A method and system for rapid testing of fuel cell stack water removal capability

Abstract

The present application relates to a kind of fuel cell stack drainage capacity quick test method and system, the method simulates several extreme working scenarios of fuel cell under actual application scene, designs different severity of start mode, and in different start mode, different loading rate is used to its severity grading, whether the start strategy of different severity grade is judged, fuel cell is started successfully, and the drainage capacity of the measured stack is quickly evaluated;The start mode includes normal temperature start, hot engine start after emergency stop and cold engine start after emergency stop.Compared with prior art, the present application has advantages such as high testing efficiency, and can realize the quick screening of fuel cell stack structure design, material selection and process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fuel cells, in particular to a fuel cell stack drainage capacity rapid test method and system. BACKGROUND

[0002] In the field of fuel cells, water management of proton exchange membrane fuel cells is the basis for ensuring the normal operation of fuel cells. There are seven forms of water transfer inside the fuel cell, which are water generated by cathode reaction, water carried out by air flow, water diffused from cathode to anode, air humidification, hydrogen humidification and water carried out by circulating hydrogen water separator. Through reasonable operating conditions and control strategies, healthy water management is an important prerequisite for high performance and long life of fuel cells. Poor water management generally leads to dry or flooded fuel cell membranes. Among them, flooding is a common problem in PEMFC operation. With the increase of reaction gas humidity, platinum dissolution and precipitation and carbon carrier corrosion will accelerate. In addition, if too much liquid water is not discharged in time, it will block the flow and mass transfer channels of the catalyst layer and the diffusion layer, and immediately lead to insufficient gas of reactants, which not only affects the power output of the fuel cell, but also leads to the acceleration of degradation of the catalyst carrier.

[0003] In the application scenario of vehicle fuel cells, some extreme conditions will also occur, for example, the vehicle stops suddenly due to abnormal operation, at this time the fuel cell may stop from high power output state, and the sudden stop of the vehicle leads to no execution of the purge instruction, and a large amount of liquid water generated by reaction will be retained in the diffusion layer micro-pore structure and the flow channel of the bipolar plate, thereby causing the next normal start. The more severe case is that if the abnormal stop cannot be started in time after the purge, after a period of time, more liquid water will be condensed and retained in the fuel cell stack after natural cooling, and it will take longer to execute the purge when starting again, which will consume more manpower and material resources and reduce user experience, and even cause the fuel cell to be flooded and unable to start. Therefore, the production of fuel cells needs to evaluate the drainage capacity of the stack, but the existing technology does not consider how to quickly evaluate the drainage capacity of the stack. SUMMARY

[0004] The purpose of the present application is to overcome the defects of the prior art and provide a fuel cell stack drainage capacity rapid test method and system with high test efficiency.

[0005] The purpose of the present application can be achieved by the following technical solutions:

[0006] In one aspect of the present application, a fuel cell stack drainage capacity rapid test method comprises the following steps:

[0007] 1) set the start mode of the fuel cell stack to be tested according to a first preset priority, set the loading rate in the current start mode according to a second preset priority, determine whether the fuel cell stack to be tested is started successfully, if yes, execute step 2), if no, execute step 4);

[0008] 2) set the start mode of a lower priority, set the loading rate in the current start mode according to the second preset priority, execute step 3);

[0009] 3) determine whether the fuel cell stack to be tested is started successfully, if yes, repeat step 2) until the lowest priority is reached, take the evaluation level corresponding to the highest priority as the final test result, if no, execute step 4);

[0010] 4) set the loading rate in the current start mode to a lower priority according to the second preset priority until the fuel cell stack to be tested is started successfully, take the evaluation level corresponding to the start success as the final test result;

[0011] Each of the evaluation levels corresponds to a start mode and a loading rate in the start mode.

[0012] Further, the start modes include normal temperature start, hot engine start after emergency stop and cold engine start after emergency stop, and in the first preset priority, the normal temperature start has the highest priority and the cold engine start after emergency stop has the lowest priority.

[0013] Further, in the second preset priority, the priorities from high to low correspond to the loading rates from large to small.

