U.S. patent application number 15/688522 was filed with the patent office on 2018-01-25 for subsea pressure booster.
This patent application is currently assigned to Aker Solutions AS. The applicant listed for this patent is Aker Solutions AS. Invention is credited to Asbjorn ERIKSEN, Kjell Olav STINESSEN.
Application Number | 20180023573 15/688522 |
Document ID | / |
Family ID | 46830934 |
Filed Date | 2018-01-25 |
United States Patent
Application |
20180023573 |
Kind Code |
A1 |
STINESSEN; Kjell Olav ; et
al. |
January 25, 2018 |
SUBSEA PRESSURE BOOSTER
Abstract
Subsea turbomachine for boosting the pressure of petroleum fluid
flow from subsea petroleum productions wells or systems, comprising
an electric motor and a compressor or pump driven by the electric
motor, a fluid inlet and a fluid outlet, distinctive that the
turbomachine comprises a pressure housing common for the electric
motor or stator, and compressor, pump or rotor; a magnetic gear
inside the common pressure housing for operative connection between
the motor or stator and compressor, pump or rotor; and a partition
inside the common pressure housing, arranged so as to separate a
motor or stator compartment from a compressor, pump or rotor
compartment.
Inventors: |
STINESSEN; Kjell Olav;
(Oslo, NO) ; ERIKSEN; Asbjorn; (Skallestad,
NO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Aker Solutions AS |
Lysaker |
|
NO |
|
|
Assignee: |
Aker Solutions AS
Lysaker
NO
|
Family ID: |
46830934 |
Appl. No.: |
15/688522 |
Filed: |
August 28, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14004029 |
Dec 10, 2013 |
9841026 |
|
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PCT/NO2012/000028 |
Mar 15, 2012 |
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15688522 |
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Current U.S.
Class: |
417/420 ;
417/410.1; 417/423.11; 417/423.14; 417/423.3 |
Current CPC
Class: |
F04D 13/08 20130101;
F04D 13/086 20130101; F04D 13/026 20130101; F04D 17/122 20130101;
F04D 13/024 20130101; F04D 25/028 20130101; F04D 25/026 20130101;
F04D 25/0686 20130101; F04D 1/06 20130101; F04D 13/0653 20130101;
F04D 13/028 20130101 |
International
Class: |
F04D 13/02 20060101
F04D013/02; F04D 13/06 20060101 F04D013/06; F04D 25/02 20060101
F04D025/02; F04D 1/06 20060101 F04D001/06; F04D 17/12 20060101
F04D017/12; F04D 13/08 20060101 F04D013/08; F04D 25/06 20060101
F04D025/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2011 |
NO |
20110398 |
Claims
1-15. (canceled)
16. A subsea turbomachine for boosting pressure of a petroleum
fluid flow from subsea petroleum production wells or systems, the
subsea turbomachine comprising: an electric motor comprising a
rotor and a stator, the rotor and the stator being disposed in a
motor compartment; a pump or compressor, disposed in a pump or
compressor compartment; a petroleum fluid inlet to and a petroleum
fluid outlet from the pump or compressor compartment; a common
pressure housing for the motor compartment and the compressor or
pump compartment; a magnetic gear inside the common pressure
housing for operative connection between the electric motor and the
compressor or the pump; an electric motor shaft and one pump or
compressor shaft; wherein an outer ring of the magnetic gear is
connected to the electric motor shaft and an inner ring of the
magnetic gear is connected to the one pump or compressor shaft, or
opposite; wherein the electric motor shaft and the one pump or
compressor shaft are suspended in bearings; and a partition inside
the common pressure housing, arranged between the inner and outer
magnetic gear rings so as to separate the motor compartment
hermetically from the pump or compressor compartment, wherein the
subsea turbomachine has no external barrier fluid system or
supply.
17. The subsea turbomachine according to claim 16, further
comprising a pressure balancing device comprising an arrangement
between an inlet side of the pump or compressor compartment and the
motor compartment.
18. The subsea turbomachine according to claim 16, further
comprising a pressure balancing device comprising two contra valves
being controlled by measurement of pressure differential between
the motor compartment and the pump or compressor compartment.
