JP5161650B2 - FUEL CELL SYSTEM AND CONTROL METHOD FOR FUEL CELL SYSTEM - Google Patents

Description

  The present invention relates to a fuel cell system and a control method for the fuel cell system.

  In recent years, fuel cell vehicles equipped with fuel cells such as polymer electrolyte fuel cells (PEFC) have been actively developed. The fuel cell generates power by supplying hydrogen (fuel gas) to the anode and air containing oxygen (oxidant gas) to the cathode. The fuel cell vehicle runs by rotating the motor with the power generated by the fuel cell.

  In such a fuel cell, in order to increase the generated power (output), more hydrogen than the amount consumed in the fuel cell is supplied to the anode. Therefore, surplus hydrogen that is not used is discharged from the anode of the fuel cell. Therefore, in order to improve the utilization efficiency of hydrogen, a hydrogen circulation system is adopted in which the discharged hydrogen is returned to the hydrogen supply side and hydrogen is circulated.

  On the other hand, when such a fuel cell generates power, water is generated at the cathode. A part of the generated water permeates to the anode side of the solid polymer electrolyte membrane (hereinafter, electrolyte membrane). In addition, in order to ensure the wet state of the electrolyte membrane and increase the diffusibility (conductivity) of protons (hydrogen ions) in the electrolyte membrane, for example, hydrogen supplied to the anode of the fuel cell or oxygen supplied to the cathode is used. A method of humidifying the air is included.

  Therefore, in the case of a fuel cell system that employs a hydrogen circulation system, the amount of moisture accompanying the circulating hydrogen increases with the progress of power generation, and the power generation efficiency of the fuel cell may decrease. Therefore, recovery of the power generation efficiency of the fuel cell is attempted by periodically discharging the circulating hydrogen-containing gas (this is called purging). And since the gas (anode off gas) discharged in this way contains hydrogen, it is introduced into a diluter together with a diluting gas (cathode off gas) for diluting it, and diluted with a diluting gas. It is known to be discharged into the outside air (see Patent Document 1).

JP 2007-66717 A

  However, fuel cell vehicles sometimes travel in high altitude areas with low atmospheric pressure. At high altitudes where atmospheric pressure is low, the anode off-gas flows into the diluter because the gas expands despite the same flow rate (mass flow rate) of the anode off-gas discharged to the diluter. After being discharged, it may be discharged into the outside air before being mixed with a certain amount of cathode offgas and discharged. This is because the anode off-gas flowing into the diluter has a low atmospheric pressure (the atmospheric pressure in the diluter is equal to the atmospheric pressure), so the time for expansion in the diluter and residence in the diluter is short (in the diluter). This is because the speed of passing through is faster). In other words, in a place where the atmospheric pressure is low, the diluting capacity of the diluter is insufficient.

  Therefore, when a certain amount of anode off-gas and cathode off-gas is introduced into the diluter regardless of fluctuations in atmospheric pressure, the flow rate of the anode off-gas mixed with the cathode off-gas in the diluter will be different. That is, the flow rate of the anode off gas to be diluted is reduced at high altitudes where atmospheric pressure is low. That is, under a low atmospheric pressure, hydrogen in the anode off gas may be discharged into the outside air without being sufficiently diluted with the cathode off gas. If it is discharged from the diluter before being sufficiently diluted in this way, the hydrogen concentration in the discharged gas (exhaust gas) may be increased.

  Therefore, an object of the present invention is to provide a fuel cell system and a control method for the fuel cell system that prevent the discharge of a gas having a high fuel gas concentration such as hydrogen.

As means for solving the above-mentioned problems, the present invention provides a fuel cell that generates power by being supplied with fuel gas and oxidant gas, fuel gas supply means for supplying fuel gas to the fuel cell, and the fuel cell. to the oxidant gas supply means for supplying oxidant gas, a diluter for diluting the fuel gas in the exhaust fuel gas discharged from the fuel cell by the oxidant gas, and the atmospheric pressure sensor for detecting the atmospheric pressure, the A pipe for introducing the non-humidified oxidant gas from the oxidant gas supply means into the diluter by bypassing the fuel cell, an on-off valve provided in the pipe, and a flow rate of the oxidant gas used for dilution. an oxidant gas flow rate adjusting means for adjusting, the exhaust fuel gas discharged from the fuel cell, discharging the circulating means for circulating back to the upstream side of the fuel cell, the exhaust fuel gas to the diluter Means out, and the discharge fuel gas flow rate adjusting means for adjusting the flow rate of the exhaust fuel gas discharged into the diluter, and a valve control means for controlling the on-off valve, the oxidant gas flow rate adjustment means, wherein If the atmospheric pressure detected by the atmospheric pressure sensor is below a predetermined value, the more the detected atmospheric pressure is low, increasing the flow rate of the oxidizing gas used in the dilution, the exhaust fuel gas flow rate adjusting means, wherein When the atmospheric pressure detected by the atmospheric pressure sensor is less than or equal to a predetermined value, the lower the detected atmospheric pressure is, the smaller the flow rate of the discharged fuel gas discharged to the diluter by the discharge means, and the discharge means When the atmospheric pressure detected by the atmospheric pressure sensor is less than or equal to a predetermined value, the valve control means opens the on-off valve and supplies non-humidified oxidant gas. It is introduced into the diluter through the pipe, a fuel cell system, characterized in that.

