Method for evaluating nitrogen tolerance of a fuel cell

Abstract

The application relates to a fuel cell nitrogen tolerance evaluation method, which comprises the following steps: S1, connecting a fuel cell to a test platform and setting test working condition conditions; S2, using pure hydrogen and air as fuel to test the polarization performance of the fuel cell as an initial reference index; S3, mixing different proportions of nitrogen into the pure hydrogen respectively, testing the nitrogen sensitivity of the fuel cell under the same working condition conditions, and obtaining a battery performance and nitrogen concentration relationship curve under different current working conditions; S4, using pure hydrogen to test the polarization performance of the fuel cell, and drawing an initial polarization curve and a final polarization curve comparison graph; S5, according to S3, the percentage of the change of the battery performance under different nitrogen concentrations is obtained, according to S4, the change of the battery performance after the fuel cell is subjected to a certain time and a certain concentration of nitrogen sensitivity test is obtained, and the nitrogen tolerance of the fuel cell is analyzed and evaluated. Compared with the prior art, the application has the advantages of convenient operation and high applicability.

Description

Technical Field

[0001] This invention relates to the field of fuel cell testing technology, and in particular to a method for evaluating the nitrogen tolerance of fuel cells. Background Technology

[0002] Fuel cells directly convert the chemical energy of fuel into electrical energy, resulting in high energy conversion efficiency. They operate without pollution or noise, making them the most promising power generation technology from the perspective of energy conservation and environmental protection.

[0003] Although the fuel cell industry has been developing for many years, numerous factors still hinder its commercialization. Fuel cells experience various performance issues during vehicle operation, such as low performance of individual cells and a rapid decline in overall cell performance. The reasons for this performance degradation are multifaceted. Research has revealed that a decrease in hydrogen concentration, particularly the introduction of nitrogen into the hydrogen, can cause unseen changes in fuel cell performance.

[0004] Currently, there is limited research on the nitrogen tolerance performance of fuel cells. Most studies on fuel cell performance focus on the sensitivity of the cell to changes in parameters such as the temperature, pressure, and metering ratio of the inlet and outlet gases and coolant, without considering the impact of nitrogen tolerance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art by providing a method for evaluating the nitrogen tolerance of fuel cells.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] This invention provides a method for evaluating the nitrogen tolerance of fuel cells, the method comprising the following steps:

[0008] Step S1: Connect the fuel cell to the test bench and set the test conditions.

[0009] Step S2: Using pure hydrogen and air as fuel, test the polarization performance of the fuel cell as an initial reference indicator;

[0010] Step S3: Mix nitrogen gas in pure hydrogen gas in different proportions, test the sensitivity of fuel cell to nitrogen gas under the same operating conditions, and obtain the relationship curve between battery performance and nitrogen concentration under different current conditions.

[0011] Step S4: Test the polarization performance of the fuel cell again with pure hydrogen and compare it with the initial reference index. Plot a comparison graph of the initial polarization curve and the final polarization curve.

[0012] Step S5: Based on step S3, obtain the percentage change in battery performance under different nitrogen concentrations. Based on step S4, obtain the change in battery performance after the fuel cell has undergone a nitrogen sensitivity test for a certain time and a certain concentration, thereby analyzing and evaluating the nitrogen tolerance of the fuel cell.

[0013] Preferably, step S1 specifically comprises:

[0014] The test bench is equipped with independent mass flow control units for hydrogen, air and nitrogen to control the flow rate of the gas entering the fuel cell stack.

[0015] Connect the fuel cell to the test bench, connect the anode chamber to the hydrogen pipeline, and connect the cathode chamber to the air pipeline. Set the gas temperature, stack temperature, humidity, gas pressure, anode metering ratio, and cathode metering ratio respectively.

[0016] Preferably, the gas temperature and fuel cell stack temperature are set to 60-75°C, the humidity to 30-60%, the gas pressure to 50-150 kPag, the anode metering ratio to 1.5-2.5, and the cathode metering ratio to 1.5-5.

