Humidification system and humidification method for fuel cells

Abstract

Provided in the present application are a humidification system and humidification method for fuel cells. The humidification system comprises a fuel cell stack, a first pressure-reducing valve, a gas-liquid separator, a first switching valve, a second switching valve, a liquid storage tank, a third switching valve, a fourth switching valve, a second pressure-reducing valve, an atomizer and at least one liquid level sensor, wherein a detection end of the liquid level sensor is located in the liquid storage tank.

Description

Humidification system and humidification method for fuel cell

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on June 27, 2023, with application number 202310762126.1, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of hydrogen fuel cell technology, for example, to a humidification system and a humidification method for a fuel cell. Background Art

[0003] Fuel cell vehicles, with their fast refueling, long range, and low-temperature resistance, have emerged alongside pure electric vehicles as a solution to future zero-emissions challenges. In recent years, they have garnered widespread attention from major countries and companies. As the core assembly of a fuel cell vehicle, the fuel cell system provides the required power and typically consists of a fuel cell stack, air supply subsystem, hydrogen supply subsystem, thermal management subsystem, and electrical and electronic subsystems.

[0004] The fuel cell stack is the place where substances undergo electrochemical reactions. Its working principle is as follows: hydrogen enters the anode, reaches the surface of the anode catalyst through diffusion, and decomposes into positively charged protons (H + ) and negatively charged electrons (e - ), protons, carried by water, cross the proton exchange membrane to the cathode, while electrons flow through the external circuit through the load to the cathode. Simultaneously, oxygen (O2) diffuses to the surface of the cathode catalyst. Under the action of the cathode catalyst, electrons, protons, and oxygen undergo an oxygen reduction reaction (ORR) to produce water and energy.

[0005] During the reaction process, controlling the water balance within the stack is a core technology for fuel cells. Proton conductivity is closely related to the water content of the membrane. Excessive water content within the stack can cause flooding, while insufficient water content can lead to membrane dryness. Related technologies consider using water generated in real time by electrochemical reactions, using a self-humidification solution with a cathode-side humidifier or a self-humidification solution with hydrogen circulation on the anode side. However, the humidified water is not decoupled from the stack power. The water production in the low-power range is too low to meet the membrane water content requirements, while the water production in the high-power range requires a faster tail discharge frequency, and the self-generated water is not effectively utilized.

[0006] The solution in the related technology is to use the air path for active humidification, and humidify the gas in the air path by means of air compressor pressurization, heating by a heating device or water pumping. These methods will generate additional parasitic power for the system. At the same time, they do not fully utilize the water discharged from the anode, resulting in energy waste.

[0007] Summary of the Invention

[0008] The present application provides a humidification system and humidification method for a fuel cell, which can achieve effective control of the humidification and dehumidification of the fuel gas and the fuel gas concentration in the fuel cell stack without adding additional auxiliary system power consumption.

[0009] The present application provides a humidification system for a fuel cell, comprising a fuel cell stack, a first pressure reducing valve, a gas-liquid separator, a first switch valve, a second switch valve, a liquid storage tank, a third switch valve, a fourth switch valve, a second pressure reducing valve, an atomizer, and at least one liquid level sensor, wherein a detection end of the at least one liquid level sensor is located in the liquid storage tank;

[0010] The high-pressure air inlet of the humidification system is connected to the first port of the first pressure-reducing valve and the first port of the second pressure-reducing valve respectively, the second port of the first pressure-reducing valve is connected to the air inlet of the fuel cell stack, the exhaust port of the fuel cell stack is connected to the air inlet of the gas-liquid separator, the air outlet of the gas-liquid separator is connected to the first port of the first switching valve, the second port of the first switching valve is connected to the air outlet of the humidification system, the water outlet of the gas-liquid separator is connected to the first port of the second switching valve, the second port of the second switching valve is connected to the air inlet of the liquid storage tank, the first water outlet of the liquid storage tank is connected to the first port of the third switching valve, the second water outlet of the liquid storage tank is connected to the first port of the fourth switching valve, the second port of the fourth switching valve is connected to the water inlet of the atomizer, the air inlet of the atomizer is connected to the second port of the second pressure-reducing valve, and the air outlet of the atomizer is connected to the air inlet of the fuel cell stack.

[0011] Optionally, an ejector is also included, wherein the first port of the ejector is connected to the second port of the first pressure reducing valve, the second port of the ejector is connected to the air inlet of the fuel cell stack, and the third port of the ejector is connected to the air outlet of the gas-liquid separator.

