Apparatus 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 delivery device (11) and at least one humidification device, which inputs product water condensed from the fuel cell (3) into the compressed incoming air stream through at least one nozzle (171-178). The device is characterized in that a field (15) of double-component nozzles (171-178) for inputting water is formed in the flow cross section of the incoming air stream, wherein for each double-component nozzle (171-178) a separate flowable cross section (161-168) is formed, each of which comprises a valve (22) having a valve seat (24) and a valve body (23), which is pressed by a return force in the direction opposite the flow against the valve seat (24).

Description

Technical Field

[0001] This invention relates to an apparatus for supplying air to a fuel cell, the apparatus having at least one air delivery device and at least one humidification device configured to input condensate from the fuel cell into a compressed inlet air stream via at least one nozzle. Furthermore, the invention also relates to a fuel cell system having such an apparatus. Background Technology

[0002] The air supply for fuel cells is typically provided by an air delivery device, such as a bladed mechanism, which is electrically driven and, if necessary, assisted by an exhaust air turbine. This structure is commonly referred to as an "electric turbocharger," "ETC," or "electrically assisted turbocharger." Here, the intake air supplied to the fuel cell is heated accordingly after compression. This is a serious disadvantage in cryogenic fuel cells, especially PEM fuel cells, and a booster air cooler is incorporated into many conventional structures. This booster air cooler cools the air before it flows through a humidifier and is humidified accordingly for use in the fuel cell. This structure is large and complex and causes pressure losses in the intake air flow. In particular, the booster air cooler here has the disadvantage that it additionally loads the cooling circuit of the fuel cell system. Because it is already difficult to remove waste heat from the fuel cell system at the relatively low temperature level, typically below 100°C to 120°C, the additional heat input through the booster air cooler is a significant drawback.

[0003] DE 10 2004 038 633 B4 now proposes to humidify the air by introducing the condensate from the fuel cell system into a heat exchanger that serves as a booster air cooler via an injector. Therefore, on the one hand, the product water of the fuel cell is consumed, and on the other hand, the humidifier designed as a gas / gas humidifier, such as a membrane humidifier, can be eliminated. However, a load is still applied to this cooling loop.

[0004] DE 10 2017 214 312 A1 humidifies the incoming airflow to the fuel cell using water condensed from the fuel cell system and injected through a jet valve into the volumetric flow after the compressor. This achieves humidification and eliminates the need for a conventional humidifier. The topic of pressurized air cooling is not relevant here and is not mentioned. Summary of the Invention

[0005] The object of the present invention is now to provide an improved device for supplying air to a fuel cell, according to the type detailed at the beginning.

[0006] According to the present invention, this objective is achieved by a device having the following features. A fuel cell system having such a device is also described.

[0007] The device according to the invention uses nozzles to humidify the incoming airflow, similar to that in the prior art. Here, according to the invention, a field / region for the input of condensate water is formed in the cross-section of the incoming airflow. Here, each of the two-component nozzles can be provided with a separate flowable cross-section, so that each nozzle is targeted by its airflow. This makes it simple and very efficient to design the two-component nozzles appropriately for the volumetric flow rate of the air to be humidified. Each of the separate flowable cross-sections here includes a valve seat and a valve body, the valve body being subjected to a restoring force in the direction opposite to the flow, for example by a spring or other restoring element, toward the valve seat.

[0008] According to a particularly advantageous design of the device according to the invention, a restoring force is provided for each of the separated flowable cross sections, wherein at least two of the separated flowable cross sections have different pre-given parameters and / or cross-sectional areas.

[0009] Here, according to a particularly advantageous improvement of the device according to the invention, for each individual, separated flowable cross section, the individual reset forces can be individually preset in the design, so that, depending on the pressure and volumetric flow rate established by the air delivery device, only one or another, or a specific number of valve bodies, are always lifted from the valve seat so that the corresponding two-component nozzle is flowed through and the water input to the corresponding two-component nozzle is atomized. If all valve bodies are lifted from their valve seats in all separated flowable cross sections, a corresponding cross section designed for the maximum air volumetric flow rate is necessarily provided, in which all two-component nozzles in the field of the two-component nozzles are supplied with water and humidify the volumetric flow.

