A closed-loop hydrogen-oxygen fuel cell system and its control method

Abstract

This invention relates to a closed-loop hydrogen-oxygen fuel cell system and its control method. The closed-loop hydrogen-oxygen fuel cell system includes a hydrogen-oxygen fuel cell stack, an oxygen gas path, a hydrogen gas path, and a nitrogen gas path. The oxygen gas path includes an oxygen ejector, an oxygen water separator, and an oxygen water storage tank. The oxygen ejector is connected to the oxygen water separator, and an oxygen circulation solenoid valve is installed between them. The oxygen water separator is connected to the oxygen water storage tank to form a drainage pipeline. The oxygen ejector and the oxygen water separator are respectively connected to the inlet and outlet of the hydrogen-oxygen fuel cell stack, forming a circulation gas path between the oxygen ejector, the oxygen water separator, and the hydrogen-oxygen fuel cell stack. The hydrogen gas path is similar. The nitrogen gas path includes a nitrogen medium-pressure solenoid valve and a nitrogen medium-pressure sensor. The nitrogen medium-pressure solenoid valve is connected to the inlet of the oxygen proportional valve and the hydrogen proportional valve through a nitrogen branch. Compared with the prior art, this invention achieves closed-loop operation and effective drainage of the hydrogen-oxygen fuel cell system, avoiding damage to the fuel cell system caused by difficulty in drainage.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, and in particular relates to a closed-loop hydrogen-oxygen fuel cell system and its control method. Background Technology

[0002] Fuel cells have attracted much attention as a clean and efficient energy conversion technology. When operating in enclosed environments such as underwater vehicles, hydrogen-oxygen fuel cells can achieve closed-loop operation by supplying pure oxygen to the cathode, avoiding the accumulation of impurity gases such as nitrogen, thus meeting the requirements for high fuel utilization and zero emissions.

[0003] However, the internal reaction gas flow rate of a closed-loop hydrogen-oxygen fuel cell system is very low, and the water generated during operation cannot be effectively discharged. Furthermore, the accumulation of gas interpenetration during long-term operation will lead to one or more of the following problems: (1) The accumulation of liquid water in the catalyst layer, gas diffusion layer, and flow channel will cause water management problems such as "flooding". "Flooding" will not only occur in the catalyst layer or diffusion layer of the electrode, but also in the flow channel of the battery, hindering the transmission of reaction gas to the active sites of the catalyst, resulting in uneven current density distribution and decreased battery performance; (2) The accumulation of liquid water may even cause local oxygen deficiency and other problems such as "oxygen hunger". (3) In order to achieve effective drainage, closed systems often use a circulating pump to circulate the gas and drain it through a water distributor. However, the circulating pump will increase the auxiliary power consumption of the system and increase the noise of the system. (4) Hydrogen and oxygen permeate each other and it is a closed system. The hydrogen concentration at the cathode may exceed the explosion limit, causing safety hazards. (5) After the closed hydrogen-oxygen fuel cell system is shut down, a large amount of oxygen and hydrogen are consumed at the cathode and anode, resulting in a large negative pressure and pressure difference. It may even produce a "hydrogen-air interface", causing performance damage.

[0004] Therefore, in view of the problems existing in the closed-loop hydrogen-oxygen fuel cell system, there is an urgent need to develop a new type of closed-loop hydrogen-oxygen fuel cell system and its control method. Summary of the Invention

[0005] The purpose of this invention is to solve the problem of ineffective drainage of internal moisture in closed-loop hydrogen-oxygen fuel cell systems, and to provide a closed-loop hydrogen-oxygen fuel cell system and its control method to avoid damage to the fuel cell system caused by difficulty in drainage.

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

[0007] A closed-loop hydrogen-oxygen fuel cell system includes a hydrogen-oxygen fuel cell stack, an oxygen gas path, a hydrogen gas path, and a nitrogen gas path.

[0008] The oxygen gas path includes an oxygen ejector, an oxygen water separator, and an oxygen water storage tank; the oxygen ejector is connected to the oxygen water separator, and an oxygen circulation solenoid valve is provided between them; the oxygen water separator is connected to the oxygen water storage tank to form a drain pipe; the oxygen ejector and the oxygen water separator are respectively connected to the inlet and outlet of the hydrogen-oxygen fuel cell stack, so that a circulation gas path is formed between the oxygen ejector, the oxygen water separator, and the hydrogen-oxygen fuel cell stack; the oxygen gas path also includes an oxygen medium-pressure solenoid valve and an oxygen proportional valve connected to it, and the oxygen proportional valve is connected to the inlet of the oxygen ejector.

[0009] The hydrogen gas path includes a hydrogen ejector, a hydrogen water separator, and a hydrogen water storage tank; the hydrogen ejector is connected to the hydrogen water separator, and a hydrogen circulation solenoid valve is provided between them; the hydrogen water separator is connected to the hydrogen water storage tank to form a drainage pipeline; the hydrogen ejector and the hydrogen water separator are respectively connected to the inlet and outlet of the hydrogen-oxygen fuel cell stack, so that a circulation gas path is formed between the hydrogen ejector, the hydrogen water separator, and the hydrogen-oxygen fuel cell stack; the hydrogen gas path also includes a hydrogen medium-pressure solenoid valve and a hydrogen proportional valve connected to it, and the hydrogen proportional valve is connected to the inlet of the hydrogen ejector;

[0010] The nitrogen gas path includes a nitrogen medium-pressure solenoid valve and a nitrogen medium-pressure sensor. The nitrogen medium-pressure solenoid valve is connected to the inlet of the oxygen proportional valve and the inlet of the hydrogen proportional valve through the nitrogen branch, respectively.

