INTEGRATED CENTRIFUGAL PUMP AND MOTOR

Description

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to electrically driven fluid pumps, and more particularly to electrically driven centrifugal pumps which require no shaft seals.

[0002] Centrifugal fluid pumps are well known in the hydraulic and pneumatic fields. They commonly consist of a motor to drive a shaft on which a fluid impeller is mounted. Generally, the fluid inlet port, or suction port, feeds fluid to the center, or hub, of the impeller. A number of impeller vanes generally project outward from the hub in spiral paths and are supported between shrouds which, together with the vanes, define pumping channels. The rotor is encased in a housing which channels the working fluid from the inlet port to the hub, or inducer, where it is inducted into the pumping channels between the vanes and shrouds. The centrifugal action of the impeller drives the working fluid outward to a diffuser at the periphery of the impeller disk where it enters a scroll shaped volute and, from there, is channelled to the discharge port of the pump.

[0003] The motor shaft, which supports the impeller, requires bearings which are sometimes lubricated by the working fluid, but, in many cases, they require separate lubrication due to incompatibility of the working fluid. In all cases, seals are required to prevent leakage of the working fluid around the impeller shaft where it enters the pump housing. After some time in service, the bearings may deteriorate to the point where they permit some radial displacement of the rotating shaft. This causes accelerated wear and deterioration of the shaft seal and results in leakage of the working fluid from the pump housing.

[0004] The foregoing illustrates limitations known to exist in present centrifugal pumps. Thus, it is apparent that it would be advantageous to provide an alternative directed to FR-A-591,315 discloses a balancing device for centrifugal pumps which comprises two balancing chambers formed on either side of the cheeks of an impeller and interconnected by a duct. If e.g. as a result of inequalities in the plays existing on either side of the impeller, different pressures become established in the balancing chambers. Fluid thus flows through the duct to restore the equilibrium of the pressures.

[0005] US-A-2,700,343 discloses a motor pump unit which is a centrifugal pump which has a housing having separate pumping chambers with separate fluid intakes and discharge ports. There is an impeller mounted for rotation in each chamber, each impeller having a hub section with at least one disc shaped shroud containing rotor coils to form an impeller-rotor unit. A plurality of pumping channels defined by a plurality of impeller blades of the impeller project outwardly from the hub section and are fixed to a face of the shroud. A stator co-operates with the rotor and the stator windings are isolated from the fluid being impelled.

[0006] According to the present invention, there is provided a centrifugal pump comprising:
   a housing having an internal chamber with inlet and discharge ports;
   an impeller supported in said chamber for rotation about an axis, the impeller having a hub section; at least one disc shaped shroud containing permanent magnets; a plurality of pumping channels defined by a plurality of impeller blades projecting outwardly from the hub section and fixed to a face of the shroud; and means for supplying fluid to the pumping channels, said means comprising at least one opening between the hub section and the shroud; characterised by one or more inducers in said opening, said inducers comprising pumping members which are separate from the impeller blades; and there being a recirculation passage adjacent the or each inducer.

[0007] For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:-

Figure 1 is a schematic sectional elevation view illustrating one embodiment of a centrifugal pump;

Figure 2 is a schematic sectional elevation view of another embodiment of the pump; and

Figure 3 is a fragmentary view along line 3-3 of the pump shown in Figure 1.

