Centrifugal pump with improved efficiency

Abstract

The invention relates to a centrifugal pump (1) comprising: • - a casing (2) comprising a first annular skirt (200), the first annular skirt comprising, in particular, a stator (201), in particular one or more electric coils (202) of the stator (201); • - an impeller (3) configured to be rotatable relative to the casing (2) about an axis of rotation (X) of the impeller (3), the impeller (3) comprising a tubular shaft (31) extending along the axis of rotation (X), the impeller (3) further comprising a second annular skirt (300), the second annular skirt (300) comprising, in particular, a rotor (301) that interacts with the stator (201), in particular the electric coils (202) of the stator (201), the impeller (3) being housed in the casing (2), characterised in that the first annular skirt (200) is at least partially positioned between the tubular shaft (31) and the second annular skirt (300).

Description

[0001] Description

[0002] Title: Improved Efficiency Centrifugal Pump

[0003] technical field

[0004] [1] The present invention relates to a centrifugal pump driven by an electric motor. The invention further relates to a vehicle cooling device comprising said pump, and to an electric or hybrid vehicle comprising said cooling device.

[0005] [2] The invention relates to the technical field of centrifugal pumps, and more particularly to centrifugal pumps whose electric motor is a radial or axial air gap motor. This type of pump is particularly suitable for vehicles, and more preferably for hybrid or electric vehicles.

[0006] Previous technique

[0007] [3] Currently, more and more vehicles are electric or hybrid vehicles, with batteries that are no longer used solely for starting or powering certain components, but also for propulsion. Consequently, these vehicles require a greater number of batteries for their proper operation.

[0008] [4] Each battery consists of individual cells, each cell producing both energy and heat. It is important, however, that the heat emitted by these cells is well dissipated, as excessive heat can cause irreversible damage to the cells, leading to a reduction or even a loss of their functionality. Therefore, efficient battery cooling is essential. This cooling is generally achieved by a heat transfer fluid circulating in a cooling circuit around and within the battery.

[0009] [5] The heat transfer fluid is used to regulate the temperature of the batteries and can be circulated by a centrifugal pump. The pump comprises at least one impeller installed in a casing, said impeller being driven by an electric motor to move the fluid. [6] Centrifugal pumps with an axial air gap are known, comprising an impeller mounted in a casing, in particular in a volute of the casing, and an electric motor driving said impeller and enabling the circulation of the fluid. The motor consists of a stator positioned in the pump casing and a rotor associated with said impeller. The casing also includes a suction port and a discharge port for the fluid, the main fluid circuit being arranged between said suction and discharge ports of the pump.Thus, the fluid circulates in a first circuit, called the main circuit, from the suction port and around the impeller blades, before reaching the discharge port. The fluid also circulates in a second circuit, called the return or leakage circuit, which flows from the impeller blades and then between the impeller and the casing before returning to the suction port. This leakage circuit negatively impacts the hydraulic efficiency of the pump.

[0010] [7] The invention aims to overcome at least one of the drawbacks of the aforementioned prior art. More specifically, the invention aims to reduce the leakage rate in the leakage circuit, so as to improve the pump torque at an equivalent discharge flow rate.

[0011] Summary

[0012] [8] To this end, the present invention proposes a centrifugal pump for a vehicle, in particular for an electric vehicle, adapted to circulate a heat transfer fluid and comprising:

[0013] - a casing comprising a first annular skirt,

[0014] - a paddle wheel, configured to be mobile in rotation relative to the casing around an axis of rotation of the paddle wheel, said paddle wheel comprising a tubular shaft extending along the axis of rotation, said paddle wheel also comprising a second annular skirt, said paddle wheel being housed in the casing, characterized in that the first annular skirt is at least partially positioned between the tubular shaft and the second annular skirt.

[0015] [9] Thus, the second annular skirt surrounds the first annular skirt, said first annular skirt surrounding the tubular shaft.

