Note: Descriptions are shown in the official language in which they were submitted.
CA 02925413 2016-03-24
WO 2015/049295
PCT/EP2014/071057
TURBO ENGINE WITH TORSIONAL COUPLING INTEGRATED TO AT LEAST
ONE DRIVING OR DRIVEN SHAFT DRIVING
The invention relates to turbo engines, for example integrated motor-driven
compressors. However, of course one does not go outside the framework of the
present
invention merely because it relates to another type of turbo engine, namely a
turbo
alternator.
An integrated motor-driven compressor group comprises a leakproof housing
which
contains an engine, for example an electric motor, and a compressor group, for
example a multi-stage unit, which comprises one or several wheels with blades
for
compression carried by a driven driven shaft and actuated by a driving driving
shaft
consisting of the rotor of the motor or actuated by the latter.
One coupling solution for the driving shaft and the driven shaft consists in a
coupling
of the driven shaft and the driving shaft by means of a rigid coupling, with
bearings
provided for supporting the ends of the line of shafts of the motor-driven
compressor
group, as well as its median portion.
This solution poses in a certain number of cases manufacturing problems and
problems related to the dynamic of the rotor.
Therefore, it is proposed to couple the driving shaft and the driven shaft by
means of a
flexible coupling in order to avoid the problems related to the alignment. In
this
respect, one can refer to the document WO 2004/083644 which describes such a
layout.
The currently used flexible couplings, which are generally of the type with a
membrane, increase the axial dimension of the motor-driven compressor group,
typically of the order of 35 to 40 cm, compared to a rigid coupling with a
flange. In
addition, they present a fragility zone because they can be subjected, for
example, only
to tensile or compression forces that are limited in the axial direction.
However, during the functioning of the layout described by the document WO
2004/083644, the gas feeding the compressor is extracted in full or in part
after the
1
CA 02925413 2016-03-24
WO 2015/049295
PCT/EP2014/071057
compression stage and is used for cooling the motor. The flow of the cooling
gas in the
motor takes place in the direction of the compressor.
The motor-driven compressor has a single abutment on the rotor of the
compressor, on
the opposite side of the coupling. Due to this fact, an axial thrust is
generated in the
motor and is absorbed by the coupling prior to being taken over by the axial
abutment.
Therefore, in order to alleviate these inconveniences, it has been proposed to
use a
torsional coupling placed in a hollow shaft of the compressor. Such a layout
is
described in the document FR 2 969 722. Although it is effective in
alleviating the
inconveniences related to the use of a flexible coupling between the driving
shaft and
the driven shaft, such a layout complicates the structure of the shaft
assembly.
In view of the preceding discussion, the aim of the invention is to mitigate
the
inconveniences related to the layouts according to the state of the art and,
in particular,
to enable the axial efforts generated during the functioning of the levels of
compression to be supported and this in a simple layout.
Therefore, the object of the invention is a turbo engine comprising a driving
shaft and
a driven shaft actuated by the driving shaft being coupled driven to this
driving shaft
by means of a torsional coupling.
In addition, the torsional coupling is integrated at least into one of the
driven and
driving shafts which comprise a flexible zone in torsion so as to form the
said torsional
coupling.
This can be, for example, a motor-driven compressor group comprising a motor
driving a compressor, comprising a set of wheels with blades for compression
mounted on the driven shaft.
The set is mounted in a common housing which is impermeable to the gas
generated
by the motor-driven compressor group.
Because the torsional coupling is integrated in the driving and/or the driven
shaft, the
problems, namely in terms of design and manufacturing, in the assembly, which
exist
2
CA 02925413 2016-03-24
WO 2015/049295
PCT/EP2014/071057
in the case of a torsional coupling assembled to a driving or driven shaft,
such as
described in the above-quoted document FR 2 969 722, are resolved.
The shaft, in which the torsional coupling is integrated, comprises, in
addition,
preferably, an external peripheral zone which constitutes a means for
supporting the
functions performed by the rotor.
This torsional zone, existing at least in one of the driving and driven
shafts, is formed,
for example, by a cylindric part with a diameter that is smaller that the
remaining part
of the shaft in which the torsional coupling is integrated.
It has, advantageously, a length selected in relation to the diameter in a way
to confer
to the coupling a torsional capability. Thanks to the presence of this
reduction of the
diameter, the shaft assembly comprises an internal shaft with reduced
dimensions,
through which the driving and driven shafts are coupled, permitting a
localized
deformation of the shaft assembly by the torsion.
