WO2022128545A1

WO2022128545A1 - Self-priming pump

Info

Publication number: WO2022128545A1
Application number: PCT/EP2021/084239
Authority: WO
Inventors: Philippe Pagnier; Pascal SMAGUE; Benoit Talvard; Stephane Venturi; Eric PEURIERE; Jocelyn TERVER; David Serrano
Original assignee: IFP Energies Nouvelles
Priority date: 2020-12-15
Filing date: 2021-12-03
Publication date: 2022-06-23
Also published as: FR3117554A1; FR3117554B1; EP4264056A1

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

SELF-PRIMING PUMP

Technical area

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 vehicles, heavy, light or utilities.

Prior technique

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 dimensioning of this pump leads to objects of relatively very small size (typically diameters included between 5 to 100 millimeters, preferably 5 to 50 mm) given the high speed of rotation (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, comprised between 1 to 5 bar (1 bar=0.1 MPa), preferably from 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.

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

In addition, the architecture of the vehicle often requires the pump to be placed in a position higher than that of the coolant reservoir of the ORC circuit, which generates a risk of the pump becoming unprimed when the vehicle is stationary.

Due to the architecture of light vehicle engines and the desire to position the expansion machine at the high 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 a operation of the pump without risk of cavitation and generally does not allow good priming of the pump.

Under these conditions, it is necessary to design a self-priming pump minimizing the risks of cavitation, while ensuring the pressure gain necessary for the proper functioning of the ORC cycle as a whole.

Patent application CN110469542A relates to a supply pump which comprises a simple recirculation loop with a restriction at the pump outlet, which makes it possible to locally increase the pressure of the fluid at the inlet of the impeller and avoid the formation of pockets. cavitation. But this system does not allow self-priming of the pump, in particular if the pump is placed along a vertical axis.

Also known are applications CN110657099A and CN207795594U which relate to double inlet pumps comprising both a liquid reservoir placed on the upper part and a recirculation loop. The upper tank allows the pump to be primed when necessary while the recirculation loop allows, as for patent CN110469542A, to locally increase the pressure at the inlet of the pump to prevent the formation of cavitation pockets. However, this type of double inlet pumps is not applicable to the case of vehicles because they are bulky. Furthermore, recirculation loops can disturb the flow at the inlet of the pump impeller, which can lead to a loss of efficiency.

Finally, application CN208858581 U 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 makes it possible to inject fluid from a reservoir up to the level of the inlet of the inlet pipe. The tank is itself pressurized from the fluid coming from the discharge of the pump.

The object of the invention consists in obtaining a very compact pump, self-priming and limiting the risk of cavitation, so that it can be used in particular in vehicle ORC circuits.

The use of this specific pump in an ORC circuit also makes it possible to reduce CO2 emissions from road transport.

It also makes it possible to electrify vehicles since part of the heat recovered in the ORC cycle can be used to power an electric machine. To meet these challenges, the invention relates to a pump 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 pump impeller axis is vertical with the impeller inlet disposed above the impeller outlet. The pump includes 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 wheel and surrounds the pump wheel. The pump also includes connection means for connecting the liquid reservoir to the pump impeller, at a connection point located in a lower part of the liquid reservoir. In addition, the means of connection between the liquid reservoir and the inlet of the impeller forms a siphon, thus making it possible to improve the self-priming capacities of the pump. Thus, the connection point is located below the wheel entry. In addition, the passage section of the fluid in the connection means increases in the direction of circulation of the liquid in the pump from the lower part of the toroidal liquid reservoir towards the inlet of the pump wheel, so as to reduce the speed of circulation of the fluid and thus increase the pressure which contributes to limiting the risks of cavitation. The flow path at the outlet of the pump is centrifugal radial, then axial ascending so 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 toroidal reservoir upstream and the connection means between the toroidal reservoir and the inlet of the pump wheel.

