Closed hydrogen-oxygen fuel cell system and control method thereof

Abstract

The invention relates to a closed hydrogen-oxygen fuel cell system and a control method thereof. The closed hydrogen-oxygen fuel cell system comprises a hydrogen-oxygen fuel cell stack, an oxygen gas path, a hydrogen gas path and a nitrogen gas path, the oxygen gas path comprises an oxygen ejector, an oxygen water segregator and an oxygen water storage tank; an oxygen circulating electromagnetic valve is arranged between the oxygen ejector and the oxygen water segregator; the oxygen water segregator is connected with the oxygen water storage tank to form a drainage pipeline; the oxygen ejector and the oxygen water knockout drum are respectively connected with an inlet and an outlet of the hydrogen-oxygen fuel cell stack, so that a circulating gas path is formed among the oxygen ejector, the oxygen water knockout drum and the hydrogen-oxygen fuel cell stack; a hydrogen gas path is similar; the nitrogen gas circuit comprises a nitrogen medium-pressure electromagnetic valve and a nitrogen medium-pressure sensor, and the nitrogen medium-pressure electromagnetic valve is connected with an inlet of the oxygen proportional valve and an inlet of the hydrogen proportional valve through nitrogen branches. Compared with the prior art, the closed operation and effective drainage of the hydrogen-oxygen fuel cell system are realized, and the damage to the fuel cell system caused by difficult drainage is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to a closed hydrogen-oxygen fuel cell system and a control method thereof. Background Art

[0002] Fuel cells have attracted much attention as a clean and efficient energy conversion technology. When working in a closed environment such as an underwater submersible, hydrogen-oxygen fuel cells can achieve closed-mouth operation to meet the needs of high fuel utilization and zero emissions because the cathode supplies pure oxygen to avoid the accumulation of impurity gases such as nitrogen.

[0003] However, the reaction gas flow rate inside the closed hydrogen-oxygen fuel cell system is very low, the water generated during operation cannot be effectively discharged, and the accumulation of gas interpenetration during long-term operation will cause 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 the reaction gas to the active site of the catalyst, resulting in uneven current density distribution and decreased battery performance; (2) Liquid water accumulation may even cause "oxygen starvation" such as local gas shortage; (3) In order to achieve effective drainage, the closed system often uses a circulating pump to circulate the gas and drain the water through a water separator. 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, and even a "hydrogen-air interface" will be generated, causing performance damage.

[0004] Therefore, in view of the problems existing in the above-mentioned closed hydrogen-oxygen fuel cell system, it is urgent to develop a new closed hydrogen-oxygen fuel cell system and a control method thereof. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that the internal moisture of a closed hydrogen-oxygen fuel cell system cannot be effectively discharged, and to provide a closed hydrogen-oxygen fuel cell system and a control method thereof to avoid damage to the fuel cell system due to difficulty in draining water.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A closed hydrogen-oxygen fuel cell system, comprising a hydrogen-oxygen fuel cell stack, an oxygen gas path, a hydrogen gas path and a nitrogen gas path;

[0008] The oxygen gas circuit 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 the two; 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, so that a circulation gas circuit is formed between the oxygen ejector, the oxygen water separator and the hydrogen-oxygen fuel cell stack; the oxygen gas circuit also includes an oxygen medium-pressure solenoid valve and an oxygen proportional valve connected thereto, and the oxygen proportional valve is connected to the inlet of the oxygen ejector;

[0009] The hydrogen gas circuit includes a hydrogen ejector, a hydrogen water separator and a hydrogen water storage tank; wherein the hydrogen ejector is connected to the hydrogen water separator and a hydrogen circulation solenoid valve is provided between the two; 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 circuit is formed between the hydrogen ejector, the hydrogen water separator and the hydrogen-oxygen fuel cell stack; the hydrogen gas circuit also includes a hydrogen medium-pressure solenoid valve and a hydrogen proportional valve connected thereto, and the hydrogen proportional valve is connected to the inlet of the hydrogen ejector;

[0010] The nitrogen gas circuit comprises 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 a nitrogen branch respectively.