In other embodiments, the torsional cylindrical part can be mounted either in
the
driven shaft or in the driving shaft, or in the two shafts ¨ both driving and
driven.
The torsional cylindrical part can be entirely in projection starting from the
shaft, into
which the coupling is integrated, or can be partially or totally situated in
the interior of
a hollow part, in the form of a hollow shaft, enabling the hollow shaft to
support one
or several functions carried out by the rotor. When the torsional cylindrical
part is
located inside the hollow shaft, it is thus in cantilever around the torsional
part. This
solution can be realized eventually by means of a throat r or by reducing the
diameter
and of the assembly.
The realization of the torsional part partially or completely inside a hollow
part
enables the length of the shaft assembly to be limited and thereby the
dimensions, the
weight and the cost of the turbo engine.
This can have also a beneficial effect on the dynamics of the rotor.
3
CA 02925413 2016-03-24
WO 2015/049295
PCT/EP2014/071057
It has to be noted that the cylindrical part(s) can be obtained by using
various
techniques.
One embodiment, comprises an axial cylindrical throat, which delimits in the
said
shaft another internal shaft coupdriven to the other driving or driven shaft
and one
external shaft. For example, the axial cylindrical throat is formed by means
of
electroerosion.
Alternatively, this torsional coupling is obtained by providing at the
manufacturing
stage a reduction of the diameter (for example by means of forging and by
machining)
in the driven and/or driving shaft.
In this case, at least one of the driven and driving shafts comprises in its
torsional
coupling zone one axial cylindrical throat delimited by an internal shaft and
one
external shaft assembled around the internal shaft.
In one embodiment mode, the external shaft is extending till the connection
zone of
the driving and driven shafts.
According to another embodiment, the free end of the shaft, into which the
torsional
coupling is integrated at a diameter that is greater than the diameter of its
median part,
forms a coupling zone of the said internal shaft with the other driving or
driven shaft.
Alternatively, it is also possible to ensure that that the free end of the
shaft, to which
the torsional coupling is integrated, has a diameter that is less than those
of the
coupling zone corresponding to the other driving or driven shaft, with which
it is
coupled, forming a flange that ensures the coupling of the said driving or
driven shafts.
Other objectives, characteristics and advantages of the invention will become
apparent
from a reading of the following description, which is provided solely as an
example
without limitations and refers to the attached drawings in which:
- Figure 1 is a synoptic diagram illustrating the general structure of a
motor-driven
compressor group according to the invention;
4
CA 02925413 2016-03-24
WO 2015/049295
PCT/EP2014/071057
- Figure 2 illustrates a first embodiment of the motor-driven compressor
group
according to figure 1;
- Figure 3 illustrates another embodiment of a motor-driven compressor
group
according to the invention;
- Figure 4 illustrates another example of the realization of compressor
group
according to the invention; and
- Figure 5 illustrates another implementation mode of the torsional zone.
Referring first to figure 1, a motor-driven compressor according to the
present
invention, designated by the general reference G, comprises essentially a
motor 1, for
example an electric motor with high rotational speed, for example between
6,000 and
16,000 revolutions/minute, powered by a frequency converter and comprising a
stator
2 and a rotor 3 forming a driving shaft for the motor-driven compressor group,
and a
compressor group 4 comprising a set of wheels with blades 5, 6 and 7, here
three in
number, mounted on the driven shaft 8. As it can be seen, the driven shaft 8
is
supported by the radial bearings 9.
The arrangement is mounted on a base (not shown) and is located in a common
casing
10, which is impermeable to the gas generated by the motor-driven compressor
group.
The casing 10 comprises an input "INPUT", through which the gas to be
generated is
drawn by suction into the compressor and an output "OUTPUT", through which the
compressed gas is delivered when it exits from the compressor group 4.
In the embodiment shown, the compressor group 4 comprises three wheels with
blades
mounted on the driven shaft 8. Obviously, the compressor group 4 can comprise
any
number of such wheels with blades or comprise a different layout of wheels
with
blades.
In the embodiment illustrated in figures 1 and 2, the driven shaft 8 is
equipped, at the
level of its end zone, with a shoulder E, with which this shaft is bolted on
the one end
with respect to the driving shaft 3 of the motor 1.
