WO2024183953A1

WO2024183953A1 - Turbomachine provided with a switched reluctance motor

Info

Publication number: WO2024183953A1
Application number: PCT/EP2024/025099
Authority: WO
Inventors: Mallikarjuna Reddy PEDDI; Uday Karthik MEDURI; Vidyasagar RENGASAMY RAMALINGAM; Stefano DEL PUGLIA; Kathiravan SELVAM
Original assignee: Nuovo Pignone Tecnologie - S.R.L.
Priority date: 2023-03-07
Filing date: 2024-03-01
Publication date: 2024-09-12

Abstract

A turbomachine (1), comprising: a casing (12) comprising a fluid inlet (122) and a fluid outlet (124); one or more stages (14) sequentially arranged in the casing (12); and a flow path (16) that extends from the fluid inlet (122) to the fluid outlet (124) through the one or more stages (14); wherein each stage of the one or more stages comprises an impeller (142) and an electric motor, the impeller (142) being located at least in part within the flow path (16), the electric motor comprising a rotor (144) and a stator (146), wherein the rotor (144) is coupled with the impeller (142) and is configured to rotate the impeller (142), the stator (146) being arranged to be stationary with the casing (12); the turbomachine being characterized in that: the stator (146) comprises a plurality of electromagnets and the rotor (144) is made of a magnetically permeable metal.

Description

TURBOMACHINE PROVIDED WITH A SWITCHED RELUCTANCE MOTOR

Description

TECHNICAL FIELD

[0001] The present disclosure concerns a turbomachine provided with electric motors. More specifically, the subject matter disclosed herein refers to pumps or compressors suited particularly for pumping fluids, such as water or other compressible fluids.

BACKGROUND ART

[0002] Turbomachines with electric motors are often used in numerous industrial fields, such as petroleum refineries, oil production platforms, submarine systems, offshore installation etc. Turbomachines can comprise Electrical Submersible Pumps (ESPs), submarine electrical motors and the like.

[0003] A turbomachine can comprise one or more stages each of which applies kinetic energy to compress and/or transport a fluid through a flow path by means of an impeller. The rotation of the impeller is driven by an electric motor coupled with the impeller and arranged within the turbomachine.

[0004] Currently, turbomachines may be equipped with Permanent Magnet Synchronous Motors (PMSMs).

[0005] For example, US10294949 discloses a multistage turbomachine, comprising a casing with a fluid inlet and a fluid outlet and a plurality of stages sequentially arranged in the casing. A flow path extends from the fluid inlet to the fluid outlet through such stages. Each stage is comprised of a rotating impeller and an electric motor embedded in the casing and arranged for rotating the impeller at a controlled rotary speed. Each electric motor comprises a motor rotor, arranged on the impeller and integrally rotating therewith, and a motor stator stationarily arranged in the casing.

[0006] Documents US 8430653, WO 2019/199318, US 11098726 and US 6616421 are representative of the available prior art.

[0007] However, turbomachines with PMSM motors currently available require permanent magnets in the rotor with the result that turbomachines of this kind have a bulky construction. Moreover, the permanent magnets are conventionally made from alloys of rare-earth elements which are heavy and expensive.

[0008] It may be beneficial to improve a turbomachine.

SUMMARY

[0009] Certain aspects commensurate in scope with the originally claimed disclosure are summarized below. These aspects are not intended to limit the scope of the claimed disclosure, but rather these aspects are intended only to provide a brief summary of possible forms of the disclosure. Indeed, the full disclosure may encompass a variety of forms that may be similar to or different from the aspects set forth below.

[0010] In one aspect, the subject matter disclosed herein is directed to a turbomachine, comprising: a casing comprising a fluid inlet and a fluid outlet; one or more stages sequentially arranged in the casing; and a flow path that extends from the fluid inlet to the fluid outlet through the one or more stages, wherein each stage of the one or more stages comprises an impeller and an electric motor. The impeller is located at least in part within the flow path and the electric motor comprises a rotor and a stator, wherein the rotor is coupled with the impeller and is configured to rotate the impeller and the stator being arranged to be stationary with the casing. In particular, the stator comprises a plurality of electromagnets and the rotor is made of a magnetically permeable metal.

