CN114865014A - Purging method for fuel cell - Google Patents
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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
- H01M8/04228—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 shut-down
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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
- H01M8/04291—Arrangements for managing water in solid electrolyte fuel cell systems
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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
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
- H01M8/04303—Processes for controlling fuel cells or fuel cell systems applied during specific periods applied during shut-down
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- H—ELECTRICITY
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- 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
- H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
- H01M8/04537—Electric variables
- H01M8/04634—Other electric variables, e.g. resistance or impedance
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Abstract
The invention discloses a fuel cell purging method, which purges water in a cell stack after the cell stack is shut down, and monitors the impedance of the stack in the purging process: in the first blowing stage, air flow is introduced into the cell stack for blowing in a constant-pressure constant-flow mode until the monitored resistance of the cell stack reaches a first resistance threshold value, and the set range is a target resistance valueR dry 50% to 70%; in the second purging stage, gas flow is introduced into the cell stack for purging in a mode of boosting pressure and increasing flow until the monitored resistance of the cell stack reaches a second resistance threshold value, wherein the set range isR dry 85% to 100%; in the third purging stage, the air flow is introduced into the battery in a mode of increasing the pressure and increasing the flow, then decreasing the pressure and decreasing the flow and then increasing the pressure and increasing the flowPurging the stack until the monitored resistance of the stack reaches a third resistance threshold, wherein the set range isR dry 98% to 100%. Tests prove that the battery purging method has the advantages of low gas consumption and short purging time.
Description
Technical Field
The invention relates to the field of fuel cell control, in particular to a fuel cell purging method.
Background
In the operation process of the fuel cell stack, gas with certain humidity needs to be introduced into the cathode and the anode, and the cathode can produce a large amount of water, so when the stack is shut down, if the membrane electrode and the water in the flow channel are not dried, the cold start failure of the stack or the flooding during the start of the stack is easily caused.
The relevant patents are mainly directed at a detection method for controlling the start and stop of purging, for example, a high-frequency impedance detection method is used for judging whether the residual water content in the reactor reaches the standard: and continuously carrying out constant-current constant-voltage ventilation and purging on the electric pile, and stopping purging when the real-time high-frequency impedance is higher than a set threshold value.
For example, in the chinese patent application with publication number CN111029623A, the disclosed purging strategy takes long time and requires large purging gas flow, so that the purging efficiency is low, the waste gas is not economical; the patent application does not consider the influence of a steady-state process, namely the internal resistance value meets the requirement after one-time purging is finished, but after the gas diffusion layer is placed for a period of time, the internal resistance value slowly decreases until the internal resistance value is stable, mainly because local residual water is not really discharged out of the membrane electrode under the purging of the atmospheric gas flow, but in the porous capillary structure of the gas diffusion layer, the local residual water is redistributed and remained in the membrane electrode again after a period of time of the steady-state process (the local residual water is diffused from a high-concentration area to a low-concentration area until the local residual water is balanced due to the influence of concentration gradient), the purging is incomplete, and the purging requirement cannot be met actually.
Also, for example, chinese patent application publication No. CN113839068A discloses an intermittent multiple purging strategy, but the system is too complex, and the constant-current constant-pressure strategy still has low purging efficiency and is not economical.
The above background disclosure is only for the purpose of assisting understanding of the inventive concept and technical solutions of the present invention, and does not necessarily belong to the prior art of the present patent application nor give technical teaching; the above background should not be used to assess the novelty and inventive aspects of the present application in the absence of express evidence that the above disclosure is published prior to the filing date of the present patent application.
Disclosure of Invention
The invention aims to provide a fuel cell purging method for implementing different purging strategies in stages, which improves the purging efficiency and the purging effect.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a fuel cell purge method of purging water in a fuel cell stack after shutdown of the stack, the impedance of the stack being monitored during the purge, the purge method comprising purging in three purge stages:
in the first blowing stage, air flow is introduced into the cell stack for blowing in a constant-pressure constant-flow mode until the monitored impedance of the cell stack reaches a preset first impedance threshold value, wherein the set range of the first impedance threshold value is 50-70% of a target impedance value;
in the second purging stage, gas flow is introduced into the cell stack for purging in a pressure-boosting and flow-boosting mode until the monitored impedance of the cell stack reaches a preset second impedance threshold value, wherein the set range of the second impedance threshold value is 85% -100% of the target impedance value;
and in the third purging stage, the gas flow is introduced into the cell stack for purging in a mode of increasing the pressure and increasing the flow rate and then decreasing the pressure and decreasing the flow rate until the impedance of the cell stack is monitored to reach a preset third impedance threshold, wherein the set range of the third impedance threshold is 98-100% of the target impedance value.
In the third purging stage, after the pressure and the flow are increased and then reduced, the gas flow is introduced into the cell stack for purging in a manner of increasing the pressure and the flow until the monitored impedance of the cell stack reaches a preset third impedance threshold, wherein the gas flow back pressure value increased for the second time is greater than the gas flow back pressure value increased for the first time, and the gas flow value increased for the second time is greater than the gas flow value increased for the first time.