[0010] It has been confirmed that humidification of the hot volumetric flow following a fluid compressor / turbine compressor / impeller compressor is ideal, as this volumetric flow can, for example, have a temperature on the order of 150°C to 250°C. An advantageous improvement according to the concept allows the input water, preheated via a heat exchanger, particularly by waste heat from the fuel cell system, to ideally evaporate in the volumetric flow. This ensures humidification of the incoming airflow on the one hand, and cooling of the incoming airflow after the air delivery device on the other. Depending on the required incoming airflow, appropriate humidification can be ensured by the passage of a number of separated flowable cross sections adapted to the volumetric flow rate. This allows for an ideal fit. The incoming airflow does not pass through a pressurized air cooler or a membrane humidifier. This design for the air supply equipment eliminates the need for a pressurized air cooler and humidifier, effectively reducing pressure losses in the incoming airflow. Furthermore, it saves on components and the structural space required for components, thus providing another advantage.

[0011] In the design variant already described above (where the condensate is preheated, more precisely, by the waste heat from the fuel cell system itself), this structure also enables the deloading of the fuel cell's cooling circuit. This deloading is achieved not only by eliminating the possibility of a booster air cooler, but also by preheating the condensate using heat from the fuel cell's cooling circuit before atomization. This significantly contributes to further optimizing the cooling circuit's previously critical role in waste heat removal in cryogenic fuel cells.

[0012] Another crucial advantage of this structure lies in the use of a valve body and seat, which are opened as needed by the volumetric flow rate supplied by the air delivery device. If the volumetric flow rate drops below a certain limit or disappears completely, the valve body is pressed or pulled against the valve seat, and the structure is sealed. Thus, as an additional use of the device according to the invention, a passive cathode shut-off valve is produced, which always effectively prevents airflow through the fuel cell when the air delivery device is not operating and therefore airflow through the fuel cell is undesirable.

[0013] Common valves of this type that open automatically under pressure can be operated, for example, by a spring. This has the disadvantage that the spring's restoring force increases with increasing volumetric flow rate and the cross-sectional area of ​​the opening between the valve seat and the valve body. This can cause the valve body to oscillate back and forth, resulting in uneven flow, which can be detrimental to subsequent components and / or metering accuracy due to the resulting pressure fluctuations. According to a highly advantageous improvement of the device according to the invention, magnetic force is therefore used as the restoring force. The magnetic force then acts between a switchable magnet and / or permanent magnet, for example in the region of the valve body, but preferably in the region of the valve seat, and a magnetizable material, such as a steel alloy or iron alloy, in the region of the valve seat, or preferably in the region of the valve body. The valve body can be designed as a hollow sphere made of a magnetizable material. For example, the valve body is designed in the form of a hollow iron or steel ball, preferably with a chemically resistant coating, for example, made of plastic. The valve body is then permanently magnetically and / or electromagnetically held on the valve seat. As the volumetric flow rate increases, the valve body, designed as a hollow sphere with a small mass and responding dynamically accordingly, lifts from the valve seat and releases the flowable cross-section. This flowable cross-section increases with increasing volumetric flow rate. Unlike the case of a spring-loaded ball, in the case of magnetic return force, the return force decreases as the distance between the valve body and the valve seat increases, resulting in a decreasing force-displacement characteristic curve for the valve. This is ideal for both controlling the incoming airflow into the corresponding two-component nozzle and for use as a cathode shut-off valve.

[0014] Another highly advantageous design of the device according to the invention further specifies that water can be delivered directly to the two-component nozzle via a delivery device, such as a delivery pump, or delivered to the two-component nozzle via a collection line. The amount of water used for humidification can be adjusted according to the delivery pressure and the volumetric flow rate delivered. In particular, the use of a collection line here also enables the use of water in other areas of the system surrounding the device, especially in other areas of the fuel cell system surrounding the device. For example, such use of water via a water collection line is substantially described in the applicant's patent application DE 10 2020 206 156 A1.