[0011] During operation, based on the fluctuation of the single cell voltage detected by the voltage inspection unit, the single cell voltage state corresponding to the flooding state of the fuel cell stack is established according to clustering and other methods, so as to analyze the flooding state of the fuel cell stack. By automatically controlling the nitrogen medium-pressure solenoid valve, hydrogen medium-pressure solenoid valve and oxygen medium-pressure solenoid valve, the gas flow rate of the cathode and anode is increased to achieve rapid water separation during operation and avoid 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 water separator and the oxygen water storage tank.

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

[0016] Furthermore, a hydrogen-in-oxygen sensor is provided at the outlet of the oxygen-water separator.

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

[0018] The hydrogen-in-oxygen sensor and the oxygen-in-hydrogen sensor can monitor the hydrogen concentration on the cathode side and the oxygen concentration on the anode side in real time during system operation, and through real-time control of the drain solenoid valve, 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 water separator is connected to an oxygen high liquid level sensor and an oxygen low liquid level sensor respectively.

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

[0021] The above-mentioned liquid level sensor can provide liquid water state feedback for drainage control during system operation, realize precise control of drainage by the drainage solenoid valve, avoid excess discharge of hydrogen and oxygen, and improve the utilization rate of hydrogen and oxygen.

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

[0023] A first one-way valve is disposed in one of the nitrogen branches and is connected to the inlet of the oxygen proportional valve, and a second one-way valve is disposed in the other nitrogen branch and is connected to the hydrogen proportional valve.

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

[0025] S1 startup purge mode: close the nitrogen gas line; in the oxygen gas line, close the oxygen circulation solenoid valve, 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 purge; the same applies to the hydrogen gas line;

[0026] S2 Normal closed-end operation mode: Close the nitrogen gas circuit; in the oxygen gas circuit, open the oxygen circulation solenoid valve and close the drainage pipeline; oxygen enters the inlet of the oxygen ejector, returns to the reflux port of the oxygen ejector after water separation in the circulation gas circuit and enters the hydrogen-oxygen fuel cell stack; the reacted oxygen enters the circulation gas circuit again after water separation to realize the closed-end operation of the system; the same applies to the hydrogen gas circuit;

[0027] S3 water separation mode: open the nitrogen gas circuit; in the oxygen gas circuit, open the oxygen circulation solenoid valve, and return the mixed gas of nitrogen and oxygen to the reflux port of the oxygen ejector after water separation through the circulation gas circuit and enter the hydrogen-oxygen fuel cell stack; the oxygen after the reaction enters the circulation gas circuit again after water separation for closed-end operation; open the drainage pipeline to discharge the nitrogen used for water separation; the same applies to the hydrogen gas circuit;

[0028] S4 drainage mode: close the nitrogen gas circuit; in the oxygen gas circuit, open the oxygen circulation solenoid valve and operate in the S2 normal closed-mouth operation mode; open the drainage pipeline to achieve effective discharge of liquid water; the same applies to the hydrogen gas circuit;

[0029] S5 purification mode: close the nitrogen gas line; in the oxygen gas line, close the oxygen circulation solenoid valve, oxygen enters the hydrogen-oxygen fuel cell stack through the oxygen ejector, and then discharges liquid water into the oxygen storage tank through the oxygen water separator; wait until the hydrogen concentration drops to a safe range, and then enter the S2 normal closed-mouth operation mode; the same applies to the hydrogen gas line;

[0030] S6 shutdown purge mode: open the nitrogen gas line; in the oxygen gas line, close the oxygen input, open the oxygen circulation solenoid valve, and the nitrogen operates in the S2 normal closed-mouth operation mode; open the drain line to discharge nitrogen and residual liquid water; the same applies to the hydrogen gas line.

[0031] Furthermore, in the S2 normal closed-mouth 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 and oxygen fuel cell stack through closed-loop control.

[0032] Furthermore, in the S4 drainage mode, the oxygen high level sensor and the oxygen low level sensor are used as the basis for timing switch control to maintain the liquid water in the oxygen water separator near the low level; the same applies to the hydrogen water separator.

