Device and Method for Evaluating the Start-Stop Durability of a Fuel Cell Stack

Abstract

The present invention provides a device and method for evaluating the start-stop durability of a fuel cell stack, which includes: an anode pipeline, including a hydrogen pipeline, an air main path, a first pipeline and a first bypass, and an anode exhaust pipe. The air main path is connected to the first pipeline and the first bypass through a first three-way valve. Both the first pipeline and the hydrogen pipeline are used to communicate with the anode inlet of the battery stack, and a first stop valve is provided on the hydrogen pipeline, and a second stop valve is provided on the first bypass; the anode exhaust pipe is used to communicate with the anode outlet of the battery stack, and a third stop valve is provided on the anode exhaust pipeline; a cathode pipeline, including a second pipeline, a second bypass and a cathode exhaust pipe. The cathode inlet pipe is connected to the second pipeline and the second bypass through a second three-way valve, and the second pipeline is used to communicate with the cathode inlet of the battery stack; the cathode exhaust pipe is used to communicate with the cathode outlet of the battery stack, and the second bypass and the cathode exhaust pipe are connected to the main exhaust pipe through a third three-way valve. The present invention makes the gas switching speeds on both the anode and cathode sides of the stack nearly the same, improving the accuracy of the start-stop durability test of the fuel cell stack.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and particularly to a device and method for evaluating the start-stop durability of a fuel cell stack. Background Art

[0002] Start-up and shutdown are one of the most frequent operating conditions encountered during the life cycle of a fuel cell. Start-stop durability is one of the key characteristics of a fuel cell stack. During the start-up process, a hydrogen-oxygen interface is formed on the anode side, causing carbon corrosion on the cathode side, thereby resulting in stack degradation. Therefore, a method and device for quickly evaluating the start-stop durability of a fuel cell stack are crucial.

[0003] Chinese patents CN201156078Y and CN101158711B respectively disclose methods and devices for evaluating start-stop durability, both of which directly introduce air into the anode inlet and control the on-off through a solenoid valve. The main disadvantages of this technology are that the structure is too simple, and the process of directly switching hydrogen with air is quite different from the actual fuel cell shutdown process; moreover, during the switching process, if the switching speeds of the anode and cathode are inconsistent, an OCV positive voltage or negative voltage may be formed. Chinese patent CN111082108A improves the device on the basis of the previous patent, mainly adding gas treatment and monitoring modules such as temperature and humidity control and CO2 concentration detection; however, this patent also does not improve from the fundamental aspect of start-stop acceleration tests and the gas switching states on both sides of the fuel cell stack, and there are still problems such as slow switching speed or inconsistent switching speeds on both sides of the anode and cathode.

[0004] Therefore, a device and method for evaluating the start-stop durability of a fuel cell stack are needed to achieve consistent switching speeds on both sides of the anode and cathode. Summary of the Invention

[0005] In view of the above-mentioned disadvantages of the prior art, the technical problem to be solved by the present invention is to provide a device and method for evaluating the start-stop durability of a fuel cell stack, so as to solve the problem of inconsistent switching speeds on both sides of the anode and cathode during the start-stop durability test of the fuel cell stack in the prior art.

[0006] To solve the above technical problem, the present invention provides a device for evaluating the start-stop durability of a fuel cell stack, which includes:

[0007] An anode pipeline, including a hydrogen pipeline, an air main pipeline, a first pipeline and a first bypass, and an anode exhaust pipe. The air main pipeline is connected to the first pipeline and the first bypass through a first three-way valve. Both the first pipeline and the hydrogen pipeline are used to communicate with the anode inlet of the fuel cell stack, and a first stop valve is provided on the hydrogen pipeline, and a second stop valve is provided on the first bypass; the anode exhaust pipe is used to communicate with the anode outlet of the fuel cell stack, and a third stop valve is provided on the anode exhaust pipeline;

[0008] The cathode pipeline includes a second pipeline, a second bypass, and a cathode exhaust pipe. The cathode inlet pipe is connected to the second pipeline and the second bypass through a second three-way valve. The second pipeline is used to communicate with the cathode inlet of the battery stack; the cathode exhaust pipe is used to communicate with the cathode outlet of the battery stack. The second bypass and the cathode exhaust pipe are connected to the main exhaust pipe through a third three-way valve;

[0009] The control system is connected to the first three-way valve, the second three-way valve, the third three-way valve, the first stop valve, the second stop valve, and the third stop valve to control the actions of each valve.

