JP4742564B2 - FUEL CELL SYSTEM, ITS CONTROL DEVICE, CONTROL METHOD, AND COMPUTER PROGRAM - Google Patents

Description

  The present invention relates to a fuel cell system that generates water during power generation.

  Conventionally, in order to increase the utilization efficiency of the reaction gas, it has been proposed to recycle off gas discharged from the fuel cell (Patent Document 1). Furthermore, as a technology related to such a recirculation, for example, a technology that suppresses the differential pressure between the electrodes caused by the start and stop of the recirculation blower (Patent Literature 2), and a technology that makes the fuel cell system compact by sharing a pump (Patent Literature) 3) A technology such as a technology for promoting warm-up at startup by recirculation (Patent Document 4) is also disclosed.

JP 2001-266922 A Japanese Patent Laid-Open No. 10-40939 JP 2002-216812 A JP 2002-56771 A

  However, such recirculation may cause problems such as blockage of the supply path and flooding due to phase changes such as condensation and freezing caused by mixing of the recirculated off-gas, particularly when the fuel cell system is started.

  The present invention has been made in order to solve the above-described problems. In the fuel cell system, the present invention provides a technique for suppressing the performance deterioration of the fuel electronic system by suppressing the phase change of the mixed gas caused by the reflux of the reaction gas. The purpose is to provide.

The present invention is a fuel cell system comprising:
A fuel cell;
A gas supply unit capable of supplying a mixed gas in which a reaction gas and an off-gas recirculated from the fuel cell are mixed to the fuel cell;
A state quantity measuring unit that measures a specific state quantity having a correlation with a phase change of moisture contained in the mixed gas;
A control unit for controlling the gas supply unit;
With
The control unit measures the specific state quantity using the state quantity measurement unit, and controls the gas supply unit according to the measured specific state quantity to limit the off-gas flow rate. It is characterized by doing.

  In the fuel cell system of the present invention, a specific state quantity having a correlation with the phase change of moisture contained in the mixed gas is measured, and the off-gas ring flow rate is limited according to the measured specific state quantity. Therefore, it is possible to suppress the blockage caused by the phase change of the moisture in the mixed gas caused by the reflux of the reaction gas and reduce the performance degradation of the fuel electronic system.

  Here, the restriction of the circulation flow rate has a meaning widely including the stop of the circulation flow. In addition, specific state quantities having a correlation with the phase change (condensation and freezing) of moisture contained in the mixed gas include not only the hydrogen gas temperature and off-gas temperature described later, but also the outside air temperature, off-gas humidity, fuel cell Various state quantities such as cooling water temperature are available.

In the fuel cell system, the specific state quantity includes an off-gas temperature that is a temperature of the off-gas,
The state quantity measuring unit measures the off-gas temperature,
The controller may increase the limit as the off-gas temperature is lower,
Alternatively, the specific state quantity includes a reaction gas temperature that is a temperature of the reaction gas,
The state quantity measuring unit measures the reaction gas temperature,
The controller may increase the limit as the reaction gas temperature is lower,
Alternatively, both the off-gas temperature and the reaction gas temperature may be measured.

  Thus, the phase change can be predicted by measuring at least one of the off-gas temperature and the reaction gas temperature. However, if both are measured, it is possible to predict the freezing and aggregation of water with a high possibility, so that highly accurate control can be realized. The phase change can be predicted by using phase change information such as a map and a calculation formula described later.

  In the fuel cell system, the gas supply unit may perform the mixing using an ejector. With this configuration, when mixing is performed using an ejector, blockage of the flow path due to aggregation or freezing that can occur inside the ejector can be effectively suppressed.

  In the fuel cell system, the gas supply unit includes a hydrogen tank for supplying hydrogen gas, and mixes the hydrogen gas supplied from the hydrogen tank with the anode off-gas circulated from the fuel cell, so that the fuel is supplied. You may make it supply to a battery.

  In the anode side supply path, there is a high possibility of freezing due to low temperature hydrogen supplied from a high-pressure hydrogen tank. Therefore, when the present invention is applied to the anode side, there is a remarkable effect.

  In the fuel cell system, the fuel cell may be a polymer electrolyte fuel cell.

  In the solid polymer fuel cell, the operating temperature and the temperature of the supplied reaction gas are low, so that a phase change is likely to occur, and the effect of the present invention becomes remarkable.

  In addition to the fuel cell system described above, the present invention can also be configured as various modes such as a control device and control method for a fuel cell system, and a computer program.