[0012] Optionally, it also includes a stack state detection device, which includes an impedance detector; the stack state detection device is arranged inside the fuel cell stack or outside the fuel cell stack, and is configured to detect the stack state of the fuel cell stack.

[0013] Optionally, it further comprises at least one gas concentration sensor, wherein a detection end of the at least one gas concentration sensor is located inside the fuel cell stack;

[0014] Wherein, the at least one gas concentration sensor includes at least a hydrogen concentration sensor, and the hydrogen concentration sensor is configured to detect the hydrogen concentration inside the fuel cell stack.

[0015] Optionally, a controller is further included, which is respectively connected to the fuel cell stack, the first pressure reducing valve, the first switch valve, the second switch valve, the third switch valve, the fourth switch valve, the second pressure reducing valve, the atomizer and the liquid level sensor.

[0016] The present application also provides a humidification method for a fuel cell, the humidification method comprising:

[0017] Obtaining the gas flow required by the fuel cell stack;

[0018] controlling the proportional opening of the first pressure reducing valve and the second pressure reducing valve according to the required gas flow rate;

[0019] Obtain the detected water level in the liquid storage tank;

[0020] The atomization state of the atomizer is controlled according to the magnitude relationship between the detected water level and the standard water level.

[0021] Optionally, the standard water level includes a first water level and a second water level, and the first water level is lower than the second water level;

[0022] According to the relationship between the detected water level and the standard water level, the atomization state of the atomizer is controlled, including:

[0023] When the detected water level is greater than or equal to the second water level, the third switch valve and the fourth switch valve are controlled to be opened, and the atomizer is controlled to be opened;

[0024] When the detected water level is less than or equal to the first water level, the third switch valve and the fourth switch valve are controlled to be closed, and the atomizer is controlled to be closed;

[0025] When the first water level is less than the detected water level and less than the second water level, the third switch valve is controlled to be closed, the fourth switch valve is controlled to be opened, and the atomizer is controlled to be turned on.

[0026] Optionally, the humidification method includes:

[0027] When the detected water level is greater than or equal to the second water level, controlling the third switch valve to be continuously opened for the first time;

[0028] When the detected water level is less than or equal to the first water level, controlling the fourth switch valve to remain closed for a second time;

[0029] The first time and the second time are calibration values.

[0030] Optionally, when the first water level is less than the detected water level and less than the second water level, the humidification method further includes:

[0031] Determining the current state of the fuel cell stack;

[0032] When the fuel cell stack is in a membrane dry state, the fourth switch valve is controlled to open, and the opening of the second switch valve is adjusted to control the flow rate of the humidified gas output from the gas outlet of the atomizer;

[0033] When the fuel cell stack is in a flooded state, the fourth switch valve is controlled to be closed, and the opening of the second switch valve is adjusted to control the flow rate of the dry gas output from the gas outlet of the atomizer.

[0034] Optionally, when the first water level is less than the detected water level and less than the second water level, the humidification method further includes:

[0035] Obtaining hydrogen concentration in the fuel cell stack;

[0036] According to the relationship between the hydrogen concentration and the standard concentration, the proportional openings of the first pressure reducing valve and the second pressure reducing valve are controlled to control the gas concentration in the fuel cell stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG1 is a schematic diagram of a humidification system for a fuel cell provided by the present application;

[0038] FIG2 is a schematic diagram of another fuel cell humidification system provided by the present application;

[0039] FIG3 is a schematic diagram of another fuel cell humidification system provided by the present application;

[0040] FIG4 is a schematic diagram of a fuel cell humidification method provided by the present application;

[0041] FIG5 is a schematic diagram of another fuel cell humidification method provided in the present application.

[0042] Among them, the accompanying drawings are described as follows: 100-fuel cell stack; 1-first pressure reducing valve; 2-gas-liquid separator; 3-first switch valve; 4-second switch valve; 5-liquid storage tank; 6-third switch valve; 7-fourth switch valve; 8-second pressure reducing valve; 9-atomizer; 10-liquid level sensor; 11-ejector; 12-gas concentration sensor; 13-stack state detection device; 14-controller. DETAILED DESCRIPTION

[0043] The present application is described below in conjunction with the accompanying drawings and embodiments. The embodiments described herein are intended only to explain the present application and are not intended to limit the present application. For ease of description, the accompanying drawings only show portions related to the present application, not all structures.

