Method for adjusting a fuel concentration in a fuel cell system, fuel cell system, vehicle, computer program product and storage medium

Abstract

The invention relates to a method for adjusting a fuel concentration in a fuel cell system (10), wherein the fuel cell system (10) comprises a fuel cell (11), a water separator (12), a fuel inlet path (13) for directing fuel to the fuel cell (11), a process gas outlet path (14) for directing process gas (16) from the fuel cell (11) and into the water separator (12), a purge path (17) for directing water and process gas (16) from the water separator (12) into the environment of the fuel cell system (10), and an outlet valve (18) for controlling a mass flow rate through the purge path (17), and wherein the method includes: determining an actual mass flow rate through the purge path (17), determining a reference mass flow rate, carrying out a comparison between the actual mass flow rate and the reference mass flow rate, setting an opening behaviour of the outlet valve (18) based on the comparison. The invention further relates to a fuel cell system (10), a vehicle (100), a computer program product (50) and a computer-readable storage medium (60).

Description

[0001] Description

[0002] Method for adjusting a fuel concentration in a fuel cell system, fuel cell system, vehicle, computer program product and storage medium

[0003] The technology disclosed here relates to a method for adjusting a fuel concentration in a fuel cell system, and in particular in a fuel cell system of a vehicle. The technology further relates to a fuel cell system and a vehicle for carrying out the method. Furthermore, the described technology relates to a computer program product for carrying out the method and a computer-readable storage medium on which such a computer program product is stored.

[0004] Fuel cell systems for mobile applications are known in the art. In a vehicle, the fuel cell system is typically configured to provide energy for a prime mover and / or a backup battery to propel the vehicle. Generic fuel cell systems comprise a fuel cell stack. The fuel cell stack typically comprises multiple fuel cells, each having two electrodes and a membrane arrangement between the two electrodes. In the fuel cell stack, fuel, particularly hydrogen, can react with oxygen during reverse electrolysis, generating electricity. The fuel can be supplied to the fuel cell stack from one or more pressurized vessels in the vehicle. The oxygen is typically taken from the ambient air.

[0005] Known fuel cell systems have a water separator in the anode subsystem to extract liquid water from process gas flowing from the anode into the water separator. The separated water can be routed out of the water separator via a purge path. The process gas can be recirculated back into the fuel cell and / or fuel cell stack via a recirculation path. A distinction must be made here between purging, also known as draining, and purging. Purging refers in particular to the removal of unwanted gases, contaminants, and / or liquids from the water separator and / or system components upstream of the water separator. Purging can be performed, for example, to remove air or other contaminants from process gas that is to be recirculated to the fuel cell.This is important to achieve the most efficient and trouble-free fuel cell reaction possible. Purging specifically involves the complete or partial removal of a liquid, especially water, from the water separator. Purging can be performed to perform maintenance, make repairs, and / or to safely shut down the fuel cell system and / or prepare it for a safe restart under freezing conditions.

[0006] Furthermore, purging and / or purging can be performed to adjust the fuel concentration in the fuel cell system, and in particular in the recirculation path. Purging and / or purging to adjust the desired fuel concentration is performed using methods and systems that utilize empirical controls, virtual models, and / or various sensors.

[0007] The object of the present invention is to provide improved methods and systems for adjusting the fuel concentration in a fuel cell system.

[0008] The above object is achieved by the patent claims. In particular, the above object is achieved by the method according to claim 1 and by the fuel cell system, the vehicle, the computer program product, and the computer-readable storage medium according to the independent claims. Further advantages of the disclosed technology emerge from the dependent claims, the description, and the figures. Features described in connection with the method also apply in connection with the fuel cell system, the vehicle, the computer program product, the storage medium, and vice versa, so that with regard to the disclosure of the individual aspects, reciprocal reference is and / or can always be made.

[0009] According to a first aspect of the present technology, a method for adjusting a fuel concentration in a fuel cell system is proposed. The fuel cell system comprises a fuel cell, a water separator, a fuel inlet path for conducting fuel to the fuel cell, a process gas outlet path for conducting process gas from the fuel cell and into the water separator, a purge path for conducting water and process gas from the water separator into the environment of the fuel cell system, and an outlet valve for controlling a mass flow through the purge path. The method comprises the following steps:

[0010] - Determination of an actual mass flow through the purge path,

[0011] - Determination of a reference mass flow,

[0012] - Carrying out a comparison between the actual mass flow and the reference mass flow,

[0013] - Setting an opening behavior of the exhaust valve based on the comparison.

