WO2022233603A1

WO2022233603A1 - Two-compression-stage electric gas compressor

Info

Publication number: WO2022233603A1
Application number: PCT/EP2022/060740
Authority: WO
Inventors: Mickael LOSZKA
Original assignee: IFP Energies Nouvelles
Priority date: 2021-05-06
Filing date: 2022-04-22
Publication date: 2022-11-10
Also published as: FR3122708A1; EP4334595A1

Abstract

The present invention relates to a two-stage electric gas compressor (1), in which the electric machine (2) is arranged in the gas flow of the first compression wheel (3), and in which the second compression wheel (4) is arranged in the opposite direction to that of the first compression wheel (3).

Description

ELECTRIFIED GAS COMPRESSOR WITH DOUBLE COMPRESSION STAGE

Technical area

The present invention relates to the field of gas compression, in particular for supplying air to a fuel cell or an internal combustion engine.

Much work is currently devoted to the development of fuel cells as sources of electrical energy for power supply, both for stationary applications and for on-board applications, in particular for vehicles driven by electrical machines. Indeed, the environmental advantages of fuel cells (high electrical and energy yields, very low emissions of harmful gases, low noise pollution, localized production, etc.) are assets that are becoming important, in particular for the field of transport.

A fuel cell transforms chemical energy into electrical energy. In the case of a hydrogen/oxygen fuel cell, the chemical reaction implemented is a combustion of hydrogen in oxygen, the reaction of which can be written by the equation:

Within a fuel cell, the electrochemical oxidation of hydrogen is carried out at the level of an anode made of a conductive catalytic material, while the electrochemical reduction of oxygen occurs at the level of a cathode. generally made of the same catalytic material. In addition, the anodic and cathodic compartments are separated by an electrolyte allowing the exchange of protons or ions.

For motor vehicles, the fuel cells which currently prove to be the most promising are so-called proton exchange membrane cells, operating from a source of hydrogen coming either from a bottle on board the vehicle, or from a unit producing hydrogen directly in the vehicle. Thus, hydrogen can be produced directly using a reformer operating with an appropriate fuel, such as methanol, gasoline, diesel fuel, etc. Generally the oxygen admission is carried out by an air admission. This intake generally uses an air compressor to increase the amount of air introduced into the fuel cell.

In the field of combustion engines, the engine intake often includes supercharging means, which include a compressor, which can take the form of a turbocharger.

For these applications (as well as for other applications), it is often desired to have a high compression ratio, while limiting bulk and mass, in particular for on-board applications (for example a fuel cell or an internal combustion engine within a vehicle).

Prior technique

To obtain a high compression ratio, a first technical solution may be to use a single compression wheel, however such a compression wheel must have a large radial dimension, which increases its bulk and its mass, which makes its use in an embedded application. In addition, such a design requires a high rotation speed, which imposes strong constraints on the drive level (for example on the level of the electric machine) and on the level of the bearings ensuring the rotation of the compressor shaft.

To respond to this problem of size, electrified compressors with two compression stages have been developed.

For example, patent applications RU157678, RU157236, RU143266, JP2004332666 and W00017524 relate to electrified compressors with two compression stages, in which the electric machine is arranged between the two compression wheels. This design requires a large space between the two compression wheels, and generates stresses for the cooling and lubrication of the electric machine.

Summary of the invention The object of the invention is to compress a gas with a high compression ratio and by limiting the size of the compressor. For this, the present invention relates to a two-stage electrified gas compressor, for which the electric machine is placed in the gas flow of the first compression wheel, and for which the second compression wheel is arranged in the opposite direction to the direction of the first compression wheel. The use of two compression wheels ensures a high compression ratio and limits the weight of the compressor. Given the arrangement of the electric machine in the gas flow, the electric machine is included in the inlet of the compressor, which reduces its bulk, moreover, the bulk between the two compression wheels is reduced. The invention relates to an electrified gas compressor with two compression stages comprising an electric machine, a drive shaft driven by said electric machine, a first compression wheel mounted on said drive shaft, and a second compression wheel mounted on said compression shaft. Said electric machine is arranged in the gas flow supplying gas to said first compression wheel, and said second compression wheel is arranged on said drive shaft in the opposite direction to the direction of said first compression wheel.

According to one embodiment, said electric machine comprises at least one gas passageway through the stator of said electric machine and/or through the air gap of said electric machine, said at least one gas passageway supplying gas said first compression wheel.