[0011] During operation, based on the fluctuations in the individual unit voltage detected by the voltage inspection unit, and using methods such as clustering, the individual unit voltage state corresponding to the flooding state of the fuel cell stack is established. This allows for analysis of the fuel cell stack's flooding state. By automatically controlling the nitrogen medium-pressure solenoid valve, hydrogen medium-pressure solenoid valve, and oxygen medium-pressure solenoid valve, the gas flow rate at the cathode and anode is increased, enabling rapid water separation during operation and preventing system failures caused by flooding.

[0012] Furthermore, an oxygen inlet temperature and pressure sensor is provided at the oxygen inlet of the hydrogen-oxygen fuel cell stack.

[0013] Furthermore, a hydrogen inlet temperature and pressure sensor is provided at the hydrogen inlet of the hydrogen-oxygen fuel cell stack.

[0014] Furthermore, an oxygen drainage solenoid valve is provided between the oxygen separator and the oxygen storage tank.

[0015] Furthermore, a hydrogen drainage solenoid valve is provided between the hydrogen water separator and the hydrogen storage tank.

[0016] Furthermore, an oxygen-hydrogen sensor is installed at the outlet of the oxygen separator.

[0017] Furthermore, an oxygen sensor in hydrogen is provided at the outlet of the hydrogen water separator.

[0018] The oxygen-hydrogen sensor and the hydrogen-oxygen sensor can monitor the hydrogen concentration on the cathode side and the oxygen concentration on the anode side in real time during system operation. By controlling the drain solenoid valve in real time, the hydrogen and oxygen concentrations at the cathode and anode can be maintained within a safe threshold range and at a high stack efficiency value, thereby improving the safety and efficiency of the system.

[0019] Furthermore, the oxygen separator is connected to both a high oxygen level sensor and a low oxygen level sensor.

[0020] Furthermore, the hydrogen separator is connected to a high hydrogen level sensor and a low hydrogen level sensor.

[0021] The aforementioned liquid level sensor can provide liquid water status feedback for drainage control during system operation, enabling precise control of drainage by the drainage solenoid valve, avoiding excessive emissions of hydrogen and oxygen, and improving the utilization rate of hydrogen and oxygen.

[0022] Furthermore, the nitrogen medium-pressure solenoid valve is connected to the nitrogen medium-pressure sensor, and the nitrogen gas is divided into two nitrogen gas branches after passing through the nitrogen medium-pressure sensor;

[0023] One nitrogen branch is equipped with a first check valve and connected to the inlet of the oxygen proportional valve, while the other nitrogen branch is equipped with a second check valve and connected to the hydrogen proportional valve.

[0024] The present invention also provides a control method based on the above-mentioned closed-loop hydrogen-oxygen fuel cell system, specifically including the following operating modes:

[0025] S1 start-up purging mode: Close the nitrogen gas path; in the oxygen gas path, close the oxygen circulation solenoid valve, and oxygen enters the hydrogen-oxygen fuel cell stack through the oxygen ejector, and then the residual liquid water is discharged into the oxygen storage tank through the oxygen water separator; then open the oxygen circulation solenoid valve to discharge the residual gas in the circulation branch to complete the purging; the hydrogen gas path is the same.

[0026] S2 Normal Closed-Loop Operation Mode: The nitrogen gas path is closed; in the oxygen gas path, the oxygen circulation solenoid valve is opened and the drain pipe is closed; oxygen enters the inlet of the oxygen ejector, and after being separated by water in the circulation gas path, it returns to the return port of the oxygen ejector and enters the hydrogen-oxygen fuel cell stack; the oxygen after the reaction is separated by water and re-enters the circulation gas path, realizing the closed-loop operation of the system; the hydrogen gas path is the same.

[0027] S3 Water Separation Mode: Open the nitrogen gas path; in the oxygen gas path, open the oxygen circulation solenoid valve, and the mixed gas of nitrogen and oxygen is separated into water in the circulation gas path and returned to the return port of the oxygen ejector and enters the hydrogen-oxygen fuel cell stack; the oxygen after the reaction is separated into water and then enters the circulation gas path again for closed-loop operation; open the drain pipe to discharge the nitrogen used for water separation; the hydrogen gas path is the same.

[0028] S4 Drainage Mode: Close the nitrogen gas path; in the oxygen gas path, open the oxygen circulation solenoid valve to operate in the normal closed-loop mode (S2); open the drain pipe to effectively drain the liquid water; the same applies to the hydrogen gas path.

[0029] S5 Purification Mode: The nitrogen gas path is closed; in the oxygen gas path, the oxygen circulation solenoid valve is closed, and oxygen enters the hydrogen-oxygen fuel cell stack through the oxygen ejector, and then the liquid water is discharged into the oxygen storage tank through the oxygen water separator; after the hydrogen concentration drops to a safe range, it enters the S2 normal closed-loop operation mode; the hydrogen gas path is the same.

[0030] S6 shutdown purging mode: Open the nitrogen gas line; in the oxygen gas line, close the oxygen input, open the oxygen circulation solenoid valve, and the nitrogen gas will run in the S2 normal closed-loop operation mode; open the drain pipe to discharge nitrogen gas and residual liquid water; the hydrogen gas line is the same.

[0031] Furthermore, in the S2 normal closed-loop operation mode, S3 water separation mode, S4 drainage mode and S5 purification mode, the oxygen inlet temperature and pressure sensor and the hydrogen inlet temperature and pressure sensor are used as feedback quantities to achieve precise pressure control of the hydrogen-oxygen fuel cell stack through closed-loop control.

[0032] Furthermore, in the S4 drainage mode, timing switch control is performed based on the oxygen high level sensor and the oxygen low level sensor to maintain the liquid water in the oxygen separator at a low level; the same applies to the hydrogen separator.