  According to such a fuel cell system, when the atmospheric pressure detected by the atmospheric pressure sensor is equal to or lower than a predetermined value, the oxidant gas flow rate adjusting means reduces the oxidation used for dilution as the detected atmospheric pressure is lower. Increase the flow rate of the agent gas. That is, when the atmospheric pressure is less than or equal to a predetermined value, the flow rate of the oxidant gas introduced into the diluter increases.

In this way, when the atmospheric pressure is below a predetermined value, the flow rate of the oxidant gas introduced into the diluter increases, so that the anode off-gas discharged to the diluter is sufficiently mixed and diluted with the cathode off-gas. The concentration of the fuel gas in the gas discharged from the diluter can be reduced, and the discharge of the gas having a high fuel gas concentration can be prevented.
According to such a fuel cell system, when the atmospheric pressure detected by the atmospheric pressure sensor is less than or equal to a predetermined value, the exhaust fuel gas flow rate adjusting means is diluted by the discharge means as the detected atmospheric pressure is lower. Reduce the flow rate of the discharged fuel gas. That is, when the atmospheric pressure is equal to or lower than the predetermined value, the flow rate of the anode off gas discharged to the diluter is reduced.
In this way, when the atmospheric pressure is less than or equal to a predetermined value, the anode off gas discharged to the diluter is reduced in flow rate so that the anode off gas discharged to the diluter is sufficiently mixed and diluted with the cathode off gas, The concentration of the fuel gas in the gas discharged from the diluter can be reduced, and the discharge of the gas having a high fuel gas concentration can be prevented.
According to such a fuel cell system, when the atmospheric pressure detected by the atmospheric pressure sensor is equal to or lower than a predetermined value, the discharged fuel gas flow rate adjusting means discharges by the discharging means as the detected atmospheric pressure is lower. Increase the discharge interval. That is, when the atmospheric pressure is equal to or lower than the predetermined value, the flow rate of the anode off gas discharged to the diluter is reduced.
In this way, when the atmospheric pressure is below a predetermined value, the anode off gas discharged to the diluter is sufficiently mixed and diluted with the cathode off gas by increasing the discharge interval of the anode off gas discharged to the diluter. The concentration of the fuel gas in the gas discharged from the diluter can be reduced, and the discharge of the gas having a high fuel gas concentration can be prevented.

  The oxidant gas flow rate adjusting means does not adjust the flow rate of the oxidant gas used for dilution when the atmospheric pressure detected by the atmospheric pressure sensor is larger than a predetermined value. is there.

  According to such a fuel cell system, the oxidant gas flow rate adjusting means does not adjust the flow rate of the oxidant gas used for dilution when the atmospheric pressure detected by the atmospheric pressure sensor is larger than a predetermined value, that is, Do not increase the flow rate of the oxidant gas.

  Thus, when the atmospheric pressure is larger than the predetermined value, the flow rate of the oxidant gas is not increased, that is, only when the atmospheric pressure is equal to or lower than the predetermined value, the flow rate of the oxidant gas is increased. Thus, only when the atmospheric pressure is below a predetermined value, by operating the oxidant gas flow rate adjusting means, the flow rate of the oxidant gas used for dilution is always increased in consideration of the high altitude. Compared with the set case, it is possible to suppress the operating energy (power consumption of the compressor 31 in the embodiment described later) when traveling outside the place where the atmospheric pressure is not more than the predetermined value, and accordingly, the power generation efficiency ( (Fuel consumption) can be improved.

