Method for testing the tightness of a fuel cell system, diagnostic tester

Abstract

The invention relates to a method for checking the tightness of a fuel cell system (100), wherein the fuel cell system (100) has a fuel path (20) and an anode circuit (50) for supplying an anode (103) of a fuel cell stack (101) of the fuel cell system (100), an air path (10) for supplying air to a cathode (102) of the fuel cell stack (101), and an exhaust air path (12) for discharging air from the cathode (102). The method comprises the following steps: closing an inlet valve (15) in the air path (10) and an outlet valve (17) in the exhaust air path (12) such that a closed region (19) is formed between the inlet valve (15) and the outlet valve (17); setting an overpressure in the anode circuit (50) by supplying a test gas; closing a shut-off valve (24) and / or a metering valve (22) in the fuel path (20); measuring an anode pressure (PA) in the anode circuit (50) and a cathode pressure (PC) after a first waiting time (TW); determining an anode pressure difference (dPA) and a cathode pressure difference (dPC); and determining a further pressure difference (dPS), wherein the further pressure difference represents a measure of a leak from the fuel cell system (100) into the environment.

Description

[0001] R.412495

[0002] - 1 -

[0003] Description

[0004] title

[0005] Method for checking the tightness of a fuel cell system, diagnostic tester

[0006] The invention relates to a method and a diagnostic tester for checking the tightness of a fuel cell system.

[0007] State of the art

[0008] After a suspected fault and / or after a repair to a fuel cell system, the fuel cell system must be checked for leaks.

[0009] To ensure the safety and proper operation of the fuel cell system, the fuel cell system must be reliably checked for leaks to ensure that there are no leaks.

[0010] To check the tightness, the anode circuit is filled with a test gas, such as gaseous nitrogen or a forming gas, and pressurized. Depending on the test gas, the entire anode subsystem is then scanned for leaks using a gas sniffer or a leak detection spray. With this conventional method, it can take a very long time to detect a leak or to fully test the tightness. Suspected areas can be difficult to access, and especially in workshops, there is a risk of overlooking small leaks.

[0011] It is therefore an object of the invention to provide a method and a diagnostic tester that make it possible to simplify the detection of leaks in a fuel cell system and to increase the reliability of checking the system for leaks. R.412495

[0012] - 2 -

[0013] Disclosure of the invention:

[0014] The inventive method for operating a fuel cell system with the features according to the independent claim has the advantage that the method enables a precise and reliable leak test by separately measuring and evaluating the pressures on the anode and cathode sides. This leads to an accurate determination of leaks and improves the safety and efficiency of the fuel cell system.

[0015] Furthermore, the use of a gas detector or leak detection spray is unnecessary. Leak detection is much faster and more precise with the inventive method than with conventional methods. Even leaks in hard-to-reach locations can be reliably detected using the inventive method.

[0016] The dependent claims specify advantageous embodiments and further developments of the method according to the invention.

[0017] It is advantageous to determine the differential pressure (dPs) from the differential anode pressure (dPA) and the differential cathode pressure (dPc), since both the pressure in the anode circuit and the pressure in the closed circuit can be reliably determined by pressure sensors, in particular the anode pressure sensor and the cathode pressure sensor, which are already installed in the fuel cell system. Consequently, the differential anode pressure (dPA) and the differential cathode pressure (dPc) are based on reliable and easily accessible measurements. No additional pressure sensors need to be installed in the fuel cell system to determine the differential pressure.

[0018] It is advantageous for an error message to be issued if the differential pressure (dPs) exceeds a predefined limit. Automatic error message generation upon exceeding a limit ensures immediate notification of potential leaks. This enables rapid response and maintenance, thereby increasing the operational safety and reliability of the fuel cell system. R.412495

[0019] - 3 -

[0020] Adjusting the pressure within the fuel cell system, particularly the anode pressure (PA) and cathode pressure (PC), to ambient pressure before starting the procedure is advantageous because it ensures that measurements are taken under standardized conditions. Furthermore, adjusting the anode pressure (PA) and cathode pressure (PC) to ambient pressure is easily accomplished by opening valves within the fuel cell system.

