A fuel cell system and water content dynamic adjustment method

Abstract

The application provides a fuel cell system and a water content dynamic adjustment method, and relates to the technical field of fuel cells.The fuel cell system comprises a controller, an electric pile and a current acquisition module, an air path subsystem, a hydrogen path subsystem and a nitrogen path subsystem which are all connected with the electric pile.The electric pile is used for outputting electric current through an electrochemical reaction, the current acquisition module is used for acquiring the output electric current of the electric pile, the air path subsystem is used for providing air to the inside of the electric pile, the hydrogen path subsystem is used for providing hydrogen to the inside of the electric pile, the nitrogen path subsystem is used for adjusting the concentration of air and hydrogen in the inside of the electric pile, and the controller is used for calculating the water content in the inside of the electric pile according to the output electric current of the electric pile and generating an adjustment instruction so as to realize the regulation and control of the air path subsystem, the hydrogen path subsystem and the nitrogen path subsystem.The application solves the problems of insufficient water management, poor system reliability, low energy efficiency utilization rate and high system complexity of the fuel cell system in the prior art.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a fuel cell system and a method for dynamically adjusting water content. Background Technology

[0002] Hydrogen fuel cells, as a highly efficient and zero-emission energy conversion device, have received widespread attention in recent years in fields such as new energy vehicles, portable power generation equipment, and stationary power sources. Among them, proton exchange membrane fuel cells have become one of the mainstream technologies for commercial applications due to their advantages such as low operating temperature, fast start-up, and high power density. However, the stable operation of a fuel cell system is highly dependent on the precise control of its internal hydrothermal management.

[0003] During fuel cell operation, the cathode reaction continuously generates water. If the water production rate is too high or drainage is inadequate, liquid water can easily accumulate in the gas diffusion layer or flow field, causing blockage of gas channels and leading to a "flooding" phenomenon. This results in restricted air transport and a sharp drop in battery performance. Conversely, if water generation is insufficient or dehydration is excessive during operation, it can cause membrane electrolyte dehydration and "membrane dryness," thereby reducing proton conductivity, damaging the membrane structure, and affecting the stability and lifespan of the fuel cell.

[0004] Current fuel cell water management technologies mainly rely on fixed strategies, such as adjusting humidifier temperature and using condensers to remove excess water. They lack dynamic feedback and closed-loop adjustment mechanisms for the actual water content of the battery. Therefore, they cannot respond in a timely manner to changes in water production when faced with different load conditions and environmental changes, resulting in problems such as insufficient water management and poor system reliability.

[0005] Furthermore, the gas exiting the cathode of a fuel cell carries a large amount of waste heat. If it is directly discharged, it will not only waste thermal energy but may also cause thermal shock to the system, reducing overall energy efficiency. Although some existing systems have preheating modules, they are mostly independent heating devices and fail to achieve effective coupling with the recovery and utilization of exhaust gas heat energy, resulting in low energy efficiency and high system complexity. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a fuel cell system and a method for dynamic adjustment of water content. This invention solves the problems of insufficient water management, poor system reliability, low energy efficiency, and high system complexity in the prior art fuel cell system.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] A fuel cell system, comprising:

[0009] The controller, fuel cell stack, and current acquisition modules, air circuit system, hydrogen circuit system, and nitrogen circuit system are all connected to the fuel cell stack.

[0010] The controller is connected to the current acquisition module, the air circuit subsystem, the hydrogen circuit system, and the nitrogen circuit system, respectively.

[0011] The fuel cell stack is used to output current through an electrochemical reaction. The current acquisition module is used to acquire the output current of the fuel cell stack. The air circuit subsystem is used to supply air to the inside of the fuel cell stack. The hydrogen circuit subsystem is used to supply hydrogen to the inside of the fuel cell stack. The nitrogen circuit subsystem is used to adjust the concentration of air and hydrogen inside the fuel cell stack. The controller is used to calculate the water content inside the fuel cell stack based on the output current of the fuel cell stack and generate adjustment commands to achieve the control of the air circuit subsystem, hydrogen circuit system, and nitrogen circuit system.