[0017] Preferably, the nitrogen in step S3 is set as follows: while keeping the hydrogen mass flow rate constant, the mass flow rate of the incoming nitrogen is controlled so that the standard gas flow rate ratio of nitrogen in the mixed gas reaches a set ratio.

[0018] Preferably, the nitrogen in step S3 is set as follows: keeping the standard gas flow rate of the mixed gas constant, reducing the mass flow rate of hydrogen proportionally, and increasing the mass flow rate of nitrogen, so that the standard gas flow rate ratio of nitrogen in the mixed gas reaches the set ratio.

[0019] Preferably, the set ratios are 0%, 5%, 10%, 15%, and 20% in sequence.

[0020] Preferably, the different current conditions in step S3 are as follows: starting from 0A, gradually loading to 50A, 250A, 400A, 500A and 650A at a set loading speed.

[0021] Preferably, step S3 further includes balancing the set duration after the set operating conditions are loaded.

[0022] Preferably, the balancing time is 10 minutes.

[0023] Preferably, step S5 specifically comprises:

[0024] Let the performance of a fuel cell under different nitrogen concentrations and different currents be expressed by voltage. The initial polarization performance in high-purity hydrogen is expressed as follows: The final polarization performance is expressed as ;in, For current;

[0025] Then, based on step S3, the percentage change in battery performance under different nitrogen concentrations is obtained:

[0026]

[0027] Based on step S4, the changes in fuel cell performance after undergoing a nitrogen sensitivity test for a certain time and concentration are as follows:

[0028]

[0029] The nitrogen tolerance of fuel cells was analyzed and evaluated.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] 1) The method for evaluating the nitrogen tolerance of fuel cells provided by this invention can effectively evaluate the tolerance of fuel cells in a nitrogen environment. The method is simple and convenient to operate, has high applicability, and is of great value to the research on nitrogen tolerance of fuel cells.

[0032] 2) In the early stages of fuel cell development, research on the battery's tolerance to nitrogen can improve the product or control the quality requirements of hydrogen at the system level.

[0033] 3) Based on the working principle of this invention, it can be extended to the tolerance of fuel cells to other gases. Attached Figure Description

[0034] Figure 1 This is a flowchart of the method of the present invention;

[0035] Figure 2 The graph shows the relationship between battery performance and nitrogen concentration under a 400A current condition.

[0036] Figure 3 These are the initial and final polarization performance curves of the fuel cell. Detailed Implementation

[0037] 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, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0038] Example

[0039] This embodiment provides a method for evaluating the nitrogen tolerance of a fuel cell, which includes the following steps:

[0040] S1: Connect the fuel cell to the test bench, connect the anode chamber to the hydrogen pipeline, and connect the cathode chamber to the air pipeline; set the gas temperature and stack temperature to 60-75℃, the humidity to 30-60%, the gas pressure to 50-150kPag, the anode metering ratio to 1.5-2.5, and the cathode metering ratio to 1.5-5.

[0041] S2: 99.999% high-purity hydrogen is introduced into the hydrogen pipeline, and purified compressed air is introduced into the air pipeline. Then, the fuel cell is operated according to the set operating conditions. The current of the fuel cell stack is controlled to be gradually increased from 0A to 50A, 250A, 400A, 500A and 650A at a loading rate of 10A / s, and stabilized for 10-20 minutes at each current density to obtain the polarization performance of the fuel cell under standard operating conditions.

[0042] S3: Introduce 99.99% pure nitrogen into the nitrogen pipeline, and merge the nitrogen pipeline with the hydrogen pipeline before entering the humidification unit. The hydrogen and nitrogen are fully mixed in the humidification unit and enter the stack after reaching the same target humidity. Under the same operating conditions, perform sensitivity tests with nitrogen flow rates of 5%, 10%, 15%, and 20% in sequence, and balance for 10-20 minutes at each current density. Plot the relationship between battery performance and nitrogen concentration under different current conditions.

