Fuel cell system, method for operating a fuel cell system, and vehicle

Abstract

The invention relates to a fuel cell system (100) comprising at least one fuel cell stack (101) and at least one air system (10) comprising an intake path (11) upstream of the at least one fuel cell stack (101) and an exhaust path (12) downstream of the at least one fuel cell stack (101), the air system (10) comprises at least one heat exchanger (13) for heat transfer between a fluid flow conducted in the intake path (11) and a fluid flow conducted in the exhaust path (12), the air system comprises an extraction path (14) for extracting a fluid flow from the exhaust path (12) at an extraction point (14.1), and wherein the extraction point (14.1) is located between the heat exchanger (13) and the extraction path (14). The extraction point (14.1) is arranged downstream of the heat exchanger (13) in the exhaust gas path (12).

Description

Technical Field

[0001] The present invention relates to a fuel cell system, a method for operating the fuel cell system, and a vehicle. Background Technology

[0002] In fuel cell vehicles (FCVs), which are primarily powered by one or more fuel cell systems (FCS), oxygen from the ambient air is typically used as an oxidant to react with hydrogen in the fuel cell, producing water and / or water vapor, which is then converted into electrical energy via electrochemical processes. For this purpose, an air system supplies ambient air to the fuel cell stack and exhausts the moist exhaust gases generated after the stack (the cathode path of the fuel cell system).

[0003] Therefore, a particularly variable air mass flow and corresponding pressure level are required during the intake of the cathode path for the fuel cell stack. The air is typically compressed by one or more thermofluid machines, particularly air compressors, arranged in the intake path of the air system. These thermofluid machines are preferably driven by an electric motor and / or a turbine arranged in the exhaust path of the air system. When driven by a turbine in this way, energy can be recovered from the humid air exiting at least one fuel cell stack, thus enabling more energy-efficient operation of the fuel cell system.

[0004] Medium system pressures can be achieved using single-stage compression. Higher system pressures require multi-stage compression using at least two air compressors arranged in series, and energy recovery using one or more turbines if necessary.

[0005] Because air heats up during compression, it is advantageous to cool the compressed intake air directed toward the fuel cell stack. In particular, the relatively warm or hot compressed intake air can be cooled in the air system's intake path by means of the relatively cool exhaust gas in the air system's exhaust path, thus avoiding or at least enabling a smaller coolant loop.

[0006] Another key aspect of operating a PEM fuel cell stack (PEM, proton exchange membrane) is water management within the membrane, and consequently, water management in the cathode path of the fuel cell system. The membrane must be sufficiently wetted to conduct protons. The risk of dryness is particularly high in the cathode inlet region. One possibility for preventing membrane dryness is to humidify the intake air leading to the fuel cell stack using the exhaust gas flow from the fuel cell stack.

[0007] The exhaust gas flow is humid and thus suitable for humidifying the intake and membrane; however, it may also contain liquid water (water droplets). Furthermore, condensation and additional liquid water accumulation can occur when the exhaust gas flow is transferred to the intake. Liquid water in the intake path can have detrimental effects; water droplets in the intake path can cause serious damage to the air compressor's blades and bearings and harm other components in the intake path, such as sensors. Summary of the Invention

[0008] This invention relates to a fuel cell system, a vehicle having such a fuel cell system, a method for operating the fuel cell system, a computer program product, a computer-readable medium, and a data carrier signal. Features and details relating to the fuel cell system of this invention also apply to features and details relating to the vehicle of this invention, features and details relating to the method of this invention, features and details relating to the computer program product of this invention, features and details relating to the computer-readable medium of this invention, or features and details relating to the data carrier signal, and vice versa; therefore, disclosures regarding various aspects of the invention can always be referenced cross-referenced.

[0009] This invention is particularly useful for enabling safe, reliable, and energy-efficient operation of fuel cell systems.

[0010] According to a first aspect, the present invention relates to a fuel cell system comprising at least one fuel cell stack and at least one air system, particularly a first air system. The air system includes an intake path located upstream of the at least one fuel cell stack and an exhaust path located downstream of the at least one fuel cell stack. This description relates to the fluid guidance within the air system or fuel cell system during specified use. In other words, the intake path is used to supply air to the fuel cell stack, i.e., to guide the intake air to the fuel cell stack. The exhaust path is used to discharge exhaust gases generated on the fuel cell stack. Specifically, regarding the specified fluid guidance in the air system, at least one fuel cell stack is arranged between the intake path and the exhaust path.

