CN115411305B - Equivalent circuit model for fuel cell starting process - Google Patents

Equivalent circuit model for fuel cell starting process Download PDF

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CN115411305B
CN115411305B CN202211137310.9A CN202211137310A CN115411305B CN 115411305 B CN115411305 B CN 115411305B CN 202211137310 A CN202211137310 A CN 202211137310A CN 115411305 B CN115411305 B CN 115411305B
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cathode
fuel cell
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leakage
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CN115411305A (en
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万鑫铭
邓波
高艳
毛占鑫
鲍欢欢
汤浩
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Caic New Energy Technology Co ltd
China Automotive Engineering Research Institute Co Ltd
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China Automotive Engineering Research Institute Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
    • H01M8/04225—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells during start-up
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
    • H01M8/04302—Processes for controlling fuel cells or fuel cell systems applied during specific periods applied during start-up
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04305—Modeling, demonstration models of fuel cells, e.g. for training purposes
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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    • Y02E60/50—Fuel cells

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Abstract

The invention relates to the technical field of fuel cells, and discloses an equivalent circuit model for a starting process of a fuel cell, which comprises the following steps: the equivalent hydrogen flow passage is divided into a plurality of subareas, the subareas are connected in parallel through transverse resistors, each subarea corresponds to an equivalent circuit model basic circuit, the equivalent circuit model basic circuit comprises a linear voltage source, and the linear voltage source is used for representing potential difference generated when a hydrogen interface reaches an anode hydrogen flow passage and reacts with oxygen in the starting process of the electric pile. According to the invention, the electrical behavior of the hydrogen flow channel in the electric pile is taken as the basis for establishing a circuit structure, the internal electrical macroscopic behavior in the starting process of the electric pile can be accurately described through the equivalent circuit model, the test times required by the actual experiment of the electric pile are reduced, and the influence of the experiment on the service life attenuation of the electric pile is reduced.

Description

Equivalent circuit model for fuel cell starting process
Technical Field
The invention relates to the technical field of fuel cells, in particular to an equivalent circuit model of a fuel cell starting process.
Background
In the past few decades, with further development of industrialization, internal combustion engines have been widely used as power sources for land vehicles, commercial ships and stationary power plants, but the large use of fossil fuels poses a series of environmental problems and energy crisis. Researchers around the world are continually striving to develop new clean energy sources to replace traditional fossil energy sources and solve the energy crisis and environmental pollution problems. Among them, proton Exchange Membrane Fuel Cells (PEMFCs) are considered as the most promising solution in new energy automobile applications due to their low pollution, high power density, high efficiency, and the like.
In order to research the dynamic characteristics, attenuation mechanisms and performance degradation influencing factors of the fuel cell in the starting process, an acceleration experiment mode is mostly adopted at present, namely, frequent start-stop experiments are carried out on the fuel cell stack under different operating conditions in a laboratory. However, frequent start-up or shut-down tests can have an irreversible damaging effect on the stack, especially for certain extreme conditions, which can greatly affect the life of the stack. In order to avoid the problems, the research on the macroscopic behavior of the fuel cell by using an equivalent circuit model has important guiding significance in the stage of pile development and test.
Disclosure of Invention
The invention aims to provide an equivalent circuit model in the starting process of a fuel cell, and the equivalent circuit model is used for accurately describing the internal electric macroscopic behavior in the starting process of the fuel cell by taking the electric behavior of a hydrogen flow channel in the fuel cell as the basis for establishing a circuit structure, so that the test times required by the actual test of the fuel cell are reduced, and the influence of the test on the service life attenuation of the fuel cell is reduced.
The technical scheme provided by the invention is as follows: an equivalent circuit model of a fuel cell start-up procedure, comprising: the equivalent hydrogen flow passage is divided into a plurality of subareas, the subareas are connected in parallel through transverse resistors, each subarea corresponds to an equivalent circuit model basic circuit, the equivalent circuit model basic circuit comprises a linear voltage source, and the linear voltage source is used for representing potential difference generated when a hydrogen interface reaches an anode hydrogen flow passage and reacts with oxygen in the starting process of the electric pile.
