A method for detecting the low-temperature airtightness of fuel cells

Abstract

This invention provides a low-temperature airtightness testing device for fuel cells, comprising: a fuel cell stack, a water pump, a water tank, an external cooling heat exchanger, pressure gauge I, pressure gauge II, an air outlet exhaust valve, and a hydrogen outlet exhaust valve. The fuel cell stack coolant inlet and outlet are connected to the water pump outlet and the external cooling heat exchanger inlet, respectively. The external cooling heat exchanger outlet is connected to the water tank inlet, and the water tank outlet is connected to the water pump inlet. The fuel cell stack is provided with a stack air inlet, a stack air outlet, a stack hydrogen inlet, and a stack hydrogen outlet. The stack air inlet is connected to pressure gauge I, the stack air outlet is connected to the air outlet exhaust valve, the stack hydrogen inlet is connected to pressure gauge II, and the stack hydrogen outlet is connected to the hydrogen outlet exhaust valve. The technical solution of this invention solves the problems of complex, inefficient, and inaccurate low-temperature environment testing procedures in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of proton exchange membrane fuel cell technology, and more particularly to a method for detecting the low-temperature airtightness of fuel cells. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are clean and efficient energy conversion devices with advantages such as being green and pollution-free, highly efficient, and low-noise. During operation, the three chambers of a PEMFC require a continuous flow of hydrogen, air, and coolant; therefore, ensuring good airtightness of the cell during operation is crucial.

[0003] In normal temperature environments, most methods for testing the airtightness of fuel cell stacks are pressure drop method or flow rate method, which judge the airtightness of the fuel cell stack by changes in air pressure and flow rate. Moreover, the pressure drop method has high requirements for the airtightness of the connecting pipelines.

[0004] In low-temperature environments, the different properties of materials lead to differences in their shrinkage, which reduces the accuracy of testing equipment using pressure drop or flow rate methods and the airtightness of connecting pipelines. This results in larger measurement errors in the testing equipment, affecting the accuracy and efficiency of the test results. It also makes it impossible to accurately determine the airtightness of the battery under low-temperature conditions. Furthermore, to ensure the battery is in a low-temperature environment, it is necessary to isolate the battery from the specific connected equipment, which increases the complexity of the testing work. Summary of the Invention

[0005] To address the aforementioned technical problems of low efficiency, inaccuracy, and complex testing procedures in low-temperature environments, this invention provides a method for detecting the airtightness of fuel cells at low temperatures. This invention, while ensuring the water pump operates at low temperatures, primarily utilizes changes in the water tank level and the battery voltage to simply and effectively determine the airtightness of the fuel cell.

[0006] The technical means employed in this invention are as follows:

[0007] A fuel cell low-temperature airtightness testing device includes: a fuel cell stack, a water pump, a water tank, an external cooling heat exchanger, pressure gauge I, pressure gauge II, an air outlet exhaust valve, and a hydrogen outlet exhaust valve.

[0008] The coolant inlet and coolant outlet of the fuel cell stack are connected to the outlet of the water pump and the inlet of the external cooling heat exchanger, respectively. The outlet of the external cooling heat exchanger is connected to the inlet of the water tank, and the outlet of the water tank is connected to the inlet of the water pump.

[0009] The fuel cell stack is provided with a stack air inlet, a stack air outlet, a stack hydrogen inlet, and a stack hydrogen outlet. The stack air inlet is connected to pressure gauge I, the stack air outlet is connected to the air outlet tail valve, the stack hydrogen inlet is connected to pressure gauge II, and the stack hydrogen outlet is connected to the hydrogen outlet tail valve.

[0010] Furthermore, the water tank is cylindrical with a diameter of 15cm, and a vent hole is provided on the water tank.

[0011] Furthermore, the external cooling heat exchanger is provided with an external cooling circulation inlet and an external cooling circulation outlet.