19. The subsea turbomachine according to claim 16, further
comprising a liquid filled motor compartment.
20. The subsea turbomachine according to claim 16, further
comprising a gas filled motor compartment.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to pressure boosting. More
specifically, the invention relates to compressors and pumps,
particularly subsea compressors and pumps, including multiphase
pumps, for boosting the pressure of gas, multiphase or liquid from
subsea petroleum production wells or systems. In the follow will be
used a common term: Pressure boosters; for turbo machines such as
compressors, multiphase pumps and liquid pumps.
BACKGROUND OF THE INVENTION AND PRIOR ART
[0002] The pressure of a petroleum reservoir, particularly a gas
reservoir, decline rather rapidly during production. In order to
maintain and prolong production from subsea reservoirs, often
involving long transport through a pipeline of the produced fluid,
pressure boosting is required.
[0003] In FIG. 1 is illustrated the process of a subsea compression
station. The rotating equipment is compressors and pumps. The
rotational speed of pumps is typically in the range of 3000-4000
rpm while compressors operate typically in the range of 5000-12000
rpm.
[0004] Reference is made to Table 1 for understanding of this
figure. To give an idea of dimensions, the diameter of the
separator in FIG. 1 can be in range of 3 m and height 10 m.
TABLE-US-00001 TABLE 1 Item # Explanation a Separator b Compressor
b' Compressor motor c Pump c' Pump motor d Lower liquid level e
High liquid level f High-high liquid level g Polishing equipment,
e.g. cyclones g' Lower edge of cyclones h Downcomer i Outlet from
downcomer j Antisurge valve with actuator k Antisurge cooler l
Cable for supply of electric power to compressor motor m Cable for
supply of electric power to pump motor n Liquid recirculation pipe
o Gas recirculation pipe p, p', p'', p''' Valves q Electric
connector for compressor motor q' Electric connector for compressor
motor r Liquid recirculation valve
[0005] A typical power requirement for pressure boosting of such a
compressor train is 5-15 MW. This, combined with high transmission
frequency, limits the length of an electric subsea step out cable,
laid out from and controlled from surface (topside or onshore) via
a surface variable speed drive (VSD). More specifically, the
Ferranti effect, and possibly also other effects, limits the subsea
length of high power high frequency electric step out cables to
about 40-50 km.
[0006] The state of the art of subsea compressors
(motor-compressors) are indicated in FIG. 2 where the main
components are the compressor which is driven by an electric high
speed motor that rotates at the speed that the compressor needs,
i.e. the motor rotates at a speed typically in the range of 5000 to
12000 rpm. The motor speed is transmitted to the compressor by at
least one shaft that connects motor and compressor. The frequency
of the electric power to give this speed for the motor and thereby
the compressor must be in the range of approximately 80 to 200 Hz
for a 2-pole motor. The shaft power of the compressor motor can
typically be in the range of 5-15 MW and possibly larger in the
future. Stable transmission of electric power at the high
frequencies that the motor requires is feasible if the distance
from the power supply, normally from onshore or topsides (surface)
is limited to the range of 40-50 km. If the step out distance is
more than this, the power transmission through the cable becomes
instable and inoperable. In such cases there will be contradictory
requirements between the high frequency that the motor needs to
give the right speed and the low frequency, say typically 40-70 Hz,
which is necessary to have a stable power transmission. This
contradiction can be resolved by low frequency power transmission
and local increase of frequency by placing a subsea variable speed
drive (SVSD) close to the motor.
[0007] The atmosphere of the motor-compressor in FIG. 1 will be
gas, either the gas being boosted or an inert gas supplied from a
reservoir. The term inert gas in the context of this patent
description means any gas that is not harmful to the internal
materials of the motor, and also of the gear in cases where such a
gear is located in the same compartment as the motor. Typically the
inert gas can be dry nitrogen or dry methane, however, dry nitrogen
is preferable and shall in the context here cover all types of
applicable inert gases.
