japan, vol. 1000, No. 24, May 11, 2001, -& JP 2001 193405
A (Mitsubishi Heavy Ind Ltd), Jul. 17, 2001 Zusammenfassung (6 pp).
Seach Report, prepared by the European Patent Office, for Swiss Appl. No. CH
6362002, issued on Jul. 18, 2001.
|
Primary Examiner: Verdier; Christopher
Attorney, Agent or Firm: Cermak & Kenealy LLP, Cermak; Adam J.
Claims
1. A moving blade, cast in one piece, for a turbomachine, comprising:
an aerodynamically shaped profile body having a radially outer end including
an integrally molded shroud band which projects beyond the profile body in the
circumferential direction and which has radially on the outside an integrally molded
fin which extends in a circumferential direction along the shroud band and which,
at least in a region of the shroud band in which the profile body runs, has a base
portion connected to the shroud band, a transitional portion adjoining the base
portion radially, circumferentially, or both, and a sealing portion adjoining the
transitional portion radially, circumferentially, or both;
an axially measured wall thickness decreasing in the transitional portion from
the base portion to the sealing portion; and
at least one depression which reduces the wall thickness of the base portion
integrally molded on the outside of the base portion.
2. The moving blade as claimed in claim 1, further comprising at least two depressions
arranged opposite one another with respect to a plane extending circumferentially
and radially.
3. The moving blade as claimed in claim 2, further comprising a wall portion
between the depressions located opposite one another in alignment with the sealing
portion of the fin.
4. The moving blade as claimed in claim 2, further comprising a wall portion
between the depressions located opposite one another having the same wall thickness
as the sealing portion of the fin.
5. The moving blade as claimed in claims
1, wherein the wall thickness
of the base portion corresponds to the wall thickness of the sealing portion in
the region of the at least one depression.
6. The moving blade as claimed in claims
1, wherein the at least one depression
has a planar bottom which extends parallel to the sealing portion.
7. The moving blade as claimed in claims
1, wherein the at least one depression
is frustoconical.
8. The moving blade as claimed in claims
1, wherein the depression has
an opening cross section which widens outward in the axial direction and which
runs parallel to a plane of the fin, said plane extending in the circumferential
direction and in the radial direction.
9. A turbine comprising a moving blade as claimed in claim 1.
10. A compressor comprising a moving blade as claimed in claim 1.
Description
This application claims priority under 35 U.S.C. § 119 to Swiss application
number 2002 0636/02, filed Apr. 16, 2002.
TECHNICAL FIELD
The invention relates to a moving blade, cast in one piece, for a turbomachine,
in particular for a turbine or for a compressor.
PRIOR ART
A moving blade of this type normally possesses an aerodynamically shaped profile
body which, at its radially outer end, has an integrally molded shroud band which
projects beyond the profile body in the circumferential direction. In the present
patent application, the designations "radially", "axial" and "circumferential direction"
refer to the installation state of the moving blade, the axis of rotation of a
rotor, to which the moving blade is fastened, running axially in this sense and
thus defining the coordinate system of the moving blade.
The shroud band formed at the moving blade tip, on the one hand, has a flow guide
function, in that it prevents an undesirable flow around the profile body tips.
On the other hand, the shroud band possesses a stabilizing function, since the
dimensioning of the shroud band is such that, during operation, shroud bands of
moving blades adjacent to one another in the circumferential direction are supported
mutually one on the other and thereby reduce oscillations and vibrations of the
moving blades.
So that, when the moving blade is in operation, the shroud band does not flex
in an undesirable way in its portions projecting in the circumferential direction,
the shroud band has integrally molded on it, radially on the outside, a reinforcing
fin which extends in the circumferential direction along the shroud band and supports
the latter. In the region of the fin, the shroud band is thereby designed virtually
as a T-beam.
The fin additionally has a sealing function, since it obstructs an axial flow
around the shroud band radially on the outside, particularly when, in the installation
state, the fin engages into a complementary sealing contour, in order, for example,
to form a labyrinth seal.
Since relatively high centrifugal forces occur when the moving blade is in
operation, an attempt is made to design the shroud band and the fin to be as light
as possible, that is to say with relatively small wall thicknesses. Such a fin
may accordingly be composed of a plurality of portions. In particular, the fin
has, at least in a region of the shroud band in which the profile body runs, a
base portion connected to the shroud band, a transitional portion adjoining the
base portion radially and/or in the circumferential direction and a sealing portion
adjoining the transitional portion radially and/or in the circumferential direction.
So that sufficient strength and dimensional stability can be ensured for the fin
and the shroud band, an axially measured wall thickness in the base portion is
markedly larger than in the sealing portion. Correspondingly, the wall thickness
decreases in the transitional portion from the base portion to the sealing portion.
