A fuel cell high-efficiency purging device and method

Abstract

This invention provides a fuel cell high-efficiency purging device and method, the method specifically including: comparing the rate of change of impedance value k with the empirical constant c: (1) if k≤c: on the cathode side: adjust the air flow rate into the fuel cell stack to v1=10v0; adjust the air exhaust throttle valve to the maximum opening θ1; on the anode side: control the opening and closing time of solenoid valve I (t1=3t0, t2=t'0); adjust the hydrogen-oxygen pressure difference to Δp1=4Δp0; adjust the reflux The pump speed is r1 = r0; (2) If k > c: On the cathode side: reduce the air flow to v2 = (4 ~ 6) v0; control the air pulse emission; On the anode side: reduce the hydrogen-oxygen pressure difference to Δp2 = (1 ~ 2) Δp0; control the opening and closing time of solenoid valve I (t3 = (3 ~ 5) t0, t4 = (8 ~ 10) t'0); increase the speed of the return pump to r2 = (3 ~ 5) r0; (3) When k changes from k > c to k ≤ c, the purging ends. The technical solution of the present invention can quickly remove liquid water from the air chamber and hydrogen chamber of the fuel cell by pulse emission of the air chamber and hydrogen chamber combined with the purging method of hydrogen side return.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and more particularly to a fuel cell high-efficiency purging device and method. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are clean and efficient energy conversion devices. However, their operating principle inevitably leads to the generation of a large amount of liquid water during operation. While the appropriate amount of water is beneficial to fuel cell performance, at low temperatures, a large amount of liquid water undergoes a water-ice phase transition, which can damage the battery structure. Therefore, before storing fuel cells at low temperatures, a significant amount of liquid water needs to be removed to prevent damage to the battery structure due to the water-ice phase transition. In automotive applications, air and hydrogen are often used to purge the gas chamber separately. Due to limitations in the vehicle's battery capacity and hydrogen storage capacity, shortening the purging time and reducing purging power consumption are urgent problems to be solved. Summary of the Invention

[0003] In view of the technical problems of existing fuel cell purging methods mentioned above, a high-efficiency fuel cell purging device and method are provided. By pulse emission of air chamber and hydrogen chamber, combined with hydrogen side recirculation purging method, liquid water in the air chamber and hydrogen chamber of fuel cell can be removed quickly.

[0004] The technical means employed in this invention are as follows:

[0005] A fuel cell high-efficiency purging device includes a gas flow meter, a pressure sensor I, an air exhaust throttle valve, a solenoid valve I, a gas-liquid separator, a reflux pump, and a pressure sensor II;

[0006] The gas flow meter and the pressure sensor I are installed on the air inlet pipe of the fuel cell, and the air exhaust throttle valve is installed on the air outlet pipe of the fuel cell.

[0007] The pressure sensor II and the proportional valve are installed on the hydrogen inlet pipe of the fuel cell, and the solenoid valve I is installed on the hydrogen outlet pipe of the fuel cell.

[0008] The fuel cell is provided with a hydrogen reflux branch, and the hydrogen outlet pipeline and the hydrogen inlet pipeline are connected through the hydrogen reflux branch; the gas-liquid separator and the reflux pump are sequentially arranged on the hydrogen branch, the inlet of the gas-liquid separator is connected to the hydrogen outlet pipeline, and the gas outlet is connected to the reflux pump; the hydrogen reflux branch is used to return the hydrogen discharged from the fuel cell to the hydrogen inlet pipeline after removing liquid water through the gas-liquid separator.

[0009] The present invention also provides a fuel cell high-efficiency purging method, which employs the above-mentioned fuel cell high-efficiency purging device, and specifically includes the following:

[0010] Once the fuel cell stack receives a shutdown purging command, the purging process begins.

[0011] With fuel cell stacks at 100mA / cm 2 Using the airflow v0, the opening and closing time (t0, t'0) of solenoid valve I, the hydrogen-oxygen pressure difference Δp0, and the reflux pump speed r0 as reference values ​​during operation at current density, the impedance value of the fuel cell stack is monitored in real time during purging, and the rate of change of impedance k is compared with the empirical constant c.

[0012] (1) If k≤c, then the purging process is in the first stage, and the following strategy is adopted to remove free water in the flow channel and porous medium:

[0013] On the cathode side: the air flow rate into the fuel cell stack is adjusted to v1 = 10v0 by the gas flow meter; the air exhaust throttle is adjusted to the maximum opening θ1.

