Air compressor for fuel cell

Abstract

An air compressor for a fuel cell includes a compressor section having a compressor inlet configured to receive gas into the compressor section and a compressor outlet configured to discharge compressed gas from the compressor section, the compressor section includes a first compressor impeller mounted within the compressor section and rotatable to effect air compression; and a second compressor wheel mounted within the compressor section and further away from the compressor inlet than the first compressor wheel, and rotatable to effect air compression, the first compressor wheel and the second compressor wheel are configured such that gas entering the compressor section flows through the first compressor wheel and the second compressor wheel to twice compress the gas. The air compressor can provide high-pressure air at a relatively low rotating speed of the rotor.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and more particularly to an air compressor for fuel cells. Background Technology

[0002] Fuel cells are widely used in various systems due to their high efficiency and environmental friendliness. Fuel cells use fuel and oxygen from the air as feedstock. To improve fuel cell performance, an air compressor is typically used to compress air to increase oxygen density, allowing more oxygen to participate in the reaction.

[0003] In existing technologies, air compressors typically include a compressor section and an expander section, located on either side of the motor section containing the electric motor. Air is compressed by the compressor impeller in the compressor section before entering the fuel cell intake passage. Meanwhile, the fuel cell exhaust gas is expanded and accelerated by the expander impeller in the expander section to assist the motor rotor's rotation, thereby reducing system power consumption. Bearing cooling air comes from the compressor impeller exhaust gas and is pre-cooled by an internal heat exchanger before cooling the air bearings.

[0004] As the output power requirements of existing systems increase, the performance requirements of fuel cells are also rising. One way to increase the power of a fuel cell is to increase the density of the oxygen used in the reaction. To do this, the air in the compressor section often needs to be further compressed to obtain a higher density, thereby providing a larger amount of oxygen.

[0005] To increase the density of compressed air, it's common practice to increase the rotor speed to raise the compressor impeller's rotational speed, or to enlarge the impeller diameter to improve the compressor's boosting capacity. However, rotor speed and impeller diameter are limited by the load-bearing capacity of the air bearings and the shaft's motion performance. Higher speeds and impeller diameters require more robust designs and materials for rotor components and bearings, as well as higher manufacturing standards. Especially when high airflow and pressure ratios are required, rotor speed and impeller diameter will be significantly increased to achieve the desired aerodynamic performance. This leads to increased manufacturing costs and compressor size, posing significant challenges to production and product reliability.

[0006] Therefore, there is a current need for an air compressor that can provide higher density compressed air without increasing rotor speed and reducing product size. Summary of the Invention

[0007] To address the problem that existing air compressors struggle to deliver higher-pressure compressed air without improvements to the rotor and bearings, this invention provides an air compressor for fuel cells.

[0008] Specifically, this air compressor for fuel cells includes a compressor section having a compressor inlet and a compressor outlet. The compressor inlet is configured to receive gas into the compressor section, and the compressor outlet is configured to discharge compressed gas from the compressor section. The compressor section includes: a first compressor impeller mounted within the compressor section and rotatable; and a second compressor impeller mounted within the compressor section and mounted further away from the compressor inlet than the first compressor impeller, also rotatable. The first and second compressor impellers are configured to cause gas entering the compressor section to flow through both impellers for double compression.

[0009] Furthermore, this air compressor for fuel cells also includes a rotating shaft that extends at least partially within the compressor section, and both the first compressor impeller and the second compressor impeller are fixedly mounted on the rotating shaft to rotate together with it.

[0010] Advantageously, the first compressor impeller and the second compressor impeller are arranged such that the back of the first compressor impeller abuts against the nose of the second compressor impeller, so as to make the compressor size more compact, thereby having a favorable effect on the arrangement of the compressor.

[0011] Advantageously, the outlet diameter of the first compressor impeller is larger than that of the second compressor impeller. The larger outlet diameter allows the first compressor impeller to deliver a greater gas flow rate.

[0012] In a preferred embodiment of the invention, the air compressor for fuel cells further includes a diffuser plate installed within the compressor section between the first compressor impeller and the second compressor impeller, such that the diffuser plate and the compressor section define a diffuser channel.

