Fuel cell system and vehicle having the fuel cell system

Abstract

The invention relates to a fuel cell system (10) comprising: a fuel cell (11) having an anode (12) and a cathode (13); a fuel path (14); an anode inlet path (15); an anode exhaust gas path (16); a recirculation path (17); an injector (28); and an ejector (18) having a mixing region (35) and a motive nozzle (30); wherein: the motive nozzle (30) has an inlet opening (31) for conducting fuel from the injector (28) into the motive nozzle (30) and has an outlet opening (32) for conducting fuel from the motive nozzle (30) into the mixing region (35); fuel from the motive nozzle (30) is mixed, in the mixing region (35), with anode exhaust gas from the recirculation path (17) and is conducted as mixed gas into the anode inlet path (15); the injector (28) is configured to control the fuel pressure of fuel in the motive nozzle (30); and the smallest flow cross-section (33) of the motive nozzle (30) is smaller than the smallest settable flow cross-section (29) of the injector (28). The invention also relates to a vehicle (100) having the fuel cell system (10).

Description

[0001] 23-3724

[0002] - 1 -

[0003] Description

[0004] Fuel cell system and vehicle with fuel cell system

[0005] The technology revealed here relates to a fuel cell system and a vehicle with the fuel cell system.

[0006] Various fuel cell systems for mobile applications are known in the prior art. In a vehicle, fuel cell systems are typically configured to generate electricity for the vehicle's drive motor. Typical fuel cell systems comprise a fuel cell with multiple fuel cell elements, each having two electrodes and a membrane array between them. Within the fuel cell, fuel reacts with an oxidizer via reverse electrolysis, thereby generating electricity. The fuel can be supplied to the fuel cell from at least one pressure vessel in the vehicle. The oxidizer can be drawn from the ambient air.

[0007] Among the well-known fuel cell systems were PEM fuel cell systems. In PEM fuel cell systems, pressure differences between the pressure vessel and an anode of the fuel cell can be so large that fuel flows at the speed of sound or faster can occur. Known PEM fuel cell systems also frequently feature an injector / ejector configuration in the anode system, which operates on the principle of a jet pump. The ejector draws anode exhaust gas from a recirculation path and then returns it to the anode. The injector can be designed as a proportional valve to regulate the gas pressure in the ejector. After the fuel leaves the injector, it flows into the ejector. In known systems, the injector represents the smallest flow cross-section of the injector / ejector configuration. Therefore, pressure fluctuations occur at the injector in these systems.The highest fuel flow velocity occurs at the smallest flow cross-section. Furthermore, it is known that the flow is altered by gas-dynamic valve shocks in the injector such that it enters the ejector at a subsonic speed. To control recirculation in conventional PEM fuel cell systems, the mass flow through the injector / ejector configuration is regulated in order to set further target values. 23-3724.

[0008] - 2 -

[0009] The purpose of the present technology is to improve recirculation in fuel cell systems.

[0010] The aforementioned problem is solved by the patent claims. In particular, the aforementioned problem is solved by the fuel cell system and the vehicle according to the dependent claim. Further advantages of the disclosed technology will become apparent from the dependent claims, the description, and the figures. Features described in connection with the fuel cell system also apply in connection with the vehicle, and vice versa, so that the disclosure always makes and / or can make reciprocal references to the individual aspects.

[0011] According to a first aspect of the present technology, a fuel cell system is proposed that features:

[0012] - a fuel cell with an anode and a cathode,

[0013] - a fuel path, an anode inlet path, an anode exhaust path, a recirculation path, an injector and

[0014] - an ejector with a mixing area and a drive nozzle,

[0015] - wherein the drive nozzle has an inlet opening for directing fuel from the injector into the drive nozzle and an outlet opening for directing fuel from the drive nozzle into the mixing area,

[0016] - wherein in the mixing area fuel from the drive nozzle is mixed with anode exhaust gas from the recirculation path and fed as mixed gas into the anode inlet path,

[0017] - wherein the injector is configured to regulate a fuel pressure of fuel in the injector and

[0018] - where the smallest flow cross-section of the drive nozzle is smaller than the smallest adjustable flow cross-section of the injector.

