Fault diagnosis method for proton exchange membrane of fuel cell

Abstract

The present invention discloses a method for diagnosing a proton exchange membrane fault of a fuel cell, which includes S1, obtaining the hydrogen inlet humidity, hydrogen outlet humidity, fuel cell output voltage and anode temperature of the fuel cell; S2, judging whether the fuel cell output voltage is less than the set voltage, if yes, executing step S3, if not, executing step S1; S3, diagnosing the fuel cell fault type according to the hydrogen inlet humidity, hydrogen outlet humidity, air inlet humidity, air outlet humidity and anode temperature; wherein the fuel cell fault type includes membrane dry fault and water flooding fault; S4, when the fault type is water flooding fault, obtaining the anode pressure and cathode pressure; S5, diagnosing the water flooding fault as cathode water flooding or anode water flooding according to the anode pressure and cathode pressure. The present invention can facilitate timely identification of fuel cell faults during the operation of the fuel cell, and provide convenience for timely elimination of the faults.

Description

Technical Field

[0001] The invention relates to the technical field of fuel cells, and in particular to a method for diagnosing faults of proton exchange membranes of fuel cells. Background Art

[0002] The main function of the proton exchange membrane is to conduct hydrogen ions, isolate fuel and oxidants, and block electrons. It is the core component of the proton exchange membrane fuel cell. Hydrogen ions cannot pass through the proton exchange membrane alone, and water molecules are the medium for passing through the membrane. Therefore, the proton exchange membrane needs a certain water content when working, and too high a water content will cause water flooding failure.

[0003] In practical applications, there are many factors that affect the water content of the proton exchange membrane. For example, temperature affects the diffusion of water. The higher the temperature, the greater the diffusion, which will aggravate the loss of water. Excessive humidification of the hydrogen supply system and the oxygen supply system will lead to the accumulation of water. The pressure difference on both sides of the proton exchange membrane will affect the migration of water between the anode and the cathode. Whether the water content of the proton exchange membrane is too high or too low, it will cause damage to the proton exchange membrane, thereby affecting the service life of the proton exchange membrane. Keeping the proton exchange membrane in a suitable working environment is the key to improving the service life of the proton exchange membrane fuel cell. To keep the proton exchange membrane in a suitable working environment, it is necessary to identify the fault of the proton exchange membrane in time. When the fault is identified, the existing method is to use ohmic internal resistance for measurement. This measurement method uses a modeling estimation method, and the process is relatively complicated and is not applicable in real-time measurement.

[0004] Therefore, how to identify fuel cell failures in real time is one of the important issues that need to be solved urgently in this field. Summary of the invention

[0005] The purpose of the present invention is to provide a method for diagnosing fuel cell proton exchange membrane faults, so as to timely identify fuel cell faults during fuel cell operation and provide convenience for timely elimination of faults.

[0006] The present invention provides a method for diagnosing a fuel cell proton exchange membrane fault, which comprises the following steps:

[0007] S1, obtaining the hydrogen inlet humidity, hydrogen outlet humidity, fuel cell output voltage and anode temperature of the fuel cell;

[0008] S2, determine whether the output voltage of the fuel cell is less than the set voltage, if yes, execute step S3, if no, execute step S1;

[0009] S3, diagnosing the fuel cell fault type according to the hydrogen inlet humidity, the hydrogen outlet humidity, the air inlet humidity, the air outlet humidity and the anode temperature; wherein the fuel cell fault type includes a membrane dry fault and a water flooding fault;

[0010] S4, when the fault type is a flooding fault, obtaining the anode pressure and the cathode pressure;

[0011] S5, diagnose the flooding fault as cathode flooding or anode flooding according to the anode pressure and the cathode pressure.

[0012] In the fuel cell proton exchange membrane fault diagnosis method as described above, optionally, in step S2, the voltage is set to 85% to 90% of the rated voltage.

[0013] In the above-mentioned fuel cell proton exchange membrane fault diagnosis method, optionally, step S3 is:

[0014] Determine whether the first condition is met. If yes, it is determined to be a membrane dry fault; if not, it is a flooding fault; wherein, the first condition is: the anode temperature is greater than the set temperature, and the hydrogen outlet humidity is greater than 1.1 times the hydrogen inlet humidity.