[0012] A method for detecting the airtightness of a fuel cell at low temperature, the specific steps of which are as follows:

[0013] S1. Place the fuel cell low-temperature airtightness testing device in a low-temperature environment and confirm that the device is properly connected. Then turn on the water pump to allow the coolant to circulate fully in the fuel cell stack until the stack is full. Continue to circulate for 5 minutes after the stack temperature reaches the predetermined value, and then turn off the water pump.

[0014] S2. Introduce hydrogen and air into the hydrogen chamber and air chamber of the fuel cell stack respectively, and open the air outlet exhaust valve and hydrogen outlet exhaust valve. Adjust the air flow rate to 200 mA / cm². 2 The air flow rate corresponding to the current density is recorded. The hydrogen side is pressure controlled to ensure that the hydrogen side pressure is 40 kPa higher than the air side pressure. The initial voltage V0 of the fuel cell stack is recorded 1 minute after the gas is introduced.

[0015] S3. Stop the air supply, close the hydrogen outlet tail valve, maintain the hydrogen side pressure 40 kPa higher than the air side, and record the final voltage V1 of the fuel cell stack after 1 minute.

[0016] S4. Calculate the difference ΔV between the initial voltage and the final voltage of the fuel cell stack and the voltage drop rate K, determine the gas tightness of the fuel cell stack membrane electrode, and indirectly compare the gas leakage of the membrane electrode of different fuel cell stacks based on the voltage drop rate K.

[0017] Furthermore, the formula for calculating the voltage drop rate K is as follows:

[0018]

[0019] In the formula: Δt represents the time interval for recording the initial voltage and the final voltage;

[0020] V1 represents the final voltage after gas supply stops for t minutes;

[0021] V0 represents the initial voltage after ventilation.

[0022] A method for detecting the airtightness of fuel cells at low temperatures, comprising the following specific steps for detecting the airtightness of bipolar plates:

[0023] S1. Place the fuel cell low-temperature airtightness testing device in a low-temperature environment and confirm that the device is properly connected. Then, open the water valve to allow the coolant to circulate fully in the fuel cell stack until it is full. Continue to circulate for 5 minutes after the stack temperature reaches the predetermined value, and then turn off the water pump.

[0024] S2. The water level in the tank stabilizes 1 minute after the water pump is turned off. Record the water level height h0 at this time.

[0025] S3. Introduce hydrogen and air into the hydrogen chamber and air chamber of the fuel cell stack respectively, and adjust the air flow rate to 500 mA / cm. 2 The air flow rate corresponding to the current density is controlled by pressure on the hydrogen side to ensure that the hydrogen side pressure is 20 kPa higher than the air side pressure. Adjust the air outlet tail valve and the hydrogen outlet tail valve to make the air inlet pressure reach 50 kPa and the hydrogen side inlet pressure 70 kPa.

[0026] S4. After setting the parameters, wait for the liquid level to stabilize for 1 minute and then record the liquid level height h1 in the water tank.

[0027] S5. Compare the recorded data h0 and h1 to determine the airtightness of the bipolar plate. If h0 < h1, the bipolar plate has poor airtightness and there is a leak. Further confirmation is needed to determine whether it is hydrogen or air leaking into water.

[0028] S6. Turn on the water pump to allow the coolant to re-enter the fuel cell stack and circulate fully until the stack is full. Continue to circulate for 5 minutes after the stack temperature reaches the predetermined value, and then turn off the water pump.

[0029] S7. One minute after the water pump is turned off, the water level in the tank stabilizes. Record the water level height h0' at this time and keep h0' = h0.

[0030] S8. Introduce hydrogen into the hydrogen chamber of the fuel cell stack and adjust the hydrogen outlet tail valve until the hydrogen side pressure is 70 kPa. After the liquid level stabilizes for 1 minute, record the water tank liquid level height h2.

