CN101185189A - Fuel cell system and operating method of fuel cell - Google Patents

Abstract

A fuel cell system having a fuel cell receiving predetermined gas and generating power and also having a humidifier for humidifying the gas, supplied to the fuel cell, by using moisture contained in discharge gas discharged from the fuel cell. The fuel cell system has a discharge moisture amount detection means for detecting the amount of moisture contained in the discharge gas and discharged to the downstream of the humidifier, and an adjustment and processing means for limiting, when it is determined that the amount of the discharge moisture is equal to or more than a predetermined amount, the amount of the moisture discharged to the downstream of the humidifier. Appropriate control of humidification can be performed.

Description

Fuel cell system and operating method of fuel cell

technical field

The present invention relates to a fuel cell system having a fuel cell that generates electricity by receiving a supply of a predetermined gas. Specifically, the present invention relates to humidification control using moisture contained in exhaust gas from the fuel cell.

Background technique

In a fuel cell system that supplies air and hydrogen as reaction gases to a fuel cell and generates electricity by electrochemical reaction of hydrogen and oxygen contained in the air, it is necessary to humidify the air supplied to the fuel cell in order to ensure a predetermined power generation efficiency . Heretofore, a technique has been disclosed (for example, see Japanese Patent Laid-Open No. 2002-75418 ) in which a humidifier is provided in the fuel cell system to humidify the air supplied to the fuel cell, wherein the humidifier utilizes Exhaust gas containing moisture generated on the oxygen side by electrochemical reactions.

For example, Patent Document 1 below discloses a system that discharges air (hereinafter, referred to as exhaust gas) that has passed through a fuel cell to the outside through a humidifier. In this system, on the flow path of the exhaust gas, a first pressure control valve is provided between the fuel cell and the humidifier (that is, on the upstream side of the humidifier), and a second pressure control valve is provided on the downstream side of the humidifier, When the humidity of the air supplied to the fuel cell is low, the pressure in the humidifier is controlled to decrease by increasing the opening degree of the second pressure control valve. In this way, the moisture contained in the exhaust gas can be turned into water vapor, and the humidification efficiency of the humidifier can be improved.

Patent Document 1: Japanese Patent Laid-Open No. 2002-75418

Contents of the invention

However, in this prior art, the exhaust gas discharged to the outside of the fuel cell is not taken into account, and there arises a problem that the humidification performance of the humidifier is lowered due to the amount of exhaust gas discharged. That is, the moisture content in the exhaust gas is not all used by the humidifier, but a part thereof is discharged to the outside together with the air as the exhaust gas. The amount of water contained in the exhaust gas is water generated as the fuel cell generates electricity, and is a fixed amount corresponding to the amount of electricity generated. For example, when the flow rate of supply air supplied to the fuel cell is increased in order to increase the amount of power generation, the flow rate of exhaust gas is also increased. In such a situation, even if the amount of water vapor is increased, the amount of moisture discharged to the outside as exhaust gas increases, so that the amount of moisture available for humidification may decrease, resulting in a decrease in the humidification performance of the humidifier.

The present invention is conceived in view of such a problem that the humidification performance of the humidifier decreases, and an object of the present invention is to provide a fuel cell system that performs appropriate humidification control.

The fuel cell system of the present invention employs the following means for the above object. That is, the fuel cell system of the present invention has a fuel cell that generates electricity by receiving a supply of a predetermined gas, and includes a humidifier that is installed on a piping line for exhaust gas from the fuel cell, and utilizes Moisture content in the discharged exhaust gas is used to humidify at least one of supply gases supplied to the fuel cell; an exhaust moisture amount detection means for detecting an exhaust moisture amount included in the exhaust gas and discharged downstream of the humidifier and an adjustment processing means for performing a process of limiting the amount of discharged water discharged downstream of the humidifier when it is determined from the detection result that the discharged water amount is equal to or greater than a predetermined amount.

According to the fuel cell system of the present invention, the amount of discharged water discharged downstream of the humidifier is detected, and the amount of discharged water is restricted when the amount of discharged water is equal to or greater than a predetermined amount. Therefore, the amount of moisture discharged to the downstream of the humidifier is suppressed, and most of the moisture contained in the exhaust gas can be used for humidifying the supply gas in the humidifier. As a result, the decrease in the humidification efficiency of the humidifier is suppressed, and the effect of proper humidification in the humidifier is achieved.

Preferably, the exhaust water amount detection means of the fuel cell system having the above configuration detects a physical quantity that affects the amount of exhaust water contained in the exhaust gas and discharged downstream of the humidifier.

According to such a fuel cell system, a physical quantity that affects the amount of discharged water is detected, and the amount of discharged water is detected from the detected physical quantity, so that the amount of discharged water can be obtained indirectly from the physical quantity.

As such physical quantities, atmospheric pressure, outlet temperature of fuel cell exhaust gas, flow velocity of fuel cell exhaust gas, etc. may be considered, but any physical quantity that affects the amount of exhaust water may be used.

When the physical quantity is atmospheric pressure, when the detected atmospheric pressure is lower than a predetermined pressure, it is determined that the amount of discharged moisture is equal to or greater than a predetermined amount. That is, when the atmospheric pressure is low, it is determined that the pressure in the humidifier has decreased and the amount of discharged water is equal to or greater than a predetermined amount. In this case, the amount of water discharged downstream of the humidifier is suppressed. Therefore, proper humidification can be performed even if the fuel cell system is operated in an environment where the atmospheric pressure is low.

Furthermore, when the physical quantity is the outlet temperature, when the detected outlet temperature is higher than a predetermined value, it is determined that the amount of discharged moisture is equal to or greater than a predetermined amount. That is, when the temperature of the exhaust gas discharged from the fuel cell is high, it is determined that the exhaust gas contains a lot of water and the amount of discharged water is more than a predetermined amount. In this case, the amount of water discharged to the downstream of the humidifier is suppressed. By using such a generally detected temperature, it is possible to easily determine the amount of discharged moisture.