[0011] In another aspect, the subject matter disclosed herein is directed to a turbomachinery plant comprising a turbomachine as defined above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

Fig. 1 illustrates an axial cross-sectional view in the plane XZ of a turbomachine provided with electric motors, according to the prior art, wherein the turbomachine comprises a plurality of sequentially arranged stages; Fig. 2 illustrates a perspective view of the turbomachine shown in Fig. 1, showing a detailed view of a single stage of the turbomachine.

Fig. 3 is an excerpt of Fig. 2 showing an enlarged view of a detail of the stage of the turbomachine.

Fig. 4 shows a perspective view of a detail of PMSM motor of the turbomachine shown in Fig. 1-3.

Fig. 5 illustrates a perspective view of an axial cross-section in the plane XZ of a turbomachine provided with electric motors, according to a first embodiment of the present disclosure, showing a detailed view of a single stage of a turbomachine;

Fig. 6 is an excerpt of Fig. 5 showing an enlarged view of a detail of the stage of the turbomachine, according to a first embodiment of the present disclosure.

Fig. 7 shows a perspective view of a detail of a Switched Reluctance Motor (SRM) motor of the turbomachine shown in Fig. 5-6.

Fig. 8 illustrates a perspective view of an axial cross-section in the plane XZ of a turbomachine provided with electric motors, according to a second embodiment of the present disclosure, showing a detailed view of a stage of a turbomachine;

Fig. 9 illustrates an axial cross-sectional view in the plane XZ of a detail of the stage of the turbomachine shown in Fig. 8, according to the second embodiment of the present disclosure.

Fig. 10 is an excerpt of Fig. 9 showing an enlarged view of a detail of the stage of the turbomachine, according to the second embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0013] In the field of turbomachinery plants, such as petroleum refineries, oil production platforms, submarine systems, offshore installation etc, turbomachines may be equipped with one or more PMSM motor.

[0014] Reference is now made to the drawings and particularly to Fig. 1 that shows an axial cross-sectional view in the plane XZ of a turbomachine 1 with a PMSM motor in accordance with the available prior art.

[0015] The turbomachine 1 of Fig. 1 can be for example a wet-gas compressor or a pump, or more generally a turbomachine 1 suitable for boosting the pressure of a fluid and/or for generating a flow from a fluid inlet 122 to a fluid outlet 124. The liquid may be a compressible liquid, such as a liquid containing a percentage of a gaseous medium.

[0016] The turbomachine 1 comprises a casing 12 including a fluid inlet 122 and a fluid outlet 124 and one or more stages 14 sequentially arranged in the casing 12. The fluid inlet 122 is in fluid communication with the fluid outlet 124 through a flow path 16 which extends from the fluid inlet 122 to the fluid outlet 124 through the one or more stages 14 of the turbomachine 1.

[0017] As shown in Fig. 1, the turbomachine 1 comprises a plurality of axial stages 14 arranged in sequence between the fluid inlet 122 and the fluid outlet 16. In the partial view of Fig. 1 there are shown only two axial stages 14. Each stage is separated from the next stage by a stationary diaphragm 18, which is a stationary portion of the turbomachine 1 configured to accommodate the inner case internally. Each stage includes a rotatable impeller 142 which can be driven into rotation by a respective embedded motor.

[0018] Fig. 2 illustrates a perspective view of the turbomachine 1 shown in Fig. 1, showing a detailed view of a single stage 14 of the turbomachine 1. The stage 14 comprises an impeller 142 and an electric motor. Fig. 3 shows an excerpt of Fig. 2 showing an enlarged view of the single stage of the turbomachine.