[0014] On the anode side: the opening and closing times of solenoid valve I (t1 = 3t0, t2 = t'0) are controlled to cause hydrogen pulse emission, where t1 represents the valve opening time and t2 represents the valve closing time; based on the pressure values ​​of air and hydrogen entering the fuel cell stack monitored by pressure sensor I and pressure sensor II, the hydrogen-oxygen pressure difference is adjusted to Δp1 = 4Δp0 through the proportional valve installed on the hydrogen inlet pipeline; the speed of the reflux pump is adjusted to r1 = r0;

[0015] (2) If k > c, the purging process is in the second stage, and the following strategies are used to remove residual liquid water and film water in the flow channel and diffusion layer:

[0016] On the cathode side: reduce the airflow to v2 = (4~6)v0; control the pulse exhaust of air through the air tailpipe throttle;

[0017] On the anode side: reduce the hydrogen-oxygen pressure difference to Δp2 = (1~2)Δp0; control the opening and closing time of solenoid valve I (t3 = (3~5)t0, t4 = (8~10)t'0) to make hydrogen pulse emission, where t3 represents the valve opening time and t4 represents the valve closing time; increase the speed of the reflux pump to r2 = (3~5)r0;

[0018] (3) When k changes from k>c to k≤c, it indicates that the purging process has entered the third stage, that is, the fuel cell stack is in a state of dynamic water equilibrium and the purging can be ended.

[0019] Furthermore, the rate of change k of the fuel cell stack impedance is calculated using the following formula:

[0020]

[0021] In the formula: z t Let t be the impedance value measured at time t, and Δt be the time step.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] The fuel cell high-efficiency purging device and method provided by the present invention first determines the purging stage by the impedance change rate during the purging process. Secondly, based on the water removal characteristics of the stage, the liquid water and membrane water are removed in a targeted manner by adjusting the air-side gas flow rate, air exhaust mode, hydrogen-side flow rate, hydrogen-side exhaust mode, and return flow rate. This can improve purging efficiency, reduce purging power consumption, and the method is simple and easy to implement.

[0024] Based on the above reasons, this invention can be widely promoted in the field of fuel cells. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A schematic diagram showing the different stages of the fuel cell purging process.

[0027] Figure 2 This is a schematic diagram of the high-efficiency purging device for fuel cells described in this invention.

[0028] Figure 3 This is a schematic diagram of the efficient fuel cell purging method described in this invention.

[0029] Figure 4 This is a schematic diagram of the gas flow rate change during the purging process in Example 1.

[0030] Figure 5 This is a schematic diagram of the gas pressure change during the purging process in Example 1.

[0031] In the diagram: 1. Gas flow meter; 2. Pressure sensor I; 3. Fuel cell stack; 4. Air exhaust throttle valve; 5. Solenoid valve I; 6. Gas-liquid separator; 7. Return pump; 8. Pressure sensor II; 9. Solenoid valve II. Detailed Implementation

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0035] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0036] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0037] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0038] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0039] like Figure 2 As shown, the present invention provides a fuel cell high-efficiency purging device, including a gas flow meter 1, a pressure sensor I 2, an air exhaust throttle valve 4, a solenoid valve I 5, a gas-liquid separator 6, a reflux pump 7, and a pressure sensor II 8.

[0040] The gas flow meter 1 and the pressure sensor I2 are installed on the air inlet pipe of the fuel cell stack 3, and the air exhaust throttle valve 4 is installed on the air outlet pipe of the fuel cell stack 3; the gas flow meter 1 is used to monitor and control the air flow rate entering the fuel cell stack 3.

[0041] The pressure sensor II8 and a proportional valve for controlling the flow rate of hydrogen into the fuel cell stack 3 are installed on the hydrogen inlet pipe of the fuel cell stack 3, and the solenoid valve I5 is installed on the hydrogen outlet pipe of the fuel cell stack 3.

[0042] The fuel cell stack 3 is provided with a hydrogen reflux branch, and the hydrogen outlet pipeline and the hydrogen inlet pipeline are connected through the hydrogen reflux branch. The gas-liquid separator 6 and the reflux pump 7 are arranged sequentially on the hydrogen branch. The inlet of the gas-liquid separator 6 is connected to the hydrogen outlet pipeline, the gas outlet is connected to the reflux pump 7, and the liquid outlet is provided with a solenoid valve II 9. The solenoid valve II 9 is used to control the drainage of the gas-liquid separator 6. The hydrogen reflux branch is used to return the hydrogen discharged from the fuel cell stack 3 to the hydrogen inlet pipeline after removing liquid water through the gas-liquid separator 6.