[0043] The test bench should have independent mass flow control units for hydrogen, air and nitrogen, which can control the flow rate of the gas entering the fuel cell stack separately;

[0044] The humidification unit has a large humidification tank volume, and the gas pipe diameter for the mixed gas entering and exiting the humidification tank is relatively small, which can ensure that hydrogen and nitrogen are fully mixed.

[0045] The standard gas flow rate ratio of nitrogen in the gas mixture can be achieved in two ways: 1. Keep the hydrogen mass flow rate constant and control the incoming nitrogen mass flow rate to achieve a standard gas flow rate ratio of 0%, 5%, 10%, 15%, and 20%; 2. Keep the standard gas flow rate of the gas mixture constant and proportionally reduce the hydrogen mass flow rate while increasing the nitrogen mass flow rate to achieve a standard gas flow rate ratio of 0%, 5%, 10%, 15%, and 20%.

[0046] S4: After completing the sensitivity tests under different nitrogen concentrations, the polarization performance of the fuel cell under standard operating conditions was tested again with high-purity hydrogen, and compared with the initial polarization performance. A comparison graph of the initial polarization curve and the final polarization curve was plotted.

[0047] S5: Let the battery performance of the fuel cell under different nitrogen concentrations and different currents be represented by voltage. The initial polarization performance in high-purity hydrogen is expressed as follows: The final polarization performance is expressed as Based on S3, the percentage change in battery performance under different nitrogen concentrations can be obtained. According to S4, the changes in fuel cell performance after undergoing a certain period of time and a certain concentration of nitrogen sensitivity test can be determined. Based on the above results, the nitrogen tolerance of fuel cells can be analyzed and evaluated.

[0048] The present invention will now be described in conjunction with the accompanying drawings and specific embodiments.

[0049] The fuel cell stack under test was connected to the test bench. The gas and stack temperatures were set to 70°C, humidity to 40%, gas pressure to 100 kPag, anode metering ratio to 1.8, and cathode metering ratio to 2.5. The initial polarization performance of the fuel cell was tested using high-purity hydrogen and air. The current was gradually increased from 0A to 50A, 250A, 400A, 500A, and 650A at a rate of 10A / s, and stabilized for 10 minutes at each current density.

[0050] After the initial polarization test, the load was reduced to 50A, maintaining a hydrogen mass flow rate of 300 NLPM and a nitrogen mass flow rate of 0 NLPM, and balancing for 10 minutes. To ensure the total flow rate is not less than 300 NLPM, the incoming nitrogen mass flow rate was first controlled at 15 NLPM, and then the hydrogen mass flow rate was adjusted to 285 NLPM, so that the nitrogen flow rate in the mixture reached 5%, and balancing for 10 minutes. Similarly, the incoming nitrogen mass flow rate was controlled sequentially at 30 NLPM, 45 NLPM, and 60 NLPM, and then the hydrogen mass flow rate was adjusted to 270 NLPM, 255 NLPM, and 240 NLPM, so that the nitrogen flow rate in the mixture reached 10%, 15%, and 20%, respectively, and balancing for 10 minutes each time. After completion, to ensure the total flow rate is not less than 300 NLPM, the incoming hydrogen mass flow rate was first controlled at 300 NLPM, and then the nitrogen mass flow rate was adjusted to 0 NLPM, restoring the initial state. Similarly, sensitivity tests were performed sequentially at different nitrogen concentrations of 250A, 400A, 500A, and 650A. A graph showing the relationship between battery performance and nitrogen concentration under different current conditions was plotted, as shown below. Figure 2 The figure shown is a curve under a current condition of 400A.

[0051] After the sensitivity test was completed, the polarization performance of the fuel cell under standard operating conditions was tested again using high-purity hydrogen, and compared with the initial polarization performance. A comparison graph of the initial polarization curve and the final polarization curve was plotted. Figure 3The figure shows the initial and final polarization performance curves of the fuel cell.