[0014] In the context of this development, it was recognized that meaningful conclusions about the fuel concentration in the process gas can be easily drawn based on the actual mass flow in the purge path and / or through the outlet valve. If the process gas fed into the water separator has a high humidity, a high water vapor content, and / or a high nitrogen content, the process gas escapes from the water separator more slowly than if the humidity, water vapor content, and / or nitrogen content were lower. For example, nitrogen and water vapor escape more slowly through the outlet valve due to their higher molar mass compared to hydrogen.In other words, if the process gas fed into the water separator has a high fuel concentration, for example a high hydrogen concentration, the process gas can escape from the water separator through the purge path more quickly than with a lower fuel concentration. The actual mass flow rate can be determined using sensors, mathematical methods and / or a virtual model. For example, the actual mass flow rate can be determined using pressure sensors to determine an anode pressure. Furthermore, at least one virtual model can be used which determines or calculates the actual mass flow rate based on measured values. The target mass flow rate can be calculated, for example in real time, or read out from a computer-readable storage medium. The target mass flow rate can also be determined based on operating parameters and / or operating states of the fuel cell system.

[0015] In this case, determining can be understood as calculating and / or measuring a value and / or data. This means that, for example, to determine the actual mass flow and / or corresponding actual mass flow values, a value can first be measured, which can then be further developed into a final value using calculation methods and / or at least one virtual model. Determining can also be understood as reading data from a computer-readable storage medium.

[0016] The method can be carried out using a water separator to which a purge path is connected, in which there is only a single outlet valve, wherein the purging and emptying can be controlled by the one outlet valve. Controlling in the context of the present technology can be understood as open-loop and / or closed-loop control. The purge path can be understood here as a purge and / or emptying path. The water separator can be a conventional water separator and / or a section in the fuel cell system via which process water and process gas, in particular in the form of purge gas, can be separated from the fuel cell system. The water separator described here can therefore be understood as a section and / or a unit by means of which it can be prevented that process water is separated from the fuel cell system together with purge gas.

[0017] The opening behavior can be adjusted so that first all or as much of the water as possible is drained out of the water separator, followed by a defined amount of process gas. By draining the defined amount of process gas out of the water separator, the desired fuel concentration can be set. A mass balance can be created for this purpose as part of the process. Process gas flowing into the water separator can be described sufficiently well using virtual models. The mass balance can be based on the following statement: Process gas flowing out of the water separator through the outlet valve either creates a pressure loss or is replaced by process gas flowing into the water separator. During a purging process, i.e. while water is being discharged, no process gas is drained out of the water separator.When the nitrogen and / or water vapor concentration of the process gas is high, the process gas flows relatively slowly, meaning less process gas can flow through the outlet valve or out of the water separator. These relationships can ultimately be used to adjust the opening behavior of the outlet valve to achieve the desired fuel concentration in the recirculated process gas. The actual mass flow rate can be understood as the actual mass flow rate during emptying. The reference mass flow rate can be understood as at least one reference value with which an actual mass flow rate value is related for comparison purposes.Adjusting the opening behavior of the outlet valve based on the comparison can be understood as setting the outlet valve to a closed or open state depending on a difference between the actual mass flow and the reference mass flow, and / or adjusting a duty cycle of the outlet valve. Adjusting can be understood here as changing and / or maintaining a current state and / or behavior.

[0018] The outlet valve can be designed as a shut-off valve. Accordingly, the opening behavior of the outlet valve can only be adjusted and / or controlled between a fully open state and a fully closed state. In this case, a valve can be understood as a device that serves to control and / or regulate the flow of liquids, gases, and / or solid particles through a pipeline, a channel, or a cavity, for example, the purge path.

[0019] The process gas can be understood as the anode gas processed and / or chemically reacted in the fuel cell. The anode gas supplied to the fuel cell can comprise fuel, for example, hydrogen, and / or recirculated process gas, which can include the components described above. The mass flow can be understood as the amount of fluid, and in particular process gas, that flows out of the water separator via the purge path per unit of time.

