Air supply device for fuel cell system and fuel cell system

Abstract

The invention relates to an air supply device (1) for a fuel cell system (2, 3), having a flow compressor and a drive motor (4) for the flow compressor, wherein the flow compressor has two compressor wheels (6, 7) which are configured to be substantially symmetrical and are arranged on a common shaft (5) together with the drive motor (4) arranged between the two compressor wheels. The air supply device according to the invention is distinguished in that the two compressor wheels (6, 7) are connected on the pressure side to two systems (2, 3, 10, 13) which are connected aerodynamically non-permanently. Furthermore, a fuel cell system (2, 3) using such an air supply device (1) is claimed.

Description

Technical Field

[0001] The present invention relates to an air supply device for a fuel cell system and a fuel cell system supplied by the air supply device, the air supply device having a flow compressor and a drive motor for the flow compressor, wherein the flow compressor has two compressor impellers configured to be substantially symmetrical and arranged on a common shaft together with the drive motor disposed between the two compressor impellers. Background Technology

[0002] Fuel cell systems are already known in existing technology. For the air supply of fuel cell systems, partially electrically driven flow compressors / centrifugal air compressors are often used. Very frequently, a turbine is positioned on one side of the electric motor, and a compressor on the other. This configuration, also known as an electric turbocharger or motor-assisted turbocharger, is commonly used because it can recover residual energy from the exhaust. However, a drawback of this configuration is the uneven loading of the axial support, as the forces acting in the compressor region and the turbine region differ significantly. This results in higher friction in the axial support region. Consequently, a very complex and expensive axial support system is required, and even then, undesirable high power losses are almost unavoidable in the axial support region.

[0003] Other structures can also be constructed as two-stage compressors with an electric motor and two compressor wheels on the same shaft. For this purpose, see DE 10 2010 035 725 A1 for an example. Here, the load on the axial support device is also relatively large due to the different pressure conditions and forces on the sides. In the aforementioned document, this is attempted to be compensated accordingly by the components following the compressor wheels.

[0004] This type of WO 2019 / 096890 A2 addresses this force imbalance by arranging two symmetrical compressor wheels and the drive motor together on a common shaft. This significantly reduces axial forces. Consequently, a smaller axial support device and very low friction are achieved in the area of ​​this axial support device.

[0005] Furthermore, as another prior art, reference can be made to the applicant’s DE 101 20 947A1, which describes a combination of an electrically driven flow compressor and a so-called no-load turbocharger, i.e., a no-load turbocharger having a turbine on one side and a compressor on the other side. Summary of the Invention

[0006] The object of the present invention is to provide an improved air supply device of the type described at the beginning for a fuel cell system, and an improved fuel cell system using the air supply device.

[0007] According to the present invention, this objective is achieved by an air supply device for a fuel cell system having the following characteristics. Furthermore, this objective is achieved by a fuel cell system having the following characteristics.

[0008] Similar to existing technologies, the air supply device for a fuel cell system is configured to include a flow compressor driven by a drive motor. Here, the flow compressor has two compressor impellers, which are configured to be substantially symmetrical and arranged on a common shaft together with the drive motor disposed between them. According to the invention, the two compressor impellers are connected to two pneumatically non-permanently connected systems.

[0009] A flow compressor with two substantially symmetrical compressor wheels, implemented in the same manner as described in existing technologies of this type, significantly unloads the axial support, simplifying its structure and reducing friction. In fuel cell applications in the vehicle sector, and at typical power levels here, power losses up to 2 kW can be avoided. A key advantage of using the airflow generated where the compressor wheels are connected on the pressure side to two different systems—two systems that are not pneumatically connected or at least not permanently pneumatically connected—is that only a portion of the heat is introduced into both systems, heat that would otherwise be shared within the assembly when converging in the air ducts on the pressure side, potentially leading to thermal overload of the assembly very quickly in a fuel cell system.

[0010] The air supply device according to the invention is particularly suitable for arranging two separate fuel cell systems, according to a very advantageous improvement of the air supply device, by supplying air to the fuel cell systems through a common air supply device. For example, the separate fuel cell systems can be two systems of the same type, for example, combined in a modular structure to provide the drive power required for a commercial vehicle. It is also desirable to contemplate, in any other form, the joint supply of air to the fuel cell system and another system requiring air.