[0033] Furthermore, in the S5 purification mode, the hydrogen-in-oxygen sensor and the oxygen-in-hydrogen sensor 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.

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

[0035] (1) The closed hydrogen-oxygen fuel cell system of the present invention can achieve closed 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, thereby avoiding damage to the fuel cell system caused by difficulty in drainage.

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

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

[0038] (4) The present invention adds oxygen-in-hydrogen and hydrogen-in-oxygen sensors to the circulating gas circuits of the hydrogen gas circuit and the oxygen gas circuit, 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 real-time control of the drain solenoid valve, the hydrogen concentration and oxygen concentration 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.

[0039] (5) The closed hydrogen-oxygen fuel cell system of the present invention introduces a nitrogen branch. During operation, the water flooding state of the fuel cell stack is analyzed based on the fluctuation of the single 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 purge gas at the cathode and anode during operation is increased, thereby improving the drainage efficiency and gas purification, and avoiding system failures caused by water flooding.

[0040] (6) The closed hydrogen-oxygen fuel cell system of the present invention introduces a nitrogen branch. During the shutdown process, liquid water purge and gas replacement of the cathode and anode are achieved through automatic control of the nitrogen medium-pressure solenoid valve, the hydrogen medium-pressure solenoid valve and the oxygen medium-pressure solenoid valve, thereby avoiding excessive internal pressure difference of the system caused by the consumption of hydrogen and oxygen during the shutdown process and performance damage caused by its hydrogen-air interface.

[0041] (7) The closed-mouth hydrogen-oxygen fuel cell system of the present invention can achieve closed-mouth operation to meet the requirements of high fuel utilization and zero emission, and improve the safety and efficiency of the hydrogen-oxygen fuel cell system. It can be widely used in work in closed environments such as underwater submersibles, and has industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0043] Figure 2 It is a schematic diagram of a control method of a closed hydrogen-oxygen fuel cell system in a startup purge mode of the present invention.

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

[0045] Figure 4 Schematic diagram of the control method of the closed hydrogen and oxygen fuel cell system in the water splitting mode of the present invention.

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

[0047] Figure 6 Schematic diagram of the control method of the closed hydrogen and oxygen fuel cell system in the purification mode of the present invention.

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

[0049] Description of the markings in the figure.

[0050] 10-hydrogen-oxygen fuel cell stack, 11-voltage inspection 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 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 liquid level sensor, 392-hydrogen low liquid level sensor;

[0053] 40 - nitrogen medium-pressure solenoid valve, 41 - nitrogen medium-pressure sensor, 42 - first one-way valve, 43 - second one-way valve. DETAILED DESCRIPTION

[0054] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0055] In the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0056] Embodiment 1:

[0057] The present embodiment provides a closed 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 circuit 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 the two. 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 circuit is formed between the oxygen ejector 20, the oxygen water separator 21 and the hydrogen-oxygen fuel cell stack 10. The oxygen gas circuit 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.

[0059] The hydrogen gas circuit 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 provided between the two. 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 circuit is formed between the hydrogen ejector 30, the hydrogen water separator 31 and the hydrogen-oxygen fuel cell stack 10. The hydrogen gas circuit also includes a hydrogen medium-pressure solenoid valve 33 and a hydrogen proportional valve 34 connected thereto, and 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 proportion valve 24 and the inlet of the hydrogen proportion valve 34 through a nitrogen branch circuit.

[0061] Embodiment 2:

[0062] The present embodiment provides a closed 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 embodiment, 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 respectively detect the pressure and temperature of oxygen and hydrogen entering the hydrogen-oxygen fuel cell stack 10. An oxygen drainage solenoid valve 27 is provided between the oxygen water separator 21 and the oxygen water storage tank 22, and a hydrogen drainage solenoid valve 37 is provided between the hydrogen water separator 31 and the hydrogen water storage tank 32. A hydrogen-in-oxygen sensor 28 is provided at the outlet of the oxygen water separator 21 to monitor the concentration of hydrogen permeated from the anode; and an oxygen-in-hydrogen sensor 38 is provided at the outlet of the hydrogen water separator 31 to monitor the concentration of oxygen permeated from the cathode. The oxygen water separator 21 is connected to an oxygen high level sensor 291 and an oxygen low level sensor 292, respectively, and the hydrogen water separator 31 is connected to a hydrogen high level sensor 391 and a hydrogen low level sensor 392, respectively. The above-mentioned liquid level sensors are used to monitor the liquid water content in the oxygen water separator 21 and the hydrogen water separator 31, respectively.

