Hydrogen leak detection method for fuel cell system and fuel cell system

Abstract

The invention discloses a hydrogen leakage detection method for a fuel cell system. The fuel cell system comprises a housing; the gas inlet pipe and the gas outlet pipe are communicated with the shell, and a hydrogen concentration sensor is arranged at the outlet end of the gas outlet pipe; and a bypass pipe located between the intake pipe and the exhaust pipe, a bypass valve being provided in the bypass pipe, the hydrogen leakage detection method including: placing the bypass valve in a fully open state, supplying air to the intake pipe, and discharging the air from the exhaust pipe through the bypass pipe; adjusting the opening degree of the bypass valve, so that a first part of the air enters the shell at a first volume flow rate and enters the exhaust pipe from the shell, and a second part of the air enters the exhaust pipe through the bypass pipe at a second volume flow rate; obtaining a diluted hydrogen concentration measured by the hydrogen concentration sensor while obtaining a dilution ratio, the dilution ratio being expressed as a ratio of a sum of the first volume flow rate and the second volume flow rate to the first volume flow rate; and calculating a raw hydrogen concentration within the enclosure based on the diluted hydrogen concentration and the dilution ratio.

Description

Technical Field

[0001] This application relates to the field of fuel cell technology, and in particular to a method for detecting hydrogen leaks in a fuel cell system and a fuel cell system. Background Technology

[0002] With the development of clean energy technologies, fuel cell systems have been widely used as power sources in many industries (e.g., electric vehicles). In a fuel cell system, hydrogen is supplied as the fuel gas to the anode side of the fuel cell unit, and air is supplied as the oxidizing gas to the cathode side. A membrane electrode assembly, comprising a solid electrolyte membrane and a catalyst layer, is positioned between them. In this type of fuel cell system, electricity is generated through the reaction of hydrogen and oxygen from the air.

[0003] However, during the operation of a fuel cell system, hydrogen may leak from inside the stack to the outside due to component aging or malfunction, accumulating inside the casing housing the stack. To prevent hydrogen leakage from causing a decrease in fuel cell system efficiency and posing safety hazards due to accumulation inside the casing, existing fuel cell systems require hydrogen leak detection and are equipped with forced ventilation devices to release the accumulated hydrogen into the atmosphere. Typically, a hydrogen concentration sensor is installed at the vent of the casing to detect the hydrogen concentration inside, allowing for monitoring of the hydrogen concentration before and during fuel cell system operation.

[0004] In addition, to ensure that hydrogen emissions from the fuel cell system into the atmosphere meet regulatory requirements (for example, GB-T 24549-2020 Safety Requirements for Fuel Cell Electric Vehicles stipulates that during normal operation (including start-up and shutdown), the average hydrogen volume concentration within any consecutive 3 seconds should not exceed 4%, and the instantaneous hydrogen volume concentration should not exceed 8%), another hydrogen concentration sensor is installed at the outlet end of the exhaust pipe to detect the hydrogen concentration discharged from the exhaust pipe.

[0005] Therefore, existing fuel cell systems typically require at least two hydrogen concentration sensors. However, the high cost of these sensors increases the overall cost of the fuel cell system. Furthermore, the more hydrogen concentration sensors required, the more design, installation, and maintenance issues arise.

[0006] Therefore, existing methods for detecting hydrogen leaks in fuel cell systems and the fuel cell systems themselves need to be improved. Summary of the Invention

[0007] The purpose of this application is to provide a hydrogen leakage detection method and a fuel cell system for a fuel cell system, so as to overcome at least one of the above-mentioned technical problems.

