A method for hydrogen removal from an anode of a fuel cell based on multipoint voltage

Abstract

The present application relates to the technical field of fuel cell, and particularly discloses a fuel cell anode hydrogen discharge method based on multi-point voltage, which comprises the following steps: obtaining the voltage at the anode inlet and the anode outlet of each single cell during the operation of the fuel cell; calculating the average value and the root mean square value of the voltage at the anode inlet and the anode outlet of the fuel cell; regarding each single cell as a half cell with two gas circuits in series and two electric circuits in parallel, and calculating the activation voltage loss, the ohmic loss and the concentration difference loss of the two half cells; further calculating the stack state evaluation factor based on the average value and the root mean square value of the voltage calculated in step 2; dividing the stack failure level into four levels based on the stack state evaluation factor calculated in step 3; and performing different treatments according to different stack failure levels. The present application can effectively improve the stack performance and reduce the hydrogen consumption by using the multi-point voltage monitoring method, formulating the detailed stack state grading, and accurately formulating the hydrogen discharge strategy.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, specifically relating to a method for hydrogen removal from the anode of a fuel cell based on multi-point voltage. Background Technology

[0002] Fuel cells have attracted widespread attention due to their pollution-free and high-efficiency characteristics. They can convert hydrogen and oxygen into electricity and water without emitting any pollutants in the process.

[0003] Therefore, fuel cells are an ideal power source for the transportation sector. However, fuel cells are significantly affected by the environment; the on-board environment and operating conditions greatly influence their durability and lifespan, limiting their commercialization. Among these factors, the purity of the anode gas has a substantial impact. During fuel cell operation, nitrogen from the cathode side permeates to the anode, reducing the purity of the hydrogen on the anode side. While fuel cell systems employ hydrogen recirculation devices to conserve hydrogen, this leads to nitrogen accumulation on the anode side, ultimately reducing fuel cell performance. Therefore, maintaining a high hydrogen concentration at the fuel cell anode is crucial for ensuring optimal fuel cell output performance.

[0004] Current technology primarily relies on periodically venting impure hydrogen to maintain the hydrogen concentration at the anode. However, the large active surface area of ​​commercially available fuel cells leads to uneven component distribution within the fuel cell surface, resulting in internal lateral currents. Consequently, the voltage measured at different locations within the fuel cell varies. This phenomenon means that the monitored cell voltage data cannot accurately reflect the true state of the fuel cell. Hydrogen venting strategies that heavily rely on cell voltage data cannot meet the actual needs of fuel cells, leading to increased hydrogen consumption and reduced performance. Summary of the Invention

[0005] The purpose of this invention is to provide a hydrogen removal method for fuel cell anodes based on multi-point voltage, which mainly solves the problems that existing hydrogen removal methods cannot meet the actual needs of fuel cells, such as high hydrogen consumption and reduced fuel cell performance.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for hydrogen removal from the anode of a fuel cell based on multi-point voltage:

[0007] S1. Obtain the voltage at the anode inlet and anode outlet of each individual cell during fuel cell operation;

[0008] S2. Calculate the average voltage and root mean square voltage at the anode inlet and outlet of the fuel cell; treat each single cell as two half-cells with gas paths connected in series and circuits connected in parallel, and calculate the activation voltage loss, ohmic loss and concentration loss of each half-cell respectively.

[0009] S3. Based on the average voltage and root mean square voltage calculated in step 2, further calculate the stack condition assessment factor.

