Self-priming pump

Abstract

The invention relates to a pump comprising a pump impeller (5) configured so that, during operation, the axis of the pump impeller (5) is vertical with an impeller inlet (10) disposed above an impeller outlet (11), the pump comprising a toroidal liquid reservoir (1) around the pump impeller (5) and a connection means (8) for connecting the liquid reservoir (1) to the pump impeller (5), at a connection point (9). The connection point (9) is positioned below the impeller inlet (10) so as to form a siphon, and the fluid passage cross-section (15) in the connection means (8) increases in the direction of circulation of the liquid in the pump. The invention also relates to a turbogenerator and a closed circuit comprising such a pump, as well as to the use of the closed circuit in a vehicle.

Description

Technical field

[0001] The invention relates to the field of pumps, in particular pumps used in Rankine type circuits (known as ORC circuits for “Organic Rankine Cycle”) and more particularly for Rankine circuits in heavy, light or utility vehicles. Prior art

[0002] For the application of ORC circuits to vehicles, and taking into account the pressure and temperature conditions upstream and downstream of the circulation pump, the sizing of this pump leads to objects of relatively very small size (typically diameters between 5 and 100 millimeters, preferably 5 to 50 mm) taking into account the high rotation speed (generally greater than 10,000 revolutions per minute) to produce the pressure gain necessary for the system, with a nominal flow rate of up to 0.5 kg / s and a relatively large pressure gain, between 1 and 5 bar (1 bar = 0.1 MPa), preferably 1.5 to 3 bar.Under these conditions, the pump is subject to a very high risk of cavitation if the pressure at the pump inlet is close to the vaporization pressure of the heat transfer fluid, which is generally the case for an ORC circuit for which the temperature at the pump inlet can be high, typically above 30 °C.

[0003] Indeed, the combination of the triplet of values ​​(flow rate, rotation speed, pressure gain), combined with a strong space constraint, can generate local overspeeds near the leading edge of the pump blades, leading to a drop in fluid pressure that can reach the vaporization pressure. This then produces the phenomenon of cavitation (vaporization of the liquid) which, if significant, generates noise, erosion of the machine blades, a drop in performance and hydraulic instabilities in the circuit.

[0004] In addition, the vehicle architecture often requires the pump to be placed in a higher position than the ORC circuit heat transfer fluid reservoir, which creates a risk of the pump losing its prime when the vehicle is stationary.

[0005] Due to the architecture of light vehicle engines and the desire to position the expansion machine at the highest point of the engine, the turbopump is often placed at the same height as the ORC circuit reservoir, or even above it. Thus, the pump load, or available NPSH (Net Positive Suction Head) is insufficient to guarantee operation of the pump without risk of cavitation and generally does not allow good priming of the pump.

[0006] Under these conditions, it is necessary to design a self-priming pump that minimizes the risk of cavitation, while ensuring the pressure gain necessary for the proper functioning of the ORC cycle as a whole.

[0007] Patent application CN110469542A relates to a feed pump that includes a simple recirculation loop with a restriction at the pump outlet, which allows the fluid pressure at the impeller inlet to be increased locally and prevents the formation of cavitation pockets. However, this system does not allow the pump to be self-primed, particularly if the pump is positioned along a vertical axis.

[0008] Applications CN110657099A and CN207795594U are also known, which relate to dual-inlet pumps comprising both a liquid reservoir placed on the upper part and a recirculation loop. The upper reservoir allows the pump to be primed when necessary, while the recirculation loop, as with patent CN110469542A, allows the pressure at the pump inlet to be increased locally to prevent the formation of cavitation pockets. However, this type of dual-inlet pump is not applicable to vehicles because they are bulky. Furthermore, recirculation loops can disrupt the flow at the inlet of the pump wheel, which can lead to a loss of efficiency.

[0009] Application CN208858581U is substantially similar to previous applications, this time with a centrifugal pump placed in a tank filled with liquid. The main inlet pipe is in communication with an auxiliary pipe which allows fluid to be injected from a tank up to the level of the inlet of the inlet pipe. The tank itself is pressurized from the fluid coming from the pump discharge.

