Air-cooled proton exchange membrane fuel cell (PEMFC) water thermal management method

Abstract

The application provides a hydrothermal management method for an air-cooled proton exchange membrane fuel cell (PEMFC), which comprises the following steps: step 1, constructing an air-cooled PEMFC system, which comprises a stack, a temperature sensor, a humidity sensor, a variable-speed fan cooling module, an electronic load and a data acquisition device; the atomization frequency f of an atomization humidification module and the atomization water temperature can be adjusted; step 2, establishing a mapping relationship between a load current and a fan reference speed; step 3, initializing the atomization humidification module and running the air-cooled PEMFC system; when the system is running initially, the fan speed is loaded based on the mapping relationship between the load current and the fan reference speed, and the atomization humidification module is run based on the initialization result; step 4, collecting the stack temperature T, the cathode humidity RH and the load current I in real time and transmitting them to a system controller; and step 5, dynamically regulating and controlling the temperature and humidity. The application realizes the coordinated regulation and control of the membrane hydration state and the stack temperature.

Description

Technical Field

[0001] This invention belongs to the field of air-cooled proton exchange membrane fuel cell (PEMFC) control technology, specifically relating to a hydrothermal management method for air-cooled PEMFC. Background Technology

[0002] Air-cooled proton exchange membrane fuel cells (PEMFCs) are widely used in transportation, distributed power generation, and other fields due to their advantages such as not requiring an independent coolant circuit, simple structure, and strong system robustness. However, they face significant hydrothermal management bottlenecks when operating at medium to high power: on the one hand, the intensified electrochemical reaction leads to a surge in heat generation, and if heat dissipation is not timely, it will cause a decrease in the mechanical strength and functional damage of the proton exchange membrane, leading to system performance degradation; on the other hand, the proton conduction of the proton exchange membrane depends on the water content, and high-speed airflow at medium to high power easily accelerates the evaporation of membrane moisture, leading to membrane dryness and increased impedance, while insufficient airflow can cause cathode flooding, hindering oxygen diffusion, causing voltage unevenness or even cell failure.

[0003] In existing technologies, hydrothermal management often employs independent control strategies: temperature is controlled solely by adjusting fan speed, or humidity is adjusted only by a humidifier, without considering the coupling relationship between temperature and humidity. Under dynamic load conditions, this independent control cannot match the dynamic changes in membrane hydration requirements and reactor heat dissipation requirements, resulting in membrane water content and reactor temperature remaining in a suboptimal state for extended periods, thus limiting system response speed, energy efficiency, and lifespan. Therefore, there is an urgent need for a hydrothermal management method that can synergistically control the temperature and humidity of air-cooled PEMFCs, adapting to medium- and high-power operating conditions, and overcoming the bottlenecks of existing technologies. Summary of the Invention

[0004] The purpose of this invention is to provide a hydrothermal management method for air-cooled proton exchange membrane fuel cells (PEMFCs). By dynamically matching atomization parameters (atomization frequency f and atomized water temperature) with fan speed, precise and coordinated control of membrane hydration state and stack temperature is achieved, ensuring stable and efficient system operation at medium to high power. The technical solution adopted is as follows:

[0005] A hydrothermal management method for an air-cooled proton exchange membrane fuel cell (PEMFC) includes the following steps:

[0006] Step 1: Build and initialize an air-cooled PEMFC system. The air-cooled PEMFC system includes:

[0007] The fuel cell stack includes several PEMFCs. Several temperature sensors are installed at the cathode inlet, cathode outlet and cathode flow channel. An atomizing humidification module is installed at the cathode inlet, a humidity sensor is installed at the cathode flow channel, and a variable speed fan cooling module is installed at the cathode outlet. An electronic load is loaded between the cathode and anode. The stack temperature T is the average value of the monitoring values ​​of all temperature sensors.

[0008] The fuel cell stack supplies power to the atomizing humidification module, the variable speed fan cooling module, and the electronic load;

[0009] The system includes a data acquisition device for acquiring the load current I and output voltage U of the fuel cell stack, and its signal is connected to the system controller and the fuel cell stack. The system controller is also signal connected to the temperature sensor, humidity sensor, atomizing humidification module, and variable speed fan cooling module.

[0010] The atomization frequency f and the temperature of the atomized water in the atomizing humidification module are both adjustable;

[0011] Initialization includes setting the target humidity range Q2 and the target temperature range Q1 for the fuel cell stack;

[0012] Step 2: Establish the mapping relationship between load current and fan reference speed;

[0013] In the mapping relationship, the fan speed is the fan reference speed, and the stack temperature T under the load current is within the stack temperature target range Q1; the temperature target range Q1 is a set value; the fan reference speed is the minimum speed that makes the stack temperature T within the stack temperature target range Q1.

[0014] Step 3: Initialize the atomizing humidification module and run the air-cooled PEMFC system; at the beginning of operation, load the initial value of the load current to the fuel cell stack, and load the load fan speed based on the mapping relationship between the load current and the fan reference speed, and run the atomizing humidification module based on the initialization results;

[0015] The initialization results include: the initial value of the atomization frequency f0 and the initial value of the atomized water temperature W0; the initial value W0 is greater than the current stack temperature.

[0016] Step 4: Real-time acquisition of reactor temperature T, cathode humidity RH, and load current I, and transmission to the system controller;

[0017] Step 5: Perform dynamic temperature and humidity coupling control.

[0018] First, adjust the fan speed based on the relationship between the reactor temperature T and the target temperature range Q1;

[0019] Then, based on the relationship between the cathode humidity RH and the target humidity range Q2, the atomization frequency f or the atomization water temperature is adjusted.

[0020] Preferably, step 5 specifically includes:

[0021] Step 5A: Determine if the reactor core temperature T is within the target temperature range Q1. If yes, proceed to step 5B. Otherwise, first adjust the fan speed until the reactor core temperature T is within the target temperature range Q1. Alternatively, under medium-to-high load conditions, if the fan speed reaches full speed but still cannot bring the reactor core temperature T within the target temperature range Q1, maintain the fan speed at full speed and then proceed to step 5B. Medium-to-high load refers to a current density in the fuel cell stack exceeding 0.3 A / cm². 2 The working conditions;

[0022] Step 5B: Determine whether the cathode humidity RH is within the target humidity range Q2. If yes, proceed to step 5C. Otherwise, first adjust the atomization frequency f or the atomization water temperature until the cathode humidity RH is within the target humidity range Q2 before proceeding to step 5C.

[0023] Step 5C, Output running parameters:

[0024] When the reactor temperature T is within the target temperature range Q1 and the cathode humidity RH is within the target humidity range Q2, the operating parameters include: the fan speed, the initial value f0 of the atomization frequency f, and the initial value W0 of the atomization water temperature during the initial operation in step 3.