Further, the volume flow of the purging airflow of the first purging stage is controlled to enable the current density of the galvanic pile during operation to be between 0.1 and 0.3A/cm 2 Corresponding anode required gasA volumetric flow value of the body; controlling the volume flow of the purge gas flow of the second purge stage from the volume flow value of the anode required gas corresponding to the first current density value to the volume flow value of the anode required gas corresponding to the second current density value when the galvanic pile is operated, wherein the first current density value is set to be in the range of 0.1 to 0.3A/cm 2 The second current density value is set within the range of 0.3 to 0.7A/cm 2 。
Further, the flow of the purge gas flow in the third purge stage is controlled to increase from the volume flow value of the anode required gas corresponding to the first current density value to the volume flow value of the anode required gas corresponding to the third current density value, decrease to the volume flow value of the anode required gas corresponding to the first current density value and increase to the volume flow value of the anode required gas corresponding to the fourth current density value when the galvanic pile is in operation, wherein the first current density value is set to be in a range of 0.1 to 0.3A/cm 2 The third current density value is set within the range of 0.4 to 0.5A/cm 2 The fourth current density value is set within the range of 0.5 to 0.8A/cm 2 ；
The flow rate of the initial purge gas flow of the second purge stage is the same as or different from the flow rate of the initial purge gas flow of the third purge stage.
Further, the flow rate of the air flow is calculated by the following formula:
Further, the gas flow back pressure of the first blowing stage is controlled to be less than 0.2kPa, the gas flow back pressure of the second blowing stage is controlled to be increased from a first pressure value to a second pressure value, wherein the first pressure value is set within a range of 2-20 kPa, the second pressure value is set within a range of 15-40 kPa, and the first pressure value is smaller than the second pressure value.
Further, the gas flow back pressure of the third purging stage is controlled to increase from a first pressure value to a third pressure value, decrease to the first pressure value and then increase to a fourth pressure value, wherein the first pressure value is set within a range of 2 to 20 kPa, the third pressure value is set within a range of 20 to 40 kPa, the fourth pressure value is set within a range of 20 to 40 kPa, and the third pressure value is smaller than the fourth pressure value.
Further, the first pressure value of the second purging stage is the same as or different from the first pressure value of the third purging stage; alternatively, the back pressure of the purge gas flow of the first purge stage is 0.
Further, after the first purging stage is completed, the second purging stage is started after waiting for a first time period, wherein the set range of the first time period is 1-5 min;
after the second purging stage is finished, starting the third purging stage after waiting for a second time period, wherein the set range of the second time period is 1-5 min;
the set value of the first time period is the same as or different from that of the second time period.
Further, the target impedance value is a qualified impedance value of the fuel cell stack under a water content condition that meets a shutdown requirement of the fuel cell stack product.
Further, the fuel cell purge method further includes: a plurality of blowing schemes are formulated, at least one blowing parameter is different among the blowing schemes, and the blowing effect of different blowing schemes is compared to determine a better blowing scheme;
wherein the purging effect is evaluated in the following manner:
and counting the gas flow consumption of the first purging stage, the second purging stage and the third purging stage, and/or counting the purging time from the beginning of the first purging stage to the end of the third purging stage.
Further, the preferred purge schedule is determined as:
controlling the gas flow back pressure of the first blowing stage to be less than 0.1 kPa, and controlling the flow of the blowing gas flow of the first blowing stage to ensure that the current density is between 0.15 and 0.25A/cm when the galvanic pile operates 2 The volume flow value of the gas required by the corresponding anode is calculated until the impedance of the galvanic pile reaches a preset first impedance threshold value, wherein the set range of the first impedance threshold value is 58-62% of the target impedance value;
controlling the gas flow back pressure of the second purging stage to be increased from a first pressure value to a second pressure value, and controlling the flow of the purging gas flow of the second purging stage to be increased from the volume flow value of the gas required by the anode corresponding to the first current density value to the volume flow value of the gas required by the anode corresponding to the second current density value when the galvanic pile operates until the impedance of the galvanic pile is monitored to reach a preset second impedance threshold value, wherein the set range of the second impedance threshold value is 92% -98% of the target impedance value, the set range of the first pressure value is 8-12 kPa, the set range of the second pressure value is 20-35 kPa, and the set range of the first current density value is 0.15-0.25A/cm 2 The second current density value is set within the range of 0.4 to 0.6A/cm 2 ；
