Periodic hydrogen flow switching system and method based on fuel cell

Abstract

The invention provides a periodic hydrogen flow switching system and method based on a fuel cell. The system comprises a hydrogen source; the fuel cell stack comprises two hydrogen ports, and when one hydrogen port is a hydrogen inlet, the other hydrogen port is a hydrogen outlet; the executing mechanism is used for changing the gas path direction of hydrogen entering the fuel cell stack and is connected with the hydrogen source and the two hydrogen ports of the fuel cell stack; and the control system is in signal connection with the fuel cell stack and the execution mechanism. The direction of a reactant gas path of the fuel cell can be adjusted, so that an inlet and an outlet of the fuel cell stack are interchangeable.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and particularly relates to a periodic hydrogen gas flow switching system and method based on a fuel cell. Background Art

[0002] In the existing fuel cell technology, problems such as water management, reactant uniformity, local overheating, system durability, and dynamic response performance have always been urgent problems to be solved. At present, most fuel cells adopt a fixed gas flow direction, which easily leads to water accumulation problems. Moisture will continuously accumulate at specific positions in the fuel cell stack along the gas flow direction, affecting the water management efficiency of the battery and thus reducing the performance. At the same time, the fixed gas flow direction causes uneven distribution of reactants in the fuel cell stack. In some areas, problems such as accelerated aging may occur due to gas starvation, such as increased bipolar plate corrosion and oxidation, increased ohmic impedance, and enhanced Ostwald ripening effect of the membrane electrode. In some areas, problems such as channel blockage and increased mass transfer loss may occur due to flooding, and the catalytic efficiency of the membrane electrode may decrease due to the coverage of catalytic active sites, greatly affecting the overall reaction efficiency of the fuel cell and the performance of the fuel cell stack. In addition, this fixed gas flow will also cause local overheating phenomena, accelerate material aging, reduce the durability of the fuel cell, and pose safety hazards. In long-term use, the fixed gas flow direction will also make the materials in some parts more prone to fatigue, reducing the durability and reliability of the system. In the face of rapidly changing operating conditions, the existing fuel cells have insufficient dynamic response performance and are difficult to adapt to complex operating environments. Summary of the Invention

[0003] The purpose of the present invention is to provide a periodic hydrogen gas flow switching system and method based on a fuel cell. By using a two-way three-way valve or a two-way five-way valve to adjust the gas path direction of the fuel cell reactants, the inlet and outlet of the fuel cell stack are interchanged according to a certain rule, so that the flow and reaction process of the reactants present a change form similar to alternating current, in order to solve the problems in the prior art. The adopted technical solutions are as follows:

[0004] A periodic hydrogen gas flow switching system based on a fuel cell, comprising:

[0005] A hydrogen source;

[0006] A fuel cell stack, including two hydrogen ports. When one hydrogen port is a hydrogen inlet, the other hydrogen port is a hydrogen outlet;

[0007] An actuator for changing the gas path direction of hydrogen entering the fuel cell stack, which is connected to the hydrogen source and the two hydrogen ports of the fuel cell stack;

[0008] And a control system, which is signal-connected to both the fuel cell stack and the actuator.

[0009] Preferably, the actuator includes two two-way three-way valves; when one of the two-way three-way valves is connected to a hydrogen source and a hydrogen port, the other two-way three-way valve is connected to the other hydrogen port.

[0010] Preferably, the actuator is a two-way five-way valve.

[0011] Preferably, it further includes a monitoring unit signal-connected to the control system, which is used to obtain the output current, output voltage, internal temperature, gas temperature and pressure at two hydrogen ports of the fuel cell stack.

[0012] A periodic hydrogen gas flow switching method based on a fuel cell, based on the periodic hydrogen gas flow switching system based on the fuel cell, includes the following steps:

[0013] Collect the output current and output voltage of the fuel cell stack;

[0014] Calculate the output power according to the collected output current and output voltage, and classify the power demand situation in the application scenario;

[0015] Based on the obtained classification, the control system makes a decision to determine the switching rule and frequency of the actuator;

[0016] The actuator performs a switching action according to the signal to realize the periodic interchange of the inlet and outlet of the fuel cell stack.

[0017] Compared with the prior art, the advantages of the present invention are:

[0018] 1. Optimize water management

[0019] By periodically switching the direction of the hydrogen gas path of the fuel cell, the phenomenon of water accumulation is effectively reduced. Compared with a fuel cell with a traditional fixed gas flow direction, the present invention avoids the continuous accumulation of moisture in some areas, significantly improving the water management efficiency of the battery. This helps to maintain a good working environment inside the fuel cell, ensure the stable progress of the electrochemical reaction, and thus improve the overall performance.