The working principle and the advantages of the invention are as follows: the equivalent circuit model of the fuel cell starting process simulates an anode hydrogen flow passage in a fuel cell stack, and the anode hydrogen flow passage can generate transverse resistance when contacting with a gas diffusion layer due to the fact that ridges and grooves exist in the flow passage caused by uneven design of the anode hydrogen flow passage of the fuel cell stack, and the influence of the transverse resistance is reflected not only between adjacent partitions along the hydrogen flow passage, but also between the adjacent partitions in space. Therefore, the equivalent hydrogen flow passage is divided into a plurality of subareas, the subareas are connected in parallel through transverse resistors, each subarea corresponds to an equivalent circuit model basic circuit, the equivalent circuit model basic circuit comprises a linear voltage source, and the linear voltage source is used for representing potential difference generated by the reaction of the hydrogen interface reaching the anode hydrogen flow passage and oxygen in the starting process of the electric pile. The equivalent circuit model of the fuel cell starting process provided by the invention takes the electrical behavior of the hydrogen flow channel in the electric pile as the basis for establishing a circuit structure, and can accurately describe the internal electrical macroscopic behavior in the electric pile starting process, reduce the test times required by the electric pile actual experiment and reduce the influence of the experiment on the service life attenuation of the electric pile. The equivalent circuit model has universality and extensibility, and can be matched with fuel cell stacks of different specifications by changing electrical parameters without modifying the model structure in a large amount.
Further, the equivalent circuit model basic circuit comprises a cathode loop, a public circuit and an anode loop which are sequentially connected in series, wherein the cathode loop is used for representing an electrochemical reaction process of a cathode side of a galvanic pile, the anode loop is used for representing an electrochemical reaction process of an anode side of the galvanic pile, the public circuit is used for representing an electrochemical reaction process on a galvanic pile membrane electrode assembly, and the linear voltage source is connected in series in the public circuit.
The cathode loop, the public circuit and the anode loop respectively represent the electrochemical reaction process of the cathode side of the electric pile, the electrochemical reaction process of the anode side of the electric pile and the electrochemical reaction process on the membrane electrode assembly of the electric pile. The electrochemical reaction process of the two poles of the galvanic pile can be more accurately simulated.
Further, the cathode loop comprises a cathode capacitance layer, a cathode charge transfer circuit and a cathode leakage circuit which are sequentially connected in parallel, and the anode loop comprises an anode capacitance layer, an anode charge transfer circuit and an anode leakage circuit which are sequentially connected in parallel;
the cathode capacitance layer and the anode capacitance layer are used for representing double capacitance layers in the pile;
the cathode charge transfer circuit and the anode charge transfer circuit are used for representing the conduction paths of the transfer of ions and electrons in the electric pile and the resistance of the electrode surface to the charge transfer process;
the cathode leakage circuit is used for representing the oxidation-reduction reaction of the platinum carrier of the cathode catalyst layer and the corrosion reaction of the carbon carrier in the starting process of the fuel cell, and the anode leakage circuit is used for representing the oxidation-reduction reaction and other oxidation-reduction reactions of the platinum carrier of the anode catalyst layer in the starting process of the fuel cell;
the common circuit is used for representing dynamic influences of the internal resistance change of the galvanic pile film, the temperature and the water content in the galvanic pile on the internal electric behavior of the fuel cell.
Internal charge transfer and diffusion movement can occur in the starting process of the fuel cell, the electric behavior of the internal charge is assumed to be double-layer capacitance according to the transfer and diffusion of the charge on the electrode, the polarization area of the internal space charge of the electric pile is represented, and the double-layer capacitance of the electric pile is represented through the cathode capacitance layer and the anode capacitance layer. The charge transfer process occurring in the catalyst layer is affected by the mass transport of hydrogen and oxygen molecules in the pores of the catalyst layer (coacervation diffusion) and mass transport in the Nafion thin layer around the catalyst particles (thin film diffusion). On the other hand, the charge transfer process is also affected by the interaction between the rate of hydrogen and oxygen intake and temperature, and the conduction paths for the transfer of ions and electrons inside the stack and the resistance of the electrode surface to the charge transfer process are represented by the cathodic charge transfer circuit and the anodic charge transfer circuit. In the starting process of the fuel cell, oxidation-reduction reaction can occur on the platinum carrier of the cathode catalyst layer, meanwhile, high potential can be generated on the anode side due to the formation of a hydrogen empty interface in a reaction gas flow channel in the starting process, so that corrosion reaction of the cathode carbon carrier is generated, leakage current is generated, the oxidation-reduction reaction of the platinum carrier of the cathode catalyst layer and the corrosion reaction of the carbon carrier in the starting process of the fuel cell are represented by a cathode leakage circuit, and the oxidation-reduction reaction and other oxidation-reduction reactions of the platinum carrier of the anode catalyst layer in the starting process of the fuel cell are represented by an anode leakage circuit.