[0010] According to one embodiment of the invention, the second annular skirt, the first annular skirt and the tubular shaft are coaxial.

[0016]

[0011] According to an embodiment of the invention, said first annular skirt comprises a stator, in particular one or more electrical stator coils.

[0017]

[0012] According to an embodiment of the invention, said second annular skirt comprises a rotor interacting with the stator, in particular the electrical coils of the stator.

[0018]

[0013] According to an example of an embodiment of the invention, the housing includes a suction port and a discharge port for the fluid.

[0019]

[0014] The suction port allows the fluid to enter the pump, the discharge port allows it to be evacuated.

[0020]

[0015] According to an embodiment of the invention, the centrifugal pump includes a main fluid circulation circuit arranged between the suction port and the discharge port, which main circuit passes through a flow chamber formed in the tubular shaft.

[0021]

[0016] The main circuit passes through the paddle wheel.

[0022]

[0017] According to one embodiment of the invention, the centrifugal pump includes a leak circuit, separate from the main circuit, said leak circuit extending from the discharge port to the suction port, said leak circuit including a flow space located between an external wall of the impeller and an internal wall of the casing, the first and second annular skirts being configured to block, at least partially, the circulation of fluid within said leak circuit.

[0023]

[0018] The presence of the first and second annular skirts in the leak circuit partially blocks said circuit. The first and second annular skirts therefore limit the recirculation of the fluid in the leak circuit. Thus, the leakage rate of the fluid in the leak circuit is limited, and the fluid pressure losses are also increased due to the increased circuit length. As a result, the pump's efficiency is improved, while its energy consumption is reduced. The reduced energy consumption of the pump allows the batteries to operate for longer. This additional energy can be used by the vehicle, notably increasing its operating time.

[0019] According to one embodiment of the invention, the first and second annular skirts form baffles, configured to block, at least partially, the circulation of fluid within said leak circuit.

[0024]

[0020] According to an example of an embodiment of the invention, the leakage circuit includes an inlet port located at the discharge port and an outlet port located at the suction port, the fluid circulating within the leakage circuit circulating in particular around the periphery of the impeller.

[0025]

[0021] According to one embodiment of the invention, the centrifugal pump is driven by an electric motor and adapted to circulate a heat transfer fluid. The motor of the centrifugal pump is formed by the rotor, carried by the impeller and rotating about the axis, and by the stator, carried by the housing.

[0026]

[0022] According to one embodiment of the invention, the electric motor of the pump is a radial or axial air gap motor whose stator and rotor are installed in the leakage circuit, so that the air gap forms part of said leakage circuit.

[0027]

[0023] According to one embodiment of the invention, the rotor comprises at least one magnet, in particular a plurality of magnets.

[0028]

[0024] According to one embodiment of the invention, the second annular skirt includes notches to house each one magnet.

[0029]

[0025] According to one embodiment of the invention, the notches extend along arcs of a circle.

[0030]

[0026] According to one embodiment of the invention, the housing is provided with a first partition between the stator coil(s) and the second annular skirt.

[0031]

[0027] According to one embodiment of the invention, the housing is provided with a second partition between the stator coil(s) and the tubular shaft.

[0032]

[0028] In other words, the coils and the magnets are placed in different spaces.

[0033]

[0029] According to one embodiment of the invention, the housing comprises a first bearing, in particular the first skirt of the housing, in particular an internal surface of the first skirt of the housing, comprises said first bearing, said first bearing being configured to allow the rotation of the impeller within the housing, in particular said first bearing being at least partially in contact with the tubular shaft.

[0030] According to one embodiment of the invention, the first bearing surrounds the tubular shaft of said impeller.

[0034]

[0031] According to one embodiment of the invention, the first bearing is configured to block, at least partially, the leakage circuit between the housing and the tubular shaft. In particular, the clearance between the first bearing and the tubular shaft is configured so that the first bearing blocks, at least partially, the leakage circuit.