[0020] According to a further embodiment of the present technology, it is possible for a duty cycle of the outlet valve to be reduced if it has been determined based on the comparison that the actual mass flow is greater than the reference mass flow. Alternatively or additionally, it is possible for a duty cycle of the outlet valve to be increased if it has been determined based on the comparison that the actual mass flow is less than the reference mass flow. In this way, the desired mass concentration can be set particularly easily. The duty cycle can be understood as a ratio or a percentage that describes the proportion of a time period during which a periodic function is active or switched on. The duty cycle can be used to specify what percentage of the time the valve is set to a certain state, in particular in an open state or a closed state.

[0021] Furthermore, it is possible to determine whether the outlet valve is open or closed, whereby the comparison is only performed when the outlet valve is open. It is therefore possible for current states regarding the mass flow to be considered only when the outlet valve is activated. In this way, the method can be implemented particularly efficiently. The comparison or a corresponding calculation operation can also be performed at a time when the outlet valve is closed. However, to adjust the opening behavior, preferably only those measurement data and / or states that were determined while the outlet valve was open are used.

[0022] With the method described here, it is also possible to determine the anode pressure of the fuel cell and to determine the reference mass flow rate based on the anode pressure. The reference mass flow rate can therefore be defined scaled with the anode pressure. This allows the desired fuel concentration to be set to the desired value particularly reliably. The anode pressure can be understood as a gas pressure in and / or at the anode of the fuel cell system, a gas pressure in the fuel inlet path upstream of the anode, and / or a gas pressure in the process gas outlet path downstream of the anode. This means that the anode pressure can be determined directly in the anode, upstream of the anode, and / or downstream of the anode. The anode pressure can be determined using sensors in and / or at the anode and / or using virtual models.

[0023] Furthermore, it is possible for a method according to the technology described here to determine the fuel consumption of the fuel cell and to adjust the opening behavior depending on the fuel consumption. This also makes it possible to set the desired fuel concentration particularly easily and reliably. The fuel consumption of the fuel cell can be understood as the amount of fuel supplied to the fuel cell that is consumed and / or chemically converted by the fuel cell within a certain period of time. The fuel consumption can be determined and / or measured in kilograms or liters per time, depending on the type of fuel. To determine the fuel consumption, the electricity generated by the fuel cell can be determined. The fuel consumption can then be determined based on the electricity generated.To determine the current, a current sensor can be positioned on and / or in the fuel cell.

[0024] Furthermore, with the technology described here, it is possible that a

[0025] Gas pressure behavior of the fuel cell is determined and the opening behavior depends on the

[0026] Gas pressure behavior is adjusted. Gas pressure behavior has proven to be a relatively simple and reliable parameter to consider when setting the desired fuel concentration. For example, if the fuel supply to the fuel cell is suddenly increased without changing fuel consumption, the pressure in the water separator can rise abruptly. This pressure jump can be considered as a disturbance variable or calculated accordingly, so that the opening behavior can be adjusted as desired even under these conditions. The gas pressure behavior can be determined or measured using a pressure sensor on and / or in the fuel inlet path.

[0027] A further aspect of the present technology relates to a fuel cell system for a vehicle, wherein the fuel cell system has a controller for carrying out a method as described above. The fuel cell system thus offers the same advantages as have been described in detail with reference to the method. The fuel cell system is preferably configured for mobile applications such as vehicles, in particular for providing energy for at least one drive machine such as an electric motor for propulsion of the vehicle. The fuel cell system can have at least one fuel cell, which can also be understood as a fuel cell stack with multiple fuel cells. The controller can have a suitable determination and / or computing unit, for example as part of at least one computer and / or at least one control unit.The controller may further comprise comparison units and / or correction units for performing comparisons, evaluations, and / or corrections. The water separator may be positioned directly downstream of the anode in the process gas outlet path. The water separator may be configured as part of an anode subsystem. The outlet valve may be positioned directly downstream of the water separator, on the water separator, or as an integral part of the water separator. The outlet valve may be configured as a combined outlet valve for purging and draining. The fuel cell system may be configured as a PEM fuel cell system. The fuel cell system may comprise a current sensor for detecting a current generated by the fuel cell and a pressure sensor for detecting an anode pressure.The fuel cell system may further comprise an ejector / injector and a current sensor for determining a current consumed by the ejector / injector.