[0064] The nitrogen medium-pressure solenoid valve 40 of this embodiment 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 of the nitrogen branches is provided with a first one-way valve 42 and is connected to the inlet of the oxygen proportional valve 24, and the other nitrogen branch is provided with a second one-way valve 43 and is connected to the hydrogen proportional valve 34.

[0065] Embodiment 3:

[0066] This embodiment provides a closed hydrogen-oxygen fuel cell system and a specific control method. Considering that the reaction gas flow rate inside the closed hydrogen-oxygen fuel cell system is very low, the water generated during operation cannot be effectively discharged, and the accumulation of gas interpenetration during long-term operation will cause 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 the reaction gas to the active site of the catalyst, resulting in uneven current density distribution and decreased battery performance; (2) Liquid water accumulation may even cause "local gas shortage" and other "flooding" problems. (1) The problem of "oxygen starvation" generates high potential, causes carbon corrosion, and reduces the service life of the battery; (2) In order to achieve effective drainage, the closed system often uses a circulation pump to circulate the gas and drain it through a water separator, but the circulation pump will increase the auxiliary power consumption of the system and increase the noise of the system; (3) In order to achieve effective drainage, the closed system often uses a circulation pump to circulate the gas and drain it through a water separator, but the circulation pump will increase the auxiliary power consumption of the system and increase the noise of the system; (4) The mutual penetration of gases, and the closed system, may cause the hydrogen concentration at the cathode to exceed the explosion limit, causing a safety hazard; (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, causing a large negative pressure and pressure difference, and even a "hydrogen-air interface" will be generated, causing performance damage.

[0067] This embodiment is dedicated to solving the above problems through the following closed hydrogen and oxygen fuel cell system. In order to control the on-off of the gas entering the hydrogen and oxygen fuel cell stack 10, the oxygen gas circuit and the hydrogen gas circuit respectively use the oxygen medium-pressure solenoid valve 23 and the hydrogen medium-pressure solenoid valve 33 to control the on-off of the gas circuit, and the nitrogen gas circuit also uses the nitrogen medium-pressure solenoid valve 40 to control the on-off of the nitrogen gas circuit. During operation, according to the fluctuation of the single cell voltage detected by the voltage inspection unit 11, according to the clustering method, the single cell voltage state corresponding to the flooding state of the hydrogen and oxygen fuel cell stack 10 is established, so as to analyze the flooding state of the stack, and through the automatic control of the nitrogen medium-pressure solenoid valve 40, the hydrogen medium-pressure solenoid valve 33 and the oxygen medium-pressure solenoid valve 23, the gas flow of the cathode and the anode is increased, and rapid water separation during operation is achieved to avoid system failure caused by flooding.