[0008] Therefore, according to one aspect of this application, a method for detecting hydrogen leakage in a fuel cell system is provided, the fuel cell system comprising: a housing; an inlet pipe and an outlet pipe communicating with the housing, and a hydrogen concentration sensor disposed at the outlet end of the outlet pipe; and a bypass pipe disposed between the inlet pipe and the outlet pipe, the bypass pipe having a bypass valve disposed therein, the hydrogen leakage detection method comprising: setting the bypass valve to a fully open state and supplying air to the inlet pipe, such that the air is discharged from the outlet pipe via the bypass pipe; adjusting the opening of the bypass valve such that a first portion of the air enters the housing at a first volumetric flow rate and enters the outlet pipe from the housing, and a second portion of the air enters the outlet pipe via the bypass pipe at a second volumetric flow rate; acquiring a diluted hydrogen concentration measured by the hydrogen concentration sensor, and simultaneously acquiring a dilution ratio, the dilution ratio being expressed as the ratio of the sum of the first volumetric flow rate and the second volumetric flow rate to the first volumetric flow rate; and calculating the original hydrogen concentration inside the housing based on the diluted hydrogen concentration and the dilution ratio.

[0009] According to another aspect of this application, a fuel cell system is provided, comprising: a housing having an air inlet and an air outlet; a fuel cell stack disposed within the housing; an air inlet pipe having an inlet end connected to an air compressor and an outlet end connected to the air inlet; an exhaust pipe having an inlet end connected to the air outlet and an outlet end connected to the atmospheric environment, and a hydrogen concentration sensor disposed at the outlet end of the exhaust pipe; a bypass pipe disposed between the air inlet pipe and the exhaust pipe, allowing air in the air inlet pipe to enter the exhaust pipe via the bypass pipe, the bypass pipe having a bypass valve; and a control unit configured to perform the hydrogen leak detection method as described above.

[0010] The technical solution in this application eliminates the need for the existing hydrogen concentration sensor installed at the outlet of the casing to detect the hydrogen concentration inside the casing. Instead, hydrogen leak detection can be achieved simply by using a hydrogen concentration sensor installed at the outlet of the exhaust pipe. Therefore, it can reduce the cost of the fuel cell system and simplify its structure while providing safe and reliable detection results. Attached Figure Description

[0011] Exemplary embodiments of this application will now be described in detail with reference to the accompanying drawings. It should be understood that the embodiments described below are for illustrative purposes only and are not intended to limit the scope of this application.

[0012] In the picture:

[0013] Figure 1This is a schematic block diagram of a fuel cell system according to an embodiment of this application;

[0014] Figure 2 This is a schematic flowchart of a hydrogen leak detection method according to an embodiment of this application;

[0015] Figure 3 yes Figure 1 The diagram shows the timing sequence of the fuel cell system. Detailed Implementation

[0016] The preferred embodiments of this application are described in detail below with reference to examples. Those skilled in the art should understand that these exemplary embodiments do not imply any limitation on this application. The exemplary embodiments of this application do not imply that the hydrogen leak detection method of this application cannot include other steps, nor that the fuel cell system of this application cannot include other modules or components. Unless otherwise specified, features in the embodiments of this application can be combined with each other. It should be understood that the number, position, and order of steps of each module in the drawings are not intended to limit this application. The drawings are not drawn to scale, but some parts have been scaled for clarity.

[0017] The following reference Figures 1 to 3 This application describes a fuel cell system and a hydrogen leak detection method for a fuel cell system according to embodiments of the present application.

[0018] like Figure 1 As shown, the fuel cell system 100 according to an embodiment of this application includes a housing 60, a fuel cell stack 50 disposed within the housing 60, an air inlet pipe 10 and an exhaust pipe 20 in fluid communication with the housing 60. The housing 60 is provided with an air inlet 61 and an air outlet 62. When air is supplied through the air inlet 61, gas that may contain hydrogen leaking from the fuel cell stack 50 inside the housing 60 can be discharged through the air outlet 62.

[0019] The fuel cell stack 50 typically includes multiple fuel cell units stacked together. Each fuel cell unit may include two electrode plates and a membrane electrode assembly sandwiched between the two electrode plates. Electrochemical reactions occur to generate electricity when hydrogen and air are supplied to the anode and cathode sides of each fuel cell unit, respectively. During operation of the fuel cell stack 50, hydrogen may leak from the stack 50 and accumulate inside the housing 60 due to component aging, malfunctions, etc. The fuel cell stack 50 can be a common structure in the art, and therefore will not be described in further detail herein. It should be noted that, as... Figure 1 As illustrated schematically, the fuel cell system 100 includes multiple stacks 50, but this application is not limited thereto; for example, it may also include a single stack.