[0010] S4. Based on the stack condition assessment factor calculated in step 3, the stack fault level is divided into four levels;

[0011] S5. Different handling is performed according to different stack fault levels. When the stack is in state 1, the hydrogen inlet solenoid valve, circulation pump, and hydrogen discharge valve maintain the previous working state. When the stack is in state 2, the hydrogen inlet solenoid valve and circulation pump maintain the previous working state, and the opening frequency of the hydrogen discharge valve increases by A%. When the stack is in state 3, based on the activation voltage loss, ohmic loss, and concentration loss of the two half-cells calculated in step 2, the performance evaluation factor k of the single cell is calculated. If k = -1 or k = 0, the opening degree of the hydrogen inlet solenoid valve increases by B%, the circulation pump speed decreases by C%, and the opening frequency of the hydrogen discharge valve increases by D%. If k = 1, an alarm is triggered. When the stack is in state 4, similarly based on the activation loss, ohmic loss, and concentration loss of the two half-cells calculated in step 2, the performance evaluation factor k of the single cell is calculated. If k = -1 or k = 0, the opening degree of the hydrogen inlet solenoid valve increases by B%, the circulation pump speed decreases by C%, and the opening frequency of the hydrogen discharge valve increases by D%. If k = 1, an alarm is triggered.

[0012] Preferably, the performance evaluation factor k of a single cell in step 5 is calculated using the following formula:

[0013]

[0014] The value of k follows the following relationship: if k ≤ -1, k = -1; if -1 <k<1,k=0;if1<k,k=1,

[0015] Among them, V inlet V outlet These are the voltages at the anode inlet and anode outlet of a single cell during fuel cell operation, ΔU and ΔU, respectively. con_inlet , ΔU con_outlet These represent the concentration losses of the two semi-single cells, where n is a coefficient ranging from 0.3 to 0.5.

[0016] Preferably, the formula for calculating the stack condition assessment factor in step 3 is:

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023] in, σ represents the average voltage at the anode inlet and outlet of the fuel cell. V This represents the root mean square average voltage at the anode inlet and outlet of the fuel cell.

[0024] Preferably, in step 4, the stack fault levels are divided into state 1, state 2, state 3, and state 4. When the average voltage of the anode inlet and anode outlet of all individual cells is between K... 1_up and K 1_down When the voltage difference between K and K is between K, the stack fault level is state 1; when the average voltage of the anode inlet and anode outlet of a single cell is between K and K, the stack fault level is state 1. 2_up and K 2_down Between, and beyond [K 1_down K 1_up When the voltage is within the specified range, the stack fault level is state 2; when the average voltage of the anode inlet and anode outlet of a single cell is between K... 3_up and K 3_down Between, and beyond [K 2_down K 2_up When the voltage exceeds [K], the stack fault level is State 3; when the average voltage of the anode inlet and anode outlet of a single cell exceeds [K], the stack fault level is State 3. 3_down K 3_up When the range is within 4, the stack fault level is state 4.

[0025] The beneficial effects of this invention are as follows: This invention utilizes a multi-point voltage monitoring method to obtain more accurate battery status information, avoiding the isolation of relying on voltage data from a single location; it also formulates detailed stack status classifications and accurate hydrogen removal strategies, which can effectively improve stack performance and reduce hydrogen consumption. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structural principle of the fuel cell system based on multi-point voltage according to the present invention;

[0027] Figure 2 This is a schematic diagram of multi-point voltage acquisition in the fuel cell system based on multi-point voltage according to the present invention;

[0028] Figure 3 This is a flowchart of the hydrogen removal method for fuel cell anodes based on multi-point voltage according to the present invention.

[0029] The diagram is labeled as follows: 1. Fuel cell stack; 2. First voltage detection module; 3. Second voltage detection module; 4. Gas-liquid separator; 5. Hydrogen discharge valve; 6. Control module; 7. Circulation pump; 8. Ejector; 9. Hydrogen inlet solenoid valve; 10. Pressure regulating solenoid valve; 11. Hydrogen cylinder; 12. Pipeline; 13. Control signal line; 14. Medium pressure sensor; 15. Hydrogen inlet temperature sensor; 16. Hydrogen inlet pressure sensor; 17. Hydrogen outlet temperature sensor; 18. Hydrogen outlet pressure sensor. Detailed Implementation

[0030] 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. 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.