[0019] First, it was recognized that the smallest flow cross-section in the area of ​​the injector and the drive nozzle determines the maximum possible mass flow rate. Furthermore, it was recognized that a momentum maximum exists in the region of the smallest flow cross-section of the drive nozzle. It was also recognized that the fuel can be accelerated to the speed of sound and beyond in the region of the smallest flow cross-section of the drive nozzle if the smallest flow cross-section of the drive nozzle is smaller than 23-3724.

[0020] - 3 - the smallest adjustable flow cross-section of the injector. Furthermore, it was found that particularly effective and / or efficient recirculation of anode exhaust gas through the recirculation path can be achieved when the flow velocity in the ejector reaches the speed of sound or even supersonic speed. That is, it was found that the suction effect of the ejector is particularly strong when fuel is introduced into the mixing zone through the drive nozzle at the speed of sound or even supersonic speed. The configuration proposed here allows this to be achieved during different operating states of the fuel cell system, and especially during low-load operation of the fuel cell system.By regulating the fuel pressure in the injector, combined with the smallest possible flow cross-section of the drive nozzle, it is possible to create a sonic ejector and / or a supersonic ejector in which the flow velocity, and thus the corresponding impulse, can be increased beyond the speed of sound. In conventional fuel cell systems, the mass flow rate, not the fuel pressure, is regulated by the injector to achieve a desired fluid pressure downstream of the ejector. With a constant flow cross-section in the mixing zone and / or in the drive nozzle area, and a constant fuel pressure in the fuel path, the flow velocity into the ejector and / or the mixing zone is always below the speed of sound, and the ejector is blocked or closed.A so-called "choked flow" is triggered as soon as the speed of the fuel flow develops towards the speed of sound.

[0021] To regulate the fuel pressure in the drive nozzle, the injector described here can have two essential valve functions. First, the injector can generate a defined and / or definable pressure drop. That is, the injector can be configured to create a defined and / or definable pressure drop between an injector inlet and an injector outlet. The second essential function of the injector is to separate and / or close off the fuel flow through the fuel path towards the anode. In the fuel cell system proposed here, the mass flow through the ejector can still be regulated by an injector valve opening, whereby the mass flow is set by a controlled and, in particular, regulated pressure drop across the injector.The pressure set upstream of the ejector no longer affects the flow velocity through the smallest flow cross-section of the propulsion nozzle, but only the density of the fuel or the 23-3724.

[0022] - 4 - of the corresponding gas and thus the mass flow. The flow velocity always has the maximum possible value.

[0023] The term "drive nozzle" refers to a component of the ejector that defines a nozzle-shaped intermediate volume between an injector outlet and a mixing volume inlet. The drive nozzle may have a partially tapered or partially convergent nozzle section. The injector may have a proportional valve or be configured as a proportional valve.

[0024] The fuel cell system can include at least one pressure sensor for determining a gas pressure in and / or at the anode and / or for determining a gas pressure in and / or at the drive nozzle. A pressure sensor for determining a gas pressure in the drive nozzle is particularly advantageous for virtual modeling, based on which the operating mode and / or an operating strategy of the fuel cell system can be configured.