A fuel cell that generates power by being supplied with fuel gas and oxidant gas, fuel gas supply means for supplying fuel gas to the fuel cell, oxidant gas supply means for supplying oxidant gas to the fuel cell, A diluter that dilutes the fuel gas in the discharged fuel gas discharged from the fuel cell with an oxidant gas, an atmospheric pressure sensor that detects atmospheric pressure, and a non-humidified oxidant gas from the oxidant gas supply means. A pipe for bypassing the fuel cell and introducing it into the diluter, an on-off valve provided in the pipe, an oxidant gas flow rate adjusting means for adjusting the flow rate of the oxidant gas used for dilution, and the fuel cell Circulating means for circulating the discharged exhaust gas back to the upstream side of the fuel cell, exhaust means for discharging the exhaust fuel gas to the diluter, and exhaust fuel gas to be discharged to the diluter And the discharge fuel gas flow rate adjusting means for adjusting an amount, a control method of a fuel cell system and a valve control means for controlling the on-off valve, by the atmospheric pressure sensor, detecting the atmospheric pressure, the A step of determining whether or not the atmospheric pressure is equal to or lower than a predetermined value, and when the atmospheric pressure is equal to or lower than the predetermined value, the lower the detected atmospheric pressure, the greater the flow rate of the oxidizing gas used for dilution. A step of reducing the flow rate of the discharged fuel gas discharged to the diluter by the discharge means when the detected atmospheric pressure is lower when the atmospheric pressure is less than or equal to a predetermined value; and If the detected atmospheric pressure is lower than the value, the lower the detected atmospheric pressure, the longer the discharge interval discharged by the discharging means; and when the atmospheric pressure is equal to or lower than the predetermined value, the on-off valve The Kukoto, non humidification of the oxidant gas, comprising the steps of introducing into the diluter through the pipe, a control method for a fuel cell system, which comprises a.

  According to such a control method of the fuel cell system, when the atmospheric pressure detected by the atmospheric pressure sensor is equal to or lower than a predetermined value, the oxidant gas flow rate adjusting means performs dilution as the detected atmospheric pressure is lower. Increase the flow rate of the oxidizing gas used. That is, when the atmospheric pressure is less than or equal to a predetermined value, the flow rate of the oxidant gas introduced into the diluter increases.

  In this way, when the atmospheric pressure is below a predetermined value, the flow rate of the oxidant gas introduced into the diluter increases, so that the anode off-gas discharged to the diluter is sufficiently mixed and diluted with the cathode off-gas. The concentration of the fuel gas in the gas discharged from the diluter can be reduced, and the discharge of the gas having a high fuel gas concentration can be prevented.

  ADVANTAGE OF THE INVENTION According to this invention, the control method of the fuel cell system and fuel cell system which prevent discharge | emission of gas with high fuel gas concentration, such as hydrogen, can be provided.

One reference embodiment of the present invention will be described with reference to FIGS.

≪Configuration of fuel cell system≫
The fuel cell system 1 according to this reference embodiment shown in Figure 1, is mounted on a fuel cell vehicle (not shown) (mobile). The fuel cell system 1 includes a travel motor (not shown) connected to an output terminal (not shown) of the fuel cell 10, and the fuel cell vehicle drives the travel motor with the generated power of the fuel cell 10. It is designed to run freely even at high altitudes with low atmospheric pressure.

  Such a fuel cell system 1 includes a fuel cell 10, an anode system 20 that supplies and discharges hydrogen (fuel gas) to and from the anode of the fuel cell 10, and air that contains oxygen to the cathode of the fuel cell 10 (oxidation). A cathode system 30 that supplies and discharges (agent gas), a diluter 40, an atmospheric pressure sensor 50, and an ECU (Electronic Control Unit) 60 that electronically controls them.

<Fuel cell>
The fuel cell (fuel cell stack) 10 is configured by stacking (stacking) a plurality of (for example, 200 to 400) solid polymer type single cells, and the plurality of single cells are electrically connected in series. ing. The single cell includes an MEA (Membrane Electrode Assembly) and two conductive anode separators and cathode separators sandwiching the MEA.

  The MEA includes an electrolyte membrane (solid polymer membrane) made of a monovalent cation exchange membrane (for example, perfluorosulfonic acid type), and an anode and a cathode sandwiching the electrolyte membrane. The anode and cathode are mainly composed of a conductive porous material such as carbon paper, and contain a catalyst (Pt, Ru, etc.) for causing an electrode reaction in the anode and cathode.

The anode separator is formed with a through-hole (called an internal manifold) extending in the stacking direction of the single cells and a groove extending in the surface direction of the single cells in order to supply and discharge hydrogen to the anode of each MEA. These through holes and grooves function as the anode flow path 11 (fuel gas flow path).
The cathode separator is formed with a through-hole (referred to as an internal manifold) extending in the stacking direction of the single cells and a groove extending in the surface direction of the single cells in order to supply and discharge air to and from the cathode of each MEA. These through holes and grooves function as the cathode channel 12 (oxidant gas channel).