[0015] In the above-mentioned fuel cell proton exchange membrane fault diagnosis method, optionally, step S5 includes:

[0016] Determine whether the anode pressure and the cathode pressure meet a second condition, if yes, it is cathode flooding, if no, it is anode flooding;

[0017] The second condition is that the pressure migration direction generated by the anode pressure and the cathode pressure is toward the cathode, or the pressure migration direction generated by the anode pressure and the cathode pressure is toward the anode and the pressure migration is less than a set value.

[0018] In the fuel cell proton exchange membrane fault diagnosis method as described above, optionally, the set temperature is set at a value of 88 to 95 degrees Celsius.

[0019] In the fuel cell proton exchange membrane fault diagnosis method as described above, optionally, the second condition satisfies the following formula:

[0020]

[0021] Among them, λ is a constant coefficient, P yi is the cathode pressure, P ya is the anode pressure, d is the average pore size of the proton membrane, S is the area of ​​the proton exchange membrane, l is the thickness of the proton exchange membrane, v 0 is the set value of pressure migration velocity, and η is the porosity of the proton membrane.

[0022] In the fuel cell proton exchange membrane fault diagnosis method as described above, optionally, the set value of the pressure migration speed is a plurality of values ​​that are positively correlated with the fuel cell output current; the plurality of set values ​​and the corresponding current values ​​are preset in a set value table of the pressure migration speed according to a corresponding relationship;

[0023] The method for obtaining the set value includes the following steps:

[0024] S501, obtaining the output current of the fuel cell;

[0025] S502, searching the corresponding pressure migration speed from the set value table according to the output current of the fuel cell;

[0026] S503, taking the pressure migration speed found as a set value.

[0027] Compared with the prior art, the present invention distinguishes between membrane dry fault and water flooding fault by measuring the hydrogen inlet humidity, hydrogen outlet humidity, fuel cell output voltage and anode temperature on the fuel cell. Furthermore, the anode pressure and cathode pressure are used to determine whether the type of water flooding fault is cathode flooding or anode flooding. By using this judgment method, fault diagnosis can be accurately performed without measuring the ohmic internal resistance of the fuel cell. The present invention bypasses the parameter of the ohmic internal resistance of the fuel cell, which is not easy to measure, making the diagnosis process more convenient.

[0028] During operation, the present invention further diagnoses flooding faults through the relationship between anode pressure and cathode pressure, and specifies the types of flooding faults into cathode flooding and anode flooding. Thus, the fault types are specified to the extent that the faults can be eliminated directly by controlling the corresponding parameters, which provides convenience for eliminating the faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flowchart of the steps of the fuel cell proton exchange membrane fault diagnosis method provided by the present invention;

[0030] Figure 2 It is a flowchart of some specific steps in step S5. DETAILED DESCRIPTION

[0031] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, but should not be construed as limiting the present invention.

[0032] In the prior art, fuel cell fault diagnosis, especially the distinction between membrane dry fault and flooding fault, is mainly judged by the ohmic internal resistance of the fuel cell. When the ohmic internal resistance is too large, it can be judged as a membrane dry fault. However, in practical applications, the measurement of ohmic internal resistance is not convenient. In the prior art, it is mostly estimated by using a model based on a large amount of data. This method is currently not suitable for real-time detection of working fuel cells. To this end, the present invention proposes the following improvements, as shown in the following embodiments.

[0033] Example 1

[0034] Please refer to Figure 1 This embodiment proposes a fuel cell proton exchange membrane fault diagnosis method, which includes the following steps:

[0035] S1, obtain the hydrogen inlet humidity, hydrogen outlet humidity, fuel cell output voltage and anode temperature of the fuel cell. The hydrogen inlet humidity, hydrogen outlet humidity, fuel cell output voltage and anode temperature are used to diagnose whether there is a fault, and if there is a fault, whether the fault type is a membrane dry fault or a water flooding fault. Specifically, whether there is a large drop in the fuel cell output voltage is used to determine whether there is a fault. The hydrogen inlet humidity, hydrogen outlet humidity and anode temperature are used to diagnose whether the fault type is a membrane dry fault or a water flooding fault.