[0025] When the reactor temperature T is not within the target temperature range Q1 and the cathode humidity RH is not within the target humidity range Q2, the operating parameters include: the fan speed or full-speed fan speed in step 5A that makes the reactor temperature T within the target temperature range Q1, and the atomization frequency f and atomization water temperature in step 5B that makes the cathode humidity RH within the target humidity range Q2.

[0026] When the reactor temperature T is not within the target temperature range Q1 and the cathode humidity RH is within the target humidity range Q2, the operating parameters include: the fan speed or full-speed fan speed that makes the reactor temperature T within the target temperature range Q1 in step 5A, the initial value f0 of the atomization frequency f, and the initial value W0 of the atomization water temperature.

[0027] When the reactor temperature T is within the target temperature range Q1 and the cathode humidity RH is not within the target humidity range Q2, the operating parameters include: the fan speed during the initial operation in step 3, and the atomization frequency f and atomization water temperature in step 5B when the cathode humidity RH is within the target humidity range Q2.

[0028] Preferably, after step 5, the following is further specified:

[0029] Step 6: Optimize operating parameters:

[0030] Step 6A: Calculate the energy efficiency return rate :

[0031] ,

[0032] ,

[0033] in, -Power of the fuel cell stack before atomization and humidification Power after atomization and humidification The difference;

[0034] - Input power of the atomizing humidification module.

[0035] Step 6B: Determine the value of EGR. If EGR≤0, execute steps 2~5; otherwise, use the running parameters in step 5C as the optimal parameters.

[0036] Preferably, step 2 specifically includes:

[0037] Step 2A: Run the variable speed fan cooling module, electronic load and fuel cell stack, and collect the stack temperature T in real time; during operation, adjust the electronic load so that the load current of the fuel cell stack changes in a gradient, and run for a set time for each gradient current.

[0038] Step 2B: Determine the reference fan speed of the variable speed fan cooling module for each gradient load current I;

[0039] When the stack temperature T exceeds the target temperature range Q1 of the fuel cell stack and the fan speed does not reach full speed, the fan speed corresponding to the last adjustment is the fan reference speed.

[0040] When the stack temperature T exceeds the target temperature range Q1 of the fuel cell stack and the fan speed has reached full speed, the full speed fan speed is the fan reference speed.

[0041] Preferably, the atomizing humidification module includes:

[0042] A frequency-adjustable atomizing actuator is used to output atomized water to achieve atomized humidification;

[0043] The water tank contains an electric heating element, and a temperature sensor is installed on its inner wall. The temperature sensor is connected to the system controller via signal. The electric heating element is connected to the temperature controller and the system controller via signal in sequence.

[0044] And drive control elements, signal connections to atomizing actuators and system controller;

[0045] The electric heating tube and the atomizing actuator are both electrically connected to the fuel cell stack.

[0046] Preferably, the variable speed fan cooling module includes:

[0047] Variable speed fan;

[0048] It includes a fan controller, which is connected to the variable speed fan and system controller via signal connections.

[0049] Compared with the prior art, the advantages of the present invention are:

[0050] 1. Outstanding coordinated control capability: Breaking through the limitations of traditional independent temperature and humidity control, it establishes a dynamic coupling logic of "load-atomization-fan", which can simultaneously meet the needs of medium and high power operating conditions (current density in the fuel cell stack is higher than 0.3A / cm). 2 Under the operating conditions of the reactor body, the heat dissipation and membrane hydration requirements are met, effectively mitigating the risk of membrane drying and flooding coexisting, and significantly improving the system's operational stability.

[0051] According to existing technology: the current density can be obtained by dividing the current by the active area of ​​a single fuel cell; the current is obtained through a current sensor, and the active area of ​​the fuel cell is the design value, which remains constant during use.

[0052] 2. Significant performance improvement: Through precise matching of core atomization parameters and fan speed, the maximum output power of the fuel cell stack can be increased by more than 10%, the energy efficiency benefit rate remains positive in the medium and high load range, and the maximum operating temperature is increased from 45-55℃ of traditional air-cooled PEMFC to no less than 65℃.

[0053] Maximum output power increased by more than 10%

[0054] Figure 5 (Left) Shows different atomization frequencies (0kHz, 95kHz, 100kHz, 105kHz) and different current densities (0.96 A / cm). 2 1.00 A / cm 2 The output power of the fuel cell stack varies significantly depending on the combination of these factors. For example, at a frequency of 100 kHz and a power output of 1.00 A / cm², the output power differs considerably. 2 Under these conditions, the output power is approximately 350W, compared to the un-atomized condition (0kHz / 1.00 A / cm). 2 The power output is increased by approximately 13% (from approximately 310W). This indicates that the optimized atomization parameters and fan speed work together to significantly improve power output.

[0055] Energy efficiency yield remains positive in the medium-to-high load range:

[0056] Figure 3 In this case, the atomization frequency is controlled at 100kHz, and the current density reaches 0.30 A / cm². 2 At the above (medium-high load range as defined in the patent), the net power turns positive, indicating that in the medium-high load range (current density ≥ 0.3 A / cm²), the net power is positive. 2 The system's energy efficiency gain is positive, meaning that the power gain brought by the atomizing humidification module is greater than its own power consumption.

[0057] The maximum operating temperature has been increased to no less than 65℃.

[0058] Figure 5 (Right) shows that under humidified conditions, the stable operating temperature of the fuel cell stack can reach above 65°C (e.g., at 105kHz), while traditional air-cooled PEMFCs typically operate at 45-55°C due to heat dissipation limitations. This method, through synergistic regulation, ensures both the hydration state of the membrane and increases the heat dissipation limit, thereby allowing the fuel cell stack to operate safely at higher temperatures.

[0059] 3. Strong adaptability to operating conditions: It can adapt to the full range of operating conditions of air-cooled PEMFC from low power start-up to high power stable operation. Through parameter iteration optimization, it can be adapted to different system specifications and has a wide range of engineering applications. Attached Figure Description

[0060] Figure 1 Flowchart of hydrothermal management method for air-cooled proton exchange membrane fuel cells (PEMFCs);

[0061] Figure 2 This is a diagram of the architecture of an air-cooled PEMFC system.

[0062] Figure 3 A comparison chart of the net power of the fuel cell stack under different current densities and different ultrasonic vibration frequencies;

[0063] Figure 4 A comparison chart of the output power of fuel cell stacks under different stack temperatures and different ultrasonic vibration frequencies;

[0064] Figure 5 The left figure shows a comparison of the output power of the fuel cell stack under different current densities and ultrasonic vibration frequencies; the right figure shows a comparison of the stack body temperature under different current densities and ultrasonic vibration frequencies.