[0011] According to a highly suitable improvement of the air supply device according to the invention, two non-permanently pneumatically interconnected systems are the compressor side and turbine side of an unloaded turbocharger. Thus, the air supply device, having two symmetrical compressor impellers, supplies air to the compressor side of the unloaded turbocharger through one compressor impeller, and to the turbine of the unloaded turbocharger through the other compressor impeller. This essentially produces staged pressurization, in which an electrically driven flow compressor provides, for example, a pressure level of 1.5 bar to 2.5 bar. This pressure then reaches the compressor side of the unloaded turbocharger from the compressor impeller, where the compressor side continues to increase the pressure, for example, to 4.5 bar for supplying the fuel cell system. For this purpose, the volumetric flow of the other compressor impeller reaches the turbine side of the unloaded turbocharger, thereby providing the energy required to drive the compressor side and to increase the pressure. This structure is extremely simple and advantageous. In particular, the unloaded turbocharger can be designed such that it could potentially freeze due to the presence of very humid gas (which may be supplied to the unloaded turbocharger) in the fuel cell system. Of course, it is now possible to blow air to the fuel cell system via an electrically driven compressor wheel through the compressor side of an unloaded booster, which is at least sufficient to start the fuel cell system and subsequently melt it.

[0012] According to another highly advantageous design, pneumatically non-permanently connected systems can be connected in a controllable manner via a bypass line equipped with a valve. This controllable connection, in two other cases of non-permanently connected systems, enables, for example, the provision of a large volumetric flow at low pressures, particularly for structures with an additional no-load booster according to the aforementioned variant. Thus, especially for such structures, with the bypass line closed and consequently the drive power on the turbine side of the no-load booster correspondingly high, a relatively high pressure can be achieved with a correspondingly smaller volumetric flow. If the valve in the bypass line is further opened, more air reaches the compressor side and less reaches the turbine side, thereby achieving a larger volumetric flow at even lower pressures.

[0013] In a variant implementation with an unloaded supercharger, a temperature rise occurs in the compressor, specifically in both compression stages. This is undesirable because such a temperature rise consequently loads the fuel cell system. Conversely, it is desirable to keep the input air to the fuel cell system humid to prevent it from drying out. For this reason, an advantageous design according to this idea specifies the provision of a means for conveying liquid in the flow direction before and / or after the compressor side into the compressed air stream, said means having, in particular, at least one nozzle for atomizing the liquid in the compressed air stream. An advantageous design according to this idea, through the introduction of liquid, particularly deionized water, via the nozzle for atomizing the liquid, reduces the temperature of the compressed air stream on the one hand, because the liquid in the air stream evaporates accordingly, and on the other hand, humidifies the air stream. This achieves two important advantages. On the one hand, when the liquid is introduced before the compressor side, the efficiency on the compressor side is improved, and on the other hand (in both designs), humidification of the fuel cell input air is ensured. Therefore, a complex, compact device for humidifying the input air, which places high space requirements within a fuel cell system, can be realized using a simple water reservoir. The reservoir can also collect and reuse condensate when necessary, and a corresponding device for delivering water into the compressed air stream is also implemented. This structure can be integrated into air supply equipment very simply, cost-effectively, and space-savingly.

[0014] Furthermore, a highly suitable improvement to the air supply device according to the invention can be specified that the unloaded turbocharger is supported by hydrodynamic pressure. This hydrodynamic support device / bearing can be extremely simple and effective, and reduces friction generated during rapid turbocharger operation. Particularly suitable here is the use of water, such as water used for humidification of the system in the above-described design, either carried or recovered from the system, to achieve the hydrodynamic support of the unloaded turbocharger.

[0015] Here, an unloaded turbocharger is particularly well-suited for use in achieving hydrodynamic support. Although leakage occurs between the support components and vented or compressed air is released, this is relatively minor because in the case of vented air, the air is no longer used, thus moisture has no effect. Similarly, in the case of input air, humidification is undoubtedly performed immediately afterward, so moisture is also unaffected, and even necessary. This is a decisive difference compared to, for example, electrically driven compressors, which, when supported by hydrodynamic water, may become moist in areas of electronics or electronic devices when not sealed, potentially leading to serious short-circuit risks and being a significant disadvantage.

[0016] According to the invention, a fuel cell system having at least one fuel cell can be configured to supply air to the fuel cell using at least a portion of the air from the air supply device according to the invention. Therefore, the fuel cell system can use the air supply device alone, or in conjunction with another fuel cell system, or also with other systems, to obtain its compressed and ideally humidified input air.