[0014] Further, the process of the normal temperature start includes:

[0015] After the fuel cell stack to be tested is purged and cooled, circulating water at ≤35℃ is introduced for more than 10 minutes, test parameters are set, after the test conditions are reached, the load instruction is executed according to the current loading rate, the numerical changes of the stack temperature, internal resistance and each section voltage during the start process are recorded, and whether the start is successful is determined.

[0016] Further, the process of the hot engine start after emergency stop includes:

[0017] The fuel cell stack to be tested is loaded to the rated power point according to the normal start mode, and runs continuously for more than 15 minutes, the emergency stop instruction is executed and the purge instruction is not executed, and after standing for at least 5 minutes, the start is restarted, and the circulating water is started at the same time, test parameters are set, after the test conditions are reached, the load instruction is executed according to the current loading rate, the numerical changes of the stack temperature, internal resistance and each section voltage during the start process are recorded, and whether the start is successful is determined.

[0018] Further, the process of the cold engine start after emergency stop includes:

[0019] The fuel cell stack to be tested is loaded to the rated power point in the normal starting mode, and is continuously operated for more than 15 minutes, an emergency shutdown instruction is executed, and a purge instruction is not executed, a rapid cooling instruction is started, after the cold machine temperature is reached, the rapid cooling function is turned off, and the starting is restarted, at the same time, the circulating water is started, the test parameters are set, after the test conditions are reached, the pull load instruction is executed at the current loading rate, the changes in the values of the stack temperature, internal resistance and each section voltage during the starting are recorded, and whether the starting is successful is judged;

[0020] Under the rapid cooling instruction, circulating water with a temperature of less than or equal to 35 DEG C is introduced to rapidly cool the fuel cell stack to be tested for more than 15 minutes.

[0021] Further, the method further comprises:

[0022] Based on the test results, the fuel cell stack structure design, material selection and / or process are selected.

[0023] Further, each of the starting modes corresponds to at least three loading rates.

[0024] Another aspect of the present application also provides a fuel cell stack drainage capacity rapid test system, comprising a total controller and an electronic load control device, a state acquisition device, a high-temperature cooling liquid circulating device and a low-temperature cooling liquid circulating device connected with the total controller respectively, when testing, the fuel cell stack to be tested is connected with the electronic load control device, the state acquisition device, the high-temperature cooling liquid circulating device and the low-temperature cooling liquid circulating device respectively, the total controller stores one or more programs, and the one or more programs comprise instructions for executing the fuel cell stack drainage capacity rapid test method as described above.

[0025] Further, the state acquisition device comprises a hydrogen flow meter and an air flow meter.

[0026] Compared with the prior art, the present application has the following advantages:

[0027] (1) The present application simulates several extreme working scenarios of fuel cells in actual application scenarios, designs different starting modes with different severity levels, and uses different loading rates in different starting modes to grade the severity levels, so that the test results of the drainage capacity of the fuel cell stack can be quickly obtained, and the test is accurate and efficient.

[0028] (2) In the test process of cold start after emergency stop, the present application designs a rapid cooling mode, greatly shortens the test period of cold start after emergency stop, and improves the test efficiency.

[0029] (3) The present application can quickly evaluate the drainage capacity of the measured fuel cell stack, facilitate the rapid screening of the fuel cell stack structure design, material selection and process, shorten the development cycle, improve the resource utilization rate, and provide certain guidance for the fuel cell system operating conditions and control strategy. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a structural schematic diagram of the test device provided by the present application;

[0031] Figure 2 is an operation flowchart of the test method of the present application;

[0032] Figure 3 is an operation sequence and determination logic diagram of the test method mentioned in the present application;

[0033] Figure 4 is the test process and determination result of the 01# fuel cell stack in the example;

[0034] Figure 5 is the test process and determination result of the 02# fuel cell stack in the example. DETAILED DESCRIPTION

[0035] The present application will be described in detail below in conjunction with the drawings and specific examples. Note that the following description of the embodiments is merely illustrative in nature, and the present application is not intended to limit the scope of application or its use, and the present application is not limited to the following embodiments.