DETAILED DESCRIPTION

[0008] Fig. 1 is a schematic cross sectional view of one embodiment of the pump of the present invention, which is seen to be laterally symmetrical about the vertical center plane represented by the centerline of Fig. 1. The housing 10 has an inlet port 11 and a discharge port 12 which are connected by means of inducer assembly 18, impeller shrouds 15, rotating vaneless diffuser 24, and volute 13. The pump fluid enters at the inlet port 11; divides and passes into the two sides of the inducer assembly 18; passes between the two impeller shrouds 15 through pumping channels 55 (shown in Fig. 3) which are defined by the spaces between neighboring impeller blades 21 and the impeller shrouds 15, between which the impeller blades 21 are disposed; passes through the rotating vaneless diffuser 24; then passes through the volute 13 and into discharge port 12. Between diffuser 24 and volute 13 a small amount of the high pressure fluid feeds back through axial thrust balance passages 45. These narrow passages provide the gap necessary for rotation of the rotor shrouds 15 between the stators 14 and, by admission of the feedback fluid, provide a hydrodynamic balance to counteract any axial thrusts of the rotor 15 so that it remains centered between stators 14. Axial thrust balancing rings 16 are provided in the balance passage 45 either on the surface of the stator can 17 or on a projection of housing 10. By narrowing the axial gap between the impeller shrouds 15 and stator cans 17 or housing 10, these rings cause an increase of fluid pressure in the balance passage 45 which enhances the axial thrust balance performance.

[0009] The alternative provided for placement of the axial thrust balancing rings 16 is required because, in some cases, stators 14 will not be canned or encapsulated. In such cases, it is necessary to place the axial thrust balancing rings 16 on projections of housing 10. Each half of housing 10 has a toroidal recess 33 in which a stator 14 is secured. In addition, recirculation passages 20 are provided to assure smooth inducer action at off-design flow rates.

[0010] The rotor assembly which includes inducer assembly 18, shrouds 15, impeller blades 21, and rotating diffuser 24 is supported on journals provided on the outside of the tubular axial extensions of shrouds 15 in radial magnetic bearings 35 and auxiliary bearings 40. During operation, the rotor is supported by the radial magnetic bearings 35 which have a large enough clearance to provide non-contact bearing support to the rotor. Should the magnetic bearings 35 fail to support the rotor, auxiliary bearings 40 are provided for the ensuing emergency rundown of the rotor only, and they have a smaller clearance than do magnetic bearings 35.

[0011] Impeller shrouds 15 each contain a peripheral array of permanent magnets required for a rotor in a brushless DC motor when used in conjunction with stators 14 containing the windings and electrical connections required for operation as a motor. Because impeller shrouds 15 contain permanent magnets, and because shrouds 15 are supported in radial magnetic bearings 35 and auxiliary bearings 40, there is no need for any shaft to penetrate the housing 10 and, thus, no need for rotary shaft seals which can cause wear of the shaft and will eventually leak.

[0012] Fig. 2 illustrates another embodiment of the pump of the present invention. In this case the housing 10 is composed of several sections, and it has two inlets 11. Otherwise, in all other respects, the pumps are functionally identical. For this reason, numbering of the various components has been retained consistent with that used in Fig. 1.

[0013] Fig. 3 shows a fragmentary schematic sectional view of the rotor and housing along line 3-3 of Fig. 1. Vanes 21 are attached to shroud 15. Inducer assembly 18 feeds fluid to the impeller blades which pump it radially outward through pumping channels 55 defined by blades 21 and shrouds 15. Diffuser 24 is defined by that space between the two shrouds 15 radially outside that which is occupied by blades 21. Pressurized fluid from diffuser 24 is carried away through volute 13.

[0014] The particular design parameters for a given pumping application are determined by pressure and volume requirements, space constraints, working fluid properties, and desired orientation of inlet and discharge ports. These are the considerations that determine the diameter of the impeller shrouds 15, the spacing between the shrouds and consequently the width of the impeller blades 21, the size of diffuser 24 if needed, the size of inducer assembly 18, and the size and shape of the pump housing 10 and recirculation passages 20 which are provided to assure smooth inducer action at off-design flow rates. Stators 14 and impeller shrouds 15 are matched according to pumping power requirements. Stators 14 may or may not be encapsulated in cans 17, depending upon whether the working fluid is compatible with the stators.

[0015] This invention provides an integrated centrifugal pump and motor having the advantages of compactness, the ability to operate electronically at variable speeds, a shaftless rotor which requires no seals, non-contact radial bearing supports during operation, and hydrodynamic axial thrust balance for the rotor. These advantages are obtained when pumping either compressible or incompressible fluids.