In addition, when the physical quantity is the flow velocity of exhaust gas, when the detected flow velocity is higher than a predetermined value, it is determined that the amount of exhaust water is equal to or greater than the predetermined amount. That is, when the flow velocity of the exhaust gas is high, the flow velocity passing through the humidifier also becomes high, and sufficient humidification cannot be performed in the humidifier. When the flow rate is high, it is determined that the amount of discharged water is equal to or greater than a predetermined amount, and the amount of water discharged to the downstream of the humidifier is suppressed. Therefore, appropriate humidification can be performed in the humidifier.

In the fuel cell system having the above configuration, it is further preferable that an upstream side pressure regulating valve is provided on the upstream side of the humidifier in the flow path of the exhaust gas, and the upstream side pressure regulating valve adjusts the pressure of the exhaust gas by adjusting the pressure of the exhaust gas. The pressure of the supply gas in the fuel cell and the flow rate adjustment processing means restrict the amount of water discharged to the downstream of the humidifier through pressure adjustment by the downstream side pressure adjustment valve.

According to such a fuel cell system, by performing pressure adjustment by the downstream side pressure adjustment valve, as a result, the discharge flow rate can be restricted. That is, the system can be constructed relatively easily by merely disposing the pressure regulating valve on the downstream side of the humidifier.

In the fuel cell system having the above configuration, it is further preferable that an upstream side pressure regulating valve is provided on the upstream side of the humidifier in the flow path of the exhaust gas, and the upstream side pressure regulating valve adjusts the pressure of the exhaust gas by adjusting the pressure of the exhaust gas. The pressure of the supply gas in the fuel cell, and when it is determined that the amount of the discharged water is less than a predetermined amount, instead of adjusting the pressure by the downstream side pressure regulating valve, the pressure adjustment by the upstream side is performed. Pressure adjustment by the pressure adjustment valve.

According to such a fuel cell system, when the amount of discharged water is small, the flow rate to the downstream of the humidifier is not restricted, but the pressure adjustment by the upstream side pressure adjustment valve is performed. Since the control is performed by the pressure regulating valve close to the upstream side of the fuel cell, response delay and the like can be reduced, thereby suppressing a decrease in controllability.

The fuel cell system having the above configuration is further preferably provided with a required humidification amount estimation means for estimating a required humidification amount suitable for the power generation state of the fuel cell; When the required humidification amount is equal to or less than a predetermined value, the pressure adjustment by the upstream side pressure regulating valve is carried out irrespective of the determination of whether the discharge water amount is equal to or greater than a predetermined amount. .

According to such a fuel cell system, when the required amount of humidification is small, processing by the upstream side pressure regulating valve is performed. That is, even when it is judged that the amount of discharged water is more than a predetermined amount, if the required amount of humidification is small, the controllability is given priority over the humidification efficiency of the humidifier, and the upstream side pressure adjustment valve is implemented. control performed. Therefore, proper humidification can be performed when necessary.

In addition, the present invention can also be understood as a method for operating a fuel cell, and can also be understood as a fuel cell system having the following forms. A fuel cell system including a fuel cell that receives a supply of a prescribed gas to generate electricity; and a humidifier that humidifies supply gas supplied to the fuel cell using moisture contained in exhaust gas discharged from the fuel cell, Among them, the system has a discharge water amount detecting means for detecting the amount of discharge water contained in the exhaust gas and discharged downstream of the humidifier; and a flow rate adjustment processing means for judging that the discharge water is When the amount is more than a predetermined amount, a process of restricting the flow rate of the exhaust gas discharged to the downstream of the humidifier is performed.

Furthermore, another fuel cell system having a fuel cell generating electricity by receiving a supply of a predetermined gas includes a humidifier provided on a piping line of exhaust gas from the fuel cell, and utilizing Moisture content in the discharged exhaust gas is used to humidify at least one of the supply gases supplied to the fuel cell; a judging means for judging the exhaust moisture contained in the exhaust gas and discharged downstream of the humidifier based on the state quantity of the exhaust gas and a pressure increasing mechanism that increases the pressure of the exhaust gas in the humidifier to increase the humidification efficiency of the humidifier when it is judged that the condition for the increase in the amount of exhausted water is established.

Description of drawings

Fig. 1 is a schematic configuration diagram of a fuel cell system as an embodiment of the present invention.

FIG. 2 is a flowchart showing the pressure adjustment process of the first embodiment of the fuel cell system of this embodiment.

FIG. 3 is a flowchart showing the pressure adjustment process of the second embodiment of the fuel cell system of the present embodiment.

4 is a flow chart of pressure adjustment processing in which judgment processing of a required humidification amount is added to the pressure adjustment processing of the first embodiment.

Detailed ways

Next, an embodiment for carrying out the present invention will be described in the following order based on examples.

A. Brief structure of fuel cell system

B. Pressure adjustment process of the first embodiment

C. Pressure adjustment process of the second embodiment

D.Modification

A. Brief structure of fuel cell system

Fig. 1 is a schematic configuration diagram of a fuel cell system as an embodiment of the present invention. This fuel cell system 10 has a fuel cell 20 that receives hydrogen and air as reaction gases and generates electricity through an electrochemical reaction between hydrogen and oxygen in the air. on the vehicle shown. As shown, in addition to the fuel cell 20, the system 10 includes a hydrogen system 30 for supplying hydrogen gas to the fuel cell 20, an air system 40 for supplying air to the fuel cell 20, a control unit 120 for controlling various parts, and the like.

The fuel cell 20 has a plurality of unit cells 21 including hydrogen electrodes (hereinafter referred to as anodes) and oxygen electrodes (hereinafter referred to as cathodes), and the stacked plurality of unit cells 21 are sandwiched from both ends by end plates 28 and 29 . And formed. The single cell 21 is constituted by sequentially stacking a separator, an anode, an electrolyte membrane, a cathode, and a separator, and flow paths for hydrogen gas and air are respectively provided on the separator. The flow paths of the above-mentioned various fluids are respectively connected to the inlets of the various fluids provided on the end plate 28 , and the hydrogen and air supplied to the inlets from the outside of the fuel cell 20 are supplied to each of the plurality of single cells 21 without stagnation. In addition, an inlet for a coolant is provided on the end plate 28 , and the coolant supplied from the outside cools the fuel cell 20 .