[0043] like Figure 1 and 3 As shown, this invention also provides a high-efficiency fuel cell purging method, which formulates differentiated anode and cathode purging strategies based on the water removal characteristics of different purging stages, thereby reducing purging energy consumption and shortening purging time; the high-efficiency fuel cell purging device described above specifically includes the following:

[0044] When the fuel cell stack 3 receives the shutdown purging command, it begins purging by introducing air and hydrogen into the fuel cell stack 3.

[0045] With fuel cell stack 3 at 100mA / cm 2 The air flow rate v0, the opening and closing time (t0, t'0) of solenoid valve I5, the hydrogen-oxygen pressure difference Δp0, and the reflux pump speed r0 are used as reference values. During the purging process, the impedance value of fuel cell stack 3 is monitored in real time, and the rate of change of impedance k is compared with the empirical constant c. The empirical constant c is an empirical parameter that can be obtained through experiments and is related to the structure of fuel cell stack 3, the purging gas flow rate, the air and hydrogen inlet pressure, and the purging temperature.

[0046] (1) If k≤c, then the purging process is in the first stage, and the following strategy is adopted to remove free water in the flow channel and porous medium:

[0047] On the cathode side: the air flow rate into the fuel cell stack 3 is adjusted to v1 = 10v0 by the gas flow meter 1; the air exhaust throttle valve 4 is adjusted to the maximum opening θ1;

[0048] In the first stage, in order to accelerate the purging speed, the above-mentioned purging strategy on the cathode side can provide a higher gas flow rate than the second stage, thereby increasing the driving force of the droplet flow and rapidly discharging the liquid water.

[0049] On the anode side: the opening and closing times of solenoid valve I5 (t1 = 3t0, t2 = t'0) are controlled to cause hydrogen pulse emission, where t1 represents the valve opening time and t2 represents the valve closing time; based on the pressure values ​​of air and hydrogen entering fuel cell stack 3 monitored by pressure sensor I2 and pressure sensor II8, the hydrogen-oxygen pressure difference is adjusted to Δp1 = 4Δp0 through the proportional valve installed on the hydrogen inlet pipeline, where the hydrogen-oxygen pressure difference represents the difference between the pressure values ​​of hydrogen and air entering fuel cell stack 3; the rotation speed of reflux pump 7 is adjusted to r1 = r0;

[0050] In the first stage, through the above purging strategy on the anode side, the higher hydrogen-oxygen pressure difference compared to the second stage can quickly remove a large amount of water in the flow channel in a short time. At the same time, the lower speed of the return pump 7 compared to the second stage can allow a larger proportion of liquid water on the hydrogen side to be discharged through the tailpipe. Since the water separation capacity of the gas-liquid separator is limited and there is a lot of free water in the flow channel in the first purging stage, the return flow rate in this stage is reduced to prevent liquid water from entering the return pump or fuel cell stack through the return flow.

[0051] (2) If k > c, the purging process is in the second stage, and the following strategies are used to remove residual liquid water and film water in the flow channel and diffusion layer:

[0052] In the second stage, the continuous atmospheric flow rate on the cathode side has no significant effect on the removal of residual liquid water and membrane water, and it is easy to increase the unevenness of humidity distribution, resulting in local over-drying of the proton exchange membrane. Therefore, in the second stage, the present invention promotes water removal by periodic fluctuations in flow rate and pressure.

[0053] If k > c, the purging process is considered to be in the second stage, and the following strategy is used to remove residual liquid water and film water in the flow channel and diffusion layer:

[0054] On the cathode side: reduce the airflow to v2 = (4~6)v0; control the pulse exhaust of air through the air tailpipe throttle;

[0055] On the anode side: reduce the hydrogen-oxygen pressure difference to Δp2 = (1~2)Δp0; control the opening and closing time of solenoid valve I (t3 = (3~5)t0, t4 = (8~10)t'0) to make hydrogen pulse emission, where t3 represents the valve opening time and t4 represents the valve closing time; increase the speed of the reflux pump to r2 = (3~5)r0;

[0056] On the cathode side: reduce the air flow to v2 = (4~6)v0; control the air pulse emission through the air tail throttle valve 4, and promote the removal of residual liquid water and film water on the air side through the fluctuation of gas flow and pressure.