[0010] Preferably, a check valve is provided on the first pipeline, and the check valve is located between the first three-way valve and the anode inlet.

[0011] Preferably, a check valve is provided on the hydrogen pipeline, and the check valve is located between the first stop valve and the anode inlet.

[0012] Preferably, an air flow meter is provided on the main air pipeline.

[0013] The present invention also provides a method for evaluating the start-stop durability of a fuel cell stack, which uses the device for evaluating the start-stop durability of a fuel cell stack as described above, and includes the following steps:

[0014] 1) The fuel cell stack is shut down, and the oxygen on the cathode side of the stack is consumed by discharging until the voltage drops to 0V;

[0015] 2) Open the second stop valve, and synchronously adjust the second three-way valve and the third three-way valve so that air is discharged through the main air pipeline and the first bypass at a first preset flow rate, and air is discharged through the cathode inlet pipe, the second bypass, and the main exhaust pipe at a second preset flow rate. The first preset flow rate and the second preset flow rate are different;

[0016] 3) Synchronously adjust the first three-way valve, the second three-way valve, and the third three-way valve. At the same time, close the second stop valve and open the third stop valve so that the air in the main air pipeline enters the fuel cell stack through the first pipeline, and the air at the cathode enters the fuel cell stack through the cathode inlet pipe, and then wait for a preset time;

[0017] 4) Monitor the single-cell voltage of the fuel cell stack and reset all parameters to zero;

[0018] 5) Adjust the first three-way valve to connect the main air pipeline with the first bypass, open the first stop valve, start the fuel cell stack, and the fuel cell stack runs to the performance operation judgment point;

[0019] 6) Determine whether the performance of the fuel cell stack reaches the specified performance decay value. If so, calculate the start-stop durability of the fuel cell stack. If not, repeat steps 1)-5) until the performance of the fuel cell stack reaches the specified performance decay value.

[0020] Preferably, the calibration process of the second preset flow rate and the first preset flow rate is as follows:

[0021] The A battery stack shuts down and discharges normally, maintaining the battery stack in the hydrogen / hydrogen state for a certain period of time;

[0022] B sends air with a first flow rate value into the first bypass and air with a second flow rate value into the second bypass. The first flow rate value is the maximum flow rate of the main air path, which is the first preset flow rate; the second flow rate value is less than the first flow rate value;

[0023] C synchronously adjusts the first three-way valve, the second three-way valve, and the third three-way valve, closes the second stop valve, and opens the third stop valve at the same time, so that the air in the main air path enters the battery stack through the first pipeline, and the air at the cathode enters the battery stack through the cathode inlet pipe, and then waits for a certain period of time;

[0024] D monitors the voltage of the battery stack, and repeats steps A-C according to the voltage situation. If the voltage is a positive voltage, increase the magnitude of the second flow rate value; if a negative voltage appears, decrease the magnitude of the second flow rate value; until there is no voltage generated in the battery stack, the current second flow rate value is the second preset flow rate.

[0025] Preferably, the preset time is 1 - 2 min.

[0026] Preferably, all the parameters include the air flow rate, air temperature, and dew point of air in the main air path.

[0027] As described above, the device and method for evaluating the start-stop durability of a fuel cell stack of the present invention have the following beneficial effects: by providing bypasses, namely the first bypass and the second bypass, in both the anode pipeline and the cathode pipeline, when performing the start-stop durability test, before quickly switching the stack from the hydrogen / hydrogen state to the air / air state, a certain flow rate of air can be simultaneously introduced through the first bypass and the second bypass and discharged to the outlet, and then the positions of the first three-way valve and the second three-way valve are simultaneously switched, so that a certain flow rate of gas enters the anode and cathode of the stack at the same time, ensuring that the gas switching speeds on both sides of the anode and cathode of the stack are close to the same, thereby more accurately simulating the normal use of the battery stack and improving the accuracy of the start-stop durability test of the battery stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It shows a schematic diagram of the device for evaluating the start-stop durability of a fuel cell stack of the present invention.

