JP2009238391A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct water injection type fuel cell system efficiently recovering water and preventing insufficient direct water injection even under high temperatures. <P>SOLUTION: The fuel cell system is constituted so that liquid water can be foggily sprayed in a supply air on an air take-in port side more than a downstream heat exchanger in an air supply passage, that is, in the supply air before flowing in the down stream heat exchanger by a second water supply means. By this constitution, the temperature of supply air before it flows in the down stream heat exchanger can be lowered by latent heat of vaporization of the sprayed liquid water. The supply air on which liquid water is sprayed acts as a cooling medium and condensing ability of water in the downstream heat exchanger can be increased. As a result, the recovery of liquid water in the downstream heat exchanger can be increased. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a direct fountain type fuel cell system including a solid polymer type fuel cell.

  The unit cell of the polymer electrolyte fuel cell has a configuration in which a solid polymer electrolyte membrane is sandwiched between a fuel electrode (hydrogen electrode, anode electrode) and an air electrode (oxygen electrode, cathode electrode). Power generation is performed by electrochemically reacting a supplied fuel gas (for example, hydrogen) and an oxidant gas (for example, air) supplied to the air electrode.

  For example, in Japanese Patent Application Laid-Open No. 11-242962 (Patent Document 1), liquid water is applied to the air electrode in order to cool the air electrode that has generated heat and to prevent the solid polymer electrolyte membrane from being dried and to improve power generation performance. A direct-fountain-type fuel cell system (fuel cell device) that injects in the form of a mist has been proposed.

  Here, an outline of a conventional direct fountain type fuel cell system will be described with reference to FIG. FIG. 7 is a block diagram showing a configuration of a conventional direct fountain type fuel cell system 200.

  As shown in FIG. 7, a conventional fuel cell system 200 includes a fuel cell stack 140 configured by stacking a plurality of unit cells, and hydrogen gas as a fuel gas, and unit cells constituting the fuel cell stack 140. A hydrogen gas supply system 150 for supplying to the fuel electrode, an air supply system 160 for supplying air as an oxidant gas to the air electrode of each unit cell constituting the fuel cell stack 140 at normal pressure, A water supply system 180 that supplies mist-like liquid water to the air electrode of the fuel cell stack 140 to cool and humidify the unit cell, and an exhaust system that discharges exhaust gas discharged from the air electrode of the fuel cell stack 140 120.

  In the fuel cell system 200, hydrogen stored in the hydrogen storage tank 151 in the hydrogen supply system 150 is supplied to the fuel electrode of each unit cell in the fuel cell stack 140, and the outside air (intaken by the blower 161 in the air supply system 160). Electricity is generated by supplying air) to the air electrode of each unit cell through the air manifold 162 at normal pressure.

  On the other hand, the liquid water stored in the water tank 181 in the water supply system 180 is pumped to the nozzle 182 by the water supply pump 180, and the liquid water is ejected from the nozzle 182 toward the air manifold 162. The liquid water jetted to the air manifold 162 in this manner is atomized by the air flow flowing through the air supply system 162 and sent to the fuel cell stack 140 to cool the air electrode and humidify the solid polymer electrolyte membrane. To do.

  A condenser 121 is provided on the exhaust path in the exhaust system 120. The condenser 121 cools the exhaust discharged from the air electrode of the fuel cell stack 140 by heat exchange with the outside air temperature, and condenses and separates moisture contained in the exhaust. The liquid water separated by the condenser 121 is pumped to the water tank 181 by the recovery pump 184.

As described above, the water supply system 180 of the direct fountain type fuel cell system 200 supplies liquid water stored in the water tank 181 as cooling water and humidified water of the fuel cell stack 140, and is discharged from the fuel cell stack 140. The water contained in the exhaust gas is condensed by the condenser 121 and recovered as liquid water, and the recovered liquid water is returned to the water tank 181 as a circulation system.
Japanese Patent Laid-Open No. 11-242962

  However, when the outside air temperature is high, the water supply system 180 configured as such a circulation system has a small temperature difference between the condenser 121 and the outside air, so that the heat exchange (ie, cooling) ability by the condenser 121 is reduced. Lower. As a result, the water condensing efficiency by the condenser 121 is deteriorated, so that sufficient liquid water cannot be recovered from the exhaust gas, and there is a problem that the liquid water (direct jet water) supplied to the fuel cell stack 140 is insufficient. It was. When the direct fountain is insufficient, the fuel cell stack 140 is not sufficiently cooled and humidified, resulting in a decrease in power generation efficiency.

  The present invention has been made in order to solve the above-described problems, and provides a direct fountain type fuel cell system that can recover water well and prevent shortage of direct fountain even under a high temperature environment. The purpose is that.

  In order to achieve this object, a fuel cell system according to claim 1 is a fuel cell comprising a solid polymer electrolyte membrane and a fuel electrode and an air electrode that sandwich the solid polymer electrolyte membrane from both sides; A fuel gas supply means for supplying fuel gas to the fuel electrode; and an oxidant gas supply for supplying supply air taken from outside the system via an air intake port to the air electrode via a supply path at normal pressure Means, water storage means for storing liquid water, first water supply means for injecting liquid water stored in the water storage means in the form of a mist to supply the liquid water to the air electrode, and the fuel cell The upstream heat is located on the fuel cell side of the exhaust path for leading the exhaust exhausted from the air electrode to the outside of the system, and condenses moisture from the exhaust and separates it as liquid water by cooling the exhaust by heat exchange Exchanger and its upstream heat A downstream heat exchanger that is located on the outlet side of the exhaust path from the exchanger and is located on the air supply path and that condenses moisture from the exhaust and separates it as liquid water by cooling the exhaust by heat exchange; Water recovery means for recovering liquid water from the upstream heat exchanger and the downstream heat exchanger and returning it to the water storage means; and liquid water from the downstream heat exchanger in the air supply path to the air intake side. And a second water supply means for injecting the water into a mist.

  The fuel cell system according to claim 2 is the fuel cell system according to claim 1, wherein the water recoverability grasping means for obtaining an index indicating the recoverability of the liquid water by the water recovery means, and the water recoverability grasping means. According to the acquired index, there is provided an injection control means for controlling the injection of water by the second water supply means.