[0068] Specifically, the closed hydrogen and oxygen fuel cell system of the present embodiment includes a hydrogen and oxygen fuel cell stack 10, a voltage inspection 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 liquid level sensor 291, an oxygen low liquid level sensor 292, an oxygen drainage 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 liquid level sensor 391, a hydrogen low liquid level sensor 392, a hydrogen drainage 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, the outlet of the oxygen proportional valve 24 is connected to the inlet of the oxygen ejector 20, and the outlet of the oxygen ejector 20 is connected to the oxygen inlet of the hydrogen-oxygen fuel cell stack 10. The oxygen inlet temperature and pressure sensor 26 is placed at the oxygen inlet of the hydrogen-oxygen fuel cell stack 10, and can detect the pressure and temperature of the oxygen inlet stack. The inlet of the oxygen water separator 21 is connected to the oxygen outlet of the hydrogen-oxygen fuel cell stack 10, and the oxygen high liquid level sensor 291 and the oxygen low liquid level sensor 292 are respectively placed in the middle and lower parts of the oxygen water separator 21, for monitoring the content of liquid water in the oxygen water separator 21. The inlet of the oxygen water discharge solenoid valve 27 is connected to the lower part of the oxygen water separator 21, and the outlet of the oxygen water discharge solenoid valve 27 is connected to the oxygen water storage tank 22. The outlet of the oxygen water separator 21 is connected to the oxygen circulation solenoid valve 25. The hydrogen in oxygen sensor 28 is placed at the outlet of the oxygen water separator 21 to monitor the concentration of hydrogen permeated from the anode. The oxygen circulation solenoid valve 25 is connected to the reflux 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. The 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 the hydrogen inlet stack. The inlet of the hydrogen water separator 31 is connected to the hydrogen outlet of the hydrogen-oxygen fuel cell stack 10, and the hydrogen high liquid level sensor 391 and the hydrogen low liquid level sensor 392 are respectively placed in the middle and lower parts of the hydrogen water separator 31 to monitor the content of liquid water in the hydrogen water separator 31. The inlet of the hydrogen drainage solenoid valve 37 is connected to the lower part of the hydrogen water separator 31, the outlet of the hydrogen drainage solenoid valve 37 is connected to the hydrogen water storage tank 32, the outlet of the hydrogen water separator 31 is connected to the hydrogen circulation solenoid valve 35, and the oxygen sensor 38 in hydrogen is placed at the outlet of the hydrogen water separator 31 to monitor the concentration of oxygen permeating from the cathode. The hydrogen circulation solenoid valve 35 is connected to the reflux 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 proportion valve 24 through the first check valve 42; second, it is connected to the inlet of the hydrogen proportion valve 34 through the second check valve 43.

[0072] In order to achieve precise and autonomous control of the stack pressure, the oxygen gas circuit and the hydrogen gas circuit use the oxygen inlet temperature and pressure sensor 26 and the hydrogen inlet temperature and pressure sensor 36 as feedback quantities, and respectively use the oxygen proportional valve 24 and the hydrogen proportional valve 34 to perform closed-loop control on the stack pressure. In order to achieve effective drainage under closed conditions, a circulation and water separation scheme is required. The hydrogen gas circuit and the oxygen gas circuit respectively use the oxygen ejector 20 and the hydrogen ejector 30 to achieve the circulation of the oxygen gas circuit and the hydrogen gas circuit, thereby achieving the effect of effective water separation and improving the consistency of gas distribution; the hydrogen gas circuit and the oxygen gas circuit respectively use the hydrogen water separator 31 and the oxygen water separator 21 to achieve the separation and storage of liquid water, and respectively use the oxygen high liquid level sensor 291, the oxygen low liquid level sensor 292 and the hydrogen high liquid level sensor 391, the hydrogen low liquid level sensor 392 to accurately control the timing of the oxygen drainage solenoid valve 27 and the hydrogen drainage solenoid valve 37, thereby achieving effective discharge of liquid water and avoiding the decrease in utilization caused by excess discharge of gas. The oxygen gas circuit and the hydrogen gas circuit respectively use the oxygen-hydrogen sensor 28 and the hydrogen-oxygen sensor 38 to monitor the real-time hydrogen concentration on the cathode side and the oxygen concentration on the anode side, and through the real-time control of the oxygen drainage solenoid valve 27 and the hydrogen drainage solenoid valve 37, the hydrogen concentration and oxygen concentration of the cathode and anode are maintained within a safe threshold range and a high stack efficiency value. The oxygen circulation solenoid valve 25 and the hydrogen circulation solenoid valve 35 are used to control the on and off of the circulation circuit. In addition, the nitrogen medium pressure sensor 41 is used to monitor the pressure value of the nitrogen circuit, and the first one-way valve 42 and the second one-way valve 43 respectively play the role of one-way flow of the nitrogen circuit.