Further, the cathode charge transfer circuit comprises a cathode charge transfer resistor, a cathode oxygen reduction reaction inductor and a first diode which are sequentially connected in series, and the cathode leakage circuit comprises a cathode leakage resistor, a cathode leakage inductor and a second diode which are sequentially connected in series;
the anode charge transfer circuit comprises an anode charge transfer resistor, an anode hydrogen oxidation reaction inductor and a third diode which are sequentially connected in series, and the anode leakage circuit comprises an anode leakage resistor, an anode leakage inductor and a fourth diode which are sequentially connected in series;
the common circuit comprises a high-frequency resistor, a high-frequency inductor and a linear voltage source which are sequentially connected in series.
In order to electrified the charge transfer behavior of the fuel cell in the starting process, a circuit design mode that a fixed-value resistor is connected with an inductor in series is adopted, the cathode charge transfer resistor and the anode transfer resistor represent the inherent influence of catalyst materials and electrode materials on the charge transfer process, and the cathode oxygen reduction reaction inductor and the anode hydrogen oxidation reaction inductor represent the dynamic influence of the inlet flow, temperature and humidity of reaction gas on the internal electric behavior of the electric pile in the starting process. The cathode leakage resistor and the anode leakage resistor are arranged, and simultaneously a cathode leakage inductance Lc and an anode leakage inductance La are respectively connected in series with the cathode leakage resistor and the anode leakage resistor, and are used for representing the dynamic contribution of oxidation-reduction reaction of a catalyst layer platinum carrier and corrosion reaction of a carbon carrier to internal current distribution in the starting process of the fuel cell, a second diode and a fourth diode are used for controlling the direction of internal current, and the current flowing through a cathode leakage resistor loop is negative current. The high-frequency resistor characterizes the internal resistance of a galvanic pile film, the electrolyte resistance and the contact resistance, the contact resistance is related to the assembly pressure during assembly of the galvanic pile, the assembly pressure of the galvanic pile directly influences the structure of a galvanic pile graphite plate and a porous fiber material, such as the contact pressure between a gas diffusion layer and a catalyst layer interface, so that the size of the contact resistance is influenced, and the distribution condition of the contact resistance has great influence on internal current distribution.
Further, the cathode leakage resistance and the anode leakage resistance are constant values.
Since the internal current generated by the oxidation-reduction reaction of the platinum support and the corrosion reaction of the carbon support of the catalyst layer is highly nonlinear, the resistance values of the cathode leakage resistance and the anode leakage resistance are set in the invention.
Further, the voltage rising time of the linear voltage source E is trise, and the delay time of the hydrogen interface reaching the adjacent partition is tdelay;
in the equivalent hydrogen flow channel, for the nth partition, when the hydrogen interface does not reach the partition yet, the value of E is 0; when the hydrogen interface reaches this zone, which is activated immediately, E rises linearly from 0 to 1V in the trie time, E has the expression:
Figure BDA0003851929130000041
wherein tdelayi is the delay time for the hydrogen interface to reach the ith partition from the ith-1 th partition,
Figure BDA0003851929130000042
the time required for the hydrogen interface to reach the ith partition from the flow channel inlet of the equivalent hydrogen flow channel.
Through the mathematical expression of the linear voltage source E and the combination of an equivalent circuit model, real-time data of the linear voltage source can be calculated, and subsequent simulation is facilitated.
Further, the number of partitions is a multiple of 8.
According to the specific structure of the anode hydrogen flow channel of the fuel cell stack, the simulated equivalent hydrogen flow channel is divided, and when the number of divided partitions is a multiple of 8, the potential difference of each partition can be expressed better, so that the subsequent simulation calculation of an equivalent circuit model is facilitated.
Further, the number of the equivalent hydrogen flow channels is equal to that of the fuel cell basic units of the fuel cell stack, and the equivalent hydrogen flow channels are connected in series end to end through bipolar plate resistors.