  The fuel cell system according to claim 3 is the fuel cell system according to claim 2, further comprising a storage amount detection means for detecting a storage amount of liquid water stored in the water storage means, wherein the water recoverability grasping means includes: The stored water amount detected by the stored water amount detecting means is acquired as an index indicating the recoverability of the liquid water.

  According to a fourth aspect of the present invention, there is provided a fuel cell system according to the second aspect, wherein a recovery amount estimating means for calculating an estimated recovery amount of liquid water by the water recovery means on the basis of a moisture balance in the system. The water recoverability grasping means acquires the estimated recovered amount of liquid water calculated by the recovered amount estimating means as an index indicating the recoverability of the liquid water.

  According to the fuel cell system of the first aspect, the fuel gas is supplied to the fuel electrode of the polymer electrolyte fuel cell by the fuel gas supply means, while the air electrode is supplied to the fuel electrode by the oxidant gas supply means. Air taken in from outside (supply air) is supplied at normal pressure through the air supply path. As a result, the fuel cell generates power by an electrochemical reaction between the fuel gas and air.

  At this time, the liquid water stored in the storage means is sprayed (sprayed) into the air electrode by the first water supply means. That is, the fuel cell system according to claim 1 is configured as a direct fountain type fuel cell system, and the air electrode is cooled and humidified by the mist-like liquid water (direct fountain).

  Exhaust gas discharged from the air electrode in the fuel cell passes through the upstream heat exchanger and the downstream heat exchanger located on the exhaust path in this order, and is cooled by these heat exchangers. It is led out of the system from the exit. Here, in the upstream heat exchanger and the downstream heat exchanger, moisture in the exhaust is condensed and separated as liquid water by cooling by heat exchange.

  The liquid water separated in the upstream heat exchanger and the downstream heat exchanger is recovered by the water recovery means and returned to the water storage means. Thereby, a system for recovering and circulating liquid water to be supplied as cooling water and humidified water to the air electrode of the fuel cell by the first water supply means from the exhaust discharged from the air electrode by the water recovery means. Composed.

  According to the fuel cell system of the first aspect, the supply air on the air intake side from the downstream heat exchanger in the supply air path, that is, the supply air before flowing into the downstream heat exchanger Thus, the liquid water can be sprayed (sprayed) in the form of mist by the second water supply means.

  With this configuration, the temperature of the supply air flowing into the downstream heat exchanger can be lowered by the evaporation latent heat of the sprayed liquid water. Therefore, the supply air sprayed with liquid water acts as a cooling medium, and the water condensing capacity in the downstream heat exchanger can be enhanced. As a result, the recoverability of liquid water in the downstream heat exchanger can be improved.

  Therefore, even in a high temperature environment where the recoverability of liquid water by the heat exchanger tends to be low, the liquid water can be sufficiently recovered and returned to the water storage means. There is an effect that it is possible to prevent the amount of liquid water supplied to the air electrode of the battery from being insufficient to cool or humidify the fuel cell.

  According to the fuel cell system of claim 2, in addition to the effect of the fuel cell system of claim 1, the following effect is obtained. The second water supply means is configured to be controlled by the injection control means in accordance with an index indicating the recoverability of the liquid water by the water recovery means acquired by the water recoverability grasping means.

  Thus, there is an effect that the recoverability of the liquid water in the downstream heat exchanger can be increased as necessary by causing the second water supply means to inject the liquid water as necessary. Therefore, for example, when the index acquired by the water recoverability grasping means indicates low water recoverability, the second water supply means is controlled to cause the liquid water to be ejected, whereby the downstream heat exchange is performed. As a result, the amount of liquid water supplied to the air electrode of the fuel cell by the first water supply means is insufficient to cool or humidify the fuel cell. It is possible to suitably prevent the amount from being reduced.

  According to the fuel cell system of claim 3, in addition to the effect of the fuel cell system of claim 2, the following effect is obtained. The water storage amount of the water storage means detected by the water storage amount detection means is acquired as an index indicating the recoverability of the liquid water by the water recovery ability grasping means. Therefore, since an index indicating the recoverability of liquid water can be easily acquired, there is an effect that control by the injection control means, that is, control for improving the recoverability of liquid water can be easily performed. .

  According to the fuel cell system of claim 4, in addition to the effect of the fuel cell system of claim 2, the following effect is obtained. The estimated recovery amount of liquid water by the water recovery means calculated by the recovery amount estimation means based on the balance of the amount of water in the system is acquired as an index indicating the recoverability of the liquid water by the water recovery ability grasping means. Therefore, since the index indicating the recoverability of the liquid water is the estimated recovery amount of the liquid water, the control by the injection control means, that is, the control for improving the recoverability of the liquid water is performed by the predictive control (prospect control). There is an effect that can be.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of a fuel cell system 100 which is a fuel cell system of the present invention.

  This fuel cell system 100 uses a fuel cell stack 40 and hydrogen gas as a fuel gas to form a fuel electrode (hydrogen electrode, anode electrode) 13 (for each unit cell 10 (see FIG. 4 and the like)) constituting the fuel cell stack 40 ( A hydrogen gas supply system 50 for supplying to the gas cell stack 40 and air as an oxidant gas are supplied to the air electrode (oxygen electrode, cathode electrode) 12 of each unit cell 10 constituting the fuel cell stack 40 (see FIG. 4). ), And a water supply system 80 for supplying the mist liquid water to the air electrode 12 of each unit cell 10 constituting the fuel cell stack 40 to cool and humidify the unit cell 10. And an exhaust system 110 that exhausts exhaust exhausted from the fuel cell stack 40 (the air electrode 12 of each unit cell 10) to the outside of the system.

  In the fuel cell system 100 shown in FIG. 1, air (supply air, exhaust) flow paths (air supply path 63, air discharge path 111, etc.) are represented by the thickest solid lines, and hydrogen gas flow paths (hydrogen The gas supply channel 51a, the gas outlet channel 51d, etc.) are next represented by the thick solid line, and the water distribution channel (the water conduit 81a, the water supply channel 81c, etc.) is represented by the dotted line. In addition, an electrical output path from the fuel cell stack 40 is indicated by a two-dot chain line.