[0013] In a specific embodiment, the diffuser channel is curved, extending from the outlet of the first compressor impeller to the inlet of the second compressor impeller, and includes a diffuser section, a curved section, and a recirculation section. Thus, the diffuser channel can guide the airflow leaving the outlet of the first compressor impeller back to the inlet of the second compressor impeller.

[0014] In one embodiment, the diffuser plate can be integrally formed with the compressor section to save on parts used to fasten them together.

[0015] The diffuser plate and the resulting diffuser section, bend section and recirculation section diffuse, guide and cool the compressed air in the primary compressor to ensure that the compressed gas can flow efficiently through the impeller of the second compressor.

[0016] In a preferred embodiment of the invention, the compressor section includes a first compressor housing and a second compressor housing, which are assembled together, wherein at least a portion of the diffuser plate is sandwiched between the first compressor housing and the second compressor housing. This configuration allows the diffuser plate to be secured without additional fixing parts.

[0017] Preferably, guide vanes (or deswirl vanes) are arranged in the diffuser channel to guide the return gas. By adjusting parameters such as the number, shape, and angle of the guide vanes, the swirling velocity of the gas in the diffuser channel can be reduced or eliminated, thereby expanding the operating range of the compressor and improving system efficiency and operational stability.

[0018] Guide vanes are usually arranged in the recirculation section, but they can also be arranged in both the diffuser section and the recirculation section, or only in the diffuser section.

[0019] In various embodiments, the guide vanes are integrally formed with the diffuser plate, or integrally formed with the compressor housing, or even integrally formed with both the diffuser plate and the compressor housing, to reduce gaps or openings for installation, thereby guiding airflow more effectively.

[0020] For example, the first compressor housing may include a first cooling chamber that is sealed and isolated from the diffuser passage. The cooling chamber can cool the air flowing through it to lower its temperature.

[0021] Similarly, the second compressor housing may include a second cooling chamber that is sealed and isolated from the diffuser passage.

[0022] It also includes an expander section, which includes an expander impeller and an expander housing, and is configured to assist the first and second compressor impellers in performing work by utilizing the exhaust energy of the fuel cell generator set. The expander section may also include an additional third compressor impeller, wherein the compressed gas, after being cooled, for example by an intercooler, by the first and second compressor impellers, is delivered to the third compressor impeller to compress the compressed gas.

[0023] Additional features and advantages of the air compressor for fuel cells described herein will be set forth in the detailed description below, and will be recognized by those skilled in the art either by the following description or by practice of the embodiments described herein, including the detailed description below and the accompanying drawings. Attached Figure Description

[0024] With reference to the above objectives, the technical features of the present invention are clearly described in the following detailed description of the embodiments, and its advantages are apparent from the following detailed description with reference to the accompanying drawings, which illustrate preferred embodiments of the invention by way of example, without limiting the scope of the inventive concept.

[0025] Figure 1 A perspective view of an air compressor for a fuel cell according to an embodiment of the present invention is shown.

[0026] Figure 2 A partial cross-sectional view of an air compressor for a fuel cell according to an embodiment of the present invention is shown.

[0027] Figure 3 It shows Figure 2 An exploded view of an air compressor used in fuel cells.

[0028] Figure 4 It shows Figure 2 A partially enlarged view of the air compressor used in fuel cells.

[0029] Figure 5 A schematic diagram of a first compressor impeller for an air compressor for a fuel cell according to an embodiment of the present invention is shown.

[0030] Figure 6 A schematic diagram of a second compressor impeller for an air compressor for a fuel cell according to an embodiment of the present invention is shown.

[0031] Figure 7 A schematic diagram of a diffuser plate for an air compressor for a fuel cell according to an embodiment of the present invention is shown.

[0032] Figure 8 It shows Figure 7 Side view of the diffuser plate.

[0033] Figure 9 A schematic diagram of a second compressor housing for an air compressor for a fuel cell according to an embodiment of the present invention is shown.