[0010] Finally, document JP H02 78790 A discloses a pump according to the preamble of claim 1.

[0011] The object of the invention is to obtain a very compact, self-priming pump which limits the risk of cavitation, in particular so that it can be used in vehicle ORC circuits.

[0012] The use of this specific pump in an ORC circuit also helps to reduce CO2 emissions from road transport.

[0013] It also allows vehicles to be electrified since part of the heat recovered in the ORC cycle can be used to power an electric machine.

[0014] To address these challenges, the invention relates to a pump according to claim 1 comprising a pump impeller, the pump impeller comprising an impeller inlet and an impeller outlet. The pump impeller is configured such that in operation, the axis of the pump impeller is vertical with the impeller inlet disposed above the impeller outlet. The pump comprises a toroidal liquid reservoir positioned around the pump impeller, the axis of symmetry of the liquid reservoir being the vertical axis of the pump impeller. In other words, the liquid reservoir is coaxial with the pump impeller and surrounds the pump impeller. The pump also comprises a connection means for connecting the liquid reservoir to the pump impeller, at a connection point located in a lower portion of the liquid reservoir.In addition, the connection means between the liquid reservoir and the impeller inlet forms a siphon, thus improving the self-priming capabilities of the pump. Thus, the connection point is located below the impeller inlet. In addition, the fluid passage section in the connection means increases in the direction of circulation of the liquid in the pump from the lower part of the toric liquid reservoir towards the pump impeller inlet, so as to reduce the circulation speed of the fluid and thus increase the pressure, which contributes to limiting the risks of cavitation. The flow vein at the outlet of the pump is radially centrifugal, then axially ascending in such a way as to form an annular reservoir whose axis of revolution is the axis of rotation of the pump. The annular outlet reservoir thus encompasses the entire pump, the upstream toric reservoir and the connection means between the toric reservoir and the inlet of the pump impeller.

[0015] An implementation of the invention also relates to a turbine generator comprising a turbine and a pump as described with an electrical machine connected to the pump wheel and positioned above the pump wheel. The turbine is positioned above the pump wheel and connected to the electrical machine. Preferably, the electrical machine is positioned between the turbine and the pump wheel.

[0016] Another implementation of the invention also relates to a closed circuit operating according to a Rankine cycle, the closed circuit comprising a heat exchanger for evaporating a fluid, an expansion means for expanding the fluid, a condenser for liquefying the fluid, and a pump as described.

[0017] The invention also relates to the use according to claim 13 of the closed circuit as described in a vehicle comprising an internal combustion engine, whether heavy, light or utility, for which exhaust gases from the internal combustion engine and / or a second cooling fluid from the internal combustion engine and / or a third fluid from a burnt gas recirculation circuit (called EGR for "Exhaust Gas Recirculation" in English) of the internal combustion engine are sent into the heat exchanger to vaporize the fluid from the closed circuit. Summary of the invention

[0018] The invention relates to a pump comprising a pump impeller, the pump impeller comprising an impeller inlet and an impeller outlet, the pump impeller being configured such that in operation the axis of the pump impeller is vertical with the impeller inlet arranged above the impeller outlet, the pump comprising an O-ring liquid reservoir positioned around the pump impeller and connection means for connecting the liquid reservoir to said pump impeller, at a connection point located in a lower part of the liquid reservoir, the axis of the liquid reservoir being the vertical axis of the pump impeller. In addition, the connection point is positioned below said impeller inlet so as to form a siphon, and the passage section of the fluid in the connection means increases in the direction of circulation of the liquid in the pump from said lower part of the O-ring liquid reservoir towards said impeller inlet.

[0019] Preferably, the connecting means has a shape of revolution around the vertical axis of the pump wheel.

[0020] According to one implementation of the invention, the pump comprises a movable hub with a vertical axis, the pump wheel being fixed to the movable hub.

[0021] Advantageously, the pump comprises a fixed hub mounted on the movable hub and the pump comprises vertical vanes mounted on the fixed hub and extending radially relative to the fixed hub.