[0044] In view of one or more of the above problems, the present application proposes a humidification system for a fuel cell. FIG1 is a schematic diagram of a humidification system for a fuel cell provided by the present application.

[0045] As shown in Figure 1, the humidification system of the fuel cell provided in the present application includes a fuel cell stack 100, a first pressure reducing valve 1, a gas-liquid separator 2, a first switch valve 3, a second switch valve 4, a liquid storage tank 5, a third switch valve 6, a fourth switch valve 7, a second pressure reducing valve 8, an atomizer 9 and at least one liquid level sensor 10, and the detection end of the liquid level sensor 10 is located in the liquid storage tank 5; the high-pressure air inlet A0 of the humidification system is respectively connected to the first port of the first pressure reducing valve 1 and the first port of the second pressure reducing valve 8, the second port of the first pressure reducing valve 1 is connected to the air inlet B0 of the fuel cell stack 100, and the exhaust port B1 of the fuel cell stack 100 is connected to the air inlet of the gas-liquid separator 2 The air outlet of the gas-liquid separator 2 is connected to the first port of the first switch valve 3, and the second port of the first switch valve 3 is connected to the air outlet A1 of the humidification system; the water outlet of the gas-liquid separator 2 is connected to the first port of the second switch valve 4, the second port of the second switch valve 4 is connected to the air inlet of the liquid storage tank 5, the first water outlet of the liquid storage tank 5 is connected to the first port of the third switch valve 6, the second water outlet of the liquid storage tank 5 is connected to the first port of the fourth switch valve 7, the second port of the fourth switch valve 7 is connected to the water inlet of the atomizer 9, the air inlet of the atomizer 9 is connected to the second port of the second pressure reducing valve 8, and the air outlet of the atomizer 9 is connected to the air inlet B0 of the fuel cell stack 100.

[0046] As shown in FIG1 , the high-pressure air inlet A0 of the humidification system can continuously provide high-pressure hydrogen fuel, and the fuel cell stack 100 is the site of the hydrogen-oxygen electrochemical reaction.

[0047] The hydrogen supply pressure of the fuel cell stack 100 can be adjusted by adjusting the opening of the first pressure-reducing valve 1 on the main channel of the fuel cell stack 100's air inlet B0. The larger the opening, the greater the degree of opening of the pressure-reducing valve, and the higher the hydrogen supply pressure. A gas-liquid separator 2 is configured to separate liquid water and mixed gas discharged from the exhaust port B1 of the fuel cell stack 100. A first on-off valve 3 is configured to control the discharge of impurities such as nitrogen from the humidification system's outlet A1. A second on-off valve 4 is configured to control the discharge of liquid water in the gas-liquid separator 2 into a liquid storage tank 5. The liquid storage tank 5 is configured to store liquid water discharged from the anode of the fuel cell stack 100. A third on-off valve 6 is configured to control the discharge of excess liquid water in the liquid storage tank 5. A fourth on-off valve 7 is configured to supply liquid water to the atomizer 9.

[0048] By adjusting the opening of the second pressure reducing valve 8 on the humidification channel of the air inlet B0 of the fuel cell stack 100, the pressure of the hydrogen supply to the atomizer 9 can be adjusted. The high-pressure hydrogen fuel enters the atomizer 9 after being reduced in pressure and increased in speed by the second pressure reducing valve 8. Driven by the high-pressure hydrogen, the atomizer 9 can automatically extract liquid water from the liquid storage tank 5. The atomizer 9 atomizes the inhaled liquid water, and the humidified hydrogen enters the air inlet B0 of the fuel cell stack 100, providing humidified fuel gas to the fuel cell stack 100, thereby realizing the decoupling of the stack power and humidification.

[0049] A pressure reducing valve, among other things, reduces the inlet pressure to a desired outlet pressure and automatically maintains a stable outlet pressure by relying on the energy of the medium itself. From a fluid mechanics perspective, a pressure reducing valve is a throttling element with variable local resistance. This means that by varying the throttling area, the flow rate and kinetic energy of the fluid are altered, resulting in varying pressure losses, thereby achieving pressure reduction. The control and regulation system balances pressure fluctuations downstream of the valve with the spring force, maintaining a constant pressure within a certain tolerance.

[0050] The on-off valve refers to a valve-like switch, such as a faucet, a pressure cooker valve, etc., which has a shut-off function. The on-off valve is divided into a pneumatic on-off valve and an electric on-off valve. As an example, the present application can use an electric on-off valve.