[0008] In cases where pumps have liquid filled motor, the motor is
filled with an inert liquid, i.e. a liquid that is not harmful to
the internal materials of the motor and of the gear in cases where
a gear is located in the same compartment as the pump.
[0009] It shall be mentioned that only main components necessary
for understanding of the state of the art of subsea
motor-compressor included in FIG. 2. and the following FIGS.
3-6.
[0010] Other vital components necessary for design of a complete
operable subsea compressor or pressure booster not included are:
Motor gas cooling system, HV power connectors for transmission of
power to the motor, LV cables for signal and control of the
magnetic bearings, balance piston and others.
[0011] However, while subsea processing equipment has gained
acceptance over the resent years for being a realistic option,
there is more reluctance against electric and electronic equipment,
i.e. a perception of that this type of equipment will have low
reliability and robustness. This is particularly valid for static
subsea variable speed drives, VSD for electric motors. [VSD is also
called variable frequency drive (VFD) and frequency converters.] It
is therefore a common view in the professional environment that the
risk for lost production by application of subsea VSDs is
considered to be high and they should if possible be avoided. A
SVSD (subsea VSD) will also be large in dimensions and weight and
therefore not easy to install and retrieve. The cost will also be
high.
[0012] A subsea VSD located near the turbomachine will allow a low
frequency high power electric power transmission through the subsea
step out cable, which allows a far longer step out length. However,
the cost of a feasible subsea VSD for a motor of 10 MW can
indicatively be 100 MNOK, the weight about 100 tons, the height
about 11 m and the diameter about 3 m. But a worse problem is the
risk of limited reliability of a subsea VSD.
[0013] Even though the subsea VSD contains top quality components,
each of very high quality and reliability, the large number of
components and the complexity of the structure result in a total
subsea VSD reliability that may be a significant problem.
[0014] A demand for further improvement still exists, for pressure
boosters in general and subsea pressure boosters in particular, and
the objective of the present invention is to meet said demand.
SUMMARY OF THE INVENTION
[0015] The demand is met with a subsea turbomachine for boosting
the pressure of petroleum fluid flow from subsea petroleum
productions wells or systems, compnsing an electric motor and a
compressor or pump driven by the electric motor, a fluid inlet and
a fluid outlet, distinctive that the turbomachine comprises [0016]
a pressure housing common for the electric motor or stator, and
compressor, pump or rotor; [0017] a magnetic gear inside the common
pressure housing for operative connection between the motor or
stator and compressor, pump or rotor; and [0018] a partition inside
the common pressure housing, arranged so as to separate a motor or
stator compartment from a compressor, pump or rotor
compartment.
[0019] The partition preferably comprises magnetic pole pieces or
electromagnets or both, for modulating the magnetic field coupling
and gear ratio of the magnetic gear. The gear ratio can be
controlled by enegizing or not energizing electromagnets in the
partition. In general, the low speed side is the motor or stator
side, typically at speed up to about 4000 revolutions per
minute--rpm, whilst the high speed side is the compressor, pump or
rotor side, typically at speed up to about 12000 rpm, at an effect
up to about 15 MW. However the speeds and effect can, at least in
the future, be varied beyond the limits indicated here.
[0020] The magnetic gear is preferably a magnetic step-up gear
allowing subsea step out lengths far above 40 km since the Ferranti
effect can be handled. A magnetic step up gear is estimated to
result in reliability much higher than that of a SVSD. Indicatively
cost of such a gear will be in the range of 10-15% of that of a
SVSD, diameter in the range of 1.5 m and length 1.5 m and weight in
the range of 5-10 tonnes. Compared to use of SVSD it is very
favourably to arrange a magnetic step-up gear between the motor and
the compressor to increase the speed from the low speed of the
motor necessary for stable electric transmission to speed that is
required for the compressor. Typically the step-up ratio of the
gear can be in the range of 2-3, but the invention covers all
ratios from 1, i.e. a magnetic 1:1 coupling, up to what can be
necessary from case to case. Compared to prior art solutions, the
reliability can be 10 times better, each of size and weight and the
cost can be 1/10. Many embodiments of the pressure booster of the
invention is contactless, having magnetic gear and magnetic
bearings, providing extremely low loss combined with extremely high
reliability, making said embodiments particularly favourable both
subsea and on dry locations.