Hereinafter, embodiments of the present invention will be described in the following order based on examples.
A. Configuration of a fuel cell system in an embodiment of the present invention:
B. Variations:

A. Configuration of a fuel cell system in an embodiment of the present invention:
FIG. 1 is a block diagram showing a configuration of a fuel cell system 100 according to an embodiment of the present invention. The fuel cell system 100 includes a fuel cell 10, a mixed gas circulation system 20, an air supply system 30, a hydrogen gas supply system 40, a hydrogen gas temperature measurement unit T1, an off gas temperature measurement unit T2, and a control unit 50. Is provided. The control unit 50 controls the air supply system 30, the hydrogen gas supply system 40, and the mixed gas circulation system 20, and uses the hydrogen gas temperature measurement unit T1 and the off gas temperature measurement unit T2 to control the temperature of hydrogen gas and anode off gas. It can be measured.

  The fuel cell 10 is a solid polymer electrolyte fuel cell having a stack structure in which a plurality of fuel cells (not shown) are stacked. Each fuel cell (not shown) includes a fuel cell air passage 35 and a fuel cell hydrogen passage 25 therein.

  The air supply system 30 is a system for supplying humidified air to the fuel cell air flow path 35. The air supply system 30 includes a blower 31 that sucks outside air, a humidifier 39 that humidifies the sucked air, a humidified air supply pipe 34 that supplies the humidified air to the air flow path 35 in the fuel cell, a fuel And an exhaust pipe 36 for exhausting from the air flow path 35 in the battery.

  The hydrogen gas supply system 40 includes a hydrogen tank 42 that stores hydrogen gas, and a hydrogen valve 41 that controls the supply of hydrogen gas to the mixed gas circulation system 20. The hydrogen valve 41 functions as a regulator that adjusts the amount of hydrogen supplied to the mixed gas circulation system 20.

  The mixed gas circulation system 20 includes an ejector 60, a mixed gas supply pipe 24, an exhaust gas pipe 26, a gas-liquid separator 29, and a purge valve 28. The ejector 60 mixes the hydrogen gas supplied from the hydrogen gas supply system 40 with the anode off gas discharged from the fuel cell 10. The mixed gas supply pipe 24 supplies a mixed gas of hydrogen gas and anode off gas to the hydrogen flow path 25 in the fuel cell. The exhaust gas pipe 26 supplies the mixed gas discharged from the hydrogen flow path 25 in the fuel cell to the gas-liquid separator 29. The gas-liquid separator 29 separates water from the anode off gas and supplies it to the purge valve 28. The purge valve 28 is a valve for discharging a part of the anode off gas from the mixed gas circulation system 20 to the outside.

  The hydrogen gas temperature measurement unit T1 is used for temperature measurement of hydrogen gas supplied from the hydrogen gas supply system 40. The off gas temperature measuring unit T2 is used for measuring the temperature of the anode off gas. In this embodiment, the hydrogen gas supply system 40 and the mixed gas circulation system 20 correspond to the “gas supply unit” in the claims, and the hydrogen gas corresponds to the “reaction gas” in the claims. .

  FIG. 2 is an explanatory diagram showing the internal structure of the ejector 60 in the embodiment of the present invention. The ejector 60 adjusts the opening amount of the housing 61 having the anode off-gas intake port 61Pin and the mixed gas exhaust port 61Pout, the nozzle portion 62 having the hydrogen gas intake port 62P and the nozzle opening 62N, and the nozzle opening 62N. A needle 63, a spring 64 that biases the needle 63, and an actuator 70 that drives the needle 63 are provided.

  The ejector 60 mixes the hydrogen gas supplied from the hydrogen gas supply system 40 with the anode off gas supplied from the gas-liquid separator 29. This mixing is performed by sucking the anode off gas supplied from the gas-liquid separator 29 into the high-speed flow of hydrogen gas discharged from the nozzle opening 62N at high speed. This suction is caused by a decrease in the pressure potential energy of the hydrogen gas discharged at high speed from the nozzle opening 62N. This decrease in pressure potential energy is due to an increase in the kinetic energy of the hydrogen gas flow and the energy conservation law (Bernoulli's theorem) in the flow field.

  The ejector 60 adjusts the negative pressure by manipulating the flow rate of the hydrogen gas whose flow rate is adjusted by the hydrogen valve 41, thereby adjusting the suction amount of the anode off gas. Adjustment of the flow rate of hydrogen gas is realized by driving the needle 63 with the actuator 70 and adjusting the opening amount of the nozzle opening 62N. When the opening amount of the nozzle opening 62N is fully opened, the ejector 60 is configured such that the negative pressure disappears due to a decrease in the flow rate of the hydrogen gas and the suction amount of the anode off gas becomes zero.