[0025] The fuel cell system can be a PEM fuel cell system. The fuel cell system can include a pressure vessel for fuel storage. The pressure vessel can be configured to store hydrogen. The pressure vessel can be configured as a high-pressure gas cylinder. The pressure vessel can be configured to continuously store fuel such as hydrogen at ambient temperatures at a nominal operating pressure of at least 350 bar or at least 700 bar. The fuel cell system can include at least one pressure vessel. That is, the term "pressure vessel" can refer to at least one pressure vessel. For example, the fuel cell system can include multiple pressure vessels connected to each other via a fluid busbar.The fuel path can be configured to deliver fuel from the pressure vessel to the injector at a pressure of at least 500 bar, at least 600 bar, or at least 700 bar. The pressure can be reduced to a desired value at and / or upstream of the injector. The injector can be configured to further reduce the fuel pressure. Within the scope of the technology described here, it has been recognized that the pressure in the pressure vessel, in combination with the proposed injector / ejector configuration, can be utilized in such a way that a dedicated pump and / or compressor can be omitted. That is, it is possible for no compressor or similar equipment to be positioned in the fuel path and / or upstream of the injector. 23-3724.

[0026] - 5 -

[0027] The fuel path may include a channel arrangement through which fuel can be directed from the pressure vessel to the injector in a controlled manner. The anode inlet path may include a channel arrangement through which mixed gas from the ejector, and in particular from a diffuser downstream of the ejector, can be directed into the anode and / or an anode inlet. The diffuser can be considered part of the anode inlet path but is not a mandatory component of the fuel cell system described here. The anode exhaust path may include a channel arrangement through which anode exhaust gas can be directed from the anode into the recirculation path or at least towards the recirculation path. The fuel cell system may include a water separator designed as a link between the anode exhaust path and the recirculation path.The recirculation path may include a channel arrangement through which anode exhaust gas from the anode exhaust path and / or from the water separator can be directed and / or drawn into the ejector.

[0028] The injector can have an injector inlet and an injector outlet. The fuel path can be configured to direct fuel to the injector inlet. The injector outlet can be located directly at the inlet of the drive nozzle. The drive nozzle outlet can be located directly at a mixing zone inlet. A mixing zone outlet can be located directly at a diffuser inlet. A diffuser outlet allows mixed gas from the mixing zone to be directed to the anode via the anode inlet path. The smallest flow cross-section of the drive nozzle can be located at the drive nozzle outlet or in a region between the outlet and inlet of the drive nozzle.

[0029] The flow cross-section can be understood as the area through which gas can flow in the injector, the drive nozzle, and the mixing section. If the injector is completely closed and / or in a blocked state, there is no flow cross-section. That is, in the closed state, the injector has no flow cross-section. The smallest adjustable flow cross-section of the injector can therefore be understood as the smallest area within the injector that can be adjusted by the fuel cell system and / or a control unit, through which gas can flow at a defined point in the injector. The adjustable flow cross-section can be understood as a flow cross-section that can be adjusted by means of the fuel cell system, for example, by actuators of the fuel cell system. 23-3724

[0030] - 6 -

[0031] The fuel cell system is preferably configured for mobile applications such as vehicles. The fuel cell system can be configured to provide electrical energy or current for at least one of the vehicle's drive units. The drive unit can be a machine, for example, an electric motor, used to propel the vehicle. The term "fuel cell" can refer to a single fuel cell or, in particular, a fuel cell stack with multiple fuel cell elements. In its simplest form, the fuel cell is an electrochemical energy converter that converts fuel and oxidant into reaction products, generating electricity and heat in the process. The anode and cathode of a single fuel cell can be separated by an ion-selective or ion-permeable separator.If the fuel cell is configured as a fuel cell stack, the anode can refer to the anode region of the fuel cell stack, and the cathode to the cathode region of the fuel cell stack. The anode can also refer to the anode path through the fuel cell stack in which the total fluid flows. Fuel can refer to hydrogen or a hydrogen-containing gas mixture.

[0032] According to one embodiment of the fuel cell system described here, the ejector can be configured such that, during operation of the fuel cell system, fuel can flow through the smallest flow cross-section of the drive nozzle into the mixing zone at least at the speed of sound. The ejector can therefore be understood as a sonic ejector and / or a supersonic ejector. As described above, the high flow velocity in the ejector enables particularly effective recirculation. With the proposed dimensioning of the flow cross-sections in the injector and the ejector, the speed of sound can be reached and / or maintained even during low-load operation of the fuel cell system, and the mass flow rate can be further increased.Low-load operation refers to the operation of the fuel cell system in which the fuel cell generates significantly less power than its maximum potential. Low-load operation can occur, for example, during standby mode of the fuel cell system.