The equivalent circuit model is expanded from a fuel cell basic unit of the fuel cell stack to an equivalent circuit model of the whole stack, and the equivalent circuits of the fuel cell basic units are connected in series through bipolar plate resistors according to the assembly sequence of the stack, so that the dynamic performance of the whole stack in the starting process can be studied.
Drawings
FIG. 1 is a circuit diagram of an equivalent circuit model basic circuit according to a first embodiment of the present invention;
fig. 2 is a schematic structural view of a fuel cell stack according to a first embodiment of the present invention;
fig. 3 is a schematic structural view of an anode plate of a fuel cell basic unit of a fuel cell stack according to the first embodiment of the present invention;
FIG. 4 is a circuit diagram of an equivalent hydrogen flow path of an equivalent circuit model according to the first embodiment of the present invention;
FIG. 5 is a graph showing simulation results of current density inside 8 partitions of an equivalent circuit model according to the first embodiment of the present invention when the hydrogen flow rate is 6.6 SLPM;
FIG. 6 is a diagram showing the simulation result of the node voltage of the equivalent circuit model according to the first embodiment of the present invention when the hydrogen flow is 6.6 SLPM;
FIG. 7 is a graph showing simulation results of current density inside 8 partitions of an equivalent circuit model according to the first embodiment of the present invention when the hydrogen flow rate is 13.2 SLPM;
FIG. 8 is a diagram showing the simulation result of the node voltage of the equivalent circuit model according to the first embodiment of the present invention when the hydrogen flow is 13.2 SLPM;
FIG. 9 is a graph showing simulation results of current density inside 8 partitions of an equivalent circuit model according to the first embodiment of the present invention when the hydrogen flow rate is 19.8 SLPM;
FIG. 10 is a diagram showing the simulation result of the node voltage of the equivalent circuit model according to the first embodiment of the present invention when the hydrogen flow rate is 19.8 SLPM;
FIG. 11 is a graph showing the current density of partition 1 at start-up under ambient conditions of normal temperature and humidity, water content, in accordance with the first embodiment of the present invention;
FIG. 12 is a graph showing the internal current density of the partition 1 when the temperature, humidity and water content decrease to increase the high frequency inductance L0 in the common circuit according to the first embodiment of the present invention;
FIG. 13 is a graph showing the internal current density of the partition 1 when the temperature and humidity and the water content increase to decrease the high frequency inductance L0 in the common circuit according to the first embodiment of the present invention;
fig. 14 is a diagram of an equivalent hydrogen flow path series circuit according to a second embodiment of the present invention.
Detailed Description
Embodiments of the technical scheme of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present invention, and thus are merely examples, and are not intended to limit the scope of the present invention.
It is noted that unless otherwise indicated, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.
The following is a further detailed description of the embodiments:
the labels in the drawings of this specification include: the cathode loop 1, the anode loop 2, the public circuit 3, the cathode end plate A-1, the fuel cell basic unit A-2, the high-resolution partition current collecting device A-3, the anode end plate A-4, the fixed screw A-5, the hydrogen inlet B-1, the cooling liquid outlet B-2, the air outlet B-3, the hydrogen outlet B-4, the cooling liquid inlet B-5, the air inlet B-6, the anode hydrogen flow passage C-1, the cathode capacitance layer C1, the anode capacitance layer C2, the cathode charge transfer resistor Rctc, the cathode oxygen reduction reaction inductance LORR, the first diode D1, the cathode leakage resistor Rlkc, the cathode leakage inductance Lc, the second diode D2, the anode charge transfer resistor Rcta, the anode hydrogen oxidation reaction inductance LHOR, the third diode D3, the anode leakage resistor Rlka, the anode leakage inductance, the fourth diode D4, the high-frequency resistance La, the high-frequency inductance L0 and the linear voltage source E.
Embodiment one:
as shown in fig. 2, the fuel cell stack in the experiment of this embodiment includes a cathode end plate a-1, a fuel cell base unit a-2, a high resolution zoned current collecting device a-3, and an anode end plate a-4, which are connected in this order, and fixed by a fixing screw a-5. The high-resolution zoned current acquisition device A-3 is used for acquiring the internal current distribution of the fuel cell basic unit A-2 at the anode end of the electric pile.