The hydrogen gas supplied to the anode in each unit cell 21 is catalyzed by the catalyst layer constituting the anode to generate hydrogen ions. The hydrogen ions pass through the electrolyte membrane, reach the cathode side, and react with oxygen in the air supplied to the cathode. Through this electrochemical reaction, the unit cells 21 generate electricity. The fuel cell 20 can output high power by connecting a plurality of such unit cells 21 in series. In addition, in this example, a solid polymer membrane was used as the electrolyte membrane. Such an electrolyte membrane can work well in a specified range of wet conditions.

The hydrogen system 30 is composed of a hydrogen tank 31 storing high-pressure hydrogen gas, a hydrogen circulation pump 32 , valves not shown in the figure, etc., and the hydrogen gas is supplied to the fuel cell 20 after the pressure and flow rate are adjusted by the valve. Hydrogen in the hydrogen gas supplied to the fuel cell 20 is consumed by the above-mentioned electrochemical reaction, but a part thereof may be discharged from the fuel cell 20 without being consumed. The hydrogen circulation pump 32 re-supplies the hydrogen gas discharged from the fuel cell 20 to the fuel cell 20 , so that the discharged hydrogen that is not used in the electrochemical reaction can be effectively used. In addition, instead of supplying hydrogen from the hydrogen tank 31 to supply hydrogen to the fuel cell 20 , for example, methane, methanol, etc. may be reformed to generate hydrogen and supplied to the fuel cell.

The air system 40 is mainly composed of a supply line for supplying air to the fuel cell 20 and an exhaust line for introducing hydrogen gas discharged from the fuel cell 20 into an exhaust system 80 described later.

In the supply pipeline, an atmospheric pressure sensor 47 with a semiconductor strain gauge inside, an air filter 41 for removing dirt and dust in the air, a hot-wire air flow meter 42, and a motor An air compressor 43 as a power source, an intercooler 44 for cooling air to increase the air density, a humidifier 48 for humidifying the supplied air, and supply pipes 45 and 46 connecting these devices are driven by the air compressor 43 to exhaust the atmosphere. The air in the air is introduced and supplied to the fuel cell 20 .

The air introduced from the outside by the driving of the air compressor 43 is first purified by the air cleaner 41 and passes through the air flow meter 42 . The air passing through the air flow meter 42 is compressed by an air compressor 43 , cooled by an intercooler 44 , and then humidified by a humidifier 48 . The humidified air flows through the supply pipe 46 connected to the end plate 28 of the fuel cell 20 and is supplied to the fuel cell 20 .

In this embodiment, a hollow fiber membrane type humidifier is used as the humidifier 48 . The humidifier 48 is provided with a plurality of hollow fiber membranes, the dry gas flows to the outside of the hollow fiber membranes (referred to as the primary side), and the humidified gas flows to the inside of the hollow fiber membranes (referred to as the secondary side). side), thereby humidifying the dry gas on the primary side. The hollow fiber membrane has a plurality of fine capillaries extending from the inside to the outside, and the water vapor of the humid gas passing through the secondary side is sucked out as water by capillary phenomenon. This sucked moisture is supplied to the drying gas on the primary side.

In this embodiment, the primary side of the humidifier 48 is arranged on the supply line, and the secondary side of the humidifier 48 is arranged on the exhaust line as will be described later. The air discharged from the fuel cell 20 contains the produced water generated on the cathode side by the above-mentioned electrochemical reaction as water vapor, and thus becomes a humid gas. The air supplied to the fuel cell 20 can be humidified by using the exhaust air in a humid state.

In such an air supply line, the atmospheric pressure sensor 41 detects the pressure P1 as the external atmospheric pressure, and the air flow meter 42 detects the air flow rate q. The detected pressure P1 and flow rate q are output to the control unit 120 and used for operation control of the fuel cell system 10 , for example, for control of the motor speed of the air compressor 43 supplying an air amount corresponding to the required power generation amount.

On the other hand, a temperature sensor 55 with a built-in thermistor, a semiconductor-type pressure sensor 56, and a first pressure regulating valve 50 for adjusting the pressure according to the opening degree of the valve are arranged in sequence upstream of the air flow discharged from the fuel cell 20 in the exhaust line. , the above-mentioned humidifier 48 (secondary side), the second pressure regulating valve 58 having the same structure as the first pressure regulating valve 50, and the exhaust pipes 51, 52 connecting them, etc., the air discharged from the fuel cell 20 is exhausted Gas pipes 51 and 52 are discharged to the outside.

As mentioned above, two pressure regulating valves 50, 58 are provided on the exhaust line. The two pressure regulating valves 50 and 58 together adjust the air pressure at the outlet of the fuel cell 20 to control the pressure of the air supplied to the fuel cell 20 within a specified range. Through such adjustment of the outlet pressure (hereinafter, this is referred to as an outlet pressure adjustment process), air can be properly supplied without imposing an excessive load on the electrolyte membrane or the like in the fuel cell 20 . In addition, poppet-type valve bodies are used for the pressure regulating valves 50 and 58, and the pressure is adjusted by adjusting the valve opening degree by the forward and backward movement of the poppet valves. The control of the valve opening degree is performed by the control unit 120, and is performed by controlling the rotation angle of the motor for driving the poppet valve.

In the exhaust line of such air, the temperature sensor 55 detects the temperature T of the air discharged from the fuel cell 20 , and the pressure sensor 56 detects the pressure P2 of the air discharged from the fuel cell 20 . The detected temperature T and pressure P2 are output to the control unit 120 and used to control the operation of the fuel cell 10 . In particular, in this embodiment, it is possible to perform pressure adjustment processing for appropriately humidifying the supply air in the humidifier 48 . The pressure adjustment process refers to a process in which the outlet pressure adjustment process described above is performed by either one of the two pressure regulating valves 50 and 58 according to predetermined conditions. For example, when the outlet pressure adjustment process is performed by the second pressure regulating valve 58 on the downstream side of the humidifier 48, the pressure inside the humidifier 48 is also adjusted to a predetermined range to adjust the air discharged to the outside through the inside of the humidifier. traffic. By adjusting the flow rate of the air discharged to the outside, the humidification performance of the humidifier 48 can be improved. This pressure adjustment process will be described in detail later.