[0033] Furthermore, the ejector of the fuel cell system proposed here can be configured such that the fuel pressure in at least part of the drive nozzle is at least 180% higher than in the mixing zone during operation of the fuel cell system. It was found that at a specific pressure difference between drive nozzle 23-3724

[0034] - 7 - and mixing zone, a particularly advantageous recirculation can be achieved. Advantageous recirculation occurs especially when the fuel pressure and / or a corresponding fluid pressure in the ejector is at least approximately twice as high as in the mixing zone. To achieve this, the ejector can be dimensioned accordingly and the injector can be monitored accordingly during operation of the fuel cell system.

[0035] In the fuel cell system described here, the drive nozzle can also have the shape of a Laval nozzle. That is, the drive nozzle can be configured as a Laval nozzle. In this case, the smallest flow cross-section of the drive nozzle is located between the outlet and inlet openings, specifically closer to the inlet opening. It has been found that the flow velocity through the smallest flow cross-section of the drive nozzle can reach supersonic speeds in this case. In particular, the flow velocity can reach supersonic speeds even during low-load operation of the fuel cell system. This further enhances the desired recirculation.

[0036] Furthermore, it is possible that the injector in the proposed fuel cell system has a meandering fuel channel. This meandering fuel channel can generate friction losses and / or turbulence, thereby achieving effective and / or efficient fuel pressure reduction across the injector. In other words, the injector in this case has a pressure reduction configuration that is not limited to a minimal cross-section in the area of ​​a valve tappet and / or the injector outlet. The meandering fuel channel can be configured as a type of labyrinth seal. A meandering fuel channel can be understood as an injector fuel channel with multiple angled channel sections. For example, projections can be formed on an injector tappet and / or on a valve chamber wall of the injector to create the meandering fuel channel.

[0037] Furthermore, in the proposed fuel cell system, it is possible for the smallest flow cross-section of the drive nozzle to be at least 10% smaller than the smallest adjustable flow cross-section of the injector. With such a difference, the speed of sound or supersonic speed can be achieved with particularly high reliability. It is also possible for the smallest flow cross-section of the drive nozzle to be reduced by 23-3724

[0038] - 8 - at least 20%, at least 30%, at least 40% or at least 50% smaller than the smallest adjustable flow cross-section of the injector.

[0039] The smallest flow cross-section of the drive nozzle in the fuel cell systems described here can have an area in the range of 5 mm². 2 and 30 mm 2exhibiting certain characteristics. It was recognized that the flow cross-section in this area leads to particularly advantageous recirculation. The smallest flow cross-section of the drive nozzle can, for example, have a circular area or an annular gap. In the case of a circular area, the diameter can be in a range between 3 mm and 7 mm or in a range between 4 mm and 6 mm, for example, approximately 5 mm. The smallest adjustable flow cross-section of the injector can be larger in each case, for example, larger than 5 mm. 2 , larger than 10 mm 2 or larger than 30 mm 2 Downstream of the ejector, the fuel cell system may have a diffuser whose smallest flow cross-section is, for example, at least 10 mm². 2 or at least 30 mm 2 It is large. The diffuser can be considered part of the anode inlet path.

[0040] The fuel cell system can include a control unit that can be configured to control the fuel pressure in the drive nozzle via the injector, thereby setting a defined mass flow rate in the drive nozzle. That is, as explained above, the fuel pressure can be controlled and, in particular, regulated to set a desired mass flow rate. In conventional fuel cell systems, this is done in precisely the opposite way. By controlling the fuel pressure, the density of the fuel flow can be set and / or changed. The mass flow rate changes proportionally with the changed density. The fuel pressure can be changed particularly easily via the injector. Accordingly, the mass flow rate can be increased just as easily, even if the fuel is already flowing through the ejector at the speed of sound or even supersonic speed.