[0021] It is advantageous to remove the operating gas from the anode circuit by opening a purge and / or drain valve, as this ensures that the operating gas does not react with air at the fuel cell stack and thus lead to a distortion of the measurement results.

[0022] It is advantageous to purge the anode circuit with the test gas after opening the purge and / or drain valve, as this ensures that the anode circuit is completely filled with the test gas. This improves the accuracy of the pressure measurements and the reliability of the leak test.

[0023] It is advantageous if the further pressure difference dPs can be calculated using the formula dP. s = ((Vcx dP c ) + (V A x dP A )) / -V sThis method is used because it allows for a mathematically sound and precise determination of the leakage. This increases the accuracy and reliability of the leak test and facilitates the interpretation of the results.

[0024] Connecting an external test gas reservoir to the fuel line for supplying the test gas is advantageous because it allows for a controlled and constant supply of the test gas. This also ensures that the test pressure is set precisely.

[0025] The invention also includes a diagnostic tester for checking the leak tightness of a fuel cell system. The diagnostic tester is designed and configured to perform a method according to the invention for checking the leak tightness of a fuel cell system, as previously described. R.412495

[0026] - 4 - to check the tightness of the fuel cell system from the environment. This reduces manual effort and the risk of operator error, thereby increasing the efficiency and reliability of the test.

[0027] It is advantageous for the diagnostic tester to connect to at least one control unit of the fuel cell system to actuate the anode shut-off valve and / or the metering valve and / or an anode pressure sensor and / or a cathode pressure sensor. The diagnostic tester's ability to connect to the fuel cell system's control units enables seamless integration and control of the valves and sensors. This simplifies leak testing and improves the accuracy and efficiency of the entire testing process.

[0028] The inventive method and diagnostic tester make it possible to detect leaks from the fuel cell system into the environment conveniently, quickly and with high reliability, without triggering too many false alarms.

[0029] This eliminates the need for lengthy and costly leak detection in the fuel cell system. Workshops can document and prove that they have performed their work on the fuel cell system correctly. Furthermore, automated execution of the procedure can increase reproducibility and reduce the risk of errors in the workshop.

[0030] Brief description of the characters

[0031] Figure 1 shows a schematic representation of a diagnostic device and a fuel cell system according to the invention.

[0032] Character description

[0033] The fuel cell system 100 shown in Figure 1 has a

[0034] Anode circuit 50, which supplies an anode 103 of a

[0035] Fuel cell stack 101 is supplied with hydrogen. The hydrogen is supplied to the R.412495

[0036] - 5 -

[0037] Fuel cells of the fuel cell stack 101 together with oxygen, which is supplied to a cathode 102 of the fuel cell stack 101, convert the energy into electrical energy, heat and water.

[0038] The hydrogen is stored in a tank 21 and metered into the anode circuit 50 via a fuel path 20 using a metering valve 22. A shut-off valve 24 is arranged in the fuel path 20. The shut-off valve 24 is located between the tank 21 and the metering valve 22.

[0039] The anode circuit 50 supplies the anode 103 of the fuel cell stack 101 not only with fresh fuel as anode gas, but also with recirculated anode gas. A jet pump 51 is integrated into the anode circuit 50 for passive recirculation. Furthermore, a recirculation pump 52 can be provided, which can be used to actively recirculate the anode gas.

[0040] Due to the permeability of the membrane of the fuel cell stack 101, nitrogen also accumulates in the anode circuit 50 during operation. As a result, the proportion of hydrogen in the anode circuit 50 decreases, while the proportion of nitrogen increases.

[0041] By opening a purge valve 41, the anode circuit 50 can be purged via a purge line 40 to transport nitrogen and / or fuel out of the anode circuit 50.

[0042] Since the anode gas escaping from the fuel cell stack 101 may contain liquid water, it can be fed to a water separator 55. Once this is full, a drain valve 57 can be opened to empty it.

[0043] Depending on the system design, the drain and purge process can also be carried out using only a combined drain / purge valve.

[0044] An anode pressure sensor 53 is provided in the anode circuit 50, which makes it possible to measure the pressure in the anode circuit 50.