[0065] Figure 6 A schematic diagram showing the arrangement of temperature sensors on a fuel cell stack;

[0066] Figure 7 This is a schematic diagram of the variable speed fan installed on the fuel cell stack. Detailed Implementation

[0067] The hydrothermal management method for an air-cooled proton exchange membrane fuel cell (PEMFC) of the present invention will now be described in more detail with reference to schematic diagrams, which illustrate preferred embodiments of the invention. It should be understood that those skilled in the art can modify the invention described herein while still achieving its advantageous effects. Therefore, the following description should be understood as being of general knowledge to those skilled in the art and is not intended to limit the invention.

[0068] This invention applies to air-cooled proton exchange membrane fuel cell systems, with typical applications including but not limited to distributed microgrid power supply, power sources for small mobile devices, and emergency backup power. Before implementation, a system architecture with the following functional modules must be constructed. All component selections and connection methods that meet the functional requirements fall within the scope of protection of this invention.

[0069] like Figures 1-2 A method for hydrothermal management of an air-cooled proton exchange membrane fuel cell (PEMFC) includes the following steps:

[0070] Step 1: Build and initialize an air-cooled PEMFC system.

[0071] The air-cooled PEMFC system includes: fuel cell stack, atomizing humidification module, variable speed fan cooling module, data acquisition equipment, system controller, electronic load, temperature sensor and humidity sensor.

[0072] The fuel cell stack includes several PEMFCs connected in series. Several temperature sensors are installed at the cathode inlet, cathode outlet and cathode flow center. An atomizing humidification module is installed at the cathode inlet. A humidity sensor is installed at the cathode flow center. A variable speed fan cooling module is installed at the cathode outlet. An electronic load is loaded between the cathode and anode.

[0073] Among them, the stack temperature T is the average value of all temperature sensor readings;

[0074] The fuel cell stack supplies power to the atomizing humidification module, the variable speed fan cooling module, and the electronic load;

[0075] Stack temperature T: reflects the temperature distribution inside the stack.

[0076] Humidity sensor: measures the humidity of the cathode to detect changes inside the fuel cell after humidification, but it is essentially also a temperature sensor.

[0077] The data acquisition device is used to acquire the load current I and voltage U of the fuel cell stack, and its signals are connected to the system controller.

[0078] The system controller is connected to the temperature sensor, humidity sensor, atomizing humidification module, and variable speed fan cooling module via signal connections.

[0079] The atomization frequency f and the temperature of the atomized water in the atomizing humidification module are both adjustable.

[0080] Initialization includes setting the target humidity range Q2 and the target temperature range Q1 for the fuel cell stack in the system controller.

[0081] (1) Atomizing humidification module:

[0082] It is an ultrasonic atomizing humidification module that can output at least three characteristic frequencies and adjust the temperature of the atomized water to ensure that the temperature of the atomized water is compatible with the temperature of the fuel cell stack, thus avoiding local overcooling caused by low-temperature water mist or accelerated moisture loss from the membrane caused by high-temperature water mist.

[0083] Frequency range: 90kHz-110kHz, divided into three characteristic frequencies.

[0084] The three characteristic frequencies include: core optimization frequency, low-load auxiliary frequency, and emergency backup frequency.

[0085] Core optimized frequency (preferred): Defined as the frequency with the smallest atomized particle size, uniform distribution, and highest evaporation efficiency (e.g., 95kHz-105kHz), suitable for medium to high loads (I≥0.5I). n It should be used in a fixed position to ensure a balance between membrane hydration and heat dissipation.

[0086] Low-load auxiliary frequency (suitable for low demand): defined as a frequency with "small atomization volume and low power consumption" (such as 90kHz-95kHz), used under low load to avoid excessive humidification.

[0087] Emergency backup frequency (extreme scenario): Defined as the frequency with "high atomization" (e.g., 105kHz-110kHz), it is only used briefly when the membrane is extremely dry (e.g., RH < 25%), while increasing the fan speed to prevent water mist from condensing.

[0088] The temperature of the atomized water can be controlled within the range of 40℃-70℃.

[0089] Reference temperature setting: The reference temperature is set by default to "target value of reactor body temperature + difference between atomized water temperature and reactor body temperature" to ensure rapid evaporation of atomized water.

[0090] The temperature difference between the atomized water and the stack body can be set in the range of 5℃-15℃.

[0091] Temperature deviation adjustment:

[0092] If the temperature of the atomized water is significantly lower than the reference temperature (e.g., above 5°C), reduce the fan speed to offset the effect of slowed evaporation.

[0093] If the temperature of the atomized water is significantly higher than the reference temperature (e.g., above 5°C), increase the fan speed to prevent excessive evaporation of membrane moisture.

[0094] The atomized water temperature refers to the actual temperature of the water used for ultrasonic atomization humidification; the reference temperature is the ideal temperature of the water used for ultrasonic atomization humidification.

[0095] For example, for a certain type of air-cooled fuel cell, if the target temperature of the stack is 40°C, and the temperature difference is set to 5°C in advance, then the reference temperature, which is the ideal temperature of the water used for ultrasonic atomization humidification, is 45°C.

[0096] The temperature of the atomized water may not be 45℃; it could be 48℃ or 42℃.

[0097] This is because the temperature of the atomized water can be set in advance and is adjustable (i.e., the value of 48 / 42℃ mentioned above), but the stable operating temperature of the reactor (the target value of the reactor temperature) is not set in advance (i.e., the value of 40℃ mentioned above), so there is a deviation.

[0098] Therefore, it is necessary to adjust the fan speed to control the reactor temperature so that the reference temperature matches the atomized water temperature.

[0099] Component selection example:

[0100] Atomizing components: microporous atomizing plates (pore size 4-6μm), piezoelectric ceramic atomizers;

[0101] Drive control components: NE555 multi-channel drive board or PLC controller;

[0102] Temperature control components: water tank, electric heating element, temperature sensor, temperature controller.

[0103] like Figure 2 As shown:

[0104] The drive control element, temperature controller, and temperature sensor in the water tank are all connected to the system controller signal.

[0105] The drive control element's signal is connected to the atomizing actuator;

[0106] The electric heating element is connected to the temperature controller via a signal.

[0107] The electric heating element, atomizing actuator, and fuel cell stack are electrically connected;

[0108] The drive control element (atomization controller) adjusts the atomization frequency and is connected to the frequency-adjustable atomization actuator via signal.

[0109] An electric heating element and a temperature sensor (which can be installed on the wall) are installed in the water tank.

[0110] There is also a signal connection between the temperature sensor in the water tank and the system controller;

[0111] The electric heating tubes in the container are powered by the reactor core, so there is an electrical connection between the container and the reactor core.

[0112] The container and the stack may not be installed or directly connected, therefore, there may not be a direct mechanical connection.

[0113] The above-mentioned components can be replaced with other elements with equivalent functions, such as using an ultrasonic spray nozzle instead of a microporous atomizing plate, which still falls within the protection scope of this invention.

[0114] (2) Variable speed fan cooling module:

[0115] An axial fan supporting pulse width modulation (PWM) is used and installed on the cathode side of the fuel cell stack. By adjusting the fan speed, the airflow can be controlled, thus achieving adjustable heat dissipation intensity of the stack.