[0011] The air system also includes at least one heat exchanger for heat transfer between the fluid flow directed in the intake path and the fluid flow directed in the exhaust path. The at least one heat exchanger is preferably configured as a gas-to-gas heat exchanger. Alternative implementations of the heat exchanger, such as a gas-to-liquid heat exchanger, are also contemplated.

[0012] Furthermore, according to the present invention, the air system includes an extraction path for extracting fluid flow from the exhaust path at an extraction point, wherein the extraction point is arranged downstream of the heat exchanger in the exhaust path. For the purposes of this invention, the term "upstream and downstream" refers to fluid guidance in the air system during the intended use of the fuel cell system. The extraction point is a location in the exhaust path where the exhaust path and the extraction path are fluidly connected or connectable, such that fluid can be diverted from the exhaust path to the extraction path.

[0013] Various advantages can be derived from the described structure of the fuel cell system. Therefore, the use of a heat exchanger can improve the energy efficiency of the fuel cell system. Furthermore, arranging the extraction section downstream of the heat exchanger in the exhaust path allows for the extraction of fluids at the highest possible temperature from the exhaust gas stream. Due to the increased temperature, the extracted fluid or exhaust gas stream can carry more water in the gas phase. Therefore, when the extracted fluid is transferred to the intake path of an air system (cathode gas recirculation or CGR) or another air system's intake path (cathode gas transfer or CGT), the amount of liquid water introduced into the intake path is reduced. This better protects components arranged in the intake path from the effects of liquid water (droplets, water films, etc.) and results in safer and more reliable operation of the fuel cell system overall.

[0014] Fuel cell systems are preferably used in mobile applications, such as in vehicles, particularly fuel-powered vehicles, and especially in the commercial vehicle sector where long service life is required. Fuel cell systems can be used as the primary energy supply unit for vehicles. Additionally or alternatively, in the sense of this invention, fuel cell systems can be used as energy supplies for secondary and / or auxiliary drive units in vehicles, such as hybrid vehicles. However, fuel cell systems can also be used in stationary applications, such as generators.

[0015] A fuel cell system can have multiple fuel cell stacks (referred to as stacks), each containing multiple stacked fuel cells and associated functional systems, including: a dielectric system (air or cathode system, fuel or anode system, cooling system), and an electrical system. Preferably, a fuel cell system can include multiple modules, which are in the form of a single stack with multiple stacked fuel cells. Preferably, at least one fuel cell stack can be configured as a PEM fuel cell stack. In other words, at least one fuel cell stack can include multiple stacked PEM fuel cells.

[0016] Advantageously, at least one heat exchanger can be arranged downstream of at least one air compressor in the intake path. This means that the fluid flow guided in the intake path is directed or diverted to the heat exchanger downstream of at least one air compressor. In particular, at least one heat exchanger can be arranged downstream of all air compressors located in the intake path. This achieves the advantage that, since the intake air temperature increases with increasing compression, heat can be transferred more efficiently to the fluid guided in the exhaust path.

[0017] Additionally or alternatively, it may be advantageous to arrange at least one heat exchanger in the exhaust path upstream of at least one expansion device, particularly the turbine. This means that the fluid flow guided in the intake path is directed or diverted to the heat exchanger upstream of at least one expansion device. In particular, it may be arranged that at least one heat exchanger is located upstream of all turbines in the exhaust path. This achieves the advantage that the fluid guided in the exhaust path can be further heated before entering the turbine, thereby increasing the power output to the turbine.

[0018] In particular, at least one heat exchanger may be arranged downstream of at least one air compressor, especially all air compressors in the intake path, and upstream of at least one expansion device, especially all turbines in the exhaust path, with respect to the intake path.

[0019] In this invention, the extraction point is preferably positioned upstream of at least one expansion device located in the exhaust path. In particular, the extraction point can be positioned upstream of all expansion devices located downstream of the heat exchanger in the exhaust path. This ensures that the fluid with the highest temperature guided in the exhaust path is used to humidify the fluid guided in the intake path.