[0021] The magnetic gear can be of any type, e.g. parallel,
planetary and cycloid type. Normally the gear is a permanent magnet
gear, but gears with electromagnets either on the motor side (i.e.
the low speed side) or the compressor side or both sides can also
be adapted for subsea pressure boosters.
[0022] A favourable design of the magnetic gear is a cycloid
permanent magnet gear operatively connecting the motor and
turbomachine, more preferably an inner cycloid permanent magnet
gear of which the inner ring of the gear is connected to the
turbomachine. This allows a very high torque transfer because the
permanent magnets of the inner ring are influenced by the permanent
magnets of the outer ring for a larger number of magnets,
increasing the magnetic coupling and thereby the torque transfer
capability. A further advantage is a compact construction compared
to conventional spur gear design since one ring is inside the
other, and also the simple design which improves reliability and
requires no bearings.
[0023] A planetary gear will also have these favourable features
and more perfect alignment of motor and compressor shaft. Planetary
gear embodiments can be very favourable since the torque transfer
can be very high due to a large number of pole interactions and the
stability can be very good due to symmetrical design with the
shafts of the motor and turbomachine coaxially arranged. Also,
planetary gears can be arranged so as to allow gear shift.
[0024] As mentioned above the invention shall not be limited with
respect to type of magnetic gear and it can either be of the
permanent magnet or the electromagnet type. The most suitable type
of gear will be selected from case to case base among other things
on the state of the art of the various types
[0025] A magnetic gear can be arranged like a gear box where the
step-up ratio can be changed in steps. This can be done at
standstill of the pressure booster by ROV or by an electric motor
mounted in the gear box.
[0026] A more conventional way to change step-up ratio is to
retrieve the pressure poster and exchange the gear with another
gear with the desired new step-up ratio. This can be done I
connection with re-bundling of the compressor or pump.
[0027] Magnetic gears with electromagnets either on the low speed
motor side or the high speed turbomachine side, makes it possible
to continuously vary the speed of the turbomachine by increasing or
reducing the rotational speed of the magnetic field of the
electromagnets, by energizing or not energizing electromagnets.
[0028] The motor, gear and compressor will be arranged in common
pressure housing, however one or more partition with shaft seals is
located between the main components dividing the common pressure
housing into compartments where the main components are installed.
A favourable design to protect motor and gear with their magnetic
bearings is to have a partition between a compartment containing
motor and gear on one side of at least one shaft seal and the
compressor on the other side.
[0029] The pressure housing can be one piece, since the number of
possible fluid leakage paths thereby is minimised. Alternatively,
the pressure housing can have flanges between the compartments with
main components if this is found favourable for replacing
components at a later stage, for example in order to increase a
compressor speed at the tail end production from a reservoir by
increasing the gear ratio.
[0030] The pressure booster preferably comprises shafts with
magnetic bearings, one shaft for the motor with the low speed part
of the gear and one shaft for the turbomachine with the high speed
part of the magnetic gear. If cycloid gear is used, an outer ring
of the magnetic gear is connected to the motor shaft and an inner
ring of the magnetic gear is connected to the turbomachine shaft.
Each shaft is suspended in two radial magnetic bearings, one in or
near either end, and one thrust magnetic bearing and a 5-axis
control system is operatively connected to the bearings of each
shaft The magnetic bearings require a comprehensive control system
in order to be operative, requiring a control unit on the seabed,
since the shafts are actively controlled by the electromagnets of
the bearings in order to rotate without physical contact. A 5-axis
control system is favourable because it is a proven design and
verified to have sufficient reliability for the purpose.
[0031] Even though two radial and one axial bearing is sufficient
for one shaft, the number of bearings shall not be a limitation to
the invention.
[0032] Alternative bearings, such as mechanical bearings are
possible but will result in need for lube oil susceptible to
contamination form the boosted media and requires a rather
complicated lube oil system.
