Fuel Cell System Having a Humidified Oxidant Flow

Abstract

A fuel cell system includes at least one fuel cell, an oxidant conveyor, a humidifier and at least one water sink. The oxidant conveyor conveys an oxidant through a supply line to the fuel cell. The humidifier introduces water into the oxidant flow. The humidifier is arranged in and/or downstream of the oxidant conveyor and upstream of the fuel cell. The water sink is arranged between the fuel cell and the oxidant conveyor. The water sink is formed and arranged in the supply line in such a way that it prevents liquid water located in the supply line from flowing to the oxidant conveyor.

Claims

1. A fuel cell system, comprising: at least one fuel cell; an oxidant conveyor, which conveys an oxidant through a supply line to the fuel cell; at least one humidifier, which introduces water into the oxidant flow; and at least one water sink, which is arranged between the at least one fuel cell and the oxidant conveyor, and wherein the at least one water sink is formed adjacent to the oxidant conveyor.

2. The fuel cell system as claimed in claim 1, wherein the water sink is arranged to be a maximum of about 0.2 L away from the oxidant conveyor, wherein L is the distance of the oxidant flow between the oxidant conveyor and a heat exchanger in the supply line.

3. The fuel cell system as claimed in claim 1, wherein the water sink is arranged to be a maximum of about 0.1 L away from the oxidant conveyor, wherein L is the distance of the oxidant flow between the oxidant conveyor and a heat exchanger in the supply line.

4. The fuel cell system as claimed in claim 1, wherein the water sink is arranged to be a maximum of about 0.05 L away from the oxidant conveyor, wherein L is the distance of the oxidant flow between the oxidant conveyor and a heat exchanger in the supply line.

5. The fuel cell system as claimed in claim 1, wherein the humidifier is arranged to be a maximum of about 0.2 L away from the oxidant conveyor, wherein L is the distance of the oxidant flow between the oxidant conveyor and a heat exchanger in the supply line.

6. The fuel cell system as claimed in claim 1, wherein the humidifier is arranged to be a maximum of about 0.1 L away from the oxidant conveyor, wherein L is the distance of the oxidant flow between the oxidant conveyor and a heat exchanger in the supply line.

7. The fuel cell system as claimed in claim 1, wherein the humidifier is arranged to be a maximum of about 0.05 L away from the oxidant conveyor, wherein L is the distance of the oxidant flow between the oxidant conveyor and a heat exchanger in the supply line.

8. The fuel cell system as claimed in claim 2, wherein the humidifier is arranged to be a maximum of about 0.2 L away from the oxidant conveyor, wherein L is the distance of the oxidant flow between the oxidant conveyor and a heat exchanger in the supply line.

9. The fuel cell system as claimed in claim 1, further comprising: a water injection device associated with the water sink; and an adjusting mechanism, wherein the adjusting mechanism is formed to alter a position of the water injection device in the supply line.

10. The fuel cell system as claimed in claim 9, wherein the adjusting mechanism comprises a float, which is fastened to the water injection device, and the adjusting mechanism comprises a joint which connects the water injection device rotatably to the supply line.

11. The fuel cell system as claimed in claim 1, wherein the water sink is formed and arranged in the supply line such that it prevents liquid water located in the supply line from flowing to and/or into the oxidant conveyor.

12. The fuel cell system as claimed in claim 1, wherein the water sink is dimensioned such that it can store sufficient liquid water so that no liquid water flows back into the oxidant conveyor.

13. The fuel cell system as claimed in claim 1, wherein the water sink is fluid-connected to the humidifier and/or to at least one water injection device associated with the water sink.

14. The fuel cell system as claimed in claim 13, wherein the water injection device is arranged immediately adjacent to the water sink in the supply line.

15. The fuel cell system as claimed in claim 13, wherein the water injection device is formed to introduce the liquid water collected in the water sink into the oxidant flow.

16. The fuel cell system as claimed in claim 14, wherein the water injection device is formed to introduce the liquid water collected in the water sink into the oxidant flow.

17. The fuel cell system as claimed in claim 9, wherein the water injection device is formed as an ejector pump.

18. The fuel cell system as claimed in claim 13, wherein the fuel cell system comprises a plurality of water sinks, and wherein the at least one water injection device is fluid-connected to the plurality of water sinks.

19. The fuel cell system as claimed in claim 18, wherein at least one of the plurality of water sinks comprises a closing device which is formed to interrupt the fluid connection between the water sink and the at least one water injection device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a schematic illustration of the fuel cell system 100 disclosed here.

[0023] FIG. 2 is a schematic illustration of a supply line 160 having a water injection device 150.

[0024] FIG. 3 is a cross-sectional view along the line A-A of FIG. 2.

[0025] FIG. 4 is a fuel cell system 100 having a plurality of water sinks 140, 140′.