[0051] The gas-liquid separator 2 is a separation device that uses centrifugal separation and screen filtration to remove liquids. It consists of a cylinder, a cyclone separator, a high-efficiency foam separator, and a drain valve. It is typically installed before the drying unit to perform coarse filtration and remove some moisture from the air, reducing the drying unit's workload.

[0052] Liquid level sensor 10 is located within liquid storage tank 5 and is configured to detect the liquid level within liquid storage tank 5. Liquid level sensor 10, which can also be referred to as a static pressure level gauge, liquid level transmitter, liquid level sensor, or water level sensor, is a pressure sensor for measuring liquid level. It operates on the principle that the static pressure of the measured liquid is proportional to the height of the liquid. It utilizes an isolated diffused silicon sensor or a ceramic capacitor pressure sensor to convert the static pressure into an electrical signal. This signal is then converted, through temperature compensation and linearity correction, into a standard electrical signal (typically 4-20 mA, direct current (DC): 1-5 V). This sensor is suitable for measuring the liquid level of various media in systems and industries such as petrochemicals, metallurgy, electricity, pharmaceuticals, water supply and drainage, and environmental protection.

[0053] The present application utilizes a liquid level sensor 10 to detect the liquid water level in the liquid storage tank 5, detects the liquid water level in the liquid storage tank 5 at all times, and then automatically controls the liquid water level in the liquid storage tank 5 in real time to ensure the supply of water to the atomizer 9 on the humidification channel of the air inlet B0 of the fuel cell stack 100, and to ensure the control of the humidification and dehumidification of the fuel gas in the fuel cell stack 100.

[0054] In summary, the humidification system of the fuel cell provided in the present application collects the water discharged from the exhaust port of the fuel cell stack as the basic medium for humidification, automatically extracts water from the water tank based on an atomizer driven by high-pressure hydrogen, and adjusts the proportional opening of the pressure reducing valve on the main channel of the air inlet of the fuel cell stack and the pressure reducing valve on the humidification channel. Under the premise of not adding additional auxiliary system power consumption, effective control of the humidification, dehumidification and fuel gas concentration of the fuel cell stack can be achieved.

[0055] FIG2 is a schematic diagram of another fuel cell humidification system provided in the present application.

[0056] On the basis of the above embodiments, in combination with Figure 2, the humidification system of the fuel cell provided in the embodiment of the present application also includes an ejector 11, the first port of the ejector 11 is connected to the second port of the first pressure reducing valve 1, the second port of the ejector 11 is connected to the air inlet B0 of the fuel cell stack 100, and the third port of the ejector 11 is connected to the air outlet of the gas-liquid separator 2.

[0057] For example, the ejector 11 utilizes the high-pressure, high-speed, high-energy fuel gas output from the second port of the first pressure reducing valve 1 to inject the unreacted mixed gas from the outlet of the gas-liquid separator 2 back into the air inlet B0 of the fuel cell stack 100, thereby allowing the unreacted mixed gas to be reused, improving the conversion efficiency of the fuel gas and saving energy.

[0058] FIG3 is a schematic diagram of another fuel cell humidification system provided in the present application.

[0059] On the basis of the above embodiments, in combination with Figure 3, the humidification system of the fuel cell provided in the embodiment of the present application also includes at least one gas concentration sensor 12, and the detection end of the gas concentration sensor 12 is located inside the fuel cell stack 100; wherein, the gas concentration sensor 12 includes at least a hydrogen concentration sensor, and the hydrogen concentration sensor is configured to detect the hydrogen concentration inside the fuel cell stack 100.

[0060] Illustratively, the gas concentration sensor 12 may be disposed inside the fuel cell stack 100 or outside the fuel cell stack 100 , which is not limited here.

[0061] As an example, the gas concentration sensor 12 is used to detect the concentration of gases such as hydrogen, oxygen, and nitrogen inside the fuel cell stack 100. The hydrogen concentration sensor is used to detect the hydrogen concentration inside the fuel cell stack 100. Under the premise that the hydrogen concentration meets the use requirements of the fuel cell stack, the proportional opening of the pressure reducing valve on the main channel of the air inlet B0 of the fuel cell stack 100 and the pressure reducing valve on the humidification channel are adjusted to reduce the backflow of impurity gases, restore the gas concentration of the fuel cell stack to normal, and achieve decoupling of the stack power and humidification.