The control unit 120 has a CPU, ROM, RAM, timer, input/output ports, and the like. In the ROM, a program for executing the above-described pressure adjustment processing and various programs for controlling the entire fuel cell system 10 are stored. The CPU installs these programs on the RAM for processing. Various sensors and various actuators are connected to the input/output ports. The control unit 120 receives signals from various sensors, judges the running state of the vehicle, and controls various actuators.

Concretely, from the above-mentioned atmospheric pressure sensor 47, pressure sensor 56, temperature sensor 55, air flow meter 42, ammeter 95 of the output system 90 described later, accelerator position sensor not shown in the figure, vehicle speed sensor, etc. The sensors respectively input pressure P1, P2, temperature T, air flow q, output current A, accelerator opening θ, vehicle speed V, etc., and control the air compressor 43 and the first pressure regulating valve 50 according to the required output (electric power). , the second pressure regulating valve 58 , the hydrogen circulation pump 32 , and the pump 72 of the cooling system 70 described later, to operate the fuel cell system 10 .

The fuel cell 20 of the fuel cell system 10 constructed in this way is connected to the cooling system 70, the exhaust system 80, the output system 90, etc. in addition to the hydrogen system 30 and the air system 40 mentioned above.

The cooling system 70 is composed of a radiator 71, a pump 72, pipes connecting them, and the like, and is connected to the end plate 28 of the fuel cell 20 through the pipes. Since the electrochemical reaction inside the fuel cell 20 is an exothermic reaction, the internal temperature rises. Cooling water (coolant) flowing into the fuel cell 20 in order to suppress this temperature rise is cooled by the radiator 71 and circulated by the pump 72 .

The exhaust system 80 mainly includes a muffler 81 , and the air flowing through the exhaust pipe 52 of the air system 40 is exhausted to the atmosphere through the muffler 81 . In addition, nitrogen contained in the air sometimes leaks to the anode side through the electrolyte membrane, and a high concentration of nitrogen is sometimes generated due to the circulation of hydrogen in the hydrogen system 30 . Although not shown in the figure, the exhaust system 80 is also connected to the hydrogen system 30, and this nitrogen is diluted with air and exhausted to the outside at a prescribed time.

The output system 90 is composed of an inverter 91 , a vehicle travel motor 92 , a DC/DC converter 93 , a secondary battery 94 , and the like. The electric power generated by the electrochemical reaction of hydrogen and air supplied to the fuel cell 20 is used for driving the running motor 92 of the vehicle through the inverter 91, and the remainder generated during constant speed running or deceleration, for example, is used by using the motor 92 as The battery is recovered by the generator and stored in the secondary battery 94 through the DC/DC converter 93 .

In the fuel cell system 10 of the present embodiment configured as above, the atmospheric pressure sensor 47, the temperature sensor 55, the air flow meter 42 (air compressor 43), and the control unit 120 constitute the discharge moisture detection means in the claimed scope of the present invention. Moreover, the first pressure regulating valve 50 represents an upstream side pressure regulating valve in the scope of the present invention's request, and the second pressure regulating valve 58 represents a downstream side pressure regulating valve in the present invention's requesting range. These valves and the control unit 120 constitute the present invention. Flow adjustment handling mechanism in the range.

B. Pressure adjustment process of the first embodiment

FIG. 2 is a flowchart showing the pressure adjustment process of the first embodiment of the fuel cell system 10 as the present embodiment. This process is performed by the control unit 120 after the fuel cell system 10 is activated to cause the air compressor 43 to supply air from the outside to the fuel cell 20 . In addition, together with the start-up of the fuel cell system 10 , the opening degree of the first pressure regulating valve 50 is set to a predetermined degree (default value), and the degree of opening of the second pressure regulating valve 58 is set to be fully open. That is, in the initial stage, the outlet pressure of the air of the fuel cell 20 is adjusted to a predetermined range by the first pressure regulating valve 50 .

When the process is started, the control unit 120 inputs the pressure P1 as the detection value of the atmospheric pressure sensor 47 (step S200). Next, it is judged whether the output pressure P1 is lower than a predetermined reference pressure α (step S215).

Atmospheric pressure is a physical quantity that affects the amount of moisture in the flow of air discharged to the outside (referred to as the amount of discharged moisture). The atmospheric pressure can be used to estimate the amount of discharged moisture, the increase or decrease in the amount of discharged moisture, and the like. Here, the determination step S215 is performed as follows. The amount of discharged water is obtained from the atmospheric pressure, and the determination of whether the obtained amount of discharged water is equal to or greater than a predetermined amount is performed instead of pressure. That is, the predetermined reference pressure α here is set in advance as a reference value based on the amount of discharged water, and is stored in the ROM of the control unit 120 . In addition, the reference pressure α set based on the amount of discharged water in this way becomes a reference pressure for judging whether or not the external environment of the fuel cell system 10 is a so-called "highland".

In step S215, when it is judged that the pressure P1 is lower than the reference pressure α, that is, it is judged that the atmospheric pressure is lower than the reference value and corresponds to a "highland" (highland condition) (step S215: Yes), the first pressure regulating valve The opening degree of valve 50 is set to fully open (step S230), and the outlet pressure adjustment process by the second pressure regulating valve 58 is executed (step S240). In the case where the outlet pressure adjustment process by the first pressure regulating valve 50 is performed in the initial stage, this step switches the valve for performing the outlet pressure adjustment process.