Claims

1. A centrifugal pump comprising:
   a housing (10) having an internal chamber with inlet (11) and discharge (12) ports;
   an impeller supported in said chamber for rotation about an axis, the impeller having a hub section; at least one disc shaped shroud (15) containing permanent magnets; a plurality of pumping channels (55) defined by a plurality of impeller blades projecting outwardly from the hub section and fixed to a face of the shroud; and means for supplying fluid to the pumping channels, said means comprising at least one opening between the hub section and the shroud; characterised by one or more inducers (18) in said opening, said inducers comprising pumping members which are separate from the impeller blades; and there being a recirculation passage adjacent the or each inducer.

2. A centrifugal pump as claimed in claim 1, wherein said impeller includes a second disc shaped shroud (15), said impeller blades (21) being located between said first and second shrouds.

3. A centrifugal pump as claimed in claim 2, wherein said second disc shaped shroud (15) includes a plurality of permanent magnets and a stator coil (14) disposed adjacent said second shroud.

4. A centrifugal pump according to claim 3, wherein said first and second disc shaped shrouds (15) are supported from said hub section, and said impeller blades (21) are in a common plane between said first and second shrouds so as to rotate in a common plane normal to said axis; the stator coil being disposed adjacent said shrouds (15) so as to form a gap between the stator coil and the shroud for receiving a small quantity of pumped working fluid, and there being a means for axial hydrodynamic balancing of said impeller, the means comprising a ring (16) disposed in said gap for restricting the flow of the small quantity of pumped working fluid.

5. A centrifugal pump as claimed in claim 3 or 4, wherein said second shroud has a second central opening coaxial with the central opening in said first shroud and said stator coil has a further central opening therein, and second flow directing means for directing fluid flow from said inlet port to said pumping channels (55) through the openings in said second shroud and said stator coil.

6. A centrifugal pump as claimed in claim 5, wherein said first and second flow directing means include inducers (18) for inducing flow in one direction through the central opening in said first shroud and in the opposite direction through the central opening in said second shroud.

7. A centrifugal pump as claimed in claim 6, wherein said housing has first and second inlet ports and said first and second flow directing means comprise means for inducing fluid flow from said first and second inlet ports respectively, through the central openings in said first and second shrouds, respectively.

8. A centrifugal pump as claimed in claim 5, 6 or 7, wherein said second flow directing means comprises a volute (13), at least a portion of which is located within said internal chamber.

9. A centrifugal pump as claimed in claim 8, wherein said inlet and discharge ports, said volute and said pumping channels are located in a common plane.

10. A centrifugal pump as claimed in any one of claims 5 to 9, further comprising a second stator coil (14), wherein said first and second flow directing means include first and second flow channels located between said housing and said stator coils, respectively.

11. A centrifugal pump as claimed in any one of claims 3 to 10, wherein the or each stator coil is encapsulated to prevent contact with the fluid.

Ansprüche

1. Zentrifugalpumpe mit einem Gehäuse (10), das eine innere Kammer mit Einlaß- (11) und Auslaßöffnung (12) aufweist, mit einem Laufrad, das in der Kammer zur Rotation um eine Achse gelagert ist, wobei das Laufrad einen Nabenbereich hat; mit wenigstens einer scheibenförmigen Abschirmung (15), die Permanentmagnete enthält; mit einer Mehrzahl von Pumpenkanälen (55), die von einer Mehrzahl von Laufradschaufeln, die vom Nabenbereich nach außen ragen und auf einer Fläche der Abschirmung befestigt sind, definiert werden; und mit Einrichtungen zum Liefern von Fluid zu den Pumpenkanälen, wobei die Einrichtungen wenigstens eine Öffnung zwischen dem Nabenbereich und der Abschirmung aufweisen, gekennzeichnet durch einen oder mehrere, in der Öffnung angeordnete Einlaufkränze (18), wobei die Einlaufkränze Pumpenelemente aufweisen, die von den Laufradschaufeln getrennt sind, und wobei bei dem oder jedem Einlaufkranz ein Rezirkulationsdurchgang angeordnet ist.