  The fuel cell stack 40 includes a unit cell 10 (see FIG. 4 and the like) and a separator 20 (see FIG. 4 and the like) that is interposed between the adjacent unit cells 10 and electrically connects the adjacent unit cells 10. The unit cell 10 and the separator 20 are stacked in the thickness direction. The fuel cell stack 40 (each unit cell 10) corresponds to a fuel cell that constitutes the fuel cell system of the present invention.

  The hydrogen gas supply system 50 corresponds to a fuel gas supply means constituting the fuel cell system of the present invention, and a hydrogen storage tank 52 that is a hydrogen cylinder serving as a hydrogen source, and a hydrogen whose one end is connected to the hydrogen storage tank 52. The gas supply channel 51a includes a hydrogen gas supply channel 51b having one end connected to the hydrogen gas supply channel 51a and the other end connected to the gas inlet 41 of the fuel cell stack 40.

  A hydrogen source solenoid valve (not shown), a primary pressure sensor (not shown), and a regulator (not shown) are provided in the hydrogen gas supply channel 51a from the hydrogen storage tank 52 side in the direction of hydrogen gas flow. (Not shown), a secondary pressure sensor SE1, a hydrogen pressure regulating valve 53a and a hydrogen starting solenoid valve (not shown) connected in parallel, a gas supply valve 53b, and a tertiary pressure sensor SE2 are provided in this order. .

  In addition, the hydrogen gas supply system 50 is connected to a gas discharge passage 51c having one end connected to the gas discharge port 42 of the fuel cell stack 40 and to the other end of the gas discharge passage 51c. And a trap 54 for recovering water contained in the discharged hydrogen gas.

  Further, the hydrogen gas supply system 50 has one end connected to the trap 53 and the other end connected to an exhaust passage 111, which will be described later, for deriving hydrogen gas discharged from the fuel cell stack 40 out of the system. A lead-out path 51d is included. An exhaust solenoid valve 53f is provided in the gas lead-out path 51d.

  In addition, the hydrogen gas supply system 50 is connected to the trap 53 at one end side, and has a circulation channel 51 e for circulating the hydrogen gas discharged from the fuel cell stack 40. The circulation channel 51e is provided with a circulation pump 55 and a circulation pressure regulating valve 53c in this order from the trap 54 toward the gas flow direction.

  Further, the hydrogen gas supply system 50 has an outside air introduction path 51g whose one end is connected to the hydrogen gas supply path 51b. The other end side of the outside air introduction path 51g opens to the outside. In the outside air introduction path 51g, a filter 56 and an outside air introduction electromagnetic valve 53d are provided in this order from the opening side. Note that the gas outlet side end of the circulation channel 51e is connected to the hydrogen gas supply channel 51b side of the outside air introduction solenoid valve 53d in the outside air introduction channel 51g.

  Further, the hydrogen gas supply system 50 has a reduced pressure discharge path 51f. The decompression / discharge passage 51f has one end connected between the circulation pump 55 and the circulation pressure regulating valve 53c in the circulation passage 51e, and the other end connected to an exhaust passage 111 described later. The decompression discharge path 51f is provided with a decompression electromagnetic valve 53e.

  The air supply system 60 is provided on the upstream side of an air supply path 63 that is an air supply path and an air flow path (not shown) in the fuel cell stack 40, and an air manifold to which an end portion on the outlet side of the air supply path 63 is connected. 62.

  The air supply path 63 includes a filter 64, an outside air temperature sensor SE6, an air fan 61 such as a sirocco fan or a turbo fan, and an air inlet temperature sensor SE5 from the outside air intake side toward the air flow direction. It is provided in order.

  The air supply system 60 having such a configuration supplies external air taken from outside the system by driving the air fan 61 to the air flow path of the fuel cell stack 40 via the air supply path 63 and the air manifold 62. Therefore, the fuel cell system 100 of the present embodiment is a system that supplies atmospheric pressure air (oxidant gas) to the fuel cell stack 40. The air supply system 60 corresponds to an oxidant gas supply means constituting the fuel cell system of the present invention.

  Further, as shown in FIG. 1, a downstream condenser 113 as a downstream heat exchanger is disposed on the path of the air supply path 63 (specifically, between the filter 64 and the air fan 61). ing.

  The exhaust system 110 includes an air discharge path 111 as an exhaust path whose one end is connected to an exhaust manifold (not shown) provided on the downstream side of the air flow path in the fuel cell stack 40.

  On the path of the air discharge path 111, an exhaust temperature sensor SE9, an upstream condenser 112 as an upstream heat exchanger, and a downstream side from the fuel cell stack 40 side toward the air (exhaust) flow direction. A downstream condenser 113 as a side heat exchanger, a condenser exhaust temperature sensor (not shown), and a filter 114 are provided in this order, and the exhaust gas that has passed through the filter 114 is discharged out of the system.

  Both the upstream condenser 112 and the downstream condenser 113 cool (adjust) the temperature of the exhaust by heat exchange with the outside air temperature, and separate and recover the moisture contained in the exhaust by condensation. .

  As shown in FIG. 1, in the fuel cell system 100 of the present embodiment, the capacity of the upstream condenser 112 is larger than the capacity of the downstream condenser 113, whereby the heat exchange capacity of the upstream condenser 112. This is configured to be larger than the heat exchange capacity of the downstream condenser 113. Therefore, the high-temperature exhaust gas discharged from the fuel cell stack 40 can first be sufficiently cooled to the ambient temperature by the upstream condenser 112 and then flowed into the downstream condenser 113.

  Although details will be described later, in the fuel cell system 100 of the present embodiment, liquid water is sprayed (sprayed) from the nozzle 83b to the supply air before flowing into the downstream condenser 113, and the water By using the latent heat of evaporation to lower the temperature of the supply air flowing into the downstream condenser 113 below the outside air temperature, the water condensing capacity in the downstream condenser 113 is increased and the water recoverability is improved. It is configured.

