WO2004045004A2 - Fuel cell system and related method - Google Patents
Fuel cell system and related method Download PDFInfo
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- WO2004045004A2 WO2004045004A2 PCT/JP2003/013564 JP0313564W WO2004045004A2 WO 2004045004 A2 WO2004045004 A2 WO 2004045004A2 JP 0313564 W JP0313564 W JP 0313564W WO 2004045004 A2 WO2004045004 A2 WO 2004045004A2
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- gas
- anode
- fuel cell
- combustor
- cathode
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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
- H01M8/04231—Purging of the reactants
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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
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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
- H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
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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
- H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
- H01M8/04014—Heat exchange using gaseous fluids; Heat exchange by combustion of reactants
- H01M8/04022—Heating by combustion
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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
- H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
- H01M8/04029—Heat exchange using liquids
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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
- H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
- H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
- H01M8/04097—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with recycling of the reactants
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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
- H01M8/04268—Heating of fuel cells during the start-up of the fuel cells
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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
- H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
- H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
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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
- H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
- H01M8/0662—Treatment of gaseous reactants or gaseous residues, e.g. cleaning
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Definitions
- This invention relates to fuel cell systems and, more particularly, to a fuel cell system, that provides improved temperature control of a combustor for combusting anode off-gas, and a related method.
- a fuel sell system fuel gas such as hydrogen and oxidant gas containing oxygen electrochemically react each other via electrolyte to take out an electric energy from electrodes disposed on both sides of an electrolyte.
- a solid polymer fuel cell employing a solid electrolyte attracts public attention as an electric power supply for an electric vehicle because of a low operating temperature and ease of handling.
- a fuel cell powered vehicle is an ultimate clean vehicle with only water remaining as emission matter.
- This vehicle install a hydrogen absorbing device, such as a high pressure hydrogen tank, a liquid hydrogen tank, and a hydrogen absorbing amorphous alloy tank. Hydrogen supplied from the hydrogen absorbing device and air including oxygen are delivered to the fuel cell to accomplish reaction for taking out the electric energy from the fuel cell to drive a motor connected to drive wheels.
- the solid polymer fuel cell includes an anode off-gas recirculation type that anode off-gas containing non-reacted hydrogen gas discharged from an anode outlet is recirculated to the anode inlet.
- This type fuel cell includes an anode (fuel electrode) inlet supplied with hydrogen at a larger flow rate than that of hydrogen consumed in electrochemical reaction with anode off-gas.
- the fuel cell system includes a fuel reformer formed with a combustion chamber into which portions of anode off-gas and cathode off-gas are introduced and combusted; an air compressor driven with a cathode exhaust gas turbine; and a low temperature blower that allows air, together with air delivered from the air compressor, to be drawn into the combustion chamber.
- this fuel cell system includes a controller provided for outputting a rotating speed command to the low temperature blower while outputting an opening-degree correction command to a reformer-combustion-air flow-rate regulator valve, based on an output command related to the fuel cell, an oxygen concentration of combustion exhaust gas, and an outlet temperature of the combustor. If the outlet temperature of the combustion chamber exceeds an upper limit, the controller controls the opening degree of the reformer-combustion-air flow-rate regulator valve to be increased and the rotating speed of the low temperature blower to be increased in dependence on the resulting opening degree for increasing the flow rate of air to be supplied to the combustion chamber of the reformer to lower the temperature of the combustion chamber.
- the above-described technology has a structure wherein if a detected value of a combustion chamber outlet temperature exceeds a temperature upper limit value, an air flow rate is increased to lower the temperature of the combustion chamber. Therefore, when intermittent and short-term combustion is performed in the combustion chamber, the temperature rise in the outlet gas temperature decreases due to a thermal capacity present in the combustion chamber. Thus, since the combustion temperature exceeding the temperature upper limit value is unable to be detected, as a result performance of the combustion chamber is degraded.
- an aspect of the present invention is a fuel cell system which comprises a fuel gas supply unit supplying fuel gas, an oxidant gas supply unit supplying oxidant gas, a fuel cell stack generating electric power using the fuel gas and the oxidant gas, an anode off-gas recirculation unit recirculating anode off-gas, discharged from an anode of the fuel cell stack, to the anode, a purging unit temporarily discharging the anode off-gas from the anode off-gas recirculation unit to an outside thereof, a combustor combusting at least the anode off-gas, discharged from the purging unit, and the oxidant gas or cathode off-gas discharged from a cathode of the fuel cell stack, and a system controller operative to perform system control such that when permitting the purging unit to discharge the anode off-gas to the combustor, a combustion temperature of the combustor does not exceed a given temperature.
- a method of controlling a fuel cell system comprises preparing a fuel gas supply unit supplying fuel gas, an oxidant gas supply unit supplying oxidant gas, a fuel cell stack generating electric power using the fuel gas and the oxidant gas, a combustor combusting at least anode off-gas, discharged from an anode off-gas and the oxidant gas or cathode off-gas, discharged from a cathode of the fuel cell stack, discharging anode off-gas from the anode of the fuel cell stack, recirculating the anode off-gas, discharged from an air supply unit or the anode of the fuel cell stack, to the anode, combusting at least the anode off-gas, discharged from the anode of the fuel cell stack, and the oxidant gas or cathode off-gas discharged from the cathode of the fuel cell stack, and executing system control such that when permitting the anode
- Fig. 1 is a system structural view illustrating a structure of a first embodiment of a fuel cell system according to the present invention.
- Figs. 2A to 2E are time charts illustrating combustion temperature control of the first embodiment, with Fig. 2A showing a combustion temperature Te of a combustor 7, Fig. 2B showing a flow rate of air supplied from an air supply unit 2, Fig. 2C showing a discharge rate of cathode off-gas, Fig. 2D showing a flow rate of hydrogen supplied from a hydrogen supply unit 1 and Fig. 2E showing a discharge rate of anode off-gas.
- Fig. 3 is a flowchart illustrating a control content of a system controller forming part of the first embodiment.
- Fig. 4 is a system structural view illustrating a structure of a second embodiment of a fuel cell system according to the present invention.