[0033] Compared to state of the art high speed subsea pressure
boosters, which includes a subsea VSD, the booster type of the
invention is estimated to have a much higher reliability,
presumably in the order of a decade better. And so are dimensions,
weight and cost. There exist therefore strong cost and technical
incentives for the invention.
[0034] By separating the motor and the gear with their bearings
from the turbomachine by a partition or diaphragm with a shaft
seal, i.e. such that the motor with gear and the turbomachine are
located in separate compartments, it will be possible to protect
the motor and gear from harmful amounts of contaminants from the
boosted media by supply of small supply of an inert fluid with
respect to the motor and gear matenals such that this fluid at all
time constitutes the major composition of the motor-gear volume,
and contaminants that should enter this volume will be diluted to
non-damaging concentrations. The supplied inert fluid will be lost
by flowing through the seal.
[0035] As example can be indicated that the loss of inert liquid
for a pump is in the order of 1 litre per day per seal.
[0036] For a compressor the atmosphere of the compartment for gear
and motor in theory should be kept protected from contaminant by
having a flow velocity of an inert gas through a seal higher than
the diffusion velocity of the contaminants. If the total atmosphere
volume of the motor and gear included gas cooler and piping is 2
m.sup.2, it is assumed that a supply of inert gas, e.g. dry
nitrogen or dry methane, at a rate that results in some few volume
exchanges per year is enough to protect the materials from being
damaged
[0037] If for example a pressure vessel or tank of 10 m.sup.3 is
located on or at the compressor and has starting pressure of 450
bar and the suction pressure of the compressor is 50 bar, an
estimate will result in that the 2 m.sup.3 atmosphere of the
motor-gar compartment can be exchanged approximately 20 times, i.e.
with one exchange of atmosphere per month the tank will last for
well below one year before recharging, which can be done from ship
by ROV when necessary.
[0038] Another design that completely protects the motor and the
low speed gear part at the motor or stator side from contaminants
is by hermetically separating the low and the high speed part
(compressor or rotor side) by a partition or separation wall,
sometimes called shroud, similar to what is used for magnetic
couplings. To keep the necessary strength and thereby thickness of
the shroud reasonable, the pressure difference between the
compressor and motor atmosphere should at all time be kept within
acceptable limits by some kind of pressure balancing device. The
partition, shroud or separation wall is for the most part
non-magnetic but should however preferably comprise pole pieces or
electromagnets arranged in the partition between the magnets on
either side of the partition in order to modulate the gear coupling
and gear ratio.
[0039] A very preferable embodiment of the invention is a
turbomachine distinctive in that it is a pressure booster
comprising a stator compartment and a rotor compartment, the rotor
compartment comprises a compressor or pump arranged directly on the
rotor or coupled to the rotor. The compartments are separated with
a diaphragm, partition or shroud, preferably hermetically
separated, and pole pieces or electromagnets are arranged in the
partition between the magnets on either side of the partition in
order to modulate the gear coupling and gear ratio. Said
turbomachine is for subsea and topsides use since the solution
appears to be completely novel.
FIGURES
[0040] FIGS. 1 and 2 illustrate prior art solutions,
[0041] FIGS. 3 to 6 illustrate embodiments and features of the
present invention, and
[0042] FIG. 7 gives examples of magnetic gears.
[0043] FIG. 8 illustrates a preferable embodiment of the invention,
and
[0044] FIG. 9 illustrates in some more detail the magnetic gear of
a subsea turbomachine of the invention.
DETAILED DESCRIPTION
[0045] In the following the invention in several embodiments will
be illustrated and explained by figures. Reference is made to Table
2 for understanding of FIG. 3-5. It shall be mentioned that only
main components necessary for understanding of the invention are
included in FIGS. 3-6.
