Note: Descriptions are shown in the official language in which they were submitted.
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TURBOMACHINE
SPECIFICATION
FIELD OF THE INVENTION
The present invention relates to a turbomachine. More
particularly this invention concerns a turbomachine two axially
spaced but jointly rotatable impeller wheels.
BACKGROUND OF THE INVENTION
A turbomachine is known having at least one first and
one second impeller wheel whose back faces confront each other, a
rotor shaft carrying both of the radial impeller wheels, and a
bearing system. Adjacent each of the radial-blade impeller
wheels is an axial bearing with one respective rotor bearing half
and one respective stator bearing half. The rotor bearing halves
are each formed on the back face of the respective radial
impeller wheel.
In practice, to contain the axial thrust of a rotor of
a turbomachine using a magnetic bearing system, axial bearing
surfaces are customarily used that are either formed directly on
the shaft, or fixed by an additional axial bearing washer to the
shaft. Correspondingly, turbomachines having an axial
magnetically mounted rotor shaft are known in which the magnetic
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bearing halves for axial bearing are on an axial bearing washer,
or on opposed shaft shoulders shrunk onto the rotor shaft.
EP 2 017 435 A2 describes a design having the features
cited above for a turbomachine having as short a rotor as
possible, and a rotor mass that is as small as possible. Because
the rotor bearing halves are formed on the back faces of the
radial impeller wheels, the space taken up by the axial bearing
can be reduced significantly, the axial bearing halves being
integrated into a housing wall and also integrated into the rear
side of the radial impeller wheels, which must also be present
independent of the bearing. The number of separate components is
thereby reduced. The design known from EP 2 017 435 A2 is
substantially symmetrical starting at an electric machine located
centrally of the rotor between the two radial impeller wheels.
Starting at the electric machine, sequentially in both
directions, a radial magnetic bearing, a safety bearing, an
opening through the assigned stator bearing half having an
interior shaft gasket and finally at the end of the rotor shaft,
the corresponding impeller wheel is mounted overhung. Starting
at the electric machine, the diameter of the rotor shaft
decreases in both directions successively, according to the cited
components that are provided along the rotor shaft. During
assembly, first the rotor shaft must be inserted through with the
electric machine into the housing, the further components and
finally the two impeller wheels are then installed on the two
shaft ends. To make subsequent maintenance possible, the
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turbomachine must be accessible on both sides, and both axial
impeller wheels must be made removable as well.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to
provide an improved turbomachine.
Another object is the provision of such an improved
turbomachine that overcomes the above-given disadvantages, in
particular that is simple to assemble and disassemble as well as
to maintain.
SUMMARY OF THE INVENTION
A turbomachine has according to the invention a shaft
extending along and rotatable relative to a support about an axis
and having an outer surface. A first impeller wheel permanently
mounted on the shaft has a respective back face. The outer
surface of the shaft is formed with steps of increasingly small
diameter away from the first wheel. A second impeller wheel
detachably mounted on a respective one of the steps of the shaft
axially offset from the first impeller wheel has a respective
back face axially confronting the back face of the first impeller
wheel. Respective first and second axial magnetic bearings each
have a respective annular rotor bearing half fixed to the
respective impeller wheel and a respective one-piece nonrotatable
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annular stator bearing half axially juxtaposed with the
respective rotor bearing half, axially spacedly traversed by the
shaft, and carried on the support. A radial bearing mounted on
the rotor shaft between the axial bearings has an inner rotor
ring carried on a respective one of the steps and an outer
stator ring carried on the support.
In accordance with one embodiment of the present invention
there is provided a turbomachine comprising a support; a shaft
extending along and rotatable relative to the support about an
axis and having an outer surface; a first impeller wheel
produced as a separate part and shrunk, welded or pressed onto
the shaft to be permanently mounted on the shaft and having a
respective back face, the outer surface of the shaft being
formed with steps of increasingly small diameter away from the
first wheel; a second impeller wheel detachably mounted on a
respective one of the steps of the shaft axially offset from the
first impeller wheel and having a respective back face axially
confronting the back face of the first impeller wheel;
respective first and second axial magnetic bearings each having
a respective annular rotor bearing half fixed to the respective
impeller wheel and a respective one-piece nonrotatable annular
stator bearing half axially juxtaposed with the respective rotor
bearing half, axially spacedly traversed by the shaft, and
carried on the support, said stator bearing halves each having a
one-piece support having an axial through hole through which the
shaft passes; a radial bearing mounted on the shaft between the
axial bearings and having an inner rotor ring carried on a
respective one of the steps and an outer stator ring carried on
the support.
