JP2023142502A - fuel cell system - Google Patents

Abstract

To provide a fuel cell system that can suppress variations in anode gas concentration within an anode gas flow path during high potential avoidance operation.SOLUTION: A fuel cell system includes a fuel cell, an anode gas supply mechanism that supplies anode gas to the fuel cell, and a control device that controls an operating condition of the fuel cell. The control device includes: a first instruction unit that instructs the anode gas supply mechanism to perform pulsating operation during high potential avoidance operation; a determination unit that determines whether hydrogen deficiency has occurred after the start of the high potential avoidance operation; and a second instruction unit that instructs to change a current value of the fuel cell when the determination unit determines that hydrogen deficiency has occurred.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to fuel cell systems.

A fuel cell system is a system that generates electricity by supplying fuel gas (anode gas) and oxidizing gas (cathode gas) to a fuel cell having a fuel electrode (anode), an electrolyte membrane, and an oxygen electrode (cathode).

Further, in the fuel cell system, a circulating fuel cell system is known in which the anode gas is circulated to cause the fuel cell to generate electricity. For example, in Patent Document 1, when ending intermittent operation and transitioning to demand-responsive operation, power generation is controlled with a command value that is increased from the command value of the required power generation amount, and then the command value of the required power generation amount is A fuel cell system for controlling power generation is disclosed. Further, Patent Document 2 discloses a pulsating operation method for a fuel cell system in which N pulsating sections and non-pulsating sections performed at a constant motion pressure are repeatedly performed between the N pulsating sections. .

JP2020-140931A Patent No. 6246501

It is known that a fuel cell system performs intermittent operation in which power generation by the fuel cell is temporarily stopped during low load operation such as when the vehicle is running at low speed or idling. On the other hand, when intermittent operation is performed, the fuel cell is maintained at a relatively high voltage (open circuit voltage: OCV), and there is a risk that components such as the catalyst may deteriorate. Therefore, during intermittent operation, high potential avoidance operation may be performed in which the voltage of the fuel cell is controlled to be a predetermined low voltage (high potential avoidance voltage).

Here, if the high potential avoidance operation is performed for a long period of time, the supply of the anode gas is suppressed or stopped for a long period of time, which may cause variations in the anode gas concentration within the anode gas flow path. In particular, in pulsating operation in which the pressure of the anode gas supplied to the fuel cell is pulsated within a predetermined range, it is considered that variations in the anode gas concentration are likely to occur. If variations in anode gas concentration occur, there is a risk that anode gas deficiency (hydrogen deficiency) will occur during transition from high potential avoidance operation and intermittent operation to normal operation, and sufficient power generation may not be possible.

The present disclosure has been made in view of the above-mentioned circumstances, and a main purpose of the present disclosure is to provide a fuel cell system that can suppress variations in anode gas concentration within an anode gas flow path during high potential avoidance operation.

In order to solve the above problems, the present disclosure includes a fuel cell, an anode gas supply mechanism that supplies anode gas to the fuel cell, and a control device that controls operating conditions of the fuel cell, The control device includes a first instruction unit that instructs the anode gas supply mechanism to perform a pulsating operation during the high potential avoidance operation, and a first instruction unit that determines whether hydrogen deficiency has occurred after the start of the high potential avoidance operation. A fuel cell system is provided that includes a determination section and a second instruction section that instructs to change the current value of the fuel cell when the determination section determines that hydrogen starvation has occurred.

According to the present disclosure, after the start of high potential avoidance operation, the control device instructs to change the current value of the fuel cell if it is determined that hydrogen deficiency has occurred, thereby suppressing variations in the anode gas concentration. can.

The present disclosure has the effect of suppressing variations in the anode gas concentration within the anode gas flow path during high potential avoidance operation.

