JP2018125197A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of suppressing deterioration in a fuel cell by preventing concentration of hydrogen gas supplied to the fuel cell from becoming uneven.SOLUTION: A fuel cell system comprises: a fuel cell 101; an injector 103 which supplies hydrogen gas to the fuel cell 101; a circulation gas passage 106 which connects a hydrogen gas inlet 111 and a hydrogen gas outlet 121 of the fuel cell 101 and circulates the hydrogen gas discharged from the hydrogen gas outlet 121 and a nitrogen-containing circulation gas to the hydrogen gas inlet 111; a circulation pump 104 which pumps the circulation gas circulating in the circulation gas passage 106; and an ECU 150 which calculates a supply of hydrogen gas required for the load demanded by the fuel cell 101, and calculates a supply flow rate of hydrogen supplied by driving of the injector 103 and a circulation flow rate of the circulation gas pumped by driving of the circulation pump 104 on the basis of the calculated supply of hydrogen gas. The ECU 150 controls driving of the injector 103 and the circulation pump 104 so that the circulation flow rate calculated on the basis of the supply of hydrogen gas increases to become the supply flow rate of hydrogen or more than that.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system.

  A fuel cell generally has a stack structure (fuel cell stack) formed by stacking a plurality of fuel cell cells in which electrodes (anode electrode, cathode electrode) are arranged on both surfaces of an electrolyte membrane. A fuel cell receives a supply of a fuel gas (for example, hydrogen gas) and an oxidizing gas (for example, air) and generates power by an electrochemical reaction.

  A fuel cell system including the fuel cell includes a fuel gas supply system (hydrogen supply system) for supplying fuel gas and an oxidizing gas supply system for supplying oxidizing gas. The fuel gas supply system usually connects an injector that supplies hydrogen gas to the fuel cell, and a hydrogen gas inlet and a hydrogen gas outlet of the fuel cell, and circulates a circulating gas containing hydrogen and nitrogen discharged from the fuel cell. It has a circulation gas channel and a circulation pump provided in the circulation gas channel (Patent Document 1 below).

Japanese Patent Laid-Open No. 2006-096054

  In this type of fuel cell system, the drive of the injector and the circulation pump is controlled based on the fuel supply flow rate required for the load required for the fuel cell. In this control, the circulation pump is driven on the assumption that the hydrogen gas concentration in the circulation gas channel is uniformly mixed by driving the injector and supplying hydrogen. However, when the drive of the injector and the circulation pump is controlled in this way, the fuel gas concentration (hydrogen gas concentration) supplied to the fuel cell may continue to be uneven, and if the uneven state continues, the fuel The battery may be deteriorated.

  Accordingly, an object of the present invention is to provide a fuel cell system capable of suppressing the concentration of hydrogen gas supplied to the fuel cell from becoming non-uniform and suppressing the deterioration of the fuel cell.

  A fuel cell system according to the present invention includes a fuel cell, an injector for supplying hydrogen gas to the fuel cell, a hydrogen gas inlet and a hydrogen gas outlet of the fuel cell, and hydrogen gas and nitrogen discharged from the hydrogen gas outlet. Calculate and calculate the circulation gas flow path that circulates the circulation gas to the hydrogen gas inlet, the circulation pump that pumps the circulation gas flowing through the circulation gas flow path, and the hydrogen gas supply amount required for the load required for the fuel cell. A control unit that calculates a hydrogen supply flow rate supplied by driving the injector and a circulation flow rate of circulating gas pumped by driving the circulation pump based on the supplied hydrogen gas supply amount. The drive of the injector and the circulation pump is controlled so that the circulation flow rate calculated based on the above increases beyond the hydrogen supply flow rate.

  According to this configuration, the hydrogen gas supply amount necessary for the load required for the fuel cell is calculated by the control unit, and based on the calculated hydrogen gas supply amount, the circulation flow rate of the circulation gas pumped by the circulation pump is The drive of the injector and the circulation pump is controlled so as to increase more than the hydrogen supply flow rate supplied by the injector. As described above, when supplying the hydrogen gas supply amount necessary for the load required for the fuel cell, the hydrogen gas is rapidly mixed with the circulation gas by increasing the circulation flow rate, so that the hydrogen gas is supplied to the fuel cell. The hydrogen gas concentration is suppressed from becoming non-uniform. As a result, deterioration of the fuel cell can be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the density | concentration of the hydrogen gas supplied to a fuel cell becomes non-uniform | heterogenous, and can provide the fuel cell system which can suppress deterioration of a fuel cell.