- Figs. 5A to 5E are time charts illustrating combustion temperature control of the second embodiment, with Fig. 5A showing the combustion temperature Te of the combustor 7, Fig. 5B showing the flow rate of air supplied from the air supply unit 2, Fig. 5C showing the discharge rate of cathode off-gas, Fig. 5D showing the flow rate of hydrogen supplied from the hydrogen supply unit 1 and Fig. 5E showing the discharge rate of anode off-gas.
- Fig. 6 is a flowchart illustrating a control content of a system controller forming part of the second embodiment.
- Fig. 7 is a system structural view illustrating a structure of a third embodiment of a fuel cell system according to the present invention.
- Figs. 8A to 8E are time charts illustrating combustion temperature control of the third embodiment, with Fig. 8A showing the combustion temperature Te of the combustor 7, Fig. 8B showing the flow rate of air supplied from an auxiliary air supply unit 28, Fig. 8C showing the discharge rate of cathode off-gas, Fig. 8D showing the flow rate of hydrogen supplied from the hydrogen supply unit 1 and Fig. 8E showing the discharge rate of anode off-gas.
- Fig. 9 is a flowchart illustrating a control content of a system controller forming part of the third embodiment.
- Figs. 10A to 10D are time charts illustrating combustion temperature control of a fourth embodiment, with Fig. 10A showing the combustion temperature Te of the combustor 7, Fig. 10B showing the discharge rate of cathode off-gas, Fig. 10C showing the flow rate of hydrogen supplied from the hydrogen supply unit 1 and Fig. 10D showing the discharge rate of anode off-gas.
- Fig. 11 is a flowchart illustrating a control content of a system controller forming part of a fourth embodiment.
- Figs. 12A to 12E are time charts illustrating combustion temperature control of a fifth embodiment, with Fig. 12A showing the combustion temperature Te of the combustor 7, Fig. 12B showing the flow rate of air supplied from the air supply unit 2, Fig. 12C showing the discharge rate of cathode off-gas, Fig. 12D showing the flow rate of hydrogen supplied from the hydrogen supply unit 1 and Fig. 12E showing the discharge rate of anode off-gas.
- Fig. 13 is a flowchart illustrating a control content of a system controller forming part of a fifth embodiment.
- Fig. 14 is a system structural view illustrating a structure of a sixth embodiment of a fuel cell system according to the present invention.
- Figs. 15A to 15E are time charts illustrating combustion temperature control of the sixth embodiment, with Fig. 15A showing the combustion temperature Te of the combustor 7, Fig. 15B showing the supply rate of water, Fig. 15C showing the discharge rate of cathode off-gas, Fig. 15D showing the supply rate of hydrogen supplied from the hydrogen supply unit 1 and Fig. 15E showing the discharge rate of anode off-gas.
- Fig. 16 is a flowchart illustrating a control content of a system controller forming part of the sixth embodiment.
- Fig. 17 is a view illustrating an example of a combustion temperature prediction map in terms of an operating condition of a fuel cell.
- Figs. 18A to 18E are time charts illustrating combustion temperature control of a seventh embodiment, with Fig. 18A showing the combustion temperature Te of the combustor 7, Fig. 18B showing the flow rate of air supplied from the air supply unit 2, Fig. 18C showing the discharge rate of cathode off-gas, Fig. 18D showing the flow rate of hydrogen supplied from the hydrogen supply unit 1 and Fig. 18E showing the discharge rate of anode off-gas.
- Fig. 19 is a flowchart illustrating a control content of a system controller forming part of the seventh embodiment.
- Fig. 20 is a view illustrating table data for calculating a voltage threshold value for judgment to find whether to execute purging of anode off-gas in the seventh embodiment.
- Fig. 21 is a view illustrating table data for calculating the voltage threshold value for judgment to find whether to execute purging of anode off-gas in the seventh embodiment.
- Fig. 22 is a view illustrating table data for calculating the variation rate of the air flow rate in the seventh embodiment.
- Fig. 23 is a view illustrating table data for calculating the variation rate of the air flow rate in the seventh embodiment.
- Fig. 24 is a view illustrating table data for calculating the variation rate of the air flow rate in the seventh embodiment.
- a first embodiment of a fuel cell system according to the present invention is described in detail below.
- Fig. 1 is a system structural view illustrating a structure of the first embodiment.
- the fuel cell system is comprised of a hydrogen supply unit (fuel gas supply unit) 1 that supplies hydrogen as fuel gas; an air supply unit (oxidant gas supply unit) 2 that supplies air as oxidant gas; a fuel cell stack 3 that includes electrodes, such as an anode 4 and a cathode 5, which are supplied with hydrogen and air, respectively, to generate electric power; an anode off-gas recirculation unit 6 that allows anode off-gas to be recirculated to an upstream side of the anode 4 via an anode off-gas recirculation conduit 12; a coolant heat exchanger 8 that heats coolant with combustion exhaust gas of a combustor 7 during start-up; a coolant cooling unit 9; a humidifier 10 that allows hydrogen and air to be humidified, an air flow control valve 16; a coolant pump 21 operative to circulate coolant between the heat exchanger 8 or the coolant cooling unit and the fuel
- phase to allow anode off-gas to be temporarily discharged from the anode off-gas recirculation unit 6 to the combustor 7 is termed "purging" .
- the combustor 7 is constructed of a mixer 23 for mixing hydrogen or anode off-gas supplied with air or cathode off-gas to form uniformly mixed gas, and a combustor 24 carrying a combustion catalyst to combust mixed gas.
- a temperature detector 29e Located in the combustion chamber 24 is a temperature detector 29e, and information of resulting detected temperature is delivered to the system controller 37 through a signal line, which is not shown.
- the combustor 7 is supplied with hydrogen through the anode off-gas discharge valve 27, air from the air supply unit 2 through the air flow control valve 16, and cathode off-gas via a cathode off-gas exhaust conduit 15. These gasses are mixed in the mixer 23, with mixed gas being combusted with the combustion catalyst 24.
- the combustion gas resulting from the combustor 7 during start-up of the fuel cell system is used in the coolant heat exchanger 8 for heat exchange with coolant to raise a coolant temperature to an operating temperature. Subsequently, resulting exhaust gas is expelled through an exhaust conduit 19 to the outside of the system.
- condensed water is recovered from the exhaust conduit 19 and stored in a pure water tank 25.
- the pure water stored in the pure water tank 25 is supplied through a pure water conduit 26 to the humidifier 10 by a pure water pump 35.