As shown in FIG. 3, the anode plate of the fuel cell basic unit A-2 of the fuel cell stack comprises a hydrogen inlet B-1, a cooling liquid outlet B-2, an air outlet B-3, a hydrogen outlet B-4, a cooling liquid inlet B-5, an air inlet B-6 and an anode hydrogen flow passage C-1, wherein the anode hydrogen flow passage C-1 is respectively communicated with the hydrogen inlet B-1 and the hydrogen outlet B-4.
As shown in fig. 4, the equivalent circuit model of the fuel cell starting process of the present invention includes an equivalent hydrogen flow path for simulating the anode hydrogen flow path C-1. The equivalent hydrogen flow passage is divided into 8 subareas, the subareas are connected in parallel through transverse resistors, each subarea corresponds to an equivalent circuit model basic circuit, the equivalent circuit model basic circuit comprises a linear voltage source E, and the linear voltage source E is used for representing potential difference generated by the reaction of the hydrogen interface reaching the anode hydrogen flow passage C-1 and oxygen in the starting process of the galvanic pile.
Rt1-Rt16 are the lateral resistances between the segments, and the lateral resistances are generated when the anode hydrogen flow channel C-1 contacts with the gas diffusion layer due to the ridges and grooves in the flow channel caused by the uneven design of the anode hydrogen flow channel C-1 of the fuel cell stack, so that the influence of the lateral resistances is not only reflected in the adjacent segments along the hydrogen flow channel, but also exists between the adjacent segments in space. Each equivalent circuit model basic circuit structure is provided with a linear voltage source E which is used for representing potential difference generated by the reaction of hydrogen interface reaching the anode hydrogen flow channel C-1 and oxygen in the starting process of the galvanic pile. In this embodiment, the voltage rise time of the linear voltage source E is defined as trise, and there is a delay time between the hydrogen interface reaching the adjacent partition, and this time difference is defined as tdelay.
As shown in fig. 1, the equivalent circuit model basic circuit includes a cathode circuit 1, a common circuit 3, and an anode circuit 2, which are sequentially connected in series. The cathode loop 1 is used to represent the electrochemical reaction process on the cathode side of the stack, the anode loop 2 is used to represent the electrochemical reaction process on the anode side of the stack, the common circuit 3 is used to represent the electrochemical reaction process on the membrane electrode assembly of the stack, and the linear voltage source E is connected in series in the common circuit 3.
The cathode loop 1 comprises a cathode capacitance layer C1, a cathode charge transfer circuit and a cathode leakage circuit which are sequentially connected in parallel, and the anode loop 2 comprises an anode capacitance layer C2, an anode charge transfer circuit and an anode leakage circuit which are sequentially connected in parallel.
The cathode charge transfer circuit comprises a cathode charge transfer resistor Rctc, a cathode oxygen reduction reaction inductor lorerrlkc and a first diode D1 which are sequentially connected in series, and the cathode leakage circuit comprises a cathode leakage resistor Rlkc, a cathode leakage inductor Lc and a second diode D2 which are sequentially connected in series.
The anode charge transfer circuit includes an anode charge transfer resistor Rcta, an anode hydroxide reaction inductance LHOR, and a third diode D3, which are sequentially connected in series, and the anode leakage circuit includes an anode leakage resistor Rlka, an anode leakage inductance La, and a fourth diode D4, which are sequentially connected in series.
The common circuit 3 includes a high-frequency resistor Rm, a high-frequency inductance L0, and a linear voltage source E, which are sequentially connected in series.
Internal charge transfer and diffusion movements occur during the start-up of the fuel cell, and the electrical behavior of the internal charge is assumed to be a double-layer capacitance according to the transfer and diffusion of the charge on the electrode, representing the polarized region of the internal space charge of the stack. The cathode capacitance layer C1 and the anode capacitance layer C2 together form a dual-capacitance layer inside the fuel cell, which is used for representing the dual-capacitance layer inside the electric pile. The values of the cathode capacitance layer C1 and the anode capacitance layer C2 are related to the membrane electrode assembly, the electrode carbon support roughness, the catalyst layer thickness, and the catalyst layer platinum support geometry of the fuel cell stack.