[0036] The factors affecting the water performance of the fuel cell mainly include three aspects, one is the stack design and the flow channel design of the polar plate; the second is the material properties inside the stack, including the hydrophilic and hydrophobic properties of the polar plate surface, the pore structure and hydrophilic and hydrophobic properties of the membrane electrode diffusion layer, the pore structure and hydrophilic and hydrophobic properties of the catalyst layer and the water transmission channel connected between the layers; the third is the control strategy during the operation of the fuel cell, including the operating temperature, pressure, inlet humidity, load rate, etc. The present application analyzes and designs a rapid test method for the drainage capacity of the fuel cell stack based on the above influencing factors, including the following steps:

[0037] 1) Set the start-up mode of the fuel cell stack to be tested according to the first preset priority, set the load rate under the current start-up mode according to the second preset priority, determine whether the fuel cell stack to be tested starts successfully, if yes, execute step 2), if not, execute step 4);

[0038] 2) Set the start-up mode to be one level lower, set the load rate under the current start-up mode according to the second preset priority, execute step 3);

[0039] 3) judge whether the fuel cell stack to be tested is started successfully, if yes, repeat step 2) until the lowest priority is reached, and the evaluation level corresponding to the highest priority is taken as the final test result, if no, step 4) is performed;

[0040] 4) set the loading rate of the current starting mode to be one priority level lower than the second preset priority level until the fuel cell stack to be tested is started successfully, and the evaluation level corresponding to the starting success is taken as the final test result.

[0041] Specifically, the starting modes designed by the application include normal temperature starting, hot engine starting after emergency stop and cold engine starting after emergency stop, and in the first preset priority level, the priority of the normal temperature starting is the highest, and the priority of the cold engine starting after emergency stop is the lowest. In the second preset priority level, the priority from high to low corresponds to the loading speed from large to small. Each evaluation level corresponds to a starting mode and a loading rate in the starting mode. As shown in Table 1, the application designs three loading speeds in each starting mode, thereby forming the division of nine severity levels, i.e. evaluation levels.

[0042] Table 1: Division of severity levels in three starting modes

[0043]

[0044]

[0045] By the different starting modes and different loading rates, the application simulates several extreme working scenarios of fuel cells in actual application scenarios, and effectively tests the water drainage capacity of the fuel cell stack. The principle of the application scenario simulation is that in the process of rapid loading, a large amount of liquid water is rapidly generated in the fuel cell, thereby blocking the mass transfer channel; in addition, the emergency stop and rapid cooling of the previous time cause a large amount of liquid water to accumulate in the fuel cell, thereby creating a more severe starting scenario.

[0046] The specific operation method of the three different severity levels of starting modes designed by the application is as follows:

[0047] (1) Normal temperature rapid starting

[0048] Test conditions: stack temperature (water inlet) T≤35℃; relative humidity of inlet gas (anode / cathode) RH (hydrogen circulation / 60%); inlet gas metering ratio (hydrogen / air) = 2.5; gas back pressure (anode / cathode) = 50 / 40kPa; anode pulse discharge frequency = 0.1s / 7s;

[0049] Three loading rates: loading at a rate of 7A / 0.1s or 10A / 0.1s or 15A / 0.1s to the rated current density.

[0050] Test procedure: After the stack is purged and cooled, circulating water at ≤35℃ is introduced for more than 10 minutes, the parameters are set according to the specified test conditions, and the load command is executed when the test platform displays that the conditions reach the set values. The changes in the values of the stack temperature, internal resistance and voltages of each section during the starting process are recorded.

[0051] (2) Hot engine start after emergency stop

[0052] Test conditions: stack temperature (water inlet) T = 75℃; relative humidity of inlet gas (anode / cathode) = hydrogen circulation / 60%; gas metering ratio (hydrogen / air) = hydrogen circulation / 2.5; gas back pressure (anode / cathode) = 50 / 40 kPa; anode pulse discharge frequency = 0.1s / 7s;

[0053] Three load rates: 3A / 0.1s, 5A / 0.1s or 7A / 0.1s to the rated current density.