- the humidifier 10 uses this pure water to humidify hydrogen and air to be supplied to the fuel cell stack 3.
- the temperature of the fuel cell stack 3 is managed through coolant, such as antifreeze mixture, such that the operating temperature is maintained at an appropriate temperature.
- coolant such as antifreeze mixture
- the three-way valve 22 permits the coolant pump 21 and the coolant cooling unit 9 to communicate one another, thereby allowing coolant to circulate through a closed circuit comprised of the coolant pump 21, the three-way valve 22, the coolant cooling unit 9, the fuel cell stack 3, and the coolant pump 21. This allows heat buildup of the fuel cell stack 3 to be discharged from the coolant cooling unit 9 to the outside of the system, thereby maintaining the temperature of the fuel cell stack 3 at the appropriate temperature.
- the three-way valve 22 permits the coolant pump 21 and the coolant heat exchanger 8 to communicate one another, thereby allowing coolant to circulate through a closed circuit comprised of the coolant pump 21, the three-way valve 22, the coolant heat exchanger 8, the fuel cell stack 3, and the coolant pump 21.
- This allows the coolant temperature to develop in the coolant heat exchanger 8, thereby enabling the temperature of the fuel cell stack 3 to be raised to the temperature appropriate for commencing operation.
- the system controller 37 serves as a system control means that controls the system to prevent the combustion temperature of the combustor 7 from exceeding a given temperature when anode off-gas is discharged to the combustor 7 through the anode off-gas discharge valve 27.
- the system controller 37 are connected to the air flow meter 32, the hydrogen flow meter 33, the temperature detectors 29a to 29g, the pressure detectors 30a to 30d, the humidity detectors 31a and 31b, and the voltage detector means 36.
- the system controller 37 is able to be applied with the flow rate, temperature and pressure of air supplied from the air supply unit 2, the flow rate, temperature and pressure of hydrogen supplied from the hydrogen supply unit 1, the temperature, pressure and humidity of cathode off-gas expelled from the cathode 5, and the temperature, pressure and humidity of anode off-gas expelled from the anode 4, respectively.
- the voltage detector means 36 detects voltages of respective unit cells or voltages of respective groups, each formed of a plurality of unit cells, that form the fuel cell stack 3, with resulting voltage values being outputted to the system controller 37.
- the system controller 37 is applied with the detection signals delivered from the above units and an electric-power-generation load command signal. By using these signals, the system controller 37 controls the hydrogen supply unit 1, the air supply unit 2, the anode off-gas recirculation unit 6, the coolant pump 21, the pure water pump 35, the air flow control valve 16, the three-way valve 22 and the anode off-gas discharge valve 27 for thereby controlling the flow rates of hydrogen and air to be supplied to the fuel cell stack 3 and the temperature of the fuel cell stack 3.
- the system controller 37 executes control such that when permitting anode off-gas to be discharged to the combustor 7 through the anode off-gas discharge valve 27, the combustion temperature of the combustor 7 does not exceed the given temperature.
- the system controller 37 is comprised of a microcomputer that includes a CPU, a memory and I/O interfaces. Now, a basic sequence of operations of the fuel cell system is described as bellow. The anode 4 and the cathode 5 are supplied with hydrogen and air from the hydrogen supply unit 1 and the air supply unit 2, respectively. Then, electric power is generated by reacting hydrogen and air in the fuel cell stack 3.
- anode off-gas is recirculated through the anode off-gas recirculation conduit 12 to the hydrogen supply conduit 11 by means of the anode off-gas recirculation unit 6. Then, the whole of the anode off-gas is supplied to the anode 4 again.
- the cathode off-gas is supplied to the combustor 7 and, thereafter, expelled through the coolant heat exchanger 8 and the exhaust conduit 19 to the outside of the system.
- the voltage detector means 36 that detects the cell voltages of the fuel cell stack 3 detects a voltage lower than a given voltage value
- anode off-gas is discharged to the combustor 7 at a given flow rate from the anode off-gas discharge valve 27 in response to a purge signal delivered from the system controller 37.
- the flow rate of hydrogen supplied from the hydrogen supply unit 1 is increased by substantially the same flow rate as that of anode off-gas being discharged while the pressure of hydrogen to be supplied is kept constant.
- gas compositions, even containing steam, of cathode off-gas, and an enthalpy of cathode off-gas are calculated in dependence on the air flow rate detected by the air flow meter 32, the hydrogen flow rate detected by the hydrogen flow meter 33, the cathode off-gas temperature detected by the temperature detector 29c, the cathode off-gas pressure detected by the pressure detector 30a, and the cathode off-gas humidity detected by the humidity detector 31a.
- the composition of anode off-gas discharged from the anode off-gas recirculation unit 6 is formed of only hydrogen.
- the enthalpy of anode off-gas is calculated in dependence on a predetermined anode off-gas discharge rate and the temperature of anode off-gas detected by the temperature detector 29d.
- a predicted value of the combustion temperature in the combustor 7 is calculated.
- One example of a calculation method is indicated below.
- the enthalpy (unit: KJ/mol) per one mol of each gas composition is expressed in the following formula as a function of an absolute temperature T (unit: K):
- Huc/100 Huc/100
- Huh2o(Tc) is the saturated steam pressure (KPa) at the temperature Tc.
- the enthalpy HC of cathode off-gas per unit time and the enthalpy HA of anode off-gas per unit time are expressed by the following formulae based on the formulae (1), (2), (3) and (4):
- HC(Tc) Ho2(Tc) x QCo2 + Hn2(Tc) x QCn2 + Hh2o(Tc) x Qh2o
- HE(Te) Ho2(Te) X QEo2 + Hn2(Te) X QEn2 + Hh2o(Te) X QEh2o
- anode off-gas originally includes nitrogen and water which are diffused in areas covering the cathode 5 and the anode 4 via an electrolyte membrane, a hydrogen concentration increases whereas inversely, an impurity concentration decreases as purging of anode off-gas proceeds.
- control may also be executed by obtaining the enthalpy for each gas component and calculating the combustion temperature even for anode off-gas.
- a predicted value of the combustion temperature as a result of calculation is less than a predetermined upper limit value, no flow conditions are altered.
- the predicted value of the combustion temperature exceeds the upper limit value, for the purpose of permitting the combustion temperature to be less than the upper limit value, the amount of air to be supplied to the combustor 7 through the fuel cell stack 3 is increased, thereby performing control such that the combustion temperature is restricted to a value below the upper limit value.