[0052] according to and This method can calculate the percentage change in fuel cell performance at a 400A current condition under nitrogen concentrations of 20% and 0%, as well as the change in final polarization performance. When different fuel cells are tested using the same method, the nitrogen tolerance of the fuel cells can be further evaluated.

[0053] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for evaluating the nitrogen tolerance of a fuel cell, characterized in that, The method includes the following steps: Step S1: Connect the fuel cell to the test bench and set the test conditions. Step S2: Using pure hydrogen and air as fuel, test the polarization performance of the fuel cell as an initial reference indicator; Step S3: Mix nitrogen gas in pure hydrogen gas in different proportions, test the sensitivity of fuel cell to nitrogen gas under the same operating conditions, and obtain the relationship curve between battery performance and nitrogen concentration under different current conditions. Step S4: Test the polarization performance of the fuel cell again with pure hydrogen and compare it with the initial reference index. Plot a comparison graph of the initial polarization curve and the final polarization curve. Step S5: Based on step S3, obtain the percentage change in battery performance under different nitrogen concentrations. Based on step S4, obtain the change in battery performance after the fuel cell has undergone a nitrogen sensitivity test for a certain time and concentration, thereby analyzing and evaluating the nitrogen tolerance of the fuel cell. Among them, the battery performance of the fuel cell under different nitrogen concentrations and different currents is defined by voltage. The initial polarization performance in high-purity hydrogen is expressed as follows: , Given the current, the percentage change in battery performance under different nitrogen concentrations is obtained according to step S3: 。 2. The method for evaluating the nitrogen tolerance of a fuel cell according to claim 1, characterized in that, Step S1 specifically involves: The test bench is equipped with independent mass flow control units for hydrogen, air and nitrogen to control the flow rate of the gas entering the fuel cell stack. Connect the fuel cell to the test bench, connect the anode chamber to the hydrogen pipeline, and connect the cathode chamber to the air pipeline. Set the gas temperature, stack temperature, humidity, gas pressure, anode metering ratio, and cathode metering ratio respectively.

3. The method for evaluating the nitrogen tolerance of a fuel cell according to claim 2, characterized in that, The gas temperature and fuel cell stack temperature are set at 60-75℃, the humidity at 30-60%, the gas pressure at 50-150kPag, the anode metering ratio at 1.5-2.5, and the cathode metering ratio at 1.5-5.

4. The method for evaluating the nitrogen tolerance of a fuel cell according to claim 1, characterized in that, In step S3, the nitrogen ratio is set as follows: while keeping the hydrogen mass flow rate constant, the incoming nitrogen mass flow rate is controlled so that the nitrogen-to-standard gas flow rate ratio in the mixed gas reaches the set ratio.

5. The method for evaluating the nitrogen tolerance of a fuel cell according to claim 1, characterized in that, In step S3, the nitrogen ratio is set as follows: the standard gas flow rate of the mixed gas is kept constant, the hydrogen mass flow rate is reduced proportionally, and the nitrogen mass flow rate is increased, so that the standard gas flow rate ratio of nitrogen in the mixed gas reaches the set ratio.

6. A method for evaluating the nitrogen tolerance of a fuel cell according to claim 4 or 5, characterized in that, The set ratios are 0%, 5%, 10%, 15%, and 20% respectively.

7. The method for evaluating the nitrogen tolerance of a fuel cell according to claim 1, characterized in that, The specific steps in step S3 for different current conditions are as follows: starting from 0A, gradually increasing the current to 50A, 250A, 400A, 500A and 650A at a set loading speed.

8. The method for evaluating the nitrogen tolerance of a fuel cell according to claim 1, characterized in that, Step S3 also includes balancing the set duration after the set operating conditions are loaded.

9. The method for evaluating the nitrogen tolerance of a fuel cell according to claim 8, characterized in that, The balancing time is 10 minutes.

10. The method for evaluating the nitrogen tolerance of a fuel cell according to claim 1, characterized in that, In step S5, step S4 yields the change in fuel cell performance after undergoing a nitrogen sensitivity test for a certain time and concentration, expressed as: In the formula: For the final polarization performance.

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