[0054] Test method: The fuel cell is loaded to the rated power point in the normal starting mode, and continuously operated for more than 15 minutes, then the test platform executes the emergency stop command without executing the purging command, and after 5 minutes of standing, the circulating water is started, the parameters are set according to the specified test conditions, and the load command is executed when the test platform displays that the conditions reach the set values. The changes in the values of the stack temperature, internal resistance and voltages of each section during the starting process are recorded.

[0055] (3) Cold engine start after emergency stop

[0056] Test conditions: stack temperature (water inlet) T≤35℃; relative humidity of inlet gas (anode / cathode) = hydrogen circulation / 60%; gas metering ratio (hydrogen / air) = hydrogen circulation / 2.5; gas back pressure (anode / cathode) = 50 / 40 kPa; anode pulse discharge frequency = 0.1s / 7s;

[0057] Three load rates: 3A / 0.1s, 5A / 0.1s or 7A / 0.1s to the rated current density.

[0058] Test method: The fuel cell is loaded to the rated power point in the normal starting mode, and continuously operated for more than 15 minutes, then the test platform executes the emergency stop command without executing the purging, the rapid cooling command is started (circulating water at a temperature of ≤35℃ is introduced to rapidly cool the stack for more than 15 minutes), the rapid cooling function is turned off, the circulating water of the stack is turned on, and the parameters are set according to the specified test conditions. The load command is executed when the test platform displays that the conditions reach the set values. The changes in the values of the stack temperature, internal resistance and voltages of each section during the starting process are recorded.

[0059] The first preset priority and the second preset priority designed according to the present application realize the test starting sequence and the grading logic, as follows:Figure 3 For a new test object, first, A3 is started at normal temperature, if the starting fails, it is downgraded, A2 and A1 are sequentially started, if the starting succeeds, the corresponding severity level is determined; if A3 succeeds, B3 is started after the emergency stop, if B3 fails, it is downgraded, B2 and B1 are sequentially started, if the starting succeeds, the corresponding severity level is determined; if B3 succeeds, C3 is started after the emergency stop, and so on.

[0060] The above test process can be realized by a fuel cell stack drainage capacity rapid test system as shown in the accompanying drawings. Figure 1 The test system comprises a total controller and an electronic load control device 8, a state acquisition device, a high-temperature cooling liquid circulating device 6 and a low-temperature cooling liquid circulating device 7 connected with the total controller respectively, when the test is performed, the fuel cell stack 1 to be tested is connected with the electronic load control device 8, the state acquisition device, the high-temperature cooling liquid circulating device 6 and the low-temperature cooling liquid circulating device 7 respectively, and the total controller executes the fuel cell stack drainage capacity rapid test method. Specifically, the state acquisition device comprises a hydrogen flow meter 2 and an air flow meter 3, and the fuel cell stack 1 to be tested is further connected with an anode tail discharge 4 and a cathode tail discharge 5. In the above system, the high-temperature cooling liquid circulating device 6 and the low-temperature cooling liquid circulating device 7 are used in cooperation to realize rapid cooling, the temperature can be rapidly reduced to below 20℃, and the test efficiency is improved.

[0061] In the experiment of performing the C type emergency stop after the cold start, the low-temperature cooling liquid circulating device 7 provided by the present application is used to rapidly cool the stack, which is beneficial to the rapid condensation of the liquid water in the stack, enhances the severity of the experiment, effectively distinguishes the drainage capacity of the test object, greatly shortens the experimental period, and improves the evaluation efficiency.

[0062] Embodiment

[0063] With reference to Figures 2-3 , the 01# stack and the 02# stack are selected to perform the fuel cell drainage capacity rapid test, and the specific steps include the following steps:

[0064] S0, the test object "01# stack" is correctly connected with the fuel cell test platform according to the requirements. It includes the hydrogen gas inlet and outlet pipeline, the air inlet and outlet pipeline, the cooling liquid inlet and outlet pipeline, the positive and negative electrode electronic load, the stack voltage acquisition line and the single-section voltage inspection needle.