[0036] In specific implementation, the humidity at the hydrogen inlet and the humidity at the hydrogen outlet can be detected by a humidity sensor, and the sensor for measuring the humidity at the hydrogen inlet is arranged at the hydrogen inlet of the fuel cell, specifically, it should be located at the end of the hydrogen supply system. The humidity at the hydrogen outlet is also detected by a humidity sensor, and the sensor for measuring the humidity at the hydrogen outlet is arranged at the hydrogen outlet of the fuel cell.

[0037] The output voltage of the fuel cell can be measured by a voltage sensor, and the anode temperature can be measured by a temperature sensor. The temperature sensor is arranged on the anode side of the proton exchange membrane to measure the temperature of the anode of the fuel cell.

[0038] The fuel cell output voltage is used to determine whether there is a fault. The fuel cell membrane faults are mainly divided into membrane dry faults and water flooding faults, and water flooding faults are further divided into cathode water flooding and anode water flooding. In specific implementation, firstly determine whether there is a membrane dry fault or a water flooding fault by the fuel cell output voltage, which can be achieved specifically through step S2.

[0039] S2, determine whether the output voltage of the fuel cell is less than the set voltage. If yes, execute step S3, if not, execute step S1. Specifically, the set voltage can be a fixed value, and the set voltage should be less than the rated voltage of the fuel cell under normal conditions. Specifically, the set voltage can be 85%-90% of the rated voltage. In this way, when the detected output voltage of the fuel cell is less than 85%-90% of the rated voltage, it means that the output voltage of the fuel cell has dropped by 10% to 20%, that is, the fuel cell has a membrane dry fault or a flooding fault. If it is not lower than the set voltage, it means that the fuel cell has no obvious fault. At this time, it is necessary to repeat step S1 to collect the signals required for diagnosis.

[0040] Through the above steps, it is possible to determine whether there is a fault in the fuel cell, but it is impossible to determine the specific type of fault. In order to distinguish between a membrane dry fault and a water flooding fault, the present embodiment also includes step S3. Through step S3, the hydrogen inlet humidity, the hydrogen outlet humidity, and the anode temperature are used to distinguish between the membrane dry fault and the water flooding fault. Specifically, step S3 is to diagnose the fuel cell fault type according to the hydrogen inlet humidity, the hydrogen outlet humidity and the anode temperature; wherein the fuel cell fault types include membrane dry fault and water flooding fault.

[0041] Specifically, the distinction between membrane dry failure and flooding failure is as follows:

[0042] Determine whether the first condition is met. If yes, it is determined to be a membrane dry fault; if not, it is a flooding fault; wherein the first condition is: the anode temperature is greater than the set temperature, and the hydrogen outlet humidity is greater than 1.1 times the hydrogen inlet humidity. In actual application, the membrane dry fault occurs at the anode. The source of the anode water mainly includes the humidifier of the hydrogen supply system, the osmotic effect of the cathode water, and the water flowing to the anode under the action of pressure migration, and the reduction of the anode water is mainly due to the diffusion of water, that is, the water flowing out with the residual hydrogen. When the humidity of the residual hydrogen is too high, it means that the anode water is being lost. Since the output voltage of the fuel cell has dropped significantly, when the humidity of the residual hydrogen is too high, it means that a membrane dry fault is occurring. In specific implementation, the set temperature is 88 to 95 degrees Celsius, such as 89, 90, 91, 92, 93, 94 degrees Celsius, etc. In this way, it is possible to avoid using the ohmic internal resistance of the fuel cell to identify whether a membrane dry fault has occurred.