[0022] Preferably, the number of vertical fins is between 4 and 15.

[0023] According to one configuration of the invention, the pump comprises an inlet pipe and an outlet pipe, the inlet pipe being connected to the upper part of the liquid reservoir, the outlet pipe being connected to the impeller outlet.

[0024] Preferably, the outlet conduit comprises a vertical portion, the vertical portion of the outlet conduit being positioned above the level of the inlet conduit.

[0025] According to an advantageous implementation of the invention, the pump comprises an electric machine positioned on the axis of the pump wheel, the electric machine being connected to the pump wheel.

[0026] An implementation of the invention also relates to a turbogenerator comprising a turbine and a pump as described, the turbine being positioned above the pump wheel, preferably the electrical machine being positioned between the turbine and the pump wheel.

[0027] An implementation of the invention also relates to a closed circuit operating according to a Rankine cycle, the closed circuit comprising a heat exchanger for evaporating a fluid, an expansion means for expanding the fluid, a condenser for liquefying the fluid, and a pump as described.

[0028] An implementation of the invention further relates to a closed circuit operating according to a Rankine cycle, the closed circuit comprising a heat exchanger for evaporating a fluid, a turbine for expanding the fluid, the turbine being connected to an electrical machine, a condenser for liquefying the fluid, and a pump. In addition, the pump, the turbine and the electrical machine form a turbogenerator as described above.

[0029] Preferably, the condenser is located below the pump.

[0030] Furthermore, the invention also relates to the use of the closed circuit as described above in a light, heavy or utility vehicle comprising an internal combustion engine for which exhaust gases from the internal combustion engine and / or a second cooling fluid from the internal combustion engine and / or a third fluid from an EGR circuit of the internal combustion engine are sent into the heat exchanger to vaporize the fluid from the closed circuit. List of figures

[0031] Other characteristics and advantages of the pump, of the closed circuit and / or their use in a vehicle according to the invention will appear on reading the following description of non-limiting examples of embodiments, with reference to the figures appended and described below. There figure 1 represents a sectional view in the plane (X, Z) of a pump according to the invention. The figure 2represents a sectional view in the (X, Y) plane of the pump of the figure 1 according to the invention. The figure 3 represents a perspective view of the pump of the figures 1 And 2 according to the invention. The figure 4 represents a turbogenerator comprising a pump according to the invention. The Figure 5 represents a closed circuit operating according to a Rankine cycle with a pump according to the invention. Description of the embodiments

[0032] The terms "vertical", "above", "below", "lower" and "upper" are understood, within the meaning of the invention, in relation to the pump in the operating position, in this case the pump has a vertical axis.

[0033] The present invention relates to a pump comprising a pump impeller and the pump impeller comprises an impeller inlet and an impeller outlet. The pump impeller is configured such that in operation, the axis of rotation of the pump impeller is vertical with the impeller inlet disposed above the impeller outlet, so as to facilitate the flow of fluid to the pump and thus facilitate priming. Thus, gravity applied to the liquid facilitates starting of the pump.

[0034] The pump further comprises a toroidal liquid reservoir (in other words, the liquid reservoir forms a torus) positioned around the pump wheel, the axis of symmetry of the liquid reservoir being the vertical axis of the pump wheel. In other words, the toroidal liquid reservoir is a volume of revolution whose axis is coaxial with the pump wheel and it surrounds the pump wheel. This configuration makes it possible to obtain a compact system. The toroidal liquid reservoir surrounding the pump wheel also allows the installation of a possible electrical machine, above the pump wheel, without increasing the size of the system. The toroidal liquid reservoir makes it possible to maintain a sufficient liquid reserve at start-up until the system operates in steady state. Indeed, at the time of start-up, the liquid level in the reservoir will drop to the permanent state.Thus, the volume of the toroidal liquid reservoir can be designed to provide sufficient liquid volume for the system in which the pump is installed to reach a permanent steady state.