[0065] S1, after the test platform is started, the stack is in the OCV state.

[0066] S2, according to Figure 3 , the test method operation logic provided by the present application, first, the A3 normal temperature rapid load mode is selected, the target loading rate is 150 A / s, and the starting result is as shown in the accompanying drawings. Figure 4The 6 monomer voltage sharply decreased during the rapid current pull-up in the starting process, and the voltage of monomer 2# appeared single low phenomenon, but gradually recovered after the current pull-up to the target value, the whole starting process was successful, and there was no monomer voltage alarm and reverse polarity on the test bench.

[0067] S3、According to Figure 3 the test method operation logic, after completing the verification of A3 level, execute B3 emergency stop after hot engine fast load test.

[0068] S321, first start the test bench, set the response operation parameters, and start the stack to 1200mA cm-2 current density, and stabilize for 30min.

[0069] S322, execute the test bench emergency stop instruction, and do not execute the purge instruction, ensure that a large amount of liquid water generated due to high current density operation is retained in the stack.

[0070] S323, after restarting the test bench, complete the test bench related setting according to the operation conditions described above, and the stack enters OCV state.

[0071] S324, execute B3 starting strategy, target loading rate is 70A / s, and the starting result is shown in Figure 4 During the starting process, the 6 monomer voltage gradually decreased with the pull-up of the current, and the whole process did not appear single low phenomenon and had good consistency, and finally realized successful starting.

[0072] S325, according to Figure 3 the test method operation logic, after completing the verification of B3 level, execute C3 emergency stop after cold engine fast load test.

[0073] S331, first start the test bench, set the response operation parameters, and start the stack to 1200mA cm-2 current density, and stabilize for 30min.

[0074] S332, execute the test bench emergency stop instruction, and do not execute the purge instruction, ensure that a large amount of liquid water generated due to high current density operation is retained in the stack.

[0075] S333, start the fast cooling instruction, open the electromagnetic valve, and pass in 25℃ cooling liquid, through condensation, the gaseous water in the stack is quickly condensed into more liquid water, and the process lasts for more than 30min.

[0076] S334, after the stack is fully cooled to the target temperature, restart the test bench, and complete the test bench related setting according to the operation conditions described above, and the stack enters OCV state.

[0077] S335, execute C3 start strategy, target loading rate is 70A / s, and the start result is as shown in Figure 4 During the start process, the voltages of the six single cells gradually decrease with the increase of the current, and when the current reaches about 150A, the voltages of the single cells 1#, 3#, 4# and 6# sharply decrease, and the voltage of the single cell 1# is lower than 0V, which is the minimum limit of the electronic load voltage, resulting in the test platform being suddenly stopped and the start failing.

[0078] Repeat the steps S331 to S334.

[0079] S335, according to the test method operation logic of Figure 3 , execute C2 start strategy, and the target loading rate is 50A / s.

[0080] S336, the start result is as shown in Figure 4 During the start process, the voltages of the six single cells gradually decrease with the increase of the current, and no single cell voltage is lower than the other single cell voltages, and finally the start is successfully realized.

[0081] S337, finally determine that the drainage capacity level of the measured 01# stack is "C2".

[0082] Test the 02# stack according to the same operation steps, and the test process is as shown in Figure 5 , and finally determine that the drainage capacity level of the measured 02# stack is "B2".

[0083] In the embodiment, the 01# and 02# stacks are assembled by using two different structures of flow channels, and it can be considered that the design scheme of the flow channel of the 01# stack is more beneficial to the drainage of the fuel cell.

[0084] The above embodiments are only examples and do not represent the limitation of the scope of the present application. These embodiments can be implemented in other various ways, and various omissions, substitutions and changes can be made without departing from the technical idea of the present application.

