DEVICE FOR SUPPLYING AIR TO A FUEL CELL

Abstract

The invention relates to a device (10) for supplying air to a fuel cell (3), having at least one air conveying device (11) and at least one humidifying device, which supplies condensed product water from the fuel cell (3) to the compressed supply air flow by means of at least one nozzle (171-178). It is characterized in that a field (15) of two-substance nozzles (171-178) for the supply of water is formed in the flow cross section of the supply air flow, wherein a separated cross section (161-168) through which flow can take place is formed for each of the two-substance nozzles (171-178) and wherein each of the separated cross sections (161-168) through which flow can take place comprises a valve (22) having a valve seat (24) and a valve body (23), which is pressed counter to the flow by a restoring force in the direction of the valve seat (24).

Claims

1. A device for supplying air to a fuel cell, having at least one air conveying device and at least one humidifying device, which is configured to supply condensed product water from the fuel cell to the compressed supply air flow by means of at least one nozzle, wherein a field of two-substance nozzles for the supply of water is formed in the flow cross section of the supply air flow, wherein a separated cross section through which flow can take place is formed for each of the two-substance nozzles, and wherein each of the separated cross sections through which flow can take place comprises a valve having a valve seat and a valve body, which is pressed counter to the flow by a restoring force in the direction of the valve seat.

2. The device as claimed in claim 1, wherein the restoring force is formed as a magnetic force between a switchable and/or permanent magnet in the area of the valve body or preferably in the area of the valve seat and a magnetizable material of the valve seat or preferably the valve body.

3. The device as claimed in claim 2, wherein the valve body is designed as a hollow sphere made of a magnetizable material.

4. The device as claimed in claim 1, wherein the restoring force for each of the separated cross sections through which flow can take place is predetermined, wherein at least two of the separated cross sections through which flow can take place have different specifications and/or cross sectional areas.

5. The device as claimed in claim 1, wherein the water can be conveyed via a conveying pump directly or via a collecting line to the two-substance nozzles.

6. The device as claimed in claim 1, wherein the water flows upstream of the two-component nozzles through a heat exchanger, which is preferably operable by means of waste heat from a fuel cell system comprising the fuel cell.

7. The device as claimed in claim 1, wherein the separated cross sections through which flow can take place are arranged directly in the outlet of a flow compressor used as an air conveying device.

8. The device as claimed in claim 1, wherein at least two air conveying devices and/or humidifying devices are provided as a sequential cascade.

9. The device as claimed in claim 1, wherein the supply air flow is free of an intercooler and a membrane humidifier.

10. A fuel cell system having a fuel cell and a device as claimed in claim 1, in particular for supplying a vehicle with at least part of its electrical drive power.

Description

IN THE FIGURES

[0020] FIG. 1 shows a schematically indicated fuel cell system in a vehicle having a device according to the invention;

[0021] FIG. 2 shows a sectional view through part of the device according to line Il-Il in

[0022] FIG. 1; and

[0023] FIG. 3 shows a schematic sectional view according to line III-III in FIG. 2.

[0024] In the representation of FIG. 1, a very schematically indicated vehicle 1, for example a utility vehicle or a passenger vehicle, can be seen. At least part of its electrical drive power is supplied to this vehicle 1 by a fuel cell system 2, which is indicated here only in parts and in a very simplified manner. This comprises a fuel cell 3 as its core, which is constructed, for example, as a stack of individual cells in PEM technology, as a so-called fuel cell stack. A common cathode chamber 4 and a common anode chamber 5 are indicated here solely by way of example. Hydrogen from a hydrogen storage system 6 is supplied to the anode chamber 5, residual hydrogen leaves the system via an exhaust gas line 7 having a water separator 8. Further variants of the anode side are of course possible. Since these are of secondary importance for the present invention, they will not be discussed further. However, it is clear to a person skilled in the art that different storage systems for the hydrogen, different metering devices, and an anode circuit having one or more recirculation conveying devices and the like are conceivable and possible here.

[0025] Air is supplied to the cathode chamber 4 as an oxygen supplier via a device 10 for supplying air. Part of this device 10 is an air conveying device 11, which can be designed, for example, as part of a so-called electric turbocharger 12. This electric turbocharger 12, which is known per se, comprises an exhaust air turbine 13 and an electric machine 14 in addition to the air conveying device 11, which is preferably designed as a flow compressor. Its mode of operation is known in principle, so that it does not have to be discussed further here.