[0033] Furthermore, in S5 purification mode, oxygen-to-hydrogen sensors and hydrogen-to-oxygen sensors are used as feedback quantities to ensure that the hydrogen and oxygen concentrations at the cathode and anode are maintained within safe threshold ranges and at high stack efficiency values.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The closed-loop hydrogen-oxygen fuel cell system of the present invention can achieve closed-loop operation and effective drainage of the hydrogen-oxygen fuel cell system through the reasonable layout design of the hydrogen-oxygen fuel cell stack, oxygen gas path, hydrogen gas path and nitrogen gas path, thus avoiding damage to the fuel cell system due to difficulty in drainage.

[0036] (2) The present invention adopts an ejector scheme in both the hydrogen gas path and the oxygen gas path, eliminating the traditional circulating pump structure, which can reduce the power consumption and noise of auxiliary system components, greatly improve the system efficiency and reduce the system noise.

[0037] (3) The present invention adds high and low liquid level sensors to the hydrogen gas path and the oxygen gas path respectively, which can provide liquid water status feedback for drainage control during system operation, realize precise control of drainage solenoid valve, avoid excess emission of hydrogen and oxygen, and improve the utilization rate of hydrogen and oxygen.

[0038] (4) The present invention adds oxygen-hydrogen and hydrogen-oxygen sensors to the circulating gas paths of the hydrogen gas path and the oxygen gas path, respectively. During the operation of the system, the hydrogen concentration on the cathode side and the oxygen concentration on the anode side can be monitored in real time. By controlling the drain solenoid valve in real time, the hydrogen concentration and oxygen concentration of the cathode and anode can be maintained within a safe threshold range and at a high stack efficiency value, thereby improving the safety and efficiency of the system.

[0039] (5) The closed-loop hydrogen-oxygen fuel cell system of the present invention introduces a nitrogen branch. During operation, the flooding status of the fuel cell stack is analyzed based on the fluctuation of the cell voltage detected by the voltage inspection unit. By automatically controlling the nitrogen medium-pressure solenoid valve, the hydrogen medium-pressure solenoid valve and the oxygen medium-pressure solenoid valve, the flow rate of the purging gas of the cathode and anode during operation is increased, thereby improving the drainage efficiency and gas purification, and avoiding system failures caused by flooding.

[0040] (6) The closed-loop hydrogen-oxygen fuel cell system of the present invention introduces a nitrogen branch. During shutdown, the liquid water purging and gas replacement of the cathode and anode are realized by automatically controlling the nitrogen medium-pressure solenoid valve, the hydrogen medium-pressure solenoid valve and the oxygen medium-pressure solenoid valve, so as to avoid the excessive internal pressure difference of the system and the performance damage caused by the consumption of hydrogen and oxygen during shutdown.

[0041] (7) The closed-loop hydrogen-oxygen fuel cell system of the present invention can achieve closed-loop operation to meet the requirements of high fuel utilization and zero emissions, and improve the safety and efficiency of the hydrogen-oxygen fuel cell system. It can be widely used in closed environments such as underwater vehicles and has industrial application prospects. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the closed-loop hydrogen-oxygen fuel cell system of the present invention.

[0043] Figure 2 This is a schematic diagram of the control method of the closed-loop hydrogen-oxygen fuel cell system of the present invention in the start-up purging mode.

[0044] Figure 3 This is a schematic diagram of the control method of the closed-loop hydrogen-oxygen fuel cell system of the present invention in normal closed-loop operation mode.

[0045] Figure 4 This is a schematic diagram of the control method of the closed-loop hydrogen-oxygen fuel cell system of the present invention in water-splitting mode.

[0046] Figure 5 This is a schematic diagram of the control method of the closed-loop hydrogen-oxygen fuel cell system of the present invention in drainage mode.

[0047] Figure 6 This is a schematic diagram of the control method of the closed-loop hydrogen-oxygen fuel cell system of the present invention in purification mode.

[0048] Figure 7 This is a schematic diagram of the control method of the closed-loop hydrogen-oxygen fuel cell system of the present invention in the shutdown purging mode.

[0049] Explanation of the markings in the diagram.

[0050] 10 - Hydrogen-oxygen fuel cell stack; 11 - Voltage monitoring unit;

[0051] 20-Oxygen ejector, 21-Oxygen water separator, 22-Oxygen water storage tank, 23-Oxygen medium-pressure solenoid valve, 24-Oxygen proportional valve, 25-Oxygen circulation solenoid valve, 26-Oxygen inlet temperature and pressure sensor, 27-Oxygen drain solenoid valve, 28-Oxygen medium hydrogen sensor, 291-Oxygen high liquid level sensor, 292-Oxygen low liquid level sensor.

[0052] 30-Hydrogen ejector, 31-Hydrogen water separator, 32-Hydrogen water storage tank, 33-Hydrogen medium-pressure solenoid valve, 34-Hydrogen proportional valve, 35-Hydrogen circulation solenoid valve, 36-Hydrogen inlet temperature and pressure sensor, 37-Hydrogen drain solenoid valve, 38-Hydrogen oxygen sensor, 391-Hydrogen high level sensor, 392-Hydrogen low level sensor.

[0053] 40 - Nitrogen medium-pressure solenoid valve, 41 - Nitrogen medium-pressure sensor, 42 - First check valve, 43 - Second check valve. Detailed Implementation

[0054] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0055] In this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention; the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly, for example, they can be fixed connections, detachable connections, or integral connections; they can be mechanical connections or electrical connections; they can be direct connections or indirect connections through an intermediate medium; they can be internal connections between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0056] Example 1:

[0057] This embodiment provides a closed-loop hydrogen-oxygen fuel cell system, which includes a hydrogen-oxygen fuel cell stack 10, an oxygen gas path, a hydrogen gas path, and a nitrogen gas path.