[0017] A highly suitable improvement to this fuel cell system, having at least one fuel cell (with an anode and a cathode side) and an air supply device with an unloaded turbocharger, can further specify that the cathode-side outlet is selectively or partially connected to the environment and / or to a recirculation line in a controllable manner, wherein the recirculation line leads between one of the compressor impellers and the compressor side of the unloaded turbocharger. Therefore, in this design of the fuel cell system, the unloaded turbocharger is used for the recirculation of the cathode exhaust gas, which is fully or particularly partially recirculated and circulated through the compressor side of the unloaded turbocharger. Consequently, the moisture carried by the cathode exhaust gas, as a reaction product in the fuel cell, is also introduced into the compressed input air. This eliminates the need for a complex humidifier and reduces or even eliminates the injection of liquid into the compressed air stream. Furthermore, the recirculation rate of the oxygen-removed exhaust air from the cathode side can be used to reduce the oxygen content in the cathode under almost no load. This prevents excessively high cell voltage in the fuel cell and the resulting cell damage.

[0018] In addition, or alternatively, another very suitable design for a fuel cell system may specify the recirculation of anode exhaust gas, at least in part, via a recirculation blower.

[0019] This principle is already known from the prior art. A variant of the fuel cell system according to the invention further specifies that the recirculation blower has an exhaust air turbine, which is connected to the recirculation blower and driven by the exhaust air from the fuel cell system, particularly the cathode exhaust air. Thus, this exhaust air turbine (in a very advantageous improvement according to this idea, the exhaust air turbine is magnetically connected to the recirculation blower) utilizes the residual energy in the fuel cell exhaust to drive the recirculation blower. This ideally utilizes the introduced aerodynamic energy. Especially in the design of the magnetic connection between the exhaust air turbine and the recirculation blower, the hydrogen-guiding side of this structure is kept separate from the air-guiding side, allowing for reliable sealing between the two sides and eliminating concerns about uncontrolled hydrogen leakage into the exhaust air. Attached Figure Description

[0020] Advantageous designs and improvements of the air supply device and the fuel cell system according to the invention are obtained from the embodiments described in detail below with reference to the accompanying drawings. Wherein:

[0021] Figure 1 An air supply device according to the invention, based on a first feasible embodiment, is shown;

[0022] Figure 2 An air supply device according to the invention, based on a second feasible embodiment, is shown;

[0023] Figure 3 This illustrates an alternative design scheme, based on... Figure 2 The present invention relates to an air supply device;

[0024] Figure 4 It shows that it has the following characteristics: Figure 2 A feasible implementation of a fuel cell system with an air supply device of type 3;

[0025] Figure 5 This illustrates an improved version based on an alternative, and... Figure 4 Similar fuel cell systems are shown;

[0026] Figure 6 It shows that according to Figure 5 A partial view of the image, which illustrates an exemplary system for utilizing water in a fuel cell system. Detailed Implementation

[0027] exist Figure 1 The view shows an air supply device 1 for fuel cell systems 2 and 3. The air supply device mainly consists of a drive motor 4, which is arranged on a common shaft 5 along with two compressor wheels 6 and 7. The compressor wheels 6 and 7 are driven by the drive motor 4, which is centrally located between them on the shaft 5 and designed to be substantially symmetrical. This minimizes the axial force acting on the common shaft 5. This helps reduce frictional power loss and also allows for a simple and efficient design of the axial support device. Air is drawn in by the compressor wheels 6 and 7 through two separate or optionally common intake paths 8, as shown by dashed lines. The air is supplied to fuel cell system 2 by compressor wheel 6 and to fuel cell system 3 by compressor wheel 7.

[0028] Here, fuel cell systems 2 and 3 are constructed independently of each other; for example, they can be implemented as identical fuel cell systems 2 and 3, used to provide driving power in commercial vehicles. The fuel cell system can, for example, be designed in the same form as a single fuel cell system used solely for driving passenger vehicles, thus effectively using this fuel cell system in a dual manner in commercial vehicles, and supplying air through a single, identical air supply device 1. As mentioned above, a common intake pipe 8 can be provided, thus requiring only a common air filter (not shown) in the intake pipe. It is also desirable to conceive of providing two separate air filters and intake pipes 8.