[0073] Figure 2 to Figure 7 Schematic diagram of the control method of the closed hydrogen-oxygen fuel cell system of this embodiment under different system operation modes. The control method under different system operation modes is as follows:

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

[0075] Secondly, the normal closed operation mode is the working mode of the closed hydrogen and oxygen fuel cell system for normal power generation. The gas flow path is as follows: Figure 3 As shown. In the normal working mode, taking the oxygen gas circuit as an example, the oxygen circulation solenoid valve 25 is opened, and oxygen enters the oxygen proportional valve 24 through the oxygen medium pressure solenoid valve 23. The oxygen inlet temperature and pressure sensor 26 is used as the feedback quantity, and the pressure of the hydrogen and 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, and the oxygen after the liquid water is removed by the oxygen water separator 21 enters the reflux port of the oxygen ejector 20 through the oxygen circulation solenoid valve 25. The combined oxygen enters the oxygen inlet of the hydrogen and oxygen fuel cell stack 10 through the oxygen ejector 20, and the reacted oxygen enters the oxygen circulation solenoid valve 25 after the liquid water is separated by the oxygen water separator 21, wherein the oxygen drainage solenoid valve 27 is closed, thereby realizing the closed-mouth operation of the system; the hydrogen gas circuit is the same as above.

[0076] Secondly, the closed hydrogen and oxygen fuel cell system has a water splitting mode during operation, and the gas flow path is as follows Figure 4 As shown. In the drainage mode during operation, taking the oxygen gas circuit as an example, the oxygen circulation solenoid valve 25 is opened, and the nitrogen passing through the nitrogen medium pressure solenoid valve 40 is mixed with the oxygen passing through the oxygen medium pressure solenoid valve 23 in a certain proportion, and then the nitrogen medium pressure solenoid valve 40 is closed, and the mixed gas enters the oxygen proportion valve 24. With the oxygen inlet temperature and pressure sensor 26 as the feedback quantity, the pressure of the hydrogen and oxygen fuel cell stack 10 is precisely controlled through closed-loop control. The oxygen proportion valve 24 enters the inlet of the oxygen ejector 20, and the mixed gas after the liquid water is removed by the oxygen water separator 21 enters the reflux port of the oxygen ejector 20 through the oxygen circulation solenoid valve 25. The mixed gas after the confluence enters the oxygen inlet of the hydrogen and oxygen fuel cell stack 10 through the oxygen ejector 20, and the reacted oxygen enters the oxygen circulation solenoid valve 25 after the liquid water is separated by the oxygen water separator 21. In addition, the oxygen drainage solenoid valve 27 is controlled by timing switch according to the effect of water separation to realize the effective discharge of nitrogen used for water separation; the hydrogen gas circuit is the same as above.

[0077] Secondly, the closed hydrogen and oxygen fuel cell system has a drainage mode during operation, and the gas flow path is as follows Figure 5As shown. In the drainage mode during operation, taking the oxygen gas circuit as an example, the oxygen circulation solenoid valve 25 is opened, and oxygen enters the oxygen proportional valve 24 through the oxygen medium pressure solenoid valve 23. The oxygen inlet temperature and pressure sensor 26 is used as the feedback quantity, and 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, and the oxygen after the liquid water is removed by the oxygen water separator 21 enters the reflux 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, and 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 performs sequential switch control according to the signal values ​​of the oxygen high liquid level sensor 291 and the oxygen low liquid level sensor 292, so as to maintain the liquid water in the oxygen water separator 21 near the low liquid level, thereby realizing the effective discharge of liquid water in the closed hydrogen-oxygen fuel cell system and achieving net zero emission; the hydrogen gas circuit is the same as above.