[0035] In addition, the pump comprises a connection means for connecting the liquid reservoir to the inlet of the pump impeller, at a connection junction located in a lower part of the liquid reservoir. This connection means is a vein of revolution whose axis is coaxial with the axis of revolution of the toroidal reservoir. This connection means makes it possible to convey the liquid from the toroidal liquid reservoir to the inlet of the pump impeller. Furthermore, the connection junction (or connection point) is positioned below the inlet of the impeller so as to form a siphon. The siphon effect makes it possible to improve the self-priming capabilities of the pump and, moreover, this configuration makes it possible to reduce the vertical height of the pump, which is advantageous when one wants to mount this pump on an ORC circuit of a vehicle.In addition, the fluid passage section in the connection means increases in the direction of circulation of the liquid in the pump from the lower part of the toric liquid reservoir to the pump wheel inlet, so as to reduce the speed of the heat transfer fluid, and therefore to increase the pressure of the fluid, which makes it possible to limit the risks of cavitation.

[0036] Thus, the pump according to the invention does not require a recirculation loop to facilitate self-priming of the pump. It therefore differs from prior art solutions.

[0037] According to the invention, the pump may be an axial, mixed, centrifugal or radial pump.

[0038] Preferably, the connecting means may have a shape of revolution around the vertical axis of the pump wheel. In other words, the connecting means completely surrounds the pump wheel, it is coaxial with the pump wheel and it is positioned between the pump wheel and the toroidal liquid reservoir. Such a shape of the connecting means makes it possible to increase the liquid passage section and further reduce the circulation speeds.

[0039] According to one implementation of the invention, the pump may comprise a movable hub with a vertical axis, the pump wheel being positioned on the movable hub. Thus, the movable hub (rotatable) may be driven in rotation by an axle, itself driven in rotation by an electric motor or any equivalent means. Thus, the rotation of the movable hub drives the pump wheel, fixed to the movable hub.

[0040] Advantageously, the pump may comprise fixed vertical vanes mounted on a fixed hub, itself mounted on the movable hub, the vertical vanes being positioned before the inlet of the pump wheel and extending radially relative to the fixed hub. These vanes make it possible to significantly reduce the tangential velocity of the liquid before the liquid reaches the pump wheel. By reducing the tangential velocity, the total velocity of the liquid is reduced. Preferably, the vanes are positioned above the pump wheel, on the fixed hub, before the inlet of the pump wheel. Rotation of the movable hub does not cause rotation of the fixed hub. To achieve this, means known to those skilled in the art may be used, such as bearings or ball bearings.

[0041] Preferably, the number of fixed vertical fins can be between 4 and 15, which allows a good compromise between the reduction of the tangential velocity of the liquid and the reduction of the passage section. Indeed, increasing the number of fins would tend to significantly reduce the passage section due to the thickness of the fins and thus to increase the flow velocity (component of the velocity contained in the section plane of the figure 1 ) of the fluid arriving at the pump wheel.

[0042] According to one configuration of the invention, the pump may comprise an inlet pipe and an outlet pipe, the inlet pipe being connected to the upper part of the toroidal liquid reservoir, the outlet pipe being connected to the impeller outlet. As a result, the pump can be easily implemented in a circuit.

[0043] Preferably, the inlet pipe and / or the outlet pipe may each comprise a vertical portion. For example, only the outlet pipe may comprise a vertical portion so as to form an annular vein. In addition, the upper level of the vertical portion of the outlet pipe may be positioned above the upper level of the inlet pipe. In other words, the annular outlet vein of the wheel ends at a vertical level higher than that of the inlet pipe of the toroidal reservoir, so as to facilitate priming of the pump. Indeed, this configuration makes it possible, when the pump is stopped, to flood the entire pump, including the toroidal liquid reservoir.

[0044] Preferably, when the pump is used in a closed circuit, such as an ORC circuit, the inlet line and the outlet line may be connected to the closed circuit so that the passage in the pump constitutes part of the closed circuit. Thus, the toroidal liquid reservoir may be designed so that its volume is sized to ensure a sufficient reserve of liquid for steady-state operation of the closed circuit to be ensured, with liquid exiting the outlet line and entering the next cycle through the inlet line.