[0034] Figure Labels

[0035] 1. Air compressor;

[0036] 10 compressor sections;

[0037] 11. Compressor inlet;

[0038] 12 compressor outlets;

[0039] 20 motor sections;

[0040] 21 rotors;

[0041] 22 First rotation axis;

[0042] 23. Second rotation axis;

[0043] 30 expander section;

[0044] 31 Expander inlet;

[0045] 32 Expander outlet;

[0046] 33. Expander impeller;

[0047] 110 First compressor casing;

[0048] 111 entry components;

[0049] 112 flange;

[0050] 113 Cooling tank;

[0051] 120 Second compressor housing;

[0052] 121 steps;

[0053] 122 Second cooling chamber;

[0054] 130 First compressor impeller;

[0055] 131 Back;

[0056] 140 Second compressor impeller;

[0057] 141. Nose;

[0058] 150 diffuser plate;

[0059] 151 opening;

[0060] 152 Reception Department;

[0061] 160 diffuser channel;

[0062] 161 Diffuser Section;

[0063] 162. Bend section;

[0064] 163 Return Flow Section;

[0065] 164 guide vanes;

[0066] 170 cover parts;

[0067] 200 First sealing ring;

[0068] 300 Second sealing ring. Detailed Implementation

[0069] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention in any way.

[0070] The terms “front” and “back”, or “inlet” and “outlet” as used in this article are defined based on the gas flow path, specifically, the gas will flow through the front or inlet of the component and then through the rear or outlet of the component.

[0071] As used herein, the term "axial" refers to the direction in which the axis of rotation extends. The term "vertical" is used according to this application. Figure 2 The directions shown are used to describe it.

[0072] This invention proposes an air compressor for fuel cells, comprising a compressor section including a first compressor impeller and a second compressor impeller. The first and second compressor impellers are configured to rotate so that gas entering the compressor section flows through the first and second compressor impellers, thereby achieving two compressions of the gas. It is worth noting that the air compressor described in the embodiments of this invention is primarily for hydrogen fuel cells; however, those skilled in the art can apply the air compressor of this invention to other types of fuel cells or generator sets if desired.

[0073] Figure 1 A perspective view of an air compressor 1 for a fuel cell according to an embodiment of the present invention is shown. The air compressor 1 includes a compressor section 10, a motor section 20, and an expander section 30. The compressor section 10 includes a compressor inlet 11 and a compressor outlet 12, and a compressor impeller (…) within the compressor section 10. Figure 1 (Not shown in the diagram) A gas, such as air, enters the compressor section 10 from the compressor inlet 11 and is compressed by the rotation of the compressor impeller. The compressed gas then exits from the compressor outlet 12 and enters the fuel cell intake passage (not shown) for subsequent reactions.

[0074] Figure 2 A cross-sectional view of an air compressor 1 for a fuel cell according to an embodiment of the present invention is shown. As shown, the motor section 20 includes a motor having a rotor 21 and a first rotating shaft 22 fixedly connected to the rotor 21, such that rotation of the rotor 21 drives rotation of the first rotating shaft 22. The first rotating shaft 22 extends at least partially within the compressor section 10 to allow a compressor impeller to be fixedly mounted on the first rotating shaft 22, thereby rotating together with the first rotating shaft 22. It should be understood that the term "rotation" as used herein refers to rotation about the axis of rotation of the rotating shaft.

[0075] Reference Figure 1 and Figure 2 The expander section 30 includes an expander housing with an expander inlet 31 and an expander outlet 32, and an expander impeller 33 inside the expander housing. Exhaust gas or waste gas from the generator set, exiting the fuel cell after the reaction, enters the expander section 30 through the expander inlet 31 to drive the expander impeller 33 to rotate. The motor section 20 includes a second rotating shaft 23 fixedly connected to the rotor 21 and extending at least partially within the expander section 30 and coaxially. The expander impeller 33 is fixedly mounted on the second rotating shaft 23, thus rotating together with it. Therefore, the fuel cell exhaust can promote the rotation of the second rotating shaft 23 and thus the rotor 21 to assist the compressor impeller in performing work, thereby helping to reduce the power consumption of the motor.