- Figs. 2A to 2E are flowcharts for illustrating combustion temperature control in the first embodiment, with Fig. 2A showing the combustion temperature Te of the combustor 7, Fig. 2B showing the flow rate of air to be supplied from the air supply unit 2, Fig. 2C showing the discharge rate of cathode off-gas, Fig. 2D showing the flow rate of hydrogen to be supplied from the hydrogen supply unit 1 and Fig. 2E showing the discharge rate of anode off-gas.
- Figs. 2A showing the combustion temperature Te of the combustor 7
- Fig. 2B showing the flow rate of air to be supplied from the air supply unit 2
- Fig. 2C showing the discharge rate of cathode off-gas
- Fig. 2D showing the flow rate of hydrogen to be supplied from the hydrogen supply unit 1
- Fig. 2E showing the discharge rate of anode off-gas.
- Fig. 3 is a flowchart for illustrating a control function of the system controller in the first embodiment.
- step (hereinafter abbreviated as "S") 10 the cell voltage of the fuel cell stack 3 is detected by the voltage detector means 36, and judgment is made to find whether the cell voltage is less than the given value. If the voltage for each unit cell or the voltage for each group of the unit cells detected by the voltage detector means 36 drop below the given value, operation is routed to S12. If these voltages exceed the given value, then operation is routed back to S10, thereby repeatedly executing detection of the cell voltages and judgment thereof.
- the combustion temperature Te is calculated for predicting the combustion temperature resulting when discharging anode off-gas, upon purging operation to recover the cell voltage, to the combustor 7. The predicted value of this combustion temperature Te is calculated, based on the enthalpy calculation for gases flowing into or flowing out from the combustor 7, using the above formulae (1) to (15).
- the flow rate Qair of air to be increased is calculated.
- the flow rate Qair of air to be increased can be obtained based on the enthalpy calculation where when taking a view in a sense of short term, no variations are regarded to take place in the temperature Tc and the relative humidity Hue of cathode off-gas.
- a purge command is transmitted from the system controller 37 to the air supply unit 2, the anode off-gas discharge valve 27 and the hydrogen supply unit 1.
- the air supply unit 2 increases the flow rate of air to be supplied to the cathode 5 while, in S24, the anode off-gas discharge valve 27 is opened and, in S26, the hydrogen supply unit 1 increases the flow rate of hydrogen to be supplied to the anode 4.
- judgment is made to find whether the given time interval Tp has elapsed from the commencement of purging and, if not, operation is routed back to S28. If the given time interval Tp has elapsed from the commencement of purging, operation is routed to S30.
- the increment in the flow rate of hydrogen to be supplied from the hydrogen supply unit 1 is interrupted and, in S32, the anode off-gas discharge valve 27 is closed while, in S34, interrupting the increment of the flow rate of air to be supplied from the air supply unit 2.
- S40 a process is begun to discharge anode off-gas under the given condition.
- the purge command is transmitted from the system controller 37 to the anode off-gas discharge valve 27 and the hydrogen supply unit 1.
- the anode off-gas discharge valve 27 is opened and, in S46, the hydrogen supply unit 1 increases the flow rate of hydrogen to be supplied to the anode 4.
- consecutive S48 judgment is made to find whether the given time interval Tp has elapsed from the commencement of purging and, if not, operation is routed back to S48. If the given time interval Tp has elapsed from the commencement of purging, operation is routed to S50.
- S50 the increment in the flow rate of hydrogen to be supplied from the hydrogen supply unit 1 is interrupted and, in S52, the anode off-gas discharge valve 27 is closed. This allows the fuel cell system to be returned to the normal operating condition.
- the system is controlled so as to preclude the combustion temperature from exceeding the given temperature in the presence of a probability where the combustion temperature exceeds the given temperature whereby even if a discrepancy occurs between the combustor inlet temperature and the combustor outlet temperature as a result of combustion being accomplished only for a short time period, excessive temperature rise is restricted in the combustor as a whole to suppress degradation in performance of the combustor due to the excessive thermal load.
- Fig. 4 is a system structural view illustrating a structure of the second embodiment.
- the fuel cell system is constructed such that an air flow control valve 17 and an air supply conduit 18 are additionally located between the air supply unit 2 and the combustor 7 to enable a portion of air supplied from the air supply unit 2 to be branched off and directly supplied to the combustor 7.
- the second embodiment is similar in other structure to that of the first embodiment shown in Fig. 1 and, so, like component parts bear the same reference numerals as those of the first embodiment for omitting duplicated description.
- the presently filed embodiment is enabled to directly supply air from the air supply unit 2 to the combustor 7 through the air flow control valve 17 without intervening the fuel cell stack 3, an improved quick response for increasing the flow rate of air to be supplied to the combustor 7 is resulted, thereby more accurately limiting a rise in the combustion temperature.
- a demanded flow rate of air to be increased is conducted in the same way as that of the first embodiment except for that the temperature Tair(K), detected by the temperature detector 29a which detects the temperature of air to be supplied from the air supply unit 2, is used in place of Tc(K) as the temperature of air to be increased and that since air to be increased is directly supplied to the combustor 7 without intervening the fuel cell stack 3, no consideration is taken for the flow rate of steam to be increased accompanied by the air increase.
- Hair(Tair) Qair X 0.21 X Ho2(Tair) + Qair X 0.79 X Hn2(Tair)
- HE(Te)* Ho2(Te) X QEo2' + Hn2(Te) X QEn2' + Hh2o(Te) X QEh2o
- Figs. 5A to 5E are flowcharts for illustrating combustion temperature control in the second embodiment, with Fig. 5A showing the combustion temperature Te of the combustor 7, Fig. 5B showing the flow rate of air to be supplied from the air supply unit 2, Fig. 5C showing the discharge rate of cathode off-gas, Fig. 5D showing the flow rate of hydrogen to be supplied from the hydrogen supply unit 1 and Fig. 5E showing the discharge rate of anode off-gas.
- Fig. 6 is a flowchart for illustrating a control function of the system controller of the second embodiment.