[0062] On the basis of the above embodiments, in combination with Figures 1 to 4 , the humidification system for the fuel cell provided in the embodiment of the present application also includes a stack state detection device 13 , which includes an impedance detector; the stack state detection device 13 is configured to detect the stack state of the fuel cell stack 100 .

[0063] Illustratively, the stack state detection device 13 may be disposed inside the fuel cell stack 100 or outside the fuel cell stack 100 , which is not limited here.

[0064] As an example, the stack state detection device 13 is an impedance detector, which determines the stack state of the fuel cell stack 100 at a current moment by detecting the impedance value of the fuel cell stack 100 .

[0065] On the basis of the above embodiments, and in combination with Figures 1 to 3, the humidification system of the fuel cell provided in the embodiment of the present application also includes a controller 14. In Figure 1, the controller 14 is respectively connected to the fuel cell stack 100, the first pressure reducing valve 1, the first switch valve 3, the second switch valve 4, the third switch valve 6, the fourth switch valve 7, the second pressure reducing valve 8, the atomizer 9 and the liquid level sensor 10.

[0066] The controller 14 includes a general-purpose processor, such as a microprocessor or any conventional processor. The controller 14 is configured to control the opening of the first pressure-reducing valve 1 and the second pressure-reducing valve 8 , and to control the opening and closing of the first on / off valve 3 , the second on / off valve 4 , the third on / off valve 6 , the fourth on / off valve 7 , the atomizer 9 , and the ejector 11 . Furthermore, the controller 14 is configured to receive the liquid level within the liquid storage tank 5 as detected by the liquid level sensor 10 and to analyze the received liquid level.

[0067] In Figure 2, the controller 14 is respectively connected to the fuel cell stack 100, the first pressure reducing valve 1, the first switch valve 3, the second switch valve 4, the third switch valve 6, the fourth switch valve 7, the second pressure reducing valve 8, the atomizer 9, the liquid level sensor 10 and the ejector 11; in Figure 3, the controller 14 is respectively connected to the fuel cell stack 100, the first pressure reducing valve 1, the first switch valve 3, the second switch valve 4, the third switch valve 6, the fourth switch valve 7, the second pressure reducing valve 8, the atomizer 9, the liquid level sensor 10, the ejector 11, the gas concentration sensor 12 and the stack state detection device 13.

[0068] Exemplarily, the controller 14 can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof.

[0069] Based on the same concept, embodiments of the present application also provide a fuel cell humidification method for controlling the humidification system provided in the above embodiments. Figure 4 is a schematic diagram of a fuel cell humidification method provided in the present application. Combined with Figures 1 to 4, the fuel cell humidification method provided in the present application includes the following steps.

[0070] S101. Obtain the gas flow required by the fuel cell stack.

[0071] S102: Control the proportional opening of the first pressure reducing valve and the second pressure reducing valve according to the required gas flow rate.

[0072] As shown in Figures 1 to 4 , the controller 14 of the humidification system obtains the gas flow required by the fuel cell stack 100 at the current moment. It controls the hydrogen supply pressure to the main channel at the fuel cell stack 100's inlet B0 by adjusting the opening of the first pressure-reducing valve 1. It also controls the hydrogen supply pressure to the humidification channel at the inlet B0 of the fuel cell stack 100 by adjusting the opening of the second pressure-reducing valve 8. Based on the current gas flow required by the fuel cell stack 100, the proportional openings of the first and second pressure-reducing valves 1 and 8 are appropriately adjusted. This not only controls the gas flow within the fuel cell stack 100, thereby ensuring that the gas concentration at the inlet B0 of the fuel cell stack 100 meets the current fuel cell stack demand, but also utilizes high-pressure gas to discharge excess moisture from the fuel cell stack 100 through the exhaust port B1 of the fuel cell stack 100, thereby dehumidifying the fuel cell stack 100. This system also eliminates the need for additional auxiliary system power consumption, resulting in a low cost advantage.

[0073] S103: Obtain the detected water level in the liquid storage tank.

[0074] S104: Control the atomization state of the atomizer according to the relationship between the detected water level and the standard water level.

[0075] Illustratively, the liquid level sensor 10 monitors the water level of the liquid water in the liquid tank 5 in real time and transmits the acquired detected water level to the controller 14 . The liquid water in the liquid tank 5 is discharged from the anode of the fuel cell stack 100 .