[0058] The oxygen gas path includes an oxygen ejector 20, an oxygen separator 21, and an oxygen storage tank 22. The oxygen ejector 20 is connected to the oxygen separator 21, and an oxygen circulation solenoid valve 25 is installed between them. The oxygen separator 21 is connected to the oxygen storage tank 22 to form a drain pipe. The oxygen ejector 20 and the oxygen separator 21 are respectively connected to the inlet and outlet of the hydrogen-oxygen fuel cell stack 10, forming a circulating gas path between the oxygen ejector 20, the oxygen separator 21, and the hydrogen-oxygen fuel cell stack 10. The oxygen gas path also includes an oxygen medium-pressure solenoid valve 23 and an oxygen proportional valve 24 connected to it; the oxygen proportional valve 24 is connected to the inlet of the oxygen ejector 20.

[0059] The hydrogen gas path includes a hydrogen ejector 30, a hydrogen water separator 31, and a hydrogen water storage tank 32. The hydrogen ejector 30 is connected to the hydrogen water separator 31, and a hydrogen circulation solenoid valve 35 is installed between them. The hydrogen water separator 31 is connected to the hydrogen water storage tank 32 to form a drain pipe. The hydrogen ejector 30 and the hydrogen water separator 31 are respectively connected to the inlet and outlet of the hydrogen-oxygen fuel cell stack 10, forming a circulating gas path between the hydrogen ejector 30, the hydrogen water separator 31, and the hydrogen-oxygen fuel cell stack 10. The hydrogen gas path also includes a hydrogen medium-pressure solenoid valve 33 and a hydrogen proportional valve 34 connected to it; the hydrogen proportional valve 34 is connected to the inlet of the hydrogen ejector 30.

[0060] The nitrogen gas circuit includes a nitrogen medium-pressure solenoid valve 40 and a nitrogen medium-pressure sensor 41. The nitrogen medium-pressure solenoid valve 40 is connected to the inlet of the oxygen proportional valve 24 and the inlet of the hydrogen proportional valve 34 through the nitrogen branch.

[0061] Example 2:

[0062] This embodiment provides a closed-loop hydrogen-oxygen fuel cell system, which includes a hydrogen-oxygen fuel cell stack 10, an oxygen gas path, a hydrogen gas path, and a nitrogen gas path.

[0063] The difference from Example 1 is that, in this example, an oxygen inlet temperature and pressure sensor 26 is provided at the oxygen inlet of the hydrogen-oxygen fuel cell stack 10, and a hydrogen inlet temperature and pressure sensor 36 is provided at the hydrogen inlet of the hydrogen-oxygen fuel cell stack 10, which can detect the pressure and temperature of oxygen and hydrogen entering the hydrogen-oxygen fuel cell stack 10, respectively. An oxygen drain solenoid valve 27 is provided between the oxygen separator 21 and the oxygen storage tank 22, and a hydrogen drain solenoid valve 37 is provided between the hydrogen separator 31 and the hydrogen storage tank 32. An oxygen-hydrogen sensor 28 is provided at the outlet of the oxygen separator 21 to monitor the concentration of hydrogen permeating from the anode; a hydrogen-oxygen sensor 38 is provided at the outlet of the hydrogen separator 31 to monitor the concentration of oxygen permeating from the cathode. The oxygen separator 21 is connected to an oxygen high level sensor 291 and an oxygen low level sensor 292, and the hydrogen separator 31 is connected to a hydrogen high level sensor 391 and a hydrogen low level sensor 392. The above level sensors are used to monitor the liquid water content in the oxygen separator 21 and the hydrogen separator 31, respectively.

[0064] In this embodiment, the nitrogen medium-pressure solenoid valve 40 is connected to the nitrogen medium-pressure sensor 41. After passing through the nitrogen medium-pressure sensor 41, the nitrogen is divided into two nitrogen branches. One nitrogen branch is equipped with a first one-way valve 42 and is connected to the inlet of the oxygen proportional valve 24. The other nitrogen branch is equipped with a second one-way valve 43 and is connected to the hydrogen proportional valve 34.

[0065] Example 3:

[0066] This embodiment provides a closed-loop hydrogen-oxygen fuel cell system and a specific control method. Considering that the internal reaction gas flow rate of the closed-loop hydrogen-oxygen fuel cell system is very low, the water generated during operation cannot be effectively discharged, and the accumulation of mutual permeation of gases during long-term operation will lead to one or more of the following problems: (1) The accumulation of liquid water in the catalyst layer, gas diffusion layer and flow channel will cause water management problems such as "flooding". "Flooding" will not only occur in the catalyst layer or diffusion layer of the electrode, but also in the flow channel of the battery, hindering the transmission of reaction gas to the active sites of the catalyst, resulting in uneven current density distribution and a decrease in battery performance; (2) The accumulation of liquid water may even cause local gas shortages, etc. (3) In order to achieve effective drainage, closed systems often use a circulating pump to circulate the gas and drain it through a water distributor. However, the circulating pump will increase the auxiliary power consumption of the system and increase the noise of the system. (4) The mutual permeation of gases, and being a closed system, may cause the hydrogen concentration at the cathode to exceed the explosion limit, resulting in safety hazards. (5) After the closed hydrogen-oxygen fuel cell system is shut down, the oxygen and hydrogen at the cathode and anode are consumed in large quantities, resulting in a large negative pressure and pressure difference, and may even produce a "hydrogen-air interface", causing performance damage.