[0026] After the air conveying device 11 there is a hot and dry compressed supply air flow to the cathode chamber 4 of the fuel cell 3. This now arrives, preferably directly after the air conveying device 11, in a field of individual cross sections through which flow can take place, each having a two-substance nozzle. In the schematic cross section of FIG. 2, this field, designated by 15 in FIG. 1, is indicated again. The individual cross sections through which a flow can take place are designated here by the reference signs 161-168. For example, they can be round and arranged within the flow cross section of the supply air. In the center of each individual separated cross section 161-168 through which flow can take place a two-substance nozzle 171-178 is located, through which, on the one hand, the volume flow, that flows through the cross section 161-168 through which flow can take place, of the air that is hot and dry after the air conveying device 11 flows and which, on the one hand, and is supplied with water via a conveying device 18, as can be seen in the representation of FIG. 1. This water is thereby deionized water, which is condensed out and collected in the fuel cell system 2. Two water separators are indicated purely by way of example in the illustration in FIG. 1. On the one hand, this is the above-mentioned water separator 8 on the anode side, and on the other hand, in an exhaust air line 19 connecting the cathode chamber 4 to the exhaust air turbine 13, this is a cathode-side water separator, designated by 9 here. The product water collected in this way reaches, for example, a tank indicated here as an example and designated by 20 and is preheated therein or in the flow direction downstream thereof via a heat exchanger 21 and then reaches the area of the conveying pump 18, to thus be supplied to the respective two-substance nozzles 171-178 depending on the generated conveying pressure and the generated volume flow. This can, for example, take place directly for each of the two-substance nozzles 171-178 and, if necessary, in a switchable manner via a valve, or via a collecting line, from which a flow takes place against the corresponding two-substance nozzles.

[0027] This structure of the device 10 could also be varied in that two or possibly more of the air conveying devices are connected in series as a sequential cascade. These would then each be followed by a corresponding two-substance nozzle 171-178 to humidify the corresponding airflow and provide the other functionalities described herein.

[0028] In the representation of FIG. 3, one of the separated cross sections through which flow can take place is now shown again in a sectional representation, here for example the cross section 164. It comprises the two-substance nozzle 174 and a valve 22 consisting of a valve body 23 and a valve seat 24. The valve body 23 can preferably be designed as a hollow steel ball having a plastic casing. In the area of the valve seat 24 there is a permanent magnet 25 which is designed, for example, as a circumferential ring. This exerts an attractive force on the valve body 23, so that when there is little or no volume flow via the valve 22, the respective cross section 161-168 through which flow can take place is closed. This is the case in particular when the air conveying device 11 is not in operation. This prevents air from flowing through the cathode space 4, for example travel wind during purely electric operation of the vehicle 1, or when the vehicle is switched off, due to external wind effects. This is of decisive advantage in order to prevent fresh oxygen from penetrating into the fuel cell 3, which would result in what is known as an air/air start and damage the fuel cell 3 in the event of a later restart.

[0029] It is now the case that as the volume flow from the air conveying device 11 increases, first one and then several of the valves 22 in the respective cross sections 161-168 through which flow can take place open accordingly. In particular, the restoring forces can be set in such a way that a suitable number of the cross sections 161 168 through which flow can take place are opened by their valves 22 to match the respective volume flow from the air conveying device 11, for example first the central cross section 161 through which flow can take place and then increasingly the cross sections 161 168 through which flow can take place arranged centrally around it, until at the maximum volume flow from the air conveying device 11, all cross sections 161 168 through which flow can take place are opened by their respective valves 22. As soon as the respective cross section 161 168 through which flow can take place is opened via the valve 22, air flows through it. If water is supplied at the same time, then this is atomized accordingly via the two-substance nozzle 171 178 in the hot and dry air flow downstream of the air conveying device 11, so that the water particles atomized into fine droplets can evaporate in the volume flow. This results in very efficient cooling of the supply air flow on the one hand and very good humidification of the supply air flow on the other hand. The two-substance nozzles 171 178 can thereby be designed in such a way that they are adapted to the respective volume flow, so that there is always ideal atomization of the water and thus ideal humidification and cooling. This applies at every volume flow of the supplied air, since only the number of cross sections through which flow can take place that matches the respective volume flow is ever passively released by the valves 22. At the same time, the valves 22 all together shut off the cathode chamber 4 from the environment when the air conveying device is switched off.

[0030] This results in a fine, stepped characteristic curve, which allows appropriate regulation on the one hand via the delivery pressure and the volume flow of the air conveying device 11 and via the delivery pressure and the volume flow of the conveying pump 18, in order to use water preheated in the hot compressed air from the fuel cell system 1 to humidify the supply air flow. The preheating can take place in particular in the heat exchanger 21 by waste heat from the fuel cell 3 itself, so that this additional use of waste heat relieves the cooling system of the fuel cell system 2 and thus the vehicle 1.