In the outlet pressure adjustment process performed by the second pressure regulating valve 58 , control is performed to limit the outlet pressure (and consequently the inlet pressure) of the air of the fuel cell 20 within a predetermined pressure range. For example, when it is determined in the control unit 120 that the current power generation of the fuel cell 20 is excessive relative to the required power generation, the control unit 120 reduces the motor speed of the air compressor 43 to reduce the flow rate of air supplied to the fuel cell 20 . The pressure of the exhaust pipe 51 decreases accordingly. The control unit 120 determines that the pressure of the exhaust pipe 51 has dropped based on the pressure value P2 of the pressure sensor 56, and reduces the opening of the second pressure regulating valve 58 (that is, throttling the flow path) so that the reduced pressure value P2 increases. .

In contrast, when the control unit 120 determines that the current power generation of the fuel cell 20 is insufficient, the control unit 120 increases the motor speed of the air compressor 43 to increase the flow rate of air supplied to the fuel cell 20 . The pressure of the exhaust pipe 51 rises accordingly. The control unit 120 determines the pressure increase of the exhaust pipe 51 based on the pressure value P2 of the pressure sensor 56, and increases the opening degree of the second pressure regulating valve 58 (ie, opens the flow path) to reduce the increased pressure value P2.

By repeating such processing, the control unit 120 keeps the pressure inside the fuel cell 20 substantially constant. As a result of the outlet pressure adjustment process, the flow rate of the air discharged to the downstream of the humidifier 48 is restricted by the second pressure regulating valve 58, and the pressure in the humidifier 48 arranged on the upstream side of the second pressure regulating valve 58 is adjusted to a ratio A pressure in a specified range above atmospheric pressure. After performing such processing for a predetermined period, the flow proceeds to the next step. As a result, the series of processes described above are repeated at predetermined times. In addition, the second pressure regulating valve 58 is controlled to a pressure value obtained by subtracting the pressure loss (pressure loss) of the humidifier 48 from the target pressure value at the outlet of the fuel cell 20 .

On the other hand, in step S215, when it is judged that the pressure P1 is above the reference pressure α, that is, it is judged that the atmospheric pressure is higher than the reference value and does not correspond to "highland" (highland condition) (step S215: NO), the The opening degree of the second pressure regulating valve 58 is set to fully open (step S260), and the outlet pressure adjustment process by the first pressure regulating valve 50 is performed (step S270). When the outlet pressure adjustment processing by the first pressure regulating valve 50 is performed in the initial stage, the original processing is continued.

The outlet pressure adjustment processing by the first pressure regulating valve 50 is performed similarly to the processing by the second pressure regulating valve 58 described above, and the pressure in the fuel cell 20 is kept substantially constant. After performing such processing for a predetermined period, the flow proceeds to the next step. As a result, the series of processes described above are repeated at predetermined times. Also, when the outlet pressure adjustment process by the first pressure regulating valve 50 is performed, the pressure in the humidifier 48 disposed downstream of the first pressure regulating valve 50 is not regulated and is substantially atmospheric pressure.

According to the pressure adjustment process of the first embodiment above, when the atmospheric pressure is low and corresponds to highland conditions, the pressure inside the fuel cell 20 is adjusted using the second pressure regulating valve 58 on the downstream side of the humidifier 48 (the outlet pressure of the air is adjusted). ). That is, the control unit 120 reduces the opening degree of the second pressure regulating valve 58 to throttle the flow path, thereby adjusting the pressure of the air in the fuel cell 20 to a predetermined range higher than the atmospheric pressure. As a result, the interior of the humidifier 48 is adjusted to a predetermined pressure higher than the atmospheric pressure, and the humidification efficiency of the humidifier 48 is improved compared to when the pressure is low (for example, atmospheric pressure in a highland). As the humidification efficiency increases, the proportion of moisture used to humidify the air passing through the humidifier 48 increases. In addition, when the humidification efficiency of the humidifier 48 increases, the proportion of moisture used for humidification increases, and the amount of moisture discharged together with the exhaust gas is therefore reduced.

Therefore, in an environment of highland conditions, the amount of water discharged to the outside of the humidifier 48 (discharged water amount) can be suppressed compared with the case where the pressure is adjusted by the first pressure regulating valve 50 on the upstream side of the humidifier 48 . In other words, it is possible to suppress a decrease in the exchange efficiency of water vapor in the humidifier 48, and it is possible to sufficiently humidify the air even in an environment of high altitude conditions.

For example, in an environment of high altitude conditions, when the pressure in the fuel cell 20 is adjusted by the first pressure regulating valve 50 on the upstream side of the humidifier 48, a part of the flow of air in the humidifier 48 (strictly speaking, in a humid state) The pressure on the side) is reduced to about atmospheric pressure, and the humidification efficiency becomes low. Therefore, the moisture used for humidification decreases, and the amount of water vapor in the air passing through the humidifier 48 increases. When it is discharged directly to the outside, a large amount of water vapor (moisture) is discharged together with the air. According to the processing of the present embodiment, when it is determined from the atmospheric pressure that the moisture content of the air discharged from the fuel cell 20 (discharge moisture content) has increased to a predetermined amount or more, the moisture loss from the humidifier 46 is reduced. Therefore, even if the fuel cell system 10 is operated under highland conditions where the atmospheric pressure is low, appropriate humidification with water balance can be performed, and performance degradation of the fuel cell 20 can be suppressed.

In addition, when the condition does not correspond to highland conditions, although the outlet pressure adjustment process at the upstream side of the humidifier 48 is performed, in this case, since the humidification performance of the humidifier 48 does not decrease significantly, it can be performed. Proper humidification. In this case, the outlet pressure adjustment process is performed by the pressure regulator valve (first pressure regulator valve 50 ) near the air outlet of the fuel cell 20 , whereby the responsiveness in the outlet pressure adjustment process can be improved. In addition, whether it corresponds to highland conditions, in this embodiment, the atmospheric pressure detected by the atmospheric pressure sensor 47 installed on the air intake side is used to judge, but the pressure of the exhaust gas from the humidifier 48 may also be used as the state quantity. One of them is detected, and when the pressure is below a specified value, it is judged as a highland condition. In addition, it is also possible to judge the high ground condition by acquiring altitude data from a car navigation device or the like. As the state quantity of the exhaust gas, the temperature, the flow rate (replaced by the flow velocity) and the like of the exhaust gas can be considered as described in the embodiments and modifications described later.

