Fuel cell system for a vehicle

Abstract

The invention relates to a fuel cell system for a vehicle, comprising a plurality of fuel cells (2) arranged in a fuel cell stack (1), an ejector (3) arranged for introducing fuel gas into the fuel cell stack (1), and a fuel gas recirculation (5) for returning residual fuel gas to the fuel cell stack (1), characterized in that the ejector (3) and the fuel gas recirculation (5) are arranged in a housing (6), wherein the housing (6) simultaneously encloses the fuel cell stack (1), and ambient air can be introduced into the housing (6) to purge the housing (6), and the fuel gas escaping from the ejector (3), the fuel gas recirculation (5), and the fuel cell stack (1) due to leaks can be discharged from the housing (6).

Description

The invention relates to a fuel cell system for a vehicle according to the type defined in more detail in the preamble of claim 1.EP 2 008 332 B1 discloses a fuel cell system having a fuel cell stack and a fuel feed line for supplying a fuel to the fuel inlet of the fuel cell stack. A jet pump is connected to the fuel supply line and to a fuel outlet of the fuel cell stack via a recirculation line.The object of the invention is therefore to propose a fuel cell system of the aforementioned type, in which explosion protection with respect to leakage-induced escape of fuel gas-carrying components during operation is improved in a structurally simple and cost-effective manner.The object is achieved by the features of claim 1. Further advantageous and claimed embodiments are evident from the respective dependent claims, the description and the drawing.Thus, a fuel cell system for a vehicle having a plurality of fuel cells arranged in a fuel cell stack is proposed. The fuel cell system includes an ejector arranged to supply fuel gas to the fuel cell stack and a fuel gas recirculation for recirculating residual fuel gas to the fuel cell stack. In order to realize explosion protection in the fuel cell system in a structurally simple and cost-effective manner, it is provided that the ejector and the fuel gas recirculation are arranged in a housing, wherein the housing simultaneously comprises the fuel cell stack and ambient air can be introduced into the housing for flushing the housing, and the fuel gas exiting from the ejector, the fuel gas recirculation and from the fuel cell stack on account of leaks can be discharged from the housing.The housing protects in particular the ejector, the fuel gas recirculation and the fuel cell stack from external influences. At the same time, the fuel gas exiting from the ejector, the fuel gas recirculation and the fuel cell stack as a result of leakage can be selectively aerated by the introduced purging air and can be selectively discharged from the housing. As a result, the leaks are secured by the housing and the fuel gas concentration in the housing can be maintained below the explosion limit, so that the formation of an ignitable mixture can be reliably avoided.In addition, by integrating the ejector and the fuel gas recirculation into the housing, the installation space of the fuel cell system can be reduced and the power density of the fuel cell system can be increased.In a preferred embodiment of the invention, the ejector is arranged so as to abut an end of the fuel cell stack and is connected directly thereto for the introduction of fuel gas and for the fuel gas recirculation. In this way, a particularly compact arrangement is made possible and additional connecting lines between ejector and fuel cell stack for the introduction of the fuel gas and for the fuel gas recirculation can be avoided.The arrangement can be further optimized if, preferably, the ejector is arranged parallel to a stack end plate of the fuel cell stack, in such a way that the connections for introducing fuel gas into the fuel cell stack and for drawing in fuel residual gas from the fuel gas recirculation are formed laterally with respect to the main fuel gas flow in the ejector. The lateral connection of the ejector to the fuel cell stack transversely to the main fuel gas flow of the ejector enables a particularly simple and space-saving arrangement.It is also conceivable for the ejector with the mixing tube for mixing the fuel residual gas sucked through it from the fuel gas recirculation and the fuel gas supplied from the fuel supply to pass directly into a fuel gas connection on the fuel cell stack.The arrangement of the ejector in the housing can thus be easily adapted to the installation conditions.In a next advantageous development of the invention, a discharge valve for discharging nitrogen from the residual fuel gas of the fuel gas recirculation to be recirculated is integrated into the ejector. In this way, the discharge valve can be arranged in the ejector in a space-saving manner. At the same time, this makes it possible to discharge the undesired nitrogen fraction from the recirculation gas, which adversely affects the operation of the fuel cells, in a particularly simple manner.Preferably, the nitrogen can be discharged from the housing through the discharge valve into a discharge line connected to the ejector into the