[0067] This embodiment aims to solve the aforementioned problems through the following closed-loop hydrogen-oxygen fuel cell system. To control the on / off flow of gas entering the hydrogen-oxygen fuel cell stack 10, the oxygen and hydrogen gas paths are controlled by oxygen medium-pressure solenoid valve 23 and hydrogen medium-pressure solenoid valve 33, respectively. Similarly, the nitrogen gas path is controlled by nitrogen medium-pressure solenoid valve 40. During operation, based on the fluctuations in individual cell voltage detected by the voltage monitoring unit 11, and using methods such as clustering, the individual cell voltage state corresponding to the flooding state of the hydrogen-oxygen fuel cell stack 10 is established. This allows for analysis of the stack's flooding state. By automatically controlling the nitrogen medium-pressure solenoid valve 40, hydrogen medium-pressure solenoid valve 33, and oxygen medium-pressure solenoid valve 23, the gas flow rates at the cathode and anode are increased, enabling rapid water separation during operation and preventing system failures caused by flooding.

[0068] Specifically, the closed-loop hydrogen-oxygen fuel cell system of this embodiment includes a hydrogen-oxygen fuel cell stack 10, a voltage monitoring unit 11, an oxygen medium-pressure solenoid valve 23, an oxygen proportional valve 24, an oxygen ejector 20, an oxygen inlet temperature and pressure sensor 26, an oxygen water separator 21, an oxygen high level sensor 291, an oxygen low level sensor 292, an oxygen drain solenoid valve 27, an oxygen-hydrogen sensor 28, an oxygen circulation solenoid valve 25, an oxygen water storage tank 22, a hydrogen medium-pressure solenoid valve 33, a hydrogen proportional valve 34, a hydrogen ejector 30, a hydrogen inlet temperature and pressure sensor 36, a hydrogen water separator 31, a hydrogen high level sensor 391, a hydrogen low level sensor 392, a hydrogen drain solenoid valve 37, a hydrogen-oxygen sensor 38, a hydrogen circulation solenoid valve 35, a hydrogen water storage tank 32, a nitrogen medium-pressure solenoid valve 40, a nitrogen medium-pressure sensor 41, a first check valve 42, and a second check valve 43.

[0069] The oxygen medium-pressure solenoid valve 23 is connected to the inlet of the oxygen proportional valve 24, and the outlet of the oxygen proportional valve 24 is connected to the inlet of the oxygen ejector 20. The outlet of the oxygen ejector 20 is connected to the oxygen inlet of the hydrogen-oxygen fuel cell stack 10. An oxygen inlet temperature and pressure sensor 26 is placed at the oxygen inlet of the hydrogen-oxygen fuel cell stack 10 to detect the pressure and temperature of oxygen entering the stack. The inlet of the oxygen separator 21 is connected to the oxygen outlet of the hydrogen-oxygen fuel cell stack 10. An oxygen high-level sensor 291 and an oxygen low-level sensor 292 are placed in the middle and lower parts of the oxygen separator 21, respectively, to monitor the liquid water content in the oxygen separator 21. The inlet of the oxygen drain solenoid valve 27 is connected to the lower part of the oxygen separator 21, and the outlet of the oxygen drain solenoid valve 27 is connected to the oxygen storage tank 22. The outlet of the oxygen separator 21 is connected to the oxygen circulation solenoid valve 25. The oxygen hydrogen sensor 28 is placed at the outlet of the oxygen separator 21 to monitor the concentration of hydrogen permeating from the anode. The oxygen circulation solenoid valve 25 is connected to the return port of the oxygen ejector 20.

[0070] The hydrogen medium-pressure solenoid valve 33 is connected to the inlet of the hydrogen proportional valve 34, the outlet of the hydrogen proportional valve 34 is connected to the inlet of the hydrogen ejector 30, and the outlet of the hydrogen ejector 30 is connected to the hydrogen inlet of the hydrogen-oxygen fuel cell stack 10. A hydrogen inlet temperature and pressure sensor 36 is placed at the hydrogen inlet of the hydrogen-oxygen fuel cell stack 10 to detect the pressure and temperature of hydrogen entering the stack. The inlet of the hydrogen water separator 31 is connected to the hydrogen outlet of the hydrogen-oxygen fuel cell stack 10. A high hydrogen level sensor 391 and a low hydrogen level sensor 392 are placed in the middle and lower parts of the hydrogen water separator 31, respectively, to monitor the liquid water content in the hydrogen water separator 31. The inlet of the hydrogen drain solenoid valve 37 is connected to the lower part of the hydrogen separator 31, the outlet of the hydrogen drain solenoid valve 37 is connected to the hydrogen storage tank 32, the outlet of the hydrogen separator 31 is connected to the hydrogen circulation solenoid valve 35, the hydrogen oxygen sensor 38 is placed at the outlet of the hydrogen separator 31 to monitor the concentration of oxygen permeating from the cathode, and the hydrogen circulation solenoid valve 35 is connected to the return port of the hydrogen ejector 30.

[0071] The nitrogen medium-pressure solenoid valve 40 is connected to the nitrogen medium-pressure sensor 41 and is divided into two paths. First, it is connected to the inlet of the oxygen proportional valve 24 through the first one-way valve 42; second, it is connected to the inlet of the hydrogen proportional valve 34 through the second one-way valve 43.