[0045] According to a variant of the invention, the outlet pipe may be cylindrical, preferably annular, with an upward circulation of fluid, thus promoting self-priming of the pump. When it is annular, this outlet pipe makes it possible to obtain encapsulation of the entire pump. Thus, starting from the axis of the pump, we find the impeller, the connection means, the toric liquid reservoir and then the outlet pipe.

[0046] According to a preferred implementation of the invention, the pump may comprise an electric machine positioned on the axis of the pump wheel, the electric machine being connected to the pump wheel for example by a shaft. As a result, the electric machine can drive the pump wheel, while allowing a compact architecture of the system.

[0047] An implementation of the invention also relates to a turbogenerator comprising a turbine and a pump as described above with an electric machine. The turbine is positioned above the pump wheel, preferably, the electric machine being positioned between the turbine and the pump wheel. Thus, the electric machine can be used in motor mode to drive the pump wheel at start-up and in generator mode to recover energy from the turbine in stabilized operating mode. In addition, this turbogenerator allows for a compact architecture while facilitating pump priming and avoiding cavitation phenomena.

[0048] Advantageously, the turbine, pump and electrical machine can be built in a single component in a fully integrated and compact manner.

[0049] An implementation of the invention also relates to a closed circuit operating according to a Rankine cycle, the closed circuit comprising a heat exchanger for evaporating a fluid, an expansion means (a turbine for example) for expanding the fluid, a condenser for liquefying the fluid, and a pump as described above. Indeed, the pump allows for proper operation of the closed circuit. In addition, the design of this pump, which limits the risks of cavitation, is suitable for fluids in ORC circuits where the vaporization pressure of the fluid is, in fact, quite close to the operating pressure of the pump. Thus, the pump can have a longer service life.

[0050] Preferably, the closed circuit may comprise a heat exchanger for evaporating a fluid, a turbine for expanding the fluid, the turbine being connected to an electrical machine, a condenser for liquefying the fluid, and a pump, such that the pump, the turbine and the electrical machine form a turbogenerator as described above. Such an implementation allows for a compact system.

[0051] Advantageously, the condenser can be located at a level below the pump. In other words, the condenser is located below the pump. Thus, the condenser is positioned in the part where the liquid naturally rests. The pump according to the invention allows improved self-priming capabilities and can therefore be positioned above the condenser.

[0052] Furthermore, the invention also relates to the use of the closed circuit as described above in a light, heavy or utility vehicle comprising an internal combustion engine which may comprise a second cooling fluid and / or an EGR circuit. In other words, the invention relates to a method for recovering energy from a vehicle comprising an internal combustion engine using a closed circuit as described above. Preferably, exhaust gases from the internal combustion engine and / or a second cooling fluid from the internal combustion engine and / or a third fluid from an EGR circuit of the internal combustion engine are sent into the heat exchanger to vaporize the fluid from the closed circuit. This configuration is advantageous because it makes it possible to recover part of the energy in the form of heat, which would normally be lost in the vehicle, and to transform this energy into mechanical or electrical energy.It therefore increases the vehicle's performance.

[0053] For example, the condenser can be cooled by the vehicle's radiator cooling circuit.

[0054] The operation of the pump according to the invention can be described as follows.

[0055] Before any operation (when the pump is stopped for example), the toroidal liquid reservoir, the pump and the outlet line are filled with liquid.

[0056] When the pump starts, the liquid in the outlet line is discharged, for example to the evaporator of the ORC circuit. The discharged liquid is replaced in the volume of liquid contained in the toroidal liquid reservoir, positioned upstream of the pump impeller, in the direction of fluid flow. Over a period of time, the liquid level in the toroidal liquid reservoir decreases. For example, for an ORC circuit, the time may depend on the time required for the evaporator and condenser to reach satisfactory temperatures to allow the ORC circuit to start up.

[0057] THE figures 1 to 3 illustrate, in a schematic and non-limiting manner, a pump according to one embodiment of the invention.