[0020] 2. Improve the uniformity of reactants

[0021] Make the distribution of reactants in the fuel cell stack more uniform, overcoming the problems of excessive or insufficient reaction in some areas in the prior art. The present invention ensures that the reactions in each area can proceed fully and evenly, thereby greatly improving the overall reaction efficiency of the fuel cell and the performance of the fuel cell stack. This not only improves the energy conversion efficiency but also extends the service life of the fuel cell.

[0022] 3. Alleviate local overheating

[0023] The periodic change in the direction of the gas flow helps to balance the temperature distribution within the stack, effectively reducing the phenomenon of local overheating. Compared with traditional fuel cells, the present invention reduces the material aging rate caused by local overheating, extends the service life of the fuel cell, and at the same time improves the stability and safety of the system. It can better adapt to different working environments and load changes.

[0024] 4. Enhance system durability

[0025] It reduces the fatigue effect of the materials in certain parts after long-term use. Through the periodic gas flow switching, the present invention makes the stress distribution inside the fuel cell stack more uniform, thereby enhancing the durability and reliability of the fuel cell stack. It reduces the maintenance cost and the risk of failure, and improves the overall service life of the system.

[0026] 5. Improve dynamic response performance

[0027] Under rapidly changing operating conditions, the present invention can provide better dynamic response performance and adapt to complex operating environments. It performs particularly well in aviation and other application scenarios with high-speed changes, and can quickly adjust the reaction state to meet the needs of different load changes. Compared with the prior art, it has higher flexibility and adaptability. Description of the Drawings

[0028] Figure 1 It is a flowchart of a periodic hydrogen gas flow switching method based on a fuel cell;

[0029] Figures 2(a) to 2(b) It is a diagram of different states of a periodic hydrogen gas flow switching system based on a fuel cell using a two-way three-way valve as an actuator;

[0030] Figures 3(a) to 3(b) It is a diagram of different states of a periodic hydrogen gas flow switching system based on a fuel cell using a two-way five-way valve as an actuator. Detailed Embodiment

[0031] The following will describe in more detail the periodic hydrogen gas flow switching system and method based on a fuel cell of the present invention with reference to the schematic diagrams, which show the preferred embodiments of the present invention. It should be understood that those skilled in the art can modify the present invention described herein while still achieving the advantageous effects of the present invention. Therefore, the following description should be understood as a broad guidance for those skilled in the art and not as a limitation to the present invention.

[0032] A periodic hydrogen gas flow switching system based on a fuel cell includes:

[0033] A hydrogen gas source, which is a hydrogen cylinder.

[0034] A fuel cell stack includes two hydrogen ports. When one hydrogen port is the hydrogen inlet, the other hydrogen port is the hydrogen outlet.

[0035] An actuator is used to change the gas path direction of hydrogen entering the fuel cell stack, and it is connected to the two hydrogen ports of the hydrogen source and the fuel cell stack.

[0036] Specifically, the actuator is connected to the hydrogen source and between the two hydrogen ports through gas pipelines.

[0037] A control system is signal-connected to both the fuel cell stack and the actuator; it receives the feedback signal of the fuel cell stack and sends a control signal to the actuator.

[0038] And a monitoring unit is used to obtain the output current, output voltage, internal temperature, gas temperature and pressure at the two hydrogen ports of the fuel cell stack. The monitoring unit is signal-connected to the control system.

[0039] Such as Figures 2(a) to 2(b) , the actuator includes 2 two-position three-way valves, and the 2 two-position three-way valves are integrated.

[0040] When one two-position three-way valve is connected to the hydrogen source and one hydrogen port, the other two-position three-way valve is connected to the other hydrogen port.

[0041] Such as Figures 3(a) to 3(b) , the actuator is 1 two-position five-way valve.

[0042] In this embodiment, the monitoring unit includes:

[0043] A current sensor, which is arranged between the fuel cell stack and the load;

[0044] A voltage sensor, which is arranged between the fuel cell stack and the load;

[0045] A temperature sensor, which is respectively arranged at the hydrogen inlet of the fuel cell stack, the hydrogen outlet of the fuel cell stack and inside the fuel cell stack; the temperatures at these three places play a great role in characterizing the performance of the fuel cell.