1 is a schematic diagram illustrating the configuration of a fuel cell system according to the present disclosure. FIG. 3 is a diagram illustrating a mechanism in the present disclosure. 1 is a schematic cross-sectional view illustrating a fuel cell according to the present disclosure. FIG. 2 is a flow diagram illustrating processing of a control device according to the present disclosure. FIG. 2 is a flow diagram illustrating processing of a control device according to the present disclosure.

Hereinafter, the fuel cell system according to the present disclosure will be described in detail.
FIG. 1 is a schematic diagram illustrating the configuration of a fuel cell system according to the present disclosure. A fuel cell system 100 shown in FIG. 1 includes a fuel cell 10, an anode gas supply mechanism 20 that supplies anode gas to the fuel cell 10, a monitoring unit 30 that monitors the fuel cell 10, and various controls of the fuel cell system. It includes an electronic control unit (ECU) 40 that performs the following operations. The ECU also functions as a control device in the present disclosure, which will be described later. The fuel cell 10, anode gas supply mechanism 20, monitoring unit 30, and ECU 40 (control device) will be described later.

According to the present disclosure, after the start of high potential avoidance operation, the control device instructs to change the current value of the fuel cell when determining that hydrogen deficiency has occurred. Variations in gas concentration can be suppressed. High potential avoidance operation refers to generating electricity by lowering the output voltage of the fuel cell, for example, in order to avoid elution of the catalyst. The output voltage of the fuel cell (high potential avoidance voltage) in high potential avoidance operation is not particularly limited as long as it is lower than the open circuit voltage (OCV) of the fuel cell.

Here, the mechanism in the present disclosure will be explained using FIG. 2. FIG. 2 is a diagram illustrating voltage (high potential avoidance voltage) and current during high potential avoidance operation, and anode gas pressure during pulsating operation. For example, if the high potential avoidance voltage value is changed at a first time point (tp) after high potential avoidance operation is performed, the current value of the fuel cell can be changed. As the current value is changed, both the upper limit pressure and the lower limit pressure in the pulsating operation are changed, so the timing of injection of the anode gas can be shifted. As a result, the anode gas within the anode gas flow path can be made to flow more, and variations in the anode gas concentration within the anode gas flow path, particularly within the anode gas circulation path shown in FIG. 1, can be suppressed.

1. Fuel Cell FIG. 3 is a schematic cross-sectional view illustrating a fuel cell in the present disclosure. The fuel cell (single cell) 10 shown in FIG. 3 is a membrane-electrode in which a cathode gas diffusion layer 1, a cathode catalyst layer 2, an electrolyte membrane 3, an anode catalyst layer 4, and an anode gas diffusion layer 5 are laminated in this order. It has a joined body (MEA) 11 and two separators 12 that sandwich the MEA 11. The fuel cell may be a single cell or a laminate in which a plurality of single cells are stacked.

Examples of the electrolyte membrane include fluorine-based electrolyte membranes such as perfluorosulfonic acid membranes and non-fluorine-based electrolyte membranes. Examples of non-fluorine electrolyte membranes include hydrocarbon electrolyte membranes. The thickness of the electrolyte membrane is, for example, 5 μm or more and 100 μm or less.

The cathode catalyst layer and the anode catalyst layer include, for example, a catalyst metal that promotes an electrochemical reaction, a base material that supports the catalyst metal, an electrolyte that has proton conductivity, and carbon particles that have electron conductivity. Examples of the catalyst metal include simple metals such as Pt (platinum) and Ru (ruthenium), and alloys containing Pt. Examples of the electrolyte include fluororesin. Furthermore, examples of the base material and the conductive material include carbon materials such as carbon. The thickness of the cathode catalyst layer and the anode catalyst layer is, for example, 5 μm or more and 100 μm or less, respectively.

The anode side gas diffusion layer and the cathode side gas diffusion layer may be electrically conductive members having gas permeability. Examples of the conductive member include carbon porous bodies such as carbon cloth and carbon paper, and metal porous bodies such as metal mesh and foam metal. The thicknesses of the anode side gas diffusion layer and the cathode side gas diffusion layer are, for example, 5 μm or more and 100 μm or less, respectively.

