JP2008004309A - Fuel cell device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent temperature drop in the vicinity of a reaction gas inlet in cooling by the evaporation latent heat of water supplied to an electrode together with reaction gas. <P>SOLUTION: Water is added to an air supply passage 37 supplying air to a fuel cell 1 through a water supply passage 59. A part of air is supplied from the air supply passage 37 through an air inlet manifold 19 at the upstream end of an air passage 3, and the remaining air is supplied from an intermediate inlet manifold 49 in the intermediate position of the air passage 3 through an air branch passage 47 branching from the air supply passage 37. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell apparatus that supplies water together with a reaction gas to an electrode of a fuel cell, and cools it by generating latent heat of vaporization of water as well as power generation.

  In general, a fuel cell is a device that directly converts a chemical energy of a fuel into electric energy by electrochemically reacting a fuel gas such as hydrogen as a reaction gas and an oxidant gas such as air.

  Such a fuel cell device requires a function of cooling the ionic conductivity of the electrolyte and the heat generated by the power generation. For example, in many polymer membranes used as an electrolyte typified by Nafion (trade name of DuPont), ionic conductivity is ensured in a wet state of the electrolyte. For this reason, the cathode gas and anode gas, which are reaction gases used in the fuel cell, are used in a humidified state.

  In addition, the fuel cell generates heat during power generation. For cooling at that time, cooling water is generally flowed into a part called a bipolar plate that separates the cathode gas and the anode gas.

On the other hand, as described in Patent Document 1 below, a fuel cell that performs humidification and cooling by latent heat of vaporization by directly mixing liquid water into a reaction gas supplied to the fuel cell and evaporating it inside the fuel cell. It has been known.
Japanese Patent Laid-Open No. 2001-210348

  By the way, in the fuel cell device that performs the above-described humidification and cooling by latent heat of vaporization, the temperature rise is observed along the flow of the reaction gas so that the water vapor vaporized by the heat generated by the power generation is saturated.

  Such a temperature rise near the reaction gas inlet is because the utilization rate of the reaction gas is extremely low when viewed locally, so that the water vapor pressure is low, and the temperature is correspondingly lower than that near the reaction gas outlet. . For this reason, as shown in FIG. 6, the fuel cell cooled by the latent heat of vaporization indicated by the broken line B has a lower temperature portion than the general fuel cell cooled by the cooling water indicated by the solid line A.

  In the portion where the temperature is low, the catalytic activity at the electrode is low, so the power generation performance is reduced. Due to the decrease in the power generation performance, the current density at the low temperature portion near the reaction gas inlet is decreased, which causes a problem that the current-voltage characteristic of the fuel cell is degraded.

  Therefore, the present invention aims to prevent a temperature drop in the vicinity of the reaction gas inlet when cooling is performed by vaporization heat of water supplied to the electrode together with the reaction gas.

  The present invention provides a fuel cell device in which water is supplied together with a reaction gas to an electrode of a fuel cell, and cooling is performed by latent heat of vaporization of water as well as power generation. A reaction gas inlet into which the reaction gas flows is provided, a reaction gas outlet from which the reaction gas is discharged is provided at the other end, and a part of the reaction gas necessary for power generation of the fuel cell is provided at the reaction gas inlet. The main feature is that the other part of the reaction gas is supplied to an intermediate portion of the reaction gas flow path between the reaction gas inlet and the reaction gas outlet simultaneously with the supply with the water.

  According to the present invention, the reaction gas necessary for power generation of the fuel cell is divided and supplied to the reaction gas inlet at the upstream end of the reaction gas channel and the middle part of the reaction gas channel. The local reaction gas supply amount in the vicinity of the inlet is relatively reduced to increase the utilization rate of the reaction gas, and the water vapor partial pressure is increased to prevent a temperature drop in the vicinity of the reaction gas inlet.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram of a fuel cell device showing a first embodiment of the present invention. In FIG. 1, a bipolar plate (also referred to as a separator) 5 which is one of the components of the fuel cell 1 is shown as a plan view. As shown in FIG. 1, the bipolar plate 5 has air as a reaction gas channel through which a reaction gas (here, oxygen-containing air) flows in a power generation region including electrodes 11 and 13 shown in FIG. A flow path 3 is formed.

  FIG. 2 is a cross-sectional view showing a part of the above-described fuel cell 1 and corresponding to the cross section taken along line AA of FIG. 1. The fuel cell 1 here is a solid polymer electrolyte using a solid polymer as an electrolyte It is a fuel cell.