[0031] S9. By comparing the magnitudes of Δh', h2, and h1, you can indirectly determine which gas is being mixed with water. Δh' = h2 - h1. If Δh' = 0, it is hydrogen mixing with water. If Δh' < 0 and h2 > h0, it is hydrogen and air mixing with water. If Δh' < 0 and h2 = h0, it is air mixing with water.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] 1. The present invention provides a method for detecting the airtightness of fuel cells at low temperature. The method determines the airtightness of fuel cells by detecting the voltage difference of the fuel cell stack and the change of the liquid level in the water tank. The method uses an external cooling heat exchanger to regulate the internal temperature of the battery, so that the battery can be tested directly on a test bench or in a system without the need for connecting additional pipelines and equipment. The method is simple and practical to operate and can effectively determine the airtightness.

[0034] 2. The present invention provides a method for detecting the air tightness of fuel cells at low temperature. By comparing the rate of change of voltage, the amount of air leakage can be indirectly compared, and the air tightness of the membrane electrode can be determined. By detecting the change of the water level in the water tank, the air tightness of the bipolar plate can be determined.

[0035] In summary, the technical solution of this invention utilizes changes in the water level in the tank and the voltage changes in the battery to simply and effectively determine the airtightness of the fuel cell. Therefore, the technical solution of this invention solves the problems of low efficiency, inaccuracy, and complex detection procedures in existing technologies for low-temperature environments.

[0036] Based on the above reasons, this invention can be widely promoted in fields such as proton exchange membrane fuel cells. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the fuel cell low-temperature airtightness testing device described in this invention.

[0039] Figure 2 This is a comparison chart of the airtightness test results of the electrode stack membrane at different temperatures as described in this invention.

[0040] Figure 3 This is a comparison chart of the airtightness test results of different fuel cell stacks described in this invention.

[0041] In the diagram: 1. Fuel cell stack; 2. Water pump; 3. Water tank; 4. External cooling heat exchanger; 5. Stack air inlet; 6. Stack air outlet; 7. Stack hydrogen inlet; 8. Stack hydrogen outlet; 9. External cooling circulation inlet; 10. External cooling circulation outlet; 11. Water tank vent; 12. Low temperature environment; 13. Air outlet tail valve; 14. Hydrogen outlet tail valve. Detailed Implementation

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0045] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0046] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0047] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0048] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0049] Example 1

[0050] like Figure 1 As shown, the present invention provides a device for detecting the low-temperature airtightness of a fuel cell, comprising: a fuel cell stack 1, a water pump 2, a water tank 3, an external cooling heat exchanger 4, a pressure gauge I, a pressure gauge II, an air outlet exhaust valve 13, and a hydrogen outlet exhaust valve 14.

[0051] The coolant inlet and coolant outlet of the fuel cell stack 1 are connected to the outlet of the water pump 2 and the inlet of the external cooling heat exchanger 4, respectively. The outlet of the external cooling heat exchanger 4 is connected to the inlet of the water tank 3, and the outlet of the water tank 3 is connected to the inlet of the water pump 2, forming a closed loop for coolant circulation.

[0052] The fuel cell stack 1 is provided with a stack air inlet 5, a stack air outlet 6, a stack hydrogen inlet 7, and a stack hydrogen outlet 8. The stack air inlet 5 is connected to the pressure gauge I, the stack air outlet 6 is connected to the air outlet tail valve 13, the stack hydrogen inlet 7 is connected to the pressure gauge II, and the stack hydrogen outlet 8 is connected to the hydrogen outlet tail valve 14.

[0053] Pressure gauge I and pressure gauge II are used to monitor the gas pressure at the fuel cell air inlet and the fuel cell hydrogen inlet.

[0054] The water tank 3 is cylindrical with a diameter of 15cm. The water tank 3 is provided with a water tank vent 11 for discharging gas that has entered the hydrogen chamber or air chamber.

[0055] The external cooling heat exchanger 4 is provided with an external cooling circulation inlet 9 and an external cooling circulation outlet 10, which are used to introduce the external cooling circulation medium to cool the coolant of the fuel cell stack 1.