Advantageously, said electric machine is a stator grid machine in which said at least one gas passageway is located in said stator of said electric machine.

According to one implementation, said compressor comprises a conduit which connects the gas outlet of said first compression wheel to the gas inlet of said second compression wheel.

Advantageously, said conduit comprises a heat exchanger.

According to one aspect, said compressor comprises at least one rolling means arranged between said first compression wheel and said second compression wheel.

Preferably, said rolling means is chosen from a roller bearing, a ball bearing, an air bearing or a magnetic bearing.

According to one embodiment option, said first compression wheel and said second compression wheel have an axial gas inlet and a radial gas outlet. According to one aspect, said compressor comprises a second electrical machine arranged in the gas flow supplying gas to said second compression wheel.

Furthermore, the invention relates to an electricity generation system comprising a fuel cell and a gas compressor according to one of the preceding characteristics for supplying said fuel cell with compressed air.

Furthermore, the invention relates to a vehicle, in particular a motor vehicle, comprising a system for generating electricity according to one of the preceding characteristics, and an electric traction machine for moving said vehicle, the electric traction machine being powered by said power generation system.

Other characteristics and advantages of the device according to the invention will appear on reading the following description of non-limiting examples of embodiments, with reference to the appended figures and described below. List of Figures

Figure 1 illustrates a gas compressor according to a first embodiment of the invention.

Figure 2 illustrates a gas compressor according to a second embodiment of the invention.

Figure 3 is a cross section of a stator grid electric machine that can be used in the compressor according to one embodiment of the invention.

Figure 4 is a longitudinal section of a large air gap electric machine that can be used in the compressor according to one embodiment of the invention.

Figure 5 is a sectional view of a compressor according to one embodiment of the invention.

Figure 6 illustrates a compressor according to a third embodiment of the invention.

Description of embodiments

The present invention relates to a gas compressor. According to the invention, the compressor is electrified. In other words, the compressor is driven by at least one electric machine. In addition, the compressor is two-stage. In other words, the compressor comprises two compression stages, so as to successively compress the gas, making it possible to obtain significant gas compression at a limited rotational speed.

Thus, the compressor according to the invention comprises:

At least one electric machine,

A drive shaft driven by the electric machine,

A first compression wheel mounted on the compression shaft, and A second compression wheel mounted on the compression shaft.

The notion of first compression wheel and second compression wheel is considered in the order of the compression wheels in which the gas circulates. In other words, within the compressor, the gas is compressed first in the first compression wheel, and in a second time in the second compression wheel.

According to the invention, the electric machine is arranged in the flow of gas supplying the first compression wheel. In other words, the electric machine is arranged at the inlet of the first compression wheel, the gas flow passing through the electric machine before entering the first compression wheel. Thus, the electric machine is included in the intake of the compressor, which reduces the bulk of the compressor, moreover, the bulk between the two compression wheels is reduced (there is no electric machine arranged between the two compressor wheels). Advantageously, all of the gas which enters the first compression wheel passes through the electric machine. For this embodiment, no gas circulates around the electrical machine. In addition, the rotor of the electric machine can be in contact with one end of the first compression wheel to limit the size, by reducing the distance between the electric machine and the first compression wheel.

In addition, the second compression wheel is arranged on the drive shaft in the opposite direction to the direction of the first compression wheel. In other words, the two compression wheels are mounted back to back: the faces of the compression wheels including the outlets of the compression wheels face each other. This arrangement of the two compression wheels allows a balancing of the forces, and a simplified implementation of the compressor.

Preferably, the first compression wheel and the second compression wheel can be centrifugal wheels.

In accordance with one implementation of the invention, the first compression wheel and the second compression wheel may be compression wheels having an inlet axial and a radial outlet. This design favors the implementation of compression wheels. For this implementation, given the inverted assembly of the two compression wheels, the input of the first compression wheel is oriented towards the electrical machine, while the input of the second compression wheel is oriented towards the other. end of the drive shaft. As a variant, the two compression wheels can be of different types.

According to one embodiment of the invention, the electric machine may comprise at least one gas passageway through the electric machine. For example, this at least one gas passageway can be located in the stator of the electric machine, and/or be located in the air gap of the electric machine. This gas passageway allows the admission of gas into the first compression wheel.