- the cell voltage of the fuel cell stack 3 is detected by the voltage detector means 36, and judgment is made to find whether the cell voltage is less than the given value. If the voltage for each unit cell or the voltage for each group of the unit cells detected by the voltage detector means 36 drop below the given value, operation is routed to S12. If these voltages exceed the given value, then operation is routed back to S10, thereby repeatedly executing detection of the cell voltages and judgment thereof.
- the combustion temperature Te is calculated for predicting the combustion temperature resulting when discharging anode off-gas, upon purging operation to recover the cell voltage, to the combustor 7. The predicted value of this combustion temperature Te is calculated, based on the enthalpy calculation for gases flowing into or flowing out from the combustor 7, using the above formulae (1) to (15).
- the flow rate Qair of air to be increased is calculated.
- the flow rate Qair of air to be increased can be obtained based on the enthalpy calculation where when taking a view in a sense of short term, no variations are regarded to take place in the temperature Tc and the relative humidity Hue of cathode off-gas.
- a purge command is transmitted from the system controller 37 to the air supply unit 2, the flow rate control valves 16, 17, the anode off-gas discharge valve 27 and the hydrogen supply unit 1.
- the air supply unit 2 increases the flow rate of air to be supplied to the cathode 5 and, in S21, the opening degree of the air flow rate control valve 16 by which air is supplied to the cathode 5 while opening the air flow control valve 17 through which air is directly supplied from the air supply unit 2 to the combustor 7.
- the anode off-gas discharge valve 27 is opened while, in S26, the hydrogen supply unit 1 increases the flow rate of hydrogen to be supplied to the anode 4.
- the system is controlled so as to preclude the combustion temperature from exceeding the given temperature in the presence of a probability where the combustion temperature exceeds the given temperature whereby even if a discrepancy occurs between the combustor inlet temperature and the combustor outlet temperature as a result of combustion being accomplished only for a short time period, excessive temperature rise is restricted in the combustor as a whole to suppress degradation in performance of the combustor due to the excessive thermal load.
- Fig. 7 is a system structural view illustrating a structure of the third embodiment.
- the third embodiment contemplates to further include, in addition to the component elements of the first embodiment shown in Fig. 1, an auxiliary air supply unit 28 that supplies auxiliary air specific for the combustor 7, an auxiliary air flow meter 38 that measures the flow rate of auxiliary air, and a temperature detector 29h that detects the temperature of auxiliary air to be supplied from the auxiliary air supply unit 28.
- the third embodiment is similar in other structure to that of the first embodiment shown in Fig. 1 and, so, like component parts bear the same reference numerals as those of the first embodiment for omitting duplicated description.
- the third embodiment is configured to allow air, to be increased during purging, to pass only through the combustor 7 and the coolant heat exchanger 8 and exhausted to the outside, flow resistance can be minimized.
- This enables the pressure of auxiliary air to be supplied from the auxiliary air supply unit 28 to be lessened to enable the pressure ratio in the auxiliary air supply unit 28 to be decreased for suppressing the increase in electric power consumption while at the same time, enabling control without changing the condition of air to be supplied to the fuel cell stack 3.
- a demanded flow rate of auxiliary air can be calculated in the same way as that of the second embodiment.
- Figs. 8A to 8E are flowcharts for illustrating combustion temperature control in the third embodiment, with Fig. 8A showing the combustion temperature Te of the combustor 7, Fig. 8B showing the air flow rate of auxiliary air to be supplied from the auxiliary air supply unit 28, Fig. 8C showing the discharge rate of cathode off-gas, Fig. 8D showing the flow rate of hydrogen to be supplied from the hydrogen supply unit 1 and Fig. 8E showing the discharge rate of anode off-gas.
- Fig. 9 is a flowchart for illustrating a control function of the system controller in the third embodiment.
- the cell voltage of the fuel cell stack 3 is detected by the voltage detector means 36, and judgment is made to find whether the cell voltage is less than the given value. If the voltage for each unit cell or the voltage for each group of the unit cells detected by the voltage detector means 36 drop below the given value, operation is routed to S12. If these voltages exceed the given value, then operation is routed back to S10, thereby repeatedly executing detection of the cell voltages and judgment thereof.
- the combustion temperature Te is calculated for predicting the combustion temperature resulting when discharging anode off-gas, upon purging operation to recover the cell voltage, to the combustor 7.
- the predicted value of this combustion temperature Te is calculated, based on the enthalpy calculation for gases flowing into or flowing out from the combustor 7, using the above formulae (1) to (15).
- operation is routed to S40 to carry out normal purging.
- the flow rate Qair air to be increased is calculated.
- the flow rate Qair of air to be increased can be obtained based on the enthalpy calculation where when taking a view in a sense of short term, no variations are regarded to take place in the temperature Tc and the relative humidity Hue of cathode off-gas.
- a purge command is transmitted from the system controller 37 to the auxiliary air supply unit 28, the anode off-gas discharge valve 27 and the hydrogen supply unit 1.
- the auxiliary air supply unit 2 supplies auxiliary air to the combustor 7 while, in S24, the anode off-gas discharge valve 27 is opened and, in S26, the hydrogen supply unit 1 increases the flow rate of hydrogen to be supplied to the anode 4.
- control of the temperature of combustion gas, resulting from the combustor when temporarily discharging anode off-gas from the anode off-gas recirculation unit, in a way not to exceed the given temperature provides an advantageous effect to provide a capability of suppressing degradation in performance of the combustor suffered from an excessive thermal load.
- the fourth embodiment has the same structure as that of the first embodiment shown in Fig. 1.
- the fourth embodiment has a feature wherein if judgment is made that the predicted combustion temperature exceeds the combustion temperature upper limit value, the flow rate of anode off-gas is made smaller than the predetermined discharge rate of the same and a time period in which anode off-gas is discharged is extended to lower the combustion temperature of the combustor.
- the fourth embodiment executes control such that the same calculation as that of the first embodiment is conducted before the combustion temperature Te is calculated whereby if it is judged that the calculated combustion temperature Te exceeds the combustion temperature upper limit value Tmax, the flow rate of cathode off-gas is not altered whereas the discharge rate of anode off-gas is made smaller than the predetermined flow rate and the anode off-gas is discharged for a longer time interval (Tp") than the predetermined discharge time interval (Tp).