exhaust gas flow and can be discharged from the housing together with the exhaust gas flow.A further preferred embodiment provides that a water separator for removing water vapor from the residual fuel gas of the fuel gas recirculation to be recirculated is integrated into the ejector. As a result, the water separator can be arranged in the ejector in a manner saving installation space and the undesired excess water vapor from the recirculation gas, which adversely affects the operation of the fuel cells, can be separated off particularly easily by said ejector.Preferably, the water vapor separated at the water separator can be discharged from the housing through the discharge valve integrated into the ejector into the discharge line connected thereto and can be discharged from the housing together with the exhaust gas flow. Accordingly, the discharge valve can be used in a dual function, so that additional fittings and connecting lines can be avoided.In the context of a next advantageous development of the invention, it is provided that a fuel gas inlet valve for controlling the fuel gas supply through the ejector into the fuel cell stack is arranged in the housing. In this way, the fuel gas inlet valve is also protected from external influences and the fuel gas leaks which may occur at it can also escape only into the housing and be discharged from the housing in a targeted manner with the exhaust gas stream.Preferably, the fuel gas inlet valve is integrated in a space-saving manner into a fuel gas supply connection on the housing or is connected directly thereto, to which a fuel gas supply can be connected.In this case, the arrangement of the fuel gas inlet valve can be easily adapted to the installation conditions. It is also conceivable to arrange the fuel gas inlet valve directly on the ejector or integrated therein.In a further preferred embodiment of the invention, a coolant inlet connection and a coolant outlet connection of a coolant circuit for cooling the fuel cell stack are provided on the housing.Preferably, an air inlet connection is also formed for supplying the fuel cells with an air oxygen stream and for flushing the housing with a flushing air stream.In a further advantageous manner, an exhaust gas connection is preferably provided at which the fuel gas exiting into the housing due to leakage can be discharged from the housing together with the exhaust gas flow.It is advantageous here if the aforementioned connections, including the fuel gas supply connection mentioned further above, are preferably arranged on one side of the housing. Preferably, they are embodied here on a central adapter, in particular an adapter plate.Hydrogen is preferably provided as the fuel gas. However, the use of other fuel gases, in particular methane, is also conceivable. It is also possible to use other fuels, such as methanol.Further claimed features of the invention will become apparent from the following description and from the drawing, on the basis of which the present invention is explained in more detail. The single FIGURE shows, by way of example, a fuel cell system according to the invention for a vehicle.The fuel cell system shown in FIG. 1 includes a plurality of fuel cells 2 arranged in a fuel cell stack 1, an ejector 3 is arranged in a fuel gas supply line 4 for supplying fuel gas into the fuel cell stack 1 and serves for drawing residual fuel gas discharged from the fuel cells 2 from a fuel gas recirculation line 5, and the fuel gas supplied via the fuel gas supply line 4 serves as a fuel gas. Hydrogen is preferably provided as the fuel gas.The ejector 3 and the fuel gas recirculation 5 are arranged in a housing 6, which simultaneously comprises the fuel cell stack 1. The ejector 3, the fuel gas recirculation 5 and the fuel cell stack 1 are protected from external influences by the housing 6.Ambient air can be introduced into the housing 6 at an air inlet connection 7 for flushing the housing 6, and the fuel gas exiting from the ejector 3, the fuel gas recirculation 5 and from the fuel cell stack 1 due to leaks can be discharged from the housing 6 with the exhaust gas flow 8 at an exhaust gas outlet connection 9 from the housing 6 into an exhaust line 10. As a result, the fuel gas concentration in the housing 6 is kept below the explosion limit in the housing 6 and the formation of an ignitable mixture of fuel gas and air is reliably avoided. In this way, the ejector 3 and the fuel gas recirculation 5 are arranged in an explosion-proof housing 6.The ejector 3 is preferably arranged, as shown, so as to lie adjacent to a first end 11 of the fuel cell stack 1 in a space-saving manner and is connected directly thereto for the introduction of fuel gas 12 and to the fuel gas recirculation 5. Consequently, additional connecting lines between ejector 3 and fuel cell stack 1 can also be avoided.The first end 11 of the fuel cell stack 1 is formed by a first stack end plate, by means of which the fuel cell stack 1 is braced together with the second stack end plate formed at the second end 13.A media adapter 14 is attached to the outside of the first stack end plate 11. This is designed as a media adapter