[0041] The fuel path and the injector can be configured to control the mass flow in the drive nozzle by changing the pressure drop across the injector. Once the ejector "blocks" upon reaching a maximum flow velocity through the drive nozzle, an increased fuel mass flow can only be achieved by increasing the fuel pressure or the supply pressure. The fuel cell system, and in particular the fuel path, can now be designed, for example, to maintain a minimum fuel pressure or supply pressure at injector 23-3724 during low-load operation of the fuel cell system.

[0042] - 9 - is present and a maximum fuel pressure is present at the injector during high-load operation. The pressure drop can then be adjusted using the injector. The injector can therefore be understood as a pressure control valve whose adjustable flow cross-section is set to a minimum during low-load operation, to a maximum during high-load operation, and to a corresponding intermediate state in intermediate states. In this way, a blower upstream of the injector can be omitted. For example, the fuel path can be configured so that during operation of the fuel cell system, the fuel pressure at the injector is in a range between 10 bar and 30 bar, between 15 bar and 25 bar, for example, 20 bar. During operation, the desired pressure drop can then be set by the injector.This means that the fuel pressure can be reduced by the injector depending on the desired mass flow and / or recirculation behavior. Setting the fuel pressure to approximately 20 bar can be understood to mean that the fuel cell system, and in particular a pressure reduction unit of the fuel path, can be configured such that a maximum supply pressure of approximately 20 bar is present at the injector or at an injector inlet port during operation of the fuel cell system. The fuel pressure can then be reduced to, for example, 2 bar using the injector.Accordingly, the injector can be configured to deliver fuel to the drive nozzle at a fuel pressure between, for example, 2 bar and 5 bar during low-load operation of the fuel cell system, and at a fuel pressure between 10 bar and 30 bar during high-load operation. This allows the fuel cell system to cover different power ranges with a factor of, for example, 10 or more.

[0043] The control unit can further be configured to increase the fuel pressure in the drive nozzle by means of the injector when the fuel flows into the mixing zone at at least the speed of sound through the smallest flow cross-section of the drive nozzle. Thus, the mass flow rate can still be increased even during low-load operation of the fuel cell system, even if the fuel is already flowing into the mixing zone at or above the speed of sound. In other words, the control unit can be configured to increase the fuel pressure in the drive nozzle by means of the injector during low-load operation of the fuel cell system if the fuel flows into the mixing zone at at least the speed of sound through the smallest flow cross-section of the drive nozzle during low-load operation. 23-3724

[0044] - 10 -

[0045] Another aspect of the proposed technology concerns a vehicle with a fuel cell system as described above, wherein the fuel cell system is configured to generate electricity in the vehicle. The vehicle may have at least one electric motor for propelling the vehicle, and the fuel cell system may be configured to supply power to this at least one electric motor. The term "vehicle" can refer to a motor vehicle such as a motorized two-wheeler, a passenger car, or a truck. It can also refer to a road vehicle, an aircraft, a watercraft, a rail vehicle, or a robot. Furthermore, the term "vehicle" can refer to a purely electric vehicle or a hybrid electric vehicle that, in addition to the at least one electric motor, has an internal combustion engine for propelling the vehicle.The term "vehicle" can refer to a fuel cell vehicle and / or a so-called FCEV (Fuel Cell Electric Vehicle).

[0046] Further features and combinations of features of the proposed technology will become apparent from the following description of various embodiments, which are schematically illustrated in the figures. All features and / or advantages arising from the claims, the description, and the figures, including design details and spatial arrangements, can be significant both individually and in combination with one another.