[0056] This invention also provides a method for detecting the low-temperature airtightness of fuel cells. The method includes a membrane electrode airtightness detection method and a bipolar plate airtightness detection method, with the specific detection steps as follows:

[0057] Electrode stack airtightness test:

[0058] S1. Place the fuel cell low-temperature airtightness testing device in a low-temperature environment and confirm that the device is properly connected. Then turn on the water pump 2 to allow the coolant to circulate fully in the fuel cell stack 1 until it is full. Continue to circulate for 5 minutes after the temperature of the fuel cell stack 1 reaches the predetermined value, and then turn off the water pump 2.

[0059] S2. Introduce hydrogen and air into the hydrogen chamber and air chamber of fuel cell stack 1 respectively, and open the air outlet exhaust valve 13 and the hydrogen outlet exhaust valve 14 to adjust the air flow rate to 200 mA / cm. 2 The air flow rate corresponding to the current density is controlled by pressure on the hydrogen side. The gas pressure at the air inlet and hydrogen inlet of fuel cell stack 1 is monitored by pressure gauges I and II to ensure that the hydrogen side pressure is 40 kPa higher than the air side pressure. The voltage of fuel cell stack 1 is monitored by the inspection instrument. The initial voltage V0 of fuel cell stack 1 monitored by the inspection instrument is recorded 1 minute after the gas is introduced.

[0060] S3. Stop the air supply, close the hydrogen outlet tail valve 14, maintain the hydrogen side pressure 40 kPa higher than the air side, and record the final voltage V1 of the fuel cell stack 1 monitored by the inspection instrument after 1 minute.

[0061] S4. Calculate the difference between the initial voltage and the final voltage of fuel cell stack 1, ΔV, and the voltage drop rate K to determine the membrane electrode airtightness of fuel cell stack 1 and indirectly compare the membrane electrode gas leakage of different stacks.

[0062] The principle of membrane electrode airtightness detection in fuel cell stacks is as follows: Poor membrane electrode airtightness is mainly manifested in the large permeability of the proton exchange membrane, which leads to hydrogen-oxygen crosstalk. After hydrogen and air are introduced into the hydrogen chamber and air chamber of the fuel cell respectively, under the action of the catalyst, hydrogen and air form an electromotive force at the two electrodes of the proton exchange membrane fuel cell. If the external circuit is in the open state, no current is formed. Under the condition of absolutely good airtightness, after a certain amount of gas is introduced, its open circuit voltage will remain stable. However, the proton exchange membrane has a certain permeability. Over time, its open circuit voltage will continue to decrease. Moreover, the greater the permeability, the faster the voltage drop rate (K). Therefore, the airtightness of the membrane electrode can be judged based on the voltage drop rate.

[0063] Therefore, based on the formula for calculating the voltage drop rate K, the data recorded during the detection is substituted into the formula to calculate the voltage drop rate K, which is used to determine the airtightness and permeability of the fuel cell. The formula for the voltage drop rate K is as follows:

[0064]

[0065] In the formula: Δt represents the time interval for recording the initial voltage and the final voltage;

[0066] V1 represents the final voltage after gas supply stops for t minutes;

[0067] V0 represents the initial voltage after ventilation.

[0068] The open-circuit voltage of a fuel cell is also affected by factors such as temperature, pressure, platinum content in the catalyst, and catalyst activity. For commercial fuel cell membrane electrode assemblies, the open-circuit voltage will also decrease in low-temperature environments (T < 0℃) due to the low cell temperature.

