U.S. patent application number 13/058602 was filed with the patent office on 2011-06-23 for fluid energy machine.
Invention is credited to Norbert Wagner.
Application Number | 20110150628 13/058602 |
Document ID | / |
Family ID | 41258491 |
Filed Date | 2011-06-23 |
United States Patent
Application |
20110150628 |
Kind Code |
A1 |
Wagner; Norbert |
June 23, 2011 |
FLUID ENERGY MACHINE
Abstract
A fluid energy machine is provided. The fluid energy machine
includes a housing having a motor, an impeller, at least two radial
bearings, and a shaft which extends along a shaft longitudinal axis
and which supports the impeller and a rotor of the motor wherein
the shaft is mounted in the radial bearings. The motor includes a
stator which at least partially surrounds the rotor in the region
of the motor. A gap which extends in the circumferential direction
along the shaft longitudinal axis is formed between the rotor and
stator and between the rotor and the radial bearings, which gap is
at least partially filled with fluid. The motor is embodied as a
bearing and is connected to a controller which activates the motor
so that forces acting radially with respect to a shaft longitudinal
axis can be exerted in addition to torques for driving the fluid
energy machine.
Inventors: |
Wagner; Norbert; (Bottrop,
DE) |
Family ID: |
41258491 |
Appl. No.: |
13/058602 |
Filed: |
August 11, 2009 |
PCT Filed: |
August 11, 2009 |
PCT NO: |
PCT/EP2009/060383 |
371 Date: |
February 11, 2011 |
Current U.S.
Class: |
415/1 ;
415/170.1 |
Current CPC
Class: |
F04D 29/58 20130101;
F04D 25/0686 20130101; F16C 2360/44 20130101; F16C 39/06 20130101;
F04D 13/0633 20130101; F04D 29/048 20130101; F04D 13/086 20130101;
F16C 37/005 20130101; F16C 32/0497 20130101; F04D 29/058 20130101;
F16C 32/0489 20130101; F04D 13/064 20130101 |
Class at
Publication: |
415/1 ;
415/170.1 |
International
Class: |
F04D 27/02 20060101
F04D027/02; F04D 29/08 20060101 F04D029/08 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 13, 2008 |
DE |
10 2008 038 787.8 |
Claims
1.-13. (canceled)
14. A fluid energy machine, comprising: a housing; a motor; an
impeller; at least two radial bearings; a shaft which extends along
a shaft longitudinal axis and supports the impeller and a rotor of
the motor, wherein the shaft is borne in the radial bearings,
wherein the motor includes a stator which at least partially
surrounds the rotor in the area of the motor, and a gap which
extends in a circumferential direction and along the shaft
longitudinal axis and is at least partially filled with a fluid is
formed between the rotor and the stator, as well as between the
rotor and the radial bearings, and wherein the motor is also in a
form of a bearing and is connected to a closed-loop control system
which drives the motor such that a plurality of radial forces with
respect to the shaft longitudinal axis can also be exerted, in
addition to a plurality of torques for driving the fluid energy
machine.
15. The fluid energy machine as claimed in claim 14, wherein the
housing is gas-tight.
16. The fluid energy machine as claimed in claim 14, wherein an
axial bearing is provided for bearing the shaft.
17. The fluid energy machine as claimed in claim 14, wherein a
process fluid, which is fed by the fluid energy machine, at least
partially flows around the rotor.
18. The fluid energy machine as claimed in claim 14, wherein a
split cage is provided in a gap between the rotor and the stator,
such that fluids which flow around the rotor do not reach that side
of the split cage on which the stator is located.
19. The fluid energy machine as claimed in claim 14, wherein the
radial bearings are magnetic bearings.
20. The fluid energy machine as claimed in claim 16, wherein the
axial bearing is a magnetic bearing.
21. The fluid energy machine as claimed in claim 17, wherein at
least one magnetic bearing is cooled by means of the process
fluid.