It is a schematic block diagram which shows the hydrogen supply system of the fuel cell system in this embodiment. It is a figure which shows the modification of the fuel cell system shown in FIG. 3 is a flowchart showing hydrogen supply control performed in the fuel cell system shown in FIGS. 1 and 2. It is a figure for demonstrating hydrogen supply flow control and circulation flow control. It is a figure which shows the hydrogen partial pressure in hydrogen supply control. It is a figure which shows the hydrogen partial pressure in the conventional hydrogen supply control.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. It should be noted that the following description of the preferred embodiment is merely an example, and is not intended to limit the present invention, its application, or its use.

  First, the configuration of the fuel cell system according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram showing a fuel gas supply system of a fuel cell system. In FIG. 1, only the configuration of the fuel gas supply system is shown, and the illustration of the configuration of the oxidizing gas supply system, the cooling system, and the like is omitted. However, the fuel cell system in this embodiment has a configuration other than the configuration described below. Can be included. The fuel cell system according to the present embodiment is mounted on, for example, a fuel cell vehicle (FCHV), and functions as an in-vehicle power supply system for such a fuel cell vehicle.

  A fuel gas supply system 100 of the fuel cell system shown in FIG. 1 is a system for supplying hydrogen gas as a fuel gas to the fuel cell 101. The fuel cell 101 includes a fuel cell stack formed by stacking a plurality of cells (a single battery (power generation body) including an anode, a cathode, and an electrolyte). In the fuel cell 101, fuel gas (hydrogen) is supplied to the anode electrode and oxidizing gas (air or oxygen) is supplied to the cathode electrode to generate electric power through an electrochemical reaction.

  The fuel gas supply system 100 includes a fuel supply unit 102 as a fuel supply source storing high-pressure hydrogen gas, a fuel supply channel 108 for supplying hydrogen gas from the fuel supply unit 102 to the fuel cell 101, a fuel cell. A circulation gas passage 106 for returning the fuel off-gas (circulation gas containing hydrogen and nitrogen) discharged from 101 to the fuel supply passage 108 and an ECU 150 (control unit) are provided.

  The fuel supply channel 108 is provided with an injector 103 (fuel gas supply valve). The injector 103 may be a device having a function capable of adjusting the gas flow rate and gas pressure of the fuel gas supplied from the fuel supply unit 102. For example, the injector 103 is directly driven by an electromagnetic driving force with a predetermined driving cycle. It is configured as an electromagnetically driven on-off valve capable of adjusting the gas flow rate and the gas pressure by being driven at a distance from the valve seat. The injector 103 includes a valve seat having an injection hole for injecting gaseous fuel such as hydrogen gas, a nozzle body for supplying and guiding the gaseous fuel to the injection hole, and an axial direction (gas flow direction) with respect to the nozzle body. And a valve body that is movably accommodated and opens and closes the injection hole. The valve body of the injector 103 is driven by a solenoid that is an electromagnetic drive device, and the opening area of the injection hole can be switched between two stages or multiple stages by turning on and off the pulsed excitation current supplied to the solenoid. It has become. By controlling the gas injection time and gas injection timing of the injector 103 by a control signal output from the ECU 150, the flow rate and pressure of the hydrogen gas are controlled with high accuracy. The injector 103 directly opens and closes the valve (valve body and valve seat) with an electromagnetic driving force, and has a high responsiveness because its driving cycle can be controlled to a highly responsive region. The injector 103 changes downstream by changing at least one of the opening area (opening) and the opening time of the valve provided in the gas flow path of the injector 103 in order to supply the required gas flow rate downstream. The flow rate of gas supplied to the side (fuel cell 101 side) is adjusted.

  The fuel gas supplied from the injector 103 to the hydrogen gas inlet (hereinafter referred to as the hydrogen gas inlet 111) of the fuel cell stack is subjected to an electromotive reaction inside the fuel cell 101, and then the fuel offgas (hydrogen gas and nitrogen). Is discharged from a hydrogen gas outlet (hereinafter referred to as hydrogen gas outlet 121) of the fuel cell stack. A part of the fuel off-gas thus discharged from the hydrogen gas outlet 121 is recirculated through the circulation gas flow path 106 by the operation of the circulation pump 104 and re-supplied to the fuel cell 101 together with the fuel gas supplied from the injector 103. . As described above, the circulation gas passage 106 is provided with the circulation pump 104 that pressurizes the fuel off-gas discharged from the hydrogen gas outlet 121 and sends it to the fuel supply passage 108 side.