  The fuel cell 1 includes an electrolyte membrane 9 made of a solid polymer membrane located in the center of one battery cell 7 and two electrodes 11 disposed on both surfaces of the electrolyte membrane 9 so as to sandwich the electrolyte membrane 9. , 13 and bipolar plates 5 and 15 arranged outside thereof to form a partition wall between the battery cells 7, and a fuel cell stack is usually constructed by stacking a plurality of these battery cells 7. is doing.

  The electrolyte membrane 9 is formed as a proton conductive membrane from a solid polymer material such as a fluorine resin. The two electrodes 11, 13 on both surfaces of the electrolyte membrane 9 are made of platinum, carbon cloth coated with carbon fine particles carrying a catalyst made of platinum and other metals, or carbon paper, and a coated surface on which the catalyst exists. Is in contact with the electrolyte membrane 9.

  The bipolar plates 5 and 15 are made of a dense carbon material that is impermeable to gas. One bipolar plate 5 is formed on the surface facing the electrode 11 with the air flow path 3 shown in FIG. The other bipolar plate 15 has a hydrogen flow path 17 through which hydrogen flows as a fuel gas on the surface facing the electrode 13.

  As shown in FIG. 1, the fuel cell component including the bipolar plate 5 has a rectangular shape that is long in the left-right direction in FIG. 1, and forms the air flow path 3 along the longitudinal direction thereof. . Then, an air inlet manifold 19 serving as a reaction gas inlet penetrating the fuel cell 1 is provided along the direction orthogonal to the paper surface at the left end in FIG. 1, that is, the stacking direction of each component of the fuel cell 1. An air outlet manifold 21 serving as a reaction gas outlet penetrating the fuel cell 1 is provided along a direction orthogonal to the paper surface at the right end portion, and each of the air inlets and the outlet manifolds 19 and 21 is connected to the air flow described above. It communicates by way 3.

  That is, the air flowing through the air inlet manifold 19 is distributed and supplied to the air flow path 3 of each battery cell 7.

  Similarly, hydrogen inlet and outlet manifolds 23 and 25 are provided adjacent to the air inlet and outlet manifolds 19 and 21, respectively, in a direction perpendicular to the paper surface in FIG. And this hydrogen is also distributed and supplied to the hydrogen flow path 17 of each battery cell 7 like the above-mentioned air.

  Here, as shown in FIG. 1, the air flow path 3 in the present embodiment is divided into two, an upstream flow path 27 and a downstream flow path 29, and an intermediate region 31 is provided between them. . Further, a dispersion region 33 is provided between the upstream flow path 27 and the air inlet manifold 19, and a collecting region 35 is provided between the downstream region 29 and the air outlet manifold 21.

  As shown in FIG. 1, an air supply passage 37 as a reaction gas supply passage is connected to the air inlet manifold 19, while an air discharge passage 38 is connected to the air outlet manifold 21. The air supply passage 37 is provided with a compressor 41 that sucks and discharges outside air from the intake port 39, while the air discharge passage 38 is provided with a pressure regulating valve 43, and the air taken in from the intake port 39 is supplied to the fuel cell 1. The controller 45 controls the compressor 41 and the pressure regulating valve 43 so that the air amount and the pressure correspond to the operating load.

  The air supply passage 37 is provided by branching an air branch passage 47 as a reaction gas branch passage in the middle. The air branch passage 47 communicates with the intermediate region 31 and is connected between the reaction gas inlet and the reaction gas outlet. It is connected to an intermediate inlet manifold 49 corresponding to a midway portion of the reaction gas flow path therebetween. Similar to the air inlet and outlet manifolds 19 and 21, the intermediate inlet manifold 49 is provided so as to penetrate in a direction orthogonal to the paper surface in FIG. 1, and the air branched into the intermediate region 31 of each battery cell 7 is respectively provided. Distribute supply.

  A pressure sensor 51 is provided in the air supply passage 37 between the air branch passage 47 and the compressor 41, and a pressure regulating valve 53 and a pressure sensor 55 are provided in the air branch passage 47 from the upstream side thereof. The detected values 51 and 55 are input to the controller 45 described above, and the pressure regulating valve 53 is controlled by the controller 45.