- Figs. 10A to 10E are flowcharts for illustrating combustion temperature control in the fourth embodiment, with Fig. 10A showing the combustion temperature Te of the combustor 7, Fig. 10B showing the discharge rate of cathode off-gas, Fig. 10C showing the flow rate of hydrogen to be supplied from the hydrogen supply unit 1, and Fig. 10D showing the discharge rate of anode off-gas.
- HE(Te)" Ho2(Te) X QEo2" + Hn2(Te) X QEn2 + Hh2o(Te) X QEh2o” (KJ/sec), • ⁇ • (13)”
- HC(Tc) +HA(Ta)” HE(Te)" + ⁇ Hb. • • ⁇ (15)"
- Fig. 11 is a flowchart for illustrating a control function of the system controller in the fourth embodiment.
- the cell voltage of the fuel cell stack 3 is detected by the voltage detector means 36, and judgment is made to find whether the cell voltage is less than the given value. If the voltage for each unit cell or the voltage for each group of the unit cells detected by the voltage detector means 36 drop below the given value, operation is routed to S12. If these voltages exceed the given value, then operation is routed back to S10, thereby repeatedly executing detection of the cell voltages and judgment thereof.
- the combustion temperature Te is calculated for predicting the combustion temperature resulting when discharging anode off-gas, upon purging operation to recover the cell voltage, to the combustor 7. The predicted value of this combustion temperature Te is calculated, based on the enthalpy calculation for gases flowing into or flowing out from the combustor 7, using the above formulae (1) to (15).
- the decremental rate Rd of the flow rate of anode off-gas is calculated.
- the anode off-gas discharge time interval Tp" and the discharge rate QAh2" are calculated.
- the calculations can be made based on the enthalpy calculation as discussed above in terms of the above formulae (18), (19) and the formulae (9)" to (15)".
- a purge command is transmitted from the system controller 37 to the anode off-gas discharge valve 27 and the hydrogen supply unit 1.
- the anode off-gas discharge valve 27 is opened while, in S26, the hydrogen supply unit 1 increases the flow rate of hydrogen to be supplied to the anode 4.
- the fifth embodiment has a feature wherein if judgment is made that the predicted combustion temperature exceeds the combustion temperature upper limit value, the discharging mode of anode off-gas is altered to a discontinuous discharge mode. That is, a time interval in which the anode off-gas is discharged in one cycle is made to be shorter than a given discharge time interval and the anode off-gas is repeatedly discharged a plurality of number of times for thereby lowering the combustion temperature of the combustor.
- the fifth embodiment executes control such that the same calculation as that of the first embodiment is conducted until the combustion temperature Te is calculated whereby if it is judged that the calculated combustion temperature Te exceeds the combustion temperature upper limit value Tmax, the flow rate of cathode off-gas and the discharge rate of anode off-gas are not altered whereas the time interval in which the anode off-gas is discharged in one cycle is made to be shorter than a predetermined given discharge time interval and discharging of anode off-gas is conducted for plural number of times during a longer time period than the given discharge time interval.
- FIGs. 12A to 12E are flowcharts for illustrating combustion temperature control in the fourth embodiment, with Fig. 12A showing the combustion temperature Te of the combustor 7, Fig. 12B showing the flow rate of air to be supplied form the air supply unit 2, Fig. 12C showing the discharge rate of cathode off-gas, Fig. 12D showing the flow rate of hydrogen to be supplied from the hydrogen supply unit 1, and Fig. 12E showing the discharge rate of anode off-gas.
- Figs. 12A to 12E repeated operations are executed a plural number of times with anode off-gas being discharged for the time interval Tp"' whereas the discharging is interrupted for the time interval Tr"'.
- the flow rate of hydrogen to be supplied from the hydrogen supply unit 1 is increased by a rate equal to the anode off-gas discharge rate.
- the combustion temperature Te takes the form of a sawtooth waveform as shown in Fig. 12A with control being executed such that a tip of the sawtooth waveform does not exceeds the combustion temperature upper limit value Tmax.
- Fig. 13 is a flowchart for illustrating a control function of the system controller in the fifth embodiment.
- the cell voltage of the fuel cell stack 3 is detected by the voltage detector means 36, and judgment is made to find whether the cell voltage is less than the given value. If the voltage for each unit cell or the voltage for each group of the unit cells detected by the voltage detector means 36 drop below the given value, operation is routed to S12. If these voltages exceed the given value, then operation is routed back to S10, thereby repeatedly executing detection of the cell voltages and judgment thereof.
- a purge command is transmitted from the system controller 37 to the anode off-gas discharge valve 27 and the hydrogen supply unit 1.
- consecutive S70 judgment is made to find whether the given time interval Tp"' has elapsed from the commencement of purging and, if not, operation is routed back to S70. If the given time interval Tp"' has elapsed from the commencement of purging, operation is routed to S72.
- S72 an increase in the flow rate of hydrogen to be supplied from the hydrogen supply unit 1 is interrupted and, in S74, the anode off-gas discharge valve 27 is closed.
- S76 judgment is made to find whether the given time interval Tr"' has elapsed and, if not, operation is routed back to S76.
- operation is routed to S78 where judgment is made to find whether the number the number of times in which the discharging takes place has reached the value of X. If the number of times in which the discharging takes place has not reached the value of X, operation is routed back to S66. If the number of times in which the discharging takes place has reached the value of X, the intermittent purging is interrupted, and operation is returned. This allows the fuel cell system to be restored to the normal operating condition. In the meanwhile, the normal purging to be executed in S40 to S52 is identical in content to that described with reference to the first embodiment and, so, duplicated description is omitted.
- control is so executed to allow the flow rates of cathode off-gas and anode off-gas not to be altered and to permit the time interval in which anode off-gas is discharged for one cycle to be shorter than the given discharge rate while compelling anode off-gas to be discontinuously discharged in plural number of times, and there is an advantageous effect in that, by carrying out the discharging of anode off-gas in a divided fashion, an average combustion temperature during the discharging period can be lowered.
- Fig. 14 is a system structural view illustrating a structure of the sixth embodiment.
- the sixth embodiment contemplates to further include, in addition to the component elements of the first embodiment shown in Fig. 1, a water supply valve 34 for injecting water to the interior of a mixer 23 of the combustor 7, and a temperature detector 29j that detects the temperature of water to be supplied from a pure water pump 35 to the water supply valve 34.