[0047] They each show schematically:

[0048] Fig. 1 shows a fuel cell system according to an embodiment of the present technology,

[0049] Fig. 2 shows an injector / ejector configuration for a fuel cell system according to a first embodiment of the present technology,

[0050] Fig. 3 shows an injector / ejector configuration for a fuel cell system according to a second embodiment of the present technology,

[0051] Fig. 4 shows a conventional injector / ejector configuration and 23-3724

[0052] - 11 -

[0053] Fig. 5 shows a vehicle with a fuel cell system according to an embodiment of the present technology.

[0054] Elements with the same function and mode of operation are each provided with the same reference symbols in the figures.

[0055] Fig. 1 shows a fuel cell system 10 according to a possible embodiment as a PEM fuel cell system. The illustrated fuel cell system 10 comprises a fuel cell 11 with an anode 12 and a cathode 13. The fuel cell 11 has an anode inlet 21, an anode outlet 22, a cathode inlet 23, and a cathode outlet 24. The fuel cell system 10 further comprises a fuel path 14, an anode inlet path 15, an anode exhaust path 16, a recirculation path 17, a cathode inlet path 26, a cathode exhaust path 27, an injector 28, an ejector 18, a diffuser 36, a purge path 19, and a purge valve 25. The ejector 18 has a drive nozzle 30 and a mixing chamber 35. In the mixing area 35, during operation of the fuel cell system 10, anode exhaust gas from the recirculation path 17 is mixed with fuel from the fuel path 14.Fuel can be supplied as primary fluid from a pressure vessel 70 to the injector 28 via the fuel path 14.

[0056] Anode gas, as a mixed gas, can be fed from the mixing chamber 35 into the fuel cell 11 via the diffuser 36 via the anode inlet path 15. Anode gas can be discharged from the fuel cell 11 via the anode exhaust path 16. Anode gas from the fuel cell 11 can be drawn into the ejector 18 and, in particular, into the mixing chamber 35 via the recirculation path 17 as a secondary fluid and then returned to the fuel cell 11 via the anode inlet path 15. Anode gas and water from the fuel cell 11 can be directed into the cathode exhaust path 27 via the purge path 19. This means that anode gas can be discharged from the anode system in a purge process and water can be flushed from the anode system in a drain process. Furthermore, the fuel cell system 10 has a control unit 20.The control unit 20 can include various sensors, actuators and a computing unit for operating the fuel cell system and / or for executing defined operating strategies of the fuel cell system.

[0057] Figure 2 shows the injector 28, the ejector 18, and the diffuser 36 in further detail. As can be seen in Figure 2, the drive nozzle 30 has an inlet opening 23-3724.

[0058] - 12 -

[0059] 31 for directing fuel from the injector into the drive nozzle 30 and an outlet opening

[0060] 32 for directing fuel from the drive nozzle 30 into the mixing area 35. The inlet opening 31 of the drive nozzle 30 corresponds to and / or is adjacent to an injector outlet opening. The outlet opening 32 of the drive nozzle 30 corresponds to and / or is adjacent to a mixing area inlet opening. As can be seen in Fig. 2, in the mixing area 35, fuel from the drive nozzle 30 can be mixed with anode exhaust gas from the recirculation path 17 and directed via the diffuser 36 as mixed gas into the anode inlet path 15.

[0061] The injector has a valve tappet 38 and a valve wall 39. Tappet projections 40 are formed on the valve tappet 38. Wall projections 41 are formed on the valve wall 39. The injector 28 thus has a meandering fuel channel. The injector 28 is configured to regulate the fuel pressure of the fuel in the drive nozzle 30. For this purpose, the valve tappet 38 can be moved translationally or back and forth in a longitudinal direction. Depending on the movement and / or the position of the valve tappet 38, the flow cross-sections of the injector 28 change. In Fig. 2, the injector 28 is in an operating state in which the injector 28 has its smallest adjustable flow cross-section 29. In the example shown, the smallest adjustable flow cross-section 29 of the injector 28 is located at the inlet opening 31 of the drive nozzle 30.Flow cross-sections 29, each formed between a tappet projection 40 and a wall projection 41, can form a similarly small or equally small area. The smallest flow cross-section 33 of the drive nozzle 30 is formed in the region of the outlet opening 32, wherein the smallest flow cross-section 33 of the drive nozzle 30 is smaller than the smallest adjustable flow cross-section 29 of the injector 28.