[0015] The collected water can and should be subjected to appropriate cleaning devices and filters, for example, to mechanically suppress impurities and remove ions accumulated in the water. For instance, a combination of water filters and ion exchanger cartridges can be provided, and these can be arranged, for example, in the area of ​​the collection pipeline, or between the various water separators of such a system and the collection container, which is preferably heated, particularly including the aforementioned heat exchanger. The water flows in the direction of flow through the heat exchanger before the two-component nozzles, and the heat exchanger preferably operates using waste heat from a fuel cell system including a fuel cell.

[0016] Here, the respective separated flowable cross sections with corresponding dual-component nozzles and valves can be arranged directly at the output of the flow compressor, which serves as an air delivery device, according to a highly advantageous improvement of this concept. In this case, "direct" means that no other components are connected between them. In particular, the device according to the invention can be designed such that the valves and dual-fuel nozzles of the separated cross sections are directly flanged at the output of the flow compressor, so that the intake air, cooled and humidified therethrough, is directly or via a short conduit into the cathode chamber of the fuel cell. Here, in the region immediately following the output of the flow compressor, the intake air has the highest temperature, thus ideally allowing for the evaporation of preheated water to both humidify and cool the intake air to a temperature level suitable for the fuel cell.

[0017] Here, according to a particularly advantageous improvement of the device, at least two air delivery devices and / or humidification devices are arranged in a sequential cascade. Two such interconnected humidifier nozzles and / or pressurization stages can be used for staged pressurization as is known per se. This enables greater structural variability and allows for the efficient humidification of different material flows.

[0018] The corresponding air delivery device here can be part of an electrically assisted turbocharger having an air delivery device, an exhaust air turbine, and an electric motor. This structure, commonly known also as an ETC (electric turbocharger) or an electric motor-assisted turbocharger, is ideally suited for efficiently supplying air to fuel cells. In addition to the drive power typically provided by the electric motor, the energy recovered from the exhaust air can be used for compression via the turbine. If there is more energy in the turbine region than is required to drive the air delivery device, the electric motor also operates as a generator to recover and temporarily store this energy as electrical energy. This applies both when using two air delivery devices and when using one air delivery device.

[0019] The entire structure of this device can be integrated into a fuel cell system, which has fuel cells, particularly single-cell stacks, so-called fuel cell stacks. Here, the fuel cell system itself can be used for various stationary or mobile applications. In particular, the fuel cell system can be used to provide electric drive energy for vehicles. Specifically, the fuel cell system is used to supply at least a portion of the electric drive power of a vehicle. Particularly advantageous in such vehicle applications is the reuse of collected byproduct water, eliminating the need for its discharge onto roads; furthermore, the decisive advantages in terms of structural volume, weight, energy efficiency, and component savings achieved by the device according to the invention are a particularly significant advantage. Attached Figure Description

[0020] Further advantageous designs of the device according to the invention arise from the embodiments described in detail below with reference to the accompanying drawings. Herein:

[0021] Figure 1 A fuel cell system with an apparatus according to the invention is shown schematically in a vehicle;

[0022] Figure 2 It shows that according to Figure 1 A sectional view of a portion of the device cut along line II-II; and

[0023] Figure 3 It shows that according to Figure 2 A schematic cross-sectional view taken along line III-III. Detailed Implementation

[0024] exist Figure 1 The illustration shows a vehicle 1, such as a commercial vehicle or passenger car, shown very schematically. At least a portion of its electric drive power is supplied to the vehicle 1 by a fuel cell system 2, which is shown only partially and very simply here. The fuel cell system includes a fuel cell 3 as its core, which is constructed, for example, as a single-cell stack utilizing PEM technology, i.e., a so-called fuel cell stack. Purely exemplary, a common cathode chamber 4 and a common anode chamber 5 are shown here. Hydrogen from the hydrogen storage system 6 is supplied to the anode chamber 5, and residual hydrogen is discharged from the system through an exhaust pipe 7 with a water separator 8. Other variations on the anode side are of course possible here. Since these other variations are minor to the present invention, they will not be discussed further. However, it will be apparent to those skilled in the art that different hydrogen storage systems, different metering devices, and anode circuits with one or more recirculation delivery devices are conceivable and feasible here.