  A water supply passage 59 for supplying liquid phase water by an injector 57 is connected to the air supply passage 37 between the pressure sensor 51 and the air branch passage 47, and the air supply passage 37 passes through the water supply passage 59. Add water.

  The supply source of the water ejected from the injector 57 may be, for example, a tank that stores water condensed with water vapor in the exhaust air flowing through the air exhaust passage 38.

  On the other hand, a hydrogen supply passage 65 is connected to the hydrogen inlet manifold 23, and a hydrogen tank 67 that stores hydrogen at high pressure from the upstream side, a pressure regulating valve 69 controlled by the controller 45, hydrogen Ejectors 71 that are circulation devices are sequentially installed. Further, one end of the hydrogen circulation passage 73 is connected to the hydrogen outlet manifold 25, and the other end of the hydrogen circulation passage 73 is connected to the above-described ejector 71. The ejector 71 causes the discharged hydrogen flowing through the hydrogen circulation passage 73 to be re-hydrogenated. Circulate to supply to the inlet manifold 23.

  Next, the operation will be described. The compressor 41 takes in air from the intake port 39. At this time, the controller 45 sets the detected value of the pressure sensor 51 so that the intake air becomes the air amount and air pressure corresponding to the operating load of the fuel cell 1. The compressor 41 and the pressure regulating valve 43 are controlled while taking in.

  Then, water from the injector 57 is supplied through the water supply passage 59 to the air discharged to the air supply passage 37 by the compressor 41. As a result, the reaction gas is sent to the fuel cell 1 in a gas-liquid two-phase flow state, and a part is supplied from the air inlet manifold 19 to the upstream power generation unit 61 corresponding to the upstream flow path 27. The other part is supplied from the intermediate inlet manifold 49 to the downstream power generation unit 63 corresponding to the downstream channel 29 through the air branch passage 47.

  At this time, the air supplied from the intermediate inlet manifold 49 to the intermediate region 31 is mixed with unused air in the upstream power generation unit 61 and supplied to the downstream power generation unit 63, and then unused air is supplied from the air outlet manifold 21. It is discharged to the air discharge passage 38.

  On the other hand, the controller 45 controls the pressure regulating valve 69 so that the hydrogen from the hydrogen tank 67 becomes the amount of circulating hydrogen corresponding to the operating load of the fuel cell 1 and the supply pressure of the ejector 71. At this time, hydrogen is introduced into the fuel cell 1 from the hydrogen inlet manifold 23, and unused hydrogen discharged from the hydrogen outlet manifold 25 is mixed with hydrogen from the hydrogen tank 67 by the ejector 71 and circulated.

  At this time, the controller 45 adjusts the pressure sensor so that the amount of air supplied from the air inlet manifold 19 to the upstream power generation unit 61 and the amount of air supplied to the intermediate inlet manifold 49 through the air branch passage 47 are equal to each other. The opening degree of the pressure regulating valve 53 is adjusted while referring to the output value 55. That is, the controller 45, the pressure regulating valve 53, and the pressure sensor 55 constitute a reaction gas flow rate adjusting means.

  Here, if the fuel cell 1 is operated at an air utilization rate of 67%, the air taken from the intake port 39 is 1.5 times the theoretically required air amount. Thereafter, the upstream power generation unit 61 and the downstream power generation unit 63 are introduced with 0.75 times as much air as theoretically necessary from the air inlet manifold 19 and the intermediate inlet manifold 49.

  In this case, if only the upstream power generation unit 61 that is a half region of the entire power generation unit is viewed, in this embodiment, the amount of air supplied to the upstream power generation unit 61 is 1.5 times the theoretically required air amount. . On the other hand, when the entire amount of air is supplied from the air inlet manifold to the half region of the entire power generation unit in the same manner as described above, it is 3.0 times the theoretically required amount of air.

  For this reason, since water vapor | steam is generated according to the heat_generation | fever at the time of electric power generation, although it does not change a lot, the amount of reaction gas (here air content) other than water vapor | steam is smaller in this embodiment compared with the past. . For this reason, in the present embodiment, the steam partial pressure of the upstream power generation unit 61 is higher than the conventional one, and the steam pressure reaches a temperature at which the steam pressure is in a saturated state. Therefore, the temperature of the upstream power generation unit 61 is the solid line in FIG. As shown by C, it becomes higher than the conventional one-dot chain line D.