[0076] The controller 14 compares the detected water level with the stored standard water level, controls the start or shut down of the third switch valve 6 and the fourth switch valve 7 as well as the atomizer 9, and utilizes the high-pressure gas on the channel of the second pressure reducing valve 8 and is driven by high-pressure hydrogen to automatically extract liquid water from the liquid storage tank 5.

[0077] When the atomizer 9 is started, the inhaled liquid water can be atomized, and the humidified hydrogen gas can enter the air inlet B0 of the fuel cell stack 100 under the drive of high voltage, providing the humidified fuel gas to the fuel cell stack 100, thereby humidifying the fuel cell stack 100. This application controls the proportional opening of the first pressure reducing valve 1 and the second pressure reducing valve 8 and the atomization state of the atomizer 9, thereby achieving control of the humidification and dehumidification of the fuel cell stack and the gas concentration without adding additional auxiliary system power consumption, thereby achieving decoupling of the fuel cell stack power and humidification.

[0078] FIG5 is a schematic diagram of another fuel cell humidification method provided in the present application.

[0079] Based on the above embodiment, the standard water level includes a first water level and a second water level, with the first water level being lower than the second water level. The first water level is lower than the second water level. As an example, the first water level is 20% of the full level of the liquid storage tank, and the second water level is 80% of the full level of the liquid storage tank. In step 104, as shown in Figures 1 to 5 , the humidification method provided in this application includes the following steps.

[0080] S1. When the detected water level is ≥ the second water level, the third switch valve and the fourth switch valve are controlled to be opened, and the atomizer is controlled to be opened.

[0081] Exemplarily, when the detected liquid water level in the liquid storage tank 5 is greater than or equal to the second water level (80%), it indicates that the liquid storage tank 5 is close to the full water level and the third switch valve 6 needs to be opened. As an example, the third switch valve 6 is controlled to be continuously opened for the first time t1 to remove excess liquid water; the fourth switch valve 7 is opened to allow liquid water to enter the atomizer 9; the atomizer 9 is opened to atomize the liquid water, and then the high-pressure gas input into the channel of the second pressure reducing valve 8 is humidified and input from the air inlet B0 of the fuel cell stack 100.

[0082] S2. When the detected water level is less than or equal to the first water level, the third switch valve and the fourth switch valve are controlled to be closed, and the atomizer is controlled to be closed.

[0083] Exemplarily, when the monitored liquid water level in the liquid storage tank 5 is less than or equal to the first water level (20%), it indicates that the liquid storage tank 5 is at a low water level, and the third switch valve 6 needs to be closed to prevent the liquid water from being discharged, while controlling the fourth switch valve 7 and the atomizer 9 to be closed. As an example, the fourth switch valve 7 is controlled to be closed continuously for the second time t2 to prevent the atomizer 9 from atomizing. The gas flow rate of the air inlet B0 of the fuel cell stack 100 is adjusted by the proportional opening of the first pressure reducing valve 1 and the second pressure reducing valve 8, and the excess moisture of the fuel cell stack 100 is removed from the exhaust port B1 of the fuel cell stack 100 by high-pressure gas, thereby achieving dehumidification of the fuel cell stack 100. Among them, the larger the proportional opening, the greater the degree of opening of the switch valve, and the greater the gas flow rate.

[0084] The first time t1 and the second time t2 are calibration values. For example, the first time t1 can be 1 minute, and the second time t2 can be 2 minutes. The specific time can be set according to the water level of the liquid storage tank 5.

[0085] S3. When the first water level is less than the detected water level and less than the second water level, the third switch valve is controlled to be closed, the fourth switch valve is controlled to be opened, and the atomizer is controlled to be turned on.

[0086] For example, when the monitored liquid water level in the liquid storage tank 5 is between the first water level (20%) and the second water level (80%), it means that the liquid water level in the liquid storage tank 5 is moderate at this time, and the third switch valve 6 needs to be closed to prevent the liquid water from being discharged. At the same time, the fourth switch valve 7 and the atomizer 9 are controlled to open. The high-pressure gas in the channel of the second pressure reducing valve 8 is used and driven by high-pressure hydrogen. The atomizer 9 automatically extracts liquid water from the liquid storage tank 5. After the liquid water is atomized, the high-pressure gas input from the channel of the second pressure reducing valve 8 is humidified, and then input from the air inlet B0 of the fuel cell stack 100 to achieve humidification of the fuel cell stack 100.

[0087] Based on the above embodiment, in step S3, when the first water level < the detected water level < the second water level, the humidification method further includes the following steps.

[0088] S31. Determine the stack status of the fuel cell stack.