[0069] According to the described method for testing the airtightness of the membrane electrode stack, the membrane electrode was tested at 70℃, 25℃, -30℃, and -40℃, respectively. The experimental results are as follows: Figure 2 As shown, analysis Figure 2 The data shows that the final voltage V1 varies significantly at different temperatures. The voltage drop rate is calculated using the voltage drop rate formula K. As the temperature increases, the voltage drop rate gradually increases, indicating that the airtightness of the membrane electrode gradually deteriorates with increasing temperature. This suggests that the membrane electrode has the best airtightness at -40℃ and the worst airtightness at 70℃. The airtightness detection method for the membrane electrode described above can effectively determine the airtightness of the membrane electrode.

[0070] According to the method for testing the membrane electrode tightness of fuel cell stacks, membrane electrode tightness tests were performed on different fuel cell stacks under the same temperature conditions, and the results are as follows. Figure 3 As shown, the voltage drop rate K of fuel cell stacks #1 and #2 was calculated according to the formula for voltage drop rate K. The initial voltages V0 of fuel cell stacks #1 and #2 were basically the same. After the gas supply was stopped for 1 minute, the final voltages V1 of fuel cell stacks #1 and #2 showed a difference. The final voltage of fuel cell stack #2 was significantly lower than that of fuel cell stack #1. Therefore, the voltage drop rate of fuel cell stack #2 was greater, and the airtightness of the membrane electrode was worse. The significant difference in the voltage drop rate of different fuel cell stacks within the same time period also indicates that the airtightness of the membrane electrode is different in different fuel cell stacks.

[0071] Battery stack bipolar plate airtightness test:

[0072] S1. Place the fuel cell low-temperature airtightness testing device in a low-temperature environment and confirm that the device is properly connected. Then, open the water valve 2 to allow the coolant to circulate fully in the fuel cell stack 1 until the stack is full. Continue to circulate for 5 minutes after the stack temperature reaches the predetermined value, and then turn off the water pump 2.

[0073] S2. After water pump 2 is turned off for 1 minute, the water level in the tank stabilizes. Record the water level height h0 in the tank at this time.

[0074] S3. Introduce hydrogen and air into the hydrogen chamber and air chamber of the fuel cell stack respectively, and adjust the air flow rate to 500 mA / cm. 2 The air flow rate corresponding to the current density is controlled by pressure on the hydrogen side. The air outlet tail valve 13 and the hydrogen outlet tail valve 14 are adjusted. The gas pressure at the air inlet and hydrogen inlet of the fuel cell stack 1 is monitored by pressure gauge I and pressure gauge II to ensure that the hydrogen side pressure is 20 kPa higher than the air side pressure.

[0075] S4. After setting the parameters, wait for the liquid level to stabilize for 1 minute and then record the liquid level height h1 in water tank 3.

[0076] S5. Compare the recorded data h0 and h1 to determine the airtightness of the bipolar plate. If h0 < h1, the bipolar plate has poor airtightness and there is a leak. Further confirmation is needed to determine whether it is hydrogen or air leaking into water.

[0077] S6. Turn on water pump 2 to allow the coolant to re-enter the fuel cell stack 1 and circulate fully until the stack is full. Continue to circulate for 5 minutes after the stack temperature reaches the predetermined value, and then turn off water pump 2.

[0078] S7. After water pump 2 is turned off for 1 minute, the water level in the tank stabilizes. Record the water level height h0' in the tank at this time and keep h0' = h0.

[0079] S8. Introduce hydrogen into the hydrogen chamber of the fuel cell stack and adjust the hydrogen outlet tail valve. Monitor the air side and hydrogen side pressures using pressure gauges I and II until the hydrogen side pressure is 70 kPa and the air side pressure is 50 kPa. After the liquid level stabilizes for 1 minute, record the liquid level height h2 in water tank 3.

[0080] S9. By comparing the magnitudes of Δh', h2, and h1, you can indirectly determine which gas is being mixed with water. Δh' = h2 - h1. If Δh' = 0, it is hydrogen mixing with water. If Δh' < 0 and h2 > h0, it is hydrogen and air mixing with water. If Δh' < 0 and h2 = h0, it is air mixing with water.