The charge transfer process occurring in the catalyst layer is affected by the mass transport of hydrogen and oxygen molecules in the pores of the catalyst layer (coacervation diffusion) and mass transport in the Nafion thin layer around the catalyst particles (thin film diffusion). On the other hand, the charge transfer process is also affected by the interaction between the rate of hydrogen and oxygen intake and temperature. In order to electrified the charge transfer behavior of the fuel cell in the starting process, a circuit design mode that a constant resistor is connected in series with an inductor is adopted, wherein the constant resistor is a cathode charge transfer resistor Rctc and an anode charge transfer resistor Rcta, and the inductor is a cathode oxygen reduction reaction inductor LORR for representing the cathode oxygen reduction reaction process and an anode hydrogen oxidation reaction inductor LHOR for representing the anode hydrogen oxidation reaction process. The charge transfer resistances Rctc and Rcta represent the inherent influence of the catalyst material and the electrode material on the charge transfer process, and the inductances lor and LHOR represent the dynamic influence of the inlet gas flow, temperature and humidity of the reaction gas on the internal electric behavior of the galvanic pile in the starting process. The cathode charge transfer resistor Rctc is connected in series with the cathode oxygen reduction reaction inductor lor and the first diode D1 and is used for representing the conduction path of ionic and electronic transfer inside the galvanic pile and the resistance of the electrode surface to the charge transfer process. The anode charge transfer resistor Rcta is connected in series with the anode hydroxide reaction inductance LHOR and the third diode D3 and is used for representing the conduction path of the transfer of ions and electrons in the galvanic pile and the resistance of the electrode surface to the charge transfer process.
In the starting process of the fuel cell, oxidation-reduction reaction can occur on the platinum carrier of the cathode catalyst layer, and meanwhile, high potential can be generated on the anode side due to the formation of a hydrogen air interface in the reaction gas flow channel in the starting process, so that corrosion reaction of the cathode carbon carrier is caused, and leakage current is generated. In the equivalent circuit model of the fuel cell starting process, a cathode leakage resistance Rlkc and an anode leakage resistance Rlka are set. In the starting process of the fuel cell, since the internal current generated by the oxidation-reduction reaction of the platinum carrier and the corrosion reaction of the carbon carrier of the catalyst layer is highly nonlinear, in this embodiment, the resistance values of the cathode leakage resistance Rlkc and the anode leakage resistance Rlka are taken as constant values, and meanwhile, a cathode leakage inductance Lc and an anode leakage inductance La are respectively connected in series with the Rlkc and the Rlka, so as to represent the dynamic contribution of the oxidation-reduction reaction of the platinum carrier of the catalyst layer and the corrosion reaction of the carbon carrier to the internal current distribution in the starting process of the fuel cell. The cathode leakage resistance Rlkc is connected in series with the cathode leakage inductance Lc and the second diode D2 to represent the oxidation-reduction reaction of the cathode catalyst layer platinum support and the corrosion reaction of the carbon support during the start-up of the fuel cell. The anode leakage resistance Rlka is connected in series with the anode leakage inductance La and the fourth diode D4, and is used for representing the oxidation-reduction reaction and other oxidation-reduction reactions of the platinum carrier of the anode catalyst layer during the starting process of the fuel cell. The second diode D2 and the fourth diode D4 are used for controlling the direction of the internal current, and the current flowing through the positive-negative leakage resistor Rlka loop is negative.
In the common circuit 3, the high-frequency resistance Rm is used for representing the membrane internal resistance, the electrolyte resistance and the contact resistance of the galvanic pile, the contact resistance is related to the assembly pressure during the assembly of the galvanic pile, the assembly pressure of the galvanic pile directly influences the structure of the galvanic pile graphite plate and the porous fiber material, such as the contact pressure between the interface of the gas diffusion layer and the catalyst layer, thereby influencing the size of the contact resistance, and the distribution condition of the contact resistance has a great influence on the internal current distribution. It is assumed that the resistance values of the internal resistances of the films at the respective positions inside the stack are equal. The high-frequency resistor Rm is connected with the high-frequency inductor L0 in series and is used for representing dynamic influence of the internal resistance change of the galvanic pile film, the temperature and the water content in the galvanic pile on the internal electric behavior of the fuel cell.
In the basic circuit of the equivalent circuit model, E is a voltage source of each partition, and represents the potential difference generated by the reaction of the hydrogen interface reaching the anode hydrogen flow channel C-1 and oxygen in the starting process of the galvanic pile. The voltage source E is assumed to rise linearly to 1V with a rise time of trise, which is the time required for the internal current of each partition unit to rise from 0 to the forward peak during start-up of the fuel cell.