  As described above, according to the present embodiment, the air branch passage 47 obtained by branching the air supply passage 37 connected to the inlet of the air flow path 3 is connected to the intermediate inlet manifold 49 in the middle of the air flow path 3 to react. Since the gas air is divided and supplied to the air inlet manifold 19 and the intermediate inlet manifold 49, the local air utilization rate in the air flow path 3 near the air inlet manifold 19 can be increased. In addition, the power generation performance of the fuel cell 1 can be improved by preventing a temperature drop of the power generation unit near the inlet of the air inlet manifold 19.

  In the above-described embodiment, the intermediate inlet manifold 49 is set at the center position in the longitudinal direction of the air flow path 3 and the air branch passage 47 is connected to this center position. However, this connection position is limited to the center position. Is not to be done.

  For example, as a second embodiment of the present invention, the intermediate inlet manifold 49 is arranged upstream of the longitudinal center position of the air flow path 3, so that the temperature of the upstream side is increased as shown by the solid line E in FIG. The temperature of the lower part can be made higher.

  In this case, the air flow rate is changed according to the power generation area (electrode area) of the upstream power generation unit 61 and the power generation area (electrode area) of the downstream power generation unit 63. That is, when the intermediate inlet manifold 49 is arranged upstream from the longitudinal center position of the air flow path 3 as described above, the electrode area of the upstream power generation unit 61 is smaller than the electrode area of the downstream power generation unit 63, but it is reduced. Accordingly, the air supply amount to the air inlet manifold 19 is made smaller than the air supply amount to the intermediate inlet manifold 49. As the air supply amount decreases, as shown by the solid line E, the temperature on the upstream side is higher than that of the solid line D and rapidly increases.

  FIG. 4 is a plan view of a bipolar plate 5A corresponding to the bipolar plate 5 described above according to the third embodiment of the present invention. In this embodiment, each of the upstream flow path 27A in the upstream power generation section 61A of the fuel cell 1A flows through the downstream flow path 29A in the downstream power generation section 63A so that the air flows in the middle region 31A. The flow paths 27A and 29A are adjacently arranged in parallel.

  In this case, the ratio of the length of the long portion in the left-right direction (longitudinal direction) in FIG. 1 of the upstream power generation portion 61 and the downstream power generation portion 63 in FIG. 1 to the length of the short length portion in the vertical direction in FIG. However, as long as the length in the left-right direction is long enough to exceed 2: 1, the area of the non-power generation portion surrounding the upstream power generation unit 61A and the downstream power generation unit 63A is reduced compared to the example of FIG. The fuel cell 1A can be made compact.

  FIG. 5 is a plan view of a bipolar plate 5B corresponding to the bipolar plate 5 described above, showing a fourth embodiment of the present invention. In this embodiment, as in the third embodiment shown in FIG. 4, the downstream flow path 29B in the downstream power generation unit 63B is placed in the middle of the upstream flow path 27B in the upstream power generation unit 61B of the fuel cell 1B. These flow paths 27B and 29B are adjacently arranged in parallel so that the air flows back in the region 31B. Here, the downstream flow path 29B is arranged on both sides of the upstream flow path 27B. Provided.

  Thus, both sides of the upstream power generation unit 61B having a low temperature are enclosed by the downstream power generation unit 63B having a high temperature, and heat is radiated from the upstream power generation unit 61B having a lower temperature than the downstream power generation unit 63B to the outside of the fuel cell. Can be reduced.

  4 and 5, the same components as those in FIG. 1 are indicated by adding alphabets A and B after the numbers in FIG. 4 and 5, only a part of the air supply passage 37, the air branch passage 47, the hydrogen supply passage 65, and the hydrogen circulation passage 73 in FIG. 1 are shown. 1 is the same connection form.

  As a fifth embodiment of the present invention, during the warm-up operation of the fuel cells 1, 1A, 1B, the amount of air supplied to the upstream power generation units 61, 61A, 61B is reduced as compared with the steady operation. This utilizes the point that the temperature increase of this part can be achieved by reducing the amount of air in the upstream power generation unit 61 in the first embodiment. Therefore, this case is effective when it is desired to quickly raise the temperature during the warm-up operation, and the warm-up operation time can be shortened.

  In addition, although each above-mentioned embodiment showed the method of utilizing vaporization latent heat only by the air side, it does not deny performing with respect to what uses vaporization latent heat on the hydrogen side. In the present embodiment, the method of supplying liquid phase water for vaporization has been described as a method of supplying using the injector 57 outside the fuel cell 1, but other methods are not denied. .