[0020] An expansion device should currently be understood as a device constructed for reducing or expanding a fluid from a higher pressure to a lower pressure. In particular, an expansion device may be an expansion valve, a throttle valve, or a turbine.

[0021] In this invention, it is advantageous if the extraction section is configured to divert the fluid flow entering the extraction path from the exhaust path in a manner free of a significant proportion of liquid water. This can be achieved, for example, by utilizing the increased inertia of liquid water relative to the airflow. Therefore, the exhaust path may, in particular, have a bend at the extraction section, within which the extraction path diverts the fluid from the exhaust path. Additionally or alternatively, a swirling flow can be generated in the exhaust path, allowing the liquid water to be centrifuged outwards and diverted from the internal flow region to exhaust gas free of a significant proportion of liquid water. Known fluid elements can be used to generate the swirling flow. Additionally or alternatively, it is advantageous to locally accelerate the fluid guided in the exhaust path (particularly by at least one nozzle) in the extraction section region. Additionally or alternatively, the extraction section may be arranged in a dead water region located within at least one baffle in the exhaust path. The proportion of liquid water in the fluid guided in the extraction path can be further reduced by one or more of the above measures, thereby enabling a reduction in the liquid water entering the intake path.

[0022] Furthermore, for the purposes of this invention, it is advantageous if the fluid guided in the extraction path can be introduced at least partially, and especially entirely, into the intake path at the introduction point, wherein the introduction point is preferably arranged in the intake path upstream of at least one air compressor, especially a first air compressor, located in the intake path. In other words, the extraction path and the intake path can be configured to be fluidly connected or connectable, such that fluid introduced from the exhaust path into the extraction path can be introduced into the intake path.

[0023] The fluid inlet in the intake path is preferably located upstream of at least one air compressor in the intake path. Particularly with respect to the use of multiple air compressors in the intake path, arranging the inlet between two air compressors, i.e., downstream of a first air compressor and upstream of a second air compressor in the intake path, has proven particularly advantageous. Furthermore, according to the invention, the inlet can be positioned downstream of at least one air filter in the intake path.

[0024] Furthermore, for the purposes of this invention, it is conceivable that at least one air compressor located in the intake path is driven or capable of being driven by a turbine and / or an electric drive unit, particularly an electric motor, arranged in the exhaust path. In particular, regarding the energy-efficient operation of fuel cell systems, a combination of an electric drive unit and a turbine to drive at least one compressor has proven advantageous. To at least partially drive the compressor by the turbine, fluid guided in the exhaust path can be expanded in the turbine, and the fluid work performed can be used to drive a drive shaft through which the turbine drives the compressor.

[0025] Furthermore, for the purposes of this invention, it is advantageous to arrange the fluid flow guided in the extraction path to be at least partially introduced at the inlet point into the intake path of another air system, particularly a second air system, wherein the inlet point is arranged upstream of at least one air compressor located in the intake path. In particular, the arrangement of the inlet point described so far can also be applied to the arrangement of the inlet point in another air system. All the features described with respect to the first air system can also be applied to the second air system. In particular, the air systems can be constructed identically or substantially identically. The second air system can be included in the fuel cell system and / or, particularly in the manner already described, for the air supply of at least one fuel cell stack.

[0026] Fuel cell systems, particularly air systems, preferably include at least one temperature sensor for detecting the fluid temperature in the intake and / or exhaust paths. Multiple temperature sensors may be provided. In particular, temperature sensors can be used to determine the direction of heat transfer in a heat exchanger. Furthermore, at least one temperature sensor can be configured to determine the temperature of the fluid guided in the exhaust path, particularly at the extraction point.

[0027] Additionally or alternatively, the fuel cell system or air system may include at least one valve, through which fluid flow in at least one path of the air system, particularly an intake path, an exhaust path, and / or an extraction path and / or at least one bypass path, can be blocked or released.

[0028] The fuel cell system preferably includes at least one control unit. The control unit may be configured, in particular, to control the flow of the method for operating the fuel cell system according to the present invention. At least one control unit may include a unit for data processing. The unit for data processing may preferably include at least one processor and / or working memory and / or non-volatile data memory.