[0035]

[0032] The positioning of the first bearing in the leak circuit, in particular between the inlet and outlet ports of the leak circuit, makes it possible to reduce the leak flow rate and to reduce the recirculation of the fluid in the leak circuit, by making the circulation of the fluid more difficult.

[0036]

[0033] According to one embodiment of the invention, the casing includes a housing, the paddle wheel being housed in said housing.

[0037]

[0034] According to one embodiment of the invention, the housing of the casing comprises an annular cavity, said annular cavity being located, in a direction parallel to the axis of rotation, between the first skirt and the impeller, said annular cavity belonging to the leakage circuit, said annular cavity being configured to form at least one enlargement and one narrowing within said leakage circuit.

[0038]

[0035] The annular cavity is configured to create turbulence within the leak circuit, thereby partially blocking said circuit. The annular cavity thus limits the recirculation of fluid in the leak circuit. Consequently, the leakage rate of the fluid in the leak circuit is limited, and the fluid pressure losses are also increased due to the abrupt expansion and contraction of said leak circuit. As a result, the efficiency of the pump is improved, while its energy consumption is reduced. The reduced energy consumption of the pump allows the batteries to operate for longer periods. This additional energy can be used by the vehicle, notably to increase its operating time.

[0039]

[0036] According to one embodiment of the invention, the paddle wheel comprises paddles connecting a hub of the paddle wheel to an outer ring of the paddle wheel, the second annular skirt extending from said outer ring parallel to the axis of rotation of the paddle wheel.

[0037] According to one embodiment of the invention, the first annular skirt extends parallel to the axis of rotation of the paddle wheel.

[0040]

[0038] According to one embodiment of the invention, the housing includes a second bearing configured to allow the rotation of the impeller in the housing, the second bearing surrounding a rotation shaft of said impeller, in particular, the second bearing is at least partially in contact with the rotation shaft.

[0041]

[0039] The casing, the second bearing and the rotation shaft also keep the impeller in position in the pump, and allow efficient movement of the fluid within said pump.

[0042]

[0040] According to one embodiment of the invention, the casing forms a sealed enclosure around the impeller so as to keep the heat transfer fluid in the pump and prevent leaks.

[0043]

[0041] According to one embodiment of the invention, the casing includes a volute to accelerate the flow of heat transfer fluid.

[0044]

[0042] According to an example of an embodiment of the invention, the casing volute includes the discharge orifice.

[0045]

[0043] According to one embodiment of the invention, the discharge orifice is configured so that the fluid leaves the volute perpendicular to the axis of rotation of the impeller.

[0046]

[0044] According to one embodiment of the invention, the suction port of the casing opens onto the axis of rotation of the paddle wheel, in particular onto the tubular shaft of the paddle wheel, especially in the flow chamber of the tubular shaft.

[0047]

[0045] According to one embodiment of the invention, the housing includes at least one fluidic connection fitting configured for the connection of an additional conduit, the fluidic connection fitting including the suction port and / or the discharge port of the housing.

[0048]

[0046] According to an embodiment of the invention, the suction port and / or the fluid discharge port of the crankcase is formed at the top of a dome closing the housing of the crankcase.

[0049]

[0047] According to one embodiment of the invention, the pump electronics are placed in the housing.

[0050]

[0048] The invention also relates to a vehicle cooling device comprising a cooling circuit in which a heat transfer fluid circulates and a centrifugal pump configured to move said fluid in said circuit, the pump being in accordance with the invention.

[0051]

[0049] The vehicle is, for example, a motor vehicle, and may be a hybrid or electric vehicle. The cooling circuit of said vehicle serves to regulate the temperature of at least one vehicle battery, but may, alternatively, also serve to cool the engine, or to cool any system that can benefit from such cooling.

[0052]

[0050] The improvements to the pump also make the circulation of the fluid within the circuit more efficient and reduce the energy consumption required for the operation of said pump.