[0028] Furthermore, one aspect of the proposed technology relates to a vehicle with a fuel cell system as described above and at least one electric motor for driving the vehicle, wherein the fuel cell system is configured to supply power to the at least one electric motor. The vehicle thus also offers the described advantages. The term "vehicle" can be understood to mean a motor vehicle such as a motor-driven two-wheeler, a passenger car, and a truck. The term "vehicle" can also be understood to mean a road vehicle, an aircraft, a watercraft, a rail vehicle, a spacecraft, and a robot. The term "vehicle" can also be understood to mean a purely electric vehicle and a hybrid electric vehicle, which, in addition to the at least one electric motor, has an internal combustion engine for driving the vehicle. The term "vehicle" can be understood to mean a so-called FCEV (Fuel Cell Electric Vehicle).

[0029] Furthermore, the technology disclosed here comprises a computer program product and a computer-readable, in particular non-volatile, storage medium on which the computer program product is stored. Thus, the computer program product and the computer-readable storage medium also provide the advantages described above. The computer program product can include instructions that, when the computer program product is executed by a computer, for example, the controller, cause the computer to carry out the proposed method in a vehicle as described above. The computer-readable storage medium can also be understood to mean the controller and / or a control unit, for example, a vehicle control unit, with the computer program product installed therein.

[0030] The computer program product may be implemented as computer-readable instruction code in any suitable programming language and / or machine language, such as JAVA, C++, C#, and / or Python. The computer program product may be stored on a computer-readable storage medium, such as a data disk, a removable drive, volatile or non-volatile memory, or a built-in memory / processor. The instruction code may program a computer and other programmable devices, such as a control unit, to perform the desired functions. Furthermore, the computer program product may be provided and / or be implemented on a network, such as the Internet, from which it can be downloaded by a user as needed.The computer program product can be implemented using software or one or more special electronic circuits, i.e., in hardware or in any hybrid form, i.e., using software components and hardware components. Further measures emerge from the following description of various exemplary embodiments, which are schematically illustrated in the figures. All features and / or advantages arising from the claims, the description, or the figures, including design details and spatial arrangements, can be significant both individually and in various combinations.

[0031] They show schematically:

[0032] Fig. 1 shows a fuel cell system according to an embodiment of the present technology,

[0033] Fig. 2 shows a water separator of the fuel cell system in a first operating state,

[0034] Fig. 3 the water separator of the fuel cell system in a second operating state,

[0035] Fig. 4 shows a computer-readable storage medium having a computer program product stored thereon according to an embodiment of the present technology,

[0036] Fig. 5 shows a vehicle with a fuel cell system according to an embodiment of the present technology,

[0037] Fig. 6 is a diagram for explaining a method according to an embodiment of the present technology, and

[0038] Fig. 7 is a diagram to further explain the process.

[0039] Elements with the same function and mode of operation are provided with the same reference symbols in the figures.

[0040] Fig. 1 shows a fuel cell system 10 according to a possible embodiment. The illustrated fuel cell system 10 comprises a fuel cell 11 with an anode 21 and a cathode 22. More specifically, the fuel cell 11 is configured as a fuel cell stack and has an anode region and a cathode region. The fuel cell system 10 comprises a water separator 12, a fuel inlet path 13 for conducting fuel to the fuel cell 11, and a process gas outlet path 14 for conducting process gas 16 from the fuel cell 11 and into the water separator 12. Furthermore, the fuel cell system 10 has a recirculation path 15 for conducting process gas 16 from the water separator 12 back into the fuel inlet path 13 and a purge path 17 for conducting water and process gas 16 from the water separator 12 into the environment of the fuel cell system 10.In the purge path 17, the fuel cell system 10 has an outlet valve 18 for controlling a mass flow through the purge path 17. Furthermore, the fuel cell system 10 has an ejector / injector 23 through which the fuel or anode gas is conveyed to the fuel cell 11 and through which the process gas 16 is conveyed via the process gas outlet path 14 and the recirculation path 15 into the fuel inlet path 13.