[0031] Example

[0032] As attached Figure 1-3 As shown, this embodiment provides the following technical solution:

[0033] A method for hydrogen removal from the anode of a fuel cell based on multi-point voltage is applicable to various commercially sized fuel cells, such as... Figure 1 As shown, the fuel cell system based on multi-point voltage in this embodiment includes a fuel cell stack 1, a first voltage detection module 2, a second voltage detection module 3, a gas-liquid separator 4, a hydrogen discharge valve 5, a control module 6, a circulation pump 7, an ejector 8, a hydrogen inlet solenoid valve 9, a pressure regulating solenoid valve 10, a hydrogen cylinder 11, a pipeline 12, a control signal line 13, a medium-pressure sensor 14, a hydrogen inlet temperature sensor 15, a hydrogen inlet pressure sensor 16, a hydrogen outlet temperature sensor 17, and a hydrogen outlet pressure sensor 18. The hydrogen inlet of the fuel cell stack 1 is sequentially connected to the hydrogen cylinder 11, the pressure regulating solenoid valve 10, the hydrogen inlet solenoid valve 9, and the ejector 8 via the pipeline 12. The hydrogen outlet of the fuel cell stack 1 is connected to the gas-liquid separator 4 and the hydrogen discharge valve 5 via the pipeline 12. A circulation pump 7 is also connected between the gas-liquid separator 4 and the hydrogen inlet pipeline 12. The hydrogen inlet pipe 12 is equipped with a hydrogen inlet temperature sensor 15 and a hydrogen inlet pressure sensor 16, and the hydrogen outlet pipe 12 is equipped with a hydrogen outlet temperature sensor 17 and a hydrogen outlet pressure sensor 18. A pressure regulating solenoid valve 10 is installed on the pipe 12 between the pressure regulating solenoid valve 10 and the hydrogen inlet solenoid valve 9. The pressure regulating solenoid valve 10, the hydrogen inlet solenoid valve 9, the circulation pump 7, the first voltage detection module 2, the second voltage detection module 3, and the hydrogen discharge valve 5 are all connected to the control module 6 via control signal lines 13. The first voltage detection module 2 and the second voltage detection module 3 are respectively positioned at the anode inlet and anode outlet of the fuel cell stack 1 to acquire two sets of voltage data for the same battery cell.

[0034] The hydrogen cylinder 11 is used to store high-pressure hydrogen. The pressure regulating solenoid valve 10 is used to reduce the pressure of the high-pressure hydrogen to medium pressure. The hydrogen inlet solenoid valve 9 is located at the inlet of the ejector 8 and is used to control the switching of the hydrogen source. The ejector 8 is located at the inlet of the fuel cell stack 1 and is used to recover the hydrogen discharged from the outlet of the fuel cell stack 1. The circulation pump 7 is used to circulate unreacted hydrogen. The gas-liquid separator 4 is located between the outlet of the fuel cell stack 1 and the hydrogen discharge valve 5 and is used to separate liquid water in the gas at the outlet of the anode simulator of the fuel cell stack 1. The hydrogen discharge valve 5 is located at the hydrogen outlet of the gas-liquid separator 4. The control module 6 receives feedback signals from the sensor unit, the voltage acquisition module and the hydrogen control unit, performs hydrogen discharge strategy calculations and transmits control commands to the hydrogen control unit. The medium-pressure sensor 14 is used to detect the pressure of hydrogen in the pipeline between the pressure regulating solenoid valve 10 and the hydrogen inlet solenoid valve 9. The hydrogen inlet pressure sensor 16 is used to detect the hydrogen pressure entering the fuel cell stack 1; the hydrogen inlet temperature sensor 15 is used to detect the hydrogen temperature entering the fuel cell stack 15; the hydrogen outlet pressure sensor 18 is used to detect the hydrogen pressure exiting the fuel cell stack 1; and the hydrogen outlet temperature sensor 17 is used to detect the hydrogen temperature exiting the fuel cell stack 1.