5
CA 02925413 2016-03-24
WO 2015/049295
PCT/EP2014/071057
In any case, the coupling between the driven shaft and the driving shaft
consists of a
torsional coupling.
This torsional coupling is obtained by the implementation in at least one of
the driven
and driving shafts of a torsional zone, i.e. flexible in the rotation.
In the embodiment shown in figures 1 to 4, this torsional coupling is obtained
by
machining an axial cylindrical throat 11 in the driven shaft 8, in order to
form in the
driven shaft 8 an internal shaft 12, through which the driven shaft 8 is
coupled to the
driving shaft 3, and an external shaft 13, through which the driven shaft 8 is
guided by
the radial bearing 9. The length of the throat will be selected in relation to
the diameter
of the shaft, in which it is mounted, with a length chosen in such a way as to
confer to
the coupling a torsional character.
In this way, by mounting the cylindrical throat in the driven shaft 8, the
useful
diameter of the shaft 8, which transmits the actuation efforts is locally
reduced, and its
resistance to torsional and radial deformations can be reduced, while
retaining an
important radial rigidity. The driven shaft and in particular the internal
shaft 12 remain
notably capable of withstanding the axial force created during the operation
of the
wheels with compression blades 5, 6 and 7.
The presence of the torsional part enables because of the localized reduction
of the
useful section of the shaft assembly, the driven shaft 8 to be endowed with
the
characteristic that it can be deformed by bending and by elastic torsion so
that on the
one hand, defects in the angular alignment, on the one hand, and on the other
lateral
defects, on the other, between the driven shaft and the driving shaft can be
compensated, either during the installation of the motor-driven compressor or
while it
is in operation.
This flexibility also enables the flexural vibrations between the driving
shaft and the
driven shaft to be filtered.
6
CA 02925413 2016-03-24
WO 2015/049295
PCT/EP2014/071057
Furthermore, the torsional zone enables a gradation to be achieved of the
efforts
transmitted during the rapid changes of the torque transmitted by the motor or
the
resistive torque produced by the compressor.
In addition, the mounting is largely simplified since the shaft assembly is
constituted
simply by two portions of the shafts, namely the driving shaft and the driven
shaft.
It is to be noted that in the embodiment illustrated in figures 1 and 2, the
torsional part
is mounted in the driven shaft 8. In addition, the driven shaft 8 comprises an
external
shaft 13, whose end is behind in relation t to the free end of the internal
shaft 12, with
which this shaft 12 was fixed to the driving shaft 3. In other terms, in this
embodiment,
the internal shaft 12 has a diameter that is smaller than the diameter of the
end formed
by the shoulder E.
In addition, the torsional coupling is obtained, as can be seen in figures 1
and 2, by
obtaining, at the manufacturing stage, for example by means of forging and by
machining of the driven shaft 8, a localized reduction of the diameter in
order to form
the end zone 12 of the driven shaft of reduced diameter, the cylindrical
throat being
then realized in order to form the external shaft 13.
The torsional coupling obtained in the embodiment shown in figures 1 and 2, by
arranging a throat in the driving shaft can of course be formed by arranging
this throat
in the driving shaft or in the two shafts ¨ driving and driven.
In another embodiment, which can be seen in 3, the external shaft 13 extends
over a
substantial part of the internal shaft 12, which here does not have an end
shoulder.
Therefore, the mounting of the internal shaft 12 on the end of the driving
shaft 3
employs a flange 14 fixed by being bolted onto the free end of the driving
shaft 3 and
connected in rotation to the internal shaft 12. Axial throat could be
provided, for
example, in the internal peripheral surface of the flange 14, destined to
engage with the
corresponding ribs mounted at the free end of the internal shaft 12.
In this respect, a flange with a general conical form or endowed with an end
shoulder
as can be seen in figure 3 can be used.
7
CA 02925413 2016-03-24
WO 2015/049295
PCT/EP2014/071057
This embodiment is advantageous insofar as it enables the distance between the
ends
of the shafts to be reduced, i.e. the distance between the free end of the
external shaft
13 and the free end with respect to the driving shaft 3, this distance being
fixed by the
length of the flange 14.
According to a third embodiment, shown in figure 4, the driving shaft 3 and
the driven
shaft 4 both have an axial cylindrical throat 11 and 11 a. The throat 11 is
similar to the
throat used in the embodiment in figure 3.