[0020] The inlet end 11 of the intake pipe 10 is connected to the air compressor 70, and the outlet end 12 of the intake pipe 10 is connected to the air inlet 61 of the outer casing 60. When the fuel cell system 100 is powered on, the air compressor 70 starts working first, pressurizing air into the intake pipe 10, which in turn blows out the gas inside the outer casing 60.

[0021] The inlet end 21 of the exhaust pipe 20 is connected to the outlet 62 of the housing 60, and the outlet end 22 of the exhaust pipe 20 is connected to the atmospheric environment. A hydrogen concentration sensor 40 is provided at the second end 22 of the exhaust pipe 20. The hydrogen concentration sensor 40 can detect the hydrogen concentration (e.g., volume concentration) in the gas discharged from the exhaust pipe 22.

[0022] Additionally, the fuel cell system 100 of this application may also include a bypass pipe 30. The bypass pipe 30 is disposed between the intake pipe 10 and the exhaust pipe 20, allowing air in the intake pipe 10 to enter the exhaust pipe 20 via the bypass pipe 30. In other words, the bypass pipe 30 allows air in the intake pipe 10 to bypass the housing 60 and enter the exhaust pipe 20. Figure 1 As shown, a bypass valve 31 is provided in the bypass pipe 30. The bypass valve 31 can be fully open, partially open, or closed. That is, the opening degree of the bypass valve 31 can be adjusted between 0 and the maximum value. The bypass valve 31 can adopt various structural forms, therefore, this paper will not describe the specific structure of the bypass valve 31 in detail.

[0023] Furthermore, the fuel cell system 100 of this application may also include a control unit 90, which is configured to perform the hydrogen leak detection method described in detail below. The control unit 90 is communicatively connected to the air compressor 70, the hydrogen concentration sensor 40, and the bypass valve 31, and can control the operation of the air compressor 70, acquire the diluted hydrogen concentration detected by the hydrogen concentration sensor 40, and control the opening degree of the bypass valve 31.

[0024] The following reference Figure 2 This application describes a hydrogen leak detection method according to embodiments thereof.

[0025] like Figure 2 As shown, in step 210, the bypass valve 31 is fully open, and air is supplied to the intake pipe 10, allowing the air to exit from the exhaust pipe 20 via the bypass pipe 30. In this step, because the bypass valve 31 is fully open, there is no pressure difference between the inlet and outlet ends of the bypass valve 31. The bypass pipe 30 remains unobstructed with the exhaust pipe 20, and the air pressure within the bypass pipe 30 is essentially atmospheric pressure. Therefore, the air from the intake pipe 10 directly enters the exhaust pipe 20 via the bypass pipe 30, without passing through the intake port 61 of the housing 60 to enter the housing 60. This allows any residual hydrogen gas in the exhaust pipe 20 to be blown out, ensuring the accuracy of subsequent test results. It should be noted that in Figure 1In the block diagram shown, there appears to be a long distance from the connection between the bypass pipe 30 and the exhaust pipe 20 to the inlet end 21 of the exhaust pipe 20. However, the bypass pipe 30 can actually be connected to the exhaust pipe 20 near the inlet end 21 of the exhaust pipe 20, so that as much of the hydrogen gas that may remain in the exhaust pipe 20 can be blown out as much as possible.

[0026] At step 220, the opening of the bypass valve 31 is adjusted so that a first portion of the air enters the housing 60 through the inlet 61 at a first volumetric flow rate V1 and enters the exhaust pipe 20 through the outlet 62, while a second portion of the air enters the exhaust pipe 20 through the bypass pipe 30 at a second volumetric flow rate V2. In this way, the leaked hydrogen gas accumulated inside the housing 60 can be discharged through the exhaust pipe 20 by the first portion of the air, while also being diluted by the second portion of the air from the bypass pipe 30.