When hydrogen is supplied to each anode via the anode flow path 11, the electrode reaction of Formula (1) occurs, and when air is supplied to each cathode via the cathode flow path 12, Formula (2) Thus, a potential difference (OCV (Open Circuit Voltage), open circuit voltage) is generated in each single cell. Next, when the fuel cell 10 and an external circuit such as a travel motor (not shown) are electrically connected and a current is taken out, the fuel cell 10 generates power.
2H ₂ → 4H ⁺ + 4e ⁻ (1)
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)

  When power is generated in this way, part of the water (water vapor) generated at the cathode permeates the electrolyte membrane and moves to the anode. Therefore, the cathode off-gas discharged from the cathode and the anode off-gas discharged from the anode are humid.

<Anode system>
The anode system 20 includes a hydrogen tank (fuel gas supply means) 21, a shutoff valve 22, an ejector 23, and a purge valve (discharge means) 24.
The hydrogen tank 21 is connected to the inlet of the anode channel 11 through a pipe 21a, a shutoff valve 22, a pipe 22a, an ejector 23, and a pipe 23a in this order. The piping 22a is provided with a pressure reducing valve (not shown) for reducing hydrogen to a predetermined pressure, and the pressure of the air toward the cathode channel 12 is input to the pressure reducing valve as a signal pressure (pilot pressure), The air pressure and the hydrogen pressure in the anode channel 11 are controlled so as to be equal regardless of the atmospheric pressure.
When the shutoff valve 22 is opened by the ECU 60, the hydrogen in the hydrogen tank 21 is supplied to the anode flow path 11 through the pipe 21a and the like.

A pipe 24a, a purge valve 24, and a pipe 24b are sequentially connected to the outlet of the anode channel 11. Further, the middle of the pipe 24a is connected to the ejector 10 through a pipe 24c (circulation means). A check valve (not shown) that prevents backflow is provided in the middle of the pipe 24c.
The purge valve 24 is an on-off valve such as a gate valve, and is normally closed. When the purge valve 24 is closed in this way, the anode off-gas (exhaust fuel gas) containing unreacted hydrogen discharged from the anode flow path 11 is returned to the ejector 10 via the pipe 24c, and again. The fuel cell 10 is supplied, that is, hydrogen is circulated.
On the other hand, when impurities such as moisture in the anode off gas increase, that is, when impurities accompanying the circulating hydrogen increase, the purge valve 24 is opened by the ECU 60, and the anode off gas passes through the pipe 24b to the diluter. 40 is discharged.

<Cathode system>
The cathode system 30 includes a compressor (oxidant gas supply means) 31 and a back pressure valve 32.
The compressor 31 is connected to the inlet of the cathode channel 12 via a pipe 31a. When the compressor 31 is operated in accordance with a command from the ECU 60, oxygen-containing air is supplied to the cathode channel 12. The pipe 31a is provided with a humidifier (not shown) so that the air sent to the fuel cell 10 is appropriately humidified.
Such a compressor 31 operates using a fuel cell 10 and / or a high-voltage battery (not shown) that charges and discharges power generated by the fuel cell 10 as a power source.

The outlet of the cathode channel 12 is connected to the diluter 40 via a pipe 32a, a back pressure valve 32, and a pipe 32b. The cathode off gas discharged from the cathode channel 12 (cathode) is discharged to the diluter 40 via the pipe 32a and the like.
The back pressure valve 32 is a butterfly valve or the like, and its opening degree is controlled by the ECU 60 in accordance with a required power generation amount such as a depression amount of an accelerator pedal (not shown).

<Diluter>
The diluter 40 is a device (container) for diluting hydrogen in the anode off-gas from the anode system 20, and has a dilution space therein. In this dilution space, the cathode offgas (dilution gas) discharged from the cathode system 30 and the anode offgas containing hydrogen from the anode system 20 are introduced, and the hydrogen in the anode offgas is diluted by the cathode offgas, Exhaust outside the car.

<Atmospheric pressure sensor>
The atmospheric pressure sensor 50 is a sensor that detects atmospheric pressure, and is provided at an appropriate position of the fuel cell vehicle. The atmospheric pressure sensor 50 is connected to the ECU 60, and the ECU 60 detects the atmospheric pressure at the place where the fuel cell vehicle is traveling (traveling place).