[0053]

[0051] The invention also relates to an electric or hybrid vehicle comprising at least one battery pack and a cooling device for said battery pack, which device includes a cooling circuit in which a heat transfer fluid circulates and a centrifugal pump configured to move said fluid in said circuit, the pump being in accordance with the invention.

[0054]

[0052] The electric or hybrid vehicle comprising a pump according to the invention has the capacity to consume less fuel thanks to the increased efficiency of the pump. The operating time of said vehicle is therefore also increased.

[0055]

[0053] The heat transfer fluid can be any fluid configured to allow thermal regulation, for example, of a vehicle engine or, more specifically, of a battery. This fluid can be any fluid capable of absorbing and transferring heat; it can also be a gas such as air, water, or a glycol compound.

[0056] Brief description of the drawings

[0057]

[0054] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0058]

[0055] [Fig. 1] is a diagram representing a cross-sectional view of a centrifugal pump according to the invention, configured to be installed in a cooling device.

[0059] Description of the implementation methods

[0060]

[0056] As used here, and unless otherwise indicated, the use of the ordinal adjectives "first," "second," etc., to describe an object simply indicates that different occurrences of similar objects are mentioned and does not imply that the objects thus described must be in any given sequence, whether in time, space, ranking, etc. "X and / or Y" means: X alone or Y alone or X+Y. Generally speaking, it will be appreciated that in the various accompanying drawings, the objects are drawn arbitrarily to facilitate their reading.

[0061]

[0057] Generally speaking, a vehicle, such as a motor vehicle, may include a cooling system. This cooling system includes a cooling circuit in which a heat transfer fluid circulates, set in motion by a centrifugal pump.

[0062]

[0058] The vehicle also includes at least one battery pack. In the case of hybrid and electric vehicles, several battery packs are necessary not only to enable the operation of the vehicle's components, but also to enable its movement. Each battery pack is composed of individual cells, each cell being capable of producing the energy required for the vehicle's operation. However, energy production is coupled with heat production, which can lead to a decrease in cell efficiency and / or deformation of the cells.

[0063]

[0059] Therefore, the cooling system provided in the vehicle can be designed for at least the battery pack(s) so as to regulate their temperature. This cooling system includes the cooling circuit in which the heat transfer fluid circulates, and is configured to regulate the temperature of the battery pack cells around which the fluid circulates. This heat transfer fluid is known to those skilled in the art and can be, for example, air, water, or a dielectric fluid. The movement of such a fluid in the cooling circuit is achieved by a centrifugal pump. This pump is described in more detail in Figure 1.

[0064]

[0060] Figure 1 shows a cross-sectional view of the centrifugal pump 1 adapted to circulate a heat transfer fluid according to the invention.

[0065]

[0061] The centrifugal pump 1 according to the invention comprises:

[0066] - a casing 2 comprising a first annular skirt 200,

[0067] - a paddle wheel 3, configured to be movable in rotation relative to the casing 2 around an axis of rotation X of the paddle wheel 3, said paddle wheel 3 comprising a tubular shaft 31 extending along the axis of rotation X, said paddle wheel 3 also comprising a second annular skirt 300, said paddle wheel 3 being housed in the casing 2.

[0068]

[0062] The first annular skirt 200 is at least partially positioned between the tubular shaft 31 and the second annular skirt 300.

[0069]

[0063] Thus, the second annular skirt 300 surrounds the first annular skirt 200, said first annular skirt 200 surrounding the tubular shaft 31. In particular, the second annular skirt 300, the first annular skirt 200 and the tubular shaft 31 are coaxial.

[0070]

[0064] The centrifugal pump 1 is driven by an electric motor and adapted to circulate a heat transfer fluid. The motor of the centrifugal pump 1 consists of a rotor 301 and a stator 201.

[0071]

[0065] The first annular skirt 200 includes the stator 201, in particular one or more electrical coils 202 of the stator 201.