[0078] Then, in the purification mode during the operation of the closed hydrogen and oxygen fuel cell system, the gas flow path is as follows Figure 6 As shown. In the purification mode, taking the oxygen gas circuit as an example, oxygen enters the oxygen proportional valve 24 through the oxygen medium pressure solenoid valve 23, and the oxygen inlet temperature and pressure sensor 26 is used as the feedback quantity, and the pressure of the hydrogen and 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, the oxygen circulation solenoid valve 25 is closed, and the oxygen refluxes to the reflux port of the oxygen ejector 20, and the outlet of the oxygen ejector 20 enters the oxygen inlet of the hydrogen and oxygen fuel cell stack 10. The reacted oxygen passes through the oxygen water separator 21 and is discharged to the oxygen water storage tank 22 through the oxygen drainage solenoid valve 27. When the value of the oxygen hydrogen sensor 28 drops below the explosion limit or below the specified safety threshold, it enters the normal power generation working mode. By closing the circulation gas circuit and opening the oxygen drainage solenoid valve 27, the hydrogen concentration in the oxygen gas circuit is rapidly reduced, and the hydrogen concentration of the cathode is maintained within the safe threshold range and the high stack efficiency value, thereby improving the safety and efficiency of the system; the hydrogen gas circuit is the same as above.

[0079] Finally, in the shutdown purge mode of the closed hydrogen and oxygen fuel cell system, the gas flow path is as follows Figure 7As shown. In the shutdown purge mode, taking the oxygen gas circuit as an example, the oxygen medium-pressure solenoid valve 23 is closed, the nitrogen medium-pressure solenoid valve 40 is opened, and the 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, the oxygen circulation solenoid valve 25 is opened, and the nitrogen after the liquid water is removed by the oxygen water separator 21 enters the reflux port of the oxygen ejector 20 through the oxygen circulation solenoid valve 25, and the nitrogen after the confluence enters the oxygen inlet of the hydrogen-oxygen fuel cell stack 10 through the oxygen ejector 20. After the reacted nitrogen passes through the oxygen water separator 21, it is discharged to the oxygen water storage tank 22 through the oxygen drainage solenoid valve 27. The oxygen at the cathode is replaced and the liquid water is removed by nitrogen; the hydrogen gas circuit is the same as above. Through the above operation, the excessive pressure difference inside the system caused by the consumption of hydrogen and oxygen during the shutdown process and the performance damage caused by its hydrogen-air interface are avoided.

[0080] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and 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 present invention should be within the scope of protection of the present invention.

Claims

1. A closed hydrogen-oxygen fuel cell system, characterized in that: It comprises a hydrogen-oxygen fuel cell stack (10), an oxygen gas path, a hydrogen gas path and a nitrogen gas path; The oxygen gas circuit comprises 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 electromagnetic valve (25) is arranged between the two; the oxygen water separator (21) and the oxygen water storage tank (22) are connected 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 circuit is formed between the oxygen ejector (20), the oxygen water separator (21) and the hydrogen-oxygen fuel cell stack (10); the oxygen gas circuit also comprises an oxygen medium-pressure electromagnetic 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 circuit comprises 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 the two; 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 circuit is formed between the hydrogen ejector (30), the hydrogen water separator (31) and the hydrogen-oxygen fuel cell stack (10); the hydrogen gas circuit also comprises a hydrogen medium-pressure solenoid valve (33) and a hydrogen proportional valve (34) connected thereto, and the hydrogen proportional valve (34) is connected to the inlet of the hydrogen ejector (30); The nitrogen gas circuit comprises a nitrogen medium-pressure solenoid valve (40) and a nitrogen medium-pressure sensor (41), and 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 a nitrogen branch circuit respectively.

2. A closed hydrogen-oxygen fuel cell system according to claim 1, characterized in that: An oxygen inlet temperature and pressure sensor (26) is provided at the oxygen inlet of the hydrogen-oxygen fuel cell stack (10); A hydrogen inlet temperature and pressure sensor (36) is provided at the hydrogen inlet of the hydrogen-oxygen fuel cell stack (10).

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

4. A closed hydrogen-oxygen fuel cell system according to claim 1, characterized in that: A hydrogen-in-oxygen sensor (28) is provided at the outlet of the oxygen water separator (21); An oxygen-in-hydrogen sensor (38) is provided at the outlet of the hydrogen water separator (31).