[0116] Speed ​​control method: Supports pulse width modulation or voltage linear regulation, and the speed adjustment range can be controlled in the range of 1000RPM-15000RPM;

[0117] Airflow: To meet the heat dissipation requirements of different power stacks, the airflow can be set to cover the range of 10CFM-100CFM;

[0118] Installation location: can be selected on the cathode inlet side (push-type) or outlet side (suction-type).

[0119] Component selection example:

[0120] Variable speed fan type: JC6025B12SC axial fan, centrifugal fan;

[0121] Speed ​​controller: STM32F103 microcontroller or dedicated PWM driver chip.

[0122] like Figure 2 As shown:

[0123] The speed controller is connected to the system controller via signal transmission.

[0124] The variable speed fan is connected to the speed controller via signal and to the fuel cell stack via electrical connection.

[0125] The variable speed fan is mounted on the fuel cell stack.

[0126] Specifically: The fan is installed on the outside of the fuel cell stack, supplying gas directly to the cathode side (oxygen side) flow channel via suction or blowing; typically, such as Figure 7 As shown, the variable speed fan is mounted on a housing (the housing can be a newly designed housing or the outer housing of the fuel cell stack), and the housing is then directly mounted on the stack with bolts; the end of the variable speed fan is a certain distance away from the air inlet of the stack.

[0127] The fan type and speed controller can be replaced according to actual needs, as long as they meet the requirements of adjustable speed and flow rate, they are all within the scope of protection of this invention.

[0128] (3) Data acquisition equipment, i.e. Figure 1 The "multi-parameter monitoring module" in the text:

[0129] Functional requirements: Implement "temperature and humidity acquisition" and "electrical performance acquisition", with specific parameters meeting the following requirements:

[0130] Temperature acquisition: such as Figure 6 As shown, the temperature sensor covers at least three sections of the fuel cell stack (front, middle, and rear).

[0131] Figure 6 In the diagram, numbers 1 through 9 represent nine temperature sensors.

[0132] Cathode humidity acquisition: Monitoring the dew point temperature at the center of the cathode channel; dew point temperature is an indicator used to reflect humidity.

[0133] Dew point temperature is a physical quantity characterizing the absolute humidity of a gas. Its core relationship with humidity is determined by the thermodynamic saturated water vapor pressure. Specifically, dew point temperature is directly equivalent to the saturation temperature corresponding to the current partial pressure of water vapor in the gas; that is, water vapor will begin to condense and precipitate when the gas is cooled to this temperature. This temperature value does not change with ambient temperature and directly reflects the absolute content of water vapor (such as absolute humidity or water vapor partial pressure). Relative humidity, on the other hand, is the result of the combined effect of dew point temperature and ambient temperature—when the actual gas temperature remains constant, the higher the dew point temperature (the greater the water vapor partial pressure), the higher the relative humidity; if the dew point temperature remains constant, an increase in ambient temperature will lead to a decrease in relative humidity.

[0134] Electrical performance acquisition: Acquire the load current and output voltage of the fuel cell stack.

[0135] Component selection example:

[0136] Temperature sensors: Type K thermocouple, platinum resistance thermometer;

[0137] Humidity sensor: dew point meter;

[0138] Data acquisition equipment: Yokogawa SMARTDAC+ GM10 data acquisition unit and data acquisition card.

[0139] The sensor type and data acquisition equipment can be replaced, as long as the acquisition accuracy and frequency requirements are met, they all fall within the protection scope of this invention.

[0140] Specifically: The data acquisition device is a storage element, which is equipped with a temperature acquisition unit, a humidity acquisition unit, and an electrical performance acquisition unit.

[0141] The temperature acquisition unit is connected to each temperature sensor to obtain the stack temperature distribution in real time, and it is connected to the system controller.

[0142] A humidity acquisition unit, connected to each humidity sensor, acquires the dew point temperature at the center of the cathode channel in real time and is connected to the system controller; the average dew point temperature is used to characterize the cathode humidity.

[0143] Dew point average = the average value of all humidity sensor readings.

[0144] The electrical performance acquisition unit acquires the load current and output voltage of the fuel cell stack in real time, and is connected to the system controller.

[0145] The system controller calculates the output power based on the load current and output voltage;

[0146] Among them, the load current is the demand from the outside, and the output voltage is the electrical output performance of the fuel cell after responding to the current demand.

[0147] (4) System controller:

[0148] As the main controller, in addition to having the same signal acquisition capability as the data acquisition device, it also has the ability to send control commands to the controllers of the atomizing humidification module, the variable speed fan cooling module, and even the air supply module (not detailed in this patent). After receiving the commands, each sub-module further adjusts the corresponding actuator.

[0149] The sub-modules include: atomizing humidification module, variable speed fan cooling module, and air supply module.

[0150] like Figure 2 As shown:

[0151] The temperature sensor on the fuel cell stack, the humidity sensor, and the temperature sensor in the water tank transmit data to the data acquisition device and the system controller, respectively.

[0152] The system controller calculates the average temperature and dew point average temperature respectively, and then issues commands to the drive control element, temperature controller and speed controller.

[0153] Specifically: The system controller sends a command to the speed controller to adjust the fan speed;

[0154] The system controller sends commands to the drive control element to adjust the atomization frequency f;

[0155] The system controller sends a command to the temperature controller to adjust the temperature of the atomized water.

[0156] In addition, by Figure 2Hydrogen gas enters the anode flow channel of the fuel cell stack after passing through a flow meter and pressure regulator from the hydrogen source (hydrogen tank). The pressure of the hydrogen supplied to the fuel cell stack is measured by a pressure sensor located at the outlet of the pressure reducing valve. When pressure adjustment is required, the system controller sends a command to the pressure controller, which in turn adjusts the flow regulating valve (not shown in the diagram) to change the hydrogen supply flow rate.

[0157] (5) System initialization parameter settings:

[0158] The target temperature range for the fuel cell stack is 45℃-65℃ (adjusted according to the type of proton exchange membrane).

[0159] Load condition classification: Low load (current density < 0.3A / cm²) 2 Medium load (0.3A / cm) 2 -0.8A / cm 2 High load (>0.8A / cm) 2 ).

[0160] Medium to high power operating conditions, including medium load and high load operating conditions.

[0161] Step 2: Based on the heat load requirements of the PEMFC system under different load currents, establish a mapping relationship between load current and fan reference speed. The fan reference speed is the minimum speed that ensures the stack temperature T is within the target temperature range Q1 of the fuel cell stack.

[0162] In the mapping relationship, the fan speed is the fan reference speed, and the stack temperature T under the load current is located within the stack temperature target range Q1; the temperature target range Q1 is a set value.

[0163] The target temperature range Q1 is 45℃-65℃, which can be adjusted according to the type of proton exchange membrane.