[0076] In the embodiment shown in the figure, the air compressor 1 maintains a design substantially the same as that of a conventional air compressor used in fuel cells, with changes made only to the compressor section. Therefore, the motor section 20 and the expander section 30 will not be described further below. Note that the air compressor shown in the figures is merely an example and not a limitation, and modifications to the motor section and expander section are permissible by those skilled in the art.

[0077] Continue to refer to Figure 2 and combined Figures 3-4 The compressor section 10 includes a first compressor housing 110 and a second compressor housing 120. The first compressor housing 110 forms the compressor inlet 11 of the compressor section 10, and the second compressor housing 120 forms the compressor outlet 12 of the compressor section 10. A tapered inlet member 111 is provided within the first compressor housing 110 near the compressor inlet 11 to guide gas into the compressor section 10. The first compressor housing 110 and the second compressor housing 120 can be assembled together axially, for example, by a threaded connection. The second compressor housing 120 can also be fixedly mounted to the motor section 20, for example, by a threaded connection. Advantageously, a first sealing ring 200 is inserted between the first compressor housing 110 and the second compressor housing 120 to prevent gas from escaping between the two housings. It should be understood that the form of the compressor section 10 is not limited to that described herein, and in other embodiments, the compressor section may be integrally formed or may be assembled from more than two (e.g., three or more) housing portions. It should also be understood that although the first compressor housing 110 and the second compressor housing 120 are assembled in the axial direction to form the compressor section 10, other assembly methods may be included within the scope of the invention. For example, the compressor housing may be two halves of the same shape and may be assembled together in a direction perpendicular to the axial direction.

[0078] Reference Figures 2-4 and additionally refer to Figure 5 The compressor section 10 includes a first compressor impeller 130 (also referred to as a low-pressure stage impeller), which is mounted on the rotor 21 via a mating connection between parts and is fixedly locked to the rotor 21 by a first rotating shaft 22 to rotate together with the rotor 21. The first compressor impeller 130 has an axial inlet near its central portion for gas intake and a radial outlet at its outer peripheral portion for gas discharge. The first compressor impeller 130 has a tapered shape; specifically, the inlet diameter of the first compressor impeller 130 increases towards the outlet diameter (from...). Figure 5 The diameter increases from left to right (as seen in the image), causing the gas entering the compressor section to flow through the rotating first compressor impeller 130 to undergo the first compression. The blade shape of the first compressor impeller 130 is known to those skilled in the art and will not be described further herein.

[0079] Continue to refer to Figures 2-3 and additionally refer to Figure 6 The compressor section 10 includes a second compressor impeller 140 (also referred to as a high-pressure stage impeller), which is also mounted on the rotor 21 via a mating connection between parts and is fixedly locked to the rotor 21 by a first rotating shaft 22 to rotate together with the rotor 21. Similar to the first compressor impeller 130, the second compressor impeller 140 has an inlet and an outlet and has a tapered shape; specifically, the inlet diameter of the second compressor impeller 140 increases towards the outlet diameter (from...). Figure 6 (Viewed from left to right, the diameter increases), causing the gas flowing through the first compressor impeller 130 to then flow through the rotating second compressor impeller 140 for a second compression. The blade shape of the second compressor impeller 140 is also known and will not be described further here. The gas after the two compressions can then leave the compressor section 10.

[0080] Preferably, the first compressor impeller 130 and the second compressor impeller 140 are arranged such that the back 131 of the first compressor impeller 130 (see also) Figure 5 (See also) The nose 141 of the second compressor impeller 140 (see also) Figure 6Arranging the first compressor impeller 130 and the second compressor impeller 140 abutting each other enables a compact design of the entire device, reducing the overall size of the device and facilitating its layout. It should be understood that while the foregoing and accompanying drawings provide one arrangement of the first compressor impeller 130 and the second compressor impeller 140, this arrangement is not limiting. For example, in another embodiment, the first compressor impeller and the second compressor impeller can be arranged back-to-back. In yet another embodiment, the first compressor impeller and the second compressor impeller can be arranged spaced apart from each other. These and other arrangements are also within the scope of this invention.

