Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Method for Producing Integrally Blade-Mounted Rotors
Specification
The present invention relates to a process for producing integrally bladed
rotors, especially
rotors of a gas turbine by an electrochemical process. The invention
furthermore relates to
an integrally bladed rotor produced with the named process.
Slender three-dimensional geometries of metallic structural components such
as, for
example, blisk blades are worked out of a solid material as a rule, at which
time the so-
called pre-allocation of the individual blades, i.e. the production of blade
pre-profiles takes
place by milling processes. In addition, the production of blade pre-profiles
by water-jet
cutting or eroding is known. In addition, it is possible to pre-allocate the
intermediate
blade space in the case of blisk blades by a straight or curved slot by
electrochemical
removal processes such as the so-called ECM (Electro Chemical Machining) or by
grinding. In the cited ECM process the surface of the workpiece is worked as a
rule with
an electrode, during which a removal of material on the workpiece takes place
by
electrochemical reaction of the workpiece with the electrolyte located between
the
workpiece and the electrode. The electrode is connected as cathode to a direct
current
source. The electrode then moves at a given speed toward the structural
component poled
as anode. The width of the working slot between the electrode and the
structural
component is of considerable significance. In customary ECM processes the work
is
carried out with intervals from the element to the workpiece that can be in a
range of 1
to 2 mm. In order to produce finer structures and forms the interval can be
reduced to
magnitudes in a=range of 10 to 50 m and above. However, the successful use of
a poled
ECM process (PECM) requires in many areas of use a uniform overmeasure of the
blade
and/or blade pre-profile to be worked. Thus, for example, an electrochemically
produced
pre-contour of a blade pan of a gas turbine, in particular of a blisk blade,
previously had an
overmeasure between ca. 1 and ca. 3 mm, conditioned by the process. In order
to produce a
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necessary uniform overmeasure in these instances the non-uniform overmeasure
was
previously worked by milling. However, such processes can be used only in a
very limited
manner, in particular in the working of slender structural components such as,
e.g., blade
pans, since there is a danger of damage here such as, for example, a
deformation of the
structural parts. In addition, such a procedure for the production of blade
pre-profiles is
relatively time-consuming and therewith cost-intensive due to the plurality of
process
steps.
The present invention therefore has the problem of making available a generic
process for
the production of integrally bladed rotors, in particular rotors of a gas
turbine, which
ensures a relatively rapid and precise production of raw blades with
approximately the
same overmeasure.
The present invention furthermore has the problem of making available an
integrally
bladed rotor of the initially cited type that can be produced relatively
rapidly and precisely.
These problems are solved by a process in accordance with the features of
Claim 1 as well
as by an integrally bladed rotor in accordance with the features of Claim 10.
Advantageous embodiments of the invention are described in the particular
subclaims.
A process in accordance with the invention for producing integrally bladed
rotors, in
particular rotors of a gas turbine comprises the following steps:
a) The defining of and making available a blade profile of a blade to be
manufactured
with a pre-contour and theoretical contour;
b) The production of at least two sectional planes of the blade profile, which
sectional
planes run vertically to a threading axis of the blade profile and of the
blade to be
produced;
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c) The determining of a point of rotation per sectional plane in such a manner
that the
interval between the pre-contour and the theoretical contour is approximately
the same
circumferentially, which points of rotation are located on a connecting line
running
parallel to the threading axis;
d) Making available a base rotor body and the electrochemical working of the
base rotor
body in order to produce a raw blade with a blade pre-contour by a lowering of
a
hollow electrode into the base rotor body, during which an advance movement of
the
hollow electrode, that is superposed by rotation, takes place along the
connection line
determined in process step c), and during which the hollow electrode has an
inner
contour adapted to the pre-contour of the raw blade at least in an end area
that is
lowered onto the base rotor body.
The process in accordance with the invention ensures the production of blade
pre-profiles
for integrally bladed rotors with a uniform circumferential overmeasure in all
cross
sections by a simple lowering movement with a hollow electrode which movement
compensates the blade twist by a rotation, which hollow electrode encloses the
overmeasure blade in the interior. In addition, it is possible that a pre-
allocation of
intermediate spaces between two adjacent raw blades takes place at the same
time in
process step d). The process in accordance with the invention ensures that the
overmeasure
contour results in each step in an almost uniform overmeasure on the convex
side and
concave side of the blade although the lateral has a three-dimensional swung
form.