[0164] The heat load requirement is determined based on the load current; under different load currents, the working efficiency of the stack is different, the waste heat (heat load) generated is also different, and the air volume required to remove this waste heat is also different. Therefore, it is necessary to establish a mapping relationship between load current and fan reference speed.

[0165] Membrane hydration requirements refer to maintaining the humidity of the proton exchange membrane within the reactor body within a reasonable range.

[0166] The humidity (RH) is used to reflect the membrane's humidity; heat load demand and membrane hydration demand refer to the requirements for dissipating waste heat and maintaining cathode humidity within a certain range under a certain load current demand.

[0167] Step 2 specifically includes:

[0168] Step 2A: Run the variable speed fan cooling module, electronic load and fuel cell stack, and collect the stack temperature T in real time; during operation, adjust the electronic load so that the load current of the fuel cell stack changes according to a gradient, and each gradient current runs stably for 20min-60min.

[0169] In this embodiment, "operating fuel cell stack" refers to: such as Figure 2 As shown, hydrogen is continuously supplied to the anode, and air is continuously supplied to the cathode through a variable-speed fan cooling module, keeping the fuel cell stack in operation.

[0170] That is, adjust the electronic load so that the load current of the fuel cell stack is N*I. n ; 0 < N ≤ 1; I n - Rated current of fuel cell stack.

[0171] The load current is kept stable until the temperature fluctuation of the reactor body is ≤2℃ (system thermal equilibrium).

[0172] The gradient is: 0.1I n →0.3I n →0.5I n →0.7I n →0.9I n →1.0I n .

[0173] The variable speed fan and the atomizing humidifier are powered by the stack body or the lithium battery accessories that support the stack's operation; when the electronic load requests a load current, the stack body responds to the load current request and supports the operation of the variable speed fan cooling module.

[0174] Electronic loads are analogous to electrical appliances used to supply power, such as electric vehicles and light bulbs.

[0175] When starting a high-speed fan, you can start from the highest speed (full speed) of the variable-speed fan and gradually reduce the speed to determine the minimum speed required to dissipate the waste heat, i.e., the fan base speed.

[0176] Operating the variable-speed fan cooling module: At the physical level, this is a closed-loop control system from command to mechanical action. The system controller, based on an algorithm or preset, sends a speed command to a dedicated fan controller (speed controller); the fan controller then converts this command into a pulse-width modulation (PWM) signal with a specific duty cycle, driving the fan motor to rotate and thus forcing airflow through the fuel cell cathode for cooling. The real-time operating status of the fan and the temperature feedback signal of the fuel cell are then sent back to the controller, forming a complete regulation loop.

[0177] Adjusting the electronic load essentially involves changing the external circuit impedance of the fuel cell stack to simulate actual power demand.

[0178] The operator or the main control program (system controller) sets the constant current or constant power mode and target value of the electronic load. Its internal power semiconductor devices will dynamically adjust their conduction state to form a controllable current path. This forces the fuel cell stack to increase the electrochemical reaction rate to meet the current output, thereby directly changing the heat generation power and output voltage of the fuel cell stack, creating varying operating conditions for hydrothermal management.

[0179] Starting the fan at its maximum speed: In the context of establishing a baseline mapping relationship, this specifically refers to an automated speed optimization process. The system first commands the fan to start at its maximum speed, then gradually reduces the speed in fixed steps (e.g., decreasing the duty cycle by 5% each time), while simultaneously monitoring the reactor temperature. Once the system detects that the temperature is about to exceed the preset target range, it determines that the previous speed is the minimum feasible speed to meet the heat dissipation requirements under the current load, i.e., the "fan baseline speed," and pairs it with the current load current for storage, so that subsequent control strategies can directly call upon it.

[0180] Step 2B, Fan speed optimization: Determine the base fan speed of the variable speed fan cooling module for each gradient of load current I.

[0181] (1) When the stack temperature T exceeds the target temperature range Q1 of the fuel cell stack and the fan speed has not reached full speed, the fan speed corresponding to the last adjustment shall be the fan reference speed. Example:

[0182] Assumption:

[0183] The target temperature range for the fuel cell stack is Q1: 45℃ - 65℃.

[0184] Test condition: Load current is 50% of the rated current (i.e., 0.5I). n ).

[0185] Fan speed adjustment step: 5% reduction in rated speed (N) each time. n ).

[0186] Full turn: 100% N n .

[0187] Scene and steps:

[0188] Initial state: To facilitate rapid heat dissipation, the system controller commands the fan to run at full speed (100% N). n Start-up. At this time, due to its extremely strong heat dissipation capacity, the reactor temperature T stabilizes at 43℃ (below the Q1 lower limit of 45℃).

[0189] First speed reduction: The system attempts to reduce fan speed to save energy. The speed is reduced by 5%, to 95% N. nAfter the operation stabilized, the reactor temperature T was monitored to rise to 48℃. This temperature is still within the Q1 range (45-65℃), so the speed reduction was successful, and we can continue to try to find an even lower speed.

[0190] Second reduction: Continue to reduce the engine speed by 5%, to 90% N. n After operation stabilized, the reactor temperature T was monitored to rise further to 60°C. This temperature was still within the Q1 range, and the rate reduction was successful again.

[0191] Third reduction: Lower the engine speed by another 5%, to 85% N. n After the operation stabilized, the reactor temperature T was monitored to rise sharply to 68°C. This temperature exceeded the upper limit of Q1 (65°C).

[0192] Result determination:

[0193] At this point, the condition is met: "The stack temperature T exceeds the target temperature range Q1 of the fuel cell stack and the fan speed has not reached full speed" (T=68℃>65℃, and the current speed is 85% N). n (Not full rotation).

[0194] According to the rules, "the fan speed corresponding to the last adjustment is the fan base speed".

[0195] "Current adjustment" refers to the third rate of decrease that leads to overheating (to 85% N). n ).

[0196] "The previous adjustment" refers to the state where the temperature was successfully maintained within Q1 (90% N) after the second rate reduction. n ).

[0197] Therefore, the system will determine: at the current 0.5I n Under load, the fan base speed is 90% N. n This speed is the lowest and most energy-efficient speed that can be achieved while ensuring that the temperature does not exceed the limit (≤65℃).

[0198] (2) When the stack temperature T exceeds the target temperature range Q1 of the stack and the fan speed has reached full speed, the full-speed fan speed is the fan reference speed.

[0199] In the process of finding the fan reference speed, for each gradient load current I, the fan speed is gradually reduced from full speed, and the "minimum fan speed" that stabilizes the reactor temperature within the target temperature range Q1 is recorded as the fan reference speed under that load current I.

[0200] This involves gradually reducing the fan speed from full speed to find the minimum fan speed that still keeps the temperature within a reasonable range. This minimum fan speed is called the "fan reference speed".