[0035] Reference Figure 3 The above-mentioned method for controlling hydrogen emission from the anode in a fuel cell system based on multi-point voltage is as follows:

[0036] S1. Obtain the voltage at the anode inlet and anode outlet of each individual cell during fuel cell operation;

[0037] S2. Calculate the average voltage and root mean square voltage at the anode inlet and outlet of the fuel cell; treat each single cell as two half-cells with gas paths connected in series and circuits connected in parallel, and calculate the activation voltage loss, ohmic loss and concentration loss of each half-cell respectively.

[0038] S3. Based on the average voltage and root mean square voltage calculated in step 2, further calculate the stack condition assessment factor.

[0039] S4. Based on the stack condition assessment factor calculated in step 3, the stack fault level is divided into four levels;

[0040] S5. Different handling is performed according to different stack fault levels. When the stack is in state 1, a fixed hydrogen venting mode is implemented, and the hydrogen inlet solenoid valve, circulation pump, and hydrogen venting valve maintain the previous operating state. When the stack is in state 2, the hydrogen inlet solenoid valve and circulation pump maintain the previous operating state, and the opening frequency of the hydrogen venting valve is increased by 5%. When the stack is in state 3, based on the concentration loss of the two half-cells calculated in step 2, the performance evaluation factor k of the single cell is calculated. If k = -1 or k = 0, it is determined that there is no performance degradation, and the hydrogen inlet solenoid valve is opened. If the concentration loss of the two half-cells is increased by 1.5%, the circulation pump speed is decreased by 1.5%, and the hydrogen discharge valve opening frequency is increased by 8%. If k=1, the battery is considered to have experienced lifespan degradation, and an alarm is triggered. When the stack is in state 4, based on the concentration loss of the two half-cells calculated in step 2, the performance evaluation factor k of the single cell is calculated. If k=-1 or k=0, no performance degradation is determined, the hydrogen inlet solenoid valve opening degree is increased by 1.5%, the circulation pump speed is decreased by 1.5%, and the hydrogen discharge valve opening frequency is increased by 8%. If k=1, the battery is considered to have experienced lifespan degradation, and an alarm is triggered.

[0041] Specifically, the voltages at the anode inlet and outlet of each single cell during fuel cell operation, obtained in step 1, are denoted as Va. inlet V outlet .

[0042] Step 2: Based on the multi-point voltage of each single cell, the fuel cell unit is assumed to consist of two half-cells connected in series in the gas path and in parallel in the circuit, and the activation voltage loss, ohmic loss and concentration loss of the two half-cells are calculated respectively.

[0043] As is well known, the voltage loss of a fuel cell depends on the cell's operating conditions and current density. By obtaining the actual operating conditions of the fuel cell and the voltages at the anode inlet and outlet, the activation voltage loss, ohmic loss, and concentration polarization of the fuel cell can be analyzed.

[0044] E cell =E0-ΔU act -ΔU ohm -ΔU con (1)

[0045] Among them, E cell Let E and E0 be the fuel cell output voltage and reversible potential, respectively. According to the Nernst equation, E0 can be calculated as:

[0046]

[0047] Where T is the operating temperature, R is the gas constant, and n e Where H₂ has 2 electrons per molecule, and F is Faraday's constant. This refers to the hydrogen partial pressure in the anode channel. and These are the oxygen partial pressure and water vapor partial pressure in the cathode flow channel, respectively.

[0048] and Affected by temperature, It can be calculated as:

[0049]

[0050]

[0051]

[0052] in, and The saturated vapor pressures P and P' are the anode and cathode, respectively. an and P ca T represents the total pressure in the anode and cathode channels, respectively. fc The temperature of the fuel cell stack, and This refers to the molar concentrations of oxygen and nitrogen. It can be obtained by subtracting the oxygen consumption in the pipeline from the molar concentration of imported oxygen.