[0029] exist Figure 2 An alternative design for the air supply device 1 can be seen in the view. The air supply device 1 is basically constructed as described in... Figure 1 The same situation described above applies. The air supply device includes a drive motor 4 and two compressor impellers 6 and 7. The compressor impellers 6 and 7 are connected to the environment via two separate air supply lines 8 and draw in air accordingly. The air is compressed in the two compressor impellers 6 and 7 by means of the drive motor 4. The compressed air travels from the compressor impeller 6 through a staged line 9 to the compressor side 10 of the unloaded turbocharger 11 (also called the unloaded supercharger 11). In the unloaded supercharger 11, a common shaft 12 connects the compressor side 10 to the turbine side 13, which is connected to the pressure side of the compressor impeller 7 of the air supply device 1 and is driven accordingly by the airflow through the compressor impeller 7. After the turbine side 13, specifically its turbine, the expanded air that previously traveled from the compressor impeller 7 to the turbine side 13 of the unloaded supercharger 11 via the turbine line 14 flows out again. Now, more strongly compressed input air travels from the compressor side 10 of the unloaded supercharger 11 to the compressor side 10. Figure 2 The fuel cell systems 2 and 3 are schematically shown in the view. Therefore, this structure enables the use of the unloaded booster 11 to generate the pressure required for the fuel cell systems 2 and 3 on the compressor side 10 of the unloaded booster 11, starting from the pressure generated by the compressor wheel 6, which serves as the first compressor stage. That is, it involves a staged boosting configuration.

[0030] exist Figure 3 The view shows another variant, which is understood as... Figure 2The views are essentially similar. Additionally, a bypass line 15 with valve 16 is provided, which guides a portion of the air already compressed by the compressor wheel 7 of the air supply device 1 from the turbine line 14 to the stage line 9. Thus, for example, when valve 16 is fully or partially open, a larger volumetric flow of air can reach the fuel cell systems 2 and 3. Simultaneously, the airflow through the turbine side 13 of the no-load booster 11 is correspondingly reduced, resulting in a lower pressure in the fuel cell systems 2 and 3 despite the larger volumetric flow. As valve 16 in the bypass line 15 further closes, the power on the turbine side 13 and consequently the compressor power on the compressor side 10 of the no-load booster 11 increases accordingly, while the volumetric flow decreases. This allows for higher pressure with a smaller volumetric flow. Therefore, the air supply can be controlled by valve 16 in the bypass line 15. While the bypass line 15 with valve 16 provides particular advantages, it is hereby understood only as optional and, in principle, can be omitted, as already provided... Figure 2 As explained in the view.

[0031] This is independent of the bypass line 15, and can therefore also be applied to... Figure 2 In the structure, a water reservoir 17 is now also shown, which is connected to the compressed input air flow reaching the fuel cell systems 2 and 3 via one or alternatively two water lines 18, 18'. Thus, liquid water can be introduced into the compressed volumetric flow, preferably atomized therein, by means suitably configured to deliver liquid water at the ends of the water lines 18 and / or 18'. Accordingly, the hot compressed air volumetric flow following the compressor wheel 6 or compressor side 10 is thereby cooled on the one hand and humidified on the other. Both aspects are advantageous for the operation of the fuel cell systems 2 and 3, since the temperature of the input air flowing to the fuel cell systems 2 and 3 should be substantially no greater than about 70°C, and since the input air should be humidified as much as possible. If this humidification is achieved by delivering water at this location, complex humidifiers, such as gas / gas humidifiers (which are currently the norm), can be eliminated, or at least their size can be reduced. This saves large and complex components, which is a significant advantage not only in terms of cost and system complexity but also in terms of space requirements. As will be explained later Figure 6 Another application scenario for the water collected in the water tank 17 is seen in the view.

[0032] exist Figure 4 The view shows, for example, detailed fuel cell systems 2 and 3, illustrating some components of the fuel cell systems. The structures of the air supply unit 1 and the no-load booster 11 are substantially corresponding to those of the fuel cell systems. Figure 3Fuel cell systems 2 and 3 include fuel cell 19, which is typically a stack of single-cell fuel cells. Surrounding the fuel cell stack or fuel cell pile 19, for example, an anode side 20 and a cathode side 21 are shown. Air is supplied to the cathode side 21 via an air supply device 1 and an idle-load booster 11 through an input air line 22. Exhaust air reaches a valve device indicated by 24 via an exhaust air line 23, which may also be referred to as an exhaust return valve 24. Exhaust air from the exhaust air line 23 can be selectively or proportionally guided, through the valve device 24, entirely or partially, back into the cascade line 9 via the exhaust air return line 25, or guided into the environment via a section of the exhaust air line 23 indicated by 23'.

