Method for testing at least one sensor in an anode path of a fuel cell system - Patents.com

Abstract

A method for testing at least two sensors in an anode path (4) of a fuel cell system (1), comprising the steps of shutting down the fuel cell system (1), closing a shut-off valve (32) and a purge valve (41), opening an internal valve (34), detecting pressure values ​​of at least two sensors (50, 51, 52, 53, 54) in the anode path, and testing whether the pressure values ​​of the at least two sensors (50, 51, 52, 53, 54) differ.

Description

[Technical Field]

[0001] The present invention starts from a method for testing at least one sensor in the anode path of a fuel cell system, and a fuel cell system having a measurement assembly therefor. [Background technology]

[0002] Hydrogen-based fuel cell systems are considered a mobility concept of the future because they emit only water as an exhaust gas, enabling quick refueling times. In this case, fuel cell systems require air and hydrogen for the chemical reaction within the cells. The fuel cells arranged in a fuel cell system are connected to each other to provide the required amount of energy, forming a so-called fuel cell stack. In this case, the cells' waste heat is dissipated using a cooling circuit and vented to the environment. The hydrogen required for the operation of the fuel cell system is typically supplied to the system from a high-pressure tank. In this case, the metering is performed in excess of the stoichiometric amount for reasons of efficiency and component protection. To avoid wasting excess hydrogen, the unused hydrogen portion is recirculated within the anode path. In this case, the anode gas is usually returned from the anode gas return line via a water separator, recirculation pump, jet pump, or similar, and then resupplied to the anode together with fresh water. During fuel cell operation, nitrogen continuously diffuses from the cathode side to the anode side and accumulates there. Therefore, to provide sufficient hydrogen for recirculation, the nitrogen must be purged at regular intervals via a purge valve. Otherwise, if the pumping capacity of the recirculation pump is constant, the amount of hydrogen returned will continually decrease.

[0003] To ensure accurate hydrogen metering, high accuracy of the sensor in the anode path is required. Summary of the Invention

[0004] If the pressure values ​​of at least two sensors in the anode path of a fuel cell system are compared with each other to check whether there are any differences in order to check the function of at least two sensors, this is advantageous as it is a simple and inexpensive method for checking the function of the sensors.

[0005] The dependent claims describe advantageous embodiments and developments of the fuel cell system according to the invention.

[0006] It is advantageous to reduce the pressure in the anode path to ambient pressure or to a pressure between the supply pressure and ambient pressure, since in this pressure range the comparison of the pressure values ​​of the individual sensors can be carried out without the influence of external disturbances.

[0007] Another advantage can be achieved if, when the fuel cell system is started, the internal valves, particularly the HGI valve, are closed, the shutoff valve is opened, and the pressure rise at a first sensor in the connecting line between the shutoff valve and the internal valve within a predetermined time interval dt is compared with an expected pressure profile, since a defective sensor can be identified even when only two sensors are compared.

[0008] Alternatively, when the fuel cell system is started, the internal valves, particularly the HGI valves, may be closed and the shut-off valves may be opened, and the pressure value measured at a first sensor in the connecting line between the shut-off valves and the internal valves according to a predetermined time interval dt is compared with the expected pressure value.

[0009] It is advantageous to select the time interval dt so that the pressure in the connecting lines at the end of the time interval dt does not exceed a maximum pressure value of 15-20 bar, since then the pressure only needs to be adapted to a small extent for the next operation of the fuel cell system. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a fuel cell system according to a first embodiment of the present invention; [Figure 2] 1 is a flow chart of the individual steps of the method according to the invention; DETAILED DESCRIPTION OF THE INVENTION

[0011] FIG. 1 shows a schematic diagram of a fuel cell system 1 according to a first embodiment of the present invention.

[0012] In this case, the fuel cell system 1 includes an anode pathway 4 connected to the anode 12 of the fuel cell stack 20. The anode pathway 4 includes an anode gas supply line 6 and an anode gas return line 7. The anode gas supply line 6 connects a hydrogen tank 28 to the anode 12 of the fuel cell stack 20.

[0013] During operation of the fuel cell system 1, hydrogen is supplied to the anode gas supply line 6 by a hydrogen tank 28. A shut-off valve 32 and an internal valve 34, in particular an HGI valve 34, are disposed within the anode gas supply line 6. The shut-off valve 32 is open during operation of the fuel cell system 1. When the fuel cell system 1 is shut down, the shut-off valve 32 is closed, thereby preventing hydrogen from flowing from the hydrogen tank 28 to the anode 12.

[0014] The internal valve 34 is configured as an HGI valve 34 and is capable of metering the amount of hydrogen required to the anode 12 depending on the respective operating state of the fuel cell stack 20 .

[0015] A connecting line 8 is arranged between the shut-off valve 32 and the internal valve 34. The connecting line 8 is provided with a first sensor 50 by means of which the pressure in the connecting line 8 can be determined.

[0016] The second sensor 51 is disposed in the anode gas supply line 6 in a line portion between the internal valve 34 and the anode 12 .