[0019] As can be seen in Fig. 2 and 3 the impeller 142 is located at least in part within the flow path 16 to engage with the fluid and for boosting the pressure of a fluid and/or generating a fluid flow. The impeller 142 is provided with respective impeller blades which may include a root portion, an airfoil portion and a tip portion. The blades may be annularly arranged blades forming a monolithic ring that is coupled with the rotor 144.

[0020] Fig. 4 shows a perspective view of an electric motor of the turbomachine 1. In particular, the electric motor is a PMSM motor and comprises a rotor 144 and a stator [0021] The stator 146 is a concentric cylinder that surrounds the rotor 144 and is arranged to be stationary with the casing 12. The stator 146 includes a plurality of electromagnets formed by respective ferromagnetic cores, or yokes, and electric coils wound around their respective cores or yokes. The cores or yokes are annularly disposed and extends toward the motor rotor 144. The cores or yokes may comprise stacked sheets of ferromagnetic metal.

[0022] The rotor 144 is coupled with the impeller 142 and is arranged to rotate relative to the stator 146. As such the rotor 144 is configured to rotate integrally with the respective impeller 146, for example at a controlled rotation speed.

[0023] As shown in Fig. 3 and 4 also the rotor 144 includes a plurality of electromagnets formed by respective ferromagnetic cores, or yokes, and electric coils wound around their respective cores or yokes. The cores or yokes are made of rare-earth material and the electric coils are made of copper.

[0024] . Therefore, the turbomachine described with reference to Fig. 1-4 includes PMSM motors which require permanent magnets in the rotor 144 with the result that turbomachines of this kind have a bulky construction as well as they may require a variable frequency drive (VFD) controller, such as a high voltage insulated gate bipolar transistor (HV-IGBT) module, in order to carefully control the startup torque and lower in-rush current, which is the amount of current drawn by the motor during startup.

[0025] For example, when a PMSM motor is started the motor speed is near zero, the electromagnetic force produced is low while the in-rush current may be high. A high in-rush current can cause motor or other electrical component damage and the sudden high torque production caused by severe rotor acceleration may also damage mechanical loads.

[0026] Moreover, the design of the PMSM motor may suffer of windage losses. This is because the presence of permanent magnets in the rotor 144 result in a rotor-stator system design that has a wide gap between the rotor 144 and stator 146. Windage losses refers to the losses sustained by the rotor-stator system due to the resistance of the fluid flowing within the gap to the rotation of the rotor 144.

[0027] Moreover, in the PMSM motor the permanent magnets of the rotor 144 are conventionally made from alloys of rare-earth elements which are heavy and expensive. As such turbomachines which comprise PMSM motor are also heavy and expensive.

[0028] The adoption of an SRM motor in place of the PMSM motor improves the overall efficiency of the turbomachine reducing windage losses, the problem of excessive in-rush current and increasing performance across a wider range of operating temperatures. Further, the adoption of an SRM motor allows to achieve a simpler yet compact and low-cost construction.

[0029] The present subject matter is thus directed to turbomachine 1 comprising one or more SRM motors.

[0030] Reference is now made to Fig. 5 which illustrates a perspective view of an axial cross-section in the plane XZ of a portion of turbomachine 1, according to a first embodiment of the present disclosure. The turbomachine 1 can be part of a turbomachinery plant of known type, such as petroleum refineries, oil production platforms, submarine systems, off-shore installation etc.

[0031] In the embodiment shown in Fig. 5 the turbomachine 1 comprises a casing 12 including a fluid inlet 122 and a fluid outlet 124 and one or more stages 14 sequentially arranged in the casing 12.

[0032] As described above with reference to Fig. 1, the fluid inlet 122 is in fluid communication with the fluid outlet 124 through a flow path 16 which extends from the fluid inlet 122 to the fluid outlet 124 through the one or more stages 14. As such the fluid flows in a generally axial direction through the turbomachine 1 from the inlet 122 towards the outlet 124 and across the one or more stages 14 of the turbomachine 1.