  FIG. 3 is an explanatory diagram showing the contents of the ejector control map M stored in the control unit 50. In this map M, the vertical axis and the horizontal axis indicate the temperature of the anode off gas and the temperature of the hydrogen gas supplied to the ejector 60, respectively. In the present embodiment, the control law of the ejector 60 is that points on the map M corresponding to the measurement value of the hydrogen gas temperature measurement unit T1 and the measurement value of the off-gas temperature measurement unit T2 are point Hth, point Ath, and point Cth. When the frozen region (hatched region) surrounded by the three points is entered, the opening amount of the nozzle opening 62N is determined to be fully opened.

  The freezing region is a temperature region in which water may be frozen inside the mixed gas circulation system 20 such as the ejector 60 or the hydrogen flow path 25 in the fuel cell and a clogged state may occur. This temperature region can be set based on performance test, operation test, and other test data.

  The reason why such a control law is set is to suppress freezing of water inside the mixed gas circulation system 20. Such freezing of water is caused by mixing low-temperature hydrogen gas and anode off-gas containing moisture in the ejector 60. The reason for the low temperature of the hydrogen gas is that the high-pressure hydrogen gas in the hydrogen tank 42 is supplied to the ejector 60 through the expansion process, and the anode off gas contains water because the gas-liquid separation unit 29 completely separates the water. Because it is not.

  Thus, in this embodiment, when these temperatures enter the freezing region according to the temperature of the anode off gas and the temperature of the hydrogen gas supplied to the ejector 60, the nozzle opening 62N of the ejector 60 is The opening amount is set to the fully open state, and the suction amount of the anode off gas is set to zero. As a result, since mixing does not occur, it is possible to suppress the possibility of occurrence of a clogged state due to freezing that occurs inside the mixed gas circulation system 20.

B. Variations:
As mentioned above, although several embodiment of this invention was described, this invention is not limited to such embodiment at all, and implementation in various aspects is possible within the range which does not deviate from the summary. It is. For example, the following modifications are possible.

B-1. In the above embodiment, the mixing is stopped when the temperature of the anode off gas and the temperature of the hydrogen gas enter the freezing region. You may comprise so that it may decrease. By so doing, it is possible to suppress clogging in the anode-side flow path without excessively reducing a favorable effect (for example, increase in utilization efficiency of hydrogen gas) due to the reflux.

B-2. In the above embodiment, the anode off gas and the hydrogen gas are mixed using the ejector, but the anode off gas inside the anode side flow path is forcibly circulated by the circulation pump 71 as in the modification shown in FIG. The present invention can also be applied to such a configuration. In this case, when the temperature of the anode off gas and the temperature of the hydrogen gas enter the freezing region, the circulation pump 71 may be stopped and controlled so as not to mix. Further, in the embodiment of FIG. 1, for example, a shutoff valve or an adjustment valve may be provided between the ejector 60 and the gas-liquid separation unit 90 to limit the circulation.

B-3. In the above embodiment, clogging due to freezing inside the anode side flow path is suppressed, but not only water freezing but also condensation causes flooding and clogging, which causes performance degradation of the fuel cell system. The phase change of moisture from gas to liquid including condensation as well as freezing may be suppressed.

B-4. In the above embodiment, the hydrogen gas temperature and the anode off gas temperature are used as specific state quantities having a correlation with the phase change (condensation or freezing) of the moisture contained in the mixed gas. The occurrence of a phase change can be predicted with only one of the temperatures. Furthermore, not only the hydrogen gas temperature and anode off-gas temperature, but also various state quantities such as outside air temperature, off-gas humidity, and fuel cell cooling water temperature are correlated with the phase change (condensation and freezing) of the water contained in the mixed gas. It can be used as a specific state quantity having

  However, since this phase change is caused by the mixing of hydrogen gas and anode off gas, the use of the hydrogen gas temperature and anode off gas temperature as specific state quantities has the advantage that the occurrence of phase change can be accurately estimated. .

B-5. In the above embodiment, the present invention is applied to the anode-side flow path. However, the present invention may be applied to the cathode-side flow path, or may be applied to both flow paths. . For example, in a cold region, there is a possibility that freezing may occur in the flow path on the cathode side. However, since there is a high possibility of freezing on the anode side by low-temperature hydrogen supplied from a high-pressure hydrogen tank, when the present invention is applied to the anode side, there is a remarkable effect.