[0081] As shown in the figure, in an embodiment of the present invention, the outlet diameter of the first compressor impeller 130 is larger than the outlet diameter of the second compressor impeller 140, so that the first compressor impeller 130 can provide a larger gas flow rate while ensuring the high efficiency of the second compressor impeller 140. Of course, those skilled in the art can adjust various diameters of the first compressor impeller 130 and the second compressor impeller 140 according to requirements. For example, the outlet diameter of the first compressor impeller 130 can be equal to or even smaller than the outlet diameter of the second compressor impeller 140. These are all within the scope of the present invention.

[0082] During gas compression, the compressor impeller performs work on the gas, which is converted into the kinetic energy of the gas molecules. This causes the average molecular velocity to increase, macroscopically manifested as a rise in temperature. The increased thermal motion of oxygen molecules in the gas leads to volume expansion, reducing the number of molecules per unit volume and decreasing density. The significant increase in gas volumetric flow rate and velocity due to the temperature rise results in a substantial decrease in system efficiency and necessitates higher material quality requirements. Therefore, cooling of the compressed gas must be considered.

[0083] Reference Figures 2-4 and additionally refer to Figure 7 In a preferred embodiment of the invention, the air compressor 1 for the fuel cell further includes a diffuser plate 150, which is installed within the compressor section 10 between the first compressor impeller 130 and the second compressor impeller 140, such that the diffuser plate 150 and the compressor section 10 together form a diffuser channel 160. This diffuser channel 160 is used for decelerating and pressurizing the compressed gas and guiding gas flow to ensure that the compressed gas can flow smoothly through the second compressor impeller 140. Furthermore, after the gas flows through the first compressor impeller 130 and is initially compressed, the compressed gas can flow along the diffuser channel 160. Specifically, refer to... Figures 7-8The diffuser 150 is substantially disc-shaped, and the dimensions (e.g., diameter) of the disc are designed to be received within the compressor section 10 with the largest diameter in a vertical plane perpendicular to the axial direction. The diffuser 150 has an opening 151 near its outer edge for gas flow. Thus, the diffuser 150 and the compressor section 10 define a diffuser passage 160 with a U-shaped bend.

[0084] In the illustrated embodiment, at least a portion of the diffuser plate 150 can be clamped between the first compressor housing 110 and the second compressor housing 120 to secure the diffuser plate 150. Specifically, the first compressor housing 110 may include a flange 112 in the axial direction, and the second compressor housing 120 may include a step 121 in the axial direction. When the first compressor housing 110 and the second compressor housing 120 are assembled together, the flange 112 and the step 121 can engage to form a recess in the vertical direction. (Refer to...) Figure 4 as well as Figures 7-8 The diffuser plate 150 has receiving portions 152 at its outer periphery, which can be received by recesses formed by the flange 112 and the step 121 (e.g. Figure 2 As shown, since the first compressor housing 110 and the second compressor housing 120 are assembled together in the axial direction, they are close to each other in the axial direction, thereby clamping the receiving portion 152 between the housings, which achieves the fixation of the diffuser plate 150. It should be understood that the method of fixing the diffuser plate 150 is not limited to this. For example, in an embodiment where the compressor housing is integral, the diffuser plate can be integrally formed with the compressor housing of the compressor section.

[0085] Reference Figure 4 The diffuser passage 160 is curved, extending from the outlet of the first compressor impeller to the inlet of the second compressor impeller. Specifically, the diffuser passage 160 includes a diffuser section 161, a curved section 162, and a recirculation section 163. The diffuser section 161 guides the compressed gas exiting the outlet of the first compressor impeller 130 to the opening 151 of the diffuser plate 150. The curved section 162 changes the airflow direction exiting the outlet of the first compressor impeller 130, and the opening 151 in the curved section 162 is substantially axial, allowing the compressed gas to flow through the opening 151. The recirculation section 163 guides the compressed gas flowing through the opening 151 to the inlet of the second compressor impeller 140 to achieve gas recirculation, that is, the compressed gas first flows radially away from the rotation axis in the diffuser passage 160, and then flows toward the rotation axis. The cross-sectional dimension at the outlet of the diffuser section 161 is preferably larger than that at the inlet to diffuse the compressed gas and thereby reduce its flow rate.