- the sixth embodiment is similar in other structure to that of the first embodiment shown in Fig. 1 and, so, like component parts bear the same reference numerals as those of the first embodiment for omitting duplicated description.
- the pure water is allowed to be supplied from the water supply valve 34 to the combustor 7 at an appropriate flow rate, thereby enabling to suppress an excessive rise in the combustion temperature in a favorable response.
- the flow rate of water to be supplied to the combustor is calculated in a sequence described below.
- FIGs. 15A to 15E are flowcharts for illustrating combustion temperature control in the sixth embodiment, with Fig. 15A showing the combustion temperature Te of the combustor 7, Fig. 15B showing the flow rate of water to be supplied from the water supply valve 34 to the combustor 7, Fig. 15C showing the discharge rate of cathode off-gas, Fig. 15D showing the flow rate of hydrogen to be supplied from the hydrogen supply unit 1 and Fig. 15E showing the discharge rate of anode off-gas.
- the pure water is supplied from the water supply valve 34 to the combustor 7 in compliance with the discharge time period Tp in which anode off-gas is discharged.
- the water supplied to the combustor 7 takes evaporation heat from the circumference as a result of rapid evaporation, resulting in a drop in the combustion temperature of the combustor.
- Fig. 16 is a flowchart for illustrating a control function of the system controller in the sixth embodiment.
- the cell voltage of the fuel cell stack 3 is detected by the voltage detector means 36, and judgment is made to find whether the cell voltage is less than the given value. If the voltage for each unit cell or the voltage for each group of the unit cells detected by the voltage detector means 36 drop below the given value, operation is routed to S12. If these voltages exceed the given value, then operation is routed back to S10, thereby repeatedly executing detection of the cell voltages and judgment thereof.
- using the purging operation for achieving recovery of the cell voltage allows prediction for the combustion temperature as a result of anode off-gas being discharged to the combustor 7 for combustion and, thus, the combustion temperature Te is calculated. The predicted value of this combustion temperature Te is calculated, based on the enthalpy calculation for gases flowing into or flowing out from the combustor 7, using the above formulae (1) to (15).
- operation is executed to calculate the flow rate Qw of water to be supplied from the water supply valve 34 to the combustor 7.
- the flow rate Qw of water to be supplied can be obtained based on the enthalpy calculation based on the water temperature Tw detected by the temperature detector 29j.
- a purge command is transmitted from the system controller 37 to the water supply valve 34, the anode off-gas discharge valve 27 and the hydrogen supply unit 1.
- the air supply unit 2 supplies air to the combustor 7 and, in S84, the supply of water to the combustor 7 from the water supply valve 34 is commenced and, in S86, the anode off-gas discharge valve 27 is opened while, in S88, the hydrogen supply unit 1 increases the flow rate of hydrogen to be supplied to the anode 4.
- a seventh embodiment of the present invention is described with reference to Figs. 18A to 18E and Figs. 19 to 24.
- the seventh embodiment has the same structure as that of the first embodiment shown in Fig. 1.
- the flow rate of air or the flow rate of cathode off-gas
- an actuator such as a pressure regulator valve that controls the air flow rate.
- a membrane electrode assembly (MEA) of the fuel cell must have an increased compressive strength, with a resultant probability of increasing costs.
- an object of the presently filed embodiment is to provide a fuel cell system that is controlled to allow fluctuation in air pressure to be suppressed to compel a combustion temperature of a combustor not to exceed a given temperature even in a fuel cell with no need for specific compressive strength.
- Figs. 18A to 18E are flowcharts for illustrating combustion temperature control in the seventh embodiment, with Fig. 18A showing the combustion temperature Te of the combustor 7, Fig. 18B showing the flow rate of air supplied from the air supply unit 2, Fig. 18C showing the discharge rate of cathode off-gas, Fig. 18D shows the flow rate of hydrogen to be supplied and Fig. 18E showing the discharge rate of anode off-gas. As shown in Figs.
- control is so executed such that when the predicted combustion temperature Te exceeds the combustion temperature upper limit value Tmax, the flow rate of air supplied from the air supply unit 2 is increased to allow the discharge rate of cathode off-gas to increase as shown in Fig. 18C and, therefore, no probability occurs for the combustion temperature of an actual combustor to exceeds the combustion temperature upper limit value Tmax.
- an advantageous effect results in that no situation takes place where the combustion temperature exceeds the combustion temperature upper limit value Tmax, unlike the related art fuel cell system suffered from an excessive temperature rise as indicated by a thin solid line in Fig. 18A, and the combustion catalyst of the combustor is enabled to be prevented from being degraded.
- FIG. 19 is a flowchart for illustrating a control function of the system controller in the seventh embodiment.
- the cell voltage of the fuel cell stack 3 is detected by the voltage detector means 36, and judgment is made to find whether the cell voltage is less than the given value (voltage threshold). If the voltage for each unit cell or the voltage for each group of the unit cells detected by the voltage detector means 36 drop below the voltage threshold, operation is routed to S12. If these voltages exceed the voltage threshold, then operation is routed back to S100, thereby repeatedly executing detection of the cell voltages and judgment thereof. Also, the voltage threshold for use in judgment of the cell voltage in S100 is calculated in a manner described below.
- the voltage threshold value is calculated using table data as shown in
- Fig. 20 This table data is set such that the higher the air temperature, the larger will be the voltage threshold, and thus, as the air temperature increases, operation commences to increase the air flow rate, which will be described below in detail, at an earlier stage. Also, though a detail is described below, since the fluctuation is liable to occur in the air pressure as the air temperature increases, for the purpose of suppressing the pressure fluctuation, operation is executed to minimize the variation rate (absolute value) of the flow rate of air to be increased.
- the voltage threshold for use in judgment of the cell voltage in S100 is calculated using table data as shown in Fig. 21.
- This table data is set such that the higher the air flow rate, the larger will be the voltage threshold and thus, operation commences to increase the air flow rate at an earlier stage. Also, though a detail is described below, since the fluctuation is liable to occur with an increase in the air flow rate, for the purpose of suppressing the pressure fluctuation, operation is executed to minimize the variation rate (absolute value) of the flow rate of air to be increased.
- the variation rate (absolute value) of the flow rate of air to be increased is calculated using table data, as shown in Fig. 23, that is preliminarily stored in the system controller 37.