[0089] Exemplarily, the stack state detection device 13 is used to detect the stack state of the fuel cell stack 100. The stack state includes a membrane dry state, a water flooded state, and a water balance state.

[0090] As an example, in combination with FIG. 1 to FIG. 3 , the stack state detection device 13 is an impedance detector, which determines the stack state of the fuel cell stack 100 at the current moment by detecting the impedance value of the fuel cell stack 100 .

[0091] S32. When the fuel cell stack is in a membrane dry state, the fourth switch valve is controlled to open, and the opening of the second switch valve is adjusted to control the flow rate of the humidified gas output from the gas outlet of the atomizer.

[0092] For example, in combination with Figures 1 to 3, when the stack state detection device 13 detects that the current stack state of the fuel cell stack 100 is a membrane dry state, it means that the water content inside the fuel cell stack 100 is insufficient, which may easily lead to membrane dry failure. Therefore, the controller 14 automatically controls the fourth switch valve 7 to open, the atomizer 9 to start, and at the same time adjusts the opening of the second pressure reducing valve 8 to control the flow rate of humidified gas output from the outlet of the atomizer 9, so that the stack returns to a normal water balance state.

[0093] Among them, the water balance state means that the water content inside the fuel cell stack reaches the expected value, which can achieve the decoupling of fuel cell stack power and humidification.

[0094] S33. When the fuel cell stack is in a flooded state, the fourth switch valve is controlled to be closed, and the opening of the second switch valve is adjusted to control the flow rate of the dry gas output from the gas outlet of the atomizer.

[0095] As shown in Figure 3, when the stack state detection device 13 detects that the current stack state of the fuel cell stack 100 is a flooded state, it means that the water content inside the fuel cell stack 100 is too high and a flooding fault occurs. Therefore, the controller 14 automatically controls the fourth switch valve 7 to close, preventing liquid water from entering the atomizer 9, and at the same time adjusts the opening of the second pressure reducing valve 8 to control the flow rate of dry gas output from the outlet of the atomizer 9, so that the stack returns to a normal water balance state.

[0096] Based on the above embodiment, in step S3, when the first water level < the detected water level < the second water level, the humidification method further includes the following steps.

[0097] S34. Obtain the hydrogen concentration in the fuel cell stack.

[0098] S35. Control the proportional openings of the first pressure reducing valve and the second pressure reducing valve according to the relationship between the hydrogen concentration and the standard concentration, so as to control the gas concentration in the fuel cell stack.

[0099] For example, in combination with Figures 2 and 3, a hydrogen concentration sensor is used to detect the hydrogen concentration inside the fuel cell stack 100 in real time. On the premise that the hydrogen concentration meets the use requirements of the stack, the proportional opening of the pressure reducing valve on the main channel of the air inlet B0 of the fuel cell stack 100 and the pressure reducing valve on the humidification channel can be adjusted to reduce the backflow of impurity gas, thereby controlling the gas concentration inside the fuel cell stack 100.

[0100] As an example, when the concentration of impurity gas inside the fuel cell stack 100 is high, the opening of the first pressure reducing valve 1 can be appropriately reduced, while the opening of the second pressure reducing valve 8 can be increased, thereby reducing the gas flow on the main channel of the air inlet B0 of the fuel cell stack and increasing the gas flow on the humidification channel of the air inlet B0 of the fuel cell stack. This humidifies the inside of the fuel cell stack 100 and improves the decoupling efficiency of the stack power and humidification, thereby reducing the reflux of impurity gas from the ejector 11 to the inside of the fuel cell stack 100, allowing the stack to restore normal gas concentration.

[0101] As shown in Figures 1 to 3, during the reaction process of the fuel cell stack 100, the first switch valve 3 is opened to allow impurity gases such as nitrogen to be discharged from the outlet A1 of the humidification system; the second switch valve 4 is opened to control the liquid water in the gas-liquid separator 2 to be discharged into the liquid storage tank 5.

[0102] In summary, the fuel cell humidification method provided in this application, through the joint control of multiple proportional valves and switch valves, realizes effective control of the humidification, dehumidification and fuel gas concentration of the fuel gas in the fuel cell stack without adding additional auxiliary system power consumption.