The voltage rising time of the linear voltage source E is trise, and the delay time of the hydrogen interface reaching the adjacent partition is tdelay; in the equivalent hydrogen flow channel, for the nth partition, when the hydrogen interface does not reach the partition yet, the value of E is 0; when the hydrogen interface reaches this zone, which is activated immediately, E rises linearly from 0 to 1V in the trie time, E has the expression:
Figure BDA0003851929130000091
wherein tdelayi is the delay time for the hydrogen interface to reach the ith partition from the ith-1 th partition,
Figure BDA0003851929130000092
the time required for the hydrogen interface to reach the ith partition from the flow channel inlet of the equivalent hydrogen flow channel.
Fig. 5 to 10 are graphs showing the internal current density change and the voltage change of the equivalent circuit model of the present embodiment at different starting hydrogen flow rates. Wherein, fig. 5 is a diagram of simulation results of current density inside 8 partitions of the equivalent circuit model when the hydrogen flow is 6.6 SLPM; FIG. 6 is a graph of the simulation result of the node voltage of the equivalent circuit model when the hydrogen flow is 6.6 SLPM; FIG. 7 is a graph of simulation results of the current density inside 8 zones of the equivalent circuit model at a hydrogen flow rate of 13.2 SLPM; FIG. 8 is a graph of the simulation result of the node voltage of the equivalent circuit model when the hydrogen flow is 13.2 SLPM; FIG. 9 is a simulation result of the current density inside 8 partitions of the equivalent circuit model at a hydrogen flow rate of 19.8 SLPM; fig. 10 is a voltage-saving simulation result of the equivalent circuit model at a hydrogen flow rate of 19.8 SLPM. The internal current, the antipole corrosion current and the electricity-saving voltage under different starting hydrogen flow rates can be quantitatively researched by modifying the boundary condition voltage rising time trise and the inter-partition delay time tdelay, and the method has reference significance for hydrogen flow rate setting during actual stack starting.
Fig. 11-13 are plots of the current density change for zone 1 at different membrane internal resistances for the same hydrogen flow rate. FIG. 11 is a plot of current density for partition 1 at start-up under ambient conditions of normal temperature, humidity, water content, with a positive current peak of about 0.078A/cm2; FIG. 12 is a graph showing the internal current density of partition 1 when the temperature and humidity and water content decrease to increase the high frequency inductance L0 in the common circuit 3, the positive peak of the current density of partition 1 decreases by about-0.071A/cm 2; FIG. 13 is a graph showing the internal current density of the partition 1 when the temperature and humidity and the water content increase to decrease the high frequency inductance L0 in the common circuit 3, and the positive peak value of the current density of the partition 1 increases by about-0.081A/cm 2. The implementation results shown in fig. 11-13 prove that the equivalent circuit model of the fuel cell starting process described in this embodiment can respond positively to the influence of the changes of the temperature and humidity, the water content and the environmental conditions in the fuel cell on the starting performance of the electric pile.
Embodiment two:
as shown in fig. 14, in the equivalent hydrogen flow path series circuit diagram, the equivalent circuit model of the second embodiment is expanded from a fuel cell basic unit a-2 of the fuel cell stack to an equivalent circuit model of the whole stack. The equivalent hydrogen flow channels are equal to the fuel cell basic units A-2 of the fuel cell stack in number, and are connected in series end to end through bipolar plate resistors. Each fuel cell basic unit A-2 is formed by connecting 8 equivalent circuit model basic circuit units in parallel through a transverse resistor Rt, and for the whole electric pile, the equivalent circuits of the fuel cell basic units A-2 are connected in series through a bipolar plate resistor Rp (n) according to the electric pile assembly sequence, wherein n is the nth fuel cell basic unit A-2. Through the equivalent circuit model, the dynamic performance of the whole pile in the starting process can be researched, and the control strategy design and the pile design during the whole pile starting have important reference significance.
The foregoing is merely exemplary of the present invention, and the specific structures and features that are well known in the art are not described in any way herein, so that those skilled in the art will be aware of all the prior art to which the present invention pertains, and will be able to ascertain all of the prior art in this field, and with the ability to apply the conventional experimental means prior to this date, without the benefit of the present application, with the ability to complete and practice the present invention, without the ability of some typical known structures or methods to become an obstacle to the practice of the present application by those of ordinary skill in the art. It should be noted that modifications and improvements can be made by those skilled in the art without departing from the structure of the present invention, and these should also be considered as the scope of the present invention, which does not affect the effect of the implementation of the present invention and the utility of the patent. The protection scope of the present application shall be subject to the content of the claims, and the description of the specific embodiments and the like in the specification can be used for explaining the content of the claims.