[0033] Hydrogen from the high-pressure gas storage tank 26 is supplied to the anode side 20. This hydrogen reaches the anode side 20 via a pressure regulating and metering device 27 and an optional gas jet pump 28. Exhaust gas from the anode side 20 is returned to the gas jet pump 28 via a recirculation line (denoted by 29) in which a water separator 30 may be arranged, if the gas jet pump is present. In the recirculation line 29, a recirculation blower 31 may be arranged as an alternative to or supplement to the gas jet pump 28 in a known manner. Here, a so-called venting valve or venting valve is arranged in the water separator 30 or alternatively in another area of ​​the recirculation line 29, through which gas from the recirculation line 29 is discharged, if necessary, along with water from the water separator 30, for example, time-dependently, based on the hydrogen concentration in the recirculation line 29, or also based on other parameters. The gas reaches the exhaust air line 23, and here it selectively either reaches the region 23' of the exhaust air line, or, as optionally indicated, also reaches the region of the exhaust air line 23 before the exhaust return valve 24 in the direction of exhaust air flow.

[0034] Now, in this structure of fuel cell systems 2 and 3, exhaust air is completely or partially redirected through exhaust air return line 25 at the corresponding position of valve device 24, thereby assisting in the humidification of the input air in the input air line 22 leading to the cathode side 21 of fuel cell 19. As used in... Figure 3The water reservoir 17, as shown in the view, serves as a replacement or supplement, which can contribute to the complete or partial elimination of conventional humidifiers. Currently, there is a risk of moisture reaching the area of ​​the idle compressor 11. This could potentially cause the idle compressor 11 to freeze in the event that the system stops operating at temperatures below freezing. However, unlike the freezing of the air supply unit 1, this is relatively minor because sufficient air is supplied through the compressor wheel 6 and, if necessary, through the compressor wheel 7 when the bypass valve 16 is open, and blown into the input air line 22 through the compressor side 10 of the idle compressor, in order to start the fuel cell systems 2, 3. Therefore, it is possible to restart operation when the idle compressor 11 melts. Thus, in addition to optimal operation with high controllability of the pressure and volumetric flow of the supplied air, the structure with the combination of air compressor 1 and idle compressor 11 further eliminates the need for a humidifier, as exhaust gas recirculation is achieved without the risk of the entire air supply unit 1 freezing at temperatures below freezing.

[0035] Unlike conventional electric turbochargers (where pressure energy is released in fuel cell systems 2, 3 and additionally used to assist, for example, the drive of air supply device 1), in accordance with... Figure 4 In the structure, this pressure is now lost. To prevent this, it is feasible to, as in... Figure 5 The structure is improved as shown in the view. Here, the structure basically corresponds to... Figure 4 The structure is shown in the figure, where, for simplicity, the water separator 30 and the anode exhaust outlet pipe are omitted. Figure 5 In the view, the gas jet pump 28 is no longer present, and of course, this is undoubtedly optional. Instead of the normally electrically driven recirculation blower 31, the exhaust air from the cathode side 21 of the fuel cell 19 now flows through the exhaust air turbine 32 arranged in the exhaust air duct 23, which is connected to the recirculation blower 31 in a power transmission manner, indicated here by a common shaft 33. This allows the recirculation blower 31 to be driven by the energy contained in the exhaust air from the cathode side 21 of the fuel cell 19, thereby recovering this energy and further improving the overall system efficiency. Here, it is particularly suitable to make a magnetic connection between the exhaust air turbine 32 and the recirculation blower 31. This allows the two volumetric flows, namely hydrogen or hydrogen-containing gas and air, to be guided simply in a manner thermally isolated from each other.

[0036] Here, it is clear that all the described implementation variations can be combined with each other, thereby achieving... Figure 3 , 4 In the implementation variant of 5, the bypass pipe 15 can also be omitted, or correspondingly... Figure 2 ,4 In a variant of implementation 5, a water storage tank 17 with water pipes 18, 18' can be additionally provided. Here, for example, in... Figure 2 The structure subsequently shown in the view is particularly suitable for supplying air to a single fuel cell system 2, 3. In the case of using multiple fuel cell systems, Figure 1 The structure in [the original text] is more suitable, or in [the context of the original text] Figure 2 The structures shown later can exist in multiple ways, just like the fuel cell systems 2 and 3 themselves.