[0058] There figure 1 illustrates the pump of the invention in a first section plane (X, Z), X being a horizontal axis and Z being the vertical axis. The figure 2illustrates the same pump of the invention according to a second section plane, in top view, X and Y being two horizontal axes (the vertical axis Z is orthogonal to the section plane (X, Y)). The figure 3 illustrates the same pump of the invention in perspective.

[0059] The pump of the invention comprises a toroidal reservoir 1 which serves to retain a sufficient volume of liquid to allow the pump to be primed. The pump also comprises a movable hub 4 on which is rigidly mounted a pump wheel 5 comprising here two blades 6 (alternatively, the pump wheel 5 could comprise another number of blades 6). The movable hub 4 is movable in rotation and drives the pump wheel in rotation.

[0060] The fluid circulates in the pump wheel from a wheel inlet 10 to a wheel outlet 11, the wheel inlet 10 being located above the wheel outlet 11, in operation, so as to facilitate the circulation of the fluid and in particular the priming of the pump.

[0061] The toroidal reservoir 1 is coaxial with the movable hub 4 and with the pump wheel 5 and it surrounds the movable hub 4 and the pump wheel 5. The toroidal reservoir 1 is supplied with liquid by the inlet pipe 2.

[0062] A connection means of revolution 8 with a revolution axis z makes it possible to supply the wheel inlet 10 from the toroidal reservoir 1. This connection means 8 is connected to the lower part of the toroidal reservoir 1 at a connection point 9 located below the pump inlet 10, so as to create a siphon which facilitates the priming of the pump and makes it possible to reduce the size of the machine along the z axis. This connection means 8 has a “swan neck” shaped section to facilitate the movement of the liquid. In addition, this connection means 8 has a liquid passage section 12 which increases between the connection point 9 and the wheel inlet 10, so as not to reduce the speed of passage of the liquid. Thus, the risks of cavitation at the pump wheel 5 are reduced.

[0063] In addition, vanes 7 are positioned on a fixed hub 16 mounted on the movable hub 4, between the impeller inlet 10 and the pump impeller 5. The fixed hub 16 is not rotated when the movable hub 4 is rotated. This is possible for example by using bearings or ball bearings between the movable hub 4 and the fixed hub 16. As a result, the vanes 7 are fixed, which makes it possible to reduce the tangential velocity of the fluid. In addition, the pump has an outlet pipe 3 for discharging the liquid. This outlet pipe 3 is connected to the impeller outlet 11. It comprises a connecting part 14 which connects the impeller outlet 11 to a radial part 13, the radial part being connected to a vertical part 15 of the outlet pipe 3.

[0064] The upper level of the vertical part 15 of the outlet pipe 3 is above the inlet pipe 2 so as to facilitate the retention of liquid in the pump, facilitating the starting of the pump and limiting the risks of cavitation.

[0065] As can be seen on the figure 2 , the toroidal reservoir 1 forms a torus all around the hub 4 and the pump wheel 5. Thus, it allows a compact architecture while guaranteeing a sufficient volume of liquid in this toroidal reservoir.

[0066] In the same way, the connection means 8 generating a siphon also forms a continuous shape all around the mobile hub 4 and the pump wheel 5. Thus, the liquid passage section is maximum and therefore the risks of cavitation are minimized. In addition, this continuous shape all around the wheel inlet allows a homogeneous distribution of the liquid in the pump wheel.

[0067] It is also observed in this figure that the vanes 7 (here eight radial vanes but a different number of vanes 7 could be used) are radial so as to reduce the circumferential or tangential speed of the liquid and thus limit the absolute speed in the pump impeller. By reducing the speed, the pressure drop is limited and consequently, the risks of cavitation are limited which could reduce the performance of the pump and damage the pump and in particular the pump impeller. Thus, the service life of the pump can be increased.

[0068] Furthermore, the outlet pipe 3, in particular the vertical part of the outlet pipe 3, also surrounds the toroidal reservoir 1. The outlet pipe 3 is therefore annular in shape so that the pump is encapsulated with different elements of this pump which surround other elements. This encapsulation allows for a compact architecture.