[0029] At least one control unit is capable of establishing a signal connection, at least temporarily, with at least one temperature sensor and / or at least one valve and / or air compressor and / or turbine and / or other components of the fuel cell system. Therefore, for example, the control unit can receive and analyze sensor values ​​for evaluation, and send control signals, such as for closing or opening a valve.

[0030] The fuel cell system can be configured to include at least one heating device, particularly an electric heating device, for heating at least one heat exchanger. This allows the heat exchanger to reach operating temperature more quickly during cold start-up of the fuel cell system, thereby enabling a faster transition to more energy-efficient process control. In particular, this allows for earlier release of the extraction path or a reduction in the liquid water content at the extraction point of the fluid flow guided in the exhaust path.

[0031] According to a second aspect, the invention also relates to a vehicle comprising at least one fuel cell system according to the invention, particularly the aforementioned fuel cell system. Therefore, the vehicle according to the invention has the same advantages as the fuel cell system according to the invention. The vehicle can be an automobile, particularly a passenger car, or a commercial vehicle, particularly a truck. Alternatively, the vehicle configuration can be construction machinery or an agricultural commercial vehicle.

[0032] According to a third aspect, the present invention relates to a method for operating a fuel cell system according to the invention, particularly the aforementioned fuel cell system. The method includes the following: - Detect the direction of heat transfer in the heat exchanger and / or the extraction temperature of the fluid flow guided in the exhaust path at the extraction point; and - Depending on the direction of heat transfer and / or the extraction temperature, fluid may be prevented or allowed to enter the extraction path, or to enter the intake path from the extraction path of at least one fuel cell system.

[0033] The method has the same advantages as the fuel cell system according to the invention and / or the vehicle according to the invention.

[0034] Detecting the direction of heat transfer currently refers to determining whether the fluid guided in the intake path transfers heat to the fluid guided in the exhaust path, or vice versa. For example, this can be achieved by measuring the temperature upstream and downstream of the heat exchanger in both the intake and exhaust paths, thereby determining whether the corresponding fluid flow through the heat exchanger is heating or cooling.

[0035] Especially after the fuel cell system starts up, while the components are still cooling, reverse heat transfer from the exhaust path to the intake path may occur compared to normal operation. In this case, the fluid guided in the exhaust path is cooled and has an undesirable effect, causing more water to condense in this operating state, and thus more liquid water will be introduced into the intake path when the fluid moves to it. To avoid this, fluid input into the extraction path or intake path can be prevented in this situation. Conversely, if heat transfer proceeds as desired from the intake path to the exhaust path, fluid input into the extraction path can be released. For example, fluid input can be prevented by closing a valve arranged in the extraction path, and fluid input can be released accordingly by opening the valve.

[0036] Additionally or alternatively, the extraction path can be blocked or released based on the temperature of the fluid flow guided in the exhaust path at the extraction point. Therefore, the extraction path can be released in particular when the temperature at the extraction point (extraction temperature) reaches or falls below a temperature limit.

[0037] Furthermore, it is advantageous that the method also includes the following: - Increase the power input to at least one air compressor arranged in the intake path, and at least partially divert the fluid flow guided in the intake path to the exhaust path via at least one bypass path connected in parallel with at least one fuel cell stack or located upstream of at least one fuel cell stack.

[0038] This increases the fluid temperature in the intake path, after the compressor or before the heat exchanger. Therefore, the fuel cell system can reach operating temperature and transition to specified operation more quickly. By at least partially bypassing the fuel cell stack, moisture in the exhaust path can also be reduced, as compressed air mixes with the exhaust gases from the fuel cell stack.

[0039] According to a fourth aspect of the invention, a computer program product is provided, comprising instructions that cause a fuel cell system according to the invention, particularly the aforementioned fuel cell system, to execute the method according to the invention, particularly the aforementioned method. This computer program product possesses the same advantages as a fuel cell system according to the invention and / or a vehicle according to the invention and / or a method according to the invention.

[0040] According to a fifth aspect of the invention, a computer-readable medium, particularly a storage medium, is provided, on which a computer program product according to the invention, particularly the aforementioned computer program product, is stored. This computer-readable medium possesses the same advantages as the fuel cell system according to the invention and / or the vehicle according to the invention and / or the method according to the invention and / or the computer program product according to the invention.