[0046] A pressure sensor, which is arranged at the hydrogen inlet and the hydrogen outlet of the fuel cell stack;

[0047] The control system is used for data acquisition and monitoring, classifying according to power demand, determining the switching rules and frequencies of the two-position three-way valve or the two-position five-way valve, sending switching signals to the electromagnetic two-position three-way valve or the two-position five-way valve to realize the periodic interchange of the inlet and outlet of the fuel cell stack, and performing performance evaluation, adjustment and optimization to adapt to different working conditions.

[0048] The working principle of the periodic hydrogen gas flow switching system based on the fuel cell:

[0049] S1: System initialization

[0050] Install and connect the fuel cell stack, electromagnetic two-way three-way valve or two-way five-way valve, gas pipeline, control system, and various sensors and measuring devices;

[0051] Among them, the measuring device refers to other parameters that need to be characterized and measured. For example, since multi-stage pressure relief is required from the hydrogen cylinder to the fuel cell stack, a flow meter and a pressure sensor are provided at the outlet of the hydrogen cylinder.

[0052] Perform initialization settings on the control system, including setting the timer and determining parameters such as the initial switching rule and frequency;

[0053] At the same time, check whether the components such as the electrodes and electrolyte of the fuel cell stack are normal, and whether the gas pipeline connections are firm and leak-free.

[0054] S2: Data acquisition and monitoring

[0055] Continuously collect the output current I fc and output voltage U fc ;

[0056] Temperature (including the internal temperature T st of the fuel cell stack, the gas temperature T in at the inlet, and the gas temperature T out at the outlet, etc.);

[0057] Gas pressure (the gas pressure P in at the inlet and the gas pressure P out ) at the outlet;

[0058] Use sensors to monitor parameters such as the temperature, humidity, and gas pressure of the external working environment, and transmit the collected data to the control system in real time for analysis and decision-making.

[0059] S3: Classification according to power demand

[0060] Based on the collected output current I fc and output voltage U fc calculate the output power and classify the power demand situation in the application scenario.

[0061] Since the gas flow consumption in the fuel cell stack is different under different power demands, the power demands are divided into different levels of low, medium, and high ranges.

[0062] S4: Control system decision-making

[0063] Based on the obtained classification, the control system makes a decision to determine the switching rule and frequency of the two-way three-way valve / two-way five-way valve.

[0064] That is, the control system makes decisions based on the classified power demand situation, determines the switching rules and frequencies of the electromagnetic two-way three-way valve / two-way five-way valve, and sends switching signals to the electromagnetic two-way three-way valve / two-way five-way valve to achieve the periodic interchange of the inlet and outlet of the fuel cell stack.

[0065] For example, a lower switching frequency is selected under low power demand and low ambient temperature conditions, while the switching frequency is increased under high power demand and high ambient temperature conditions. The specific steps are as follows:

[0066] 1. Calculate the required power of the fuel cell based on the measured voltage and current data of the load. According to the operating current density of the fuel cell or the voltage of a single fuel cell, the required power is divided into different grade ranges including but not limited to low, medium, high, etc. (for example, when the voltage of a single fuel cell is higher than 0.9V, it is a low power demand; when the current density of the fuel cell is lower than the rated current density and the voltage of a single fuel cell is lower than 0.9V, it is a medium power demand; when the current density of the fuel cell is between the rated current density and the peak current density, it is a high power demand);

[0067] 2. Set different switching frequencies, for example, 0.1Hz, 0.05Hz, 0.02Hz, etc.;

[0068] 3. Fix the switching frequency, change the operating conditions of the fuel cell stack by setting different load demands, and collect the temperature and pressure information of the fuel cell stack at these moments, as well as the maximum output power that the polarization curve of the fuel cell can reach, etc.;

[0069] 4. Set the switching frequency as the predicted output variable, and use other information, including power demand, three temperatures of the stack, and two pressures of the stack, as input variables to train the established machine learning model.

[0070] Here, regression algorithms such as Random Forest (RF), Extreme Gradient Boosting (XGboost), Elastic Net Regression (ENR), Ridge Regression (RR), etc. can be used, or machine learning algorithms enhanced based on these algorithms, such as the Bagging algorithm, can also be used;

[0071] 5. After pre-training the regression model, input the collected temperature signal of the stack, voltage signal, and temperature and humidity of the external environment as input variables, and the regression model can output a predicted operating frequency;

[0072] 6. According to the prediction results, the switching frequency value obtained under low power demand and low ambient temperature conditions is lower, while the switching frequency obtained under high power demand and high ambient temperature conditions is higher.