[0025] Air is supplied to the cathode chamber 4 as an oxygen supply via an air supply device 10. A portion of this device 10 is an air delivery unit 11, which can be designed, for example, as part of a so-called electric turbocharger 12. This per se electric turbocharger 12, in addition to the air delivery unit 11, which is preferably designed as a flow compressor, also includes an exhaust air turbine 13 and a motor 14. Its operating principle is known in principle and therefore need not be discussed further.

[0026] Following the air delivery device 11, there is a hot, dry, compressed inlet air flow supplied to the cathode chamber 4 of the fuel cell 3. This compressed inlet air flow preferably enters directly into the respective flowable cross-sections of the two-component nozzles immediately after the air delivery device 11. Figure 2The schematic cross-sectional view shows again the... Figure 1 The field is indicated by 15. The various flowable cross sections are indicated here by reference numerals 161-168. For example, the flowable cross sections may be circular and arranged within the flow cross section of the incoming air. At the center of each individually separated flowable cross section 161-168 are two-component nozzles 171-178, which, on the one hand, are flowed by a volumetric flow of dry, hot air following the air delivery device 11 through the flowable cross sections 161-168, and on the other hand, by... Figure 1 As shown in the diagram, pump 18 is supplied with water. This water is deionized water, which is condensed and collected in fuel cell system 2. Purely exemplary, in Figure 1 The diagram shows two water separators. On the anode side, this is the already mentioned water separator 8; on the cathode side, this is the water separator indicated here by 9 in the exhaust air duct 19 connecting the cathode chamber 4 and the exhaust air turbine 13. The collected product water enters, for example, a tank shown here and indicated by 20, and is preheated in this tank or downstream of the tank via a heat exchanger 21, and then enters the area of ​​the delivery pump 18 so as to be supplied to the respective two-component nozzles 171-178 according to the resulting delivery pressure and the resulting volumetric flow rate. This can be done directly for each of the two-component nozzles 171-178, and switchably via valves if necessary, or via a collection line from which the water flows to the respective two-component nozzle.

[0027] The structure of device 10 can also be modified to allow two or more air delivery devices to be connected in sequence in a cascade. Following each air delivery device are corresponding two-component nozzles 171-178 to humidify the corresponding airflow and provide other functionalities described herein.

[0028] Now Figure 3The illustration again shows one of the separated flowable cross sections in a cross-sectional view, here for example, cross section 164. This cross section includes a two-component nozzle 174 and a valve 22 consisting of a valve body 23 and a valve seat 24. The valve body 23 may preferably be designed as a hollow steel ball with a plastic sheath. In the region of the valve seat 24, there is a permanent magnet 25, which is designed, for example, as a surrounding ring. This permanent magnet applies an attractive force to the valve body 23, such that in the case of small volumetric flow or no volumetric flow, the corresponding flowable cross sections 161-168 are closed by the valve 22. This is especially true when the air delivery device 11 is not operating. Thus, during the pure electric operation of the vehicle 1 or when the vehicle is stopped, the flow of air, such as driving air, through the cathode chamber 4 is prevented by the external wind effect. This is very beneficial in preventing fresh oxygen from seeping into the fuel cell 3, which would cause a so-called air / air start and damage the fuel cell 3 in the event of a later restart.