plate, on which a plurality of connections 15, 16, 17, 18, 19, 20 are provided for mass transfer with the fuel cell stack 1.The ejector 3 is disposed in parallel with the first stack end plate 11 of the fuel cell stack 1. It bears laterally against the media adapter plate 14, so that the connection 15 for introducing a fuel gas stream 12 into the fuel cell stack 1 and the connection 16 for drawing in residual fuel gas from the fuel gas recirculation 5 can each be formed laterally with respect to the main fuel gas stream in the ejector 3.Integrated in the ejector 3 in a space-saving manner is a discharge valve 21, which serves for discharging undesired nitrogen from the residual fuel gas of the fuel gas recirculation 5 to be recirculated. The discharge valve 21 is connected to a discharge line 22 connected to the ejector 3, via which the nitrogen discharged at the discharge valve 21 can be discharged into the exhaust gas flow 8 from the fuel cell stack 1 and can be discharged with the exhaust gas flow 8 from the housing 6.In addition, a water separator 23 for removing undesired water vapor from the residual fuel gas of the fuel gas recirculation 5 to be recirculated is integrated into the ejector 3 in a manner saving further installation space. The water vapor separated at the water separator 23 can be discharged through the discharge valve 21 integrated into the ejector 3 into the discharge line 22 connected thereto and via the latter into the exhaust gas stream 8 and can be discharged together with the exhaust gas stream 8 from the housing 6. In this way, the discharge valve 21 and the discharge line 22 can be used in a dual function, so that additional fittings and connecting lines can be avoided. It is possible in particular to blow out the water vapor separated at the water separator 23 or the separated water together with the separated nitrogen.In the housing 6, a fuel gas inlet valve 24 for controlling the fuel gas flow into the ejector 3 and via the latter into the fuel cell stack 1 is arranged in the fuel gas feed line 4. The suction pressure for the fuel gas recirculation 5 can also be adjusted by the fuel gas inlet valve 24. The fuel gas inlet valve 24 is preferably integrated into or directly connected to a fuel gas supply port 25 on the housing 6. Via the fuel gas supply connection 25, the fuel cell system can be connected to an external fuel gas supply 26 as shown. The fuel gas feed line 4 can be sealed off from the outside in a gas-tight manner by the fuel gas inlet valve 24. The fuel gas supply 26 is connected to a fuel gas reservoir, not shown, in particular a fuel gas tank in a vehicle.A coolant inlet connection 27 and a coolant outlet connection 28 of a coolant circuit 29 for cooling the fuel cell stack 1 are provided on the housing 6. In order to supply the fuel cells 2 with oxidation air via an oxidation air line 30 and to flush the housing 6 with a flushing air stream 31, a common air inlet connection 7 can be formed on the housing. It is also conceivable to provide two separate connections. Ambient air can be conveyed at the air inlet connection 7, for example, via a blower.The fuel gas exiting into the housing 1 due to leakage can, as already mentioned above, be discharged from the housing 6 into the exhaust line 10 with the exhaust gas flow 8 from the fuel cell stack 1 at an exhaust gas outlet connection 9 of the latter.The aforementioned connections 7, 9, 25, 27, 28 are preferably arranged on one side of the housing 6, as shown, whereby the production and assembly are facilitated. For adaptation to the installation conditions, the connections 7, 9, 25, 27, 28 can also be arranged on different sides of the housing 6.The coolant circuit 29 is connected to the fuel cell stack 1 via a coolant supply connection 17 and a coolant discharge connection 18 on the media adapter plate 14. For connecting the fuel cell stack 1 to the oxidation air train 31, a connection 19 is provided on the media adapter plate 14. The exhaust gas flow 8 is discharged from the fuel cell stack 1 via an exhaust gas connection 20 of the media adapter plate 14.Accordingly, all fuel gas-carrying components of the fuel cell system are integrated into an explosion-proof housing 6. Leaks are thus protected by the housing 6. In addition, the power density of the fuel cell system is increased.List of reference characters1 Fuel cell stack 2 Fuel cell 3 Ejector 4 Fuel gas supply line 5 Fuel gas recirculation 6 Housing 7 Air inlet connection 8 Exhaust gas flow 9 Exhaust gas outlet connection 10 Exhaust gas line 11 First end, first stack end plate 12 Fuel gas 13 Second end, second stack end plate 14 Media adapter, media adapter plate 15 Connection Fuel gas 16 Connection Fuel gas recirculation 17 Coolant supply connection 18 Coolant discharge connection 19 Connection Oxidation air line 20 Exhaust gas connection 21 Discharge valve 22 Discharge line 23 Water separator 24 Fuel gas inlet valve 25 Fuel gas supply connection 26 Fuel gas supply 27 Coolant inlet connection 28 Coolant outlet connection 29 Coolant circuit 30 Oxidation air line 31 Scavenging air flowReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedEP 2 008 332 B1