[0029] Figure 2 It shows a schematic diagram of bypass air intake in the device for evaluating the start-stop durability of a fuel cell stack.

[0030] Figure 3 It shows a schematic diagram of air entering both the cathode and anode of a fuel cell stack simultaneously.

[0031] Figure 4 It shows a schematic diagram of air intake during the normal startup of a fuel cell stack.

[0032] Figure 5 It shows a schematic diagram of the method flow for evaluating the start-stop durability of a fuel cell stack according to the present invention.

[0033] Description of component labels

[0034] 1 Fuel cell stack

[0035] 2 Air flow meter

[0036] 3 First three-way valve

[0037] 4, 6 Check valve

[0038] 5 First stop valve

[0039] 7 Second three-way valve

[0040] 8 Third stop valve

[0041] 9 Third three-way valve

[0042] 10 Second stop valve

[0043] 11 First pipeline

[0044] 12 First bypass

[0045] 13 Second pipeline

[0046] 14 Second bypass Detailed implementation manners

[0047] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0048] It should be noted that the structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the conditions for the implementation of the present invention. Therefore, they do not have substantial technical significance. Any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle", and "one" cited in this specification are only for the convenience of clear narration and are not used to limit the scope for the implementation of the present invention. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope in which the present invention can be implemented.

[0049] As Figure 1 shown, the present invention provides a device for evaluating the start-stop durability of a fuel cell stack, which includes:

[0050] An anodic gas pipeline, including a hydrogen gas pipeline, an air main pipeline, a first pipeline 11 and a first bypass 12, and an anodic exhaust pipeline. The air main pipeline is connected to the first pipeline 11 and the first bypass 12 through a first three-way valve 3. Both the first pipeline 11 and the hydrogen gas pipeline are used to communicate with the anodic inlet of the battery stack 1, and a first stop valve 5 is provided on the hydrogen gas pipeline, and a second stop valve 10 is provided on the first bypass 12; the anodic exhaust pipeline is used to communicate with the anodic outlet of the battery stack, and a third stop valve 8 is provided on the anodic exhaust pipeline; a cathodic gas pipeline, including a second pipeline 13, a second bypass 14 and a cathodic exhaust pipeline. The cathodic inlet pipeline is connected to the second pipeline 13 and the second bypass 14 through a second three-way valve 7. The second pipeline 13 is used to communicate with the cathodic inlet of the battery stack 1; the cathodic exhaust pipeline is used to communicate with the cathodic outlet of the battery stack 1. The second bypass 14 and the cathodic exhaust pipeline are connected to the main exhaust pipeline through a third three-way valve 9;

[0051] A control system, connected to the first three-way valve 3, the second three-way valve 7, the third three-way valve 9, the first stop valve 5, the second stop valve 10 and the third stop valve 8, and controlling the actions of each valve.

[0052] The present invention adopts bypasses, namely the first bypass 11 and the second bypass 14, in both the anodic gas pipeline and the cathodic gas pipeline. In this way, when performing the start-stop durability test, before quickly switching the battery stack 1 from the hydrogen / hydrogen state to the air / air state, a certain flow rate of air can be simultaneously introduced and discharged to the outlet through the first bypass 11 and the second bypass 14, and then the positions of the first three-way valve 3 and the second three-way valve 7 are simultaneously switched, so that a certain flow rate of gas simultaneously enters the anode and cathode of the battery stack 1, ensuring that the gas switching speeds on both the anode and cathode sides of the stack are close to the same, thereby more accurately simulating the normal use of the battery stack 1 and improving the accuracy of the start-stop durability test of the battery stack.