The first impeller wheel is fixedly mounted together
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with further machine components in a main housing. The shaft
extends out the main housing and the second impeller wheel is
mounted outside the main housing. An electric machine is
provided between the first and second impeller wheels.
According to one embodiment of the invention, an asymmetric
design is provided, and the first impeller wheel is mounted
fixedly and nonremovably on the rotor shaft. Thus according to
the invention the first radial impeller wheel cannot be
separated from the rotor shaft, or can be separated from the
rotor shaft only upon the exertion of a very large force or by
taking special steps. Thus, it is possible, for example, to
shrink the first axial impeller wheel onto the rotor shaft, to
weld it or to press it onto the rotor shaft. Then, during
assembly, starting with the first radial impeller wheel that is
connected nonremovably, the further components, i.e. at least
the stator bearing halves and finally the second radial impeller
wheel are installed sequentially. According to the invention the
individual steps of the shaft outer surface have outer diameters
adapted to the inner diameters of the respective components to
be mounted thereon. The individual components can easily be
pushed up to the section at which they are to be mounted. As a
result of the removable design of the second radial impeller
wheel - depending on the design - disassembly or at least
maintenance of the described components is possible. In
particular, the components of the
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axial bearings are accessible starting from the second radial
impeller wheel.
Because the stator bearing halves are pushed onto the
rotor shaft from one end during assembly, separation into two
half shells or segments is not required, as a result of which
stability and impermeability are improved and production expense
is also reduced.
To form an axial bearing, in particular an actively
controllable axial bearing, magnetic windings of one of the
halves of each bearing generate a magnetic field affecting the
other bearing half, preferably controllable as needed. For
practical reasons it is advantageous when the magnetic windings
are in the fixed stator bearing halves.
To form a magnetic axial bearing, the rotor bearing
halves must consist of a suitable material that magnetically
interacts with the coils, or be covered with permanent magnets.
Often, the material used for impeller wheels is not suited for
forming rotor bearing halves of a magnetic bearing. In such a
case, at least one of the radial impeller wheels can be formed by
an impeller wheel body that includes a blade system and a disk
consisting of a different material, e.g. an aluminum alloy,
fastened at the rear side of the impeller wheel body, the disk
forming the rotor bearing half of the corresponding axial
bearing. Such a disk or such a ring with a central opening for
the rotor shaft can, for example, be welded onto the impeller
wheel body. To make precise welding possible, in particular, a
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connection by friction welding can be provided. Alternatively,
it is also possible to provide a suitable material, for example,
permanent magnets or a magnetizable material in the form of
segments on the rear side of the radial impeller wheels, in
particular to insert them into corresponding recesses.
The assembly and the optionally provided disassembly
from one end permits, within the scope of the invention, that the
first radial impeller wheel with further machine components is
also mounted fixedly in a main housing. Advantageously, it is
then provided that the rotor shaft extends out of the main
housing, as a result of which the second radial impeller wheel is
correspondingly located outside the main housing.
The turbomachine having at least two radial impeller
wheels whose back faces confront each other (back-to-back
arrangement), can serve as a compressor, expander or compander.
While with a compressor having two compressor impeller wheels a
drive, in particular by an electric machine, is to be provided,
in the case of an expander having two impeller wheels, the energy
that is being released can be recovered and used by an electric
machine in the form of a generator. In the case of a compander
having a compressor impeller wheel and an expander impeller
wheel, an electric machine is only optionally provided, and it
can be operated as a generator or as a motor depending on
application.
According to a preferred design of the invention, the
two radial impeller wheels are mounted overhung at respective
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ends of the rotor shaft. But in principle, it is also
conceivable that on at least one of the two radial impeller
wheels, the rotor shaft extends beyond this radial impeller
wheel, and still at least one further device can be mounted on
the rotor shaft, for example, a further radial impeller wheel.
BRIEF DESCRIPTION OF THE DRAWING
The above and other objects, features, and advantages
will become more readily apparent from the following description,
reference being made to the accompanying drawing in which:
FIG. 1 shows components of a turbomachine according to
the invention; and
FIG. 2 shows the system according to FIG. 1 attached to
a main housing.