- the table data shown in Fig. 23 is table data that allows the variation rate of the air flow rate to be obtained from air flow rate and is set such that the higher the air temperature, the less will be the variation rate (absolute value) of the flow rate of air.
- an air density largely varies in terms of variation in the air temperature.
- Table data shown in Fig. 24 is an example of table data with the air flow rate being plotted from which the variation rate (absolute value) of the flow rate of air to be increased can be obtained and is set such that the larger the current air flow rate, the smaller will be the variation rate (absolute value) of the air flow rate. If attempt is made to control the air pressure using a butterfly valve so as to control at to be kept at a fixed pressure, the valve opening increases with an increase in the air flow rate, resulting in degraded sensitivity of the air flow rate in terms of the valve opening.
- the air flow rate can be gradually increased as the air flow rate increases whereby the fluctuation in the air pressure during an incremental phase of the air flow rate can be suppressed.
- the variation rate (absolute value) of the flow rate of air to be increased is calculated to have a value that is greater than that appearing during a decremental phase of the air flow rate subsequent to the incremental phase being terminated.
- the variation rate (absolute value) of the flow rate of air during an incremental phase of the air flow rate shown in a solid line is made greater than the variation rate (absolute value) of the air flow rate of air during a decremental phase of the air flow rate as shown in a broken line.
- the variation rate (absolute value) of the flow rate of air to be increased is calculated using table data as shown by the solid line in Fig. 24.
- a purge command is transmitted from the system controller 37 to the anode off-gas discharge valve 27 and the hydrogen supply unit 1.
- the anode off-gas discharge valve 27 is opened while, in S26, the hydrogen supply unit 1 increases the flow rate of hydrogen to be supplied to the anode 4.
- the variation rate (absolute value) of the flow rate of air to be decreased is calculated using table data as shown in Fig. 22.
- This table data is determined such that as set forth above, the higher the temperature of air, the smaller will be the variation rate (absolute value) of the air flow rate, and has an advantageous effect in that the air flow rate can be gradually decreased as the air temperature increases and the fluctuation in the air pressure during the decremental phase can be suppressed.
- the variation rate (absolute value) of the flow rate of air to be decreased is calculated using table data as shown in Fig. 23.
- This table data is set such that, as set forth above, the larger the current air flow rate, the smaller will be the variation rate (absolute value) of the air flow rate, and has an advantageous effect in that it becomes possible to gradually decrease the air flow rate as the air flow rate increases and the fluctuation in the air pressure during the decremental phase can be suppressed.
- the variation rate (absolute value) of the flow rate of air during the decremental phase is calculated to have a value less than the variation rate (absolute value) of the air flow rate during the incremental phase.
- An advantageous effect resides in that calculation of the variation rate (absolute value) of the air flow rate during the decremental phase depending on table data as shown by the broken line in Fig. 24 allows the fluctuation in the air flow rate to be suppressed in a manner as set forth above not only when increasing the air flow rate but also when decreasing the air flow rate subsequent to the incremental phase.
- the air supply unit 2 commences to decrease the flow rate of air to be supplied to the cathode 5.
- the air flow rate is decreased, and the air flow rate is restored to the original condition. This allows the fuel cell system to be returned to the normal operating condition.
- S40 to S52 are identical to S40 to S52 of the first embodiment shown in Fig. 3.
- the combustion temperature map plotted in terms of the operating condition (here, the flow rate of cathode off-gas and relative humidity) of the fuel cell shown in Fig. 17 may be employed.
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Abstract
Description
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US10/508,448 US7425380B2 (en) | 2002-11-13 | 2003-10-23 | Fuel cell system and related method |
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KR1020047014001A KR100591365B1 (en) | 2002-11-13 | 2003-10-23 | Fuel cell system and related method |
DE60325501T DE60325501D1 (en) | 2002-11-13 | 2003-10-23 | FUEL CELL SYSTEMS AND RELATED METHOD |
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JP3312499B2 (en) | 1994-09-05 | 2002-08-05 | 石川島播磨重工業株式会社 | Fuel cell generator |
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- 2003-10-23 WO PCT/JP2003/013564 patent/WO2004045004A2/en active IP Right Grant
- 2003-10-23 US US10/508,448 patent/US7425380B2/en not_active Expired - Fee Related
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Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2004075327A2 (en) * | 2003-02-19 | 2004-09-02 | Nissan Motor Co., Ltd. | Fuel cell system and fuel cell operating method |
WO2004075327A3 (en) * | 2003-02-19 | 2005-03-03 | Nissan Motor | Fuel cell system and fuel cell operating method |
US7550214B2 (en) | 2003-02-19 | 2009-06-23 | Nissan Motor Co., Ltd. | Fuel cell system and fuel cell operating method |
EP1605539A2 (en) * | 2004-06-10 | 2005-12-14 | Nissan Motor Co., Ltd. | Fuel cell system and method of controlling thereof |
EP1605539A3 (en) * | 2004-06-10 | 2007-12-26 | Nissan Motor Co., Ltd. | Fuel cell system and method of controlling thereof |
WO2006011368A1 (en) * | 2004-07-30 | 2006-02-02 | Nissan Motor Co., Ltd. | Fuel cell power generating system for executing off gas treatment of fuel cells |
AT510354A1 (en) * | 2010-08-25 | 2012-03-15 | Vaillant Group Austria Gmbh | FUEL CELL SYSTEM |
AT510354B1 (en) * | 2010-08-25 | 2014-06-15 | Vaillant Group Austria Gmbh | FUEL CELL SYSTEM |
EP2824743A1 (en) * | 2013-07-08 | 2015-01-14 | Vaillant GmbH | Method for controlling a fuel cell |
EP4145575A1 (en) * | 2021-09-07 | 2023-03-08 | Hyundai Mobis Co., Ltd. | Fuel cell system and method of controlling heater thereof |
Also Published As
Publication number | Publication date |
---|---|
DE60325501D1 (en) | 2009-02-05 |
US20050123813A1 (en) | 2005-06-09 |
EP1556917B1 (en) | 2008-12-24 |
EP1556917A2 (en) | 2005-07-27 |
KR20040089712A (en) | 2004-10-21 |
KR100591365B1 (en) | 2006-06-19 |
WO2004045004A3 (en) | 2005-06-02 |
JP2004179149A (en) | 2004-06-24 |
US7425380B2 (en) | 2008-09-16 |
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