  Note that a discharge passage 109 is connected to the circulation gas passage 106 via a gas-liquid separator 105. Since the fuel off gas is affected by the generated water generated by the electrochemical reaction and may contain excessive moisture, the gas / liquid separator 105 recovers excess moisture in the fuel off gas. The fuel off-gas from which moisture has been recovered is pumped by the circulation pump 104 and supplied to the fuel cell 101 again. Note that an exhaust / drain valve 107 is connected to the gas-liquid separator 105 via a discharge channel 109. The water accumulated in the gas-liquid separator 105 is discharged from the gas-liquid separator 105 when the exhaust / drain valve 107 is opened by a command from the ECU 150.

  The ECU 150 (control unit) controls operations of various devices in the system, and is configured by a computer system (not shown). Such a computer system includes a CPU, a ROM, a RAM, an HDD, an input / output interface, and the like, and various control operations are realized by the CPU reading and executing various control programs recorded in the ROM. It has become. In the present embodiment, the ECU 150 calculates, for example, a hydrogen gas supply amount necessary for a load required for the fuel cell 101, and based on the calculated hydrogen gas supply amount, hydrogen of hydrogen gas supplied by driving the injector 103 is calculated. The supply flow rate and the circulation flow rate of the circulation gas pumped by driving the circulation pump 104 are calculated. The ECU 150 also controls the drive of the injector 103 and the circulation pump 104 so that the circulation flow rate is increased beyond the hydrogen supply flow rate calculated based on the hydrogen gas supply amount that satisfies the load required for the fuel cell 101.

  As a modification, in addition to the circulation pump 104, for example, an ejector 114 (see FIG. 2) or the like may be used as a hydrogen circulation mechanism. As shown in FIG. 2, the ejector 114 is provided at a junction of the fuel supply passage 108 and the circulating gas passage 106. The ejector 114 uses the flow of the fuel gas supplied from the fuel supply unit 102 as a driving flow, sucks the fuel off-gas exhausted from the fuel cell 101 from the circulation gas flow path 106, and again supplies the fuel cell off-gas to the fuel cell 101. It is a circulation means to circulate. By providing the ejector 114 as described above, the fuel off-gas can be circulated again to the fuel cell 101, and hydrogen discharged from the fuel cell 101 without being used in the electrochemical reaction can be used effectively. In FIG. 2, the configuration other than the ejector 114 is the same as that shown in FIG. Below, although the example of control of the circulation pump 104 is demonstrated, the ejector 114 can bear the same function.

  Subsequently, a control process executed by the ECU 150 will be described with reference to FIGS. 3 and 4. FIG. 3 is a flowchart for explaining hydrogen supply control (anode pressurization control) executed by ECU 150. FIG. 4 is a diagram for explaining the hydrogen supply flow rate and the circulation flow rate. The hydrogen supply flow rate shown in FIG. 4 indicates the hydrogen supply flow rate supplied by the injector, and the circulation flow rate indicates the flow rate of the circulating gas pumped by the circulation pump.

  For example, the required hydrogen partial pressure and the required pressure increase time (refer to the target pressure indicated by the anode pressure in FIG. 4) are calculated from the load required for the fuel cell (target load) when the load fluctuates or starts (step in FIG. 3). After that, the fuel supply amount is calculated from the fuel pressure increase amount and the pressure increase time.

Next, based on the fuel supply amount that satisfies the load required for the fuel cell, the flow rate of hydrogen gas supplied by the injector (hydrogen supply flow rate) and the flow rate of circulating gas pumped by the circulation pump (circulation flow rate) are calculated ( Steps S120 and S130 in FIG. 3). In this embodiment, the circulation flow rate is set to be equal to or higher than the hydrogen supply flow rate, and is preferably determined from the relationship between the fuel supply flow rate (Qinj) and the circulation flow rate (Qcir) shown in the following formula (1). As shown in the following formula (1), the circulation flow rate (Qcir) is preferably set to be an integral multiple of the fuel supply flow rate (Qinj).
Qcir = n × Qinj (n = 1, 2, 3...) (1)

  The drive of the injector 103 and the circulation pump 104 (FIG. 1 and the like) is controlled so as to satisfy the fuel supply flow rate and the circulation flow rate set based on the relationship of the above equation (1) (step S140 in FIG. 3). For example, as shown in FIG. 4, when the required hydrogen partial pressure and the required pressure increase time are calculated from the load required for the fuel cell, the injector 103 so that the circulation flow rate and the fuel supply flow rate increase with the passage of time. And the drive of the circulation pump 104 is controlled.