[0072] To achieve precise autonomous control of the reactor feed pressure, the oxygen and hydrogen gas paths use oxygen inlet temperature and pressure sensors 26 and 36 as feedback signals, respectively, and employ oxygen proportional valves 24 and 34 for closed-loop control of the feed pressure. To achieve effective drainage under closed-loop conditions, a circulation and water separation scheme is required. The hydrogen and oxygen gas paths utilize oxygen ejectors 20 and 30, respectively, to achieve circulation, thereby effectively separating water and improving gas distribution consistency. The hydrogen and oxygen gas paths employ hydrogen water separators 31 and 21, respectively, to separate and store liquid water. Oxygen high-level sensors 291 and 292, and hydrogen high-level sensors 391 and 392, respectively, are used to precisely control the timing of oxygen drainage solenoid valves 27 and 37, thereby achieving effective liquid water discharge and avoiding a decrease in utilization caused by excessive gas discharge. The oxygen and hydrogen gas paths utilize oxygen-to-hydrogen sensors 28 and hydrogen-to-oxygen sensors 38, respectively, to monitor the real-time hydrogen concentration on the cathode side and the oxygen concentration on the anode side. Real-time control of the oxygen drain solenoid valve 27 and the hydrogen drain solenoid valve 37 maintains the hydrogen and oxygen concentrations at the cathode and anode within safe threshold ranges and ensures high stack efficiency. Oxygen circulation solenoid valve 25 and hydrogen circulation solenoid valve 35 control the opening and closing of the circulation path. Additionally, a nitrogen pressure sensor 41 monitors the pressure in the nitrogen path, and the first one-way valve 42 and the second one-way valve 43 ensure unidirectional flow of nitrogen gas.

[0073] Figures 2-7 This diagram illustrates the control methods for the closed-loop hydrogen-oxygen fuel cell system under different system operating modes in this embodiment. The specific control methods under different system operating modes are as follows:

[0074] Start-up purging mode is an operating mode of a closed-loop hydrogen-oxygen fuel cell system during startup. The gas flow path is as follows: Figure 2 As shown. In the start-up purging mode, the oxygen circulation solenoid valve 25 and the hydrogen circulation solenoid valve 35 are closed. Oxygen enters the oxygen proportional valve 24 through the oxygen medium-pressure solenoid valve 23, then enters the hydrogen-oxygen fuel cell stack 10 through the oxygen ejector 20, and then directly enters the oxygen drain solenoid valve 27 after passing through the oxygen water separator 21. The oxygen drain solenoid valve 27 is normally open, draining residual gas and liquid water into the oxygen storage tank 22; the hydrogen gas path is the same. After the liquid water is completely drained, the oxygen circulation solenoid valve 25 and the hydrogen circulation solenoid valve 35 are opened. At this time, the circulation branch is opened, and the residual gas in the circulation branch is discharged, thereby realizing the drainage and gas replacement process during start-up.

[0075] Secondly, the normal closed-loop operation mode is the normal power generation mode of a closed-loop hydrogen-oxygen fuel cell system. The gas flow path is as follows: Figure 3 As shown. In normal operating mode, taking the oxygen gas path as an example, the oxygen circulation solenoid valve 25 is open, and oxygen enters the oxygen proportional valve 24 through the oxygen medium-pressure solenoid valve 23. With the oxygen inlet temperature and pressure sensor 26 as feedback, the pressure of the hydrogen-oxygen fuel cell stack 10 is precisely controlled through closed-loop control. The oxygen proportional valve 24 enters the inlet of the oxygen ejector 20. After the liquid water is removed by the oxygen separator 21, the oxygen enters the return port of the oxygen ejector 20 through the oxygen circulation solenoid valve 25. The combined oxygen enters the oxygen inlet of the hydrogen-oxygen fuel cell stack 10 through the oxygen ejector 20. After the reaction, the oxygen enters the oxygen circulation solenoid valve 25 after liquid water separation by the oxygen separator 21. The oxygen drain solenoid valve 27 is closed, thereby realizing the closed-loop operation of the system; the hydrogen gas path is the same as above.

[0076] Secondly, in the closed-loop hydrogen-oxygen fuel cell system, the gas flow path during operation is as follows: (The text abruptly ends here, likely due to an incomplete sentence or a formatting error.) Figure 4 As shown. During operation in drainage mode, taking the oxygen gas path as an example, the oxygen circulation solenoid valve 25 is opened. Nitrogen gas passing through the nitrogen medium-pressure solenoid valve 40 mixes with oxygen gas passing through the oxygen medium-pressure solenoid valve 23 in a certain proportion. Then, the nitrogen medium-pressure solenoid valve 40 is closed, and the mixed gas enters the oxygen proportioning valve 24. Using the oxygen inlet temperature and pressure sensor 26 as feedback, the pressure of the hydrogen-oxygen fuel cell stack 10 is precisely controlled through closed-loop control. The oxygen proportioning valve 24 leads to the inlet of the oxygen ejector 20. After the liquid water is removed by the oxygen water separator 21, the mixed gas enters the return port of the oxygen ejector 20 through the oxygen circulation solenoid valve 25. The combined mixed gas enters the oxygen inlet of the hydrogen-oxygen fuel cell stack 10 through the oxygen ejector 20. The reacted oxygen enters the oxygen circulation solenoid valve 25 after liquid water separation by the oxygen water separator 21. In addition, the oxygen drainage solenoid valve 27 is controlled by a time sequence based on the water separation effect to achieve effective discharge of nitrogen gas used for water separation; the hydrogen gas path is the same.