  Therefore, when the high-temperature exhaust discharged from the fuel cell stack 40 is sufficiently cooled by the upstream condenser 112, the temperature inside the downstream condenser 113 can be suppressed to a relatively low temperature. Therefore, it is possible to prevent moisture from being taken out of the system by the high saturated vapor pressure of the high-temperature gas, and to efficiently condense the water from the exhaust by the supply air cooled by the spray of liquid water. it can.

  As shown in FIG. 1, the upstream condenser 112 is provided with a heat dissipating fan 112a. The amount of heat released from the upstream condenser 112 can be adjusted by the fan 112a.

  The water supply system 80 includes a water tank 82 and a water supply path 81 c that is connected to the water tank 82 at one end and supplies water stored in the water tank 82 to the fuel cell stack 40. In addition, the water supply path 81c in this water supply system 80 corresponds to the 1st water supply means which comprises the fuel cell system of this invention.

  The water tank 82 stores water for supplying cooling water and humidified water to the fuel cell stack 40. The water tank 82 is provided with a water temperature sensor SE7 and a water level sensor SE8. ing.

  A filter 84, a water supply pump 85, a water supply electromagnetic valve 86, and a nozzle 83a serving as an outlet of water from the water supply path 81c are provided in the water supply path 81c from the water tank 82 side in the direction of water flow. It is provided in order.

  The tip of the nozzle 83a is directed to the air manifold 62, and the water guided from the water tank 82 via the water supply path 81c is jetted from the tip of the nozzle 83a. The water jetted from the nozzle 83 a toward the air manifold 62 is sent to the fuel cell stack 40 in the form of a mist by the flow of supply air flowing through the air supply system 60. The water sprayed in the form of mist flows into the air electrode 12 of each unit cell 10 (see FIG. 4 and the like), and acts as cooling water and humidifying water for the fuel cell stack 40.

  An outside air intake path 81d is connected between the water tank 82 and the filter 84 in the water supply path 81c, and an outside air intake electromagnetic valve 87 is provided in the outside air intake path 81.

  As shown in FIG. 1, the water supply system 80 also supplies the water collected by the upstream condenser 112 to the water tank 82, and the water collected by the downstream condenser 113 to the water tank 82. And a water conduit 81b for guiding. In addition, the water conduits 81a and 81b in the water supply system 80 correspond to the water recovery means constituting the fuel cell system of the present invention.

  The water conduit 81a is a path in which one end side is connected to the upstream condenser 112 and the other end side is connected to the water tank 82, and a recovery pump 88 is provided in the water conduit 81a. One end side of the water conduit 81 b is connected to the downstream condenser 113, and the other end is connected between the upstream condenser 112 and the recovery pump 88 in the water conduit 81 a.

  Thus, the water supply system 80 supplies the liquid water stored in the water tank 82 as the cooling water and the humidified water of the fuel cell stack 40 via the water supply path 81c, and the exhaust discharged from the fuel cell stack 40. The water contained therein is condensed by the condensers 112 and 113 and separated as liquid water, and the water is returned to the water tank 82 via the water conduits 81a and 81b.

  Further, as shown in FIG. 1, the water supply system 80 branches from the fuel cell stack 40 side from the water supply pump 85 in the water supply path 81 c and flows the water stored in the water tank 82 into the downstream condenser 113. The water supply path 81e for supplying to the air before performing is included. The water supply path 81e in the water supply system 80 corresponds to the second water supply means that constitutes the fuel cell system of the present invention.

  The water supply path 81e is a water distribution path branched from the fuel cell stack 40 side from the water supply pump 85 in the water supply path 81c as described above, and the other end is the downstream condenser 113 and the filter 64 in the air supply path 63. Connected between. In this water supply path 81e, a water supply electromagnetic valve 89 and a nozzle 83b serving as an outlet of water from the water supply path 81e are sequentially provided from the water tank 82 side toward the direction of water flow.

  The water that has flowed through the water supply path 81e is sprayed from the tip of the nozzle 83b toward the air (supply air) that flows through the air supply path 63. As a result, the supply air is cooled below the ambient temperature by the latent heat of vaporization of the sprayed water, and then flows into the downstream condenser 113.

  Therefore, the supply air flowing into the downstream condenser 113 (that is, the supply air taken from outside the system and sprayed with water) acts as a cooling medium, and as a result, the water condensation capacity in the downstream condenser 113 is reduced. The water recoverability in the downstream condenser 113 is improved.

  Although details will be described later, the fuel cell system 100 of the present embodiment opens the water supply electromagnetic valve 89 when the water level of the stored water stored in the water tank 82 is below a predetermined level by the water level sensor SE8. Then, water is sprayed from the nozzle 83b, thereby improving the recoverability of water in the downstream condenser 113.

  When operating the fuel cell system 100 configured as described above, the air fan 61 is driven to supply outside air (air) taken from outside the system into the air flow path of the fuel cell stack 40, The water supply pump 85 of the supply system 80 is driven to supply water. On the other hand, each solenoid valve (such as solenoid valves 51a to 51g) of the hydrogen gas supply system 50 is adjusted to supply hydrogen gas into the hydrogen gas flow path of the fuel cell stack 40 as a predetermined pressure.

  As a result, a water generation reaction (electrode reaction) between hydrogen and oxygen is performed in each unit cell 10 constituting the fuel cell stack 40, and the generated current flows to the load system 90. During operation of the fuel cell system 100, each unit cell 10 is cooled and humidified by water supplied in the form of a mist.

  A load system 90 is connected to the fuel cell system 100 having the above-described configuration, and power output from the fuel cell stack 40 is supplied to the load system 90. The electrodes of the fuel cell stack 40 are connected to relays 92 and 93 via wiring 91. Further, these relays 92 and 93 are connected to a motor 95 via an inverter 94. In addition, an auxiliary power source 96 is connected to the inverter 94 via an output control device 95. The load system 90 is provided with a voltage sensor SE4 for detecting the output voltage of the fuel cell stack 40 and a current sensor SE3 for detecting the output current of the fuel cell stack 40.

  As shown in FIG. 1, the fuel cell system 100 of the present embodiment further includes a control device 70 that controls the operation of the fuel cell system 100. The control device 70 includes a CPU 71 which is a central processing unit, a ROM 72 which is a non-rewritable nonvolatile memory storing a control program executed by the CPU 71 and fixed value data, and various data when the control program is executed. Are rewritable RAM 73 and CPU 71, ROM 72, and input / output port 75 connected to RAM 73 via bus line 74.