Preferably, the electric machine can be a stator grid electric machine. For this type of electric machine, the gas passageway is located in the stator of the electric machine. An example of such an electric machine is described in particular in patent application FR 3041831 (US 2018-0269744). Such an electric machine comprises a rotor and a stator. The rotor may include at least one permanent magnet. The stator comprises an outer crown, and radial stator teeth directed towards the rotor. Between the stator teeth is delimited a volume in which coils (to generate a magnetic flux) are mounted, and in which the gas passageways are formed. The coils are positioned close to the crown of the stator and away from the rotor. The gas passageways are delimited by the stator teeth and the coils. These gas passageways are preferably large in size to limit pressure drops in the gas flow. For this purpose, the cross-sectional area of the gas passageways may be at least similar to the cross-sectional area of the coils. For example, the section of the passageways can have substantially a triangular shape. This type of electric machine allows better magnetic performance compared to electric machines with a large air gap, for a limited mass. In addition, the passage of gas makes it possible to cool the coils of the stator, which makes it possible to use an electric machine without a cooling system or with a simplified cooling system.

As a variant, the electric machine can be an electric machine of the large Airgap (large air gap) type. For this type of machine, the air gap, that is to say the space between the rotor and the stator, is large, so as to allow the flow of gas to pass. In order to perform the two successive compressions, the compressor may further comprise a pipe which connects the outlet of the first compression wheel to the inlet of the second compression wheel. For the embodiment for which the two compression wheels have an axial inlet and a radial outlet, the pipe has a first radial portion (relative to the first compression wheel), and a last axial portion (relative to the second compression wheel).

According to an option of this embodiment of the invention, the pipe which connects the two compression wheels can comprise a heat exchanger. The heat exchanger can make it possible to reduce the temperature of the gas before entering the second compression wheel, and thus improve the performance of the compression. Indeed, it is easier to compress a cold fluid than a hot fluid. This embodiment option of the invention is particularly suitable for the use of the compressor for a fuel cell, for which the temperature of the gas (air) must be limited to protect the fuel cell components. The heat exchanger can be a heat exchanger with a coolant from a cooling circuit, the coolant can comprise water or any similar fluid.

In order to achieve the rotational guidance of the drive shaft relative to a casing, the compressor may comprise at least one rolling means. The rolling means can preferably be arranged between the first compression wheel and the second compression wheel. Advantageously, the compressor may comprise two rolling means, the two rolling means being arranged between the first compression wheel and the second compression wheel, one close to the first compression wheel, and one close to the second compression wheel. Thus, according to a preferred embodiment, the compressor may comprise successively, along the drive shaft, the electric machine, the first compression wheel, at least one rolling means, and the second compression wheel.

Due to the limited rotational speed of the drive shaft, the rolling means may be a bearing, a roller bearing, a ball bearing, an air bearing, a magnetic bearing, or any similar means. These rolling means, in particular the frictionless rolling means (balls, air, magnetic) make it possible to simplify the lubrication system and to limit lubrication leaks, which can pollute the compressed gas, such leaks possibly being particularly problematic. for a compressor application for a fuel cell. Where appropriate, the hydrocarbons present in the means of Lubrications can cause damage to the proton exchange membrane of the fuel cell.

According to one implementation of the invention, the compressor may comprise a second electric machine. The second electric machine can be arranged in the gas flow supplying gas to said second compression wheel. In this case, the gas circulates successively in the first electric machine, the first compression wheel, the second electric machine and the second compression wheel. This realization makes it possible to increase the available power, and ensures redundancy in the event of failure of one of the electrical machines.

For this implementation, the second electric machine can be identical (same type, same size) to the first electric machine arranged in the flow of gas supplying the first compression wheel. Thus, the compressor can be symmetrical.

Preferably, the second electrical machine can be a stator grid machine, in which the gas passes through the stator. As a variant, the second electric machine can be a machine with a large air gap.

When the compressor comprises a pipe, the pipe connects the outlet of the first compression wheel to the inlet of the second electric machine, the inlet of the second electric machine being considered in the direction of gas flow.

Figure 1 illustrates, schematically and in a non-limiting way, an electrified gas compressor with two compression stages according to a first embodiment of the invention. The compressor 1 comprises an electric machine 2 which drives a drive shaft 5. A first compression wheel 3 is mounted on the drive shaft 5. A second compression wheel 4 is mounted on the drive shaft 5 The second compression wheel 4 is arranged in the opposite direction to the direction of the first compression wheel 3. The compressor 1 further comprises two bearings 6 for guiding the drive shaft 2 in rotation. compressor 1 comprises a pipe 7 which connects the radial outlet 10 of the first compression wheel 3 to the axial inlet 11 of the second compression wheel 4.