[0073] S5: Execution of the switching of the two-way three-way valve / two-way five-way valve

[0074] The control system sends a switching signal to the electromagnetic two-way three-way valve or two-way five-way valve. The electromagnetic two-way three-way valve or two-way five-way valve performs a switching action according to the signal, realizing the periodic interchange of the inlet and outlet of the fuel cell stack, and ensuring that the switching action is accurate and rapid.

[0075] S6: Performance evaluation and adjustment

[0076] Continuously monitor the performance indicators of the fuel cell system, such as output power, temperature distribution, etc. If it is found that the performance does not meet the expectations or abnormal situations occur, the control system adjusts the switching rule and frequency according to the feedback information.

[0077] Among them, the abnormal situation refers to: the operating temperature exceeds the appropriate temperature range of the fuel cell stack, and the voltage of the fuel cell drops under the same current condition, which may be due to the phenomenon of internal flooding or membrane drying in the fuel cell. It is necessary to jointly evaluate the cause of the fault through information such as temperature, pressure, and power.

[0078] S7: Optimization and adaptation to different working conditions

[0079] Accumulate the switching rule and frequency data under different working conditions through continuous experiments and actual operations. Use machine learning algorithms or optimization algorithms to analyze these data, and further optimize the switching strategy to adapt to a wider working environment and working condition changes. For example, in the aviation application scenario, dynamically adjust the switching rule and frequency according to factors such as altitude change and speed change during flight.

[0080] That is, optimization and adaptation to different working conditions is to accumulate the switching rule and frequency data under different working conditions through continuous experiments and actual operations, and use machine learning algorithms or optimization algorithms including but not limited to random forest method, ridge regression, elastic net regression, etc. to analyze these data, and further optimize the switching strategy to adapt to a wider working environment and working condition changes.

[0081] Such as Figure 1 As shown, during operation, a machine learning algorithm has been continuously used to execute the regression model to determine the switching frequency (that is, the step of the control system making decisions and determining the switching rule and frequency); when an abnormality occurs, it indicates that the switching frequency of the fuel cell operating normally predicted by the regression model is actually not appropriate, and this state and error value need to be recorded; and eliminate the abnormality of the fuel cell stack by changing the switching frequency (usually by increasing the switching frequency); after covering the previous predicted frequency with this switching frequency, input it into the regression model; subsequently, when encountering the same input quantities (signals such as temperature, pressure, power, etc.), accurate control signals can be given to optimize the control effect of the control system.

[0082] The above are only the preferred embodiments of the present invention and do not impose any restrictive effect on the present invention. Any person skilled in the art, within the scope of the technical solution of the present invention, makes any form of equivalent substitution or modification and other changes to the technical solution and technical content disclosed by the present invention, which are all within the content of the technical solution of the present invention and still fall within the protection scope of the present invention.

Claims

1. A periodic hydrogen gas flow switching system based on a fuel cell, characterized in that: include: Hydrogen source; A fuel cell stack comprises two hydrogen ports, one of which is a hydrogen inlet and the other is a hydrogen outlet; An actuator, used to change the gas path direction of hydrogen entering the fuel cell stack, which is connected to the hydrogen source and the two hydrogen ports of the fuel cell stack; and a control system, which is signal-connected to the fuel cell stack and the actuator.

2. The periodic hydrogen gas flow switching system based on a fuel cell according to claim 1, characterized in that: The actuator comprises two two-position three-way valves; when one of the two-position three-way valves is connected to a hydrogen source and a hydrogen port, the other two-position three-way valve is connected to the other hydrogen port.

3. The periodic hydrogen gas flow switching system based on a fuel cell according to claim 1, characterized in that: The actuator is a two-position five-way valve.

4. The periodic hydrogen gas flow switching system based on a fuel cell according to claim 1, characterized in that: Further including: The monitoring unit is connected to the control system signal and is used to obtain the output current, output voltage, internal temperature, and gas temperature and pressure at the two hydrogen ports of the fuel cell stack.

5. A periodic hydrogen gas flow switching method based on a fuel cell, based on the periodic hydrogen gas flow switching system based on a fuel cell according to claim 4, characterized in that: The following steps are involved: Collecting the output current and output voltage of the fuel cell stack; Calculate the output power based on the collected output current and output voltage, and classify the power demand in the application scenario; Based on the obtained classification, the control system makes decisions and determines the switching rules and frequencies of the actuators; The actuator performs switching actions according to the signal to achieve periodic interchange of the inlet and outlet of the fuel cell stack.

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