<ECU>
The ECU 60 is a control device that electronically controls the fuel cell system 1 and includes a CPU, a ROM, a RAM, various interfaces, an electronic circuit, and the like.
When the ECU 60 detects an IG (ignition) ON signal (not shown), the ECU 60 opens the shut-off valve 22, operates the compressor 31, and appropriately controls the opening degree of the back pressure valve 32 to start power generation of the fuel cell 10. Is configured to do.

  Further, the ECU 60 has a function of adjusting the air flow rate based on the atmospheric pressure detected by the atmospheric pressure sensor 50. Specifically, when the atmospheric pressure is less than or equal to a predetermined value, the ECU 60 operates to increase the rotation of the compressor 31 and controls the opening of the back pressure valve 32 to increase the air flow rate. Is set to On the other hand, when the atmospheric pressure is larger than a predetermined value, the flow rate of air is not adjusted, that is, not increased (the normal flow rate is a flow rate (a constant amount) when the atmospheric pressure is larger than the predetermined value). Yes.

Further, the ECU 60 has a function of adjusting the flow rate of the anode off gas based on the atmospheric pressure detected by the atmospheric pressure sensor 50. Specifically, when the atmospheric pressure is equal to or lower than a predetermined value, the ECU 60 controls to shorten the opening time (opening time) of the purge valve 24 so as to reduce the flow rate of the anode off gas. Has been. On the other hand, when the atmospheric pressure is larger than the predetermined value, the opening time of the purge valve 24 is not adjusted, that is, not shortened (the normal opening time is set as the opening time (a constant time) when the atmospheric pressure is larger than the predetermined value). Is set to
Further, when the atmospheric pressure is equal to or lower than a predetermined value, the ECU 60 is set to increase the anode off gas discharge interval by the purge valve 24 so as to reduce the anode off gas flow rate. On the other hand, when the atmospheric pressure is larger than a predetermined value, the discharge interval of the anode off gas by the purge valve 24 is not adjusted, that is, not increased (the normal discharge interval that is a discharge interval (a constant interval) when the atmospheric pressure is larger than the predetermined value). )).

That is, in this reference embodiment, the oxidant gas flow rate adjusting means includes the compressor 31, the back pressure valve 32, and the ECU 60. The exhaust fuel gas flow rate adjusting means includes a purge valve 24 and an ECU 60.

≪Operation of fuel cell system≫
Next, the operation of the fuel cell system 1 will be described with reference mainly to FIG.

  In step S11, the atmospheric pressure sensor 50 detects the atmospheric pressure where the fuel cell vehicle is traveling (traveling location).

In step S12, the ECU 60 determines whether or not the atmospheric pressure is equal to or less than a predetermined value. The predetermined value here is, for example, a value of atmospheric pressure corresponding to the upper limit value of the hydrogen concentration at which hydrogen in the gas discharged from the diluter 40 (exhaust gas) does not ignite, and is obtained by a preliminary test or simulation. , Stored in advance in the ECU 60 (see FIG. 3). In other words, the pressure at which the lack of capacity of the diluter 40 due to a decrease in atmospheric pressure begins to become manifest is the predetermined value.
When the atmospheric pressure at the travel location is equal to or less than the predetermined value (S12 / Yes), the process of the ECU 60 proceeds to step S13. On the other hand, when the atmospheric pressure at the travel location is greater than the predetermined value (S12 · No), the process of the ECU 60 proceeds to step S16.

  In step S13, the ECU 60 operates to speed up the rotation of the compressor 31 based on the detected atmospheric pressure and controls the opening of the back pressure valve 32 to increase the flow rate of air (FIG. 4 (a)). The relationship between the increased air flow rate and the atmospheric pressure is obtained by a preliminary test or the like and stored in the ECU 60 in advance.

  In step S14, the ECU 60 controls the purge valve 24 to be open for a shorter time (open time), thereby reducing the flow rate of the anode off gas (see FIG. 4B). The relationship between the opening time of the purge valve 24 to be shortened in this way and the atmospheric pressure is obtained by a preliminary test or the like and stored in the ECU 60 in advance.

In step S15, the ECU 60 controls to increase the anode off gas discharge interval by the purge valve 24, thereby reducing the flow rate of the anode off gas (see FIG. 4C). The relationship between the discharge interval of the anode off gas by the purge valve 24 thus lengthened and the atmospheric pressure is obtained by a preliminary test or the like and stored in the ECU 60 in advance.
Note that the processing in steps S13 to S15 may be performed in sequence, but is not limited thereto. For example, only the processing in step S13 may be performed and the processing in steps S14 and S15 may not be performed. .
Thereafter, the processing of the ECU 60 returns to the start via return.