22. The fluid energy machine as claimed in claim 14, wherein the
motor is equipped with at least two winding systems with different
numbers of pole pairs.
23. The fluid energy machine as claimed in claim 14, wherein the
closed-loop control system is connected to a plurality of position
sensors and/or a plurality of oscillation sensors, and uses a
plurality of signals from the plurality of position sensors and/or
oscillation sensors as input signals to drive the motor.
24. The fluid energy machine as claimed in claim 14, wherein the
closed-loop control system is linked to measurements of the
electrical currents through a motor winding or to measurements of a
plurality of magnetic fluxes on the motor, and is designed such
that the measurements are used as an input signal for driving the
motor.
25. The fluid energy machine as claimed in claim 14, wherein the
fluid energy machine is a compressor or a pump.
26. A method for operation of a fluid energy machine, comprising:
connecting the closed-loop control system to two position sensors
and/or oscillation sensors for the shaft; using a plurality of
signals from the position sensors and/or the oscillation sensors as
input signals for driving the motor in order to produce radial
forces with respect to the shaft axis; and connecting the
closed-loop control system to two radial bearings which are in the
form of magnetic bearings, wherein the closed-loop control system
uses the plurality of signals as input signals for driving the
radial bearings.
27. The method as claimed in claim 26, wherein the closed-loop
control system is linked to a first plurality of measurements of
the electrical currents through a motor winding or to a second
plurality of measurements of the magnetic fluxes on the motor, and
uses the first and second plurality of measurements as an input
signal for driving the motor.
28. The method as claimed in claim 26, wherein the fluid energy
machine comprises: a housing; a motor; an impeller; at least two
radial bearings; a shaft which extends along a shaft longitudinal
axis and supports the impeller and a rotor of the motor, wherein
the shaft is borne in the radial bearings, wherein the motor
includes a stator which at least partially surrounds the rotor in
the area of the motor, and a gap which extends in a circumferential
direction and along the shaft longitudinal axis and is at least
partially filled with a fluid is formed between the rotor and the
stator, as well as between the rotor and the radial bearings, and
wherein the motor is also in a form of a bearing and is connected
to a closed-loop control system which drives the motor such that a
plurality of radial forces with respect to the shaft longitudinal
axis can also be exerted, in addition to a plurality of torques for
driving the fluid energy machine.
29. The method as claimed in claim 28, wherein the housing is
gas-tight.
30. The method as claimed in claim 28, wherein an axial bearing is
provided for bearing the shaft.
31. The method as claimed in claim 28, wherein a process fluid,
which is fed by the fluid energy machine, at least partially flows
around the rotor.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the U.S. National Stage of International
Application No. PCT/EP2009/060383, filed Aug. 11, 2009 and claims
the benefit thereof. The International Application claims the
benefits of German application No. 10 2008 038 787.8 DE filed Aug.
13, 2008. All of the applications are incorporated by reference
herein in their entirety.
FIELD OF INVENTION
[0002] The invention relates to a fluid energy machine, in
particular a compressor or pump, having a housing, a motor, at
least one impeller, at least two radial bearings, at least one
shaft which extends along a shaft longitudinal axis and supports
the at least one impeller and a rotor of the motor, wherein the
shaft is borne in the radial bearings, wherein the motor has a
stator which at least partially surrounds the rotor in the area of
the motor, and a gap which extends in the circumferential direction
and along the shaft longitudinal axis and is at least partially
filled with a fluid is formed between the rotor and the stator, as
well as between the rotor and the radial bearings.