[0077] Secondly, in the drainage mode of a closed-circuit hydrogen-oxygen fuel cell system during operation, the gas flow path is as follows: Figure 5As shown. During operation in drainage mode, taking the oxygen gas path as an example, the oxygen circulation solenoid valve 25 opens, and oxygen enters the oxygen proportional valve 24 through the oxygen medium-pressure solenoid valve 23. Using the oxygen inlet temperature and pressure sensor 26 as feedback, closed-loop control achieves precise pressure control of the hydrogen-oxygen fuel cell stack 10. The oxygen proportional valve 24 leads to the inlet of the oxygen ejector 20. After liquid water is removed by the oxygen separator 21, the oxygen enters the return port of the oxygen ejector 20 through the oxygen circulation solenoid valve 25. The combined oxygen then enters the oxygen inlet of the hydrogen-oxygen fuel cell stack 10 through the oxygen ejector 20. The reacted oxygen undergoes liquid water separation through the oxygen separator 21 before entering the oxygen circulation solenoid valve 25. Additionally, the oxygen drainage solenoid valve 27 performs time-sequential switching control based on the signal values ​​of the oxygen high-level sensor 291 and the oxygen low-level sensor 292, maintaining the liquid water in the oxygen separator 21 near the low level, thereby achieving effective drainage of liquid water from the closed-loop hydrogen-oxygen fuel cell system and achieving net-zero emissions; the hydrogen gas path is the same.

[0078] Then, in the purification mode during operation of the closed-loop hydrogen-oxygen fuel cell system, the gas flow path is as follows: Figure 6 As shown. In purification mode, taking the oxygen gas path as an example, oxygen enters the oxygen proportional valve 24 through the oxygen medium-pressure solenoid valve 23. Using the oxygen inlet temperature and pressure sensor 26 as feedback, closed-loop control achieves precise pressure control of the hydrogen-oxygen fuel cell stack 10. The oxygen proportional valve 24 enters the inlet of the oxygen ejector 20, the oxygen circulation solenoid valve 25 is closed, and oxygen flows back to the return port of the oxygen ejector 20. The outlet of the oxygen ejector 20 enters the oxygen inlet of the hydrogen-oxygen fuel cell stack 10. After the reaction, the oxygen passes through the oxygen separator 21 and is discharged into the oxygen storage tank 22 through the oxygen drain solenoid valve 27. When the value of the oxygen hydrogen sensor 28 drops below the explosion limit or the specified safety threshold, the system enters the normal power generation mode. By closing the circulation gas path and opening the oxygen drain solenoid valve 27, the hydrogen concentration in the oxygen gas path rapidly decreases, maintaining the hydrogen concentration at the cathode within a safe threshold range and a high stack efficiency value, thereby improving the system's safety and efficiency; the hydrogen gas path is the same.

[0079] Finally, in the shutdown purging mode, the gas flow path of the closed-loop hydrogen-oxygen fuel cell system is as follows: Figure 7As shown. In shutdown purging mode, taking the oxygen gas path as an example, the oxygen medium-pressure solenoid valve 23 is closed, and the nitrogen medium-pressure solenoid valve 40 is open. Nitrogen enters the oxygen proportional valve 24 through the first one-way valve 42. The oxygen proportional valve 24 enters the inlet of the oxygen ejector 20, and the oxygen circulation solenoid valve 25 is opened. After the liquid water is removed by the oxygen separator 21, the nitrogen enters the return port of the oxygen ejector 20 through the oxygen circulation solenoid valve 25. The combined nitrogen enters the oxygen inlet of the hydrogen-oxygen fuel cell stack 10 through the oxygen ejector 20. After the reaction, the nitrogen passes through the oxygen separator 21 and is discharged into the oxygen storage tank 22 through the oxygen drain solenoid valve 27. The nitrogen replaces the oxygen at the cathode and removes the liquid water. The hydrogen gas path is the same. Through the above operations, the excessive internal pressure difference of the system caused by the consumption of hydrogen and oxygen during shutdown and the performance damage caused by the hydrogen-air interface are avoided.