2. Zentrifugalpumpe nach Anspruch 1, wobei das Laufrad eine zweite scheibenförmige Abschirmung (15) aufweist, wobei die Laufradschaufeln (21) zwischen der ersten und der zweiten Abschirmung angeordnet sind.

3. Zentrifugalpumpe nach Anspruch 2, wobei die zweite scheibenförmige Abschirmung (15) eine Mehrzahl von Permanentmagneten aufweist und wobei eine Statorwicklung (14) neben der zweiten Abschirmung angeordnet ist.

4. Zentrifugalpumpe nach Anspruch 3, wobei die erste und zweite scheibenförmige Abschirmung (15) von dem Nabenbereich getragen werden, und wobei die Laufradschaufeln (21) in einer gemeinsamen Ebene zwischen der ersten und der zweiten Abschirmung so liegen, daß sie in einer gemeinsamen Ebene normal zur Achse rotieren, wobei die Statorwicklung so neben den Abschirmungen (15) angeordnet ist, daß sie einen Spalt zwischen der Statorwicklung und der Abschirmung bildet, um eine geringe Menge von gepumptem Arbeitsfluid aufzunehmen, und mit einer Einrichtung zum axialen hydrodynamischen Ausgleichen des Laufrades, wobei die Einrichtungen einen Ring (16) aufweisen, der in dem Spalt zum Beschränken des Stroms der kleinen Menge gepumpten Arbeitsfluids angeordnet ist.

5. Zentrifugalpumpe nach Anspruch 3 oder 4, wobei die zweite Abschirmung eine zweite Zentralöffnung aufweist, die koaxial mit der Zentralöffnung in der ersten Abschirmung liegt, und wobei die Statorwicklung eine weitere darin angeordnete Zentralöffnung aufweist, und mit einer zweiten Strömungsleiteinrichtung zum Steuern der Fluidströmung von der Einlaßöffnung zu den Pumpenkanälen (55) durch die Öffnungen in der zweiten Abschirmung und der Statorwicklung.

6. Zentrifugalpumpe nach Anspruch 5, wobei die erste und zweite Strömungsleiteinrichtung Einlaufkränze (18) zum Einführen der Strömung in eine Richtung durch die Zentralöffnung in der ersten Abschirmung und in entgegengesetzte Richtung durch die Zentralöffnung in der zweiten Abschirmung aufweist.

7. Zentrifugalpumpe nach Anspruch 6, wobei das Gehäuse eine erste und eine zweite Einlaßöffnung hat, und wobei die erste und die zweite Strömungsleiteinrichtung Mittel zum Führen des Fluidstromes von der ersten und der zweiten Einlaßöffnung durch die Zentralöffnungen in der ersten und zweiten Abschirmung aufweisen.

8. Zentrifugalpumpe nach Anspruch 5, 6 oder 7, wobei die zweite Strömungsleiteinrichtung einen Spiraldiffusor (13) aufweist, wobei wenigstens ein Abschnitt davon innerhalb der inneren Kammer angeordnet ist.

9. Zentrifugalpumpe nach Anspruch 8, wobei die Einlaß- und Auslaßöffnung, der Spiraldiffusor und die Pumpenkanäle in einer gemeinsamen Ebene angeordnet sind.

10. Zentrifugalpumpe nach einem der Ansprüche 5 bis 9, die eine zweite Statorwicklung (14) aufweist, wobei die erste und zweite Strömungsleiteinrichtung erste und zweite Strömungskanäle aufweisen, die zwischen dem Gehäuse und den Statorwicklungen angeordnet sind.

11. Zentrifugalpumpe nach einem der Ansprüche 3 bis 10, wobei die oder jede Statorwicklung gekapselt ist, um einen Kontakt mit dem Fluid zu verhindern.