The invention also relates to a turbine generator comprising a turbine and a pump with an electric machine connected to the pump wheel and positioned above the pump wheel. The impeller is positioned above the pump wheel and connected to the electric machine. Preferably, the electric machine is positioned between the turbine and the pump wheel.

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 .

The invention also relates to the use 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 of the internal combustion engine and/or a third fluid of a burnt gas recirculation circuit (called EGR for “Exhaust Gas Recirculation” in English) of the internal combustion engine in the heat exchanger to vaporize the closed circuit fluid.

Summary of the invention

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 disposed above the impeller outlet, the pump comprising a toroidal liquid reservoir positioned around the pump impeller and connection means for connecting the liquid reservoir to said pump impeller, at the level of 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 wheel. 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 part lower part of the toric liquid reservoir towards said wheel inlet.

Preferably, the connection means has a form of revolution around the vertical axis of the pump wheel.

According to one implementation of the invention, the pump comprises a mobile hub with a vertical axis, the pump wheel being fixed to the mobile hub.

Advantageously, the pump comprises a fixed hub mounted on the mobile hub and the pump comprises vertical fins mounted on the fixed hub and extending radially with respect to the fixed hub.

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

According to a 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.

Preferably, the outlet pipe includes a vertical portion, the vertical portion of the outlet pipe being positioned above the level of the inlet pipe.

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.

The invention also relates to a turbine generator comprising a turbine and a pump as described, the turbine being positioned above the pump wheel, preferably, the electric machine being positioned between the turbine and the pump wheel.

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, a means of expansion to expand the fluid, a condenser to liquefy the fluid, and a pump as described.

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, a turbine for expanding the fluid, the turbine being connected to an electric machine, a condenser for liquefying the fluid , and a pump. In addition, the pump, the turbine and the electric machine form a turbogenerator as described above.

Preferably, the condenser is located below the pump.

Furthermore, the invention also relates to the use of the closed circuit as described previously 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 of the internal combustion engine and/or a third fluid of an EGR circuit of the internal combustion engine in the heat exchanger to vaporize the fluid of the closed circuit.

List of Figures

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 description below of non-limiting examples of embodiments, with reference to the appended figures. and described below.

Figure 1 shows a sectional view in the plane (X, Z) of a pump according to the invention.

Figure 2 shows a sectional view in the plane (X, Y) of the pump of Figure 1 according to the invention.

Figure 3 shows a perspective view of the pump of Figures 1 and 2 according to the invention.

Figure 4 shows a turbine generator according to the invention.

FIG. 5 represents a closed circuit operating according to a Rankine cycle according to the invention.

Description of embodiments The terms "vertical", "above", "below", "lower" and "upper" are understood, within the meaning of the invention, with respect to the pump in the operating position, in this case the pump is vertical axis.

A pump includes a pump impeller and the pump impeller includes 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 circulation of the fluid to the pump and thus facilitate priming. Thus, the gravity applied to the liquid facilitates the starting of the pump.

The pump further comprises a toroidal liquid reservoir (i.e. the liquid reservoir forms a torus) 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 toric liquid reservoir is a volume of revolution whose axis is coaxial with the pump wheel and it surrounds the pump wheel. This configuration results in a compact system. The toric liquid reservoir surrounding the pump impeller also allows the installation of a possible electric machine, above the pump impeller, without increasing the size of the system. The toroidal fluid reservoir maintains a sufficient reserve of fluid at start-up until the system is operating in steady state. Indeed, at the time of starting, the level of liquid in the tank will drop to steady state. Thus, the volume of the toroidal liquid reservoir can be designed to provide a sufficient volume of liquid for the system in which the pump is installed to reach a permanent steady state.

Furthermore, 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 wheel. Furthermore, the connection junction (or connection point) is positioned below the impeller inlet 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 you want to mount this pump on an ORC circuit. of a vehicle. In addition, the passage section of the fluid in the connection means increases in the direction of circulation of the liquid in the pump from the lower part of the toroidal 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. Thus, the pump according to the invention does not require a recirculation loop to facilitate self-priming of the pump. It therefore differs from the solutions of the prior art.