[0086] Preferably, guide vanes 164 are arranged within the diffuser channel 160, and more preferably within the recirculation section 163, for guiding the recirculating gas. It should be noted that the guide vanes 164 can be arranged within the recirculation section 163, or they can be arranged simultaneously in the diffuser section 161 and the recirculation section 163, or only within the diffuser section 161. (Refer to...) Figure 9 The guide vanes 164 are arranged circumferentially around the center of rotation. The number, shape, and angle of the guide vanes 164 can be designed to reduce the swirling velocity of the gas in the diffuser channel 160 before the inlet of the second compressor impeller 140, thereby expanding the compressor's operating range and improving system efficiency and operational stability. Figure 9 In the illustrated embodiment, the guide vane 164 is integrally formed with the second compressor housing 120 to reduce installation gaps or openings, thereby more effectively guiding airflow. In other embodiments, the guide vane may alternatively be integrally formed with the diffuser or with the first compressor housing. In yet another embodiment, the guide vane may be integrally formed with multiple components in the diffuser, the first compressor housing, and the second compressor housing (e.g., some guide vanes are integrally formed with the diffuser, and other guide vanes are integrally formed with the compressor housing).

[0087] The design of the diffuser channel 160 and the guide vanes 164 helps to slow down the compressed gas in the diffuser channel 160, thereby reducing the temperature of the compressed gas. At the same time, the flow straightening effect of the guide vanes reduces gas swirling, thereby improving gas flow efficiency and expanding the operating range of the second-stage compressor impeller.

[0088] It should be understood that the shapes of the diffuser plate 150 and the compressor section 10 can be designed to define diffuser channels 160 of different shapes, as long as they can achieve the functions of diffuser, guide and cool compressed gas.

[0089] Reference Figures 2-4 To effectively cool the compressed fluid, the first compressor housing 110 and the second compressor housing 120 include cooling chambers, namely a first cooling chamber and a second cooling chamber 122, which are sealed and isolated from the diffuser passage 160. In the embodiment shown in the invention, the first cooling chamber is formed by a cooling groove 113 and a cover 170 (e.g., by a threaded connection), and is sealed between the cooling groove 113 and the cover 170 by a second sealing ring 300. In other embodiments, the first cooling chamber may also be formed directly in the first compressor housing 110. By adding coolant to the first and second cooling chambers 122, the gas is cooled to increase its density as it flows through the cooling chambers, thereby increasing the oxygen density.

[0090] Although in a preferred embodiment of the invention both the first compressor housing 110 and the second compressor housing 120 include a cooling chamber, in other embodiments only one of the first compressor housing 110 and the second compressor housing 120 or none at all, a cooling chamber may be provided.

[0091] Furthermore, it is worth noting that although two compressor impellers—a first compressor impeller 130 and a second compressor impeller 140—are used in the preferred embodiment of the invention to achieve a higher gas density, this is merely an example and not a limitation. In additional embodiments of the invention, more than two compressor impellers may be included, for example, three. These compressor impellers may all be mounted within the compressor section, or some of the compressor impellers may be mounted outside the compressor section. As an example, an additional compressor impeller may be included in the expander housing of the expander section, wherein the compressed gas passed through the first and second compressor impellers, after being cooled, for example, by an intercooler, is delivered to the expander section via an additional delivery pipe, reaching the additional third compressor impeller, for more thorough compression of the compressed gas. Advantageously, the expander section includes the expander impeller as described above, wherein the back of the additional compressor impeller may abut against the back of the expander impeller, and the compressor impeller and the expander impeller rotate together with the rotor by a second rotating shaft.