  In step S16, the ECU 60 sets the air flow rate to a normal flow rate that is a flow rate (a constant amount) when the atmospheric pressure is greater than a predetermined value. When the current flow rate of air is a normal flow rate, the processing of this step is not performed.

  In step S17, the ECU 60 sets the opening time of the purge valve 24 to a normal opening time that is an opening time (a constant time) when the atmospheric pressure is larger than a predetermined value. If the current opening time of the purge valve 24 is the normal opening time, the processing in this step is not performed.

In step S18, the ECU 60 sets the discharge interval of the anode off gas by the purge valve 24 to a normal discharge interval that is a discharge interval (a constant interval) when the atmospheric pressure is greater than a predetermined value. If the current discharge interval of the anode off gas by the purge valve 24 is the normal discharge interval, the processing in this step is not performed.
Thereafter, the processing of the ECU 60 returns to the start via return.

≪Effect of fuel cell system≫
Since the fuel cell system 1 is configured as described above, the following operational effects can be obtained.
When the atmospheric pressure detected by the atmospheric pressure sensor 50 is a predetermined value or less, the oxidant gas flow rate adjusting means increases the flow rate of air used for dilution as the detected atmospheric pressure is lower. That is, when the atmospheric pressure is equal to or lower than the predetermined value, the flow rate of air introduced into the diluter 40 increases.

  In this way, when the atmospheric pressure is below a predetermined value, the flow rate of air introduced into the diluter 40 increases, so that the anode off-gas discharged to the diluter 40 is sufficiently mixed and diluted with the cathode off-gas. The concentration of hydrogen in the gas discharged from the diluter 40 can be reduced.

  Further, when the atmospheric pressure detected by the atmospheric pressure sensor 50 is larger than a predetermined value, the oxidant gas flow rate adjusting means does not adjust the flow rate of air used for dilution, that is, does not increase the air flow rate.

  Thus, when the atmospheric pressure is larger than the predetermined value, the air flow rate is not increased, that is, only when the atmospheric pressure is equal to or lower than the predetermined value, the air flow rate is increased. Thus, only when the atmospheric pressure is less than or equal to a predetermined value, the flow rate of air used for dilution is considered by considering the case of high altitude by operating the oxidant gas flow rate adjusting means (making the ECU 60 function). Compared to the case where the system is always set to introduce a large amount, the power consumption of the compressor 31 when traveling outside the place where the atmospheric pressure is not more than a predetermined value can be suppressed, and accordingly, the power generation efficiency (fuel consumption) is reduced. Can be improved.

  Further, when the atmospheric pressure detected by the atmospheric pressure sensor 50 is equal to or lower than a predetermined value, the discharged fuel gas flow rate adjusting means is configured to discharge the anode off-gas discharged to the diluter 40 by the purge valve 24 as the detected atmospheric pressure is lower. Reduce the flow rate. That is, when the atmospheric pressure is equal to or lower than the predetermined value, the flow rate of the anode off gas discharged to the diluter 40 is reduced.

  In this way, when the atmospheric pressure is less than or equal to a predetermined value, the anode off-gas discharged to the diluter 40 is reduced in flow rate so that the anode off-gas discharged to the diluter 40 is sufficiently mixed and diluted with the cathode off-gas. Thus, the hydrogen concentration in the gas discharged from the diluter 40 can be reduced.

  Further, when the atmospheric pressure detected by the atmospheric pressure sensor 50 is less than or equal to a predetermined value, the discharged fuel gas flow rate adjusting means lengthens the discharge interval discharged by the purge valve 24 as the detected atmospheric pressure is lower. That is, when the atmospheric pressure is equal to or lower than the predetermined value, the flow rate of the anode off gas discharged to the diluter 40 is reduced.

  In this way, when the atmospheric pressure is below a predetermined value, the anode off gas discharged to the diluter 40 is sufficiently mixed with the cathode off gas by increasing the discharge interval of the anode off gas discharged to the diluter 40. The concentration of hydrogen in the gas diluted and discharged from the diluter 40 can be reduced. In other words, the lack of capacity of the diluter 40 can be compensated.

≪Example of fuel cell system operation≫
With reference to FIG. 5, an example of the operation of the fuel cell system 1 will be described by taking as an example a case where the fuel cell vehicle travels from a lowland to a highland.
When the fuel cell vehicle travels from low to high, the atmospheric pressure detected by the atmospheric pressure sensor 50 changes from a high atmospheric pressure (value) to a low atmospheric pressure (value).
Then, the flow rates of the anode off-gas containing hydrogen and the cathode off-gas containing air introduced into the diluter 40 are constant amounts (air flow rate: normal flow rate, purge valve 24 open time: normal open time, anode by purge valve 24) Since the off-gas discharge interval is a normal discharge interval, the hydrogen concentration in the gas (exhaust gas) discharged from the diluter 40 tends to increase as the atmospheric pressure decreases in this way ( Comparative example).