Furthermore, the process in accordance with the invention ensures the use of a
simple
electrode contour for lowering the intermediate spaces of the blade in the
case of integrally
bladed rotors.
In an advantageous embodiment of the process in accordance with the invention
a plurality
of hollow electrodes is moved simultaneously or successively into the base
rotor body.
Prior to a lowering of the plurality of hollow electrodes a determination of
the connecting
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line for the determining of the advance movement of each hollow electrode can
take place.
This ensures that each raw blade produced has an optimized overmeasure.
In a further advantageous embodiment of the process in accordance with the
invention the
points of rotation are arranged off-center relative to the blade profile. In
addition, the
points of rotation are located off-center relative to the contour of the
hollow electrode.
This process has proven to be especially advantageous for the rapid and
precise
production of raw blades.
In a further advantageous embodiment of the process of the invention the
hollow electrode
is constructed in an electrically insulating manner up to an end area that is
lowered onto
the base rotor body. This ensures that no undesired removal events occur on
the raw
blade by the inner contour of the electrode.
In further advantageous embodiments of the process of the invention, after the
production
of the raw blades according to the process steps a) to d) an electrochemical
working of
the raw blades takes place for making available fluidic surfaces in accordance
with the
theoretical contour of the blades to be produced. The electrochemical working
can take
place here by a precise electrochemical removal process (PECM). For the rest,
it is also
conceivable that the production of the raw blades takes place by a PECM
process. Even
in the precise electrochemical removal the inner- and/or outer contour of at
least one
electrode used to this end can be adapted to the theoretical contour of the
blades. In
addition, the precision of the removal procedure can be raised during the
precise
electrochemical removal by an oscillating of the electrode during lowering.
The cited
measures make it possible to efficiently produce integrally bladed rotors such
as blisks
and blings.
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A gas turbine rotor integrally bladed in accordance with the invention is
produced
according to a process described above. The rotor integrally bladed in
accordance with the
invention can be rapidly and precisely produced.
An exemplary embodiment of the process in accordance with the invention is
described in
detail in the following with reference made to the figures.
Fig. 1 shows a schematic lateral view of several raw blades of an integrally
bladed
rotor which blades are produced with the process in accordance with the
invention; and
Fig. 2 shows a schematic top view onto the integrally bladed rotor according
to
figure 1.
Fig. 1 shows a schematic lateral view of several raw blades 12 produced with
the process
for the production of integrally bladed rotors 10. In the exemplary embodiment
shown the
rotor is a so-called blisk. The raw blades 12 as well as the rotor disk 18
connected to them
are worked out of a base disk body. Raw blades 12 have a blade pre-contour
with a
uniform overmeasure so that they can be readily further processed. The further
processing
takes place, for example, by a PECM process with which fluidic surfaces can be
produced
according to the theoretical contour of the final blades to be produced.
Figure 2 shows a schematic top view onto integrally bladed rotor 10 according
to fig. 1.
Here, two points of rotation 14, 16 are sketched in by way of example. Points
of rotation
14, 16 each correspond to a sectional plane through the blade profile, namely,
vertically to
a threading axis of the blade profile. Points of rotation 14, 16 are
determined in such a
manner per sectional plane that the interval between a pre-contour and a
theoretical
contour of the blades to be produced is circumferentially approximately the
same, and the
points of rotation 14, 16 are located on a connecting line running parallel to
the threading
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axis. The advance movement of a hollow electrode (not shown), that is
additionally
superposed by a rotation about the particular points of rotation 14, 16, takes
place along
the determined connecting line. The hollow electrode is constructed in such a
manner here
at least in an end area that is lowered onto the base rotor body that this
hollow electrode
has an inner contour that is adapted to the pre-contour of the raw blade.
Furthermore, it
can be recognized that points of rotation 14, 16 are arranged off-center
relative to the
blade profile of the raw blades. In addition, it is clear that a pre-
allocation of the
intermediate spaces 20 between adjacent raw blades 12 takes place by the
lowering of the
hollow electrode in the direction of the base rotor body. The integrally
bladed rotor 10
produced can consist of alloys based on nickel, cobalt or titanium.