[0002]

Claims

Fuel cell system for a vehicle, having a plurality of fuel cells (2) arranged in a fuel cell stack (1), an ejector (3) arranged for introducing fuel gas into the fuel cell stack (1) and a fuel gas recirculation (5) for recirculating residual fuel gas into the fuel cell stack (1), characterized in that the ejector (3) and the fuel gas recirculation (5) are arranged in a housing (6), wherein the housing (6) simultaneously comprises the fuel cell stack (1) and ambient air can be introduced into the housing (6) for flushing the housing (6), and the fuel gas emerging from the ejector (3), the fuel gas recirculation (5) and from the fuel cell stack (1) owing to leaks can be discharged from the housing (6).Fuel cell system according to Claim 1, characterized in that the ejector (3) is arranged so as to abut one end (11) of the fuel cell stack (2) and is connected directly thereto for the introduction of fuel gas and for the fuel gas recirculation (5).Fuel cell system according to either of Claims 1 and 2, characterized in that the ejector (3) is arranged parallel to a stack end plate (11) of the fuel cell stack (1) in such a way that the connections (15, 16) for introducing fuel gas into the fuel cell stack (1) and for drawing in residual fuel gas from the fuel gas recirculation (5) are formed laterally with respect to the main fuel gas flow in the ejector (3).Fuel cell system according to one of Claims 1 to 3, characterized in that the ejector (3) has integrated therein a discharge valve (21) for discharging nitrogen from the residual fuel gas of the fuel gas recirculation (5) to be recirculated.Fuel cell system according to Claim 4, characterized in that the discharge valve (21) is connected to a discharge line (22) connected to the ejector (3) and the nitrogen can be discharged from the housing (6) via said discharge line into the exhaust gas stream (8) and can be discharged from the housing (6) together with the exhaust gas stream (8).Fuel cell system according to one of Claims 1 to 5, characterized in that a water separator (23) for removing water vapor from the residual fuel gas of the fuel gas recirculation (5) to be recirculated is integrated into the ejector (3).Fuel cell system according to Claim 6, characterized in that the water vapor separated off at the water separator (23) can be discharged from the housing () through the discharge valve (21) into the discharge line (22) connected to the ejector (3) into the exhaust gas stream (8) and can be discharged from the housing (6) together with the exhaust gas stream (8).Fuel cell system according to one of Claims 1 to 7, characterized in that a fuel gas feed valve (24) for controlling the fuel gas feed to the ejector (3) is arranged in the fuel cell stack (2) in the housing (6).Fuel cell system according to Claim 8, characterized in that the fuel gas feed valve (24) is integrated into a fuel gas feed connection (25) on the housing (6) or is connected directly to the latter, and a fuel gas supply (26) can be connected to the fuel gas feed connection (25).Fuel cell system according to one of Claims 1 to 9, characterized in that a coolant inlet connection (27) and a coolant outlet connection (28) of a coolant circuit (29) for cooling the fuel cell stack (2), an air inlet connection (7) for supplying the fuel cells (2) with oxidation air via an oxidation air train (30) and for flushing the housing (6) with a flushing air stream (31), and an exhaust gas outlet connection (9) are provided on the housing (6), at which connection the fuel gas which escapes into the housing (6) as a result of leakage can be discharged from the housing (6) together with the exhaust gas stream.

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