[0043] Through the above steps, it is possible to distinguish between membrane dry fault and flooding fault. However, flooding fault is divided into cathode flooding and anode flooding. The means used to eliminate cathode flooding and anode flooding are completely different. In order to prepare for accurate fault elimination, it is necessary to distinguish between cathode flooding and anode flooding. In order to distinguish between cathode flooding and anode flooding, this embodiment also includes steps S4 and S5. Specifically, step S4 is to obtain the anode pressure and cathode pressure when the fault type is a flooding fault; wherein the anode pressure can be obtained by a pressure sensor installed in the anode, and the cathode pressure can be obtained by a pressure sensor installed in the cathode. In specific implementation, the anode pressure can be the average value of the pressure values ​​detected by multiple sensors, and the cathode pressure can also be the average value of the pressure values ​​detected by multiple sensors. Step S5 is to diagnose the flooding fault as cathode flooding or anode flooding based on the anode pressure and the cathode pressure. That is, the anode pressure and the cathode pressure are used as parameters to distinguish between cathode flooding and anode flooding.

[0044] In specific implementation, distinguishing between cathode flooding and anode flooding is to promote the use of the fault diagnosis method for real-time fuel cell fault diagnosis and use the diagnosis results as the basis for eliminating the fault. In order to achieve the distinction between cathode pressure and anode pressure, step S5 is specifically implemented in the following way.

[0045] Step S5 is specifically as follows:

[0046] It is determined whether the anode pressure and the cathode pressure meet the second condition, if yes, it is cathode flooding, if no, it is anode flooding. The second condition is that the pressure migration direction generated by the anode pressure and the cathode pressure is toward the cathode, or the pressure migration direction generated by the anode pressure and the cathode pressure is toward the anode and the pressure migration is less than a set value.

[0047] During use, the difference between anode flooding and cathode flooding is that anode flooding means too much water at the anode, while cathode flooding means too much water at the cathode. The electro-drag effect is mainly that water flows from the anode to the cathode under the electro-drag effect. The water produced by the chemical reaction is mainly produced at the cathode. The reverse osmosis effect migrates from the side with more water to the other side. The water in the humidification will increase the water in the cathode and anode, while the diffusion effect will cause the water in the cathode and anode to decrease. When a flooding fault occurs, the electro-drag effect decreases, the chemical reaction rate decreases, and the main variable in the whole process is the pressure migration without changing the humidification amount. Therefore, the pressure migration can be used to distinguish between cathode flooding and anode flooding.

[0048] In specific implementation, the second condition satisfies the following formula:

[0049]

[0050] Among them, λ is a constant coefficient, P yi is the cathode pressure, Pya is the anode pressure, d is the average pore size of the proton membrane, S is the area of ​​the proton exchange membrane, l is the thickness of the proton exchange membrane, v 0 is the set value of pressure migration velocity, and η is the porosity of the proton membrane.

[0051] In implementation, in order to have better accuracy, the set value of the pressure migration speed is related to the current current speed, that is, the set value of the pressure migration speed is related to the strength of the electric drag effect. More specifically, the set value of the pressure migration speed is a plurality of values ​​that are positively correlated with the output current of the fuel cell; the plurality of set values ​​and the corresponding current values ​​are preset in the set value table of the pressure migration speed according to the corresponding relationship.

[0052] Please refer to Figure 2 , the method for obtaining the set value includes the following steps:

[0053] S501, obtaining the output current of the fuel cell; in specific implementation, obtaining the output current of the fuel cell can be achieved through a current sensor.

[0054] S502, searching the corresponding pressure migration speed from the set value table according to the output current of the fuel cell. Specifically, searching the corresponding pressure migration speed from the set value table according to the detection result of the current sensor.

[0055] S503, taking the pressure migration speed found as a set value.

[0056] Through the above method, the judgment accuracy of the second condition can be improved, making the judgment result more accurate.

[0057] Embodiment 2,

[0058] This embodiment is a further improvement on the basis of the embodiment 1, and the similarities are not repeated here, and only the differences are described below.

[0059] The difference between this embodiment and embodiment 1 mainly lies in the distinction between membrane dry failure and water flooding failure.