[0012] Preferably, the air path subsystem includes:

[0013] Air compressor, intercooler, first water flow sensor, heat exchanger, and first tail valve;

[0014] The air compressor and intercooler are connected in sequence. The intercooler is connected to the cathode inlet of the fuel cell stack. The first water flow sensor, heat exchanger and first tail valve are connected in sequence. The first water flow sensor is connected to the cathode outlet of the fuel cell stack.

[0015] The air compressor is used to supply air, the intercooler is used to cool the air at the air compressor outlet, the first water flow sensor is used to monitor the water flow at the cathode outlet of the fuel cell stack, the heat exchanger is used to heat the hydrogen at the anode inlet of the fuel cell stack using the high-temperature gas at the cathode outlet of the fuel cell stack, and the first tail valve is used to discharge unreacted oxygen and nitrogen and regulate the cathode cavity pressure of the fuel cell stack.

[0016] Preferably, the hydrogen circuit subsystem includes:

[0017] Hydrogen cylinder, primary pressure reducing valve, secondary pressure reducing valve, second water flow sensor, first three-way valve, second tail valve, hydrogen circulation pump and water-gas separator;

[0018] The hydrogen cylinder, primary pressure reducing valve, secondary pressure reducing valve, and cold-side inlet of the heat exchanger are connected in sequence. The cold-side outlet of the heat exchanger is connected to the anode inlet of the fuel cell stack. The second water flow sensor, the first three-way valve, and the second tail valve are connected in sequence. The second water flow sensor is connected to the anode outlet of the fuel cell stack. The first three-way valve is connected in sequence to the water-gas separator and the hydrogen circulation pump. The hydrogen circulation pump is connected to the anode inlet of the fuel cell stack.

[0019] The hydrogen cylinder is used to supply hydrogen. The primary pressure reducing valve and the secondary pressure reducing valve are used to gradually reduce the pressure of the hydrogen at the outlet of the hydrogen cylinder to a preset working pressure. The second water flow sensor is used to monitor the water flow at the outlet of the fuel cell anode. The first three-way valve is used to control the direction of the gas at the outlet of the fuel cell anode. The second tail valve is used to periodically discharge the water accumulated at the outlet of the anode and the nitrogen accumulated in the anode circulation. The hydrogen circulation pump is used to circulate the unreacted hydrogen at the fuel cell anode back to the inlet of the fuel cell anode. The water-gas separator is used to separate liquid water from the tail gas of the fuel cell anode.

[0020] Preferably, the nitrogen path subsystem includes:

[0021] Nitrogen cylinder, nitrogen pressure reducing valve, and second three-way valve;

[0022] The nitrogen cylinder is connected in sequence to the nitrogen pressure reducing valve and the second three-way valve. The second three-way valve is connected to the cathode inlet of the fuel cell stack and the outlet of the secondary pressure reducing valve, respectively.

[0023] The nitrogen cylinder is used to provide high-pressure nitrogen, the nitrogen pressure reducing valve is used to reduce the high-pressure nitrogen at the outlet of the nitrogen cylinder to a preset safe pressure, and the second three-way valve is used to switch the nitrogen flow path.

[0024] Preferably, it further includes:

[0025] The thermal management subsystem, connected to the air circuit subsystem and the controller, is used to cool the high-temperature air in the intercooler and absorb excess heat generated during the operation of the fuel cell stack.

[0026] Preferably, the cooling method of the thermal management subsystem includes:

[0027] Air cooling and water cooling.

[0028] A method for dynamically adjusting water content, the method comprising:

[0029] The output current of the fuel cell stack is acquired using a current acquisition module.

[0030] The amount of water generated is calculated based on the output current.

[0031] The outlet water flow rate of the fuel cell stack is obtained using a water flow sensor;

[0032] Calculate the water content inside the fuel cell stack at the current moment based on the water generation and the outlet water flow rate.