[0053] To ensure the stability of gas flow and avoid backflow, in this embodiment, a check valve 4 is provided on the above-mentioned first pipeline 11, and the check valve 4 is located between the first three-way valve 3 and the anode inlet of the battery stack 1. A check valve 6 is provided on the above-mentioned hydrogen pipeline, and the check valve 6 is located between the first stop valve 5 and the anode inlet of the battery stack 1.

[0054] To better control the intake air flow rate and improve the accuracy of the test, in this embodiment, an air flow meter 2 is provided on the main air path to clarify the intake air flow rate of the air, which is convenient for adjustment and calculation.

[0055] The present invention also provides a method for evaluating the start-stop durability of a fuel cell stack, which uses the device for evaluating the start-stop durability of a fuel cell stack as described above, and connects the battery stack to be tested to the above-mentioned device, including the following steps: See Figure 5 as shown,

[0056] 1) The battery stack 1 stops operating, and the oxygen on the cathode side of the stack is consumed by discharging until the voltage drops to 0V; in this step, the battery stack 1 is in the hydrogen / hydrogen state;

[0057] 2) Open the above-mentioned second stop valve 10, and synchronously adjust the second three-way valve 7 and the third three-way valve 9, so that air passes through the main air path and the first bypass 12 at a first preset flow rate, that is, the air at the first preset flow rate (also called anode air) flows according to Figure 2 the s1 intake route; the air passes through the cathode inlet pipe, the second bypass 14 and the main exhaust pipe at a second preset flow rate, that is, the air at the second preset flow rate (also called cathode air) flows according to Figure 2 the s2 intake route, and the first preset flow rate and the second preset flow rate are different;

[0058] 3) Synchronously adjust the first three-way valve 3, the second three-way valve 7 and the third three-way valve 9, close the second stop valve 10 at the same time, and open the third stop valve 8, so that the air in the main air path enters the battery stack 1 through the first pipeline 11 (see Figure 3 the s3 intake line in), the air at the cathode enters the battery stack 1 through the cathode inlet pipe (see Figure 3 the s4 intake line in), and then wait for a preset time until the gas flow rate is stable. In this embodiment, the preset time is 1-2 min; this step is to simultaneously introduce air into the cathode and anode of the battery stack to quickly switch the battery stack to the air / air state, set the cooling water temperature of the battery stack 1 to 25 °C, the dew point of the air to 23 °C and the temperature to 30 °C, and wait for 5 min to make each parameter reach the corresponding set value;

[0059] 4) Monitor the single-cell voltage of the battery stack 1 and reset all parameters to zero; all parameters include the air flow rate, air temperature and air dew point in the main air path;

[0060] 5) Adjust the first three-way valve 3 to connect the main air path with the first bypass 12, open the first stop valve 5, and start the battery stack 1. As shown in Figure 4 , first introduce hydrogen into the anode, i.e., the anode inlet line s5, and then introduce air into the cathode, i.e., the cathode inlet line s6; the battery stack 1 operates to the performance operation judgment point; in this embodiment, the performance operation judgment point is a working point known to those skilled in the art, that is, the moment when the current of the fuel cell is loaded to be constant, and the performance of the fuel cell is stable for a period of time thereafter;

[0061] 6) Determine whether the performance of the battery stack reaches the specified performance attenuation value (in this embodiment, the performance attenuation value is generally 10% of the maximum output voltage, and the maximum is 20% of the maximum output voltage). If so, calculate the start-stop durability of the battery stack. If not, repeat steps 1)-5) until the performance of the battery stack reaches the specified performance attenuation value.