[0045] The air supplied to the cathode 102 of the fuel cell stack 101 is drawn from the environment via an inlet 16 and fed to an air compressor 11 via an air path 10. The air compressor 11 compresses the supplied air, as the electrochemical process in the fuel cells requires a certain amount of air.

[0046] - 6 -

[0047] Air mass flow and a certain pressure level are required. The air compressor 11 can be arranged downstream of an air filter in the air path 10. An inlet valve 15 is arranged in the air path 10. The inlet valve 15 is preferably arranged between the air compressor 11 and the cathode 102.

[0048] Exiting air is discharged from the fuel cell stack 101 via an exhaust path 12. An exhaust valve 17 is arranged in the exhaust path 12. Closing the inlet valve 15 and the exhaust valve 17 creates a closed chamber 19 with a volume Vc. The volume Vc comprises the piping system between the inlet valve 15 and the exhaust valve 17, in particular a portion of the air duct 10, the piping system within the cathode 102, and a portion of the exhaust path 12.

[0049] A cathode pressure sensor 14 is provided in the enclosed area 19, enabling the pressure within the enclosed area 19 to be measured. The cathode pressure sensor 14 can be located in the air duct 10 or in the exhaust gas path 12. The cathode pressure sensor 14 can be controlled and read by a control unit of the fuel cell system 100.

[0050] The inventive method for checking the tightness of a fuel cell system 101 comprises several steps. First, the inlet valve 15 in the air path 10 and the outlet valve 17 in the exhaust air path 12 are closed, so that a closed area 19 is formed between the inlet valve 15 and the outlet valve 17.

[0051] Subsequently, an overpressure is set in the anode circuit 50 by supplying a test gas. Then, the shut-off valve 24 and / or the metering valve 30 in the fuel path 20 are closed.

[0052] After a predetermined waiting time Tw, the anode pressure PA in anode circuit 50 and the cathode pressure Pc are measured. From these measurements, an anode pressure difference dPA and a cathode pressure difference dPc are determined.

[0053] The anode pressure difference dPA is derived from the pressure difference between the anode pressure PA measured after the waiting time Tw and the R.412495

[0054] - 7 - originally set overpressure determined. The anode pressure PA in the anode circuit 50 is determined by the anode pressure sensor 53.

[0055] The cathode pressure difference dPc is determined from the pressure difference between the cathode pressure PC, measured after the waiting time Tw, and the ambient pressure. The cathode pressure Pc in the closed area 19 is determined by the cathode pressure sensor 14.

[0056] To establish ambient pressure in the closed area 19, the inlet valve 15 in the air path 10 and the outlet valve 17 in the exhaust path 12 are opened before the start of the measurement.

[0057] A further pressure difference dPs is determined from the anode pressure difference dPA and the cathode pressure difference dPc. This further pressure difference dPs represents a measure of leakage from the fuel cell system 100 into the environment.

[0058] The further pressure difference dPs is calculated using the formula dP s =(Vc*dPc)+(VA*dPA)-V s dP s =-V s (VC*dPc)+(VA*dP A ) determined, where Ve is the volume of the closed region 19, VA is the volume of the anode circuit 50, Vs is the combined volume of the closed region 10 and the volume of the anode circuit 50, and dPs is the pressure difference between the closed region 19 and the anode circuit 50 relative to the surroundings.

[0059] Since the differential pressure dPs is a measure of leakage from the fuel cell system 100 into the environment, an error message is issued if the differential pressure dPs exceeds a predefined limit. In this case, during normal operation of the fuel cell system 100, the fuel leakage into the environment would be so high that the safety requirements could not be met. R.412495

[0060] - 8 -

[0061] Before starting the test procedure, the pressure within the fuel cell system 100, in particular the anode pressure PA and the cathode pressure Pc, can be adjusted to ambient pressure.

[0062] To adjust the anode pressure PA to ambient pressure, any operating gas, in particular hydrogen, still present in the anode circuit 50 or in the fuel line 20, is removed from the fuel cell system 100 by opening the purge valve 41 and / or the drain valve 57. To ensure that all components of the operating gas have been removed, the anode circuit 50 can additionally be purged with the test gas or another suitable gas after opening the purge valve 41 and / or drain valve 57.