Revendications

1. Pompe centrifuge, comprenant :
- un boîtier (10) ayant une chambre interne avec des orifices d'entrée (11) et de refoulement (12);
- un rotor supporté dans ladite chambre en rotation autour d'un axe, le rotor ayant une section de moyeu; au moins un voile (15) en forme de disque, qui contient des aimants permanents ; une pluralité de canaux de pompage (55) définis par une pluralité de pales de rotor qui se projettent vers l'extérieur depuis la section de moyeu et sont fixées sur une face du voile ; et des moyens pour fournir du fluide vers les canaux de pompage, lesdits moyens comprenant au moins une ouverture entre la section de moyeu et le voile;
caractérisée en ce qu'elle comprend un ou plusieurs inducteurs (18) dans ladite ouverture, lesdits inducteurs comprenant des éléments de pompage qui sont séparés des pales de rotor; et en ce qu'il est prévu un passage de recirculation adjacent audit inducteur, ou à chaque inducteur.

2. Pompe centrifuge selon la revendication 1, dans laquelle ledit rotor comprend un second voile (15) en forme de disque, lesdites pales de rotor (21) étant situées entre ledit premier et ledit second voile.

3. Pompe centrifuge selon la revendication 2, dans laquelle ledit second voile (15) en forme de disque comprend une pluralité d'aimants permanents et un bobinage de stator (14) disposé en position adjacente audit second voile.

4. Pompe centrifuge selon la revendication 3, dans laquelle ledit premier et le second voile (15) en forme de disque sont supportés par ladite section de moyeu, et lesdites pales de rotor (21) sont dans un plan commun entre ledit premier et ledit second voile de manière à tourner dans un plan commun perpendiculaire audit axe ; le bobinage de stator étant disposé adjacent auxdits voiles (15) de manière à former un intervalle entre le bobinage de stator et le voile pour recevoir une petite quantité de fluide de travail pompé, et dans laquelle il est prévu des moyens pour équilibrer axialement ledit rotor de façon hydrodynamique, lesdits moyens comprenant un anneau (16) disposé dans ledit intervalle pour restreindre l'écoulement de la petite quantité de fluide de travail pompé.

5. Pompe centrifuge selon l'une ou l'autre des revendications 3 et 4, dans laquelle ledit second voile comporte une seconde ouverture centrale coaxiale à l'ouverture centrale dans ledit premier voile et ledit bobinage de stator comporte une autre ouverture centrale, et des seconds moyens de guidage d'écoulement pour diriger l'écoulement de fluide depuis ledit orifice d'entrée vers lesdits canaux de pompage (55) à travers les ouvertures dans ledit second voile et ledit bobinage de stator.

6. Pompe centrifuge selon la revendication 5, dans laquelle lesdits premier et second moyens de guidage d'écoulement comprennent des inducteurs (18) afin d'induire un écoulement dans une direction à travers l'ouverture centrale dans ledit premier voile et dans la direction opposée à travers l'ouverture centrale dans ledit second voile.

7. Pompe centrifuge selon la revendication 6, dans laquelle ledit boîtier comporte un premier et un second orifice d'entrée, et lesdits premier et second moyens de guidage d'écoulement comprennent des moyens pour induire un écoulement de fluide depuis lesdits premier et second orifice respectivement, à travers les ouvertures centrales dans ledit premier et ledit second voile, respectivement.

8. Pompe centrifuge selon l'une quelconque des revendications 5, 6 et 7, dans laquelle lesdits second moyens de guidage d'écoulement comprennent une volute (13), dont au moins une partie est située à l'intérieur de ladite chambre interne.

9. Pompe centrifuge selon la revendication 8, dans laquelle lesdits orifices d'entrée et de refoulement, ladite volute et lesdits canaux de pompage sont situés dans un plan commun.

10. Pompe centrifuge selon l'une quelconque des revendications 5 à 9, comprenant en outre un second bobinage de stator (14), dans laquelle lesdits premier et second moyens de guidage d'écoulement comprennent des premier et second canaux d'écoulement situés entre ledit boîtier et lesdits bobinages de stator respectivement.

11. Pompe centrifuge selon l'une quelconque des revendications 3 à 10, dans laquelle le ou chaque bobinage de stator est encapsulé afin d'empêcher un contact avec le fluide.

Drawing