[0072]

[0066] The second annular skirt 300 includes the rotor 301 interacting with the stator 201, in particular the electrical coils 202 of the stator 201.

[0073]

[0067] The rotor 301 is carried by the blade wheel 3 and is mobile in rotation around the X axis, the stator 201 being carried by the casing 2.

[0074]

[0068] The housing 2 includes a suction port 21 and a discharge port 22 for the fluid.

[0075]

[0069] The suction port 21 allows the fluid to enter the pump 1, the discharge port 22 allows its evacuation.

[0076]

[0070] The centrifugal pump 1 includes a main fluid circulation circuit 41 arranged between the suction port 21 and the discharge port 22, which main circuit 41 passes through a flow chamber 310 formed in the tubular shaft 31. The main circuit 41 passes through the impeller 3.

[0077]

[0071] The centrifugal pump 1 also includes a leak circuit 42, separate from the main circuit 41, said leak circuit 42 extending from the discharge port 22 to the suction port 21, said leak circuit 42 comprising a flow space located between an outer wall of the impeller 3 and an inner wall of the casing 2. The first and second annular skirts 200, 300 are configured to block, at least partially, the circulation of fluid within said leak circuit 42.

[0078]

[0072] The presence of the first and second annular skirts 200, 300 in the leakage circuit 42 partially blocks said circuit. The first and second annular skirts 200, 300 therefore limit the recirculation of the fluid in the leakage circuit 42. Thus, the leakage rate of the fluid in the leakage circuit 42 is limited, and the fluid pressure losses are also increased due to the increased circuit length. As a result, the efficiency of the pump 1 is improved, while reducing its energy consumption. The reduced energy consumption of the pump 1 allows the batteries to operate for longer periods. This additional energy can be used by the vehicle, notably to increase its operating time.

[0079]

[0073] The first and second annular skirts 200, 300 form baffles, configured to block, at least partially, the circulation of fluid within said leakage circuit 42.

[0080]

[0074] In particular, the leakage circuit 42 includes an inlet port 421 located at the discharge port 22 and an outlet port 422 located at the suction port 21. The fluid circulating within the leakage circuit 42 thus circulates around the periphery of the impeller 3.

[0081]

[0075] The electric motor of the pump 1 is a radial or axial air gap motor. The stator 201 and rotor 301 are installed in the leakage circuit 42, so that the air gap of the pump 1 forms part of said leakage circuit 42.

[0082]

[0076] The rotor 301 of the pump 1 comprises at least one magnet 302, in particular a plurality of magnets 302.

[0083]

[0077] According to an example of an embodiment of the invention, not shown, the second annular skirt 300 includes notches to house each a magnet 302.

[0084]

[0078] According to this embodiment of the invention, the notches extend along arcs of circles formed in the second annular skirt 300.

[0079] The housing 3 is provided with a first partition 24 between the stator coil(s) 202 201 and the second annular skirt 300. The housing 2 is also provided with a second partition 25 between the stator coil(s) 202 201 and the tubular shaft 31.

[0085]

[0080] In other words, the coils 202 and the magnets 302 are placed in different spaces.

[0086]

[0081] The housing 2 includes a first bearing 26, in particular the first skirt 200 of the housing 2, in particular an internal surface of the first skirt 200 of the housing 2, includes said first bearing 26, said first bearing 26 being configured to permit the rotation of the impeller 3 in the housing 2.

[0087]

[0082] The first bearing 26 surrounds the tubular shaft 31 of the paddle wheel 3. In particular, the first bearing 26 is at least partially in contact with the tubular shaft 31.

[0088]

[0083] The first bearing 26 is configured to block, at least partially, the leakage circuit 42, between the housing 2 and the tubular shaft 31.

[0089]

[0084] The positioning of the first bearing 26 in the leakage circuit 42, in particular between the inlet port 421 and the outlet port 422 of the leakage circuit 42, makes it possible to reduce the leakage flow and to reduce the recirculation of the fluid in the leakage circuit 42, by making the circulation of the fluid more difficult.