During the casting of the moving blade, the fin is molded by feeding, that
is to say the liquid alloy is not introduced into the casting mold at the fin,
but at another suitable point, so that the molding region forming the fin is fed
or supplied with liquid alloy from the adjoining regions of the mold. Since the
alloy shrinks during solidification, it must be possible, during the solidification
process, for liquid alloy to continue to flow, in order to avoid casting faults,
for example porous structure or pores. Problems arise in this case, in the region
of the base portion of the fin, since the base portion has a relatively large volume
due to its larger wall thickness. The result of this is that the base portion,
on the one hand cools relatively slowly and, on the other hand, during cooling,
requires a relatively large amount of liquid alloy in order to avoid dimensional
changes. Since, however, the portions of the moving blade which are contiguous
to the fin, that is to say the shroud band and, indirectly, the profile body, usually
have smaller wall thicknesses than the base portion, these thinner wall portions
may, usually, solidify before the base portion of the fin, with the result that
a further feed of material into the solidifying base portion is obstructed. Correspondingly,
during the production of a moving blade of this type, casting faults occur relatively
frequently in the region of the base portion of the fin. In order to take this
into account, the feeding portions must be dimensioned correspondingly larger,
thus increasing the mass of the blade tip, with the result that the moving blade
is exposed to higher loads during operation.
PRESENTATION OF THE INVENTION
The invention is intended to remedy this. The invention, as characterized in
the claims, is concerned with the problem of specifying, for a moving blade of
the type initially mentioned, an improved embodiment which, in particular, reduces
the occurrence of casting faults during production.
This problem is solved, according to the invention, by means of the subject
of the independent claim.
Advantageous embodiments are the subject matter of the dependent claims.
The invention is based on the general idea of reducing the wall thickness in
the base portion of the fin at at least one selected point. This is achieved, according
to the invention, by means of at least one depression which is integrally molded
on the outside of the base portion as early as during the casting of the moving
blade. The proposed form of construction reduces the volume of the base portion,
with the result that the latter, on the one hand, during casting, can solidify
more quickly and, on the other hand, during solidification, requires a lower afterfeed
of liquid alloy in order to maintain the desired shape.
By an optimization of the shape and position and, if appropriate, of the number
of depressions of this type, the fin can ensure its carrying function sufficiently
reliably, while having a reduced mass and/or regions of reduced wall thickness.
Correspondingly, the risk of casting faults in the region of the
base portion of the fin is reduced.
In a development, at least two depressions may be provided, which are arranged
opposite one another with respect to a plane extending in the circumferential direction
and radially. The reduction in wall thickness thereby takes place essentially symmetrically,
this being advantageous for the production capability of the blade and for the
strength of the fin.
According to a development, a wall portion remaining between the depressions
located opposite one another may have essentially the same wall thickness as the
sealing portion of the fin. Solidification thereby takes place essentially synchronously
in the sealing region and in this wall portion, thus simplifying the production
of the blade.
Further important features and advantages of the invention may be gathered
from the subclaims, from the drawings and from the accompanying figure description
with reference to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred exemplary embodiment of the invention is illustrated in the drawings
and is explained in more detail in the following description, identical reference
symbols relating to identical or functionally identical or similar components.
In the drawings, in each case diagrammatically,
FIG. 1 shows an axial section through a moving blade according to the invention
in the region of a fin along the sectional lines I in FIG. 2,
FIG. 2 shows a section through the fin in the circumferential direction along
the sectional lines II in FIG. 1.
EMBODIMENTS OF THE INVENTION
According to FIGS. 1 and 2, a moving blade
1 according to the invention
of a turbomachine, in particular a turbine or a compressor, possesses a profile
body
2 which is shaped aerodynamically and, during operation, has a flow
passing around it. In FIG. 2, a tip profile formed at the tip of the profile body
2 is illustrated by a broken line and is designated by
3. A foot
profile present on the radially inner foot of the profile body is designated by
4. As may be gathered from the run of the profile along the profile body
2, the latter is twisted. The radial direction is in this case symbolized
in FIG. 1 by an arrow
7.
The profile body
2 has integrally molded on it, at its radially outer
end, a shroud band
5 which, on the one hand, completely covers the tip profile
3 and, on the other hand, projects beyond the profile body
2 in the
circumferential direction approximately centrally with respect to the profile body
2. The circumferential direction is in this case symbolized in FIG. 2 by
an arrow
6. To complete the reference system, FIGS. 1 and 2 additionally
illustrate the axial direction by means of an arrow
8.
The projecting regions of the shroud band
5 are designed in FIG. 2 by
9 and
10 and serve for flow guidance when the moving blade
1
is in operation, in that they obstruct an undesirable flow around the tip of the
profile body
2. Furthermore, these regions
9,
10 of the shroud
band
5 are dimensioned such that, when the moving blade is in operation,
they cooperate with matching regions
9,
10 of adjacent moving blades
1 in order to stabilize the moving blades
1. At the latest when the
moving blades
1 are in operation, that is to say with turbine rotor or compressor
rotor rotating, the shroud bands
5 of adjacent moving blades
1 come
to bear on one another at the regions
9,
10 projecting in the circumferential
direction, for which purpose corresponding bearing surfaces
11 are formed
at the regions
9,
10. As a result, on the one hand, an additional
twisting of the profile body
2 during operation is limited. On the other
hand, the mutual support damps the formation of oscillations or increases the frequency
of the latter.