Controlling the gas flow back pressure of the third purging stage to increase from a first pressure value to a third pressure value, decrease to the first pressure value and then increase to a fourth pressure value, and controlling the flow of the purging gas flow of the third purging stage to increase from the volume flow value of the anode required gas corresponding to the first current density value to the volume flow value of the anode required gas corresponding to the third current density value and decrease to the volume flow value of the anode required gas corresponding to the first current density value and then increase to the volume flow value of the anode required gas corresponding to the fourth current density value when the galvanic pile operates until the monitored impedance of the galvanic pile reaches a preset third impedance threshold value, wherein the set range of the third impedance threshold value is 99-100% of the target impedance value, the set range of the first pressure value is 8-12 kPa, and the set range of the third pressure value is 22-28 kPa, the set range of the fourth pressure value is 32-40 kPa, and the set range of the first current density valueIs 0.15 to 0.25A/cm 2 The third current density value is set within the range of 0.42A/cm 2 To 0.48A/cm 2 The fourth current density value is set within the range of 0.55 to 0.65A/cm 2 。
Further, the preferred purge schedule is determined as:
controlling the airflow backpressure of the first blowing stage to be 0, and controlling the flow of the blowing airflow of the first blowing stage to be 0.2 +/-0.01A/cm of current density when the galvanic pile operates 2 The volume flow value of the gas required by the corresponding anode is up to 60% of the target impedance value;
waiting for 2 +/-0.3 min;
controlling the gas flow back pressure of the second purging stage to be increased from 10 +/-0.1 kPa to 30 +/-0.1 kPa, and controlling the flow of the purging gas flow of the second purging stage to be increased from the current density of 0.2 +/-0.01A/cm when the galvanic pile runs 2 The volume flow value of the gas required by the corresponding anode is increased to 0.5 +/-0.01A/cm of current density 2 The volume flow value of the gas required by the corresponding anode is detected until the impedance of the galvanic pile reaches 95% of the target impedance value;
waiting for 3 +/-0.5 min;
controlling the gas flow back pressure of the third purging stage to be increased from 10 +/-0.1 kPa to 25 +/-0.1 kPa, and then decreased to 10 +/-0.1 kPa to 35 +/-0.1 kPa, and controlling the flow of the purging gas flow of the third purging stage to be controlled from the current density of 0.2 +/-0.01A/cm when the galvanic pile operates 2 The volume flow value of the gas required by the corresponding anode is increased to 0.45 +/-0.01A/cm of current density 2 The volume flow value of the gas required by the anode is reduced to 0.2 +/-0.01A/cm of current density 2 The volume flow value of the gas required by the corresponding anode is increased to 0.6 +/-0.01A/cm of current density 2 And the volume flow value of the gas required by the corresponding anode is detected until the impedance of the galvanic pile reaches 100 percent of the target impedance value.
The technical scheme provided by the invention has the following beneficial effects:
a. the shutdown electric pile is purged by adopting different purging strategies stage by stage, and the three stages are reasonable in section: adopting lower flow rate in the early stage,The lower pressure gas flow is primarily purged to reachR dry About 60 percent of the total mass of the waste gas, further purging the waste gas by adopting gas flow with gradually increased flow and back pressure in the middle period until the waste gas reaches the total massR dry About 95 percent of the total amount of the waste gas, and blowing the waste gas to a higher air flow after the flow and the back pressure are increased first and then decreased to be higher in the later periodR dry ；；
b. The purging strategy of each stage is particularly emphasized: when the content reaches 60 percentR dry Before, selecting gentle airflow and considering both air consumption and purging; at 60 percentR dry To 95 percentR dry In the middle stage, the atmospheric flow is gradually increased, and the blowing efficiency is emphasized; at 95%R dry To 100 percentR dry And (3) preventing or reducing the phenomenon that the internal resistance value slowly decreases after purging is finished by using a mode of first rising, then falling and then rising.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic basic flow diagram of a fuel cell purge method provided by an exemplary embodiment of the present invention;
FIG. 2 is a schematic flow diagram of a preferred purge scheme provided by an exemplary embodiment of the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, apparatus, article, or device that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or device.
The gas diffusion layer in the fuel cell membrane electrode is of a porous capillary structure, water in the gas diffusion layer is not easy to blow out of a stack, the phenomenon that the internal resistance value is slowly reduced until the internal resistance value is stable after the gas diffusion layer is subjected to primary purging until the internal resistance value of the fuel cell meets the requirement and is kept standing for a period of time is mainly caused by the fact that local residual water is not really discharged out of the membrane electrode under the purging of large gas flow, but is in the porous capillary structure of the gas diffusion layer, the local residual water is uniformly distributed in the membrane electrode again after a period of time of steady-state process (due to the influence of concentration gradient, the local residual water is diffused from a high-concentration area to a low-concentration area until the local residual water is balanced), and the current purging actually does not meet the purging requirement, namely the water content in the stack does not meet the shutdown requirement, particularly the water content index requirement in the shutdown requirement of a fuel cell stack product, if the purging does not reach the standard, the water content in the galvanic pile is higher than the index requirement. The present invention aims to provide a fuel cell purge method that addresses the above-identified deficiencies.