In this figure, the arrows illustrate the circulation of the gas to be compressed by the compressor. A gas to be compressed 8, for example air, passes through the electric machine 2 through at least one gas passageway 9. Then, the gas passes through the first compression wheel 3 to come out through the outlet 10 of the first compression wheel 3. The compressed gas passes through the pipe 7 to arrive at the inlet 11 of the second compression wheel 4. The compressed gas leaves the second compression wheel 4 through the outlet 12 of the second compression wheel 4.

Figure 2 illustrates, schematically and in a non-limiting way, a compressor according to a second embodiment of the invention. The elements identical to the first embodiment of FIG. 1 are not described again. For this embodiment, the pipe 7 further comprises a heat exchanger 13. Preferably, the heat exchanger 13 exchanges heat between the compressed gas at the outlet of the first compression wheel 3 and a cooling fluid. Thus, at the outlet of the heat exchanger 13, the compressed gas comes out cooled before the second compression.

Figure 3 illustrates, schematically and in a non-limiting manner, an electric machine with a stator grid, as described in patent application FR 3041831 (US 2018-0269744). Figure 3 is a sectional view in a plane transverse to the axis of the rotor and the stator. The electric machine 2 comprises a rotor 17 and a stator 14. An air gap E is provided between the rotor 17 and the stator 14. This air gap E is of limited size (for example of the order of 0.5 mm) to improve the magnetic performance of the electric machine. The stator 14 of the electric machine comprises a crown 20, from which a plurality of stator teeth 18 start. The stator teeth 18 are radial. A volume 16 is formed by the stator teeth 18 and the crown 20. Within the volume 16 are arranged the coils 19 which generate a magnetic flux. The coils 19 are arranged close to the crown 20 and are remote from the rotor 17. In addition, gas passageways 15 are formed in these volumes 16. The gas passageways 15 are delimited by the stator teeth 18 and by the coils 19. These gas passageways 15 have substantially a triangular section. In addition, the area of the section of the gas passageways 15 is at least similar to the area of the section of the coils 19. Thus, almost all of the gas supplying the first compression wheel of the compressor passes through the stator in the gas pathways 15.

Figure 4 illustrates, schematically and in a non-limiting manner, an electrical machine with a large air gap. Figure 4 is a sectional view in the longitudinal plane to the axis of the rotor and the stator. The electric machine 2 comprises a rotor 17 and a stator 14. An air gap E is provided between the rotor 17 and the stator 14. This air gap is of large size (of the order of a few mm, or even a few cm), so to form an annular passageway 9 around the rotor 17. Thus, almost all of the gas supplying the first compression wheel of the compressor passes through the electrical machine in the air gap E.

Figure 5 illustrates, schematically and in a non-limiting manner, a compressor according to one embodiment of the invention. Figure 5 is a longitudinal sectional view of the electrified compressor with two compression stages. In this figure, the stator of the electric machine, and the casing are not represented. At one end of the drive shaft 9 is fixedly mounted the rotor 17. For the example shown, the rotor 17 comprises a permanent magnet 21 and a non-magnetic hoop 22. Other embodiment variants of the rotor can be envisaged. Near the rotor 17, a first compression wheel 3 is mounted on the drive shaft 9. At the other end of the compression shaft 9 is mounted a second compression wheel 4. Between the two compression wheels 3 and 4, there is provided a first bearing support 24 for mounting a rolling means for guiding in rotation in a housing. The rolling means comprises the bearing support in the form of a spacer 24 and a ring 27, as well as rolling elements such as balls (not shown). The spacer 24 bears against the shoulder 25 of the drive shaft 9. The ring 27 is provided with means for lubricating the rolling means. In addition, retaining means, such as a nut 23 can be provided at the second end of the drive shaft 9. The nut 23 allows the mounting and holding in position of the second compression wheel 4.

Figure 6 illustrates, schematically and in a non-limiting manner, a compressor according to a third embodiment of the invention. The elements identical to the first embodiment of FIG. 1 are not described again. For this embodiment, the compressor comprises a second electric machine 2′. The second electric machine 2' is arranged in the flow of gas from the second compression wheel 4. The second electric machine 2' comprises at least one gas passageway 9', which makes it possible to direct the gas at the outlet of the pipe 7 to the second compression wheel 4. This embodiment may also include a heat exchanger (not shown) on line 7.