[0053] The total pressure within the anode and cathode channels of the j-th single cell is calculated using the following formula:

[0054]

[0055]

[0056] P an,j and P ca,j These are the total voltages on the anode and cathode sides of the j-th single cell, respectively, where N is the number of single cells, and P is the total voltage. an,inlet It is the pressure collected by the hydrogen inlet pressure sensor, P an,outlet This is the pressure collected by the hydrogen pressure sensor. Similarly, P ca,inlet and P ca,outlet It is also obtained through sensors.

[0057] The Nernst equation mathematically explains the degradation characteristics of the three overpotentials, among which ΔU act , ΔU ohm and ΔU con These are the increased activation overpotential, ohmic overpotential, and concentration overpotential. In reality, the degradation characteristics of these three overpotentials are quite different. Activation polarization consists of cathodic and anodic activation polarization, with cathodic polarization accounting for the largest proportion of activation polarization.

[0058] ΔU act =η HOR +η ORR (8)

[0059]

[0060]

[0061] Where, η HOR and η ORR These represent the activation polarization losses at the anode and cathode, respectively, α an and α ca , where are the anode and cathode transfer coefficients, respectively, and i is the current density. o,an and i o,ca These are the local specific exchange current densities at the anode and cathode, respectively, and are dominated by the cell's operating temperature and gas partial pressure.

[0062]

[0063]

[0064] and These are the reference exchange current densities for the anode and cathode, respectively. A Pt,an and A Pt,CA These are the anode and cathode catalytic regions, respectively. L Pt,an and L Pt,ca These represent the catalyst loadings at the anode and cathode, respectively. and These are the reference pressures for hydrogen and oxygen, respectively. and These are the pressure dependence coefficients for hydrogen and oxygen, respectively. E an and E ca These are the activation energies for hydroxide oxidation and oxygen reduction, respectively. R ref This is a reference temperature.

[0065] For ohmic overpotential, the voltage drop is linearly related to the output current.

[0066] ΔU ohm =i×R Ω (13)

[0067] Among them, R Ω It is an ohmic resistor, which can be calculated using high-frequency impedance values. However, for concentration overpotentials, the voltage drop is more complex because its rate of increase becomes increasingly higher with increasing output current.

[0068] ΔU con =E0-ΔU act -ΔU ohm -E cell (14)

[0069] The concentration loss of the two half-cells can then be calculated:

[0070] ΔU con_inlet = E0 - ΔU act -ΔU ohm -V inlet (15)

[0071] ΔU con_outlet = E0 - ΔU act -ΔU ohm -V outlet (16)

[0072] Furthermore, in step 5, based on the concentration difference losses of the two half-cells calculated in step 2, calculate the performance evaluation factor k of the single cell.

[0073]

[0074] The value of k follows the following relationship: if k ≤ -1, k = -1; if -1 < k < 1, k = 0; if 1 < k, k = 1. n is a coefficient, taking values from 0.3 to 0.5.

[0075] In step 2, calculate the average voltage of the fuel cell anode inlet and anode outlet through the following formula , and the root mean square average value σ of the fuel cell anode inlet and anode outlet voltages V ,

[0076]

[0077]

[0078]

[0079] N is the number of single cells, V inlet,j is the anode inlet voltage of the jth single cell, V outlet,j is the anode outlet voltage of the jth single cell, is the average anode inlet voltage of the fuel cell, is the average anode outlet voltage of the fuel cell.

[0080]

[0081]

[0082]

[0083] Among them, σ V,inlet is the root mean square of the fuel cell anode inlet voltage, σ V,outlet is the root mean square of the fuel cell anode outlet voltage.

[0084] Furthermore, the formula for calculating the stack condition assessment factor in step 3 is as follows:

[0085]

[0086]

[0087]

[0088]

[0089]

[0090]

[0091] Furthermore, the four fault levels of the fuel cell stack identified in step 4 are as follows:

[0092] When the average voltage of the anode inlet and anode outlet of all individual cells is between K 1_up and K 1_down During this period, the stack fault level is State 1.