[0027] This application proposes a bypass control mode for a bypass valve: increasing the pressure difference between the inlet and outlet of the bypass valve 31 reduces the second volumetric flow rate V2 within the bypass pipe 30. This not only blows out leaked hydrogen accumulated inside the housing 60 but also helps reduce the dilution of the hydrogen. In other words, the increase in the pressure difference across the bypass valve 31 is accompanied by an increase in the first volumetric flow rate V1 entering and exiting the housing 60.

[0028] At step 230, the diluted hydrogen concentration in the exhaust pipe 20, measured by the hydrogen concentration sensor 40, is obtained, and the dilution ratio is also obtained. The gas containing leaked hydrogen discharged from the housing 60 and the air discharged from the bypass pipe 30 mix (i.e., dilute) in the exhaust pipe 20, and the diluted hydrogen concentration C1 in the mixed gas is detected by the hydrogen concentration sensor 40. The ratio of the original hydrogen concentration C0 to the diluted hydrogen concentration C1 in the housing 60 is called the dilution ratio. The dilution ratio can be expressed as the ratio of the sum of the first volumetric flow rate V1 and the second volumetric flow rate V2 to the first volumetric flow rate V1, i.e., C0:C1=(V1+V2) / V1. The sum of the first volumetric flow rate V1 and the second volumetric flow rate V2 can be obtained by obtaining the third volumetric flow rate V3 flowing through the exhaust pipe 30.

[0029] At step 240, the initial hydrogen concentration C0 inside the casing 60 is calculated based on the diluted hydrogen concentration and the dilution ratio. For example, if the initial hydrogen concentration C0 inside the casing 60 is 8%, the following result can be obtained based on the dilution ratio:

[0030] When the dilution ratio is 100, the concentration of diluted hydrogen in the exhaust pipe 20 is 0.08.

[0031] When the dilution ratio is 50, the concentration of diluted hydrogen in the exhaust pipe 20 is 0.16.

[0032] When the dilution ratio is 25, the concentration of diluted hydrogen in the exhaust pipe 20 is 0.32.

[0033] Therefore, by using the above steps, the original hydrogen concentration C0 inside the housing 60 can be detected using only the hydrogen concentration sensor 40 installed at the outlet end 22 of the exhaust pipe 20, thus reducing the cost of the fuel cell system and simplifying its structure and maintenance.

[0034] It should be noted that, in order to improve the detection robustness of the hydrogen concentration sensor 40, the dilution effect of the air should be reduced, and the dilution ratio should be lowered. For example, the original hydrogen concentration C0 inside the housing 60 can be safely and reliably obtained when the dilution ratio is between 15 and 40.

[0035] As described above, the dilution ratio is achieved by adjusting the opening of the bypass valve 31; therefore, the dilution ratio corresponds to the opening of the bypass valve 31. A larger opening of the bypass valve 31 results in a larger dilution ratio, and vice versa. The dilution ratio can be determined by determining the opening of the bypass valve 31. The correspondence between the opening of the bypass valve 31 and the dilution ratio can be obtained through experimental calibration or simulation and stored as a lookup table in the memory of the control unit 90 for retrieval by the processor of the control unit 90. Alternatively, the dilution ratio can also be calculated based on the gas flow rate in the bypass pipe 30 and the exhaust pipe 20. For example, the volumetric flow rate of each pipe can be calculated by separately collecting the gas flow rate in the bypass pipe 30 and the exhaust pipe 20 and using the known pipe diameter (design parameter). It should be noted that this application is not limited to the above-described method of obtaining the dilution ratio, but various methods in the prior art that can be used to obtain the corresponding volumetric flow rates of the bypass pipe 30 and the exhaust pipe 20 can be used, which will not be described in further detail herein.

[0036] It should be noted that the hydrogen leak detection method is performed when the anode side of the fuel cell system 100 is stopped. This allows the leaked hydrogen accumulated inside the casing 60 to be expelled using air supplied through the intake pipe 10, and also avoids interference from hydrogen from the operating anode side with the detection results.