In this embodiment, although a solid polymer membrane is used as the electrolyte membrane, any electrolyte membrane may be used as long as it works well in a wet state within a predetermined range. As long as the fuel cell system includes a fuel cell having such an electrolyte membrane and a humidifier for humidifying supply air using moisture in exhaust gas, the pressure adjustment process of this embodiment can be applied to perform appropriate humidification.

C. Pressure adjustment process of the second embodiment

In the pressure adjustment processing of the first embodiment, although it is judged that the amount of discharged moisture discharged from the humidifier 48 has increased to a predetermined amount or more based on the atmospheric pressure, in the pressure adjustment processing of the second embodiment, the fuel cell 20 Judgment based on the outlet temperature. That is to say, the pressure adjustment process of the second embodiment is different from the pressure adjustment process of the first embodiment in the judging process of the increase of the moisture content, and the other processes (the outlet pressure adjustment process performed by any pressure regulating valve) It is the same as the pressure adjustment process of the first embodiment. Therefore, the portion of the outlet pressure adjustment process will be briefly described. In addition, the hardware configuration for carrying out the pressure adjustment processing of the second embodiment is basically the same as that of the fuel cell system 10 shown in FIG. 1 , and therefore description thereof will be omitted.

FIG. 3 shows a flowchart of the pressure adjustment process of the second embodiment of the fuel cell system 10 as the present embodiment. This processing is stored in the ROM of the control unit 120 as a processing program, and the CPU reads the program from the ROM and installs it in the RAM to execute the processing.

When starting the process, the control unit 120 inputs the detection value of the temperature sensor 55, that is, the outlet temperature T of the air of the fuel cell 20 (step S300). Next, it is judged whether the outlet temperature T is higher than a predetermined reference temperature β (step S315).

As in the case of the atmospheric pressure in the first embodiment, the outlet temperature of the air of the fuel cell 20 is a physical quantity that affects the amount of discharged water, and the amount of discharged water, the increase or decrease of the discharged water, and the like can be estimated using the outlet temperature. Here, the determination step S315 is performed by calculating the amount of discharged water from the outlet temperature, and replacing the determination of whether the calculated amount of discharged water is equal to or greater than a predetermined amount with temperature. That is, the predetermined reference temperature β here is set in advance as a reference value based on the amount of discharged moisture, and is stored in the ROM of the control unit 120 .

In step S315, when it is determined that the outlet temperature T is higher than the reference temperature β, that is, it is determined that the water vapor contained in the air has increased (step S315: Yes), the opening degree of the first pressure regulating valve 50 is set to To fully open (step S330), the second pressure regulating valve 58 performs outlet pressure adjustment processing for a predetermined period (step S340), and then proceeds to the next step. As a result, the series of processes described above are repeated at predetermined times. This outlet pressure adjustment processing is the same as steps S230 and S240 of the pressure adjustment processing in the first embodiment shown in FIG. 2 .

On the other hand, in step S315, when it is determined that the outlet temperature T is lower than the reference temperature β, that is, when it is determined that the water vapor contained in the air has not increased (step S315: No), the second pressure regulating valve 58 The opening degree of the valve is set to be fully open (step S360), and the outlet pressure adjustment process for a predetermined period is performed by the first pressure regulating valve 50 (step S370), and then proceeds to the next step. As a result, the series of processes described above are repeated at predetermined times. This outlet pressure adjustment processing is the same as steps S260 and S270 of the pressure adjustment processing in the first embodiment shown in FIG. 2 .

According to the pressure adjustment process of the second embodiment above, when the outlet temperature T is high and the water vapor contained in the air increases, the outlet pressure adjustment by the second pressure regulating valve 58 is carried out to limit the flow to the humidifier. 48 The flow rate of the downstream exhaust air. Therefore, similar to the pressure adjustment process of the first embodiment, the amount of moisture discharged to the outside of the humidifier 48 (discharged moisture amount) can be suppressed, and appropriate humidification by the humidifier 48 can be performed.

In addition, in the control of the fuel cell system 10 , generally, the physical quantity of the reactant gas such as the outlet temperature T of the air of the fuel cell 20 is detected. By using such physical quantities for pressure adjustment processing, it is possible to construct a system relatively easily. In addition, when it is judged that the amount of discharged water has increased to a predetermined amount or more, instead of the outlet temperature T, the flow rate q of the air supplied to the fuel cell 20 may be used.

In this case, instead of steps S300 and S315 in FIG. 2 , the control unit 120 may input the detection value (flow rate q) of the air flow meter 42 and compare the flow rate q with a predetermined reference value. When the flow rate q exceeds the specified reference value, the outlet pressure adjustment performed by the second pressure regulating valve 58 in steps S330 and S340 is performed; when the flow rate q does not exceed the specified reference value, the steps S360 and S370 Outlet pressure adjustment by the first pressure regulating valve 50.

That is, when the supply flow rate q per unit time increases to exceed a predetermined reference value, it is determined that the flow velocity of the air discharged from the fuel cell 20 also increases, and the humidification performance of the humidifier 48 decreases. Similar to the first and second embodiments, this predetermined reference value is also a reference value set according to the amount of discharged moisture.

In this case, the flow rate of the air discharged downstream of the humidifier 48 is restricted by performing outlet pressure adjustment processing by the second pressure regulating valve 58 on the downstream side of the humidifier 48 . By doing so, the amount of moisture discharged to the outside of the humidifier 48 (discharged moisture amount) can be reduced compared to the case where the pressure adjustment process is performed using the first pressure regulating valve 50 . In addition, the flow rate (air supply amount) of the supplied air may be estimated from the motor rotation speed of the air compressor 43 .