  Therefore, when the atmospheric pressure detected by the atmospheric pressure sensor 50 is equal to or lower than the predetermined value (S12 / Yes), the oxidant gas flow rate adjusting means increases the air flow rate as the detected atmospheric pressure is lower ( S13). Further, the discharged fuel gas adjusting means shortens the opening time of the purge valve 24 as the detected atmospheric pressure is lower (S14). Further, the discharged fuel gas adjusting means lengthens the anode off-gas discharge interval by the purge valve 24 as the detected atmospheric pressure is lower (S15).

By increasing the air flow rate in this way, for example, even when the anode off gas flow rate is constant, the anode off gas discharged to the diluter 40 is sufficiently mixed and diluted with the cathode off gas, and the hydrogen concentration in the exhaust gas is increased. Can be reduced.
In addition, by reducing the flow rate of the anode off gas discharged to the diluter 40 in this way (shortening the opening time of the purge valve 24 and increasing the discharge interval of the anode off gas by the purge valve 24), The discharged anode off gas is sufficiently mixed and diluted with the cathode off gas, and the hydrogen concentration in the exhaust gas can be reduced.
Further, by increasing the flow rate of air and decreasing the flow rate of the anode off-gas discharged to the diluter 40, the hydrogen concentration in the exhaust gas can be appropriately reduced ( reference example).

As mentioned above, although one reference form of this invention was demonstrated, this invention is not limited to the said reference form, In the range which does not deviate from the meaning of this invention, it can change as follows, for example, You may combine a structure suitably.

In the reference embodiment described above, the case where the anode off gas and the cathode off gas are used as the gas introduced into the diluter 40 is illustrated, but the present invention is not limited to this. For example, as shown in FIG. 6, the middle of the pipe 31a is connected to the diluter 40 through the pipe 33a, the normally closed on-off valve 33, and the pipe 33b, and the non-humidified air from the compressor 31 is used. May be introduced into the diluter 40.
The on-off valve 33 is an on-off valve such as a gate valve, and is normally closed. When the on-off valve 33 is closed in this way, the air from the compressor 31 is supplied to the cathode flow path 12 via the pipe 31a.
On the other hand, when the atmospheric pressure detected by the atmospheric pressure sensor 50 is less than or equal to a predetermined value, when the on-off valve 33 is opened by the ECU 60, the non-humidified air from the compressor 31 is diluted via the pipe 33a and the like. 40 is introduced. Even when the on-off valve 33 is controlled to the fully open position, a part of the air may flow through the cathode channel 12.

  As described above, by providing the pipe 33a and the like, the non-humidified air from the compressor 31 is introduced into the diluter 40, and as a result, the hydrogen in the anode off-gas is mixed and diluted with the non-humidified air and the cathode off-gas. The hydrogen concentration in the gas (exhaust gas) discharged from the diluter 40 can be appropriately reduced.

In the reference embodiment or embodiment described above, the air flow rate is increased and the anode off-gas flow rate discharged to the diluter 40 is decreased in response to insufficient capacity of the diluter 40 at high altitudes. By making the inside of the vessel 40 have a bellows-like structure, the dilution process can be promoted.

In the reference embodiment or the embodiment described above, the case where hydrogen is used as the fuel gas is exemplified, but the present invention is not limited to this. For example, what can be used as fuel gas, such as methane, should just be used.

In the reference embodiment or embodiment described above, the present invention is applied to the fuel cell system 1 in which the anode off-gas containing unreacted hydrogen is circulated to the ejector 23 as it is, but the present invention is not limited to this.
For example, in order to remove impurities such as moisture in the anode off-gas, the anode off-gas containing unreacted hydrogen is returned to the ejector 23 via a gas-liquid separator (not shown) and re-supplied to the anode channel 11. The present invention may be applied to a fuel cell system.

In the reference embodiment or the embodiment described above, the case where the fuel cell system 1 is mounted on a fuel cell vehicle has been illustrated. However, for example, a fuel cell system mounted on a motorcycle, a train, or a ship may be used. Further, it may be a stationary fuel cell system for home use or business use, or a fuel cell system incorporated in a hot water supply system.