  An input / output port 75 of the control device 70 has sensors (sensors SE1 to SE9, etc.), solenoid valves (electromagnetic valves 51a to 51f, 86, 87, etc.), pumps 85, 88, and air by wiring (not shown). The fan 61, the inverter 94, and the output control device 95 are connected. Based on the input of the detection value from each sensor, the control device 70 includes each electromagnetic valve (electromagnetic valves 51a to 51f, 86, 87, etc.), each pump 85, 88, air fan 61, inverter 94, and output control device. Various controls for operating the fuel cell system 100 such as a control of 95 and the like are performed.

  Further, as shown in FIG. 1, in the fuel cell system 100 of the present embodiment, the input / output port 75 of the control device 70 includes a water level sensor SE8 that detects the level of stored water stored in the water tank 82, and a water supply channel. It is connected to a water supply electromagnetic valve 89 provided on 81e.

  Although details will be described later, the control device 70 of the fuel cell system 100 according to the present embodiment detects when the detection value by the water level sensor SE8 (that is, the water level of the stored water stored in the water tank 82) becomes a predetermined level or less. The water supply electromagnetic valve 89 is opened in order to improve the water recoverability of the downstream condenser 113 by determining that the water recoverability is low.

  Next, the configuration of the fuel cell stack 40 will be described with reference to FIGS. FIG. 2A is a top view schematically showing the fuel cell stack 40 in the present embodiment, and FIG. 2B is a top view schematically showing the cell module 30 constituting the fuel cell stack 40. is there. In FIG. 2A, two cell modules 30 are shown as representatives, and the other cell modules 30 are not shown. Further, in FIG. 2B, only the positional relationship between the unit cell 10 and the separator 20 is illustrated for the purpose of facilitating understanding, and a specific configuration is omitted.

  FIG. 3A is a front view of the cell module 30 viewed from the air electrode side, and FIG. 3B is a front view of the cell module 30 viewed from the fuel electrode side. 4A is a cross-sectional view taken along the arrow IVa-IVa in FIG. 3A, and FIG. 4B is a cross-sectional view taken along the arrow in FIG.

  As shown in FIG. 2A, the fuel cell stack 40 in the present embodiment is configured by stacking a plurality of cell modules 30.

  As shown in FIG. 2B, the cell module 30 includes a unit cell 10 and a separator 20 that is interposed between the adjacent unit cells 10 and electrically connects the adjacent unit cells 10 to each other. 10 and frames 17 and 18 that support the separator 20 are set as one set, and a plurality of sets are laminated in the thickness direction. In addition, the cell module 30 illustrated in FIG. 2B is obtained by laminating 10 sets each including the unit cell 10 and the separator 20.

  In the cell module 30, unit cells 10 and separators 20 are stacked in multiple stages using two types of frames 17 and 18 alternately as spacers so that adjacent unit cells 10 are arranged at a predetermined interval. Are stacked.

  One end of the cell module 30 in the stacking direction (the upper end surface side in FIG. 2A) terminates at the end surface of the air electrode side collector 22 of the separator 20 and the end surface of the frame 17 as shown in FIG. ing. On the other hand, the other end of the cell module 30 in the stacking direction (the lower end face side in FIG. 2A) is the end face of the fuel electrode side collector 23 of the separator 20 and the end face of the frame 18, as shown in FIG. And terminated with.

  As shown in FIG. 4A and FIG. 4B, the unit cell 10 includes a solid polymer electrolyte membrane 11, an air electrode 12 in contact with one surface of the solid polymer electrolyte membrane 11, a solid height The fuel electrode 13 is in contact with the other surface of the molecular electrolyte membrane 11.

  Examples of the solid polymer electrolyte membrane 11 include solid polymer electrolyte membranes applicable to solid polymer fuel cells such as Nafion (registered trademark: manufactured by DuPont) and Aciplex (registered trademark: manufactured by Asahi Kasei Co., Ltd.). Can be used.

  The air electrode 12 is formed on a diffusion layer (not shown) made of a conductive material that permeates while diffusing air (oxidant gas), and is in contact with the solid polymer electrolyte membrane 11. And a reaction layer (not shown).

  The fuel electrode 13 is formed on a diffusion layer (not shown) made of a conductive material that permeates while diffusing hydrogen gas (fuel gas), and is in contact with the solid polymer electrolyte membrane 11. And a reaction layer (not shown).

  The diffusion layer constituting the air electrode 12 and the fuel electrode 13 is composed of carbon woven fabric, carbon paper, etc. capable of gas diffusion, for example, carbon cloth, carbon paper, carbon fiber. The nonwoven fabric etc. which become can be used. In addition, as the reaction layer constituting the air electrode 12 and the fuel electrode 13, for example, a reaction layer (catalyst layer) configured to include carbon carrying a platinum catalyst and PTFE (polytetrafluoroethylene) is employed. can do.

  Among the members constituting the unit cell 10, the air electrode 12 and the fuel electrode 13 have a lateral dimension slightly longer than the lateral dimension (short dimension) of the opening of the frame 18 serving as a supporting member thereof, and the opening. The vertical dimension (longitudinal dimension) is slightly longer than the vertical dimension. Further, the solid polymer electrolyte membrane 11 has a vertical and horizontal dimension that is slightly larger than the vertical and horizontal dimensions of the opening.

  The separator 20 is provided on one side of the separator body 21, the air electrode side collector 22 that is in contact with the diffusion layer (not shown) of the air electrode 12 of the unit cell 10, and the separator body 21. And a fuel electrode side collector 23 which is provided on the other side and abuts against a diffusion layer (not shown) of the fuel electrode 13 of the unit cell 10.

  The separator body 21 is a thin metal plate that functions as a gas blocking member between adjacent unit cells 10. Examples of the metal constituting the separator body 21 include a metal having conductivity and corrosion resistance, for example, a stainless steel, a nickel alloy, a titanium alloy and the like subjected to a corrosion-resistant conductive treatment such as gold plating.