[0029] Now, as the volumetric flow rate from the air delivery device 11 increases, one valve 22 in each of the corresponding flowable cross sections 161-168 opens, followed by multiple valves. The reset force can be adjusted to open an appropriate number of flowable cross sections 161-168 through their valves 22, adapted to the corresponding volumetric flow rate from the air delivery device 11. For example, initially the central flowable cross section 161, then increasingly more flowable cross sections 161-168 arranged around it, until all flowable cross sections 161-168 are opened through their respective valves 22 at the maximum volumetric flow rate from the air delivery device 11. Once the corresponding flowable cross section 161-168 is opened through the valve 22, air flows through it. If water is simultaneously introduced, it is atomized through the two-component nozzles 171-178 in the dry, hot airflow following the air delivery device 11, allowing the atomized water droplets to evaporate in the volumetric flow. This results in both highly effective cooling and excellent humidification of the incoming airflow. The two-component nozzles 171-178 can be designed to adapt to the corresponding volumetric flow rate, thus always producing ideal atomization of water, and consequently, ideal humidification and cooling. This applies to every volumetric flow rate of the input air, as the valve 22 always passively releases only the flowable cross-section corresponding to the corresponding volumetric flow rate. Simultaneously, all valves 22 together isolate the cathode chamber 4 from the environment when the air delivery device is shut off. This results in a finely stepped characteristic curve, which allows for corresponding adjustments via the delivery pressure and volumetric flow rate of the air delivery device 11 and via the delivery pump 18, to humidify the incoming airflow using water preheated in thermally compressed air from the fuel cell system 2. Here, preheating can be particularly achieved through waste heat from the fuel cell 3 itself in the heat exchanger 21, thereby deloading the cooling system of the fuel cell system 2 and, consequently, the vehicle 1.

Claims

1. An apparatus (10) for supplying air to a fuel cell (3), the apparatus having at least one air delivery device (11) and at least one humidification device, the humidification device being configured to input condensed product water from the fuel cell (3) into a compressed incoming air stream via at least one nozzle, characterized in that, A field (15) is formed in the flow cross section of the incoming airflow, wherein at least one two-component nozzle (171-178) for water input is formed, wherein each of the two-component nozzles (171-178) has a separated flowable cross section (161-168), each of the separated flowable cross sections (161-168) includes a valve (22) having a valve seat (24) and a valve body (23), the valve body being pressed against the valve seat (24) in the opposite direction of the flow by a restoring force.

2. The device (10) according to claim 1, characterized in that, The reset force is formed as a magnetic force between a switchable magnet and / or a permanent magnet in the region of the valve body (23) and a magnetizable material of the valve seat (24), or between a switchable magnet and / or a permanent magnet in the region of the valve seat (24) and a magnetizable material of the valve body (23).

3. The device (10) according to claim 2, characterized in that, The valve body (23) is designed as a hollow sphere made of a magnetizable material.

4. The device (10) according to claim 1, 2 or 3, characterized in that, A reset force is provided for each of the separated flowable cross sections (161-168), wherein at least two of the separated flowable cross sections (161-168) have different pre-given parameters and / or cross-sectional areas.

5. The device (10) according to any one of claims 1 to 3, characterized in that, Water can be delivered directly to the two-component nozzle via a delivery pump (18) or via a collection line to the two-component nozzle (171-178).

6. The device (10) according to any one of claims 1 to 3, characterized in that, Water flows through a heat exchanger (21) in the direction of flow before the two-component nozzles (171-178), and the heat exchanger can operate with the help of waste heat from the fuel cell system (2) including the fuel cell (3).

7. The device (10) according to any one of claims 1 to 3, characterized in that, Separated flowable cross sections (161-168) are arranged directly at the output end of the flow compressor used as an air delivery device (11).

8. The device (10) according to any one of claims 1 to 3, characterized in that, At least two air delivery devices (11) and / or humidification devices are arranged in a sequential cascade.

9. The device (10) according to any one of claims 1 to 3, characterized in that, The incoming airflow does not pass through the pressurized air cooler and membrane humidifier.

10. A fuel cell system (2) having a fuel cell (3) and a device (10) according to any one of claims 1 to 9.

11. The fuel cell system (2) according to claim 10, characterized in that, The fuel cell system is used to supply at least a portion of the electric drive power to the vehicle (1).

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