According to the invention, the pump can be an axial, mixed, centrifugal or radial pump.

Preferably, the connection means can have a form of revolution around the vertical axis of the pump wheel. In other words, the connection means totally surrounds the pump impeller, it is coaxial with the pump impeller and it is positioned between the pump impeller and the toroidal liquid reservoir. Such a shape of the connection means makes it possible to increase the passage section of the liquid and further reduce the circulation speeds.

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 mobile hub (mobile in rotation) can 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.

Advantageously, the pump may comprise fixed vertical fins mounted on a fixed hub, itself mounted on the mobile hub, the vertical fins being positioned before the entry of the pump wheel and extending radially with respect to the fixed hub. These fins make it possible to greatly reduce the tangential speed of the liquid before the liquid arrives on the pump impeller. By reducing the tangential velocity, the total velocity of the liquid is reduced. Preferably, the vanes are positioned above the impeller, on the fixed hub, before the entry of the impeller. The rotation of the mobile hub does not cause the rotation of the fixed hub. To do this, means known to those skilled in the art can be used, such as bearings or ball bearings.

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 increase the flow velocity (component of the velocity contained in the cutting plane of Figure 1) of the fluid arriving at the pump wheel.

According to a configuration of the invention, the pump can 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 outlet of wheel. Therefore, the pump can be easily implemented in a circuit. Preferably, the inlet pipe and/or the outlet pipe may each comprise a vertical portion. For example, only the outlet pipe can include a vertical portion so as to form an annular vein. Additionally, 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 impeller outlet vein terminates at a higher vertical level 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.

Preferably, when the pump is used in a closed circuit, such as an ORC circuit, the inlet line and the outlet line can be connected to the closed circuit so that the passage in the pump forms part of the closed circuit. Thus, the toroidal liquid reservoir can be designed in such a way that its volume is dimensioned so as to ensure a reserve of sufficient liquid for the operation in steady state of the closed circuit to be ensured, the liquid leaving the outlet pipe, incoming, to the next cycle through the inlet line.

According to a variant of the invention, the outlet pipe may be cylindrical, preferably annular, with upward fluid circulation, 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.

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. Therefore, the electric machine can drive the pump wheel, while allowing a compact architecture of the system.

The invention also relates to a turbogenerator comprising a turbine and a pump as described previously with an electric machine. The turbine is positioned above the pump wheel, preferably, the electrical 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 on start-up and in generator mode to recover energy from the turbine in stabilized operating mode. In addition, this turbogenerator allows a compact architecture while facilitating pump priming and avoiding cavitation phenomena. Advantageously, the turbine, the pump and the electric machine can be built in a single component in a fully integrated and compact manner.

The invention also relates to a closed circuit operating according to a Rankine cycle, the closed circuit comprising a heat exchanger to evaporate a fluid, an expansion means (a turbine for example) to expand the fluid, a condenser to liquefy the fluid, and a pump as previously described. Indeed, the pump allows a good functioning of the closed circuit. In addition, the design of this pump, which limits the risk 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.

Preferably, the closed circuit can comprise a heat exchanger to evaporate a fluid, a turbine to expand the fluid, the turbine being connected to an electric machine, a condenser to liquefy the fluid, and a pump, so that the pump, the turbine and the electrical machine form a turbogenerator as described previously. Such an implementation allows a compact system.

Advantageously, the condenser can be located at a level lower than the level of 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.

Furthermore, the invention also relates to the use of the closed circuit as described previously in a light, heavy or utility vehicle comprising an internal combustion engine which can 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 of 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 performance of the vehicle. For example, the cooling of the condenser can be ensured by the cooling circuit of the radiator of the vehicle.