[0090]

[0085] The housing 2 includes a housing, the impeller 3 being housed in said housing. The housing of the housing 2 includes an annular cavity 28, said annular cavity 28 being located, in a direction parallel to the axis of rotation X, between the first skirt 200 and the impeller 3, said annular cavity 28 belonging to the leakage circuit 42. Said annular cavity 28 is configured to form at least one expansion and one contraction within said leakage circuit 42.

[0091]

[0086] The annular cavity 28 is configured to create turbulence within the leak circuit 42, thereby partially blocking said circuit. The annular cavity 28 thus limits the recirculation of the fluid in the leak circuit 42. Consequently, the leakage rate of the fluid in the leak circuit 42 is limited, and the fluid pressure losses are also increased due to the abrupt expansion and contraction of said leak circuit 42. As a result, the efficiency of the pump 1 is improved, while its energy consumption is reduced. The reduced energy consumption of the pump 1 allows the batteries to operate for longer periods. This additional energy can be used by the vehicle, notably to increase its operating time.

[0092]

[0087] The paddle wheel 3 includes paddles 33 connecting a hub of the paddle wheel 3 to an outer ring 34 of the paddle wheel 3, the second annular skirt 300 extending from said outer ring 34, parallel to the axis of rotation X of the paddle wheel 3.

[0093]

[0088] The paddle wheel 3 is therefore contained within a fictitious cylinder, of circular cross-section, centered on the axis of rotation X, the second annular skirt 300 and the outer ring 34 fitting within said fictitious cylinder. In particular, the second annular skirt 300 and the outer ring 34 form at least partially said fictitious cylinder.

[0094]

[0089] The first annular skirt 200 also extends parallel to the axis of rotation X of the paddle wheel 3.

[0095]

[0090] The housing 2 includes a second bearing 27 configured to allow the rotation of the impeller 3 in the housing 2, the second bearing 27 surrounding a rotation shaft 32 of said impeller 3. The second bearing 27 is at least partially in contact with the rotation shaft 32.

[0096]

[0091] The casing 2, the second bearing 27 and the rotation shaft 32 also allow the impeller 3 to be kept in position in the pump 1, and allow efficient movement of the fluid within said pump 1.

[0097]

[0092] The casing 2 forms a sealed envelope around the impeller 3 so as to keep the heat transfer fluid in the pump 1 and prevent leaks.

[0098]

[0093] The housing 2 includes a volute 23 to accelerate the flow of heat transfer fluid. The volute 23 of the housing 2 includes the discharge port 22, configured so that the fluid leaves the volute 23 perpendicular to the axis of rotation X of the impeller 3.

[0099]

[0094] The suction port 21 of the housing 2 opens onto the axis of rotation X of the impeller 3, in particular onto the tubular shaft 31 of the impeller 3, notably into the flow chamber 310 of the tubular shaft 31.

[0095] The housing 2 includes at least one fluid connection fitting 29 configured for the connection of an additional conduit, the fluid connection fitting 29 including the suction port 21 and / or the discharge port 22 of the housing 2.

[0100]

[0096] The suction port 21 and / or the discharge port 22 of the fluid from the housing 2 is formed at the top of a dome closing the housing of the housing 2.

[0101]

[0097] An electronic unit of the pump 1 is placed in the housing 2.

[0102]

[0098] The invention also relates to a vehicle cooling device comprising a cooling circuit in which a heat transfer fluid circulates and a centrifugal pump 1 configured to move said fluid in said circuit, the pump 1 being in accordance with the invention.

[0103]

[0099] The vehicle is, for example, a motor vehicle, and may be a hybrid or electric vehicle. The cooling circuit of said vehicle serves for the thermal regulation of at least one vehicle battery, but may, alternatively, also serve for the cooling of the engine, or for the cooling of any system that can benefit from such cooling.