[0093]

[0094] When the average voltage at the anode inlet and anode outlet of a single cell (assuming it is the j-th cell) is between K 2_up and K 2_down Between, and beyond [K 1_down K 1_up When the range is within 1, the stack fault level is State 2.

[0095]

[0096] When the average voltage at the anode inlet and anode outlet of a single cell (assuming it is the j-th cell) is between K 3_up and K 3_down Between, and beyond [K 2_down K 2_up When the range is within 3, the stack fault level is state 3.

[0097]

[0098] When the average voltage at the anode inlet and anode outlet of a single cell (assuming the j-th cell) exceeds [K] 3_down K 3_up When the range is within ], it is state 4.

[0099]

[0100] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for hydrogen removal from an anode of a fuel cell based on multipoint voltage, characterized in that, The steps of the method are as follows: S1, obtaining the voltage at the anode inlet and the anode outlet of each single cell during the operation of the fuel cell; S2, calculating the average value and the root mean square value of the voltage at the anode inlet and the anode outlet of the fuel cell; regarding each single cell as a half cell with two gas circuits in series and two electric circuits in parallel, and calculating the activation voltage loss, the ohmic loss and the concentration difference loss of the two half cells respectively; S3, further calculating the stack state evaluation factor based on the average value and the root mean square value of the voltage calculated in step S2; the calculation formula of the stack state evaluation factor is: ； wherein V is the average value of the voltage at the fuel cell anode inlet and anode outlet, V is the root mean square average value of the voltage at the fuel cell anode inlet and anode outlet; S4, dividing the stack failure level into four levels based on the stack state evaluation factor calculated in step S3; S5, performing different treatments according to different stack failure levels; when the stack is in state 1, the hydrogen inlet electromagnetic valve, the circulating pump and the hydrogen exhaust valve maintain the working state of the previous moment; when the stack is in state 2, the hydrogen inlet electromagnetic valve and the circulating pump maintain the working state of the previous moment, and the opening frequency of the hydrogen exhaust valve is increased by A%; when the stack is in state 3, the performance evaluation factor k of the single cell is calculated based on the activation voltage loss, the ohmic loss and the concentration difference loss of the two half cells calculated in step S2; the performance evaluation factor k of the single cell is calculated by the following formula: The value of k follows the following relationship: if k≤-1, then k=-1; if-1<k<1, then k=0; if 1<k, then k=1, wherein , V1and V2are the voltages at the anode inlet and outlet of the single cell, respectively, , J1and J2are the concentration losses of the two half cells, respectively, is a coefficient, taken between 0.3 and 0.

5. If k=-1 or k=0, the opening degree of the hydrogen inlet electromagnetic valve is increased by B%, the rotating speed of the circulating pump is reduced by C%, and the opening frequency of the hydrogen exhaust valve is increased by D%; if k=1, an alarm is given; when the stack is in state 4, the performance evaluation factor k of the single cell is calculated based on the activation voltage loss, the ohmic loss and the concentration difference loss of the two half cells calculated in step S2; if k=-1 or k=0, the opening degree of the hydrogen inlet electromagnetic valve is increased by B%, the rotating speed of the circulating pump is reduced by C%, and the opening frequency of the hydrogen exhaust valve is increased by D%; if k=1, an alarm is given.

2. The multi-point voltage based fuel cell anode hydrogen removal method of claim 1, wherein: The stack failure level in step S4 is divided into state 1, state 2, state 3 and state 4, when the average voltage of the anode inlet and the anode outlet of all single cells is between and , the stack failure level is state 1; when the average voltage of the anode inlet and the anode outlet of some single cells is between and , and beyond the range of , , the stack failure level is state 2; when the average voltage of the anode inlet and the anode outlet of some single cells is between and , and beyond the range of , , the stack failure level is state 3; when the average voltage of the anode inlet and the anode outlet of some single cells is beyond the range of , , the stack failure level is state 4.

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