BACKGROUND OF INVENTION
[0003] Fluid energy machines such as these are the object of
particularly intensive research efforts at the moment, because they
offer the capability to be embodied without seals. The motor, which
is generally in the form of an electrical drive, and the impeller
of the fluid energy machine, for example a compressor impeller, can
be arranged jointly in a single housing, sealed in a gas-tight
manner from the environment, such that the shaft does not require
any bushing to the outside. In this case, without any seals means
that no shaft seal has to seal a gap between a moving component and
a stationary component from the environment. Nevertheless, some
seals are required, for example in the area of the impellers, and
are normally in the form of labyrinth seals. The rotor and the
stator of the motor are surrounded by the process fluid since,
preferably, no shaft seal is also provided between the compressor
and the motor in the housing. The process fluid is correspondingly
located in the gaps between the rotor and the stationary
components--that is to say between the stator of the motor and the
rotor, in the bearings and in the back-up bearings. If the rotor or
the split cage is excited to oscillate, with the oscillation
changing the gap height in one of the circumferential gaps at a
circumferential position, and if the fluid has a significant
circumferential velocity in the gap between the rotor and the split
cage, then the local reduction in the gap height results in
acceleration in the resultant Couette flow which, in accordance
with Bernoulli's flow law, leads to a local pressure reduction, as
a result of which the forces which reduce the gap height are
increased in addition to the stimulated reduction of the gap
height. These aerodynamic or hydrodynamic forces increase as the
fluid density increases and, if sufficiently pronounced, can lead
to a contact between rotating and stationary parts, even resulting
in damage. It is essential to prevent a reduction such as this in
the availability of the fluid energy machine.
[0004] A split-cage motor which has at least one motor without any
bearings and drives a pump impeller arranged at the side is known
from WO 97/08808. The arrangement proposed there is suitable only
for operation of small fluid energy machines, since the impeller,
which is in each case arranged at a free shaft end, has a
restricted size and mass, from the rotor-dynamic point of view. A
multistage embodiment is not feasible in the described manner.
Hydrodynamic instability in the gap flow is not discussed.
SUMMARY OF INVENTION
[0005] Against the background of the problems described above, the
object of the invention is to provide a fluid energy machine of the
type mentioned initially, which has particularly high availability,
in particular with the aim of improving the operational reliability
of a large fluid engine machine.
[0006] The invention achieves the object by means of the features
additionally stated in the claims. The dependent claims, which
refer back thereto, include advantageous developments of the
invention.
[0007] According to the invention, an impeller should be understood
as meaning a rotating component which feeds a process fluid
depending on the purpose of the machine, or is driven thereby. By
way of example, this could be an impeller of a compressor.
Correspondingly, for example, a plurality of centrifugal impellers
may be arranged in-line or back-to-back in a centrifugal
compressor. The additional application of forces to the rotor of
the motor by means of separate magnetic fields which are produced
by the closed-loop control system, controlled by the stator,
ensures a more secure position of the rotor and an increased level
of concentricity of the shaft longitudinal axis with respect to the
split cage. Therefore, the rotor-dynamic and flow phenomena of
hydrodynamic instability, as described above, do not occur as early
and a further operating range can be made use of without any
risk.
[0008] It is particularly expedient to design the housing to be
gas-tight, with at least one inlet and one outlet being provided
for the process fluid to be fed by the fluid energy machine, or the
driving process fluid. In this sense, a gas-tight housing for the
purposes of the invention should be understood as meaning that
there is no need to provide a shaft seal in order to pass the shaft
out of the housing.
[0009] According to the invention, at least one axial bearing is
provided for defined bearing of the shaft in an axial position.
This axial bearing is preferably in the form of a magnetic bearing,
in the same way as the at least two separate radial bearings.
[0010] The saving of a complex shaft seal naturally results in the
disadvantage that the motor must be insensitive to exposure to the
process fluid, which is frequently chemically aggressive.
[0011] In this case, for example, the process fluid may be natural
gas, which is compressed under water and, in addition to the
chemically aggressive nature, also results in the difficulties of a
widely fluctuating pressure and coarse impurities.
[0012] In this case, it is expedient to protect at least the
interior of the stator of the motor against the process fluid, such
that a so-called split cage can be provided in the gap between the
rotor and the stator, which separates an area in which the process
fluid flows around the rotor from an area in which the interior of
the stator is arranged.