D.Modification

Although the embodiments of the present invention have been described above, the present invention is of course not limited to these embodiments, and the present invention can be implemented in various forms without departing from the spirit of the present invention. In this embodiment, when setting the predetermined reference values (α, β), the amount of discharged water is obtained from physical quantities such as atmospheric pressure and outlet temperature, but the amount of discharged water itself is not necessarily required. For example, even if the amount of discharged water itself is not known, if it is known through experiments that there is a close correlation between the physical quantity and the amount of discharged water, the reference value of pressure or temperature can be set.

In the present embodiment, although the flow rate discharged downstream of the humidifier 48 is limited by a predetermined reference value, control may be performed such that the degree of restriction of the flow rate increases as the amount of discharged water increases (linear control). . For example, in the case of using atmospheric pressure, the limited flow rate may be set in advance according to the detected pressure value.

In this embodiment, the atmospheric pressure, the outlet temperature, or the delivery rate of the supply air are used as judgment criteria alone, but it is also possible to input all of them, and if any one condition is met, the pressure adjustment system installed downstream of the humidifier will be implemented. The outlet pressure adjustment process performed by the valve.

Moreover, in the pressure adjustment process of the first embodiment and the pressure adjustment process of the second embodiment, although the atmospheric pressure or the outlet temperature (or the air supply volume of the supply air) determines whether the two regulators installed upstream and downstream of the humidifier Which one of the pressure valves performs the outlet pressure adjustment process, however, the pressure regulator valve to perform the outlet pressure adjustment process may be determined in consideration of the required humidification amount required for proper power generation by the fuel cell.

4 is a flow chart of pressure adjustment processing in which judgment processing of a required humidification amount is added to the pressure adjustment processing of the first embodiment. This process is the same as the pressure adjustment process of the second embodiment shown in FIG. 2 and is executed by the control unit 120 . In addition, in the same processing as the pressure adjustment processing of the first embodiment, the same step numbers are used.

When starting the process, the control unit 120 inputs the pressure P1 as the atmospheric pressure (step S200), and judges whether the atmospheric pressure is lower than a reference value (step S215). In step S215, when it is judged that the atmospheric pressure is above the reference value (step S215: No), the second pressure regulating valve 58 is fully opened (step S260), and the first pressure regulating valve 50 performs outlet pressure adjustment processing for a predetermined period. (step S270), and then proceed to the next step. That is, outlet pressure adjustment processing is performed on the upstream side of the humidifier 48 for a predetermined period. As a result of proceeding to the next step, the above-mentioned series of processes are repeated for a predetermined period of time.

On the other hand, when it is judged in step S215 that the atmospheric pressure is lower than the reference value (step S215: Yes), the required humidification amount is calculated from the detection values of various sensors (step S420).

Specifically, the amount of supplied air is calculated from the detection value of the air flow meter 42, the consumption of oxygen in the electrochemical reaction and the amount of water produced are calculated from the detection value of the ammeter 95, and the temperature sensor 55, the pressure sensor 56, The flow rate of the discharged air is calculated from the opening degrees of the pressure valves 50 and 58 , and the current amount of water held in the air in the fuel cell 20 is calculated from these calculated values. This retained moisture amount is compared with a map of the moisture amount set in advance corresponding to the amount of power generation, and the required humidification amount necessary for proper power generation is calculated.

Next, the control unit 120 judges whether or not the requested humidification amount obtained in this way is larger than a predetermined value γ (step S425).

In step S425, when it is determined that the required humidification amount is greater than the specified value γ (step S425: Yes), the first pressure regulating valve 50 is fully opened (step S230), and the second pressure regulating valve 58 implements the outlet for a specified period of time. Pressure adjustment processing (step S240), and then proceed to the next step. That is, outlet pressure adjustment processing is performed on the downstream side of the humidifier 48 for a predetermined period. As a result of proceeding to the next step, the above-mentioned series of processes are repeated for a predetermined period of time.

On the other hand, in step S425, when it is judged that the required humidification amount is below the predetermined value γ (step S425: No), the second pressure regulating valve 58 is fully opened (step S260), and the first pressure regulating valve 50 executes Outlet pressure adjustment processing for a predetermined period (step S270), and then proceed to the next step. That is, outlet pressure adjustment processing is performed on the upstream side of the humidifier 48 for a predetermined period. As a result of proceeding to the next step, the above-mentioned series of processes are repeated for a predetermined period of time.

According to the above pressure adjustment processing, even if it is judged that the atmospheric pressure is low and corresponds to highland conditions, when the required humidification amount is equal to or less than a predetermined value, outlet pressure adjustment processing can be performed on the upstream side of the humidifier 48. That is, even if it is judged that the amount of discharged moisture has increased to more than a predetermined amount, since the amount of humidification required in the fuel cell 20 at present is less than a predetermined amount, the need for humidification is not high. In this case, the responsiveness (controllability) of the outlet pressure of the air of the fuel cell 20 is prioritized, and the outlet pressure adjustment process is performed by the first pressure regulating valve 50 near the outlet of the air of the fuel cell 20 . By doing so, the outlet pressure can be controlled with good responsiveness.

In this embodiment, although pressure regulating valves are respectively provided on the upstream side and downstream side of the humidifier, and the valves for adjusting the outlet pressure of the air of the fuel cell are switched under specified conditions, it is not necessary to switch to any one. valve for outlet pressure adjustment. For example, in the outlet pressure adjustment process, the pressure is always adjusted by the valve on the upstream side of the humidifier, and the amount of discharged moisture may increase to a predetermined amount or more when the atmospheric pressure decreases, the outlet temperature increases, and the flow rate of the discharged air increases. In the case of a humidifier, the opening of the valve on the downstream side of the humidifier can be reduced (throttling the flow path). By doing so, the amount of moisture discharged to the outside can be suppressed, and a reduction in the humidification performance of the humidifier can be suppressed. In addition, the control of the two valves can be facilitated.