[0041] The illustrated fuel cell system 10 also has a sensor system with a pressure sensor 19 and two current sensors 26, 27. The pressure sensor 19 is positioned to determine a gas pressure in the fuel inlet path downstream of the ejector / injector 23 and upstream of the anode 21. A first current sensor 26 is positioned to determine the current generated by the fuel cell 11 or corresponding current values. A second current sensor 27 is positioned to determine the current consumed by the ejector / injector 23 or corresponding current values. The sensors 19, 26, 27 can in principle also be positioned at other locations. In addition, the fuel cell system 10 has a controller 20 for operating the fuel cell system 10. The controller 20 is in signal communication with the sensor system. The illustrated signal connection can be implemented wired or wirelessly.

[0042] Fig. 2 shows the water separator 12 in further detail. There is no water in the water separator 12 shown in Fig. 2, and the outlet valve 18 is open. In this operating state, the process gas 16 flowing in through the process gas outlet path 14 can flow out of the water separator 12 both through the recirculation path 15 and through the purge path 17. Fig. 3 shows a water separator 12 in which the outlet valve 18 is closed and water has accumulated in the water separator 12. In this case, the process gas 16 can only flow out of the water separator 12 through the recirculation path 15 and, in particular, not through the purge path 17.

[0043] Fig. 4 shows a computer-readable and non-volatile storage medium 60 on which a

[0044] Computer program product 50 is stored therein. The storage medium 60 is configured in the form of a flash drive. The computer program product 50 comprises instructions which, when executed by a computer, cause the computer to perform a method for adjusting a fuel concentration in the fuel cell system 10 in the illustrated vehicle 100. One possible method is explained below with reference to FIGS. 6 and 7.

[0045] Fig. 5 shows a vehicle 100 in the form of a passenger car. The vehicle 100 has a fuel cell system 10 as described above, comprising a fuel cell 11 and two electric motors 40 for driving the vehicle 100. The vehicle 100 also has a pressure vessel 70 containing fuel for supplying the fuel cell system 10. The fuel cell system 10 is configured to supply power to the electric motors 40 and / or a buffer battery (not shown). Furthermore, the vehicle 100 has a controller 20 in the form of a vehicle control unit. The controller 20 and the pressure vessel 70 can be considered part of the fuel cell system 10.

[0046] Fig. 6 shows a flow chart for explaining a method for adjusting a fuel concentration in the illustrated fuel cell system 10. In a first step S1, the electrical current consumed by the ejector / injector 23 is measured using a current sensor 27. In a second step S2, the current generated by the fuel cell 11 or by the fuel cell stack is measured using a current sensor 26. In a third step S3, the anode pressure is determined or measured using a pressure sensor. In a fourth step S4, a virtual model of the ejector / injector 23 is created based on the measured current, by means of which model a fuel flow to the fuel cell 11 is calculated. In a fifth step S5, the fuel consumption of the fuel cell 11 is calculated based on the measured current.In a sixth step S6, based on the fuel flow to the fuel cell 11 and based on the fuel consumption in the fuel cell 11, an actual mass flow to the water separator 12 and an actual mass flow through the purge path 17 are calculated. In a seventh step S7, a corresponding fuel consumption is calculated based on the changing anode pressure. Based on the fuel consumption, a reference mass flow is determined in an eighth step S8. This means that the reference mass flow is defined scaled to the anode pressure. In a ninth step S9, a comparison is made between the actual mass flow and the reference mass flow. If the comparison results in the actual mass flow being greater than the reference mass flow by a predefined or definable value, the duty cycle of the exhaust valve 18 is reduced in a tenth step S10.If the comparison results in the actual mass flow being smaller than the reference mass flow, the duty cycle of the outlet valve 18 is increased. Adjusting the duty cycle results in a corresponding opening behavior of the outlet valve 18. In the example shown, the comparison according to step S9 is only performed if it is detected that the outlet valve 18 is open.