[0013] In this case, the stator is advantageously kept at a
suitable operating temperature by a separate cooling system by
means of a cooling fluid, with the rest of the components of the
machine preferably being cooled by means of the process fluid. In
particular, the bearings, which are preferably in the form of
magnetic bearings, can be cooled by means of the process fluid.
[0014] In this case, the split cage is subject to particular
requirements. In order to prevent it from being excessively heated,
because of eddy currents being induced in the alternating magnetic
fields of the stator, it should be electrically non-conductive. In
addition, it must be sufficiently mechanically robust, since high
pressure differences can occur between the process fluid and the
stator cooling fluid, which is generally separated from the process
fluid by means of the split cage. For acceptable efficiency, the
wall thickness of the split cage must not be excessively thick.
Furthermore, the split cage must be chemically resistant to the
process fluid.
[0015] In another preferred development of the invention,
components of the fluid energy machine are cooled by means of the
fluid to be fed, or the process fluid, in particular the bearings,
which are in the faun of magnetic bearings. Furthermore, the fluid
energy machine is preferably designed such that the process fluid
at least partially flows around the rotor.
[0016] In order to allow the motor to exert lateral forces in order
to stabilize the concentricity of the rotor with respect to the
split cage, it is expedient for the motor to have at least two
winding systems with different numbers of pole pairs.
[0017] It is also expedient for the closed-loop control system to
be connected to position and/or oscillation sensors, and to use
their signals as input signals to drive the motor. These sensors
can likewise be used for closed-loop control of radial magnetic
bearings, as a result of which there is no need for additional
components. Additionally or alternatively, the closed-loop control
system can be linked to measurements of the electrical currents
through the motor windings or to measurements of the magnetic
fluxes on the motor, and these can be used as an input signal for
exerting lateral forces on the rotor, in order to drive the
motor.
[0018] The advantages of the invention are particularly evident for
a multistage compressor or a multistage pump with a number of
impellers corresponding to the number of stages.
[0019] In a preferably physically short arrangement, the shaft can
be borne by means of two separate radial bearings, which are
arranged at the shaft ends and enclose the combination of the motor
and compressor between them.
[0020] With regard to the rotor dynamics, it is particularly
expedient for the motor and/or the impellers to be arranged along a
shaft longitudinal axis, and for a radial bearing to be provided in
each case at both ends of the motor along this shaft longitudinal
axis, and for a further radial bearing to be provided on the side
of the impeller or of the impellers facing away from the motor.
This arrangement, which comprises three separate radial bearings,
is ideally suitable for good rotor dynamics for multistage
compressors.
[0021] In conjunction with the closed-loop control system according
to the invention, which drives the motor such that radial forces
are also exerted with respect to the shaft longitudinal axis, in
addition to torques for driving the fluid energy machine, an
arrangement such as this has high availability, even in extreme
operating areas.
[0022] The invention also relates to a method for operation of a
fluid energy machine of the abovementioned type, in which an
additional drive for production of radial forces with respect to a
shaft longitudinal axis is superimposed by means of a closed-loop
control system for driving the motor for controlling a drive
torque, and in which at least two further radial bearings are
provided adjacent to the motor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The invention will be explained in the following text using
the description of one specific exemplary embodiment and with
reference to a figure. Further embodiment options will be evident
to a person skilled in the art from the disclosure, which options
which can be ascribed to the invention and differ from the
described exemplary embodiment. In the figure:
[0024] FIG. 1 shows a schematic illustration of a longitudinal
section through a fluid energy machine according to the invention,
with components of a closed-loop control system according to the
invention, which is illustrated in simplified foam, by means of
block symbols.