  The air electrode side collector 22 is in contact with the air electrode 12 and collects current, and is also a conductive member having a large number of holes that enables supply of air to the air electrode 12 and discharge of generated water from the air electrode 12. It is. The air electrode side collector 22 also functions as a heat sink and is cooled by water sprayed (sprayed) from the nozzle 83 (see FIG. 1) of the water supply system 80. The detailed configuration of the air electrode side collector 22 will be described later with reference to FIG.

  The fuel electrode-side collector 23 is a conductive member that contacts the fuel electrode 13 and collects current and has a large number of holes that enable supply of hydrogen gas to the fuel electrode 13. In addition, since this fuel electrode side collector 23 can be comprised similarly to the air electrode side collector 22, detailed description is abbreviate | omitted.

  Frames 17 and 18 are arranged outside the separator 20 so that the unit cell 10 can be held in a predetermined positional relationship. These frames 17 and 18 are made of an insulating material.

  More specifically, the frames 17 are arranged on the left and right sides of the air electrode side collector 22, and the frame 18 is provided on the peripheral edge of the fuel electrode side collector 23. As shown in FIG. 3, the uppermost and lower ends of the frame 17 arranged at the outermost end are connected to each other by backup plates 17a and 17b to form a frame shape.

  As shown in FIGS. 4A and 4B, the frame 17 disposed on the air electrode side collector 22 side has an outer end (the uppermost end in FIG. 4A and the left end in FIG. 4B). The vertical frame portions 171 are arranged on both sides along the short side of the air electrode side collector 22 except for those arranged on the air electrode side collector 22. The thickness of the frame 17 is comparable to the thickness of the air electrode side collector 22.

  The vertical frame portion 171 is provided with a long hole 172 penetrating in the thickness direction for forming a hydrogen gas flow path. The vertical and horizontal dimensions on the surface of the separator body 21 are comparable to the vertical and horizontal dimensions on the surface of the frame 17, and the same long hole 212 is provided at a position overlapping the long hole 172 of the frame 17. Yes.

  With the arrangement of the frame 17, an air chamber surrounded by the air electrode 12 of the unit cell 10 and the separator body 21 is formed between the left and right vertical frame portions 171. Although details will be described later, a plurality of linear rib members 222 (a part of the air electrode side collector 22) extending in the direction perpendicular to the paper surface in FIG. In addition, the installation of the rib member 222 forms an air flow path that passes all the way in one direction (the direction perpendicular to the paper surface in FIG. 4A).

  On the other hand, as shown in FIG. 4B, the frame 18 surrounding the fuel electrode side collector 23 and the unit cell 10 is a frame-shaped member having left and right vertical frame portions and upper and lower horizontal frame portions 182 and is configured in a frame shape. The size of the frame 17 is the same as that of the frame 17 (FIG. 3A). The left and right vertical frame portions of the frame 18 are not shown because they are located further to the right than the description range of FIG. 4A, but both sides are located at the same positions as the left and right side ends of both the vertical frame portions 171 of the frame 17. The length (width) in the short direction is substantially the same as the length in the short direction of the upper and lower horizontal frame portions 182.

  As shown in FIG. 4A, the frame 18 is parallel to the left and right vertical frame portions except for the frame 18 arranged at the outer end (the bottom end in FIG. 2B, the surface shown in FIG. 3B). The thin plate-like backup plate 18a and the thick plate-like backup plate 18b extend and overlap the left and right ends of the fuel electrode side collector 23 (end portions in the left and right direction in FIG. 4A). The thickness of the frame 18 is comparable to the thickness of the fuel electrode side collector 23.

  A space surrounded by the backup plate 18a and the vertical frame portion 171 constitutes a space for forming a hydrogen gas flow path together with the long hole 172 penetrating the frame 17 in the plate thickness direction. A fuel chamber surrounded by the fuel electrode 13 of the unit cell 10 and the separator body 21 is formed on the inner peripheral side of each frame 18.

  In this fuel chamber, a linear rib member 232 (fuel electrode side collector) extending in a direction orthogonal to the rib member 222 (that is, a direction perpendicular to the paper surface in FIG. 4B and a horizontal direction in FIG. 4A). 23) are standing upright in parallel. The installation of the rib member 232 forms a hydrogen gas flow path that passes completely in the direction perpendicular to the air flow path described above (the direction perpendicular to the paper surface in FIG. 4B).

  Next, a detailed configuration of the air electrode side collector 22 will be described with reference to FIG. FIG. 5A is a front view of the air electrode side collector 22 viewed from the separator body 21 side, and FIG. 5B is a side view of the air electrode side collector 22 viewed from the Vb direction in FIG. 5A and 5B, illustration of the holes 221a and 221b opened in the base collector 221 is omitted.

  As shown in FIGS. 5A and 5B, the air electrode side collector 22 of the present embodiment includes a base collector 221 and a plurality of rib members 222.

  The base collector 221 is a conductive plate that is brought into contact with the air electrode 12 of the unit cell 10 and collects current from the air electrode 12. The base collector 221 is manufactured from a metal having conductivity and corrosion resistance, such as stainless steel, nickel alloy, titanium alloy or the like subjected to corrosion resistance conductive treatment such as gold plating.

  The base collector 221 is composed of a porous body having a large number of holes, for example, an expanded metal or a punching metal. In addition, although the shape of the hole opened to the base collector 221 is not illustrated in the present embodiment, for example, a rhombus, a square, a hexagon, a circle, or the like can be appropriately employed.

  When the hole opened in the base collector 221 has a rhombus shape, for example, the shorter diagonal dimension is about 0.7 mm to about 1.3 mm, and the longer diagonal dimension is about 0 mm. It can be designed to be about 8 mm to about 2.8 mm. Moreover, it is preferable that the aperture ratio of the hole opened to the base collector 221 is about 30 to about 50%.

  On the other hand, as shown in FIGS. 5A and 5B, each of the plurality of rib members 222 is a linear body having a rectangular cross section, and these rib members 222 are formed of the base collector 221. Are arranged in a state of being arranged substantially parallel to each other on the surface opposite to the contact surface with the air electrode 12. The rib member 222 is bonded to the surface of the base collector 221 by, for example, diffusion bonding.