[0037] Refer again Figure 1The air inlet pipe 10 may not be specifically used for hydrogen leak detection, but can be further configured to supply air to the cathode side of the fuel cell stack 50 through the cathode pipe 80. Therefore, according to the inventive concept of this application, for fuel cell systems that draw air from the cathode inlet pipe for purging, the hydrogen leak detection method of this application can be applied without modifying the existing fuel cell system. In this case, a cathode inlet valve 81 may be provided in the cathode pipe 80, and the cathode inlet valve 81 is closed when performing the hydrogen leak detection method. At this time, the air from the air inlet pipe 10 can be used entirely for hydrogen leak detection. For fuel cell systems using other air intake methods, the hydrogen leak detection method of this application can also be applied with appropriate modifications.

[0038] The following reference Figure 3 To describe the operating timing of the fuel cell system in this application. Figure 3 In the diagram, the airflow process inside the outer casing 60 is represented by arrow A1, the airflow process inside the bypass pipe 30 is represented by arrow A2, the hydrogen purging process is represented by arrow H1, the hydrogen flow process during normal operation of the anode is represented by arrow H2, and the airflow process during normal operation of the cathode is represented by arrow A3. Figure 3 The horizontal axis represents time, and the length of each arrow corresponds to the duration of the process.

[0039] like Figure 3 As shown, at time t0, the air compressor 70 starts, supplying air to the intake pipe 10 and bypass pipe 30, allowing air to enter the exhaust pipe 20 via the bypass pipe 30, as indicated by arrow 2. Between time t0 and time t1, the bypass valve 31 remains fully open, allowing any residual hydrogen gas in the exhaust pipe 20 to be discharged, thus avoiding interference with the test results. During this process, because the bypass valve 31 is fully open, the air in the intake pipe 10 does not cause the gas inside the housing 60 to be discharged.

[0040] Then, at time t1, the opening of the bypass valve 31 is adjusted so that a first portion of the air in the intake pipe 10 enters the housing 60 through the intake port 61 at a first volumetric flow rate V1, thereby discharging the leaked hydrogen gas accumulated in the housing 60 into the exhaust pipe 20, as shown by arrow A1. A second portion of the air in the intake pipe 10 enters the exhaust pipe through the bypass pipe 30 at a second volumetric flow rate V2. Therefore, the leaked hydrogen gas discharged into the exhaust pipe 20 is diluted by the air from the bypass pipe 30.

[0041] Between time t2 and time t3, the diluted hydrogen concentration C1 within the exhaust pipe 20, measured by the hydrogen concentration sensor 40, can be obtained, along with the dilution ratio. Figure 3As can be seen, time t2 is later than time t1 because it takes time for the leaked hydrogen from the outer casing 60 to travel to the outlet 22 of the exhaust pipe 20. The time from time t1 to time t2 can be called the predetermined delay time T1. By designing the predetermined delay time T1, the accuracy of the detection results can be ensured. Preferably, the predetermined delay time T1 is between 1 and 3 seconds. The time from time t2 to time t3 can be called the detection time T2. During the detection time T2, multiple diluted hydrogen concentrations C1 and corresponding dilution ratios can be obtained, and the corresponding average values ​​can be calculated as the detection results.

[0042] Then, at time t3, hydrogen can be supplied to the anode side of the fuel cell system for hydrogen purging, preparing for normal operation of the anode side, such as... Figure 3 As indicated by arrow H1, this also shows that the hydrogen leak detection process is performed while the anode side is stopped. This ensures that the detected diluted hydrogen concentration comes only from the leaked hydrogen discharged from the casing 60, and not from the hydrogen coming from the operating anode side. The above process continues until time t4.

[0043] Then, at time t4, the hydrogen purging process ends, and hydrogen supply continues (as shown by arrow H2). The anode side begins normal operation, and air is simultaneously supplied to the cathode side of the fuel cell system (as shown by arrow A3), and the cathode side begins normal operation. In this case, bypass valve 31 can be closed. However, to regulate the pressure of the air supplied to the housing 60 and the air supplied to the cathode side, as well as the workload of the air compressor 70, bypass valve 31 can also be kept partially open.