It is a figure which shows the structure of the fuel cell system which concerns on this reference form. It is a flowchart which shows operation | movement of the fuel cell system which concerns on this reference form. It is a map which shows the relationship between atmospheric pressure and the hydrogen concentration in exhaust gas. It is a map which shows the relationship between atmospheric pressure, (a) air flow rate, (b) purge valve opening time, and (c) anode off-gas discharge interval by purge valve. It is a time chart which shows one operation example of the fuel cell system which concerns on this reference form or this embodiment. It is a figure which shows the structure of the fuel cell system which concerns on embodiment .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 10 Fuel cell 21 Hydrogen tank (fuel gas supply means)
31 Compressor (oxidant gas supply means, oxidant gas flow rate adjustment means)
32 Back pressure valve (Oxidant gas flow rate adjusting means)
40 Diluter 50 Atmospheric pressure sensor 60 ECU (Oxidant gas flow rate adjusting means, exhaust fuel gas flow rate adjusting means)

Claims (3)

A fuel cell that generates electricity by being supplied with fuel gas and oxidant gas;
Fuel gas supply means for supplying fuel gas to the fuel cell;
An oxidant gas supply means for supplying an oxidant gas to the fuel cell;
A diluter for diluting the fuel gas in the discharged fuel gas discharged from the fuel cell with an oxidant gas;
An atmospheric pressure sensor for detecting atmospheric pressure;
A pipe for introducing the non-humidified oxidant gas from the oxidant gas supply means into the diluter by bypassing the fuel cell;
An on-off valve provided in the pipe;
An oxidant gas flow rate adjusting means for adjusting the flow rate of the oxidant gas used for dilution;
A circulating means for circulating the exhaust fuel gas discharged from the fuel cell back to the upstream side of the fuel cell;
Discharging means for discharging the discharged fuel gas to the diluter;
An exhaust fuel gas flow rate adjusting means for adjusting the flow rate of the exhaust fuel gas discharged to the diluter;
Valve control means for controlling the on-off valve;
With
When the atmospheric pressure detected by the atmospheric pressure sensor is below a predetermined value, the oxidant gas flow rate adjusting means increases the flow rate of the oxidant gas used for dilution as the detected atmospheric pressure is lower ,
When the atmospheric pressure detected by the atmospheric pressure sensor is less than or equal to a predetermined value, the discharged fuel gas flow rate adjusting means discharges the discharged fuel gas that is discharged to the diluter by the discharge means as the detected atmospheric pressure is lower. And increasing the discharge interval discharged by the discharge means,
When the atmospheric pressure detected by the atmospheric pressure sensor is equal to or lower than a predetermined value, the valve control means opens the on-off valve and introduces a non-humidified oxidant gas into the diluter via the pipe.
A fuel cell system. The oxidant gas flow rate adjusting means does not adjust the flow rate of the oxidant gas used for dilution when the atmospheric pressure detected by the atmospheric pressure sensor is larger than a predetermined value. Fuel cell system. A fuel cell that generates power by being supplied with fuel gas and oxidant gas, fuel gas supply means for supplying fuel gas to the fuel cell, oxidant gas supply means for supplying oxidant gas to the fuel cell, A diluter that dilutes the fuel gas in the discharged fuel gas discharged from the fuel cell with an oxidant gas, an atmospheric pressure sensor that detects atmospheric pressure, and a non-humidified oxidant gas from the oxidant gas supply means. A pipe for bypassing the fuel cell and introducing it into the diluter, an on-off valve provided in the pipe, an oxidant gas flow rate adjusting means for adjusting the flow rate of the oxidant gas used for dilution, and the fuel cell Circulating means for circulating the discharged exhaust gas back to the upstream side of the fuel cell, exhaust means for discharging the exhaust fuel gas to the diluter, and exhaust fuel gas to be discharged to the diluter And the discharge fuel gas flow rate adjusting means for adjusting the amount, and valve control means for controlling the on-off valve, a control method of a fuel cell system comprising,
Detecting atmospheric pressure by the atmospheric pressure sensor;
Determining whether the atmospheric pressure is below a predetermined value;
When the atmospheric pressure is below a predetermined value, the lower the detected atmospheric pressure, the more the flow rate of the oxidizing gas used for dilution; and
When the atmospheric pressure is less than or equal to a predetermined value, the lower the detected atmospheric pressure, the lower the flow rate of the discharged fuel gas discharged to the diluter by the discharge means;
When the atmospheric pressure is below a predetermined value, the lower the detected atmospheric pressure, the longer the discharge interval discharged by the discharge means; and
When the atmospheric pressure is equal to or lower than a predetermined value, the open / close valve is opened to introduce a non-humidified oxidant gas into the diluter via the pipe. How to control the system.

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