The block diagram which shows the structure of the fuel cell system 100 in the Example of this invention. Explanatory drawing which shows the internal structure of the ejector 60 in the Example of this invention. Explanatory drawing which shows the content of the map M for ejector control which the control part 50 stores. The block diagram which shows the structure of the fuel cell system 100 in the modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 20 ... Mixed gas circulation system 24 ... Mixed gas supply piping 25 ... Hydrogen flow path in fuel cell 26 ... Exhaust gas piping 28 ... Purge valve 29 ... Gas-liquid separation part 30 ... Air supply system 31 ... Blower 34 ... Humidified air Supply pipe 35 ... Air flow path in fuel cell 36 ... Exhaust pipe 39 ... Humidifier 40 ... Hydrogen gas supply system 41 ... Hydrogen valve 42 ... Hydrogen tank 50 ... Control unit 60 ... Ejector 61 ... Housing 61Pin ... Anode off gas intake port 62 ... Nozzle part 62N ... Nozzle opening 62P ... Hydrogen gas intake port 63 ... Needle 64 ... Spring 70 ... Actuator 71 ... Circulation pump 100 ... Fuel cell system T1 ... Hydrogen gas temperature measurement part T2 ... Off gas temperature measurement part

Claims (10)

A fuel cell system,
A fuel cell;
A gas supply unit capable of supplying a mixed gas in which a reaction gas and an off-gas recirculated from the fuel cell are mixed to the fuel cell;
A state quantity measuring unit that measures a specific state quantity having a correlation with a phase change of moisture contained in the mixed gas;
A control unit for controlling the gas supply unit;
With
When the control unit measures the specific state quantity using the state quantity measurement unit, and the measured specific state quantity indicates the possibility of a phase change of moisture contained in the mixed gas, A fuel cell system, wherein the gas supply unit is controlled to limit a ring flow rate of the off gas.   The fuel cell system according to claim 1, wherein
  The control unit stores in advance a range of the specific state quantity in which moisture contained in the mixed gas may freeze due to a phase change;
  The said control part is a fuel cell system which stops the recirculation | reflux of the said off gas, when the measured said specific state quantity is contained in the said range. The fuel cell system according to claim 1, wherein
The specific state quantity includes an off-gas temperature that is a temperature of the off-gas,
The state quantity measuring unit measures the off-gas temperature,
The control unit increases the limit as the off-gas temperature is lower. The fuel cell system according to claim 1 or 3 ,
The specific state quantity includes a reaction gas temperature that is a temperature of the reaction gas,
The state quantity measuring unit measures the reaction gas temperature,
The said control part is a fuel cell system which enlarges the said limit, so that the said reaction gas temperature is low. The fuel cell system according to any one of claims 1 to 4 ,
The gas supply unit is a fuel cell system that performs the mixing using an ejector. A fuel cell system according to any one of claims 1 to 5 ,
The gas supply unit includes a hydrogen tank for supplying hydrogen gas, and mixes the hydrogen gas supplied from the hydrogen tank and the anode off-gas circulated from the fuel cell, and supplies the fuel cell to the fuel. Battery system. The fuel cell system according to any one of claims 1 to 6 ,
The fuel cell is a solid polymer fuel cell, a fuel cell system. A control device for a fuel cell system,
The fuel cell system includes a fuel cell, a gas supply unit capable of supplying a mixed gas in which a reaction gas and an off-gas recirculated from the fuel cell are mixed to the fuel cell, and the mixed gas. A state quantity measuring unit that measures a specific quantity of state having a correlation with the phase change of moisture,
The controller is
(A) a function of measuring the specific state quantity using the state quantity measurement unit;
(B) When the measured specific state quantity indicates the possibility of a phase change of moisture contained in the mixed gas, the function of controlling the gas supply unit to limit the off-gas ring flow rate;
A control apparatus for a fuel cell system, comprising: A control method for a fuel cell system, comprising:
(A) a fuel cell, a gas supply unit capable of supplying the fuel cell with a mixed gas in which a reaction gas and an off-gas recirculated from the fuel cell are mixed, and a phase of moisture contained in the mixed gas A step of preparing a state quantity measuring unit that measures a specific state quantity having a correlation with the change;
(B) a step of measuring the specific state quantity using the state quantity measurement unit;
(C) when the measured specific state quantity indicates the possibility of a phase change of the moisture contained in the mixed gas, the step of controlling the gas supply unit to limit the flow rate of the off gas;
A control method for a fuel cell system, comprising: A computer program for causing a computer to execute control of a fuel cell system,
The fuel cell system includes a fuel cell, a gas supply unit capable of supplying a mixed gas in which a reaction gas and an off-gas recirculated from the fuel cell are mixed to the fuel cell, and the mixed gas. A state quantity measuring unit that measures a specific quantity of state having a correlation with the phase change of moisture,
The computer program is
A function of measuring the specific state quantity using the state quantity measurement unit;
When the measured specific state quantity indicates the possibility of a phase change of moisture contained in the mixed gas, the function of controlling the gas supply unit and limiting the off-gas flow rate;
A computer program comprising a program for causing the computer to realize the above.

Images