[0044] In this way, hydrogen leak detection can be completed safely and reliably before the fuel cell system 100 is put into operation.

[0045] The present application has been described in detail above with reference to specific embodiments. Obviously, the above description and the embodiments shown in the accompanying drawings should be understood as exemplary and not as limiting the present application. Those skilled in the art can make various modifications or alterations without departing from the spirit of the present application, and such modifications or alterations do not depart from the scope of the present application.

Claims

1. A method for detecting hydrogen leakage in a fuel cell system (100), the fuel cell system (100) comprising: Outer shell (60); An intake pipe (10) and an exhaust pipe (20) are connected to the housing (60), and a hydrogen concentration sensor (40) is provided at the outlet end (22) of the exhaust pipe (20); and a bypass pipe (30) is provided between the intake pipe (10) and the exhaust pipe (20), and a bypass valve (31) is provided in the bypass pipe (30). The hydrogen leak detection method includes: The bypass valve (31) is fully open, and air is supplied to the intake pipe (10), so that the air is discharged from the exhaust pipe (20) through the bypass pipe (30); Adjust the opening of the bypass valve (31) so that the first part of the air enters the housing (60) at a first volume flow rate and enters the exhaust pipe (20) from the housing (60), and the second part of the air enters the exhaust pipe (20) via the bypass pipe (30) at a second volume flow rate; The diluted hydrogen concentration measured by the hydrogen concentration sensor (40) is obtained, and the dilution ratio is obtained, which is expressed as the ratio of the sum of the first volume flow rate and the second volume flow rate to the first volume flow rate. as well as The original hydrogen concentration inside the outer shell (60) is calculated based on the diluted hydrogen concentration and the dilution ratio.

2. The hydrogen leak detection method according to claim 1, wherein, The dilution ratio corresponds to the opening degree of the bypass valve (31), and the correspondence between the dilution ratio and the opening degree is stored as a lookup table.

3. The hydrogen leak detection method according to claim 1 or 2, wherein, The dilution ratio is calculated based on the gas flow rate in the bypass pipe (30) and the exhaust pipe (20).

4. The hydrogen leak detection method according to claim 1, wherein, The dilution ratio is 15 to 40.

5. The hydrogen leak detection method according to claim 1, wherein, The dilute hydrogen concentration and dilution ratio are acquired only after a predetermined delay time following the adjustment of the opening of the bypass valve (31).

6. The hydrogen leak detection method according to claim 5, wherein, The predetermined delay time is between 1 and 3 seconds.

7. The hydrogen leak detection method according to claim 1, wherein, The hydrogen leak detection method is performed when the fuel cell system (100) is stopped from operating.

8. A fuel cell system (100), comprising: The outer casing (60) is provided with an air inlet (61) and an air outlet (62); The fuel cell stack (50) is disposed within the housing (60); An air intake pipe (10) is provided, the inlet end (11) of which is connected to an air compressor (70), and the outlet end (12) of which is connected to an air inlet (61). An exhaust pipe (20) is provided, wherein the inlet end (21) of the exhaust pipe (20) is connected to the outlet (62), and the outlet end (22) of the exhaust pipe (20) is connected to the atmospheric environment, and a hydrogen concentration sensor (40) is provided at the outlet end (22) of the exhaust pipe (20). A bypass pipe (30) is provided between the intake pipe (10) and the exhaust pipe (20) so that air in the intake pipe (10) can enter the exhaust pipe (20) through the bypass pipe (30), and a bypass valve (31) is provided in the bypass pipe (30). and A control unit (90) configured to perform the hydrogen leak detection method according to any one of claims 1 to 7.

9. The fuel cell system (100) according to claim 8, wherein, The air intake pipe (10) is further configured to supply air to the cathode side of the fuel cell stack (50) through the cathode tube (80).

10. The fuel cell system (100) according to claim 9, wherein, The cathode tube (80) is provided with a cathode inlet valve (81), and the cathode inlet valve (81) is closed when the hydrogen leak detection method is performed.

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