[0062] In the illustrated embodiment, the ejector 18 is configured such that, during operation of the fuel cell system 10, fuel can flow at least at the speed of sound through the smallest flow cross-section 33 of the drive nozzle 30 into the mixing area 35. Furthermore, the ejector 18 is configured such that the fuel pressure in at least a portion of the drive nozzle 30 during operation of the fuel cell system 10 is at least approximately twice as high as in the mixing area 35. In the illustrated example, the smallest flow cross-section 33 of the drive nozzle 30 is approximately 40% smaller than the smallest adjustable flow cross-section of the injector 28. In the illustrated example, the smallest flow cross-section 33 of the drive nozzle 30 has a diameter of approximately 5 mm. 23-3724

[0063] - 13 -

[0064] The control unit 20 shown in Fig. 1 is configured to control the fuel pressure in the drive nozzle 30 by means of the injector 28 in order to set a defined and / or desired mass flow rate in the drive nozzle. Furthermore, the fuel path 14 and the injector 28 are configured to control the mass flow rate in the drive nozzle 30 by changing a pressure drop across the injector 28. The fuel path 14 is configured so that a fuel pressure of approximately 20 bar is present at the injector 28 during operation of the fuel cell system 10. For this purpose, a suitable pressure reduction unit (not shown) is provided in the fuel path 14. The control unit 20 is also configured to increase the fuel pressure in the drive nozzle 30 by means of the injector 28 when the fuel flows at least at the speed of sound through the smallest flow cross-section 33 of the drive nozzle 30 into the mixing zone 35.This means that if the fuel reaches the speed of sound in the area of ​​the outlet opening 32, the fuel pressure can be further increased by means of the injector 28, so that the mass flow through the drive nozzle 30 is also increased.

[0065] Fig. 3 shows an injector / ejector configuration according to a second embodiment. According to the embodiment shown in Fig. 3, the drive nozzle 30 is configured as a Laval nozzle. In this case, the smallest flow cross-section 33 of the drive nozzle 30 is located between the inlet opening 31 and the outlet opening 33. In the region of the smallest flow cross-section of the drive nozzle 30, the fuel can reach supersonic speeds even during low-load operation of the fuel cell system 10.

[0066] Figure 4 shows a conventional injector / ejector configuration in which the smallest flow cross-section 33 of the drive nozzle is larger than the smallest adjustable flow cross-section 29 of the injector 28. It should be noted that conventional injector / ejector configurations for fuel cell systems often omit a drive nozzle. These systems differ fundamentally in their physical operating principles from the technology described here.

[0067] Figure 5 shows a vehicle 100 in the form of a passenger car. The vehicle 100 has a fuel cell system 10 as described above, comprising a fuel cell 11 and a pressure vessel 70 for storing fuel. The vehicle 100 also has two electric motors 60 for propelling the vehicle 100. The fuel cell system 10 is configured to generate electrical current in the vehicle 100, which can be used to power the electric motors 60. Furthermore, 23-3724

[0068] - 14 - the vehicle 100 has a control unit 20 which is configured to operate the fuel cell system 10 and its functional components in the desired manner.

[0069] The technology disclosed here allows for further design principles in addition to those illustrated. That is to say, the technology should not be considered limited to the embodiments explained with reference to the figures.