[0201] The fan speed is adjusted by regulating the PWM through the fan controller, but the adjustment step size is not completely continuous; for example, if the adjustment is made at 5% of the maximum speed, then the PWM may be 50% / 55% / 60%, etc. In this case, the temperature of the stack under steady-state conditions may not be the lower limit or the upper limit of the target temperature range Q1 of the stack, but a value in the range; since the fan speed is gradually reduced after full speed (which may not generate much heat and therefore does not need to be full speed), the minimum fan speed may be found; the temperature may be inside the target temperature range Q1 at one moment and jump out of the target temperature range Q1 at the next moment.

[0202] The basic relationship between load current and fan speed:

[0203] For the low load current range, a lower fan speed is set to match the low heat generation demand, avoiding excessive heat dissipation that could cause the proton exchange membrane to become too cold.

[0204] For medium to high load current ranges, the fan speed is increased as the load current increases to balance the heat dissipation of the reactor body and the hydration requirements of the membrane, and to prevent local overheating.

[0205] For high load current ranges, a maximum fan speed threshold is set to ensure that the reactor temperature does not exceed the proton exchange membrane's tolerance limit and to avoid membrane damage.

[0206] To further optimize the fan speed, step 2B solves for the fan reference speed, which is taken as the optimal fan speed, i.e., the minimum fan speed.

[0207] Step 2C: Store the load current and the corresponding fan reference speed in the system controller, which can be directly called in subsequent steps 3 and 5.

[0208] For example, in step 5, if you want to adjust the fan speed, you need to select the fan reference speed.

[0209] Table 1 Load Current-Fan Reference Speed ​​Mapping Table

[0210]

[0211] In Table 1:

[0212] I - Load current; I n - Charge stack rated current; I / I n =0.1, 0.3, 0.5, 0.7, 0.9, 1.

[0213] N - Fan reference speed; N n - Fan rated speed. N / N n =15%-20%, 30%-35%, 45%-50%, 65%-70%, 85%-90%, 95%-100%.

[0214] Step 3: Initialize the atomizing humidification module and run the air-cooled PEMFC system; at the beginning of operation, load the initial value of the load current to the fuel cell stack, load the fan speed based on the mapping relationship between the load current and the fan reference speed, and run the atomizing humidification module based on the initialization results in the system controller.

[0215] The initialization results include: the initial value f0 of the atomization frequency f and the initial value W0 of the atomized water temperature; the initial value W0 is greater than the current stack temperature. The current stack temperature is obtained from the temperature sensor, and the average temperature is taken.

[0216] The load current is determined based on external demand (electric vehicles, etc.), and here the external demand is simulated by an electronic load.

[0217] Adjusting the load current achieves the "load current".

[0218] The initial value of the load current can also be understood as: adjusting the electronic load according to external requirements to achieve the "initial value of the load current".

[0219] The initial value f0 of the atomization frequency f is the rated frequency of the atomization actuator, which can be set to 100kHz in the system controller;

[0220] The initial value of the atomized water temperature W0 = the current reactor temperature T + the difference between the atomized water temperature and the reactor temperature.

[0221] Step 4: Real-time acquisition of reactor temperature T, cathode humidity RH, load current I, and output voltage U, and transmission to the system controller.

[0222] Step 5: Perform dynamic temperature and humidity coupling control.

[0223] First, adjust the fan speed based on the relationship between the reactor temperature T and the target temperature range Q1;

[0224] Then, based on the relationship between the cathode humidity RH and the target humidity range Q2, the atomization frequency f or the atomization water temperature is adjusted.

[0225] Step 5 specifically includes:

[0226] Step 5A: Determine whether the reactor temperature T is within the target temperature range Q1. If yes, proceed to step 5B. Otherwise, first adjust the fan speed until the reactor temperature T is within the target temperature range Q1. Or, under medium to high power load, if the fan speed reaches full speed but still cannot make the reactor temperature T within the target temperature range Q1, keep the fan speed at full speed and then proceed to step 5B.

[0227] In some medium-to-high load conditions, there is excessive waste heat (heat load), and the fan speed has reached full speed, but it is still not possible to keep the stack temperature within the target range. Therefore, it is necessary to keep the fan running at full speed and adjust the humidity, based on the principle of evaporator change, to bring the overall temperature and humidity of the stack back to the target range.

[0228] If the reactor temperature T > Q1 upper limit, increase the fan speed in a certain step until T drops back down; step size: 5%-10%, such as 5%.

[0229] If the reactor temperature T < Q1 lower limit, reduce the fan speed in a certain step size until T rises again; step size: 3%-5%, such as 3%.

[0230] Taking a reactor temperature T > Q1 upper limit and a step size of 5% as an example, the fan speed adjustment process is explained in detail with reference to Table 1:

[0231] If the current fan base speed is 15%, and the adjusted fan base speed is switched to 20%, then the adjusted fan base speed = 20% N. n .

[0232] Step 5B: Determine whether the cathode humidity RH is within the target humidity range Q2. If yes, proceed to step 5C. Otherwise, first adjust the atomization frequency f or the atomization water temperature until the cathode humidity RH is within the target humidity range Q2 before proceeding to step 5C.

[0233] If RH < target lower limit: switch the initial value f0 to a higher atomization frequency (e.g., 100kHz → 105kHz), or increase the atomization water temperature (e.g., step size 5℃).

[0234] If RH > target upper limit: switch the initial value f0 to a lower atomization frequency (e.g., 100kHz → 95kHz), or increase the fan speed (e.g., step 3%).

[0235] Step 5C: Output running parameters.

[0236] When the reactor temperature T is within the target temperature range Q1 and the cathode humidity RH is within the target humidity range Q2, the operating parameters include: the fan speed, the initial value f0 of the atomization frequency f, and the initial value W0 of the atomization water temperature during the initial operation in step 3.

[0237] When the reactor temperature T is not within the target temperature range Q1 and the cathode humidity RH is not within the target humidity range Q2, the operating parameters include: the fan speed or full-speed fan speed in step 5A that makes the reactor temperature T within the target temperature range Q1, and the atomization frequency f and atomization water temperature in step 5B that makes the cathode humidity RH within the target humidity range Q2.

[0238] When the reactor temperature T is not within the target temperature range Q1 and the cathode humidity RH is within the target humidity range Q2, the operating parameters include: the fan speed or full-speed fan speed that makes the reactor temperature T within the target temperature range Q1 in step 5A, the initial value f0 of the atomization frequency f, and the initial value W0 of the atomization water temperature.

[0239] When the reactor temperature T is within the target temperature range Q1 and the cathode humidity RH is not within the target humidity range Q2, the operating parameters include: the fan speed during the initial operation in step 3, and the atomization frequency f and atomization water temperature in step 5B when the cathode humidity RH is within the target humidity range Q2.

[0240] Step 6: Optimize operating parameters.