[0057] On the anode side: reduce the hydrogen-oxygen pressure difference to Δp2 = (1~2)Δp0; control the opening and closing time of solenoid valve I5 (t3 = (3~5)t0, t4 = (8~10)t'0) to make hydrogen pulse emission, where t3 represents the valve opening time and t4 represents the valve closing time, that is, the valve closing time is extended compared to the first stage; increase the speed of return pump 7 to r2 = (3~5)r0, so that the residual liquid water is removed through the gas-liquid separator of the hydrogen return branch, increasing the hydrogen side flow rate and improving the hydrogen utilization rate. In addition, it can improve the uniformity of voltage and humidity distribution during the purging process and significantly reduce purging energy consumption.

[0058] (3) When k changes from k>c to k≤c, it indicates that the purging process has entered the third stage, that is, the fuel cell stack 3 is in a state of dynamic water equilibrium and the purging can be ended.

[0059] The impedance value of the fuel cell stack 3 changes continuously throughout its life cycle. Simply judging by the impedance value cannot accurately determine the purging stage. However, this invention can effectively solve the problem of impedance judgment benchmark shift during the life cycle by using the impedance slope change during the purging process, and accurately determine the purging stage.

[0060] Furthermore, the proportion of each stage in the shutdown purging process of fuel cell stack 3 is related to the working state of the battery before shutdown purging. If the stack is in a high current state for a long time before shutdown (the time and current are different for different fuel cell stacks 3, for example, time ≥10min, current ≥240A), then the purging starts from the first stage. If the stack is in an idling state for a long time before shutdown (the time and current are different for different fuel cell stacks 3, for example, time ≥5min, current 30A), then the purging starts from the second stage.

[0061] Furthermore, the rate of change k of the impedance value of the fuel cell stack 3 is calculated by the following formula:

[0062]

[0063] In the formula: z t Let t be the impedance value measured at time t, and Δt be the time step.

[0064] The fuel cell high-efficiency purging method provided by this invention first divides the entire purging process into three different stages based on the characteristics of water removal in the fuel cell purging process: removal of free water in the flow channel and porous medium, removal of residual free water and membrane water, and water dynamic equilibrium. Then, the purging stage is determined by the rate of impedance change during the purging process. Next, a corresponding purging strategy is formulated based on the water removal characteristics of the current stage. The rapid removal of free water and membrane water is promoted through the synergistic effect of gas flow rate, pressure fluctuation adjustment, reflux pump speed, and tailpipe discharge cycle, shortening the purging time and reducing purging energy consumption. This invention determines the purging stage by the slope of impedance change during the purging process, solving the problem that impedance changes throughout the life cycle cannot accurately determine the purging stage using only impedance values.

[0065] Example 1

[0066] Based on the fuel cell high-efficiency purging device and method provided by the present invention, the specific purging process in this embodiment includes:

[0067] The fuel cell stack is operated at 1600 mA / cm 2 After running stably at the current density for 20 minutes, the purging process begins upon receiving the shutdown and purging command.

[0068] During the purging process, the impedance value of the fuel cell is monitored in real time, and the rate of change of the impedance value k is compared with a given empirical constant c = 2.

[0069] (1) When k≤2, the purging process is in the first stage:

[0070] The air flow rate into the fuel cell stack is adjusted to v1 = 2745 L / min using gas flow meter 1; the air exhaust throttle valve 4 is adjusted to the maximum opening θ1 = 90°; the opening and closing time of solenoid valve I 5 is controlled (t1 = 0.3 s, t2 = 1 s) to make hydrogen pulse emission; the hydrogen-oxygen pressure difference is adjusted to Δp1 = 40 kPa; and the speed of reflux pump 7 is adjusted to r1 = 1000 r / min.

[0071] (2) When k > 2, the purging process is in the second stage:

[0072] Reduce airflow to v2 = 1372 L / min; control pulse air emission through air exhaust throttle valve 4, with an opening angle of 90° and a closing angle of 10°, and a time interval of 2s between opening and closing; control the opening and closing time of solenoid valve I5 (t3 = 0.3s, t4 = 10s) to achieve pulse hydrogen emission; reduce the hydrogen-oxygen pressure difference to Δp2 = 20 kPa; increase the speed of reflux pump 7 to r2 = 5000 r / min;

[0073] (3) When k changes from k>2 to k≤2, it indicates that the purging process has entered the third stage, that is, the fuel cell stack is in a state of dynamic water equilibrium and the purging can be ended.