[0062] Before performing the above method, flow matching can be carried out. That is, the calibration process of the second preset flow rate and the first preset flow rate is as follows:

[0063] A. The battery stack 1 shuts down and discharges normally, and maintains the battery stack 1 in the hydrogen / hydrogen state for a certain period of time;

[0064] B. Send air with the first flow rate value into the first bypass 12, and send air with the second flow rate value into the second bypass 14. The first flow rate value is the maximum flow rate of the main air path, that is, the first preset flow rate; the second flow rate value is less than the first flow rate value;

[0065] C. Synchronously adjust the first three-way valve 3, the second three-way valve 7 and the third three-way valve 9, and at the same time close the second stop valve 10 and open the third stop valve 8, so that the air in the main air path enters the battery stack 1 through the first pipeline 11, and the air at the cathode enters the battery stack 1 through the cathode inlet pipe, and then wait for a certain period of time;

[0066] D. Monitor the voltage of the battery stack 1, and repeat steps A-C according to the voltage situation. If the voltage is a positive voltage, increase the magnitude of the second flow rate value. If a negative voltage appears, reduce the magnitude of the second flow rate value; until there is no voltage generated in the battery stack 1, the current second flow rate value is the second preset flow rate.

[0067] Through this flow matching in this embodiment, there are no other interference factors affecting the performance evaluation in the experiment, and the accuracy of the evaluation is improved.

[0068] In this embodiment, a start-stop durability test is carried out on a fuel cell stack with 20 membrane electrodes. The specific working steps are as follows:

[0069] 1) The fuel cell stack 1 shuts down. After normal shutdown and discharging, the hydrogen pressure is set to 50 kPa. After the voltage drops to 0 V, the first three-way valve 3, the second three-way valve 7, and the third three-way valve 9 are all in the bypass state, that is, they are respectively connected to the first bypass 11 and the second bypass 14. The first stop valve 5 and the third stop valve 8 are in the closed state, and the fuel cell stack is maintained in the hydrogen / hydrogen state for one minute;

[0070] 2) Open the second stop valve 10. Through the above calibration process, match the first preset flow rate and the second preset flow rate. In this embodiment, the matched air flow rate of 50 NLPM (i.e., the first preset flow rate) is set to enter the first bypass 11, and the air flow rate of 30 NLPM (i.e., the second preset flow rate) is set to enter the second bypass 14. Wait for the gas flow rate to stabilize; set the cooling water temperature of the fuel cell stack to 25 °C, the dew point of the air to 23 °C, and the temperature to 30 °C. Wait for 5 min to make each parameter reach the corresponding set value;

[0071] 3) At the same time, switch the first three-way valve 3, the second three-way valve 7, and the third three-way valve 9 to the intake state of the fuel cell stack 1. Close the second stop valve 10 and open the third stop valve 8, so that the air at the anode instantaneously changes from the first bypass 12 to flow through the fuel cell stack via the first pipeline 11, and the air at the cathode instantaneously changes from the second bypass 14 to flow through the fuel cell stack via the second pipeline 13, and then wait for 1 min;

[0072] 4) Set the air flow rate to 0, and both the temperature and the dew point are set to 0.

[0073] 5) Switch the first three-way valve 3 to the bypass state, open the first stop valve 5, and start the fuel cell stack according to the strategy of first introducing hydrogen to the anode and then introducing air to the cathode; after the average voltage reaches 0.9 V, slowly load the fuel cell stack to 2 A / cm2 according to the loading strategy. At this current density, the corresponding operating conditions are shown in Table 1 below.

[0074]

[0075]

[0076] Table 1

[0077] 6) Repeat steps 1) to 5) until the performance of the fuel cell stack drops to 90% of the initial performance. After 2000 start-stop cycles, the fuel cell stack drops from the initial average voltage of 0.6 V to 0.54 V. That is, it shows that the start-stop durability of the fuel cell stack is 200 times.

[0078] Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0079] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. An apparatus for evaluating the start-stop durability of a fuel cell stack, characterized in that, Comprising: An anodic pipeline, including a hydrogen pipeline, an air main pipeline, a first pipeline and a first bypass, and an anodic exhaust pipe. The air main pipeline is connected to the first pipeline and the first bypass through a first three-way valve. Both the first pipeline and the hydrogen pipeline are used to communicate with the anodic inlet of the fuel cell stack, and a first stop valve is provided on the hydrogen pipeline, and a second stop valve is provided on the first bypass; the anodic exhaust pipe is used to communicate with the anodic outlet of the fuel cell stack, and a third stop valve is provided on the anodic exhaust pipeline; A cathodic pipeline, including a second pipeline, a second bypass and a cathodic exhaust pipe. The cathodic inlet pipe is connected to the second pipeline and the second bypass through a second three-way valve. The second pipeline is used to communicate with the cathodic inlet of the fuel cell stack; the cathodic exhaust pipe is used to communicate with the cathodic outlet of the fuel cell stack. The second bypass and the cathodic exhaust pipe are connected to the main exhaust pipe through a third three-way valve; A control system, connected to the first three-way valve, the second three-way valve, the third three-way valve, the first stop valve, the second stop valve and the third stop valve, and controlling the actions of each valve.