In one embodiment of the invention, a fuel cell purge method is provided for purging water in a fuel cell stack in three purge stages after shutdown of the stack, the completion of the three purge stages being determined by monitoring the impedance of the stack during the purge, as shown in fig. 1, the purge method comprising the steps of:
in the first blowing stage, air flow is introduced into the cell stack for blowing in a constant-pressure constant-flow mode until the monitored impedance of the cell stack reaches a preset first impedance threshold value, wherein the set range of the first impedance threshold value is 50-70% of a target impedance value; the target impedance value is the qualified impedance value of the fuel cell stack under the condition of water content meeting the shutdown requirement of the fuel cell stack product, and is hereinafter referred to as the qualified impedance valueR dry 。
In the second purging stage, gas flow is introduced into the cell stack for purging in a pressure-boosting and flow-boosting mode until the monitored impedance of the cell stack reaches a preset second impedance threshold value, wherein the set range of the second impedance threshold value is 85% -100% of the target impedance value;
and in the third purging stage, the gas flow is introduced into the cell stack for purging in a mode of increasing the pressure and increasing the flow rate and then decreasing the pressure and decreasing the flow rate until the impedance of the cell stack is monitored to reach a preset third impedance threshold, wherein the set range of the third impedance threshold is 98-100% of the target impedance value.
As shown in fig. 1, in the third purging stage, after the pressure and the flow are increased and then decreased, the gas flow is introduced into the cell stack for purging in a manner of increasing the pressure and the flow until the impedance of the cell stack reaches a preset third impedance threshold, wherein the gas flow back pressure value increased for the second time is greater than the gas flow back pressure value increased for the first time, and the gas flow value increased for the second time is greater than the gas flow value increased for the first time.
The following takes a fuel cell stack product with a power of 80 kW as an example, and the specific air pressure value and flow value of constant pressure and constant flow, pressure rise flow, pressure drop flow after pressure rise flow, and pressure rise flow after pressure rise flow are combined to describe the scheme of the embodiment:
a first purging stage: constant pressure and constant flow:
controlling the flow of the purge gas flow of the first purge stage to be 0.1-0.3A/cm of current density when the galvanic pile operates 2 Corresponding volume flow value of anode required gas；
Specifically, the flow rate of the airflow is calculated by the following formula:
wherein, in the step (A),vthe volumetric flow of the gas required by the anode for the operation of the stack,jis the current density of the electric pile,Athe reaction area is the area of reaction,athe number of single cell sections contained in the electric pile,Sin the form of a stoichiometric ratio,V m is the molar volume of the gas,ntransferring the number of electrons for the reaction;Fis the Faraday constant inC/ mol(ii) a For a 80 kW fuel cell stack product in this example, 0.1 to 0.3A/cm was calculated 2 The current density of (a) is in the range of 70 to 230 NLPM, and the gas flow rate is converted from the current density.
The back pressure of the gas flow in the first purge stage is controlled to be 0.2kPa or less.
Until the resistance of the pile is detected to be between 50 percent R dry To 70 percentR dry The purging operation in the first purging stage can be stopped by a certain set value.
A second purging stage: pressure and flow rate increase:
controlling the flow of the purge gas flow of the second purge stage from the volume flow value of the anode required gas corresponding to the first current density value to the volume flow value of the anode required gas corresponding to the second current density value when the galvanic pile is operated, wherein the first current density value is set to be in the range of 0.1 to 0.3A/cm 2 Converted into an airflow flow range of 70 to 230 NLPM, and the set range of the second current density value is 0.3 to 0.7A/cm 2 Converted to an airflow range of 230 to 530 NLPM.
And controlling the gas flow back pressure of the second purging stage to increase from a first pressure value to a second pressure value, wherein the first pressure value is set within a range of 2-20 kPa, the second pressure value is set within a range of 15-40 kPa, and the first pressure value is smaller than the second pressure value.
Until the impedance of the stack is monitoredUp to 85 percent R dry To 100 percentR dry The purging operation of the second purging stage may be stopped at a set value therebetween.
And a third purging stage: firstly, increasing pressure and increasing flow, then reducing pressure and decreasing flow, and then increasing pressure and increasing flow:
controlling the flow of the purging gas flow of the third purging stage from the volume flow value of the anode required gas corresponding to the first current density value to the volume flow value of the anode required gas corresponding to the third current density value when the galvanic pile operates, and from the volume flow value of the anode required gas corresponding to the first current density value to the volume flow value of the anode required gas corresponding to the fourth current density value, wherein the first current density value is set within the range of 0.1 to 0.3A/cm 2 Converted into an airflow flow range of 70 to 230 NLPM, and the set range of the third current density value is 0.4A/cm 2 To 0.5A/cm 2 The fourth current density value is set within a range of 0.5 to 0.8A/cm in terms of an airflow flow rate range of 300 to 380 NLPM 2 Converting into an airflow flow range of 380 to 610 NLPM;
and controlling the gas flow back pressure of the third purging stage to increase from a first pressure value to a third pressure value, decrease to the first pressure value and then increase to a fourth pressure value, wherein the first pressure value is set within a range of 2-20 kPa, the third pressure value is set within a range of 20-40 kPa, the fourth pressure value is set within a range of 20-40 kPa, and the third pressure value is smaller than the fourth pressure value.