[0033] The turbomachine 1 can comprise a plurality of axial stages 14 arranged in sequence between the fluid inlet 122 and the fluid outlet 16. In the partial view of Fig. 5 there is only shown a single axial stage 14, but those skilled in the art will understand that a different number of stages 14 can be provided. Each stage is separated from the next stage by a stationary diaphragm 18, which is a stationary portion of the turbomachine 1 configured to accommodate the inner case internally and separate the different stages 14.

[0034] Each stage applies kinetic energy to compress or transport a fluid through the flow path 16 by means of a rotatable impeller 142. Each stage comprises the rotatable impeller 142 which can be driven into rotation by a respective motor. For example, the stages 14 may be organised in pair, such that each impeller 142 that is configured to rotate in one direction is always followed by a next impeller 142 that is configured to rotate in the opposite direction.

[0035] It shall be understood that in the context of the present description, that the plurality of stages 14 may alternatively be disposed radially, i.e. placed one radially inside the other, or in a mixed configuration with respect the direction of the flow path 16. For example, if the flow path 16 is radial, e.g. centrifugal, the electric motor of each centrifugal stage is arranged axially, in the sense that the motor stator(s) 146 and the motor rotor 144 are aligned along the axis of rotation of the turbomachine 1.

[0036] A more detailed view of a single stage 14 of the turbomachine 1 is shown in Fig. 6. The stage 14 comprises an impeller 142 and an electric motor coupled thereto. An enlarged view of a portion of the SRM motor of the turbomachine 1 is shown in Fig. 7.

[0037] As shown in Fig. 6, the impeller 142 is located at least in part within the flow path 16 to engage with the fluid for boosting the pressure of a fluid and/or for generating a fluid flow. During use the impeller can act like a flywheel in order to minimise torque ripple. The impeller is provided with respective impeller blades which may include a root portion, an airfoil portion and a tip portion. The blades are annularly arranged blades forming a monolithic ring that is coupled with the rotor 144.

[0038] The impeller 142 may be integrally built with the rotor 144 or built separately and affixed to the rotor 144. For example, the impeller 142 may be made of the same material of the rotor 144 or a different material.

[0039] The SRM motor comprises a stator 146 and a rotor 144. The stator 146 com- prises a plurality of electromagnets whereas the rotor 144 is integrally made of a magnetically permeable metal. As such, the rotor 144 does not require a plurality of electromagnets, but comprises solely a magnetically permeable metal that is fixed onto a radial bearing about which it rotates.

[0040] In the embodiment shown in Fig. 5-7, the stator 146 and the rotor 144 are arranged radially with respect to a rotation axis R of the electric motor. The stator 146 is configured to surround the rotor 144 and is arranged to be stationary with the casing 12.

[0041] The stator 146 includes a plurality of electromagnets formed by respective ferromagnetic cores, or yokes, and electric coils wound around their respective cores or yokes. The cores or yokes are annularly disposed and extends toward the motor rotor 144. The cores or yokes may comprise stacked sheets of ferromagnetic metal. The electric coils may be made of copper. In one embodiment, it is possible to replace copper windings with lighter aluminium windings achieving a lighter construction.

[0042] The rotor 144 is arranged to rotate relative to the stator 146. The stator 146 and the rotor 144 are arranged so as to form a gap between each other. The gap may be in fluidic communication with the flow path 16. The electric motor may comprise a radial bearing such that the rotor 144 is fixed onto the radial bearing about which it rotates. The radial bearing may be disposed within the gap. The rotor 144 is coupled with the impeller 142 and configured to rotate integrally with the respective impeller 146, for example by means of a controller at a controlled rotation speed which may vary e.g. between 0-100,000 RPM.

[0043] The SRM has a compact construction because the gap between the rotor 144 and the stator 146 may be reduced as compared to PMSM motors thus achieving less windage losses caused by the movement of the fluid within the gap.

[0044] During use the electric coils of the stator 146 can be energized to generate magnetic flux that pulls the rotor 144 along, generating torque. The electric coils can be powered without the requirement of a VFD, because the SRM motor is less affected by in rush currents, thereby optimizing efficiency across speeds. [0045] The turbomachine 1 may comprise a controller configured to individually control each electric motor of one or more stages 14 as a function of at least one parameter being selected from the group consisting of a rotational speed, a torque, a power, or a combination thereof.