DETAILED DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 shows a schematic view of the construction of the fuel cell system 100. The fuel cell system 100 includes a fuel cell 110 having a cathode 112 and an anode 114, which are separated from one another by an ion-separator shown here by dashed lines. The supply line 160 has a first end 162, which is connected to the oxidant conveyor 120, for example a compressor 120. The second end 164 of the supply line 160 ends in the cathode 112 of the fuel cell 110. For simplicity, only one fuel cell 110 is shown here. A plurality of fuel cells 110 are preferably combined to form a fuel cell stack. The humidifier 130, which here comprises, for example, an injection nozzle through which water is injected into the oxidant flow O, is arranged at the first end 162 of the supply line 160. A water sink 140 is arranged downstream of the humidifier 130 (c.f. FIG. 2). A second humidifier 130′ is arranged between the heat exchanger or charge air cooler 180 and the water sink 140. A water separator 190, which separates any water from the oxidant flow O a short distance before the fuel cell 110, is furthermore provided between the charge air cooler 180 and cathode-side inlet of the fuel cell 110. Following the electrochemical reaction in the fuel cell, the oxidant O exits the fuel cell as fuel cell exhaust gas A.

[0027] FIG. 2 shows a schematic and enlarged view of a detail of the supply line 160 and the oxidant conveyor 120. The oxidant conveyor 120 is connected to the first end 162 of the supply line 160. The oxidant conveyor 120 is located in a deeper position than other sections of the supply line 160. The oxidant conveyor 120 generates an oxidant flow O. This oxidant flow O has a turbulent flow and a comparatively high temperature. In the region adjacent to the first end 162 of the supply line 160, water is introduced into the supply line 160 by the humidifier 130. This water is distributed in a finely dispersed manner in the turbulent oxidant flow O and, for the most part, evaporates. A second humidifier 130′, which likewise introduces water into the oxidant flow O, is shown further downstream. However, some of the water introduced does not evaporate completely or condenses on the walls of the supply line 160. This results in water collecting on the supply-line walls. In the embodiment shown here, this water flows back into the water sink 140. The water sink is dimensioned such that it can store sufficient liquid water so that no liquid water flows back into the oxidant conveyor 120.

[0028] The liquid water collected in the water sink 140 is introduced back into the oxidant flow 150 through a water injection device formed as an ejector pump. The ejector pump includes an inlet pipe 152 which projects into the water sink 140. The electric head 158 takes in the liquid water through the inlet pipe 152, and this liquid water is then distributed in a finely dispersed manner in the turbulent oxidant flow O. The ejector pump 150 is preferably dimensioned such that, even with low quantities of oxidant flow O, it can introduce sufficient water so that, at most, low quantities of liquid water collect in the water sink 140. The quantity of liquid water in the supply line 160 is thus reduced, which has a positive effect on the cold start behavior. The risk of frozen liquid water damaging the supply line 160 is also considerably reduced. The inlet pipe 152 is connected to a float 156 via a rigid connection. The inlet pipe 152 is furthermore connected to the supply line 160 via a joint 154 and a holder 155. The joint 154 and the float 156 are formed in such a way that they enable the ejector pump 150 to pivot about the joint 154. In particular, with a very low water level, the ejector pump 150 can assume a first position in which the ejector pump impedes the oxidant flow O to a lesser extent than in a second position assumed by the ejector pump 150 when water has collected in the water reservoir 140. In this second position, the ejector 158 is arranged in the oxidant flow O and introduces liquid water into the oxidant flow O.

[0029] FIG. 3 shows a cross-section along the line A-A along FIG. 2. The inlet pipe 152 projects into the liquid water collected in the water sink 140. The liquid water rises in the inlet pipe 152 and is sprayed out through the ejector 158.

[0030] FIG. 4 shows the supply line 160 and a further portion 160′ of the supply line 160. The further portion 160′ can be arranged, for example, further downstream, e.g. near the second end 164 of the supply line 160. Two parallel supply lines 160, 160′ would likewise be usable. Liquid water can collect in the water sinks 140, 140′, as has also been described above with respect to the other figures. The two water sinks 140, 140′ are connected via water lines 170, 170′ to a common water injection device 150 which introduces the collected liquid water of the water sinks 140, 140′ back into the oxidant flow O, preferably in the vicinity of the oxidant conveyor 120, since the evaporation/vaporization can be achieved particularly effectively in this region. The water lines 170, 170′ and the water injection device 150 are preferably formed and arranged in such a way that the liquid water can be taken in passively, i.e. without the use of electrical and/or mechanical energy. An ejector pump 150, for example, can be used for this. The water sinks 140, 140′ here each comprise a closing device 142, 142′ which is formed to interrupt the fluid connection between the respective water sink 140, 140′ and the at least one water injection device 150. To this end, the closing device 142, 142′ can comprise a float, for example, which is connected to a water sink opening valve and opens or closes this latter depending on the water level. If there is no liquid water in the water sink 140′, for example, the valve 142′ is closed and the intake line 170′ does not take in any air. The full intake capacity of the water injection device 150 is then available for the water sink 140. The water sink 140, the supply line 160, the water injection device 150 and the humidifier 130 can otherwise correspond to the remaining figures.

[0031] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.