[0069] There figure 3is a perspective view where the sectional view of the figure 1 is shown in dark gray. It can be seen that in the center, the mobile hub 4 is positioned on which two vanes 6 of the pump wheel are mounted. Around this mobile hub 4, there is the connection means 8 in the form of a swan neck acting as a siphon.

[0070] Surrounding this swan-neck-shaped connection means 8 is the toroidal reservoir 1 where the connection with the connection means 8 is located at a vertical altitude lower than the pump inlet. Finally, surrounding this toroidal reservoir 1 is the outlet pipe 3 which forms a cylindrical ring for the passage of the fluid.

[0071] The toroidal reservoir 1, the vertical part of the outlet pipe 3, the connection means 8, the fixed and mobile hubs and the pump wheel are coaxial, so as to promote the homogeneity of the circulation of the fluid in the pump.

[0072] The mobile hub 4 can be rotated in a known manner by a shaft itself driven in rotation by an electric machine (not shown) in transient mode (for example for starting) or in stabilized mode, or driven in rotation by a turbine, in particular in stabilized mode.

[0073] To promote the compactness of the system, this electric machine is positioned above the mobile hub 4.

[0074] There figure 4 illustrates, schematically and in a non-limiting manner, a turbogenerator comprising a pump according to

[0075] the invention. In this figure, the X axis is a horizontal axis and the Z axis corresponds to the vertical axis. This turbogenerator comprises a pump P as described previously and in particular a pump conforming to the figures 1 to 3 .

[0076] Pump P is connected to an electric machine ME via a shaft A2. Thus, starting the electric machine ME as an electric motor enables the rotation of pump P.

[0077] Turbine T is connected to the electric machine ME by another shaft A1. Thus, the energy recovered by turbine T is transmitted to the electric machine ME which then operates as an electric generator to generate electricity or to drive pump P.

[0078] In operation, the turbine T is positioned above the electric machine ME, itself positioned above the pump P. In addition, the turbine T, the pump P, the shafts A1 and A2 as well as the electric machine ME are coaxial.

[0079] There Figure 5 illustrates, in a schematic and non-limiting manner, a closed circuit which operates according to a Rankine cycle.

[0080] The X axis represents a horizontal axis and the Z axis represents the vertical axis.

[0081] This circuit comprises a condenser C through which the coolant LR of a vehicle passes. Alternatively, the condenser C could be crossed by another cold source. In this condenser, the working fluid circulating in the closed circuit in the direction of the arrow F cools and liquefies. The working fluid is then admitted into a liquid reservoir Res. Then it arrives in the pump P of the invention, preferably a pump as described in the figures 1 to 3 The liquid inlet point on pump P is at a lower altitude than its outlet point on pump P.

[0082] The working fluid then enters an evaporator E, which here exchanges heat with the exhaust gases GE from a vehicle's internal combustion engine. Alternatively, the evaporator could exchange heat with other heat sources.

[0083] In this evaporator E, the working fluid heats up and vaporizes. At the outlet of the evaporator E, the working fluid circulating in the closed circuit is completely or almost completely gaseous.

[0084] The gas then passes through a turbine T which recovers part of the energy from the heat source. Here the turbine sets the shaft A1 in rotation which will drive the electric machine ME and thus produce electricity. The gas leaving the turbine T is returned to the condenser C.

[0085] So, the closed loop circuit is positioned between the ground on which the vehicle is traveling and the vehicle's exhaust pipes. It must therefore be compact to fit into such a confined space. Moreover, as can be seen in the Figure 5, the pump is not located at the lowest point of the circuit which could cause priming problems. The pump according to the invention, in particular thanks to the toroidal reservoir and the connection means generating a siphon, makes it possible to overcome these priming problems thanks to an integrated design adapted to the operating mode of the Figure 5 .

[0086] Furthermore, pump P is connected to the electric machine ME, which is positioned above it, by a shaft A2. Thus, the electric machine ME, which operates as an electric motor, can then drive pump P in rotation.

[0087] In other words, the electric machine ME can operate in electric motor mode to drive the pump and / or in electricity generator mode to produce electricity. The turbine T, the pump P, the electric machine ME and the shafts A1 and A2 can be designed in an integrated manner to form a compact turbogenerator, corresponding to the turbogenerator of the figure 4 .