[0033] The current water content inside the fuel cell stack is compared with a preset membrane dryness threshold and a preset flooding threshold to generate corresponding adjustment commands to control the air circuit system, hydrogen circuit system, and nitrogen circuit system.

[0034] The present invention discloses the following technical effects:

[0035] This invention provides a fuel cell system and a method for dynamically adjusting water content. The fuel cell system includes a controller, a fuel cell stack, and a current acquisition module, an air subsystem, a hydrogen subsystem, and a nitrogen subsystem, all connected to the fuel cell stack. The controller is connected to the current acquisition module, the air subsystem, the hydrogen subsystem, and the nitrogen subsystem, respectively. The fuel cell stack outputs current through an electrochemical reaction. The current acquisition module acquires the output current of the fuel cell stack. The air subsystem supplies air to the fuel cell stack. The hydrogen subsystem supplies hydrogen to the fuel cell stack. The nitrogen subsystem adjusts the concentration of air and hydrogen inside the fuel cell stack. The controller calculates the water content inside the fuel cell stack based on the output current and generates adjustment commands to control the air, hydrogen, and nitrogen subsystems. This invention combines real-time water production monitoring and drainage measurement to accurately estimate the internal water content and adjust parameters such as inlet pressure, concentration, and flow rate accordingly, preventing flooding and membrane drying, and improving system reliability and stability. Simultaneously, by combining cathode outlet waste heat recovery and hydrogen preheating strategies, the system's energy utilization efficiency is improved. By estimating the water content inside the fuel cell to determine its operating status and performing corresponding adjustments on both the anode and cathode sides, the system offers more targeted and precise control. The nitrogen circuit subsystem regulates and controls the water production rate, eliminating the need for an external humidifier and maintaining an appropriate water content inside the fuel cell, simplifying the system structure and reducing operating and maintenance costs. A heat exchanger is added to the existing air and hydrogen system loops with minimal changes and ease of implementation. Furthermore, using the high-temperature gas from the fuel cell cathode outlet to preheat the hydrogen at the anode inlet and recovering waste heat improves the overall energy efficiency of the fuel cell. During cold start-up, the cold start performance of the fuel cell can be improved. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 A schematic diagram of a fuel cell system structure is provided as an embodiment of the present invention;

[0038] Figure 2 This is a detailed schematic diagram of a fuel cell system device provided in an embodiment of the present invention.

[0039] Figure label:

[0040] 1. Airflow; 2. Air compressor; 3. Intercooler; 4. First water flow sensor; 5. Heat exchanger; 6. First tailpipe valve; 7. Hydrogen cylinder; 8. First-stage pressure reducing valve; 9. Second-stage pressure reducing valve; 10. Second water flow sensor; 11. First three-way valve; 12. Second tailpipe valve; 13. Water-air separator; 14. Hydrogen circulation pump; 15. Fuel cell stack; 16. Second three-way valve; 17. Nitrogen pressure reducing valve; 18. Nitrogen cylinder; 19. Current acquisition module; 20. Controller; 21. Air circuit subsystem; 22. Hydrogen circuit subsystem; 23. Nitrogen circuit system. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] like Figure 1 As shown, the present invention provides a fuel cell system, comprising:

[0044] The controller 20, the fuel cell stack 15 and the current acquisition module 19, which are all connected to the fuel cell stack 15, the air circuit subsystem 21, the hydrogen circuit subsystem 22, and the nitrogen circuit subsystem 23;

[0045] The controller 20 is connected to the current acquisition module 19, the air circuit subsystem 21, the hydrogen circuit subsystem 22, and the nitrogen circuit subsystem 23 respectively;

[0046] The fuel cell stack 15 is used to output electrical energy through an electrochemical reaction. The current acquisition module 19 is used to acquire the output current of the fuel cell stack 15. The air circuit subsystem 21 is used to supply air to the interior of the fuel cell stack 15. The hydrogen circuit subsystem 22 is used to supply hydrogen to the interior of the fuel cell stack 15. The nitrogen circuit system 23 is used to adjust the concentration of air and hydrogen inside the fuel cell stack 15. The controller 20 is used to calculate the water content inside the fuel cell stack 15 based on the output current of the fuel cell stack 15 and generate adjustment commands to achieve the regulation of the air circuit subsystem 21, the hydrogen circuit system 22, and the nitrogen circuit system 23.