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

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

When the pump starts, the liquid in the outlet line is evacuated, for example to the evaporator of the ORC circuit. The evacuated 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 circulation. For a while, the fluid level in the toroidal fluid reservoir drops. For example, for an ORC circuit, the time may depend on the time necessary for the evaporator and the condenser to be at satisfactory temperatures to allow the start-up of the ORC circuit.

Figures 1 to 3 illustrate, schematically and without limitation, a pump according to one embodiment of the invention.

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. Figure 2 illustrates 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)). Figure 3 illustrates the same pump of the invention in perspective.

The pump of the invention comprises a toroidal reservoir 1 which is used to maintain a sufficient volume of liquid to allow priming of the pump. The pump also comprises a mobile 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 mobile hub 4 is mobile in rotation and drives the pump wheel in rotation.

The fluid circulates in the pump impeller from an impeller inlet 10 to an impeller outlet 11, the impeller inlet 10 being located above the impeller outlet 11, in operation, so as to facilitate the circulation of the fluid and in particular the priming of the pump.

The toroidal reservoir 1 is coaxial with the mobile hub 4 and with the pump impeller 5 and it surrounds the mobile hub 4 and the pump impeller 5. The toroidal reservoir 1 is supplied with liquid by the inlet pipe 2. A revolution connection means 8 of axis of revolution 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 the level of a connection point 9 located below the pump inlet 10, so as to create a siphon which facilitates 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 section in the shape of a "gooseneck" 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 liquid passage speed. Thus, the risks of cavitation at the level of the pump wheel 5 are reduced.

In addition, fins 7 are positioned on a fixed hub 16 mounted on the mobile hub 4, between the wheel inlet 10 and the pump wheel 5. The fixed hub 16 is not driven in rotation when the mobile hub 4 is rotated. This is possible for example by using bearings or ball bearings between the mobile hub 4 and the fixed hub 16. As a result, the fins 7 are fixed, which makes it possible to reduce the tangential speed of the fluid.

In addition, the pump has an outlet line 3 to evacuate the liquid. This outlet pipe 3 is connected to the wheel outlet 11 . It comprises a connecting part 14 which communicates the wheel outlet 11 to a radial part 13, the radial part being connected to a vertical part 15 of the outlet pipe 3.

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.

As can be seen in 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.

In the same way, the connection means 8 generating a siphon also forms a continuous shape all around the movable 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 impeller inlet allows a homogeneous distribution of the liquid in the pump impeller.

It is also observed in this figure that the fins 7 (here eight radial fins but a different number of fins 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 wheel of pump. By reducing the speed, the pressure drop is limited and consequently the risks of cavitation which could reduce the performance of the pump and damage the pump and in particular the pump impeller are limited. Thus, the service life of the pump can be increased. In addition, the outlet pipe 3, in particular the vertical part of the outlet pipe 3, also surrounds the toric reservoir 1 . The outlet pipe 3 is therefore of annular shape so that the pump is encapsulated with various elements of this pump which surround other elements. This encapsulation allows a compact architecture.

Figure 3 is a perspective view where the sectional view of Figure 1 is shown in dark gray. It can be seen that in the center is positioned the mobile hub 4 on which is mounted two blades 6 of the pump wheel. Around this movable hub 4 is the connection means 8 in the form of a gooseneck acting as a siphon.

Surrounding this gooseneck-shaped connection means 8, there is the toric tank 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, there is the outlet pipe 3 which forms a cylindrical ring for the passage of the fluid.

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

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, especially in steady state.

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

Figure 4 illustrates, schematically and in a non-limiting way a turbogenerator according to 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 Figures 1 to 3.

The pump P is connected to an electric machine ME via a shaft A2. Thus, starting up the electric machine ME as an electric motor allows the rotation of the pump P.

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

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. FIG. 5 illustrates, schematically and without limitation, a closed circuit which operates according to a Rankine cycle.