[0060] In step S3, the first condition is: within a period of time, the anode temperature is greater than the set temperature, and within a period of time, the ratio of the hydrogen outlet humidity to the hydrogen inlet humidity decreases from greater than 1.2 to close to 1, such as a decrease close to 1.05. In the early stage of membrane dry failure, the anode temperature rises, which will lead to enhanced anode diffusion and increased moisture in residual hydrogen. When the membrane dry failure occurs, the anode moisture decreases, and the moisture discharged by diffusion decreases. The above method can be used to distinguish between cathode flooding and anode flooding.

[0061] Compared with the prior art, the present embodiments 1 and 2 distinguish between membrane dry fault and water flooding fault by using the hydrogen inlet humidity, hydrogen outlet humidity, fuel cell output voltage and anode temperature on the fuel cell. Furthermore, the anode pressure and cathode pressure are used to determine whether the type of water flooding fault is cathode flooding or anode flooding. By using this judgment method, fault diagnosis can be accurately performed without measuring the ohmic internal resistance of the fuel cell. The present invention bypasses the parameter of the ohmic internal resistance of the fuel cell, which is not easy to measure, making the diagnosis process more convenient.

[0062] During operation, the present invention further diagnoses flooding faults through the relationship between anode pressure and cathode pressure, and specifies the types of flooding faults into cathode flooding and anode flooding. Thus, the fault types are specified to the extent that the faults can be eliminated directly by controlling the corresponding parameters, which provides convenience for eliminating the faults.

[0063] The above describes in detail the structure, features and effects of the present invention based on the embodiments shown in the drawings. The above is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the drawings. Any changes made according to the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which still do not exceed the spirit covered by the description and drawings, should be within the protection scope of the present invention.

Claims

1. A method for diagnosing a fuel cell proton exchange membrane fault, characterized in that: The following steps are included: S1, obtaining the hydrogen inlet humidity, hydrogen outlet humidity, fuel cell output voltage and anode temperature of the fuel cell; S2, determine whether the output voltage of the fuel cell is less than the set voltage, if yes, execute step S3, if no, execute step S1; S3, diagnosing the fuel cell fault type according to the hydrogen inlet humidity, the hydrogen outlet humidity and the anode temperature; wherein the fuel cell fault types include membrane dry fault and water flooding fault; including: judging whether the first condition is met, if yes, it is judged as a membrane dry fault; if not, it is a water flooding fault; wherein the first condition is: the anode temperature is greater than the set temperature, and the hydrogen outlet humidity is greater than 1.1 times the hydrogen inlet humidity; S4, when the fault type is a flooding fault, obtaining the anode pressure and the cathode pressure; S5, diagnosing the flooding fault as cathode flooding or anode flooding according to the anode pressure and the cathode pressure; Step S5 includes determining whether the anode pressure and the cathode pressure meet a second condition, if yes, it is cathode flooding, if no, it is anode flooding; wherein the second condition is that the pressure migration direction generated by the anode pressure and the cathode pressure is toward the cathode, or the pressure migration direction generated by the anode pressure and the cathode pressure is toward the anode and the pressure migration is less than a set value; The second condition satisfies the following formula, ； in, is a constant coefficient, is the cathode pressure, is the anode pressure, is the average pore size of the proton membrane, is the area of ​​the proton exchange membrane, is the thickness of the proton exchange membrane, is the set value of pressure migration speed, is the porosity of the proton membrane.

2. The fuel cell proton exchange membrane fault diagnosis method according to claim 1, characterized in that: In step S2, the voltage is set to 85% to 90% of the rated voltage.

3. The fuel cell proton exchange membrane fault diagnosis method according to claim 1, characterized in that: The set temperature is between 88 and 95 degrees Celsius.

4. The fuel cell proton exchange membrane fault diagnosis method according to claim 1, characterized in that: The set values ​​of the pressure migration speed are multiple values ​​that are positively correlated with the output current of the fuel cell; the multiple set values ​​and the corresponding current values ​​are preset in the set value table of the pressure migration speed according to the corresponding relationship; The method for obtaining the set value includes the following steps: S501, obtaining the output current of the fuel cell; S502, searching the corresponding pressure migration speed from the set value table according to the output current of the fuel cell; S503, taking the pressure migration speed found as a set value.

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