[0047] Specifically, such as Figure 2As shown, the fuel cell stack 15 is an energy conversion device that outputs electrical energy through electrochemical reactions within the stack. The current acquisition module 19 acquires the output current through a current sensor module (such as a Hall current sensor) connected to the fuel cell stack 15.

[0048] Furthermore, the air path subsystem 21 includes:

[0049] 2. Air compressor; 3. Intercooler; 4. First water flow sensor; 5. Heat exchanger; 6. First tail valve;

[0050] The air compressor 2 and the intercooler 3 are connected in sequence. The intercooler 3 is connected to the cathode inlet of the fuel cell stack 15. The first water flow sensor 4, the heat exchanger 5, and the first tail valve 6 are connected in sequence. The first water flow sensor 4 is connected to the cathode outlet of the fuel cell stack 15.

[0051] The air compressor 2 is used to supply air according to the input air flow 1. The intercooler 3 is used to cool the air at the outlet of the air compressor 2. The first water flow sensor 4 is used to monitor the water flow at the cathode outlet of the fuel cell stack 15. The heat exchanger 5 is used to heat the hydrogen at the anode inlet with the high-temperature gas at the cathode outlet of the fuel cell stack 15. The first tail valve 6 is used to exhaust and drain air, discharge unreacted oxygen and nitrogen, maintain stable cathode gas concentration and pressure, periodically discharge produced water, prevent cathode water accumulation and flooding, and ensure the performance of the fuel cell stack 15. It also regulates pressure, is linked with the air compressor 2 to regulate the cathode cavity pressure, and improves system response and stability. As a safety protection channel, it serves as a pressure relief channel to prevent excessive pressure from damaging the fuel cell stack 15 under abnormal operating conditions.

[0052] Specifically, in the air circuit subsystem 21, the air compressor 2 and intercooler 3 are sequentially connected to the cathode inlet of the fuel cell; the first water flow sensor 4, the hot-side inlet of the heat exchanger 5, the hot-side outlet of the heat exchanger 5, and the first tail valve 6 are sequentially connected to the cathode outlet of the fuel cell. The air circuit subsystem 21 supplies the oxygen required for the electrochemical reaction. The air compressor 2 provides air with suitable pressure and flow rate to the fuel cell system. The intercooler 3 cools the high-temperature gas at the outlet of the air compressor 2 to prevent the high-temperature gas from directly entering the fuel cell, which could affect the performance of the stack 15 and the proton exchange membrane. The heat exchanger 5 uses the high-temperature gas from the cathode outlet of the fuel cell to heat the hydrogen at the anode inlet, increasing the reaction rate, recovering waste heat, improving energy utilization, and improving the cold-start performance of the fuel cell during cold start.

[0053] Furthermore, the hydrogen circuit subsystem 22 includes:

[0054] Hydrogen cylinder 7, primary pressure reducing valve 8, secondary pressure reducing valve 9, second water flow sensor 10, first three-way valve 11, second tail valve 12, hydrogen circulation pump 14, water-gas separator 13.

[0055] The hydrogen cylinder 7, the primary pressure reducing valve 8, the secondary pressure reducing valve 9, and the cold side inlet of the heat exchanger 5 are connected in sequence. The cold side outlet of the heat exchanger 5 is connected to the anode inlet of the fuel cell stack 15. The second water flow sensor 10, the first three-way valve 11, and the second tail valve 12 are connected in sequence. The second water flow sensor 10 is connected to the anode outlet of the fuel cell stack 15. The first three-way valve 11 is connected in sequence to the water-gas separator 13 and the hydrogen circulation pump 14. The hydrogen circulation pump 14 is connected to the anode inlet of the fuel cell stack 15.