Until the resistance of the galvanic pile reaches 100 percentR dry The purging operation in the third purging stage can be stopped to complete the purging. The purge gas flows in the above-mentioned three purge stages are simultaneously applied to the cathode and anode of the stack. The flow rate of the purge gas is usually set according to an empirical value (the higher the power of the galvanic pile is), or according to an experiment, and unlike the conventional method for setting the flow rate of the purge gas, the flow rate of the purge gas is set according to the conventional method that the volume of the anode required gas corresponding to the preset target current density value is preset when the galvanic pile is operatedThe accumulated flow value is used as a set reference, and the control strategy has the advantages that the control strategy is suitable for fuel cell stack products with various power specifications, the flow of the purge air flow corresponding to the stacks with different powers and different structures can be determined only by the flow calculation formula, and the flow setting result of the matched purge air flow is obtained by performing a retest on the stack with a new power specification in a conventional way.
The flow rate of the initial purge gas flow of the second purge stage and the flow rate of the initial purge gas flow of the third purge stage are both in the range of 70 to 230 NLPM, but the specific set values may be the same or different; the first pressure value of the second purging stage and the first pressure value of the third purging stage both range from 2 to 20 kPa, but the specific set values may be the same or different.
As in the first embodiment, the moisture is not completely discharged from the membrane electrode under the purging of the gas flow, but the residual water is re-uniformly distributed in the porous capillary structure of the gas diffusion layer after a period of steady-state process, so that, in one possible embodiment of the present invention, after the first purging stage is completed, the second purging stage is started after waiting for a first period of time, which is set in a range of 1 to 5 min; after the second purging stage is finished, starting the third purging stage after waiting for a second time period, wherein the set range of the second time period is 1-5 min; the set value of the first time period and the set value of the second time period are the same or different.
On the basis of the frame, a plurality of blowing schemes are formulated, at least one blowing parameter is different among the blowing schemes, and the blowing effect of different blowing schemes is compared to determine a better blowing scheme;
wherein the purging effect is evaluated in the following manner:
and counting the gas flow consumption of the first purging stage, the second purging stage and the third purging stage, and/or counting the purging time from the beginning of the first purging stage to the end of the third purging stage. The smaller the gas flow consumption is, the shorter the purging time is, the better the purging effect is, otherwise, the worse the purging effect is. Specifically, corresponding weight values may be set for the gas flow consumption and the purging time, for example, if the weight coefficients of the two are 0.85 and 0.15, the following calculation is performed: and (4) gas flow consumption of 0.85+ purging time of 0.15, obtaining an evaluation score of the purging effect, wherein the higher the score is, the poorer the purging effect is represented.
The following examples and comparative examples are provided below, with an example of a fuel cell stack product of 80 kW power:
example 1
After the purging is finished for 0.5h, the resistance of the galvanic pile is reduced to 99.3 percentR dry And the resistance of the galvanic pile is reduced to 98.9 percent 12 hours after the purging is finishedR dry 。
Example 2
After the purging is finished for 0.5h, the resistance of the galvanic pile is reduced to 99.9 percentR dry And the resistance of the galvanic pile is reduced to 99.6 percent 12 hours after the purging is finishedR dry 。
Example 3
After the purging is finished for 0.5h, the resistance of the galvanic pile is reduced to 99.5 percentR dry And the resistance of the galvanic pile is reduced to 98.7 percent 12 hours after the purging is finishedR dry 。
Comparative example 1
After 0.5h of purging, the resistance of the galvanic pile is reduced to 99.1 percentR dry And the resistance of the galvanic pile is reduced to 98.2 percent 12 hours after the purging is finishedR dry 。
Comparative example 2
After the purging is finished for 0.5h, the resistance of the galvanic pile is reduced to 98.7 percentR dry And the resistance of the galvanic pile is reduced to 98.1 percent 12 hours after the purging is finishedR dry 。
Comparative example 3
According to a typical purge strategy, i.e., constant flow purge until 100% reaches a preset impedance threshold, the purge data is as follows:
after 0.5h of purging, the resistance of the galvanic pile is reduced to 97.1 percentR dry And the resistance of the galvanic pile is reduced to 95.4 percent 12 hours after the purging is finishedR dry 。
Comparing examples 1 to 3, it can be seen that example 2 has less gas consumption, shorter purging time, and reduced stack resistance drop after purging is completed, thus establishing a better purging scheme.
In the solutions of comparative examples 1 to 3, the gas consumption is greater than that of example 1, the purging time is greater than that of example 1, and the decrease trend of the resistance of the stack is more obvious after the purging is finished, so that it can be verified that the setting range given in this embodiment is a better parameter range, and in this range, the setting value applied in example 2 is a better purging solution.