TABLE-US-00002 TABLE 2 Item # Explanation 1 Motor 2 Compressor or
other turbomachine 3 Pressure housing 4 Shaft seal 4' Partition 5
Compressor (or other turbomachine) inlet 6 Compressor (or other
turbomachine) outlet 7 Compartment for motor and magnetic gear or
low speed part of the magnetic gear 8 Compartment for compressor
and high speed side of gear 9, 9' Shafts 10 Shaft coupling either
rigid or flexible or common shaft for compressor and motor 11, 11',
11'', Radial bearings 11''' 12, 12' Axial bearings 13 Magnetic gear
14 Low speed side of magnetic gear 15 High speed side of magnetic
gear 16 Partition, diaphragm or shroud hermetically separating low
and high speed of gear 17 Pressure vessel or tank for nitrogen 18,
18' Control valves 19 Pressure-Volume-Regulator (PVR) 20, 20', 20''
Tubes
[0046] Reference is made to FIG. 3 illustrating a pressure booster
in the form of a compressor with magnetic gear and electric motor,
and where the magnetic gear has a step-up ratio that steps up the
speed from that of the motor shaft, which is low enough to be
supplied with a low enough frequency to have stable cable
transmission, to the necessary speed of the compressor. The motor
can for instance rotate with a speed of 3000 rpm, i.e. the electric
power has a frequency of 50 Hz for a 2-pole motor, and the gear can
have a step up ratio of 2.5:1, meaning that the compressor has a
speed of 7500 rpm. If the surface located power source has a VSD,
the frequency can for instance be varied between 33 and 67 Hz. A
partition 4' is arranged between the magnetic gear 13 and the
pressure housing and inside the magnetic gear, not shown, between
the gear higher speed and lower speed sides.
[0047] Reference is made to FIG. 4 illustrating that there is a
partition 4' with a shaft seal between the compressor 2 in
compartment 8 and the motor and magnetic gear in compartment 7.
Pressure vessel or tank 17 contains nitrogen reservoir at high
pressure, e.g. 400 bar charging pressure, and nitrogen is supplied
in a small but sufficient rate to the motor-gear compartment to
keep its atmosphere harmless with respect to ingress harmful
components of boosted gas which in principle will be kept our of
the motor-gear compartment by flow of nitrogen from motor
compartment and into the compressor. Some ingress of contaminants
from the gas being boosted may sometimes happen, but these
components will be diluted to harmless levels by the continuous
supply of nitrogen. Alternatively the nitrogen can be supplied by
tube in an umbilical.
[0048] If the arrangement shown in FIG. 4 with supply of nitrogen
from a pressure vessel is used, the flow regulation by valve 18 can
be controlled by measurement of the pressure in the vessel 17. The
decrease of the pressure is expression for the flow out of the
vessel with sufficient accuracy because the temperature of the gas
volume in the tank is close to constant, i.e. the seawater
temperature, that at deep water is close to constant year around.
Alternatively to setting a small flow of nitrogen through valve
based on calculations and expenence to keep the nitrogen atmosphere
in compartment 7 harmless, the valve can be controlled by having
sensors in the nitrogen atmosphere that measures the concentration
of contaminants in the nitrogen; e g. total hydrocarbons, selected
hydrocarbons (e.g. heavy hydrocarbon molecules) water vapour,
H.sub.2S, CO.sub.2, MEG vapour or other harmful components that
indicates the degree of contamination of the atmosphere. The valve
18 can than based on these measurements regulate the supply of
nitrogen to keep the degree of contamination below a harmful level.
This level can be established by experience and knowledge about the
tolerance of the various contaminants of the materials in
compartment 7. The control of valve 18 can either be continuous or
intermittent.
[0049] In FIG. 5 is given an illustration of a compressor where the
high speed motor side of the magnetic gear is hermetically
separated from the low speed motor side by a partition or diaphragm
also called shroud. In this way the motor with its part of the gear
and magnetic bearings is hermetically separated (compartment 7)
from the compressor with the high speed part of the gear and
magnetic bearings (compartment 8). Some kind of pressure balancing
of the pressure of the motor-gear atmosphere of compartment 7
compared to the suction pressure of the compressor in compartment 8
will be necessary to keep the requirements of the strength of the
shroud reasonable. In FIG. 5 the pressure balancing is arranged by
supply of nitrogen from tank 17 (or alternatively from tube in
umbilical) through pressure transmitting tube 20 and by a
Pressure-Volume-Regulator, PVR, which is a well known and verified
device. A pressure transmitting tube is connected to the compressor
compartment, and the PVR will continuously compare and control the
pressure of the motor-gear atmosphere to be close to the compressor
suction pressure. Pressure balancing can also be arranged with an
arrangement of pressure regulating valves 18 and 18' and pressure
sensor or sensors that detects the pressure difference between the
motor-gear compartment and the compressor suction pressure.