[0056] Hydrogen cylinder 7, primary pressure reducing valve 8, secondary pressure reducing valve 9, second water flow sensor 10, first three-way valve 11, second tail valve 12, hydrogen circulation pump 14, water-gas separator 13.

[0057] Hydrogen cylinder 7 is used to provide high-pressure hydrogen. The first-stage pressure reducing valve 8 and the second-stage pressure reducing valve 9 are used to gradually reduce the pressure of the high-pressure hydrogen at the outlet of hydrogen cylinder 7 to the working pressure suitable for supplying gas to the anode of fuel cell stack 15. The second water flow sensor 10 is used to monitor the water flow at the outlet of the anode of fuel cell stack 15. The first three-way valve 11 is used to control the destination of the gas at the anode outlet, switching it to a circulation or discharge channel. The first three-way valve 11 connects to the water-gas separator 13 and the hydrogen circulation pump 14 as a circulation channel. The first three-way valve 11 connects to the second tail drain valve 12 as a discharge channel. The second tail drain valve 12 is used to periodically discharge the water accumulated at the anode outlet and the nitrogen accumulated in the anode circulation, maintaining the anode side pressure and gas purity, and ensuring reaction stability. The hydrogen circulation pump 14 is used to circulate the unreacted hydrogen from the anode back to the anode inlet of fuel cell stack 15, improving hydrogen utilization and also serving as an intake humidifier. The water-gas separator 13 is used to separate liquid water from the anode tail gas, assisting in water management and preventing anode flooding.

[0058] Specifically, in the hydrogen circuit subsystem 22, the hydrogen cylinder 7, the primary pressure reducing valve 8, the secondary pressure reducing valve 9, the cold-side inlet of the heat exchanger 5, and the cold-side outlet of the heat exchanger 5 are sequentially connected and connected to the anode inlet of the fuel cell; the second water flow sensor 10, the first three-way valve 11, and the second tail valve 12 are sequentially connected and connected to the anode outlet of the fuel cell; one outlet of the first three-way valve 11 is sequentially connected to the water-gas separator 13 and the hydrogen circulation pump 14, and connected in parallel to the anode inlet of the fuel cell. The hydrogen in the hydrogen circuit subsystem 22, after being depressurized by the secondary pressure reducing valve 9, is used to provide hydrogen at an appropriate pressure to the fuel cell stack 15 to ensure the continuous electrochemical reaction. The water-gas separator 13 separates liquid water and gas at the anode outlet, improving drainage efficiency and preventing water from returning to the fuel cell stack 15 with the gas, thus achieving more effective water management. The hydrogen circulation pump 14 not only improves hydrogen utilization but also acts as an intake humidifier, enhancing the output performance of the fuel cell stack 15.

[0059] Furthermore, the nitrogen path subsystem 23 includes:

[0060] Nitrogen cylinder 18, nitrogen pressure reducing valve 17, and second three-way valve 16;

[0061] Nitrogen cylinder 18 is connected in sequence to nitrogen pressure reducing valve 17 and second three-way valve 16. The second three-way valve 16 is connected to the cathode inlet of the fuel cell stack 15 and the outlet of the secondary pressure reducing valve 9, respectively.

[0062] The nitrogen cylinder 18 is used to supply nitrogen, and the nitrogen pressure reducing valve 17 is used to reduce the high-pressure nitrogen at the outlet of the nitrogen cylinder 18 to a safe pressure suitable for the operation of the system pipeline and the fuel cell stack 15. The second three-way valve 16 is used to switch the nitrogen flow path, which can both achieve directional purging of the cathode or anode channel and adjust the concentration and flow rate of the reactive gas in the cathode or anode channel, thereby controlling the water production rate.