  Thus, the rib member 222 erected on the base collector 221 is inserted between the base collector 221 and the separator body 21 in the air electrode side collector 22 to form an air flow path (air chamber). Create a space.

  In order to realize high-efficiency power generation in the fuel cell and suppress power loss of the auxiliary equipment, it is preferable to reduce the air flow resistance of the air flow path as much as possible. Therefore, it is necessary to appropriately secure the height of the flow path for supplying air to the unit cell 10, that is, the height of the rib member 222, while reducing the size of the fuel cell stack 40, that is, the cell module 30. In order to reduce the size, the height of the rib member 222 is preferably as low as possible. Therefore, the height dimension of the rib member 222 is set to a height that satisfies both of these conditions, for example, about 0.5 mm to about 0.9 mm.

  The rib member 222 is made of a metal having conductivity and corrosion resistance. In addition, the material (material) which comprises the rib member 222 may be the same material as the base collector 221 mentioned above, or a different material. Further, the cross-sectional shape of the rib member 222 is not limited to the rectangular shape illustrated in FIG. 5B, and may be other shapes such as a triangle or a circle.

  The fuel electrode side collector 23 can also be configured in the same manner as the air electrode side collector 22. That is, if the fuel electrode side collector 23 is composed of a base collector 231 corresponding to the base collector 221 (see FIG. 4B) and a rib member 232 corresponding to the rib member 222 (see FIG. 4B). Good.

  Next, a method for controlling the recoverability of water from the downstream condenser 113 in the fuel cell system 100 having the above configuration will be described with reference to FIG. FIG. 6 is a flowchart showing the water supply electromagnetic valve opening / closing process executed in the control device 70 in the fuel cell system 100.

  This water supply electromagnetic valve opening / closing process is a process for opening / closing the water supply electromagnetic valve 89 in accordance with the value detected by the water level sensor SE8, and is periodically performed by the CPU 71 while the control device 70 is powered on ( It is executed repeatedly (for example, at intervals of 0.5 s). A control program for executing the water supply electromagnetic valve opening / closing process is stored in the ROM 72.

  As shown in FIG. 7, in this supply air temperature adjustment process, first, the detection value by the water level sensor SE8, that is, the detection value indicating the water level of the stored water stored in the water tank 82, indicates the recoverability of the liquid water. Obtained as an index (S1). After the process of S1, it is confirmed whether or not the acquired index, that is, the water level indicated by the detection value by the water level sensor SE8 is less than the first threshold that is the lower threshold (S2).

  If the water level is less than the first threshold (S2: Yes), the water supply solenoid valve 89 is determined to be low and the water supply solenoid valve 89 is opened (S3). The supply solenoid valve opening / closing process is terminated.

  When the water supply electromagnetic valve 89 is opened by the process of S3, water is sprayed (sprayed) from the nozzle 83b toward the air supply path 63, and the supply air is cooled by the latent heat of evaporation of water. As a result, the supply air thus cooled flows into the downstream condenser 113, so that the supply air (that is, the supply air sprayed with water) acts as a cooling medium, and the downstream condenser 113 The recoverability of liquid water is improved.

  On the other hand, when the water level is equal to or higher than the first threshold value as a result of checking in the process of S2 (S2: No), the temperature indicated by the detection value acquired by the process of S1 is the second threshold value that is the higher threshold value. It is confirmed whether or not this is the case (S4).

  As a result of checking by the process of S4, when the water level is equal to or higher than the second threshold (S4: Yes), it is determined that the water is sufficiently recovered, and the water supply electromagnetic valve 89 is closed (S5), This water supply electromagnetic valve opening / closing process is terminated. When the water supply electromagnetic valve 89 is opened by the process of S5, the spraying of water from the nozzle 83b is stopped.

  On the other hand, when the water level is less than the second threshold value as a result of the confirmation in S4 (S4: No), nothing is performed, that is, the water supply electromagnetic valve 89 is maintained in the open / closed state. The supply solenoid valve opening / closing process is terminated.

  According to this water supply electromagnetic valve opening / closing process, the opening / closing of the water supply electromagnetic valve 89 is configured to be controlled in accordance with the value detected by the water level sensor SE8. Therefore, water can be sprayed as necessary to the supply air before flowing into the downstream condenser 113.

  Further, according to the water supply electromagnetic valve opening / closing process, the water supply electromagnetic valve 89 is controlled to open / close, that is, the spray of water from the nozzle 83b is controlled according to the detection value by the water level sensor SE8. Control for improvement can be easily performed.

  In addition, while the process of S1 in the water supply electromagnetic valve opening / closing process described above corresponds to the water recoverability grasping means in the present invention, the processes of S2, S3, S4, and S5 correspond to the injection control means in the present invention. .

  As described above, according to the fuel cell system 100 of the present embodiment, water is sprayed (sprayed) in the form of mist on the supply air before flowing into the downstream condenser 113. Therefore, the supply air can be cooled to the ambient temperature or less by the latent heat of water evaporation and then flowed into the downstream condenser 113, and the supply air thus cooled can act as a cooling medium. Therefore, the water condensing capacity in the downstream condenser 113 can be increased, and the recoverability of the liquid water in the downstream condenser 113 can be improved.

  Therefore, even in a high temperature environment where the recoverability of liquid water by the condenser (heat exchanger) tends to be low, by improving the recoverability of water by the downstream condenser 113, the fuel cell stack 40 Moisture can be sufficiently recovered from the exhausted exhaust and returned to the water tank 82.

  Therefore, the amount of water in the water tank 82 decreases excessively, and the amount of liquid water supplied from the nozzle 83a to the fuel cell stack 40 via the water supply path 81c is insufficient to cool or humidify the fuel cell stack 40. Can be prevented. As a result, a decrease in power generation efficiency of the fuel cell stack 40 due to insufficient cooling and humidification is prevented.

  As described above, the present invention has been described based on the embodiments, but the present invention is not limited to the above-described embodiments, and various improvements and modifications can be easily made without departing from the spirit of the present invention. It can be guessed.

  For example, in the said embodiment, the upstream condenser 112 and the downstream condenser 113 were each comprised as a separate condenser. Instead, the inside of one condenser is separated into two sections, and the outside air introduction part is introduced from the section located on the outlet side of the exhaust path (that is, downstream of the exhaust path) among the two sections. You may comprise.