Claims

1. A humidification system for a fuel cell, comprising a fuel cell stack, a first pressure reducing valve, a gas-liquid separator, a first switch valve, a second switch valve, a liquid storage tank, a third switch valve, a fourth switch valve, a second pressure reducing valve, an atomizer and at least one liquid level sensor, wherein a detection end of the at least one liquid level sensor is located in the liquid storage tank; The high-pressure air inlet of the humidification system is connected to the first port of the first pressure reducing valve and the first port of the second pressure reducing valve respectively, the second port of the first pressure reducing valve is connected to the air inlet of the fuel cell stack, the exhaust port of the fuel cell stack is connected to the air inlet of the gas-liquid separator, the air outlet of the gas-liquid separator is connected to the first port of the first switch valve, the second port of the first switch valve is connected to the air outlet of the humidification system, the water outlet of the gas-liquid separator is connected to the first port of the second switch valve, the second port of the second switch valve is connected to the air inlet of the liquid storage tank, the first water outlet of the liquid storage tank is connected to the first port of the third switch valve, the second water outlet of the liquid storage tank is connected to the first port of the fourth switch valve, the second port of the fourth switch valve is connected to the water inlet of the atomizer, the air inlet of the atomizer is connected to the second port of the second pressure reducing valve, and the air outlet of the atomizer is connected to the air inlet of the fuel cell stack.

2. The system according to claim 1 further includes an ejector, a first port of the ejector is connected to the second port of the first pressure reducing valve, a second port of the ejector is connected to the air inlet of the fuel cell stack, and a third port of the ejector is connected to the air outlet of the gas-liquid separator.

3. The system according to claim 1, further comprising a battery stack state detection device, wherein the battery stack state detection device comprises an impedance detector; The stack state detection device is disposed inside the fuel cell stack or outside the fuel cell stack, and is configured to detect the stack state of the fuel cell stack.

4. The system according to claim 1, further comprising at least one gas concentration sensor, wherein a detection end of the at least one gas concentration sensor is located inside the fuel cell stack; in, The at least one gas concentration sensor includes a hydrogen concentration sensor configured to detect a hydrogen concentration inside the fuel cell stack.

5. The system according to claim 1 further includes a controller, which is respectively connected to the fuel cell stack, the first pressure reducing valve, the first switch valve, the second switch valve, the third switch valve, the fourth switch valve, the second pressure reducing valve, the atomizer and the at least one liquid level sensor.

6. A method for humidifying a fuel cell, comprising: Obtaining the gas flow required by the fuel cell stack; According to the required gas flow, controlling the proportional opening of the first pressure reducing valve and the second pressure reducing valve; Obtaining the detected water level in the liquid storage tank; The atomization state of the atomizer is controlled according to the magnitude relationship between the detected water level and the standard water level.

7. The method according to claim 6, wherein: The standard water level includes a first water level and a second water level, wherein the first water level is lower than the second water level; The controlling the atomization state of the atomizer according to the magnitude relationship between the detected water level and the standard water level comprises: When the detected water level is greater than or equal to the second water level, the third switch valve and the fourth switch valve are controlled to be opened, and the atomizer is controlled to be opened; When the detected water level is less than or equal to the first water level, the third switch valve and the fourth switch valve are controlled to be closed, and the atomizer is controlled to be closed; When the first water level is less than the detected water level and less than the second water level, the third switch valve is controlled to be closed, the fourth switch valve is controlled to be opened, and the atomizer is controlled to be opened.

8. The method according to claim 7, wherein: The method further comprises: When the detected water level is greater than or equal to the second water level, controlling the third switch valve to be continuously opened for a first time; When the detected water level is less than or equal to the first water level, controlling the fourth switch valve to be closed continuously for a second time; The first time and the second time are calibration values.

9. The method according to claim 7, wherein: In the case where the first water level is less than the detected water level and less than the second water level, the method further includes: Determine the current fuel cell stack status; When the current fuel cell stack state is a membrane dry state, the fourth switch valve is controlled to open, and the opening of the second switch valve is adjusted to control the flow rate of humidified gas output from the gas outlet of the atomizer; When the fuel cell stack is in a flooded state, the fourth switch valve is controlled to be closed, and the opening of the second switch valve is adjusted to control the flow rate of dry gas output from the gas outlet of the atomizer.

10. The method according to claim 8, wherein: In the case where the first water level is less than the detected water level and less than the second water level, the method further includes: Obtaining the hydrogen concentration in the fuel cell stack; According to the relationship between the hydrogen concentration and the standard concentration, the first pressure reducing valve and the first pressure reducing valve are controlled. The proportional opening of the second pressure reducing valve is used to control the gas concentration in the fuel cell stack.

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