  As described above, the results of verifying the fuel gas concentration when the fuel supply flow rate and the circulation flow rate are controlled are shown in FIGS. FIG. 5 is a diagram for explaining the hydrogen partial pressure in the hydrogen gas inlet, the hydrogen gas outlet, and the circulation gas flow path when the fuel supply flow rate (Qinj) is set to be one time the circulation flow rate (Qcir). FIG. 6 is a diagram for explaining the hydrogen partial pressure of the hydrogen gas inlet, the hydrogen gas outlet, and the circulation gas flow path when the fuel supply flow rate (Qinj) is five times the circulation flow rate (Qcir). Note that Gi shown in FIGS. 5 and 6 represents a hydrogen partial pressure transition at the hydrogen gas inlet 111 (FIG. 1 and the like), Ge represents a hydrogen partial pressure transition at the hydrogen gas outlet 121 (FIG. 1 and the like), and Gc Shows the hydrogen partial pressure transition of the circulating gas flow path 106 (FIG. 1 etc.).

  As shown in FIG. 6, when the fuel supply flow rate (Qinj) is five times the circulation flow rate (Qcir), the hydrogen partial pressure Gi at the hydrogen gas inlet, the hydrogen partial pressure Ge at the hydrogen gas outlet, and the circulation gas flow path The hydrogen partial pressure Gc pulsates by repeatedly increasing and decreasing, and the hydrogen partial pressure becomes uniform at time t1. Conventionally, such a hydrogen partial pressure pulsation is not assumed. In detail, conventionally, the required fuel is required on the assumption that the hydrogen gas concentration in the circulation system becomes uniform quickly by the hydrogen supply from the injector (in other words, the fuel flows through the circulation gas passage). (The fuel is supplied by the injector regardless of the flow rate of the circulating gas.) However, when hydrogen is supplied based on such a requirement, the hydrogen partial pressure pulsates, and the concentration of the hydrogen gas supplied to the fuel cell is low. It becomes uniform and the fuel cell may be deteriorated.

  Therefore, in the present embodiment, when the fuel gas is supplied from the injector 103 (FIG. 1 and the like), the circulation flow rate of the circulation gas pumped by the circulation pump 104 is increased. As an example, FIG. 5 shows the result of increasing the circulation flow rate (Qcir) and setting the circulation flow rate (Qcir) to one time the fuel supply flow rate (Qinj). As shown in FIG. 5, when the circulation flow rate (Qcir) is set to 1 times the fuel supply flow rate (Qinj), the hydrogen partial pressure Gi at the hydrogen gas inlet, the hydrogen partial pressure Ge at the hydrogen gas outlet, and the circulation gas flow path The time during which the hydrogen partial pressure Gc pulsates (time t2 shown in FIG. 5) can be shortened compared to the conventional pulsation time (time t1 shown in FIG. 6) (t2 is one third or less of t1). ). As described above, when the fuel gas is supplied from the injector 103, the circulation gas flowing through the circulation gas flow path 106 and the fuel gas can be promptly increased by increasing the circulation flow rate of the circulation gas pumped by the circulation pump 104. Since they are mixed, the time during which the hydrogen gas concentration is not uniform can be shortened. As a result, deterioration of the fuel cell can be suppressed.

  The embodiments described above are for facilitating the understanding of the present invention, and are not intended to limit the present invention. Each element included in the embodiment and its arrangement, material, condition, shape, size, and the like are not limited to those illustrated, and can be changed as appropriate. In addition, the structures shown in different embodiments can be partially replaced or combined.

DESCRIPTION OF SYMBOLS 100 ... Fuel gas supply system 101 ... Fuel cell 102 ... Fuel supply part 103 ... Injector 104 ... Circulation pump 105 ... Gas-liquid separator 106 ... Circulation gas flow path 107 ... Exhaust drain valve 108 ... Fuel supply flow path 109 ... Discharge flow path 111 ... Hydrogen gas inlet 121 ... Hydrogen gas outlet 150 ... ECU (control part)

Claims (1)

A fuel cell system,
A fuel cell;
An injector for supplying hydrogen gas to the fuel cell;
A circulation gas flow path for connecting a hydrogen gas inlet and a hydrogen gas outlet of the fuel cell, and circulating a circulation gas containing hydrogen gas and nitrogen discharged from the hydrogen gas outlet to the hydrogen gas inlet;
A circulating pump for pumping the circulating gas flowing through the circulating gas flow path;
A hydrogen gas supply amount required for a load required for the fuel cell is calculated, and based on the calculated hydrogen gas supply amount, a hydrogen supply flow rate supplied by driving the injector and a circulation pumped by driving the circulation pump A control unit that calculates a circulating flow rate of gas,
The fuel cell system, wherein the control unit controls driving of the injector and the circulation pump so that the circulation flow rate calculated based on the hydrogen gas supply amount increases to be higher than the hydrogen supply flow rate.