[0050] In FIG. 6 is illustrated pressure balancing by use of two
contra valves being controlled by measurement of pressure
differential between compartments 7 and 8. Nitrogen is supplied by
control valve 18 while overpressure in compartment 7 compared to
compressor suction pressure is released by control valve 18'
[0051] In FIG. 7 is illustrated following types of magnetic gears:
Spur (parallel, radial), planet and cycloid gear.
[0052] FIG. 8 illustrates a preferable embodiment of the invention
wherein a stator 21 is arranged in a stator compartment 22,
separated by a partition 16 from a rotor compartment 28, the rotor
compartment comprises a compressor 2 or pump arranged directly on
the rotor shaft or coupled to the rotor 23. Preferably, pump or
compressor impellers, or both, are arranged directly on the rotor
shaft. Preferably the partition 16 seals the stator compartment
hermetically from the rotor compartment. The partition preferably
includes pole pieces 24, electromagnets or both, for enhanced
magnetic coupling, arranged between the gear sides, for a set or
controllable gear ratio. The gear ratio can be controlled by
controlling optional electromagnets in the partition, the rotor
position can be inferred from the impedance of the stator, by using
an algorith or a look up table. The rotor shaft may preferably
comprise bearings on either end, and also on the shaft between
rotor and impellers if required.
[0053] FIG. 9 illustrates a preferable subsea turbomachine or a
general purpose turbomachine or pressure booster according to the
invention, wherein the magnetic gear is a radial magnetic gear with
the partition 16 arranged between the inner part 25 and outer parts
26. Increasing the length of the gear allows better magnetic
coupling and transfer of higher effect, which is preferable, but
may require extra bearings on the gear end of the shaft. The
partition comprises magnetic pole pieces 25 or electromagnets or
both in the partition between the lower speed and higher speed
sides of the gear. The number of pole pieces and/or electromagnets
are related to the gear ratio, preferably the number of rotor
elements and the number of pole pieces or electromagnets are
multiples or fractions of the number of stator elements, the
multiple or fraction ratios relate to the gear ratio. The gear
ratio can be controlled by enegizing or not energizing
electromagnets in the partition, said electromagnets are preferably
connected electrically to the stator power source or side, avoiding
any slip rings or other rotatable electric connections. This figure
illustrates in more detail the magnetic gear, the partition 16 and
pole pieces 24 or similar, and the common pressure housing 3,
whilst the motor with stators 21 and rotor 23, and the compressor 2
are illustrated out of scale and not to detail, for clarity.
Bearings and some other features are for clarity not illustrated or
only indicated in order to show more clearly how the magnetic gear
coupling can be configured and arranged. With a radial gear of the
type illustrated, which side is the inner or outer side or faster
or slower side can be subject to a choice of design, however, in
many cases the faster side should be the inner side since this will
in most cases result in lower stress levels.
[0054] Some of the advantages of the invention are as follows:
[0055] Non-contact elements--no friction between the elements.
[0056] High torque transfer due to multiple pole interaction.
[0057] Utilization of peak torque.
[0058] Input and output shafts can be isolated.
[0059] Increased temperature range, no elastomeric seals.
[0060] Inherent overload protection.
[0061] Increased tolerance of misalignment.
[0062] Several options for arranging shift of gear ratio, several
mechanical and several electronic options.
[0063] The liquid lubrication system and supply can be
eliminated.
[0064] The pressure boosters or turbomachines of the invention may
include any features as described or illustrated in this document,
in any operative combination, each such combination is an
embodiment of the present invention. The invention also provides
use of the turbomachine and pressure booster of the invention, for
pressure boosting fluids subsea and topsides, particularly gas and
oil subsea.
* * * * *