The preferred parameter range purge strategy is determined as:
controlling the gas flow back pressure of the first blowing stage to be less than 0.1 kPa, and controlling the flow of the blowing gas flow of the first blowing stage to ensure that the current density is between 0.15 and 0.25A/cm when the galvanic pile operates 2 Corresponding volume flow value of anode required gas until the electric pileThe impedance reaches a preset first impedance threshold value, wherein the setting range of the first impedance threshold value is 58% to 62% of a target impedance value;
controlling the gas flow back pressure of the second purging stage to be increased from a first pressure value to a second pressure value, and controlling the flow of the purging gas of the second purging stage to be increased from the volume flow value of the gas required by the anode corresponding to the first current density value when the galvanic pile operates to the volume flow value of the gas required by the anode corresponding to the second current density value until the impedance of the galvanic pile is monitored to reach a preset second impedance threshold value, wherein the set range of the second impedance threshold value is 92% -98% of the target impedance value, the set range of the first pressure value is 8-12 kPa, the set range of the second pressure value is 20-35 kPa, and the set range of the first current density value is 0.15-0.25A/cm 2 The second current density value is set within the range of 0.4 to 0.6A/cm 2 ；
Controlling the gas flow back pressure of the third purging stage to increase from a first pressure value to a third pressure value, decrease to the first pressure value and then increase to a fourth pressure value, and controlling the flow of the purging gas flow of the third purging stage to increase from the volume flow value of the anode required gas corresponding to the first current density value to the volume flow value of the anode required gas corresponding to the third current density value and decrease to the volume flow value of the anode required gas corresponding to the first current density value and then increase to the volume flow value of the anode required gas corresponding to the fourth current density value when the galvanic pile operates until the monitored impedance of the galvanic pile reaches a preset third impedance threshold value, wherein the set range of the third impedance threshold value is 99-100% of the target impedance value, the set range of the first pressure value is 8-12 kPa, and the set range of the third pressure value is 22-28 kPa, the fourth pressure value is set within the range of 32-40 kPa, and the first current density value is set within the range of 0.15-0.25A/cm 2 The third current density value is set within the range of 0.42A/cm 2 To 0.48A/cm 2 The fourth current density value is set within the range of 0.55 to 0.65A/cm 2 。
Wherein the preferred purge scheme for example 2 was determined as shown in figure 2:
controlling the airflow backpressure of the first blowing stage to be 0, and controlling the flow of the blowing airflow of the first blowing stage to be 0.2 +/-0.01A/cm of current density when the galvanic pile operates 2 The volume flow value of the gas required by the corresponding anode is up to 60% of the target impedance value;
waiting for 2 +/-0.3 min;
controlling the gas flow back pressure of the second purging stage to be increased from 10 +/-0.1 kPa to 30 +/-0.1 kPa, and controlling the flow of the purging gas flow of the second purging stage to be increased from the current density of 0.2 +/-0.01A/cm when the galvanic pile runs 2 The volume flow value of the gas required by the corresponding anode is increased to 0.5 +/-0.01A/cm of current density 2 The volume flow value of the gas required by the corresponding anode is detected until the impedance of the galvanic pile reaches 95% of the target impedance value; in the process, the increase speeds of the airflow backpressure and the airflow flow can be adjusted, and on the premise that the airflow backpressure and the airflow flow can be increased to the final values before the end point of the stage, the slow or slowest increase speed can be selected, and the end point is reached by adopting a uniform increase mode as far as possible, so that a better purging effect is realized.
Waiting for 3 +/-0.5 min;
controlling the gas flow back pressure of the third purging stage to be increased from 10 +/-0.1 kPa to 25 +/-0.1 kPa, and then decreased to 10 +/-0.1 kPa to 35 +/-0.1 kPa, and controlling the flow of the purging gas flow of the third purging stage to be controlled from the current density of 0.2 +/-0.01A/cm when the galvanic pile operates 2 The volume flow value of the gas required by the corresponding anode is increased to 0.45 +/-0.01A/cm of current density 2 The volume flow value of the gas required by the anode is reduced to 0.2 +/-0.01A/cm of current density 2 The volume flow value of the gas required by the corresponding anode is increased to 0.6 +/-0.01A/cm of current density 2 The volume flow value of the gas required by the corresponding anode is detected until the impedance of the galvanic pile reaches 100% of the target impedance value; in the process, the increasing/decreasing/re-increasing speed of the airflow back pressure and the airflow flow can be adjusted, and the slower or the slowest of the airflow back pressure and the airflow flow can be selected on the premise that the airflow back pressure and the airflow flow can be increased to the final value before the end of the stageThe increasing/decreasing/re-increasing speed of the air pump reaches the end point by adopting a constant speed increasing/decreasing/re-increasing mode as much as possible so as to realize a better purging effect.
The invention aims to provide a fuel cell purging method reasonably divided into three stages, wherein each stage has a core strategy: most of liquid in the galvanic pile is blown out by utilizing the moderate air flow in the early stage, most of residual liquid is blown out by utilizing the gradually-enhanced air flow in the middle stage, the air consumption and the blowing efficiency are considered, the gradually-enhanced, weakened and gradually-enhanced air flow is blown to the terminal point in the later stage, and the phenomenon that the internal resistance value is slowly reduced after blowing is finished is weakened by utilizing the waiting time period among all stages.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The foregoing is directed to embodiments of the present application and it is noted that numerous modifications and adaptations may be made by those skilled in the art without departing from the principles of the present application and are intended to be within the scope of the present application.