  In the above embodiment, the detection value of the water level sensor SE8 is used as an index indicating the recoverability of the liquid water, but the estimated recovery of the liquid water is performed by the recovery amount estimation means based on the balance of the moisture amount in the system. The amount may be calculated, and the calculated estimated recovery amount may be used as an index indicating the recoverability of liquid water.

  For example, the exhaust temperature detected by a condenser exhaust temperature sensor (not shown) provided between the downstream condenser 113 and the filter 114 in the air discharge path 111 and the amount of air taken from outside the system The estimated water recovery amount can be calculated from (that is, the air supply amount) and the value can be used as an index indicating the recoverability of the liquid water.

  In this case, when the calculated estimated recovery amount is lower than the predetermined amount, control may be performed so that the water supply electromagnetic valve 89 is opened. The predetermined amount may be the amount of water sprayed from the nozzle 83a (that is, the amount of water supplied to the fuel cell stack 40) or a value obtained by adding a predetermined offset to the amount of water.

  In this way, the control for improving the recoverability of liquid water by using the estimated recovery amount calculated based on the balance of the amount of water in the system as an index indicating the recoverability of the liquid water is predicted control. (Prospect control).

  Further, instead of the detection value of the water level sensor SE8, a value representing the amount of water in the water tank 82, such as the weight of the water tank 82, may be used as an index indicating the recoverability of liquid water.

  In the above embodiment, the water sprayed on the supply air before flowing into the downstream condenser 113 (that is, the water sprayed from the nozzle 83b) and the fuel cell stack 40 are cooled and humidified. For this reason, both the water sprayed (that is, the water sprayed from the nozzle 83a) is supplied from the same water tank 82, but the water sprayed from the nozzle 83b and the water sprayed from the nozzle 83a. The water may be supplied from a dedicated water tank. In addition, by using the configuration in which the water tank 82 is shared as the water supply source as in the above embodiment, the recoverability of the liquid water can be improved while suppressing an increase in the size of the system.

  Moreover, in the said embodiment, although it was set as the structure using two threshold values, a 1st threshold value and a 2nd threshold value, as a threshold value compared with the water level which the detection value by water level sensor SE8 shows, You may comprise so that opening and closing of the water supply electromagnetic valve 89 may be controlled according to whether it is more than a threshold value or less. Or the structure which controls opening and closing of the water supply electromagnetic valve 89 using two or more threshold values may be sufficient.

It is a block diagram showing one embodiment of a fuel cell system which is a fuel cell system of the present invention. (A) is a top view schematically showing the fuel cell stack, and (b) is a top view schematically showing cell modules constituting the fuel cell stack. (A) is the front view which looked at the cell module from the air electrode side, (b) is the front view which looked at the cell module from the fuel electrode side. (A) is IVa-IVa arrow principal part sectional drawing of Fig.3 (a), (b) is arrow principal part sectional drawing of Fig.3 (a). (A) is the front view which looked at the air electrode side collector from the separator main body side, (b) is the side view seen from the Vb direction in (a). It is a flowchart which shows the supply air temperature adjustment process performed in a control apparatus. It is a block diagram which shows the structure of the conventional direct fountain type fuel cell system.

Explanation of symbols

10 Unit cell (fuel cell)
11 solid polymer electrolyte membrane 12 air electrode 13 fuel electrode 40 fuel cell stack (fuel cell)
50 Hydrogen supply system (fuel gas supply means)
60 Air supply system (oxidant gas supply means)
63 Air supply path (air supply path)
80 Water supply system (first water supply means, water recovery means, second water supply means)
81a Water conduit (water recovery means)
81b Water conduit (water recovery means)
81c Water supply channel (first water supply means)
81e Water supply channel (second water supply means)
82 Water tank (water storage means)
100 Fuel cell system 111 Air discharge path (exhaust path)
112 Upstream condenser (upstream heat exchanger)
112a Fan 113 for heat dissipation Downstream condenser (downstream heat exchanger)
SE8 Water level sensor (water storage detection means)

Claims (4)

A fuel cell comprising a solid polymer electrolyte membrane and a fuel electrode and an air electrode sandwiching the solid polymer electrolyte membrane from both sides;
Fuel gas supply means for supplying fuel gas to the fuel electrode;
Oxidant gas supply means for supplying supply air taken from outside the system through an air intake port to the air electrode through an air supply path at normal pressure;
Water storage means for storing liquid water;
First water supply means for spraying liquid water stored in the water storage means in a mist to supply the liquid water to the air electrode;
The fuel cell is located on the fuel cell side of the exhaust path for leading the exhaust gas discharged from the air electrode to the outside of the system, and moisture is condensed from the exhaust gas by liquid cooling by heat exchange and separated into liquid water. An upstream heat exchanger,
A downstream side that is located on the outlet side of the exhaust path from the upstream heat exchanger and that is located on the supply path, and that condenses moisture from the exhaust by cooling the exhaust by heat exchange and separates it as liquid water A heat exchanger,
Water recovery means for recovering liquid water from the upstream heat exchanger and the downstream heat exchanger and returning it to the water storage means;
And a second water supply means for injecting liquid water in the form of a mist from the downstream heat exchanger in the air supply path toward the air intake side. Water recoverability grasping means for obtaining an index indicating the recoverability of liquid water by the water recovery means;
2. The fuel cell system according to claim 1, further comprising injection control means for controlling water injection by the second water supply means in accordance with the index acquired by the water recoverability grasping means. A water storage amount detecting means for detecting the amount of liquid water stored in the water storage means,
3. The fuel cell system according to claim 2, wherein the water recoverability grasping unit acquires the water storage amount detected by the water storage amount detection unit as an index indicating the recoverability of the liquid water. A recovery amount estimation means for calculating an estimated recovery amount of liquid water by the water recovery means, based on a moisture balance in the system;
3. The fuel cell system according to claim 2, wherein the water recoverability grasping means obtains the estimated recovery amount of liquid water calculated by the recovery amount estimation means as an index indicating the recoverability of the liquid water. .

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