[0104]

[0100] The improvements to pump 1 also make the circulation of the fluid within the circuit more efficient and reduce the energy consumption required for the operation of said pump.

[0105]

[0101] The heat transfer fluid can be any fluid configured to allow thermal regulation, for example, of a vehicle engine or, more specifically, of a battery. This fluid can be any fluid capable of absorbing and transferring heat; it can also be a gas such as air, water, or a glycol compound.

Claims

Demands

1. A centrifugal pump (1) for a vehicle, in particular for an electric vehicle, adapted for circulating a heat transfer fluid and comprising: - a casing (2) comprising a first annular skirt (200), - a paddle wheel (3), configured to be mobile in rotation relative to the housing (2) around an axis of rotation (X) of the paddle wheel (3), said paddle wheel (3) comprising a tubular shaft (31) extending along the axis of rotation (X), said paddle wheel (3) also comprising a second annular skirt (300), said paddle wheel (3) being housed in the housing (2), characterized in that the first annular skirt (200) is at least partially positioned between the tubular shaft (31) and the second annular skirt (300).

2. Centrifugal pump (1) according to the preceding claim in which said first annular skirt (200) comprises a stator (201), in particular one or more electrical coils (202) of the stator (201).

3. Centrifugal pump (1) according to any one of the preceding claims wherein said second annular skirt (300) comprises a rotor (301).

4. A centrifugal pump (1) according to any one of the preceding claims, wherein the casing (2) comprises a fluid suction port (21) and a fluid discharge port (22), the centrifugal pump (1) comprising: - a main fluid circulation circuit (41) arranged between the suction port (21) and the discharge port (22), which main circuit (41) passes through a flow chamber (310) formed in the tubular shaft (31), - a leak circuit (42), separate from the main circuit (41), said leak circuit (42) extending from the discharge port (22) to the suction port (21), said leak circuit (42) comprising a flow space situated between an external wall of the impeller (3) and an internal wall of the casing (2), the first and second annular skirts (200, 300) being configured to block, at least partially, the circulation of fluid within said leak circuit (42).

5. Centrifugal pump (1) according to the preceding claim, in combination with claims 2 and 3, said pump being driven by an electric motor formed by the rotor (301), carried by the impeller (3) and movable in rotation about the axis (X), and by the stator (201), said stator (201) and rotor (301) being installed in the leakage circuit (42), so that the air gap forms a part of said leakage circuit (42).

6. Centrifugal pump (1) according to any one of the preceding claims, in combination with claim 4, wherein the casing (2) comprises a housing, the impeller (3) being housed in said housing, said housing comprising an annular cavity (28), said annular cavity (28) being located, in a direction parallel to the axis of rotation (X), between the first skirt (200) and the impeller (3), said annular cavity (28) belonging to the leakage circuit (42), said annular cavity (28) being configured to form at least one enlargement and one constriction within said leakage circuit (42).

7. Centrifugal pump (1) according to any one of the preceding claims wherein the casing (2) comprises a first bearing (26), said first bearing (26) being configured to permit rotation of the impeller (3) in the casing (2), in particular said first bearing (26) being at least partially in contact with the tubular shaft (31).

8. Centrifugal pump (1) according to any one of the preceding claims in which the impeller (3) comprises vanes (33) connecting a hub of the impeller (3) to an outer ring (34) of the impeller (3), the second annular skirt (300) extending from said outer ring (34) parallel to the axis of rotation (X) of the impeller (3).

9. Centrifugal pump (1) according to any one of the preceding claims wherein the casing (2) comprises a second bearing (27) configured to permit rotation of the impeller (3) in the casing (2), the second bearing (27) surrounding a rotation shaft (32) of said impeller (3), in particular the first bearing (27) being at least partially in contact with the rotation shaft (32).

10. Vehicle cooling device comprising a cooling circuit in which a heat transfer fluid circulates and a centrifugal pump (1) configured to move said fluid in said circuit, characterized in that the pump (1) conforms to one of the preceding claims.

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