So that, during operation, the shroud band
5 is not inadmissibly deformed
in its projecting regions
9,
10, a fin
12 is integrally molded
on the shroud band
5 radially on the outside. This fin
12 extends
in the circumferential direction
6 along the shroud band
5, centrally
with respect to the profile body
2, over the entire extent of the shroud
band
5, that is to say even in the projecting regions
9,
10.
Thus, a T-beam profile, which can be seen in FIG. 1, is formed on the shroud band
5 in the region of the fin
12. The fin
12 thus provides an
intensive stiffening of the projecting regions
9,
10, with the result
that the shroud band
5 acquires sufficient stability. In a region
13
which is identified in FIG. 2 by a brace and in which the profile body
2
adjoins the shroud band
5, the fin
12 possesses a base portion
14
which merges into the shroud band
5. A transitional portion
15 adjoins
this base portion
14 in the radial direction
7 according to FIG.
1 and in the circumferential direction
6 according to FIG. 2. A sealing
portion
16 adjoins this transitional portion
15 in the radial direction
7 again according to FIG.
1 and in the circumferential direction
6 according to FIG.
2. With the aid of this sealing portion
16,
the fin
12 performs its sealing function, in that it obstructs a flow around
the shroud band
5 in the axial direction on its radially outer side.
As may be gathered from FIGS. 1 and 2, a wall thickness, measured in the axial
direction
8, of the fin
12 decreases in the transitional portion
15 from the base portion
14 to the sealing portion
16. By
virtue of this form of construction, the fin
12 possesses increased strength
in the region of the transitional portion
15 and of the base portion
14,
so that the necessary rigidity of the shroud band
5 can be ensured.
According to the invention, then, at least one depression
17, which
locally reduces the wall thickness of the base portion
14, is integrally
molded on the outside of the base portion
14. In the preferred embodiment
shown here, two depressions
17 of this type are formed. The two depressions
17 are in this case arranged opposite one another with respect to a plane,
not designated in any more detail, of the fin
12, said plane extending in
the circumferential direction
6 and in the radial direction
7. The
depressions
17 are in each case formed in such a way that they have an opening
cross section which lies parallel to the plane of the fin
12 and which is
indicated in the figures by an arrow
20 and widens outward in the axial
direction
8 with respect to the fin
12. In particular, the depressions
17 may be of frustoconical design. This geometric shaping of the depressions
17 serves for optimizing the stress distribution in the fin
12 during
operation and makes it easier to remove the model from the mold.
Each of the depressions
17 possesses a planar bottom
18. These
bottoms
18 limit a wall portion
19 which remains as a result of the
integral molding of the depressions
17 and which has a smaller wall thickness
than the remaining region of the base portion
14 or than the transitional
region
15. Expediently, the bottoms
18 of the depressions
17
run essentially parallel to the sealing portion
16 of the fin
12,
that is to say essentially parallel to the radial direction
7 and parallel
to the circumferential direction
6. In the embodiment shown here, the wall
thickness of the base portion
14 is reduced in the region of the depressions
17, that is to say in the wall portion
19, to an extent such that
it corresponds essentially to the wall thickness of the sealing portion
16.
The same wall thicknesses are identified in FIGS. 1 and 2 by dimensioning arrows
and are designated by D.
Expediently, the two depressions
17 are designed symmetrically
to an extent such that the wall portion
19 remaining between the depressions
17 is in alignment with the sealing portion
16 of the fin
12
in the radial direction
7 according to FIG.
1 and in the circumferential
direction
6 according to FIG.
2. This measure, too, leads to optimization
with regard to the stress distribution in the fin
12 and the load-bearing
capacity of the latter.
It is particularly important, in this case, that the moving blade
1, including
the depressions
17, be designed or produced as a one-part or one-piece cast
component. What is achieved by allowing for one or more depressions
17 of
this type in the casting mold used for producing the moving blade
1 is that
the base portion
14, which per se has a large mass, is reduced in terms
of its volume to be cast. The result of this is that, on the one hand, during the
casting of the moving blade
1, the fin
12 can cool more quickly in
the base portion
14 and, on the other hand, during the solidification process,
less melt which continues to flow is required in order to avoid shrinkage. Correspondingly,
in the moving blade
1 configured according to the invention, the formation
of porous structures can be reduced or avoided. The strength and useful like of
the moving blade
1 are thus increased. Furthermore, by virtue of this measure,
the weight of the fin
12 can be reduced, in order thereby to reduce the
load on the moving blade
1 during operation.
The positioning and geometric shaping and also the number of the depressions
17 are expediently selected such that an optimum is obtained for the stiffening
function and the sealing function of the fin
12, on the one hand, and for
the production capability and service life of the moving blade
1, on the
other hand.
LIST OF REFERENCE SYMBOLS
1 Moving blade
2 Profile body
3 Tip profile of 2
4 Foot profile of 2
5 Shroud band
6 Circumferential direction
7 Radial direction
8 Axial direction
9 Projecting region of 5
10 Projecting region of 5
11 Contact surface
12 Fin
13 Region of 12
14 Base portion of 12
15 Transitional portion of 12
16 Sealing portion of 12
17 Depression in 14
18 Bottom of 17
19 Wall portion
*