  In the above-described embodiment, the air branch passage 47 is branched from the air supply passage 37. However, two air supply sources such as the compressor 41 are installed, and air is supplied to the air inlet manifold 19 and the intermediate inlet manifold 49. May be supplied separately.

1 is an overall configuration diagram of a fuel cell device showing a first embodiment of the present invention. It is sectional drawing equivalent to the AA sectional view of FIG. 1 which shows a part of fuel cell. It is explanatory drawing which shows the temperature change along an air flow path by comparing a prior art example and this embodiment. It is a top view of the bipolar plate which shows the 3rd Embodiment of this invention. It is a top view of the bipolar plate which shows the 4th Embodiment of this invention. It is explanatory drawing which shows the temperature change along an air flow path by comparing cooling water cooling and vaporization latent heat cooling.

Explanation of symbols

1, 1A, 1B Fuel cell 3, 3A, 3B Air flow path (reactive gas flow path)
11, 13 Electrode 19, 19A, 19B Air inlet manifold (reactive gas inlet)
21, 21A, 21B Air outlet manifold (reactive gas outlet)
37 Air supply passage (reactive gas supply passage)
45 Controller (reaction gas flow rate adjusting means)
47 Air branch passage 49 Intermediate inlet manifold (part of the reaction gas flow path between the reaction gas inlet and the reaction gas outlet)
53 Pressure regulating valve (reaction gas flow rate adjusting means)
55 Pressure sensor (reaction gas flow rate adjusting means)
61, 61A, 61B Upstream flow path of air flow path 63, 63A, 63B Downstream flow path of air flow path

Claims (9)

  In a fuel cell device that supplies water together with a reaction gas to an electrode of a fuel cell and cools by generating latent heat of vaporization of water together with power generation, the reaction gas flows into one end of a reaction gas channel through which the reaction gas flows in the electrode The reaction gas inlet is provided with a reaction gas outlet for discharging the reaction gas at the other end, and a part of the reaction gas necessary for power generation of the fuel cell is supplied to the reaction gas inlet together with the water. At the same time, another part of the reaction gas is supplied to an intermediate portion of the reaction gas flow path between the reaction gas inlet and the reaction gas outlet.   2. The fuel cell device according to claim 1, wherein another part of the reaction gas is supplied together with the water to an intermediate portion of the reaction gas flow path between the reaction gas inlet and the reaction gas outlet. .   The fuel cell device according to claim 1 or 2, wherein a reaction gas supply passage for supplying the reaction gas to the reaction gas inlet is connected and a reaction gas branch passage provided by branching the reaction gas supply passage is provided. A fuel cell device connected to an intermediate portion of the reaction gas flow path.   4. The fuel cell device according to claim 1, wherein an intermediate portion of the reaction gas flow path is located upstream of a central position in the reaction gas flow direction in the reaction gas flow path. A fuel cell device.   5. The fuel cell device according to claim 1, wherein the reaction gas inlet and the reaction gas flow path are arranged so that the reaction gas flows back at a midpoint of the reaction gas flow path. As a configuration having an upstream flow path connecting a midway part and a downstream flow path connecting the midway part and the reactive gas outlet, the upstream flow path and the downstream flow path are arranged adjacent to each other in parallel. A fuel cell device.   6. The fuel cell device according to claim 5, wherein the downstream flow path of the reaction gas flow path is disposed on both sides of the upstream flow path of the reaction gas flow path.   7. The fuel cell device according to claim 1, wherein a flow rate of the reaction gas supplied from the reaction gas inlet to the reaction gas channel and a reaction gas supplied to an intermediate portion of the reaction gas channel. A fuel cell device comprising a reactive gas flow rate adjusting means for adjusting the flow rate of the fuel gas.   8. The fuel cell device according to claim 7, wherein the reactive gas flow rate adjusting means includes an electrode area between the reactive gas inlet and an intermediate part of the reactive gas channel, an intermediate part of the reactive gas channel, and the A fuel cell device, wherein a flow rate of a reaction gas is changed according to an electrode area between the reaction gas outlet and the reaction gas outlet.   9. The fuel cell device according to claim 1, wherein the flow rate of the reaction gas supplied to the reaction gas inlet during the warm-up operation of the fuel cell is reduced as compared with the steady operation. A fuel cell device.

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