[0063] Specifically, in the nitrogen circuit subsystem 23, the nitrogen cylinder 18 is sequentially connected to the nitrogen pressure reducing valve 17 and the second three-way valve 16. One outlet of the second three-way valve 16 is connected in parallel to the cathode inlet of the fuel cell, and the other outlet of the second three-way valve 16 is connected in parallel to the outlet of the secondary pressure reducing valve 9 of the hydrogen circuit subsystem 22. Besides purging the anode and cathode after the fuel cell stack 15 is shut down, the nitrogen circuit system 23 can also regulate the concentration and flow rate of the reacting gases at the anode and cathode, thereby controlling the water production rate, increasing the purging gas flow rate, and efficiently regulating the water content inside the fuel cell.

[0064] Furthermore, it also includes:

[0065] The thermal management subsystem, connected to the air circuit subsystem 21 and the controller 20, is used to cool the high-temperature air in the intercooler 3 and remove excess heat generated during the operation of the fuel cell stack 15, ensuring that the fuel cell stack 15 operates at a suitable temperature.

[0066] Specifically, fuel cells release a large amount of heat during electrochemical reactions. If this heat is not dissipated in time, the temperature inside the fuel cell stack 15 will rise, causing changes in the water content within the membrane and consequently affecting the performance of the fuel cell. The role of the thermal management subsystem is to remove this heat in a timely manner. Regardless of whether air cooling or water cooling is used, the thermal management subsystem is responsible for cooling the high-temperature air in the intercooler 3 and removing excess heat generated during the operation of the fuel cell stack 15, maintaining the fuel cell at a suitable operating temperature.

[0067] Furthermore, the controller 20 receives real-time operating data collected by the current acquisition module 19 and water flow sensor in the fuel cell system. Based on a built-in algorithm, it estimates the water generation and water content, and intelligently determines the current operating status according to a set water content threshold. It then outputs adjustment commands to control parameters such as intake pressure, gas flow rate, and concentration. The air circuit subsystem 21, hydrogen circuit subsystem 22, and nitrogen circuit subsystem 23 execute corresponding adjustment programs, forming a closed-loop water management control strategy to ensure stable operation of the fuel cell stack 15 under suitable water content conditions. Simultaneously, the controller 20 is also responsible for adjusting the thermal management subsystem components to ensure the fuel cell stack 15 operates at a suitable temperature. The air circuit subsystem 21, hydrogen circuit subsystem 22, nitrogen circuit subsystem 23, and thermal management subsystem are electrically connected to the controller 20.

[0068] This embodiment also provides a method for dynamically adjusting water content, the method comprising:

[0069] The output current of the fuel cell stack is acquired using a current acquisition module.

[0070] The amount of water generated is calculated based on the output current.

[0071] The outlet water flow rate of the fuel cell stack is obtained using a water flow sensor;

[0072] Calculate the water content inside the fuel cell stack at the current moment based on the water generation and the outlet water flow rate.

[0073] The current water content inside the fuel cell stack is compared with a preset membrane dryness threshold and a preset flooding threshold to generate corresponding adjustment commands to control the air circuit system, hydrogen circuit system, and nitrogen circuit system.

[0074] Specifically, by collecting the output current of the fuel cell stack and monitoring the water production and discharge in real time, the internal water content of the fuel cell is accurately estimated and compared with the flooding threshold and the membrane dryness threshold. When the water content is greater than the flooding threshold, it indicates that the internal water content of the fuel cell is too high and it is in a flooded state. When the water content is lower than the membrane dryness threshold, it indicates that the internal water content of the fuel cell is too low and it is in a membrane dryness state.

[0075] When the fuel cell is flooded, the intake pressure of the anode and cathode is increased to enhance scavenging capacity and accelerate water removal. Simultaneously, the second three-way valve is opened to introduce nitrogen into the air and hydrogen circuits, increasing the scavenging flow rate and further accelerating water removal. An appropriate amount of nitrogen is added to the cathode air to reduce the oxygen concentration. A hydrogen-nitrogen mixture is introduced into the anode to reduce the hydrogen concentration entering the stack, lowering the reaction rate and further slowing water formation. The outlet of the water-gas separator is closed via the first three-way valve, and the hydrogen circulation pump is shut off to stop hydrogen circulation humidification and prevent moisture in the circulating hydrogen from entering the fuel cell stack.