[0070] -3724

[0071] - 15 -

[0072] Reference symbol list

[0073] B renn stoffze 11 en syste m

[0074] Fuel cell

[0075] anode

[0076] cathode

[0077] Fuel path

[0078] Anode inlet path

[0079] Anode exhaust path

[0080] Recirculation path

[0081] Ejector

[0082] Flushing path

[0083] Control unit

[0084] Anode input

[0085] anode output

[0086] Cathode inlet

[0087] Cathode output

[0088] Flush valve

[0089] cathode inlet path

[0090] Cathode exhaust path

[0091] Injector smallest flow cross-section of the injector

[0092] Drive nozzle

[0093] Inlet opening

[0094] Outlet opening smallest flow cross-section of the drive nozzle

[0095] Mixing area

[0096] Diffuser

[0097] Valve tappet

[0098] Valve wall

[0099] plunger projection

[0100] wall projection

[0101] electric motor

[0102] Pressure vessel 0 vehicle

Claims

23-3724 - 16 - Patent claims 1. Fuel cell system (10), comprising: - a fuel cell (11) with an anode (12) and a cathode (13), - a fuel path (14), an anode inlet path (15), an anode exhaust path (16), a recirculation path (17), an injector (28), - an ejector (18) with a mixing area (35) and a drive nozzle (30), - wherein the drive nozzle (30) has an inlet opening (31) for directing fuel from the injector (28) into the drive nozzle (30) and an outlet opening (32) for directing fuel from the drive nozzle (30) into the mixing area (35), - wherein in the mixing area (35) fuel from the drive nozzle (30) is mixed with anode exhaust gas from the recirculation path (17) and directed as mixed gas into the anode inlet path (15), - wherein the injector (28) is configured to regulate the fuel pressure of fuel in the propulsion nozzle (30) and - wherein the smallest flow cross-section (33) of the drive nozzle (30) is smaller than the smallest adjustable flow cross-section (29) of the injector (28).

2. Fuel cell system (10) according to claim 1, wherein the ejector (18) is configured such that fuel can flow into the mixing area (35) at least at the speed of sound during operation of the fuel cell system (10) through the smallest flow cross-section (33) of the drive nozzle (30).

3. Fuel cell system (10) according to one of the preceding claims, wherein the ejector (18) is configured such that a fuel pressure in at least a part of the drive nozzle (30) is at least 180% higher than in the mixing area (35) during operation of the fuel cell system.

4. Fuel cell system (10) according to one of the preceding claims, wherein the drive nozzle (30) has the form of a Laval nozzle.

5. Fuel cell system (10) according to one of the preceding claims, wherein the injector (28) has a meandering fuel channel. 23-3724 - 17 - 6. Fuel cell system (10) according to one of the preceding claims, wherein the smallest flow cross-section (33) of the drive nozzle (30) is at least 10% smaller than the smallest adjustable flow cross-section of the injector (28).

7. Fuel cell system (10) according to one of the preceding claims, wherein the smallest flow cross-section (33) of the drive nozzle (30) has an area in a range between 5 mm 2 and 30 2 mm.

8. Fuel cell system (10) according to one of the preceding claims, comprising a control unit (20) configured to control the fuel pressure in the drive nozzle (30) by means of the injector (28) in order to set a defined mass flow in the drive nozzle.

9. Fuel cell system (10) according to one of the preceding claims, wherein the fuel path (14) and the injector (28) are configured to control the mass flow in the drive nozzle (30) by changing a pressure drop across the injector (28).

10. Fuel cell system (10) according to one of claims 8 to 9, wherein the fuel path (14) is configured such that during operation of the fuel cell system (10) the fuel pressure at the injector (28) is in a range between 10 bar and 30 bar.

11. Fuel cell system (10) according to one of claims 8 to 10, wherein the control unit (20) is configured to increase the fuel pressure in the drive nozzle (30) by means of the injector (28) when the fuel flows at least at the speed of sound through the smallest flow cross-section (33) of the drive nozzle (30) into the mixing area (35).

12. Vehicle (100) with a fuel cell system (10) according to one of the preceding claims, wherein the fuel cell system (10) is configured to generate electrical current in the vehicle (100).

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