Claims (5)

1. An equivalent circuit model of a fuel cell starting process, comprising: the equivalent hydrogen flow passage is divided into a plurality of subareas, the subareas are connected in parallel through transverse resistors, each subarea corresponds to an equivalent circuit model basic circuit, the equivalent circuit model basic circuit comprises a linear voltage source, and the linear voltage source is used for representing potential difference generated by the reaction of the hydrogen interface reaching the anode hydrogen flow passage and oxygen in the starting process of the galvanic pile;
the equivalent circuit model basic circuit comprises a cathode loop, a public circuit and an anode loop which are sequentially connected in series, wherein the cathode loop is used for representing an electrochemical reaction process of a cathode side of a galvanic pile, the anode loop is used for representing an electrochemical reaction process of an anode side of the galvanic pile, the public circuit is used for representing an electrochemical reaction process on a galvanic pile membrane electrode assembly, and the linear voltage source is connected in series in the public circuit;
the cathode loop comprises a cathode capacitance layer, a cathode charge transfer circuit and a cathode leakage circuit which are sequentially connected in parallel, and the anode loop comprises an anode capacitance layer, an anode charge transfer circuit and an anode leakage circuit which are sequentially connected in parallel;
the cathode capacitance layer and the anode capacitance layer are used for representing double capacitance layers in the pile;
the cathode charge transfer circuit and the anode charge transfer circuit are used for representing the conduction paths of the transfer of ions and electrons in the electric pile and the resistance of the electrode surface to the charge transfer process;
the cathode leakage circuit is used for representing the oxidation-reduction reaction of the platinum carrier of the cathode catalyst layer and the corrosion reaction of the carbon carrier in the starting process of the fuel cell, and the anode leakage circuit is used for representing the oxidation-reduction reaction and other oxidation-reduction reactions of the platinum carrier of the anode catalyst layer in the starting process of the fuel cell;
the public circuit is used for representing dynamic influences of internal resistance change of the galvanic pile film, temperature and water content in the galvanic pile on the internal electric behavior of the fuel cell;
the cathode charge transfer circuit comprises a cathode charge transfer resistor, a cathode oxygen reduction reaction inductor and a first diode which are sequentially connected in series, and the cathode leakage circuit comprises a cathode leakage resistor, a cathode leakage inductor and a second diode which are sequentially connected in series;
the anode charge transfer circuit comprises an anode charge transfer resistor, an anode hydrogen oxidation reaction inductor and a third diode which are sequentially connected in series, and the anode leakage circuit comprises an anode leakage resistor, an anode leakage inductor and a fourth diode which are sequentially connected in series;
the common circuit comprises a high-frequency resistor, a high-frequency inductor and a linear voltage source which are sequentially connected in series.
2. The equivalent circuit model of a fuel cell start-up procedure according to claim 1, characterized in that: the cathode leakage resistance and the anode leakage resistance are constant values.
3. The equivalent circuit model of a fuel cell start-up procedure according to claim 1, characterized in that: the voltage rising time of the linear voltage source E is trise, and the delay time of the hydrogen interface reaching the adjacent partition is tdelay;
in the equivalent hydrogen flow channel, for the nth partition, when the hydrogen interface does not reach the partition yet, the value of E is 0; when the hydrogen interface reaches this zone, which is activated immediately, E rises linearly from 0 to 1V in the trie time, E has the expression:
Figure QLYQS_1
wherein tdelay i For the delay time of the hydrogen interface from the i-1 th partition to the i-th partition,
Figure QLYQS_2
the time required for the hydrogen interface to reach the ith partition from the flow channel inlet of the equivalent hydrogen flow channel.
4. The equivalent circuit model of a fuel cell start-up procedure according to claim 1, characterized in that: the number of partitions is a multiple of 8.
5. The equivalent circuit model of a fuel cell start-up procedure according to claim 1, characterized in that: the equivalent hydrogen flow channels are equal to the fuel cell basic units of the fuel cell stack in number, and the equivalent hydrogen flow channels are connected in series end to end through bipolar plate resistors.
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