The separator may have a gas path on the surface facing the gas diffusion layer (the anode gas diffusion layer and the cathode gas diffusion layer). Examples of the material of the separator include metal materials such as stainless steel and carbon materials such as carbon composite materials. Note that this separator has electronic conductivity and also functions as a current collector for the generated electricity.

2. Anode Gas Supply Mechanism The fuel cell system according to the present disclosure includes an anode gas supply mechanism that supplies anode gas to the fuel cell. Typically, as shown in FIG. 1, the anode gas supply mechanism includes an anode gas circulation path 20A through which anode gas circulates, and an anode gas supply path 20B that supplies anode gas to the anode gas circulation path 20A.

Further, as shown in FIG. 1, the anode gas circulation path 20A includes an ejector 21 for supplying a mixed gas containing anode gas and anode off-gas to the fuel cell 10, and an ejector 21 for supplying a mixed gas containing anode gas and anode off-gas to the fuel cell 10, and an ejector 21 for supplying a mixed gas containing anode gas and anode off-gas to the fuel cell 10. a gas-liquid separator 22 that removes gas, a pressure sensor 23 that measures the pressure of the anode gas supplied to the fuel cell 10, and a gas sensor 24 that measures the anode gas concentration in the anode gas circulation path 20A inside the fuel cell, for example. may be placed. The pressure sensor and gas sensor output their measurement results to the ECU 40.

Further, as shown in FIG. 1, a gas tank 25 that stores anode gas (for example, hydrogen gas) and an injector 26 that injects the anode gas may be arranged in the anode gas supply path 20B.

The anode gas supply mechanism can perform pulsating operation by controlling, for example, the ejector 21, injector 26, and valves (not shown) shown in FIG. 1 by the ECU 40. Further, for example, by adjusting the amount of anode gas supplied by the anode gas supply mechanism, high potential avoidance operation of the fuel cell can be performed.

3. Monitoring Unit The fuel cell system may include a monitoring unit that monitors the fuel cell. As shown in FIG. 1, the monitoring unit 30 monitors the state of the fuel cell 10 and outputs the monitoring result to the ECU 40. Preferably, the monitoring unit includes at least a voltage sensor that measures the voltage (OCV) of the fuel cell and a current sensor that measures the current value of the fuel cell.

A control device, which will be described later, may perform control to perform high potential avoidance operation based on the voltage value and current value measured by the monitoring unit.

4. Control Device (1) Configuration of Control Device The fuel cell system according to the present disclosure includes a control device that controls operating conditions of the fuel cell. The control device instructs the anode gas supply mechanism to perform pulsating operation during high potential avoidance operation, and controls the current value of the fuel cell if it is determined that hydrogen deficiency has occurred after the start of high potential avoidance operation. Configured to instruct you to make changes.

As described above, the electronic control unit (ECU) also functions as a control device in the present disclosure, and includes a CPU (Central Processing Unit), a memory, and an input/output port for inputting and outputting various signals. The memory includes, for example, ROM (Read Only Memory), RAM (Random Access Memory), and rewritable nonvolatile memory. Various controls are executed by the CPU executing programs stored in the memory. The various controls performed by the ECU are not limited to processing by software, but can also be processed by dedicated hardware (electronic circuits).

The control device includes a first instruction section, a determination section, and a second instruction section as processing blocks for realizing its functions. The control device also acquires at least one of the voltage value measured by the voltage sensor, the current value acquired by the current sensor, the anode gas concentration in the anode gas circulation path measured by the gas sensor, and the anode gas pressure measured by the pressure sensor. , an acquisition unit.

The first instruction unit instructs the anode gas supply mechanism to perform pulsating operation during high potential avoidance operation. For example, the first instruction unit can cause the anode gas supply mechanism to perform a pulsating operation during the high potential avoidance operation by controlling the components of the anode gas supply mechanism such as the ejector, the injector, and the valve.