Claims (13)
1. A fuel cell purge method of purging water from a fuel cell stack after shutdown of the stack, wherein the impedance of the stack is monitored during the purge, the purge method comprising purging in three purge stages:
in the first blowing stage, air flow is introduced into the cell stack for blowing in a constant-pressure constant-flow mode until the impedance of the cell stack is monitored to reach a preset first impedance threshold, wherein the set range of the first impedance threshold is 50-70% of a target impedance value;
in the second purging stage, gas flow is introduced into the cell stack for purging in a pressure-boosting and flow-boosting mode until the monitored impedance of the cell stack reaches a preset second impedance threshold value, wherein the set range of the second impedance threshold value is 85% -100% of the target impedance value;
and in the third purging stage, the gas flow is introduced into the cell stack for purging in a mode of increasing the pressure and increasing the flow rate and then decreasing the pressure and decreasing the flow rate until the impedance of the cell stack is monitored to reach a preset third impedance threshold, wherein the set range of the third impedance threshold is 98-100% of the target impedance value.
2. A fuel cell purge method according to claim 1, wherein the third purge stage is configured to purge the stack by raising the pressure and raising the flow rate before lowering the pressure and lowering the flow rate, until the stack impedance is monitored to reach a preset third impedance threshold, wherein the second raised flow back pressure value is greater than the first raised flow back pressure value, and the second raised flow rate value is greater than the first raised flow rate value.
3. A fuel cell purge method according to claim 1 or 2, wherein the volume flow rate of the purge gas flow of the first purge stage is controlled so that the current density is between 0.1 and 0.3A/cm when the stack is in operation 2 The volume flow value of the gas required by the corresponding anode; controlling the volume flow of the purge gas flow of the second purge stage from the volume flow value of the anode required gas corresponding to the first current density value to the volume flow value of the anode required gas corresponding to the second current density value when the galvanic pile is operated, wherein the first current density value is set to be in the range of 0.1 to 0.3A/cm 2 Setting of the second current density valueIn the range of 0.3 to 0.7A/cm 2 。
4. The fuel cell purge method according to claim 3, wherein the flow rate of the purge gas in the third purge stage is controlled by increasing the volume flow rate of the anode required gas corresponding to the first current density value to the volume flow rate of the anode required gas corresponding to the third current density value, decreasing the volume flow rate of the anode required gas corresponding to the first current density value, and increasing the volume flow rate of the anode required gas corresponding to the fourth current density value, wherein the first current density value is set in a range of 0.1 to 0.3A/cm 2 The third current density value is set within the range of 0.4 to 0.5A/cm 2 The fourth current density value is set within the range of 0.5 to 0.8A/cm 2 ；
The flow rate of the initial purge gas flow of the second purge stage is the same as or different from the flow rate of the initial purge gas flow of the third purge stage.
5. A fuel cell purge method according to claim 1, 2 or 4, wherein the flow rate of the gas flow is calculated by the following formula:
6. A fuel cell purge method according to claim 1 or 2, wherein the gas flow back pressure of the first purge stage is controlled to be less than 0.2kPa, the gas flow back pressure of the second purge stage is controlled to be increased from a first pressure value to a second pressure value, wherein the first pressure value is set to range from 2 to 20 kPa, the second pressure value is set to range from 15 to 40 kPa, and the first pressure value is smaller than the second pressure value.
7. The fuel cell purge method according to claim 6, wherein the gas flow back pressure in the third purge stage is controlled to increase from a first pressure value to a third pressure value, decrease to the first pressure value and then increase to a fourth pressure value, wherein the first pressure value is set within a range of 2 to 20 kPa, the third pressure value is set within a range of 20 to 40 kPa, the fourth pressure value is set within a range of 20 to 40 kPa, and the third pressure value is smaller than the fourth pressure value.
8. The fuel cell purge method of claim 7, wherein the first pressure value of the second purge stage is the same as or different from the first pressure value of the third purge stage; alternatively, the back pressure of the purge gas flow of the first purge stage is 0.
9. A fuel cell purge method according to claim 2, wherein the second purge stage is started after waiting a first period of time set in a range of 1 to 5 min after the first purge stage is completed;
after the second purging stage is finished, starting the third purging stage after waiting for a second time period, wherein the set range of the second time period is 1-5 min;
the set value of the first time period is the same as or different from that of the second time period.
10. A fuel cell purge method as claimed in claim 1, wherein the target impedance value is a qualified impedance value of the stack at a moisture content condition that meets a fuel cell stack product shutdown requirement.
11. A fuel cell purge method according to any one of claims 2, 4, 7, 8, 9, further comprising: a plurality of blowing schemes are formulated, at least one blowing parameter is different among the blowing schemes, and the blowing effect of different blowing schemes is compared to determine a better blowing scheme;
wherein the purging effect is evaluated in the following manner:
and counting the gas flow consumption of the first purging stage, the second purging stage and the third purging stage, and/or counting the purging time from the beginning of the first purging stage to the end of the third purging stage.