[0041] According to a sixth aspect of the invention, a data carrier signal is provided that transmits data according to a computer program product of the invention, particularly the aforementioned computer program product. This data carrier signal possesses the same advantages as the fuel cell system and / or vehicle and / or method and / or computer program product and / or storage medium of the invention. Attached Figure Description

[0042] Other advantages, features, and details of the invention will become apparent from the following description, which details embodiments of the invention in conjunction with the accompanying drawings. The features mentioned in the claims and description may constitute key features of the invention, individually or in any combination.

[0043] Here, the following are illustrated schematically: Figure 1 A view of a fuel cell system. Figure 2 A view of a fuel cell system. Figure 3 A view of a fuel cell system. Figure 4 View of the vehicle Figure 5 : A schematic diagram of the method. Detailed Implementation

[0044] Figure 1 A schematic diagram of a fuel cell system 100 is shown, which includes at least one fuel cell stack 101 and at least one air system 10.

[0045] The air system 10 includes an intake path 11 located upstream of at least one fuel cell stack 101 and an exhaust path 12 located downstream of at least one fuel cell stack 101. Figure 1 As can be seen, the intake path 11 is configured to deliver air from the ambient ENV to the fuel cell stack 101. The exhaust path 12 is configured to deliver exhaust gas from the fuel cell stack 101 to the ambient ENV.

[0046] although Figure 1 Only one fuel cell stack 101 is shown, but a fuel cell system may include multiple fuel cell stacks 101. In particular, relative to... Figure 1 The circuit diagram shown indicates that multiple fuel cell stacks can be arranged in parallel and are supplied with air through the same system 10.

[0047] The air system 10 includes at least one heat exchanger 13 for heat transfer between a fluid flow guided in the intake path 11 and a fluid flow guided in the exhaust path 12; and an extraction path 14 for extracting fluid flow from the exhaust path 12 at an extraction point 14.1. Here, from Figure 1 As can be seen, the extraction part 14.1 is arranged downstream of the heat exchanger 13 in the exhaust path 12.

[0048] The heat exchanger 13 is currently arranged downstream of at least one air compressor 16 relative to the intake path 11 and, in addition, upstream of at least one expansion device 15 relative to the exhaust path 12, wherein the expansion device 15 is configured as a turbine 18.

[0049] In addition, from Figure 1 As can be seen, the extraction section 14.1 is arranged in the exhaust path upstream of at least one expansion device 15 or turbine 18 located in the exhaust path 12. The turbine 18 is mechanically coupled to an air compressor 16 arranged in the intake path 11, particularly via a shaft coupling, in order to drive the air compressor. Furthermore, the air compressor 16 is driven by an electric motor 19.

[0050] from Figure 1It can also be seen that the fluid flow guided in the extraction path 14 can be introduced into the intake path 11 at least partially at the inlet portion 14.2, wherein the inlet portion 14.2 is arranged in the intake path 11 upstream of the air compressor 16 located in the intake path 16. In addition, the inlet portion 14.2 is located downstream of the air filter 17 arranged in the intake path 11.

[0051] from Figure 1 It can also be seen that the fuel cell system 100 includes a bypass path 22 connected in parallel with or located upstream of the fuel cell stack 101, through which the fluid flow guided in the intake path 11 can at least partially bypass the fuel cell stack 101.

[0052] Figure 2 A schematic diagram of another fuel cell system 100 is shown. (Compared to...) Figure 1 Unlike the fuel cell system 100, the expansion device 15 arranged downstream of the extraction section 14.1 in the exhaust path 12 is configured as an expansion valve 20.

[0053] also, Figure 2 The fuel cell system 100 is implemented such that the fluid flow guided in the extraction path 14 can be introduced at least partially at the inlet 14.2 into the intake path 11 of another air system, which is only schematically shown. Here, the inlet 14.2 is located upstream of at least one air compressor 16 arranged in the intake path of the other air system.

[0054] Figure 3 A schematic diagram of another fuel cell system is shown, and Figure 1 and Figure 2 In contrast, this other fuel cell system uses two air compressors 16 arranged in series for multi-stage compression in the intake path 11. Here, the inlet portion 14.2 is arranged between the air compressors 16 and is therefore located downstream of the first air compressor 16 and upstream of the second air compressor 16.