Claims (14)

1. A fuel cell system comprising a fuel cell generating electricity by supplying a predetermined gas, comprising: a humidifier provided on a piping line of exhaust gas from the fuel cell, and humidifies at least one of supply gases supplied to the fuel cell using moisture contained in the exhaust gas discharged from the fuel cell; a discharge moisture amount detection mechanism that detects the discharge moisture amount contained in the discharge gas and discharged downstream of the humidifier; and An adjustment processing unit that performs a process of limiting the amount of discharged water discharged downstream of the humidifier when it is determined from the detection result that the discharged water amount is equal to or greater than a predetermined amount. 2. The fuel cell system according to claim 1, wherein, The discharge water amount detection means detects the discharge water amount from a physical quantity that affects the discharge water amount. 3. The fuel cell system according to claim 2, wherein, The discharge water amount detection mechanism is a pressure detection sensor that detects atmospheric pressure as the physical quantity, The adjustment processing means determines that the amount of discharged moisture is equal to or greater than a predetermined amount when the detected atmospheric pressure is equal to or lower than a predetermined pressure. 4. The fuel cell system according to claim 2 or 3, wherein, The exhaust water amount detecting means is a temperature sensor that detects the temperature of the exhaust gas at the outlet of the fuel cell as the physical quantity, The adjustment processing means determines that the amount of discharged moisture is equal to or greater than a predetermined amount when the detected temperature is greater than or equal to a predetermined temperature. 5. The fuel cell system according to any one of claims 2 to 4, wherein, The exhaust moisture amount detection means is a flow velocity sensor that detects the flow velocity of the exhaust gas of the fuel cell as the physical quantity, The adjustment processing means determines that the amount of discharged moisture is equal to or greater than a predetermined amount when the detected flow velocity is equal to or greater than a predetermined value. 6. The fuel cell system according to any one of claims 2 to 5, wherein, The adjustment processing mechanism has a downstream side pressure adjustment valve on the piping line of the exhaust gas on the downstream side of the humidifier, and the downstream pressure adjustment valve adjusts the pressure of the exhaust gas to adjust the pressure in the fuel cell. supply gas pressure, and, The pressure adjustment by the downstream side pressure adjustment valve restricts the amount of water discharged to the downstream of the humidifier. 7. The fuel cell system according to claim 6, wherein, In the adjustment processing mechanism, an upstream side pressure adjustment valve is provided on the upstream side of the humidifier on the piping line of the exhaust gas, and the upstream pressure adjustment valve adjusts the pressure of the exhaust gas to adjust the pressure in the fuel cell. supply gas pressure, and, When it is determined that the amount of discharged water is smaller than a predetermined amount, the pressure adjustment by the upstream pressure adjustment valve is performed instead of the pressure adjustment by the downstream pressure adjustment valve. 8. The fuel cell system according to claim 7, wherein, It also has a required humidification amount estimating means for estimating a required humidification amount suitable for the power generation state of the fuel cell, In the flow rate adjustment processing means, when the estimated required humidification amount is equal to or less than a predetermined value, regardless of whether the discharge water amount is determined to be equal to or greater than a predetermined amount, the upstream side pressure adjustment valve performs pressure adjustment. 9. A fuel cell system comprising a fuel cell generating electricity by receiving a supply of a predetermined gas, comprising: a humidifier provided on a piping line of exhaust gas from the fuel cell, and humidifies at least one of supply gases supplied to the fuel cell using moisture contained in the exhaust gas discharged from the fuel cell; judging means for judging, based on the state quantity of the exhaust gas, whether or not a condition for an increase in the amount of exhaust moisture contained in the exhaust gas to be discharged downstream of the humidifier is satisfied; and The pressure increasing means increases the pressure of the exhaust gas in the humidifier to increase the humidification efficiency of the humidifier when it is determined that the condition for the increase in the amount of exhaust water is satisfied. 10. The fuel cell system according to claim 9, wherein, The determination means is a means for determining the satisfaction of the condition based on any one of the pressure, temperature, and flow rate of the exhaust gas in the humidifier. 11. The fuel cell system according to claim 9 or 10, wherein, The pressure increasing mechanism is provided with a pressure regulating valve downstream of the humidifier, and controls the pressure regulating valve to increase the pressure. 12. A method of operating a fuel cell, which generates electricity by receiving a supply of a predetermined gas, comprising the steps of: Humidifying the supply gas supplied to the fuel cell with moisture contained in the exhaust gas discharged from the fuel cell by a humidifier provided on the piping line of the exhaust gas from the fuel cell; detecting the amount of exhaust moisture contained in the exhaust gas and discharged downstream of the humidifier; and Based on the detected amount of discharged water, the amount of discharged water is limited so that the amount of discharged water discharged downstream of the humidifier does not exceed a predetermined amount. 13. A method for operating a fuel cell, which receives a supply of fuel gas to generate electricity, comprising the steps of: Humidifying the supply gas supplied to the fuel cell with moisture contained in the exhaust gas discharged from the fuel cell by a humidifier provided on the piping line of the exhaust gas from the fuel cell; Based on the state quantity of the exhaust gas, it is judged whether or not a condition for an increase in the amount of exhaust moisture contained in the exhaust gas to be discharged downstream of the humidifier is satisfied; and When it is determined that the condition for the increase in the amount of discharged water is satisfied, the pressure of the discharged gas in the humidifier is increased to increase the humidification efficiency of the humidifier. 14. A fuel cell system having a fuel cell for generating electricity by receiving supply of hydrogen as a fuel gas and air as an oxidizing gas, comprising: a humidifier provided on a piping line of exhaust gas from the air system of the fuel cell, and humidifying the air supplied to the fuel cell using moisture contained in the exhaust gas exhausted from the fuel cell; a sensor that detects at least one of atmospheric pressure, temperature, and flow rate of the exhaust gas as a physical quantity corresponding to an amount of exhaust moisture contained in the exhaust gas and discharged downstream of the humidifier; and a pressure regulating valve that is provided on the downstream side of the humidifier, and restricts the flow path of the exhaust gas when it is determined that the amount of the exhaust water is equal to or greater than a predetermined amount based on the detection result of the sensor, to increase the pressure of the exhaust gas in the humidifier.

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