12. A fuel cell purge method as claimed in claim 11, wherein the preferred purge strategy is determined as:
controlling the gas flow back pressure of the first blowing stage to be less than 0.1 kPa, and controlling the flow of the blowing gas flow of the first blowing stage to ensure that the current density is between 0.15 and 0.25A/cm when the galvanic pile operates 2 The volume flow value of the gas required by the corresponding anode is calculated until the impedance of the galvanic pile reaches a preset first impedance threshold value, wherein the set range of the first impedance threshold value is 58-62% of the target impedance value;
controlling the gas flow back pressure of the second purging stage to be increased from a first pressure value to a second pressure value, and controlling the flow of the purging gas flow of the second purging stage to be increased from the volume flow value of the anode required gas corresponding to the first current density value to the volume flow value of the anode required gas corresponding to the second current density value when the galvanic pile operates until the impedance of the galvanic pile is monitored to reach a preset second impedance threshold value, wherein the set range of the second impedance threshold value is 92% -98% of the target impedance value, the set range of the first pressure value is 8-12 kPa, the set range of the second pressure value is 20-35 kPa, and the set range of the first current density value is 0.15-0.25A/cm 2 The second current density value is set within the range of 0.4 to 0.6A/cm 2 ；
Controlling the gas flow back pressure of the third purging stage to increase from a first pressure value to a third pressure value, decrease to the first pressure value and increase to a fourth pressure value, and controlling the flow of the purging gas flow of the third purging stage to be controlled by the electricityWhen the reactor is operated, the volume flow value of the anode required gas corresponding to the first current density value is increased to the volume flow value of the anode required gas corresponding to the third current density value, the volume flow value of the anode required gas corresponding to the first current density value is reduced to the volume flow value of the anode required gas corresponding to the first current density value, and the volume flow value of the anode required gas corresponding to the fourth current density value is increased to the volume flow value of the anode required gas corresponding to the fourth current density value until the impedance of the galvanic pile is monitored to reach a preset third impedance threshold value, wherein the set range of the third impedance threshold value is 99% -100% of the target impedance value, the set range of the first pressure value is 8-12 kPa, the set range of the third pressure value is 22-28 kPa, the set range of the fourth pressure value is 32-40 kPa, and the set range of the first current density value is 0.15-0.25A/cm 2 The third current density value is set within the range of 0.42A/cm 2 To 0.48A/cm 2 The fourth current density value is set within the range of 0.55 to 0.65A/cm 2 。
13. A fuel cell purge method as claimed in claim 11, wherein the preferred purge strategy is determined as:
controlling the airflow backpressure of the first blowing stage to be 0, and controlling the flow of the blowing airflow of the first blowing stage to be 0.2 +/-0.01A/cm of current density when the galvanic pile operates 2 The volume flow value of the gas required by the corresponding anode is up to 60% of the target impedance value;
waiting for 2 +/-0.3 min;
controlling the gas flow back pressure of the second purging stage to be increased from 10 +/-0.1 kPa to 30 +/-0.1 kPa, and controlling the flow of the purging gas flow of the second purging stage to be increased from the current density of 0.2 +/-0.01A/cm when the galvanic pile runs 2 The volume flow value of the gas required by the corresponding anode is increased to the current density of 0.5 +/-0.01A/cm 2 The volume flow value of the gas required by the corresponding anode is detected until the impedance of the galvanic pile reaches 95% of the target impedance value;
waiting for 3 +/-0.5 min;
controlling the gas flow back pressure of the third purging stage to increase from 10 +/-0.1 kPa to 25 +/-0.1 kPa, decrease to 10 +/-0.1 kPa and increase to35 +/-0.1 kPa, and the flow of the purge gas flow of the third purge stage is controlled by the current density of 0.2 +/-0.01A/cm when the galvanic pile operates 2 The volume flow value of the gas required by the corresponding anode is increased to 0.45 +/-0.01A/cm of current density 2 The volume flow value of the gas required by the anode is reduced to 0.2 +/-0.01A/cm of current density 2 The volume flow value of the gas required by the corresponding anode is increased to 0.6 +/-0.01A/cm of current density 2 And the volume flow value of the gas required by the corresponding anode is detected until the impedance of the galvanic pile reaches 100 percent of the target impedance value.
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| CN111224131A (en) * | 2020-01-16 | 2020-06-02 | 上海重塑能源科技有限公司 | Fuel cell system and low-temperature purging method thereof |
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| CN114447377A (en) * | 2020-10-30 | 2022-05-06 | 北京亿华通科技股份有限公司 | Shutdown purging method for fuel cell system, fuel cell system and vehicle |
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| CN111224131A (en) * | 2020-01-16 | 2020-06-02 | 上海重塑能源科技有限公司 | Fuel cell system and low-temperature purging method thereof |
| CN114447377A (en) * | 2020-10-30 | 2022-05-06 | 北京亿华通科技股份有限公司 | Shutdown purging method for fuel cell system, fuel cell system and vehicle |
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