Claims

1. A method for rapid testing of fuel cell stack drainability, characterized by, The method comprises the following steps: 1) setting a start mode of the fuel cell stack to be tested according to a first preset priority, setting a loading rate in the current start mode according to a second preset priority, judging whether the fuel cell stack to be tested is started successfully, if yes, executing step 2), if no, executing step 4); 2) setting a start mode of a lower priority, setting a loading rate in the current start mode according to the second preset priority, executing step 3); 3) judging whether the fuel cell stack to be tested is started successfully, if yes, repeatedly executing step 2) until the lowest priority is reached, taking an evaluation grade corresponding to the highest priority as a final test result, if no, executing step 4); 4) setting a loading rate of a lower priority in the current start mode according to the second preset priority until the fuel cell stack to be tested is started successfully, taking an evaluation grade corresponding to the start success as the final test result; Each of the evaluation grades corresponds to a start mode and a loading rate in the start mode; The start modes comprise a normal temperature start, a hot engine start after an emergency stop and a cold engine start after an emergency stop, and in the first preset priority, the normal temperature start has the highest priority and the cold engine start after an emergency stop has the lowest priority.

2. The rapid test method for drainability of a fuel cell stack according to claim 1, characterized by, In the second preset priority, the priorities are from high to low according to the loading rates from large to small.

3. The rapid test method for drainability of a fuel cell stack according to claim 1, characterized by, The process of the normal temperature start comprises: After the fuel cell stack to be tested is purged and cooled, circulating water with a temperature of ≤35℃ is introduced for more than 10 minutes, test parameters are set, after the test conditions are reached, a load instruction is executed at the current loading rate, the changes of the values of the stack temperature, internal resistance and each section voltage in the start process are recorded, and whether the start is successful is judged.

4. The rapid test method for drainability of a fuel cell stack according to claim 1, characterized by, The process of the hot engine start after an emergency stop comprises: The fuel cell stack to be tested is loaded to a rated power point according to a normal start mode, is continuously operated for more than 15 minutes, an emergency stop instruction is executed and a purge instruction is not executed, is statically placed for at least 5 minutes, is restarted, circulating water is started at the same time, test parameters are set, after the test conditions are reached, a load instruction is executed at the current loading rate, the changes of the values of the stack temperature, internal resistance and each section voltage in the start process are recorded, and whether the start is successful is judged.

5. The rapid test method for drainability of a fuel cell stack according to claim 1, characterized by, The process of the cold engine start after an emergency stop comprises: The fuel cell stack to be tested is loaded to a rated power point according to a normal start mode, is continuously operated for more than 15 minutes, an emergency stop instruction is executed and a purge instruction is not executed, a rapid cooling instruction is started, after the cold engine temperature is reached, the rapid cooling function is turned off, is restarted, circulating water is started at the same time, test parameters are set, after the test conditions are reached, a load instruction is executed at the current loading rate, the changes of the values of the stack temperature, internal resistance and each section voltage in the start process are recorded, and whether the start is successful is judged. Under the rapid cooling instruction, circulating water with a temperature of ≤35℃ is introduced to rapidly cool the fuel cell stack to be tested for more than 15 minutes.

6. The rapid test method for drainability of a fuel cell stack according to claim 1, characterized by, The method further comprises: Based on the test result, the structure design, material selection and / or process of the fuel cell stack are selected.

7. The rapid test method for drainability of a fuel cell stack according to claim 1, characterized by, Each of the start modes corresponds to at least three loading rates.

8. A rapid test system for water removal capability of a fuel cell stack, characterized by, The test system comprises a general controller and an electronic load control device, a state acquisition device, a high-temperature coolant circulation device and a low-temperature coolant circulation device connected to the general controller respectively, and the fuel cell stack to be tested is connected to the electronic load control device, the state acquisition device, the high-temperature coolant circulation device and the low-temperature coolant circulation device respectively during the test, the general controller stores one or more programs, and the one or more programs comprise instructions for executing the method for rapidly testing the water removal capacity of the fuel cell stack according to any one of claims 1-7.

9. The rapid fuel cell stack drainability test system of claim 8, wherein, The state acquisition device comprises a hydrogen flow meter and an air flow meter.

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