[0037] For example, water recovered from the system can be used to fill the already described water storage tank 17. Typically, fuel cell systems 2, 3 have a water separator, for example, in the recirculation line 29, which can... Figure 4 As can be seen in the view, and if necessary, another water separator can also be present in the area of ​​the exhaust air duct 23. As described above, water from the water separator can be supplied to the water storage tank 17. Now, according to a suitable design, this can be constructed in the form of an isolated water tank 170, or (as shown) connected to a water tank. Figure 6 In the view, the water tank is shown in dashed lines. The entire water system connected to the water tank 170 is shown here in dashed lines. Water is heated in the water tank 170. This can be achieved, for example, by electric heating, or supplementally or alternatively, by using the waste heat from the fuel cell systems 2, 3 for heating. In particular, the waste heat present in the exhaust air of the turbine 13 of the unloaded turbocharger 11 can be used to heat the water tank 170 accordingly. Ideally, the water stored therein has a temperature of about 80°C, and the water tank 170 has a heat insulation section 171. Water from the water tank 170 is then guided by a water pump 172 to a pressurized water distributor 173, for example, in the form of a so-called common rail. Subsequently, individual water lines branch off from the system under the corresponding pressure, where, here, water has already been drawn from... Figure 3 The known water lines 18 and 18' are then directed to humidifiers 34 and 35, where humidification can be achieved, for example, by single-component or two-component nozzles, of the volumetric flow in the tiered line 9 and / or the input air line 22. Humidifiers 34 and 35 can be operated electrically.

[0038] Water is supplied to the two hydrodynamic support devices 36 and 37 of the unloaded turbocharger 11 via two additional water lines 174 and 175, thus making the unloaded turbocharger resemble a water support. Here, sufficient wastewater is generally available in the fuel cell systems 2 and 3 to humidify not only the input airflow but also to support the unloaded turbocharger 11, thereby enabling water supply without external water delivery to the system. This structure allows the use of components known in conventional automotive technology, particularly in internal combustion engine technology, and especially in gasoline-injected internal combustion engines, to minimize harmful substances and consumption. Therefore, this type of component can be readily, well-proven, and cost-effectively available on the market.

Claims

1. An air supply device (1) for a fuel cell system (2, 3) having a flow compressor and a drive motor (4) for the flow compressor, wherein The flow compressor has two compressor wheels (6, 7) which are configured symmetrically and are arranged on a common shaft (5) together with a drive motor (4) arranged between the two compressor wheels, characterized in that the two compressor wheels (6, 7) are connected on the pressure side to two aerodynamically non-persistent systems, which are two fuel cell systems (2, 3), the two compressor wheels (6, 7) being provided for supplying air to the two fuel cell systems (2, 3).

2. The air supply device (1) according to claim 1, characterized in that The aerodynamically non-persistent systems are connected in a controllable manner by means of a bypass line (15) provided with a valve (16).

3. The air supply device (1) according to claim 1 or 2, characterized in that There is provided a device for delivering a liquid into the compressed air stream, the device having at least one nozzle for atomizing the liquid in the compressed air stream.

4. A fuel cell system (2, 3) having at least one fuel cell (19), wherein The air supply of the fuel cell (19) is carried out with at least a part of the air from the air supply device (1) according to any one of claims 1 to 3.

5. The fuel cell system (2, 3) according to claim 4, further comprising an anode side (20) and a cathode side (21) of the at least one fuel cell (19), characterized in that The outlet of the cathode side (21) is selectively or partially in controllable manner communicable with the environment and / or with a recirculation line (25).

6. The fuel cell system (2, 3) according to claim 4 or 5, further comprising anode exhaust gas recirculation means, the recirculation means being implemented at least in part by a recirculation blower (31), characterized in that, The recirculation blower (31) is coupled with an exhaust air turbine (32) driven by the exhaust gas of the fuel cell (19), which is the cathode exhaust air.

7. The fuel cell system (2, 3) according to claim 6, characterized in that The coupling between the exhaust air turbine (32) and the recirculation blower (31) is configured as a magnetic coupling.

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