[0046] The controller may comprise one or more processors. The controller may also comprise a memory and a communication module communicatively couplable with a server and/or a mobile terminal, such as a tablet, a cell phone, a laptop, or the like. The communication module may be configured to communicate with the mobile terminal and/or server, such as a cloud server, using wired or wireless technology in order to control the rotation of the motor and/or exchange data relative to the operation of the turbomachine 1. For example, the wireless technology may include WiFi, cellular technology, near field communications (NFC), Bluetooth, personal area networks (PANs), and the like. Wired technology may include proprietary cabling, RJ45 cabling, co-axial cables, fiber optic cables, and so on.

[0047] During use, the turbomachine 1 may be controlled by an operator, for example remotely through a mobile terminal, or be controlled automatically on the basis of a programmed instructions stored within a memory of the controller or the server.

[0048] Reference is now made to Fig. 8 which illustrates a perspective view of an axial cross-section in the plane XZ of a portion of turbomachine 1, according to a second embodiment of the present disclosure.

[0049] The turbomachine 1 shown in Fig. 8-10 differs from the turbomachine 1 of the first embodiment in that the stator 146 and the rotor 144 are arranged axially with respect to a rotation axis R of the electric motor.

[0050] In particular, as shown in Fig. 8 the stator 146 is placed opposite to the rotor 144 in the direction of the rotation axis R so as to form a sandwich structure with the rotor 144. In this way the stator 146 is no longer disposed at least in part within the exterior casing 3. In particular, the motor can be disposed within the stationary diaphragm 18. As such, the thickness of the exterior casing 3 can be further reduced achieving a more compact construction of the turbomachine 1 as well as savings in the material required for the casing 3. [0051] As better illustrated in Fig. 9 and 10, the stator 146 comprises a plate and the plurality of electromagnets are arranged on the surface of the plate, for example along a circumferential direction of the plate. The plurality of electromagnets may be formed by respective ferromagnetic cores, or yokes, and electric coils wound around their respective cores or yokes. The cores or yokes may comprise stacked sheets of ferromagnetic metal that extends toward the motor rotor 144 in order to induce an electromagnetic flux to the rotor 146 when powered. The electric coils can be made of copper or aluminium.

[0052] The stator 146 and the rotor 144 are arranged so as to form a gap between each other. The rotor 144 is arranged to rotate relative to the stator 146. The electric motor may comprise an axial bearing such that the rotor 144 is fixed onto the axial bearing about which it rotates. The axial bearing may be disposed within the gap.

[0053] As will be appreciated from Fig. 9 and 10, the gap between the stator 146 and the rotor 144 is isolated from the flow path 16. In particular, the impeller 142 comprises a flap-like portion 1422 that extends over the stationary diaphragm 18. The flaplike portion 1422 of the impeller 142 is configured to be fluid tight so as to isolate the gap between the stator 146 and the rotor 144 from the flow path 16. For example, the flap-like portion 1422 may be provided with one or more seal rings (not shown) that avoid the working fluid to enter inside the gap. This arrangement allows to minimize the windage losses caused by working fluid entering into the gap due to torturous path created by the impeller 142 blades during operation.

[0054] An advantage of the technical solutions of the present embodiments is to provide a turbomachine 1 which comprises at least one SRM motor. The SRM is a more robust, compact and fault tolerant motor than the PMSM, because it does not require rare earth elements for magnets, thus overcoming the limits of the PMSM motor. In particular, the gap between the rotor and stator can be reduced resulting in less windage losses.

[0055] Another advantage of the present technical solutions is that the absence of rotor windings and permanent magnets allows to achieve a simpler yet low-cost construction of the turbomachine with less hysteresis losses. Moreover, because of the absence of the permanent magnets the performance will be maintained across a wider range of operating temperatures of the turbomachine.