DETAILED DESCRIPTION OF INVENTION
[0025] The figure shows a longitudinal section through a fluid
energy machine 1, and a closed-loop control system 2, in the form
of a block diagram, each illustrated in a simplified form. The
fluid energy machine 1 has a compressor 3 and a motor 4, connected
by means of a common shaft 5 and arranged along a shaft
longitudinal axis 6 in a housing 7 which provides an external
gas-tight seal. The gas-tight housing 7 is gas-tight to the extent
that no bushing is provided for the shaft 5, which would have to be
sealed by means of a shaft seal. To this extent, the fluid energy
machine 1 can be described as having no seals, although shaft seals
are located between the individual stages of the compressor 3, in
order to cope with the pressure difference produced in the
stages.
[0026] The housing 7 has an inlet 8 and an outlet 9 for process
fluid 10, which is compressed by means of the compressor 3. In
addition to a main flow 13 through the inlet 8 and the outlet 9 and
a plurality of impellers 11 of the compressor 3, a smaller
proportion of the process fluid 10 flows from the last impeller 11
along a secondary flow path 12 as far as the first impeller 11.
[0027] The motor 4 has a rotor 15 and a stator 16, with the rotor
15 being supported by the shaft 5. The shaft 5 is borne in a first
radial bearing 17 and a second radial bearing 18, as well as an
axial bearing 19. Dashed lines in the figure show a third radial
bearing 20, which can optionally be provided. In this part, the
shaft 5 can also be formed by means of a quill shaft 21
(illustrated by dashed lines) in the area between the compressor 3
and the motor 4, such that it bends easily.
[0028] The compressor 3 has three stages, and correspondingly has
three impellers 11, but may also have fewer or more stages.
[0029] The bearings 17, 18, 19 and 20 are in the form of magnetic
bearings, and the secondary flow path 12 extends along these
bearings, in order to cool them. The process fluid 10 along the
secondary flow path 12 cools not only the magnetic bearings 17-20
but also the rotor 15 of the motor 4. The stator 16 is separated
from the rotor 15 by a gap 22, with the secondary flow path 12
extending through the gap 22. In order to ensure that the interior
of the stator 16 is not subjected to the process fluid 10, it is
encapsulated, and is separated toward the gap 22 by a so-called
split cage 24.
[0030] The stator 16 is cooled by means of separate stator cooling
25. The cooling fluid 26 which circulates in the stator cooling may
be at a different pressure than the process fluid 10 which is
present in the gap, with the split cage 24 absorbing the pressure
difference.
[0031] The motor 4 transmits a torque 30 to the compressor 3, in
order to drive the compression process. In this case, the
closed-loop control system 2 controls the rotation speed of the
fluid energy machine 1, with a rotation speed sensor 31 measuring
the rotation speed on the shaft 5, and passing on the measured
value to an inverter 40 in the closed-loop control system 2. The
inverter 40 supplies the stator 16 with the appropriate drive for
the nominal rotation speed value, and with a current at the
required voltage and frequency. A combined regulator and amplifier
41 in the closed-loop control system 2 passes the appropriate
nominal values for the rotation speed to the inverter 40. The
combined regulator and amplifier 41 is furthermore connected to two
position sensors, a first radial position sensor 50 and a second
radial position sensor 51, whose measured values are used by the
combined regulator and amplifier 41 to appropriately drive the
first radial bearing 17 and the second radial bearing 18 such that
the shaft 5 remains in its nominal spatial position. In addition,
the combined regulator and amplifier 41 uses the signals from the
radial position sensors 50, 51 in order to cause the inverter 40 to
produce a drive for the stator 16 of the motor 4, which is
superimposed on the drive for driving the compressor, resulting in
a discrepancy in the concentric position of the shaft 5 with
respect to the split cage 24, and which drive results in additional
radial forces 60 on the shaft 5.
[0032] In order to allow the motor 4 to produce the additional
radial forces 60, a first winding system 71 and a second winding
system 72 are provided in the stator 16, which winding systems 71,
72 have different numbers of pole pairs.
* * * * *