[0074] The battery airflow rate during the entire purging process in this embodiment is as follows: Figure 3 As shown, the air and hydrogen pressure changes throughout the purging process are as follows: Figure 4 As shown.

[0075] The fuel cell stack in this embodiment underwent a -30°C low-temperature start-up verification after purging. Compared with conventional purging methods, the purging time of the stack purged using the purging device and method provided by this invention can be shortened by 50%, and the purging energy consumption can be reduced by 50%.

[0076] The fuel cell high-efficiency purging device and method provided by this invention can determine the internal drainage status of the battery by the rate of change of battery impedance during the purging process, and then set the purging parameters for the air and hydrogen sides differently to achieve rapid removal of water inside the battery, shorten the downtime for purging, reduce purging power consumption, and avoid battery damage caused by freezing due to low-temperature storage.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for efficient purging of a fuel cell, characterized in that, A high-efficiency purging device for fuel cells is adopted, the device including a gas flow meter, a pressure sensor I, an air exhaust throttle valve, a solenoid valve I, a gas-liquid separator, a reflux pump and a pressure sensor II; The gas flow meter and the pressure sensor I are installed on the air inlet pipe of the fuel cell, and the air exhaust throttle valve is installed on the air outlet pipe of the fuel cell. The pressure sensor II and the proportional valve are installed on the hydrogen inlet pipe of the fuel cell, and the solenoid valve I is installed on the hydrogen outlet pipe of the fuel cell. The fuel cell is provided with a hydrogen reflux branch, and the hydrogen outlet pipeline and the hydrogen inlet pipeline are connected through the hydrogen reflux branch; the gas-liquid separator and the reflux pump are arranged in sequence on the hydrogen reflux branch, the inlet of the gas-liquid separator is connected to the hydrogen outlet pipeline, and the gas outlet is connected to the reflux pump. The hydrogen return branch is used to return the hydrogen discharged from the fuel cell to the hydrogen inlet pipeline after removing liquid water through the gas-liquid separator. The method includes: Once the fuel cell stack receives a shutdown purging command, the purging process begins. With fuel cell stacks at 100mA / cm 2 The air flow rate v0, the opening and closing time t0 and t'0 of solenoid valve I, the hydrogen-oxygen pressure difference Δp0, and the reflux pump speed r0 are used as reference values. During the purging process, the impedance value of the fuel cell stack is detected in real time and the rate of change of impedance k is compared with the empirical constant c. The empirical constant c is an empirical parameter obtained through experiments and is related to the fuel cell stack structure, the purging gas flow rate, the air and hydrogen inlet pressure, and the purging temperature. (1) If k≤c, the purging process is in the first stage. The following strategies are used to remove free water from the flow channel and porous medium: On the cathode side: the air flow rate into the fuel cell stack is adjusted to v1=10v0 by the gas flow meter; the air exhaust throttle valve is adjusted to the maximum opening θ1; On the anode side: the opening and closing time of solenoid valve I is controlled to t1=3t0, t2=t'0, so that hydrogen is emitted in a pulse, where t1 represents the valve opening time and t2 represents the valve closing time; according to the pressure values ​​of air and hydrogen entering the fuel cell stack monitored by pressure sensor I and pressure sensor II, the hydrogen-oxygen pressure difference is adjusted to Δp1=4Δp0 by the proportional valve set on the hydrogen inlet pipe; the speed of the return pump is adjusted to r1=r0; (2) If k > c, the purging process is in the second stage. The following strategies are used to remove residual liquid water and film water in the flow channel and diffusion layer: On the cathode side: reduce the air flow rate to v2 = (4~6)v0; control the air pulse emission through the air tail throttle valve; On the anode side: reduce the hydrogen-oxygen pressure difference to Δp2 = (1~2)Δp0; control the opening and closing time of solenoid valve I to t3 = (3~5)t0, t4 = (8~10)t'0, so that hydrogen is emitted in a pulse, where t3 represents the valve opening time and t4 represents the valve closing time; increase the speed of the return pump to r2 = (3~5)r0; (3) When k changes from k>c to k≤c, it indicates that the purging process has entered the third stage, that is, the fuel cell stack is in a state of dynamic water equilibrium and the purging ends.

2. The fuel cell high-efficiency purging method according to claim 1, characterized in that, The rate of change k of the fuel cell stack impedance is calculated using the following formula: In the formula: z t Let t be the impedance value measured at time t, and Δt be the time step.

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