[0241] Step 6A: Calculate the energy efficiency return rate :

[0242] ,

[0243] ,

[0244] in, -Power of the fuel cell stack before atomization and humidification Power after atomization and humidification The difference;

[0245] - The input power of the atomizing humidification module can be obtained from the product manual;

[0246] -Balance of Plant: An accessory used by the fuel cell stack to achieve hydrothermal balance, specifically referring to the atomizing humidification module.

[0247] Normally, this should include all accessories, including the variable speed fan cooling module and the atomizing humidification module. This comparison focuses on the power impact of adding or not adding the atomizing humidification module (i.e., Case 1: other accessories + reactor; Case 2: other accessories + atomizing humidification module + reactor). Therefore, other accessories are not considered; the power consumed by the atomizing humidification module is specifically taken into account.

[0248] Regarding the controllers of the components: the drive control element (atomizer controller) is used to control the atomization frequency; the water tank controller (temperature controller) is used to control the water temperature; the speed controller (fan controller) is used to control the fan speed; the controller FCU acts as the upper controller, sending signals to the controllers of the corresponding components.

[0249] Furthermore, the current and voltage of the atomizing humidification module are not directly measured; the power of the atomizing humidification module at different frequencies is obtained directly through pre-testing / product manual; in actual use, the voltage of the atomizing plate is adjusted to match the power supply through a voltage converter, and the current changes accordingly; during the voltage conversion process, the power remains unchanged, only the voltage changes.

[0250] Step 6B: Determine the value of EGR. If EGR≤0, execute steps 2~5; otherwise, use the running parameters in step 5C as the optimal parameters.

[0251] Figure 1 In this context, "strategy" refers to the optimal parameters.

[0252] When EGR>0, the system's net energy efficiency is considered to be improved, and this operating parameter is considered optimal.

[0253] Figure 3 The relationship between the net power of a fuel cell system (air-cooled PEMFC system) and the current density and atomization frequency is shown.

[0254] The horizontal axis represents the current density of the fuel cell stack, and the vertical axis represents the net power of the system (i.e., the net value of the fuel cell stack output power minus the parasitic power consumption of the atomizing humidification module).

[0255] The sign of the net power reflects the benefit status of the atomizing humidification module: if the net power is greater than zero, it indicates that the output power of the system equipped with the atomizing humidification module is higher than that of the system without the module; conversely, it indicates that the introduction of the humidification module actually reduces the net output.

[0256] Figure 3 The study compared the net power variation trends at different current densities when the atomization frequencies were 95kHz, 100kHz, and 105kHz.

[0257] It can be seen that in the low current density range (e.g., below 0.25 A / cm²), 2 The net power corresponding to all three frequencies is negative, which means that turning on the humidification module at this time will not only fail to increase the output, but will also cause a decrease in net benefit due to parasitic power consumption. Therefore, it is recommended to turn off the humidification function under this condition.

[0258] When the current density is increased to 0.45 A / cm 2At the above times, the net power at both 95kHz and 100kHz atomization frequencies turned positive, and the net power at 100kHz was always higher than that at 95kHz. This indicates that under this condition, using a 100kHz atomization frequency can more effectively improve the overall output performance of the system.

[0259] Figure 4 The coupling relationship between the total output power of the fuel cell system and the ultrasonic vibration frequency and the temperature of the atomized water was demonstrated.

[0260] The horizontal axis represents the ultrasonic vibration frequency (atomization frequency), and the vertical axis represents the output power of the fuel cell stack. Different colored bars represent different atomized water temperature settings.

[0261] Specific data shows that:

[0262] At a vibration frequency of 95kHz, when the temperature of the atomized water is 40℃, the output power of the fuel cell is 239W; while when the temperature of the atomized water is increased to 55℃, the output power increases to 260W.

[0263] At a vibration frequency of 100kHz, the output power of the atomized water at a temperature of 40℃ is 256W, and the power further increases to 280W when the temperature is increased to 55℃.

[0264] In summary, the fuel cell stack achieved the highest output power under the combined configuration of a 100kHz vibration frequency and a 55℃ atomized water temperature, indicating that this parameter combination represents the optimal system operating point, and thus the strategy is effective.

[0265] Figures 3-4 In the diagram, the vertical axis represents "power," which is the "ultrasonic vibration frequency" or "atomization frequency."

[0266] like Figure 5 As shown: Figure 5 (Left) Reveals the relationship between the output power of the fuel cell stack and the current density at different atomization frequencies.

[0267] The horizontal axis represents current density, and the vertical axis represents fuel cell output power. The curves correspond to operating conditions with atomization frequencies of 0kHz (baseline without humidification), 95kHz, 100kHz, and 105kHz, respectively.

[0268] The results show:

[0269] At a current density of 1 A / cm 2 At that time, the output power ranking was: 100kHz > 95kHz > 0kHz > 105kHz. This indicates that the atomization frequency of 105kHz not only failed to improve the output, but also caused a performance degradation;

[0270] The output power at 95kHz and 100kHz was higher than the baseline without humidification (0kHz), indicating that moderate humidification helps improve the performance of the fuel cell stack.

[0271] However, it should be noted that whether this power increase brings net system benefit still needs to be considered in conjunction with other factors. Figure 3 The net power after deducting parasitic power consumption is comprehensively evaluated.

[0272] Figure 5 (Right) reflects the effect of different atomization frequencies on the operating temperature of the fuel cell stack.

[0273] The horizontal axis represents current density, and the vertical axis represents the stable operating temperature of the fuel cell stack. Each curve corresponds to one of the four atomization frequencies mentioned above.

[0274] Data shows:

[0275] At 1 A / cm 2 Under operating conditions, the operating temperatures are ranked as follows: 0kHz > 95kHz > 100kHz > 105kHz.

[0276] The results show that atomized humidification can effectively reduce the operating temperature of the fuel cell stack, and the reduction increases with the atomization frequency. This effect extends the safe operating range of the fuel cell stack, enabling stable operation under high current density conditions that might otherwise lead to proton exchange membrane drying or thermal runaway due to excessive temperature, demonstrating the positive role of humidification management in thermal safety.

[0277] Figure 6 The diagram shows the arrangement of the temperature sensor in the cathode flow channel of the fuel cell stack.

[0278] In this structure, hydrogen flows from right to left, while air flows from front to back.

[0279] Temperature sensors are all arranged in the cathode channel through which the air flows, with monitoring points set at the front, middle and rear positions along the direction of the channel.

[0280] The specific meanings of the numbers are as follows: Sensors 3, 6, and 9 correspond to the front, middle, and rear positions of the left flow channel of the fuel cell, respectively; Sensors 1, 4, and 7 correspond to the front, middle, and rear positions of the right flow channel; and Sensors 2, 5, and 8 correspond to the front, middle, and rear positions of the middle flow channel.

[0281] This arrangement enables distributed temperature monitoring of the stack cathode along the flow direction and cross-sectional space, providing a structural basis for comprehensively acquiring the temperature field distribution of the stack.