Furthermore, the invention relates to an electricity generation system. The electricity generation system comprises at least one fuel cell and one compressor according to any one of the variants or combinations of variants as described previously. The compressor generates compressed air for the oxygen intake of the fuel cell. Indeed, the compressor according to the invention is particularly suitable for the air compression for a fuel cell, in particular in terms of compression ratio and air temperature.

Preferably, the fuel cell can be a low-temperature fuel cell, for example a fuel cell of the proton-exchange polymer membrane (PEMFC) type. This type of fuel cell is currently the most suitable for mobile applications, in particular because of its cost. Alternatively, the fuel cell can be a high temperature fuel cell, for example SOFC from the English “Solid Oxide Fuel Cell” which can be translated as solid oxide fuel cell or MCFC from the English “Molten Carbonate Fuel Cell”. which can be translated as molten carbonate fuel cell.

Alternatively, the invention also relates to an internal combustion engine provided with a compressor according to any one of the variants or combinations of variants as described previously. The compressor generates compressed air for the air intake into the cylinders of the internal combustion engine.

Furthermore, the invention relates to a vehicle, in particular an automobile road vehicle or heavy goods vehicle (or also a bus, a boat, an airplane, a hovercraft, an amphibious vehicle, etc.), comprising a fuel cell supplying at least one electric machine, and a compressor according to any one of the variants or combinations of variants described above. Preferably, the fuel cell can be a low-temperature fuel cell, for example a fuel cell of the proton-exchange polymer membrane (PEMFC) type. This type of fuel cell is currently the most suitable for mobile applications, in particular because of its cost. Alternatively, the fuel cell can be a high temperature fuel cell, for example SOFC from the English “Solid Oxide Fuel Cell” which can be translated as solid oxide fuel cell or MCFC from the English “Molten Carbonate Fuel Cell”. which can be translated as molten carbonate fuel cell.

Alternatively, the invention relates to a vehicle, in particular a motor vehicle or heavy goods vehicle (or also a coach, a boat, an airplane, a hovercraft, an amphibious vehicle, etc.), comprising an internal combustion engine provided with a compressor according to one any of the variants or combinations of variants as described previously.

Alternatively, the invention also relates to a fuel cell or an internal combustion engine for a stationary system, the fuel cell or the internal combustion engine being equipped with a compressor according to any one of the preceding characteristics.

It goes without saying that the invention is not limited solely to the embodiments of the compressor described above by way of example, on the contrary it encompasses all variant embodiments.

Claims

1. Electrified gas compressor with two compression stages comprising an electric machine (2), a drive shaft (5) driven by said electric machine (2), a first compression wheel (3) mounted on said drive (5), and a second compression wheel (4) mounted on said drive shaft (5), characterized in that said electric machine (2) is arranged in the gas flow supplying gas to said first compression wheel (3), and in that said second compression wheel (4) is arranged on said drive shaft (5) opposite to the direction of said first compression wheel (3).

2. Gas compressor according to claim 1, wherein said electrical machine (2) comprises at least one gas passageway (9) through the stator of said electrical machine (2) and / or through the air gap of said electric machine (2), said at least one gas passageway (9) supplying gas to said first compression wheel (3).

3. Gas compressor according to claim 2, wherein said electric machine (2) is a stator grid machine in which said at least one gas passageway (9) is located in said stator of said electric machine.

4. Gas compressor according to one of the preceding claims, wherein said compressor (1) comprises a pipe (7) which connects the gas outlet of said first compression wheel (3) to the gas inlet of said second compression wheel (4).

5. A gas compressor according to claim 4, wherein said conduit (7) comprises a heat exchanger (13).

6. Gas compressor according to one of the preceding claims, wherein said compressor (1) comprises at least one bearing means (6) arranged between said first compression wheel (3) and said second compression wheel (4).

7. A gas compressor according to claim 6, wherein said bearing means (6) is selected from a roller bearing, a ball bearing, an air bearing or a magnetic bearing.

8. Gas compressor according to one of the preceding claims, wherein said first compression wheel (3) and said second compression wheel (4) have an axial gas inlet and a radial gas outlet.

9. Gas compressor according to one of the preceding claims, wherein said compressor (1) comprises a second electric machine (2 ') arranged in the gas flow supplying gas to said second compression wheel (4).

10. Electricity generation system comprising a fuel cell and a gas compressor (1) according to one of the preceding claims for supplying said fuel cell with compressed air.

11. Vehicle, in particular motor vehicle, comprising an electricity generation system according to claim 10, and an electric traction machine for moving said vehicle, the electric traction machine being powered by said electricity generation system.