[0056] Another advantage of the present technical solutions is that the switched reluctance motor has a higher starting torque without the problem of excessive in-rush current, reducing machine start-up problem, and improving the general operation thereof.

[0057] While aspects of the invention have been described in terms of various specific embodiments, it will be apparent to those of ordinary skill in the art that many modifications, changes, and omissions are possible without departing form the spirit and scope of the claims. In addition, unless specified otherwise herein, the order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments.

[0058] Reference has been made in detail to the embodiments of the disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the disclosure, not limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. Reference throughout the specification to "one embodiment" or "an embodiment" or “some embodiments” means that the particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrase "in one embodiment" or "in an embodiment" or "in some embodiments" in various places throughout the specification is not necessarily referring to the same embodiment(s). Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

[0059] When elements of various embodiments are introduced, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

Claims

1. A turbomachine (1), comprising: a casing (12) comprising a fluid inlet (122) and a fluid outlet (124); one or more stages (14) sequentially arranged in the casing (12); and a flow path (16) that extends from the fluid inlet (122) to the fluid outlet (124) through the one or more stages (14); wherein each stage of the one or more stages comprises an impeller (142) and an electric motor, the impeller (142) being located at least in part within the flow path (16), the electric motor comprising a rotor (144) and a stator (146), wherein the rotor (144) is coupled with the impeller (142) and is configured to rotate the impeller (142), the stator (146) being arranged to be stationary with the casing (12); the turbomachine being characterized in that: the stator (146) comprises a plurality of electromagnets and the rotor (144) is made of a magnetically permeable metal.

2. The turbomachine of claim 1, wherein the stator (146) and the rotor (144) are arranged radially with respect to a rotation axis (R) of the electric motor such that the stator (146) is configured to surround the rotor (144).

3. The turbomachine of claim 2, wherein the stator (146) and the rotor (144) are arranged so as to form a gap between each other, the gap being in fluidic communication with the flow path (16).

4. The turbomachine of claim 2 or 3, wherein the electric motor comprises a radial bearing and the rotor (144) is fixed onto the radial bearing about which it rotates.

5. The turbomachine of claim 1, wherein the stator (146) and the rotor (144) are arranged axially with respect to a rotation axis (R) of the electric motor such that the stator (146) is placed opposite to the rotor (144) in the direction of the rotation axis (R) so as to form a sandwich structure with the rotor (144).

6. The turbomachine of claim 5, wherein the stator (146) and the rotor (144) are arranged so as to form a gap between each other, the gap being isolated from the flow path (16).

7. The turbomachine of claim 6, wherein the impeller (142) comprises a flap-like portion (1422) that extends over a stationary diaphragm (18) of the turbomachine (1), wherein the flap-like portion (1422) of the impeller (142) is configured to be fluid tight so as to isolate the gap between the stator (146) and the rotor (144) from the flow path (16).

8. The turbomachine of claim 6, wherein the flap-like portion (1422) comprises one or more seal rings.

9. The turbomachine of any one of claims 5-8, wherein the stator (146) comprises a plate and wherein the plurality of electromagnets are arranged on the plate along a circumferential direction of the plate.

10. The turbomachine of any one of claims 5-9, wherein the electric motor comprises an axial bearing and the rotor (144) is fixed onto the axial bearing about which it rotates.

11. The turbomachine (1) of any one of the preceding claims comprising a controller configured to individually control each electric motor of one or more stages (14) as a function of at least one parameter being selected from the group consisting of: a rotational speed, a torque, a power, or a combination thereof.

12. The turbomachine (1) of any one of the preceding claims, wherein each of the plurality of electromagnets comprises a magnetically permeable core with a plurality of electric windings wound around the magnetically permeable core.

13. The turbomachine (1) of any one of the preceding claims, wherein the impeller (142) is integrally built with the rotor (144).

14. The turbomachine (1) of any one of the preceding claims, wherein the impeller (142) is made of the same material of the rotor (144).

15. A turbomachinery plant comprising a turbomachine (1) as claimed in any one of the preceding claims.