[0063] To supply the test gas, an external test gas reservoir 25 can be connected to the fuel line 20.

[0064] Furthermore, a diagnostic tester 70 is provided and configured to perform the procedure described above for checking the tightness of the fuel cell system 100. The diagnostic tester 70 can establish a connection with at least one control unit of the fuel cell system 100 to control the anode shut-off valve 28 and / or the metering valve 30 and / or a pressure sensor in the anode circuit 50 or in the closed section. The connection can be wired via an OBD interface or wireless.

[0065] The diagnostic tester 70 can issue an error message if a leak to the environment is detected in the fuel cell system 101. The error message can be displayed, for example, on a display device of the diagnostic tester 70.

[0066] A successfully completed test run, in which no indication of a leak was found, can also be displayed on the display device.

[0067] A successfully completed test run can also be saved to a storage device, e.g., for logging purposes. The storage device can be located inside or outside the diagnostic tester 70 R.412495.

[0068] - 9 - . The storage device may be located, for example, in a vehicle or in a virtual cloud.

[0069] To test the leak tightness of the fuel cell system 100, a suitable test gas, such as nitrogen gas or forming gas, can be used. A readily detectable forming gas can also be used as a test gas, making it easy to locate any leaks by detecting the forming gas escaping from the fuel cell system 100.

Claims

R.413843 - 10 - Patent claims 1. Method for checking the tightness of a fuel cell system (100), wherein the fuel cell system (100) has a fuel path (20) and an anode circuit (50) for supplying an anode (103) of a fuel cell stack (101) of the fuel cell system (100) and an air path (10) for supplying air to a cathode (102) of the fuel cell stack (101) and an exhaust air path (12) for removing air from the cathode (102), the method comprising: Closing an inlet valve (15) in the air path (10) and an outlet valve (17) in the exhaust path (12), so that a closed area (19) is formed between the inlet valve (15) and the outlet valve (17); Setting an overpressure in the anode circuit (50) by supplying a test gas; Closing a shut-off valve (24) and / or a metering valve (22) in the fuel path (20); Measuring an anode pressure (PA) in the anode circuit (50) and a cathode pressure (Pc) after an initial waiting period (Tw); Determining an anode pressure difference (dPA) and a cathode pressure difference (dPc); and Determining a further pressure difference (dPs) where the further pressure difference is a measure of leakage from the fuel cell system (100) into the environment.

2. Method according to claim 1, wherein the further pressure difference (dPs) is determined from the anode pressure difference (dPA) and the cathode pressure difference (dPc). R.413843 - 11 - 3. Method according to claim 1, wherein an error message is issued if the further pressure difference (dPs) exceeds a predetermined limit.

4. Method according to one of the preceding claims, characterized in that the pressure within the fuel cell system (100), in particular the anode pressure (PA) and the cathode pressure (Pc), is set to ambient pressure before the start of the method.

5. Method according to claim 4, characterized in that an operating gas is removed from the anode circuit (50) by opening a purge and / or drain valve.

6. Method according to claim 5, characterized in that after opening the purge and / or drain valve the anode circuit (50) is purged with the test gas.

7. Method according to one of the preceding claims, characterized in that the further pressure difference dPs is determined via the formula dP s = ((Vc x dP c ) + (V A x dP A )) / -V sis determined where Vc is the volume of the closed area, VA is the volume of the anode circuit, Vs is the volume of the closed area + anode circuit, and dPs is the pressure difference between the closed area + anode circuit.

8. Method according to one of the preceding claims, characterized in that an external test gas reservoir (25) is connected to the fuel line (20) for supplying the test gas.

9. Diagnostic tester (70) for checking the tightness of a fuel cell system (100), wherein the diagnostic tester (70) is provided and configured to perform a method according to one of the preceding claims to check the tightness of the fuel cell system (100).

10. Diagnostic tester (70) according to claim 9, characterized in that the diagnostic tester (70) is equipped with at least one control unit of the R.413843 - 12 - fuel cell system (100) establishes a connection to control the anode shut-off valve (28) and / or the metering valve (22) and / or an anode pressure sensor (53) and / or a cathode pressure sensor (14).

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