[0076] When the fuel cell is in a membrane dry state, the inlet pressure of the anode and cathode is reduced to decrease the scavenging capacity and prevent moisture from being carried out too quickly. At the same time, the inlet flow rates of hydrogen and oxygen are increased to enhance the electrochemical reaction rate and promote water generation inside the fuel cell. Simultaneously, the speed of the hydrogen circulation pump is increased to increase the circulating hydrogen volume and humidify the gas at the anode inlet.

[0077] When the fuel cell is in normal operating condition, the second three-way valve remains closed.

[0078] When the controller receives a shutdown command, the fuel cell needs to enter the shutdown state. The second three-way valve remains open to purge the anode and cathode channels with nitrogen. This mainly removes residual gas and water, preventing damage and aging of the fuel cell.

[0079] More specifically, water generation estimation:

[0080] During the operation of the fuel cell, the output current I of the stack is collected in real time. st The water production per unit time can be estimated using the following formula:

[0081] ;

[0082] In the formula, I st Indicates the stack current; n represents the number of individual cells in the stack; M w The molar mass of water is represented by F; F is the Faraday constant.

[0083] Outlet water flow monitoring:

[0084] Water flow sensors are installed at both the cathode and anode outlets to record the amount of water discharged per unit time, W. w,out .

[0085] Water content estimation:

[0086] Estimate the current water content inside the battery based on the difference between water production and water discharge:

[0087] ;

[0088] It was then compared with the set flooding threshold and membrane dryness threshold.

[0089] Feedback adjustment strategy:

[0090] When the water content is greater than the flooding threshold, increase the intake pressure of the anode and cathode to enhance the scavenging capacity and accelerate the removal of water.

[0091] A mixture of hydrogen and nitrogen is introduced into the anode to reduce the hydrogen concentration and thus the reaction rate. An appropriate amount of nitrogen is added to the cathode air to reduce the oxygen concentration, further slowing water formation and increasing the scavenging gas flow rate to accelerate moisture removal. Simultaneously, the outlet of the water-gas separator connected to the first three-way valve is closed, and the hydrogen circulation pump is shut off to stop hydrogen circulation humidification and prevent moisture in the circulating hydrogen from entering the fuel cell stack.

[0092] When the water content is below the membrane dry threshold, the inlet pressure is reduced to decrease the scavenging capacity and prevent water from being carried out too quickly. The inflow rates of hydrogen and oxygen are increased to enhance the electrochemical reaction rate and promote water generation inside the fuel cell. At the same time, the speed of the hydrogen circulation pump is increased to increase the amount of circulating hydrogen and humidify the gas at the anode inlet.