[0017] Hydrogen is often stored under high pressure in a hydrogen tank 28. To reduce the pressure, a pressure regulator 30 may be provided between the hydrogen tank 28 and a shutoff valve 32, which reduces the pressure before the hydrogen flows to an internal valve 34 or to the anode 12. The pressure at the inlet of the shutoff valve 32, which corresponds to the tank pressure or reduced by the pressure regulator 30, is called the supply pressure.

[0018] The fuel cell system 1 further includes a cathode gas supply line 15 that supplies air to the cathode 16 of the fuel cell stack 20 , and a cathode gas discharge line 17 that discharges used air and exhaust gas from the fuel cell stack 20 .

[0019] During operation of the fuel cell system 1, hydrogen is released in the anode path 4 to the anode 12 via the hydrogen tank 28, the shut-off valve 32, and the internal valve 34. Because the hydrogen at the anode 12 is supplied in stoichiometric excess for reasons of efficiency and component protection, unused hydrogen is routed via the anode gas return line 7 and reintroduced into the anode gas supply line 6 at the hydrogen return point 22.

[0020] A recirculation pump 42 may be located in the anode gas return line 7. Additionally, other sensors 52, 53, 54 are located in the anode gas return line 7.

[0021] During the fuel cell reaction, nitrogen diffuses from the cathode 16 to the anode 12 and accumulates at an increasing rate in the anode passage 4 via the anode gas return line 7, so the nitrogen accumulated in the anode passage 4 must be removed from the fuel cell system 1 from time to time.

[0022] This can be done by a purge valve 41 arranged in the anode gas return line 7. A water separator, a water reservoir and a drain valve may further be arranged in the anode gas return line 7 to conduct excess water from the anode 12 or the anode passage 4, but these are not essential to the invention and are not explicitly shown in the drawings.

[0023] The fuel cell system 1 comprises a measuring assembly for testing at least two sensors 50, 51, 52, 53, 54. For detecting measured values, in particular pressure values, and for evaluating them in the method according to the invention, and thus for detecting at least two Sensor To test the sensors 50, 51, 52, 53, 54, the measurement assembly includes a control unit 11 that is connected by wire or wirelessly to at least two sensors 50, 51, 52, 53, 54. For better illustration, only one dashed line indicating the wire or wireless connection between the first sensor 50 and the control unit 11 is shown in Figure 1.

[0024] The control unit 11 is also connected to other components of the fuel cell system 1. The control unit 11 may also be connected to the shut-off valves 32 or internal valves 34, thereby controlling them and detecting when the shut-off valves 32 and / or internal valves 34 are opened or closed, and including this in the calculation of pressure profiles or pressure values.

[0025] The control unit 11 may also consist of several control devices or control units assigned to the individual components of the fuel cell system 1 .

[0026] 2 shows a flow chart of the individual steps of a method according to the invention for checking the function of at least two sensors in the anode path 4. In method step 100, the fuel cell system 1 is shut down. The shut down can also include a standby mode, but there must be an operating mode in which no hydrogen is supplied from the hydrogen tank 28 to the anode 12 of the fuel cell stack 20. This is done by closing the shut-off valve 32.

[0027] When the fuel cell system 1 is shut down, the anode path 4 The pressure is reduced to a pressure corresponding to ambient pressure or a pressure between the supply pressure and ambient pressure.

[0028] In one embodiment of the invention, to reduce the pressure in the anode path 4, the first shut-off valve 32 at the inlet of the connecting line 8 is closed, and the internal valve 34 and the purge valve 41 are opened until the required pressure level is reached.

[0029] In method step 110, the purge valve 41 is closed. The shut-off valve 32 is already closed due to the shutdown of the fuel cell system 1, so that the anode path 4 is closed to the environment. If other valves form connections to the environment and to lines outside the anode path 4, these must also be closed.

[0030] In method step 120, the internal valve 34 is opened, thereby preventing closed valve gas exchange within the anode path 4. If there are other valves or components within the anode path 4 that can prevent gas exchange between the individual line segments, these other valves or components are also opened.

[0031] In method step 130, the pressure values ​​of at least two sensors 50, 51, 52, 53, 54 in the anode path 4 are detected, and in method step 140 it is checked whether the pressure values ​​of the at least two sensors 50, 51, 52, 53, 54 differ.

[0032] If the anode path 4 is a closed system with respect to the environment, and the internal valve 34 and all other valves or components are open, so that at least two sensors 50, 51, 52, 53, 54 can fully function, their pressure values ​​should be equal. If there is a difference between the pressure values, the functionality of at least one sensor 50, 51, 52, 53, 54 is limited, and a corresponding notification or notification is generated in method step 141. If there are more than two sensors 50, 51, 52, 53, 54 in the anode path 4, the defective sensor 50, 51, 52, 53, 54 can be easily identified.

[0033] If there is no difference between the pressure values, the functionality of at least two sensors 50, 51, 52, 53, 54 is good and a corresponding notification or indication is given in method step 142.