[0047] Fig. 7 shows a diagram in which measured values ​​and calculated values ​​are represented according to the described method. In Fig. 7, the determined actual mass flow rate is represented as a mass flow rate graph 31. The opening behavior or duty cycle of the outlet valve 18 is represented as a duty cycle graph 32. The duty cycle graph 32 corresponds to a control signal for opening and closing the outlet valve 18. In Fig. 7, corresponding emptying times or opening times t1, t2, t3, t4 of the outlet valve 18 are represented. During these times, the outlet valve 18 is open. Furthermore, a lower reference value 33, a middle reference value 34 and an upper reference value 35 are represented in Fig. 7. The reference mass flow rate described above can be determined based on the reference values ​​33, 34, 35 and in particular based on the middle reference value 34 and the upper reference value 35.More precisely, in the example shown, a comparison is made between the actual mass flow and the reference values ​​33, 34, 35 to ensure that the determined actual mass flow remains as above the middle reference value 34 and below the upper reference value 35 as possible. Looking at the first opening time t1, it can be seen that the actual mass flow is relatively low. At this time, no emptying is probably taking place. During the second opening time t2 and the fourth opening time t4, the actual mass flow is relatively high and lies above the upper reference value, which indicates an emptying process. During the third opening time t3, the actual mass flow is low, but with values ​​sometimes above the upper reference value 35, it is sufficiently high that emptying can be concluded there too. Comparisons during the opening time t1 can lead to the duty cycle of the outlet valve 18 being increased.Comparisons during opening times t2 and t4 can result in a reduction in the duty cycle of exhaust valve 18. Comparisons during opening time t3 can result in the duty cycle of exhaust valve 18 remaining unchanged.

[0048] The technology disclosed here allows for further design principles in addition to the embodiments shown. This means that the technology should not be considered limited to the embodiments explained with reference to the figures.

[0049] Fuel cell system Fuel cell Water separator Fuel inlet path Process gas outlet path Recirculation path

[0050] Process gas purge path outlet valve pressure sensor controller anode cathode

[0051] Ejector / Injector pressure sensor pressure sensor

[0052] Mass flow graph Duty cycle graph Lower reference value Middle reference value Upper reference value Electric motor

[0053] Computer program product storage medium pressure vessel

[0054] vehicle

Claims

Patent claims 1. A method for adjusting a fuel concentration in a fuel cell system (10), wherein the fuel cell system (10) comprises a fuel cell (11), a water separator (12), a fuel inlet path (13) for conducting fuel to the fuel cell (11), a process gas outlet path (14) for conducting process gas (16) from the fuel cell (11) and into the water separator (12), a purge path (17) for conducting water and process gas (16) from the water separator (12) into the environment of the fuel cell system (10), and an outlet valve (18) for controlling a mass flow through the purge path (17), the method comprising: - Determining an actual mass flow through the purge path (17), - Determination of a reference mass flow, - Performing a comparison between the actual mass flow and the reference mass flow, - Setting an opening behavior of the exhaust valve (18) based on the comparison.

2. The method according to claim 1, wherein a duty cycle of the outlet valve (18) is reduced if it has been determined based on the comparison that the actual mass flow is greater than the reference mass flow and / or wherein a duty cycle of the outlet valve (18) is increased if it has been determined based on the comparison that the actual mass flow is smaller than the reference mass flow.

3. Method according to one of the preceding claims, wherein it is determined whether the outlet valve (18) is open or closed and wherein the comparison is only carried out when the outlet valve (18) is open.

4. Method according to one of the preceding claims, wherein an anode pressure of the fuel cell (11) is determined and the reference mass flow is determined based on the anode pressure.

5. Method according to one of the preceding claims, wherein a fuel consumption of the fuel cell (11) is determined and the opening behavior is adjusted depending on the fuel consumption.

6. Method according to one of the preceding claims, wherein a gas pressure behavior of the fuel cell (11) is determined and the opening behavior is adjusted depending on the gas pressure behavior.

7. A fuel cell system (10) comprising a controller (20), wherein the controller (20) is configured to carry out a method according to any one of the preceding claims.

8. A vehicle (100) comprising a fuel cell system (10) according to claim 7 and at least one electric motor (40) for driving the vehicle (100), wherein the fuel cell system (10) is configured to supply power to the at least one electric motor (40).

9. A computer program product (50) comprising instructions which, when the computer program product (50) is executed by a computer, cause the computer to carry out the method according to one of claims 1 to 6 in a vehicle (100) according to claim 8.

10. A computer-readable storage medium (60) having stored thereon a computer program product (50) according to claim 9.

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