[0282] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A hydrothermal management method for an air-cooled proton exchange membrane fuel cell (PEMFC), characterized in that, The method comprises the following steps: Step 1, constructing an air-cooled PEMFC system and initializing, the air-cooled PEMFC system comprising: a stack comprising a plurality of PEMFCs, a plurality of temperature sensors arranged at the cathode inlet, the cathode outlet and the cathode flow channel of the PEMFCs, a mist humidification module arranged at the cathode inlet of the PEMFCs, a humidity sensor arranged in the cathode flow channel of the PEMFCs, a variable-speed fan cooling module arranged at the cathode outlet of the PEMFCs, and an electronic load connected between the cathode and the anode; wherein the stack body temperature T is the average of all the monitored values of the temperature sensors; the stack supplies power to the mist humidification module, the variable-speed fan cooling module and the electronic load; and a data acquisition device for acquiring the load current I and the output voltage U of the stack, which is signal connected to the system controller and the stack; the system controller is signal connected to the temperature sensors, the humidity sensor, the mist humidification module and the variable-speed fan cooling module; the mist frequency f and the mist water temperature of the mist humidification module are adjustable; the initialization comprises setting the humidity target interval Q2 and the temperature target interval Q1 of the stack; Step 2, establishing a mapping relationship between the load current and the fan reference speed; in the mapping relationship, the fan speed is the fan reference speed, and the stack body temperature T under the load current is within the temperature target interval Q1 of the stack; the temperature target interval Q1 is a set value; the fan reference speed is the minimum speed that makes the stack body temperature T within the temperature target interval Q1 of the stack; Step 3, initializing the mist humidification module and running the air-cooled PEMFC system; at the initial running, a load current initial value is loaded to the stack, a load fan speed is loaded based on the mapping relationship between the load current and the fan reference speed, and the mist humidification module is run based on the initialization result; wherein the initialization result comprises the initial value f0 of the mist frequency f and the initial value W0 of the mist water temperature; the initial value W0 is greater than the current stack body temperature; Step 4, acquiring the stack body temperature T, the cathode humidity RH and the load current I in real time and transmitting them to the system controller; Step 5, performing dynamic regulation and control of temperature and humidity: firstly, adjusting the fan speed according to the relationship between the stack body temperature T and the temperature target interval Q1; then, adjusting the mist frequency f or the mist water temperature according to the relationship between the cathode humidity RH and the humidity target interval Q2.

2. The water thermal management method of an air-cooled proton exchange membrane fuel cell (PEMFC) according to claim 1, characterized by, Step 5 specifically comprises: Step 5A, judge whether the stack temperature T is in the temperature target interval Q1, if yes, execute step 5B, otherwise, first adjust the fan speed until the stack temperature T is in the temperature target interval Q1, or under medium and high load conditions, when the fan speed reaches the full speed and still cannot make the stack temperature T in the temperature target interval Q1, keep the fan speed at full speed, and then execute step 5B; medium and high load refers to the current density in the stack is higher than 0.3A / cm 2 ; Step 5B, judging whether the cathode humidity RH is within the humidity target interval Q2, if yes, executing Step 5C, otherwise, first adjusting the mist frequency f or the mist water temperature until the cathode humidity RH is within the humidity target interval Q2, and then executing Step 5C; Step 5C, outputting the running parameters: when the stack body temperature T is within the temperature target interval Q1 and the cathode humidity RH is within the humidity target interval Q2, the running parameters comprise the fan speed, the initial value f0 of the mist frequency f and the initial value W0 of the mist water temperature at the initial running in Step 3. When the stack temperature T is not in the temperature target interval Q1 and the cathode humidity RH is not in the humidity target interval Q2, the operating parameters include: the fan speed or the full-speed fan speed in step 5A to make the stack temperature T in the temperature target interval Q1, the atomization frequency f and the atomization water temperature in step 5B to make the cathode humidity RH in the humidity target interval Q2; When the stack temperature T is not in the temperature target interval Q1 and the cathode humidity RH is in the humidity target interval Q2, the operating parameters include: the fan speed in the initial operation in step 3, the atomization frequency f and the atomization water temperature in step 5B to make the cathode humidity RH in the humidity target interval Q2. When the stack temperature T is not in the temperature target interval Q1 and the cathode humidity RH is in the humidity target interval Q2, the operating parameters include: the fan speed in the initial operation in step 3, the atomization frequency f and the atomization water temperature in step 5B to make the cathode humidity RH in the humidity target interval Q2.

3. The water thermal management method of an air-cooled proton exchange membrane fuel cell (PEMFC) according to claim 1, characterized by, After step 5, it further specifically includes: Step 6, optimizing the operating parameters: Step 6A, Calculating Energy Efficiency Yield : ， ， wherein, - the difference between the power of the stack before atomizing humidification and the power after atomizing humidification . - input power of the nebulizing humidification module; Step 6B, judging the size of EGR, when EGR≤0, executing steps 2-5, otherwise, taking the operating parameters in step 5C as the optimal parameters.

4. The water thermal management method of an air-cooled proton exchange membrane fuel cell (PEMFC) according to claim 1, characterized by, Step 2 specifically includes: Step 2A, running the variable-speed fan cooling module, the electronic load and the electric pile, and collecting the stack temperature T in real time; during the running process, adjusting the electronic load to make the load current of the electric pile change according to the gradient, and running for a set time per gradient current; Step 2B, determining the fan reference speed of the variable-speed fan cooling module for each gradient of the load current I; When the stack temperature T exceeds the temperature target interval Q1 of the electric pile and the fan speed has not reached the full-speed fan speed, the corresponding fan speed of the last adjustment is the fan reference speed; When the stack temperature T exceeds the temperature target interval Q1 of the electric pile and the fan speed has reached the full-speed fan speed, the full-speed fan speed is the fan reference speed.

5. The water thermal management method of an air-cooled proton exchange membrane fuel cell (PEMFC) according to claim 1, characterized by, The atomization humidification module includes: An adjustable-frequency atomization execution element for outputting atomization water to realize atomization humidification; A water tank, which is provided with an electric heating pipe and a temperature sensor on the inner wall, the temperature sensor being signal-connected with the system controller; the electric heating pipe being signal-connected with the temperature controller and the system controller in sequence; And a driving control element, which is signal-connected with the atomization execution element and the system controller; The electric heating pipe and the atomization execution element are electrically connected with the electric pile.

6. The water thermal management method of an air-cooled proton exchange membrane fuel cell (PEMFC) of claim 1, wherein, The variable-speed fan cooling module includes: A variable-speed fan; And a fan controller, which is signal-connected with the variable-speed fan and the system controller. The variable-speed fan cooling module includes: A variable-speed fan; And a fan controller, which is signal-connected with the variable-speed fan and the system controller.

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