[0080] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A control method for a closed-loop hydrogen-oxygen fuel cell system, characterized in that, The closed-loop hydrogen-oxygen fuel cell system is used in a closed environment and includes a hydrogen-oxygen fuel cell stack (10), an oxygen gas path, a hydrogen gas path, and a nitrogen gas path. The oxygen gas path includes an oxygen ejector (20), an oxygen water separator (21), and an oxygen water storage tank (22); the oxygen ejector (20) is connected to the oxygen water separator (21), and an oxygen circulation solenoid valve (25) is provided between them; the oxygen water separator (21) is connected to the oxygen water storage tank (22) to form a drainage pipeline; the oxygen ejector (20) and the oxygen water separator (21) are respectively connected to the inlet and outlet of the hydrogen-oxygen fuel cell stack (10), so that a circulation gas path is formed between the oxygen ejector (20), the oxygen water separator (21), and the hydrogen-oxygen fuel cell stack (10); the oxygen gas path also includes an oxygen medium-pressure solenoid valve (23) and an oxygen proportional valve (24) connected thereto, and the oxygen proportional valve (24) is connected to the inlet of the oxygen ejector (20); The hydrogen gas path includes a hydrogen ejector (30), a hydrogen water separator (31), and a hydrogen water storage tank (32); wherein the hydrogen ejector (30) is connected to the hydrogen water separator (31) and a hydrogen circulation solenoid valve (35) is provided between them; the hydrogen water separator (31) is connected to the hydrogen water storage tank (32) to form a drainage pipeline; the hydrogen ejector (30) and the hydrogen water separator (31) are respectively connected to the inlet and outlet of the hydrogen-oxygen fuel cell stack (10), so that a circulation gas path is formed between the hydrogen ejector (30), the hydrogen water separator (31), and the hydrogen-oxygen fuel cell stack (10); the hydrogen gas path also includes a hydrogen medium-pressure solenoid valve (33) and a hydrogen proportional valve (34) connected thereto, the hydrogen proportional valve (34) being connected to the inlet of the hydrogen ejector (30); The nitrogen gas path includes a nitrogen medium-pressure solenoid valve (40) and a nitrogen medium-pressure sensor (41). The nitrogen medium-pressure solenoid valve (40) is connected to the inlet of the oxygen proportional valve (24) and the inlet of the hydrogen proportional valve (34) through the nitrogen branch respectively. The control method specifically includes the following operating modes: S1 Start-up Purging Mode: Close the nitrogen gas path; in the oxygen gas path, close the oxygen circulation solenoid valve (25), and oxygen enters the hydrogen-oxygen fuel cell stack (10) through the oxygen ejector (20), and then the residual liquid water is discharged into the oxygen storage tank (22) through the oxygen water separator (21); then open the oxygen circulation solenoid valve (25) to discharge the residual gas in the circulation branch to complete the purging; the hydrogen gas path is the same. S2 Normal Closed-End Operation Mode: Close the nitrogen gas path; in the oxygen gas path, open the oxygen circulation solenoid valve (25) and close the drain pipe; oxygen enters the inlet of the oxygen ejector (20), and after being separated by water in the circulation gas path, it returns to the return port of the oxygen ejector (20) and enters the hydrogen-oxygen fuel cell stack (10); the oxygen after the reaction is separated by water and then re-enters the circulation gas path to achieve closed-end operation of the system; the same applies to the hydrogen gas path. S3 water separation mode: Open the nitrogen gas path; in the oxygen gas path, open the oxygen circulation solenoid valve (25), and return the mixed gas of nitrogen and oxygen to the return port of the oxygen ejector (20) after water separation in the circulation gas path and enter the hydrogen-oxygen fuel cell stack (10); the oxygen after reaction is separated into water and then enters the circulation gas path again for closed-loop operation; open the drain pipe to discharge the nitrogen used for water separation; the hydrogen gas path is the same. S4 Drainage Mode: Close the nitrogen gas path; in the oxygen gas path, open the oxygen circulation solenoid valve (25) and operate in the S2 normal closed-loop mode; open the drain pipe to achieve effective discharge of liquid water; the same applies to the hydrogen gas path. S5 Purification Mode: Close the nitrogen gas path; in the oxygen gas path, close the oxygen circulation solenoid valve (25), and oxygen enters the hydrogen-oxygen fuel cell stack (10) through the oxygen ejector (20), and then the liquid water is discharged into the oxygen storage tank (22) through the oxygen water separator (21); after the hydrogen concentration drops to a safe range, enter the S2 normal closed-loop operation mode; the same applies to the hydrogen gas path; S6 shutdown purging mode: Open the nitrogen gas path; in the oxygen gas path, close the oxygen input, open the oxygen circulation solenoid valve (25), and the nitrogen gas will run in the S2 normal closed-loop operation mode; open the drain pipe to discharge the nitrogen gas and residual liquid water; the hydrogen gas path is the same.

2. The control method for a closed-loop hydrogen-oxygen fuel cell system according to claim 1, characterized in that, The oxygen inlet of the hydrogen-oxygen fuel cell stack (10) is equipped with an oxygen inlet temperature and pressure sensor (26). The hydrogen inlet of the hydrogen-oxygen fuel cell stack (10) is equipped with a hydrogen inlet temperature and pressure sensor (36).

3. The control method for a closed-loop hydrogen-oxygen fuel cell system according to claim 1, characterized in that, An oxygen drain solenoid valve (27) is provided between the oxygen separator (21) and the oxygen storage tank (22). A hydrogen drainage solenoid valve (37) is provided between the hydrogen water separator (31) and the hydrogen storage tank (32).

4. The control method for a closed-loop hydrogen-oxygen fuel cell system according to claim 1, characterized in that, The oxygen separator (21) is equipped with an oxygen-hydrogen sensor (28) at its outlet. The hydrogen separator (31) is equipped with a hydrogen oxygen sensor (38) at its outlet.

5. The control method for a closed-loop hydrogen-oxygen fuel cell system according to claim 1, characterized in that, The oxygen separator (21) is connected to an oxygen high level sensor (291) and an oxygen low level sensor (292) respectively. The hydrogen separator (31) is connected to a high hydrogen level sensor (391) and a low hydrogen level sensor (392).

6. The control method for a closed-loop hydrogen-oxygen fuel cell system according to claim 1, characterized in that, The nitrogen medium-pressure solenoid valve (40) is connected to the nitrogen medium-pressure sensor (41), and the nitrogen gas is divided into two nitrogen branches after passing through the nitrogen medium-pressure sensor (41); One nitrogen branch is equipped with a first check valve (42) and connected to the inlet of the oxygen proportioning valve (24), while the other nitrogen branch is equipped with a second check valve (43) and connected to the inlet of the hydrogen proportioning valve (34).

7. The control method for a closed-loop hydrogen-oxygen fuel cell system according to claim 1, characterized in that, In the S2 normal closed-loop operation mode, S3 water separation mode, S4 drainage mode and S5 purification mode, the oxygen inlet temperature and pressure sensor (26) and the hydrogen inlet temperature and pressure sensor (36) are used as feedback quantities to achieve precise pressure control of the hydrogen-oxygen fuel cell stack (10) through closed-loop control.

8. The control method for a closed-loop hydrogen-oxygen fuel cell system according to claim 1, characterized in that, In the S4 drainage mode, the timing switch control is based on the oxygen high level sensor (291) and oxygen low level sensor (292) to maintain the liquid water in the oxygen separator (21) at a low level; the same applies to the hydrogen separator (31).

9. The control method for a closed-loop hydrogen-oxygen fuel cell system according to claim 1, characterized in that, In S5 purification mode, the hydrogen in oxygen sensor (28) and oxygen in hydrogen sensor (38) are used as feedback quantities to ensure that the hydrogen concentration and oxygen concentration of the cathode and anode are maintained within a safe threshold range and at a high stack efficiency value.

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