As in the embodiments described above, as regards the driven shaft, the axial
cylindrical throat 11 creates an internal shaft 12 and an external shaft 13
which are
extended along a substantial part of the internal shaft 12, with this internal
shaft 12
extending in a projection starting from the external shaft 13 along a length
that is
sufficient for the mounting of a flange 15.
As regards the driving shaft 3, the axial cylindrical throat lla creates in
this shaft 3, an
internal shaft 16 and an external shaft 17 which are extended along a
substantial part
of the internal shaft 16, with the latter extending in a projection beyond the
free end of
the external shaft 17 along a length that is sufficient for the mounting of
the flange 15.
Thus, in this embodiment, the torsional zone of the shaft assembly is formed
in the
driving shaft 3 and in the driven shaft 8.
In other terms, with respect to the previously described embodiments, the
shaft
assembly comprises a torsional zone with increased length.
It is to be noted that the embodiments shown in figures 3 and 4, in which the
mounting
of the driven shaft and the driving shaft is performed by means of a fitted
flange,
enabling the torsional zone to be created at the manufacturing stage namely by
means
of forging and then by machining.
The implementation of the torsional zone consists, in particular, in the
realization of
the internal shaft within the driven shaft 8, through which the driven shaft 8
is coupled
driven to the driving shaft 3, and of an external shaft 13, which is then
assembled to
the driven shaft 8 and through which the latter is guided by the radial
bearing 9 in a
8
CA 02925413 2016-03-24
WO 2015/049295
PCT/EP2014/071057
way as to form a cylindrical throat between the two internal and external
shafts. In
other terms, and as this is illustrated with a dotted line in the figures, the
external shaft
is assembled around the zone of the shaft which has a reduced diameter.
Such an assembly can be obtained with various means. The hollow part can be
assembled on the rotor, for example close to the torsional zone, for example
by bolting
and/or through the diameter of the abutment and/or by means of a toothed hirth
and/or
by using many other assembly modes.
The embodiments shown in the figures 3 and 4, in which the driven shift
comprises an
internal shaft 12 and an external shaft 13, are also advantageous since the
external
shaft can then be used for the implementation of functions carried out by the
rotor.
In particular, a bearing support and/or a support of one or several wheel(s)
with
blade(s) can be realized (figure 3).
Obviously, the invention is not limited to the embodiments described above. .
It is also
possible, in a variant, to arrange the axial cylindrical throat driving shaft
and in the
driven shaft and to make sure, regarding both the driving shaft and the driven
shaft,
that the distance between the ends of the shafts, namely between the ends of
the two
exterior shafts 13 and 17, is equal to half of the torsional length or, in
other terms, to
ensure that the length of the interior shaft, which extends outside the
exterior shaft, is
equal to the length of the exterior shaft, as in the embodiment described in
the
reference to figure 2, both as regards the driving shaft and the driven shaft.
Therefore, in the embodiment shown in figure 5, the torsional zone can be
formed by
the realization, during the manufacture of the driven shaft, of a zone 18 with
diameter
that is reduced in a such a way as to confer on the coupling a torsional
character. As in
the previously described embodiment modes, the coupling with the driving shaft
can
be realized both by providing a shoulder E at the end, as shown, or by using a
fitted
flange.
9
CA 02925413 2016-03-24
WO 2015/049295
PCT/EP2014/071057
The reduced diameter zone can also be realized independently from the rest of
the
driven shaft and can be assembled, as previously indicated in the reference to
the
figures 2 to 4, to the driven shaft.
Obviously, as it was previously indicated, as an alternative the reduced
diameter zone
can be formed in the driving shaft or in the two driven and driving shafts. It
is to be
noted that, as in the embodiments shown in figures 1 to 4, the length of the
reduced
diameter zone is chosen in relation to the diameter of this zone in a way as
to confer a
torsional character on the shaft.
For example, for a shaft diameter of the order of 50 mm, the torsional zone
can be
realized over a length between 600 and 700 mm.
And finally, it is to be noted that in the different embodiments the axial
cylindrical
throat produced in the driven shaft and/or in the driving shaft, can be formed
by means
of electroerosion or by EDM ("Electrical Discharge Machining" ), which is a
machining procedure consisting in the removal of material in one piece by
using
electric discharges.