DETAILED DESCRIPTION
As seen in FIG. 1 a turbomachine according to the
invention has a first impeller wheel 1 and a second impeller
wheel 2 with respective back faces 3a and 3b turned axially
relative to an axis A toward each other in a so-called back-to-
back arrangement. The two wheels 1 and 2 are carried by and
rotationally fixed to a common axially centered rotor shaft 4
mounted on a bearing system that in turn is carried on a fixed
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support constituted by a machine housing.
The bearing system includes respective axial bearings
5a and 5b each having a rotor bearing half 6a or 6b and a stator
bearing half 7a or 7b. The rotor bearing halves 6a and 6b are
formed on back faces 3a and 3b of the respective assigned radial
impeller wheels 1 and 2. The stator halves 7a and 7b are carried
on the fixed support.
According to the invention, the first radial impeller
wheel 1 is permanently mounted on to the rotor shaft 4, for
example by shrinking on, while the second radial impeller wheel 2
can be detached from the shaft 4. Thus, during assembly, the two
stator bearing halves 7a and 7b and then the second radial
impeller wheel 2 can be pushed in sequence onto the rotor shaft 4
to which the wheel 1 has already been fixed. To_make_this
possible, the rotor shaft 4 decreases in cross-sectional size or
diameter from the first radial impeller wheel 1 toward the second
impeller wheel 2. Disassembly of the rotor system is also
possible in reverse order.
FIG. 1 further shows that the stator bearing halves 7a
and 7b each have a respective one-piece support 8 having an
axially centered and throughgoing hole for the rotor shaft 4 and
an electromagnetic winding 9 set in a groove formed in the
respective support 8. In contrast, the rotor halves 6a and 6b on
the back faces 3a and 3b of the radial impeller wheels 1 and 2
consist of a material that interacts magnetically with the
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magnetic windings 9. Thus the rotor bearing halves 6a and 6b are
for example fitted with permanent magnets, magnetizable material
or a material in which an opposing field is induced.
The specific embodiment according to FIG. 1 shows by
way of example a design in which the first radial impeller wheel
1 is comprised of a body 10 formed with axially and radially
extending blades and a flat disk 11 of a different material
integrally fixed to the rear side of the body 10. The disk 11
forms the rotor bearing half 6a of the corresponding axial
bearing 5a and is of a material selected for its magnetic
properties. The rotor half 6a of the annular disk 11 with an
axially centered and throughgoing through hole can, for example,
be permanently connected to the blade body 10 by friction
welding.
FIG. 1 further .shows that the_axially_oppositelv
effective bearings 5a and 5b flank a radial bearing 12 mounted on
the rotor shaft 4 and formed as a magnetic bearing with an inner
rotor ring 13 carried on the shaft 4 and an outer stator ring 14
carried on the fixed support- While the stator ring 14 has
magnetic windings 18, the rotor ring 13 consists of a material
with suitable magnetic properties to form a radial magnetic
bearing together with the magnetic windings 18 of the stator ring
14.
It can be seen that during assembly, first one stator
bearing half 7a1 then the radial bearing 12, then the other
stator bearing half 7b, and finally the second radial impeller
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wheel 2 with the corresponding rotor bearing half 6b mounted on
its back face 3b, are installed, one after the other. To
facilitate assembly, the diameter of the rotor shaft 4 decreases
in steps each intended to carry a respective one of the described
components.
Within the scope of the design according to the
invention, the described configuration is not only to be
assembled successively, but can also in reverse sequence be at
least partially disassembled, so that subsequent maintenance or
the exchange of individual components is still possible.
For example, the first impeller wheel 1 can be fixed
with other machine components in a main housing 15, with the
rotor shaft 4 extending out of the main housing 15 and the second
radial impeller wheel 2 mounted outside the main housing 15. A
corresponding design is shown in FIG. 2. The advantage results_
that during assembly, maintenance, and disassembly of the bearing
system, the main housing 15 can remain closed, while only an
additional housing 16 that covers the bearing system must be
removed.
In principle, the turbomachine can also have an
electric machine that is provided together with the radial
bearing 12 between the radial impeller wheels 1 and 2. This
machine can be a motor, a generator, or a motor/generator.
Furthermore, the radial impeller wheels 1 and 2 can
also be mounted overhung, that is each at a respective end of the
rotor shaft 4. But the invention is not limited to this type of
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design. In principle, it is also possible that the rotor shaft 4
extends beyond at least one of the two radial impeller wheels 1
and 2, for instance into the housing 15.
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