[0034] In optional method step 150, an additional check of the first sensor 50 in the connecting line 8 can be performed. In this case, when the fuel cell system 1 is started, the internal valves 34, in particular the HGI valve 34, are closed and the shut-off valve 32 is opened, and the pressure rise at the first sensor 50 in the connecting line 8 between the shut-off valve 32 and the HGI valve 34 within a predetermined time interval dt is compared with an expected pressure profile. If the expected pressure rise profile matches the pressure rise measured at the first sensor 50, the function of the sensor 50 is correct; otherwise, it is defective.

[0035] In a further optional method step 160, an additional check of the first sensor 50 in the connecting line 8 may be performed. In this case, when the fuel cell system is started, the internal valves 34, in particular the HGI valve 34, are closed and the shut-off valve 32 is opened, and the pressure value measured by the first sensor 50 in the connecting line 8 between the shut-off valve 32 and the HGI valve 34 according to a predetermined time interval dt is compared with an expected pressure value. If the expected pressure value matches the pressure value measured by the first sensor 50 according to the time interval dt, the function of the sensor 50 is correct; otherwise, it is defective.

[0036] In this case, the time interval dt can be selected such that the pressure in the connecting line 8 at the end of the time interval dt does not exceed a maximum pressure value of 15-20 bar. [Explanation of symbols]

[0037] 1. Fuel cell system 4 Anode Path 6 Anode gas supply line 7 Anode gas return line 8 Connection Lines 11 Control Unit 12 anodes 15 Cathode gas supply line 16 cathode 17 Cathode gas outlet line 20 Fuel Cell Stack 22 Hydrogen return point 28 Hydrogen Tank 30 Pressure Regulating Valve 32 Shut-off valve 34 Internal valve, HGI valve 41 Purge valve 50 First Sensor 51 Second Sensor 52, 53, 54 Other sensors 100 Method Steps 110 Method Steps 120 method steps 130 method steps 140 method steps 150 method steps 160 method steps

Claims

1. A method for testing the functionality of at least two sensors in an anode path (4) of a fuel cell system (1), comprising: 1.) shutting down the fuel cell system (1); 2.) Closing the purge valve (41); 3.) Opening the internal valve (34); 4.) Detecting pressure values ​​of at least two sensors (50, 51, 52, 53, 54) in the anode path; 5.) checking whether the pressure values ​​of the at least two sensors (50, 51, 52, 53, 54) are different, The anode pathway (4) comprises an anode gas supply line (6) and an anode gas return line (7); at least one sensor of the at least two sensors (50, 51, 52, 53, 54) is disposed in a line portion of the anode gas return line (7) or the anode gas supply line (6) between the internal valve (34) and the anode (12); Hydrogen not used in the fuel cell stack (20) arranged in the fuel cell system (1) is introduced into the anode gas supply line (6) at a hydrogen return point (22) via the anode gas return line (7); The hydrogen return point (22) is provided in the internal valve (34).

2. 2. The method according to claim 1, characterized in that when the fuel cell system (1) is shut down, the pressure in the anode path (4) is reduced to ambient pressure or to a pressure between the supply pressure and ambient pressure.

3. 3. The method according to claim 2, characterized in that the shut-off valve (32) at the inlet of the connecting line (8) is closed and the internal valve (34) and the purge valve (41) are opened to reduce the pressure in the anode path (4).

4. 4. The method of claim 3, characterized in that when the fuel cell system is started, the internal valve (34) is closed, the shut-off valve (32) is opened, and the pressure increase at a first sensor in the connecting line (8) between the shut-off valve (32) and the internal valve (34) within a predetermined time interval dt is compared with an expected pressure profile.

5. 4. The method according to claim 3, characterized in that when the fuel cell system is started, the internal valve (34) is closed, the shut-off valve (32) is opened, and a pressure value measured by a first sensor (50) in a connecting line (8) between the shut-off valve (32) and the internal valve (34) according to a predetermined time interval dt is compared with an expected pressure value.

6. 6. The method according to claim 4 or 5, characterized in that the internal valve (34) is a valve for supplying hydrogen to the anode (12).

7. 7. The method according to claim 4, wherein the time interval dt is selected such that the pressure in the connecting line (8) at the end of the time interval dt does not exceed a maximum pressure value of 15 to 20 bar.

8. 10. A fuel cell system (1) having a measurement assembly for testing at least two sensors (50, 51, 52, 53, 54) and for carrying out the method according to any one of claims 1 to 7, the fuel cell system (1) having an anode path (4), an anode (12) and an anode gas return line (14), and a connecting line (8) arranged between a first valve (32) and an internal valve (34) in the anode path (4), a first sensor (50) for detecting a measurement to determine the pressure at a predetermined position in the connection line (8) of the anode path (4); - a control unit (11) for checking at least one sensor in the anode path (4) of the fuel cell system (1) based on measurements detected by the first sensor (50).

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