The X axis represents a horizontal axis and the Z axis represents the vertical axis.

This circuit includes a condenser C through which the LR coolant of a vehicle passes. Alternatively, 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 to a Res liquid reservoir. Then it arrives in the pump P of the invention, preferably a pump as described in Figures 1 to 3. The point of entry of the liquid on the pump P is at an altitude lower than its point of exit on the pump p.

The working fluid then arrives in an evaporator E which here exchanges heat with the exhaust gases GE of the internal combustion engine of a vehicle. Alternatively, the evaporator could exchange heat with other hot sources.

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 totally or almost totally gaseous.

The gas then passes through a turbine T which recovers part of the energy from the hot source. Here the turbine rotates the shaft A1 which will drive the electric machine ME and thus produce electricity. The gas leaving the turbine T is returned to the condenser C.

Thus, the closed-loop circuit is positioned between the ground on which the vehicle travels and the vehicle's exhaust pipes. It must therefore be compact to fit into such a small space. In addition, as can be seen in 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 mode of operation of Figure 5.

Furthermore, the 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 the pump P in rotation.

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 way to form a compact turbogenerator, corresponding to the turbogenerator of figure 4.

The closed circuit and the pump or the turbogenerator according to the invention are particularly suitable for use in a vehicle comprising an internal combustion engine. It goes without saying that the invention is not limited solely to the embodiments of the invention, described above by way of example, on the contrary it embraces all variant embodiments.

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) disposed above the impeller outlet (11), the pump comprising a toroidal fluid reservoir (1) positioned around the pump wheel (5) and a connection means (8) for connecting the liquid reservoir (1) to said pump wheel (5), at a connection point (9) located in a lower part of the liquid reservoir (1), the axis of the liquid reservoir (1) being the vertical axis (Z) of the pump wheel (5), characterized in that the connection point (9 ) is positioned below said impeller inlet (10) so as to form a siphon, and in that the passage section (12) of the fluid in the connection means (8) increases in the direction of circulation of the liquid in the pump (P) since s said lower part of the toroidal liquid reservoir (1) towards said impeller inlet (10).

2. Pump (P) according to claim 1, for which the connection means (8) has a form of revolution around the vertical axis (Z) of the pump wheel (5).

3. Pump (P) according to one of the preceding claims, wherein the pump (P) comprises a movable hub (4) of vertical axis, the pump wheel (5) being fixed on 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) mounted on the fixed hub (16 ) and extending radially relative to the fixed hub (16).

5. Pump (P) according to claim 4, for which the number of vertical fins (7) is between 4 and 15.

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

7. Pump (P) according to claim 6, wherein the outlet pipe (3) comprises a vertical portion (15), the vertical portion of the outlet pipe (15) being positioned above the level of the pipe d entrance (2).

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

9. Turbogenerator comprising a turbine (T) and a pump (P) according to claim

8, the turbine (T) being positioned above the pump wheel (5), preferably the electric machine (ME) being positioned between the turbine (T) and the pump wheel (5).

10. Closed circuit operating according to a Rankine cycle, the closed circuit comprising a heat exchanger (E) to evaporate a fluid, an expansion means (T) to expand the fluid, a condenser (C) to liquefy the fluid, and a pump (P) according to one of claims 1 to 8.

11. Closed circuit operating according to a Rankine cycle, the closed circuit comprising a heat exchanger (E) to evaporate a fluid, a turbine (T) to expand 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 one of claims 10 or 11, for which the condenser (C) is located below the pump (P).

13. Use of the closed circuit according to one of claims 10 to 12 in a light, heavy or utility vehicle comprising an internal combustion engine for which exhaust gases (GE) from the internal combustion engine and/or a second cooling fluid (LR) of the internal combustion engine and/or a third fluid of an EGR circuit of the internal combustion engine in the heat exchanger (E) to vaporize the fluid of the closed circuit.