[0088] The closed circuit and the pump or turbogenerator according to the invention are particularly suitable for use in a vehicle comprising an internal combustion engine.

[0089] It goes without saying that the invention is not limited to the embodiments of the invention described above as examples, but rather encompasses all variant embodiments covered by the scope of the appended claims.

Claims

1. Pump (P) comprising a pump impeller (5), the pump impeller (5) comprising an impeller inlet (10) and an impeller outlet (11), the pump impeller (5) being configured such that, in operation, the axis of the pump impeller (5) is vertical with the impeller inlet (10) arranged above the impeller outlet (11), the pump comprising a toric liquid reservoir (1) positioned around the pump impeller (5) and a connecting means (8) for connecting the liquid reservoir (1) to said pump impeller (5) at a connecting point (9) situated in a lower part of the liquid reservoir (1), the axis of the liquid reservoir (1) being the vertical axis (Z) of the pump impeller (5), characterized in that the connecting point (9) is positioned below said impeller inlet (10) so as to form a siphon, and in that a passage section (12) for the fluid in the connecting means (8) increases in the direction of circulation of the liquid in the pump (P) from said lower part of the toric liquid reservoir (1) to said impeller inlet (10).

2. Pump (P) according to Claim 1, wherein the connecting means (8) has a shape exhibiting symmetry of revolution about the vertical axis (Z) of the pump impeller (5).

3. Pump (P) according to either of the preceding claims, wherein the pump (P) comprises a movable hub (4) with a vertical axis, the pump impeller (5) being fixed to the movable hub (4).

4. Pump (P) according to Claim 3, wherein the pump (P) comprises a fixed hub (16) mounted on the movable hub (4) and the pump comprises vertical vanes (7) that are mounted on the fixed hub (16) and extend radially with respect to the fixed hub (16).

5. Pump (P) according to Claim 4, wherein the number of vertical vanes (7) is between 4 and 15.

6. Pump (P) according to one of the preceding claims, wherein the pump (P) comprises an inlet line (2) and an outlet line (3), the inlet line (2) being connected to the upper part of the liquid reservoir (1), the outlet line (3) being connected to the impeller outlet (11).

7. Pump (P) according to Claim 6, wherein the outlet line (3) comprises a vertical portion (15), the vertical portion of the outlet line (15) being positioned above the level of the inlet line (2).

8. Pump (P) according to one of the preceding claims, comprising an electric machine (ME) positioned on the axis of the pump impeller (5), the electric machine (ME) being connected to the pump impeller (5).

9. Turbogenerator comprising a turbine (T) and a pump (P) according to Claim 8, the turbine (T) being positioned above the pump impeller (5), the electric machine (ME) preferably being positioned between the turbine (T) and the pump impeller (5).

10. Closed circuit operating on a Rankine cycle, the closed circuit comprising a heat exchanger (E) for evaporating a fluid, an expansion means (T) for expanding the fluid, a condenser (C) for liquefying the fluid, and a pump (P) according to one of Claims 1 to 8.

11. Closed circuit operating on a Rankine cycle, the closed circuit comprising a heat exchanger (E) for evaporating a fluid, a turbine (T) for expanding the fluid, the turbine (T) being connected to an electric machine (ME), a condenser (C) for liquefying the fluid, and a pump (P), characterized in that the pump (P), the turbine (T) and the electric machine (ME) form a turbogenerator according to Claim 9.

12. Closed circuit according to either of Claims 10 and 11, wherein the condenser (C) is situated below the pump (P) .

13. Use of the closed circuit according to one of Claims 10 to 12 in a lightweight, heavy-duty or utility vehicle comprising an internal combustion engine, wherein exhaust gases (GE) from the internal combustion engine and / or a second cooling fluid (LR) from the internal combustion engine and / or a third fluid from an EGR circuit of the internal combustion engine are / is sent into the heat exchanger (E) in order to vaporize the fluid in the closed circuit.

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