2. The device for evaluating the start-stop durability of a fuel cell stack according to claim 1, wherein: A check valve is provided on the first pipeline, and the check valve is located between the first three-way valve and the anodic inlet.

3. The device for evaluating the start-stop durability of a fuel cell stack according to claim 1, wherein: A check valve is provided on the hydrogen pipeline, and the check valve is located between the first stop valve and the anodic inlet.

4. The device for evaluating the start-stop durability of a fuel cell stack according to claim 1, characterized in that: An air flow meter is provided on the air main pipeline.

5. A method for evaluating the start-stop durability of a fuel cell stack, characterized in that: Using the device for evaluating the start-stop durability of a fuel cell stack according to any one of claims 1 to 4, comprising the following steps: 1) The fuel cell stack shuts down, and discharges to consume the oxygen on the cathodic side of the stack until the voltage drops to 0V; 2) Open the second stop valve, synchronously adjust the second three-way valve and the third three-way valve, so that air is discharged through the air main pipeline and the first bypass at a first preset flow rate, and air is discharged through the cathodic inlet pipe, the second bypass and the main exhaust pipe at a second preset flow rate. The first preset flow rate and the second preset flow rate are different; 3) Synchronously adjust the first three-way valve, the second three-way valve and the third three-way valve, close the second stop valve at the same time, and open the third stop valve, so that the air in the air main pipeline enters the fuel cell stack through the first pipeline, and the air at the cathode enters the fuel cell stack through the cathodic inlet pipe, and then wait for a preset time; 4) Monitor the single-cell voltage of the fuel cell stack, and reset all parameters to zero; 5) Adjust the first three-way valve to connect the air main pipeline with the first bypass, open the first stop valve, start the fuel cell stack, and the fuel cell stack runs to the performance operation judgment point; 6) Judge whether the performance of the fuel cell stack reaches the specified performance attenuation value. If so, calculate the start-stop durability of the fuel cell stack. If not, repeat steps 1)-5) until the performance of the fuel cell stack reaches the specified performance attenuation value.

6. The method for evaluating the start-stop durability of a fuel cell stack according to claim 5, characterized in that: The calibration process of the second preset flow rate and the first preset flow rate is as follows: A The fuel cell stack shuts down and discharges normally, and maintains the fuel cell stack in the hydrogen / hydrogen state for a certain period of time; B Send air with a first flow rate value into the first bypass, and send air with a second flow rate value into the second bypass. The first flow rate value is the maximum flow rate of the air main pipeline, that is, the first preset flow rate; The second flow rate value is less than the first flow rate value; C Synchronously regulate the first three-way valve, the second three-way valve, and the third three-way valve. Meanwhile, close the second stop valve and open the third stop valve, so that the air in the main air path enters the fuel cell stack through the first pipeline, and the air at the cathode enters the fuel cell stack through the cathode inlet pipe, and then wait for a certain period of time; D Monitor the voltage of the fuel cell stack, and repeat steps A - C according to the voltage situation. If the voltage is a positive voltage, increase the magnitude of the second flow value; if a negative voltage appears, decrease the magnitude of the second flow value; until the fuel cell stack generates no voltage, and the current second flow value is the second preset flow rate.

7. The method for evaluating the start-stop durability of a fuel cell stack according to claim 5, characterized in that: The preset time is 1 - 2 minutes.

8. The method for evaluating the start-stop durability of a fuel cell stack according to claim 5, characterized in that: All the parameters include the air flow rate, air temperature, and air dew point in the main air path.

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