[0092] This invention designs an air compressor with a two-stage compression function, wherein the outlet of the low-pressure impeller within the compressor section is connected to the inlet of the high-pressure impeller. This compressor functions to diffuse, guide, and cool compressed air. The compressor housing provides additional cooling, regardless of whether a cooling circuit is provided. The air compressor does not use external connections to link the two stages; instead, it improves system efficiency solely through the two stages within the compressor section, and this design is very compact and economical.

[0093] While the structure of the present invention has been described above with reference to preferred embodiments, those skilled in the art should recognize that the above examples are merely illustrative and should not be construed as limiting the invention. Therefore, modifications and variations can be made to the present invention, all of which will fall within the scope defined by the appended claims.

Claims

1. An air compressor for a fuel cell, comprising a compressor section having a compressor inlet and a compressor outlet, the compressor inlet configured to receive gas into the compressor section, and the compressor outlet configured to discharge compressed gas from the compressor section. Its features are, The compressor section includes: A first compressor impeller, mounted within the compressor section, is rotatable to compress air; and A second compressor impeller is installed within the compressor section and further away from the compressor inlet than the first compressor impeller. This second compressor impeller is capable of rotation to compress air. The first compressor impeller and the second compressor impeller are configured to allow gas entering the compressor section to flow through the first compressor impeller and the second compressor impeller, thereby compressing the gas twice.

2. The air compressor for a fuel cell as described in claim 1, characterized in that, It also includes a rotating shaft that extends at least partially within the compressor section, and the first compressor impeller and the second compressor impeller are fixedly mounted on the rotating shaft to rotate together with the rotating shaft.

3. The air compressor for a fuel cell as described in claim 1, characterized in that, The first compressor impeller and the second compressor impeller are arranged such that the back of the first compressor impeller abuts against the nose of the second compressor impeller.

4. The air compressor for a fuel cell as described in claim 3, characterized in that, The outlet diameter of the first compressor impeller is larger than the outlet diameter of the second compressor impeller.

5. The air compressor for a fuel cell as described in claim 1, characterized in that, It also includes a diffuser plate, which is installed in the compressor section between the first compressor impeller and the second compressor impeller, so that the diffuser plate and the compressor section define a diffuser channel.

6. The air compressor for a fuel cell as described in claim 5, characterized in that, The diffuser plate is integrated with the compressor section.

7. The air compressor for a fuel cell as described in claim 5, characterized in that, The diffuser channel is a curved channel that extends from the outlet of the first compressor impeller to the inlet of the second compressor impeller, and includes a diffuser section, a curved section, and a recirculation section.

8. The air compressor for a fuel cell as described in claim 5, characterized in that, The compressor section includes a first compressor housing and a second compressor housing, which are assembled together, wherein at least a portion of the diffuser plate is sandwiched between the first compressor housing and the second compressor housing.

9. The air compressor for a fuel cell as described in claim 8, characterized in that, Guide vanes are arranged in the diffuser channel, and the guide vanes are configured to reduce or eliminate the swirling velocity of the gas in the diffuser channel.

10. The air compressor for a fuel cell as described in claim 9, characterized in that, The diffuser channel includes a diffuser section and a recirculation section, wherein the guide vanes are arranged in at least one of the diffuser section and the recirculation section of the diffuser channel.

11. The air compressor for a fuel cell as claimed in claim 10, characterized in that, The guide vane is integrally formed with at least one of the diffuser plate, the second compressor housing, and the first compressor housing.

12. The air compressor for a fuel cell as described in claim 8, characterized in that, The first compressor housing includes a first cooling chamber, which is sealed and isolated from the diffuser channel.

13. The air compressor for a fuel cell as described in claim 8, characterized in that, The second compressor housing includes a second cooling chamber, which is sealed and isolated from the diffuser channel.

14. The air compressor for a fuel cell as claimed in claim 1, characterized in that, It also includes an expander section, which includes an expander impeller and an expander housing, and is configured to assist the first compressor impeller and the second compressor impeller in doing work by utilizing the exhaust energy of the fuel cell generator set, wherein the expander section also includes a third compressor impeller, wherein the compressed gas passing through the first compressor impeller and the second compressor impeller is delivered to the third compressor impeller after cooling to compress the compressed gas.

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