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

6. A closed hydrogen-oxygen fuel cell system according to claim 1, characterized in that: The nitrogen medium-pressure solenoid valve (40) is connected to a nitrogen medium-pressure sensor (41), and the nitrogen is divided into two nitrogen branches after passing through the nitrogen medium-pressure sensor (41); A first one-way valve (42) is provided in one of the nitrogen branches and is connected to the inlet of the oxygen proportion valve (24), and a second one-way valve (43) is provided in the other nitrogen branch and is connected to the hydrogen proportion valve (34).

7. A control method for a closed hydrogen-oxygen fuel cell system according to any one of claims 1 to 6, characterized in that: The specific working modes include: S1 startup purge mode: close the nitrogen gas circuit; in the oxygen gas circuit, close the oxygen circulation solenoid valve (25), oxygen enters the hydrogen-oxygen fuel cell stack (10) through the oxygen ejector (20), and then discharges the residual liquid water into the oxygen water storage tank (22) through the oxygen water separator (21); then open the oxygen circulation solenoid valve (25), discharge the residual gas in the circulation branch to complete the purge; the same applies to the hydrogen gas circuit; S2 normal closed-end operation mode: the nitrogen gas circuit is closed; in the oxygen gas circuit, the oxygen circulation solenoid valve (25) is opened and the drainage pipeline is closed; oxygen enters the inlet of the oxygen ejector (20), returns to the reflux port of the oxygen ejector (20) after water separation in the circulation gas circuit and enters the hydrogen-oxygen fuel cell stack (10); the reacted oxygen enters the circulation gas circuit again after water separation, thus realizing the closed-end operation of the system; the same applies to the hydrogen gas circuit; S3 water separation mode: open the nitrogen gas circuit; in the oxygen gas circuit, open the oxygen circulation solenoid valve (25), and return the mixed gas of nitrogen and oxygen to the reflux port of the oxygen ejector (20) after water separation through the circulation gas circuit and enter the hydrogen-oxygen fuel cell stack (10); the oxygen after the reaction enters the circulation gas circuit again after water separation for closed-end operation; open the drainage pipeline to discharge the nitrogen used for water separation; the same applies to the hydrogen gas circuit; S4 drainage mode: close the nitrogen gas circuit; in the oxygen gas circuit, open the oxygen circulation solenoid valve (25) and perform closed-mouth operation in the S2 normal closed-mouth operation mode; open the drainage pipeline to achieve effective discharge of liquid water; the same applies to the hydrogen gas circuit; S5 purification mode: close the nitrogen gas circuit; in the oxygen gas circuit, close the oxygen circulation solenoid valve (25), oxygen enters the hydrogen-oxygen fuel cell stack (10) through the oxygen ejector (20), and then discharges liquid water into the oxygen water storage tank (22) through the oxygen water separator (21); wait until the hydrogen concentration drops to a safe range, then enter the S2 normal closed-mouth operation mode; the same applies to the hydrogen gas circuit; S6 shutdown purge mode: open the nitrogen gas circuit; in the oxygen gas circuit, close the oxygen input, open the oxygen circulation solenoid valve (25), and the nitrogen is operated in a closed-mouth operation mode of S2 normal closed-mouth operation; open the drainage pipeline to discharge nitrogen and residual liquid water; the same applies to the hydrogen gas circuit.

8. The control method of a closed hydrogen-oxygen fuel cell system according to claim 7, characterized in that: In the S2 normal closed-mouth operation mode, the S3 water separation mode, the S4 drainage mode and the 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 and oxygen fuel cell stack (10) through closed-loop control.

9. The control method of a closed hydrogen-oxygen fuel cell system according to claim 7, characterized in that: In the S4 drainage mode, the oxygen high liquid level sensor (291) and the oxygen low liquid level sensor (292) are used as the basis for timing switch control to maintain the liquid water in the oxygen water separator (21) at a low liquid level; the same applies to the hydrogen water separator (31).

10. The control method of a closed hydrogen-oxygen fuel cell system according to claim 7, characterized in that: In the S5 purification mode, the hydrogen-in-oxygen sensor (28) and the 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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