[0055] Figures 1 to 3 The fuel cell system 100 also includes a control unit 21 for at least partially controlling the respective fuel cell system 100.

[0056] Figure 4 A schematic diagram of a vehicle 50 is also shown, which includes at least one fuel cell system 100, not shown in detail.

[0057] also, Figure 5 A schematic diagram of a method 200 for operating a fuel cell system 100 is also shown, the method 200 including: - Detect the direction of heat transfer in heat exchanger 13 and / or extract the extraction temperature of the fluid flow guided in exhaust path 12 at extraction point 14.1; and - Prevent or release fluid 220 from entering the extraction path 14 based on the direction of heat transfer and / or extraction temperature.

[0058] The above description of the embodiments illustrates the invention only within the scope of examples. Of course, the various features of the embodiments can be freely combined with each other without departing from the scope of the invention, provided it is technically reasonable.

Claims

1. A fuel cell system (100), comprising: At least one fuel cell stack (101) and at least one air system (10). The air system (10) includes an intake path (11) located upstream of the at least one fuel cell stack (101) and an exhaust path (12) located downstream of the at least one fuel cell stack (101). The air system (10) includes at least one heat exchanger (13) for heat transfer between a fluid flow guided in the intake path (11) and a fluid flow guided in the exhaust path (12). The air system includes an extraction path (14) for extracting fluid flow from the exhaust path (12) at an extraction point (14.1), and The extraction section (14.1) is located downstream of the heat exchanger (13) in the exhaust path (12).

2. The fuel cell system (100) according to claim 1. Its features are, The extraction part (14.1) is arranged in the exhaust path (12) upstream of at least one expansion device (15) located in the exhaust path (12).

3. The fuel cell system (100) according to any one of the preceding claims. Its features are, The extraction section (14.1) is configured to divert the fluid flow entering the extraction path (14) from the exhaust path (12) in a manner that does not contain a significant proportion of liquid water.

4. The fuel cell system (100) according to any one of the preceding claims. Its features are, The fluid flow guided in the extraction path (14) can be at least partially introduced into the intake path (11) at the inlet (14.2), wherein the inlet (14.2) is arranged in the intake path (11) upstream of at least one air compressor (16), particularly the first air compressor, located in the intake path (11).

5. The fuel cell system (100) according to claim 4. Its features are, The inlet portion (14.2) is arranged in the intake path (11) downstream of at least one air compressor (16), particularly a second air compressor, located in the intake path (11).

6. The fuel cell system (100) according to claim 4 or 5. Its features are, The inlet portion (14.2) is arranged in the air intake path (11) downstream of at least one air filter (17) located in the air intake path (11).

7. The fuel cell system (100) according to any one of the preceding claims. Its features are, At least one air compressor (16) arranged in the intake path (11) can be driven by a turbine (18) and / or an electric drive (19) arranged in the exhaust path (12).

8. The fuel cell system (100) according to any one of the preceding claims. Its features are, The fluid flow guided in the extraction path (14) can be at least partially introduced at the inlet (14.2) into the intake path (11) of another air system (10), particularly the second air system, wherein the inlet (14.2) is arranged in the intake path (11) upstream of at least one air compressor (16) located in the intake path (11).

9. A vehicle (50) comprising a fuel cell system (100) according to any one of the preceding claims.

10. A method (200) for operating a fuel cell system (100) according to any one of claims 1 to 8, the method (200) comprising: - Detect (210) the direction of heat transfer in the heat exchanger (13) and / or the extraction temperature of the fluid flow guided in the exhaust path (12) at the extraction point (14.1); and - Prevent or release (220) fluid input into the extraction path (14) based on the heat transfer direction and / or the extraction temperature.

11. The method (200) according to claim 10. Its features are, The method also includes: - Increase the power input to at least one air compressor arranged in the intake path (11) and at least partially transfer the fluid flow guided in the intake path (11) to the exhaust path (12) via at least one bypass path (22) connected in parallel with the at least one fuel cell stack (101).

12. A computer program product comprising instructions that cause a fuel cell system (100) according to any one of claims 1 to 8 to perform the method according to claim 10 or 11.

13. A computer-readable medium having stored thereon a computer program product according to the preceding claims.

14. A data carrier signal for transmitting a computer program product according to claim 12.

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