[0093] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0094] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A fuel cell system, characterized in that, include: The controller, fuel cell stack, and current acquisition modules, air circuit system, hydrogen circuit system, and nitrogen circuit system are all connected to the fuel cell stack. The controller is connected to the current acquisition module, the air circuit subsystem, the hydrogen circuit system, and the nitrogen circuit system, respectively. The fuel cell stack is used to output current through an electrochemical reaction. The current acquisition module is used to acquire the output current of the fuel cell stack. The air circuit subsystem is used to supply air to the inside of the fuel cell stack. The hydrogen circuit subsystem is used to supply hydrogen to the inside of the fuel cell stack. The nitrogen circuit subsystem is used to adjust the concentration of air and hydrogen inside the fuel cell stack. The controller is used to calculate the water content inside the fuel cell stack based on the output current of the fuel cell stack and generate adjustment commands to achieve the control of the air circuit subsystem, hydrogen circuit system, and nitrogen circuit system. The hydrogen supply subsystem includes: Hydrogen cylinder, primary pressure reducing valve, secondary pressure reducing valve, second water flow sensor, first three-way valve, second tail valve, hydrogen circulation pump and water-gas separator; The hydrogen cylinder, primary pressure reducing valve, secondary pressure reducing valve, and cold-side inlet of the heat exchanger are connected in sequence. The cold-side outlet of the heat exchanger is connected to the anode inlet of the fuel cell stack. The second water flow sensor, the first three-way valve, and the second tail valve are connected in sequence. The second water flow sensor is connected to the anode outlet of the fuel cell stack. The first three-way valve is connected in sequence to the water-gas separator and the hydrogen circulation pump. The hydrogen circulation pump is connected to the anode inlet of the fuel cell stack. The hydrogen cylinder is used to supply hydrogen. The primary pressure reducing valve and the secondary pressure reducing valve are used to gradually reduce the pressure of the hydrogen at the outlet of the hydrogen cylinder to a preset working pressure. The second water flow sensor is used to monitor the water flow at the outlet of the fuel cell anode. The first three-way valve is used to control the direction of the gas at the outlet of the fuel cell anode. The second tail valve is used to periodically discharge the water accumulated at the outlet of the anode and the nitrogen accumulated in the anode circulation. The hydrogen circulation pump is used to circulate the unreacted hydrogen at the fuel cell anode back to the inlet of the fuel cell anode. The water-gas separator is used to separate liquid water from the tail gas of the fuel cell anode. The nitrogen gas supply subsystem includes: Nitrogen cylinder, nitrogen pressure reducing valve, and second three-way valve; The nitrogen cylinder is connected in sequence to the nitrogen pressure reducing valve and the second three-way valve. The second three-way valve is connected to the cathode inlet of the fuel cell stack and the outlet of the secondary pressure reducing valve, respectively. The nitrogen cylinder is used to provide high-pressure nitrogen, the nitrogen pressure reducing valve is used to reduce the high-pressure nitrogen at the outlet of the nitrogen cylinder to a preset safe pressure, and the second three-way valve is used to switch the nitrogen flow path. The air circuit subsystem includes: Air compressor, intercooler, first water flow sensor, heat exchanger, and first tail valve; The air compressor and intercooler are connected in sequence. The intercooler is connected to the cathode inlet of the fuel cell stack. The first water flow sensor, heat exchanger and first tail valve are connected in sequence. The first water flow sensor is connected to the cathode outlet of the fuel cell stack. The air compressor is used to supply air, the intercooler is used to cool the air at the outlet of the air compressor, the first water flow sensor is used to monitor the water flow at the cathode outlet of the fuel cell stack, the heat exchanger is used to heat the hydrogen at the anode inlet of the fuel cell stack using the high-temperature gas at the cathode outlet of the fuel cell stack, and the first tail valve is used to discharge unreacted oxygen and nitrogen and regulate the cathode cavity pressure of the fuel cell stack. Among them, when the fuel cell is in a membrane dry state, the inlet pressure of the anode and cathode is reduced, while the inlet flow rates of hydrogen and oxygen are increased. When the fuel cell is submerged, the intake pressure of the anode and cathode is increased, and the second three-way valve is opened to introduce nitrogen into the air circuit system and the hydrogen circuit system, thereby reducing the concentration of oxygen and hydrogen.

2. The fuel cell system according to claim 1, characterized in that, Also includes: The thermal management subsystem, connected to the air circuit subsystem and the controller, is used to cool the high-temperature air in the intercooler and absorb excess heat generated during the operation of the fuel cell stack.

3. A fuel cell system according to claim 2, characterized in that, The cooling methods of the thermal management subsystem include: Air cooling and water cooling.

4. A method for dynamically adjusting water content, applied to the fuel cell system according to any one of claims 1-3, characterized in that, The adjustment method includes: The output current of the fuel cell stack is acquired using a current acquisition module. The amount of water generated is calculated based on the output current. The outlet water flow rate of the fuel cell stack is obtained using a water flow sensor; Calculate the water content inside the fuel cell stack at the current moment based on the water generation and the outlet water flow rate. The current water content inside the fuel cell stack is compared with a preset membrane dryness threshold and a preset flooding threshold to generate corresponding adjustment commands to control the air circuit system, hydrogen circuit system, and nitrogen circuit system.

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