[0081] The working principle of the bipolar plate airtightness detection is as follows: the fuel cell stack / system is placed in a low-temperature environment, the cooling circulation loop is filled with coolant, and the initial liquid level height h0 in the cooling water tank 3 of the circulation loop is recorded. Hydrogen is gradually introduced into the hydrogen chamber of the stack, so that the hydrogen fills the entire chamber, and the pressure is controlled to be stable at p1. Air is introduced into the air chamber, and the pressure is controlled to be stable at p2. The liquid level change in the cooling water tank 3 of the entire process is observed, and the liquid level height h1 after stabilization for time t is recorded. The airtightness and relative leakage of the bipolar plate in the low-temperature environment are judged based on the liquid level change Δh before and after air introduction. Furthermore, the relationship between Δh, h2 and h0 can be compared to determine whether it is hydrogen-water leakage, air-water leakage, or hydrogen and air leakage at the same time.

[0082] According to the described bipolar plate airtightness testing method, bipolar plates with different materials and adhesive sealing structures were tested at 25℃, -30℃, and -40℃. The thickness of the membrane electrode used also varied, so that the pressure at the air inlet reached 50 kPa and the pressure at the hydrogen inlet was 70 kPa. The test results are shown in Table 1. Analysis of the data in Table 1 shows that the airtightness of the bipolar plate of stack #3 is good under normal temperature and low temperature conditions, with no obvious gas leakage. The airtightness of the bipolar plate of stack #4 is good at normal temperature, but poor at -30℃ and -40℃, with serious hydrogen-oxygen-water leakage. Moreover, the leakage at -40℃ is greater than that at -30℃, indicating that there are differences in the airtightness of bipolar plates with different materials and adhesive sealing structures.

[0083] Table 1. Data on fuel cell stack airtightness test

[0084]

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting the low-temperature gas tightness of a fuel cell, characterized by, The specific steps are as follows: S1, the fuel cell low temperature airtightness detection device is placed in a low temperature environment, and after it is confirmed that the device is connected perfectly, a water valve is opened, cooling liquid is made to enter the fuel cell stack to fully circulate, until the stack is filled, after the stack temperature reaches a predetermined value, the circulation is continued for 5 minutes, and then the water pump is closed; S2, water pump off 1 min after the water tank liquid surface stable, record the liquid level at this time h 0; S3, respectively into the hydrogen cavity and air cavity of the hydrogen and air, the air side flow is adjusted to 500 mA / cm 2 The air flow corresponding to the current density, the hydrogen side is pressure control, to ensure that the hydrogen side pressure is higher than the air side pressure 20 kPa, adjust the air outlet tail exhaust valve and hydrogen outlet tail exhaust valve, so that the pressure of air inlet is 50 kPa, the hydrogen side inlet pressure is 70 kPa; S4, after the parameter setting is completed, the liquid surface is stabilized for 1 minute, and then the water tank liquid level h1 is recorded; S5, the recorded data h0 and h1 are compared and recorded, the bipolar plate airtightness is judged, if h0 S6, the water pump is opened, the cooling liquid is made to re-enter the fuel cell stack to fully circulate, until the stack is filled, after the stack temperature reaches a predetermined value, the circulation is continued for 5 minutes, and then the water pump is closed; S7, after the water pump is closed for 1 minute, the water tank liquid level h0' is recorded, and h0'=h0 is kept; S8, hydrogen is introduced into the hydrogen cavity of the stack, and a hydrogen outlet tail exhaust valve is adjusted, until the hydrogen side pressure is 70 kPa, after the liquid surface is stabilized for 1 minute, the water tank liquid level h2 is recorded; S9, by comparison The indirect judgment of the size relationship between h2 and h1 is which gas is watered, h2-h1, if h2-h1=0 is hydrogen water, if h2-h1<0 and h2>h0 is hydrogen and air water, if h2-h1<0 and h2=h0 is air water.

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