The determination unit is configured to determine whether hydrogen deficiency has occurred after the high potential avoidance operation is started. The determination unit may determine that hydrogen deficiency has occurred when a predetermined period of time has elapsed since the start of the high potential avoidance operation. Alternatively, it may be determined that hydrogen deficiency has occurred when the anode gas concentration measured by the gas sensor is less than a threshold (first threshold). The determination unit also includes a first determination unit that determines whether or not a predetermined time has elapsed since the start of the high potential avoidance driving; In this case, the anode gas concentration measured by the gas sensor may include a second determination unit that determines whether or not the anode gas concentration is less than a threshold value. In this case, if the second determining section determines that the amount is less than the threshold, the determining section determines that hydrogen deficiency has occurred. As for the "predetermined time" and the "threshold value," it is preferable to conduct a preliminary test and record them in the memory in advance, for example.

The second instruction unit is configured to issue an instruction to change the current value of the fuel cell when the determination unit determines that hydrogen deficiency has occurred. The current value of the fuel cell can be changed by changing at least one of the voltage value in high potential avoidance operation (high potential avoidance voltage value) and the amount of gas (cathode gas and anode gas) supplied to the fuel cell. can. It is preferable that the amount of change in the current value be recorded in advance in a memory, for example.

Furthermore, the second instruction section may instruct the length for which the changed current value is maintained. For example, as shown in FIG. 2, when the current value is changed, the upper limit pressure and lower limit pressure of the anode gas are changed. Therefore, the second instruction section may instruct the length for which the changed current value is maintained based on the number of times the anode gas pressure reaches the upper limit pressure (the number of pulsations). For example, the second instruction unit may instruct the current value after the change to be maintained until the number of pulsations reaches a predetermined number (second threshold). Furthermore, when the second threshold value is reached, the second instruction unit may instruct the electric current value to be returned to the value before the change and to continue the high potential avoidance operation. It is preferable to record the second threshold value in the memory in advance.

(2) Processing executed by control device FIG. 4 is a flowchart illustrating processing executed by the control device according to the present disclosure. In step S1, an instruction is given to perform pulsating operation during high potential avoidance operation. Then, in step S2, it is determined whether a predetermined time has elapsed since the start of the high potential avoidance operation. If the predetermined time has elapsed, it is determined that hydrogen deficiency has occurred, and the process proceeds to step S3, where the current value is changed. Then, in step S4, high potential avoidance operation is performed with the changed current value until the number of pulsations reaches a predetermined number. When the number of pulsations reaches a predetermined number of times, in step S5, the current value is returned to the original value and an instruction is given to continue the high potential avoidance operation, and the process ends.

Further, as shown in FIG. 5, if it is determined in step S2 that a predetermined time has elapsed since the start of the high potential avoidance operation, the process may proceed to step S2'. Then, when the anode gas concentration inside the fuel cell is less than the threshold value, it may be determined that hydrogen deficiency has occurred, and the process may proceed to step S3.

Note that the present disclosure is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any configuration that has substantially the same technical idea as the claims of the present disclosure and provides similar effects is the present invention. within the technical scope of the disclosure.

10...Fuel cell 20...Anode gas supply mechanism 20A...Anode gas circulation path 20B...Anode gas supply path 30...Monitoring unit 40...ECU
100...Fuel cell system

Claims (1)

fuel cell and
an anode gas supply mechanism that supplies anode gas to the fuel cell;
A control device that controls operating conditions of the fuel cell,
The control device includes:
a first instruction unit that instructs the anode gas supply mechanism to perform pulsating operation during high potential avoidance operation;
a determination unit that determines whether hydrogen deficiency occurs after the start of the high potential avoidance operation;
a second instruction unit that instructs to change the current value of the fuel cell when the determination unit determines that hydrogen deficiency has occurred;
A fuel cell system with