JP6015525B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  When the operation of the fuel cell is stopped, generally, a process (also referred to as “scavenging process” or “scavenging operation”) in which the remaining water remaining in the fuel cell is discharged by the scavenging gas is performed. For example, Patent Document 1 discloses that after the fuel cell is started and stopped, the generated water inside the anode electrode and the cathode electrode is discharged by scavenging at a larger flow rate than the deterioration countermeasure scavenging when the fuel cell falls below a predetermined temperature. It is described to do. Patent Document 2 describes that the inside of the fuel cell is scavenged at a large flow rate immediately after power generation is stopped, and then scavenging at a low flow rate is performed after scavenging is stopped for a predetermined time. Patent Document 3 discloses that a water droplet generated in an oxidant gas flow channel is scavenged for a short time with a large flow rate of oxidant gas, and then a solid polymer electrolyte membrane is formed with a good startability using a dry small flow rate of oxidant gas. It is described that scavenging is performed for a longer time than the short-time scavenging in order to obtain a proper water content.

JP 2009-252593 A JP 2007-073328 A JP 2007-115581 A

  Here, a channel having a structure in which a plurality of narrow channels (hereinafter referred to as “comb channel”) is formed at the outlet of the groove-shaped gas channel formed in the separator may be applied. . When the above scavenging process is applied to a gas channel having a comb channel, there are the following problems.

  When the scavenging process of Patent Document 1 is applied, there is no problem if the stagnant water is completely removed, but scavenging for a long time at a large flow rate is required to completely remove the stagnant water. However, due to the system configuration, the time that can be set for the scavenging process may be limited to some extent, and if the stagnant water cannot be completely removed by the scavenging process for the set scavenging time, the comb flow path There is a possibility that water remaining in the vicinity moves and stays in the comb tooth channel.

  Even when the scavenging process of Patent Document 2 is applied, scavenging for a long time with a small flow rate is necessary to remove the stagnant water, and the stagnant water can be completely removed by the scavenging process with the set scavenging time. If not, water remaining near the comb channel may move and stay in the comb channel.

  The scavenging process of Patent Document 3 is to perform scavenging for a long time with a small flow rate of an oxidant gas that is dry to make the solid polymer electrolyte membrane have a good starting water content. It is not supposed to be removed. For this reason, similarly to the above-mentioned Patent Documents 1 and 2, water remaining near the comb channel may move and stay in the comb channel.

  The stagnant water in the comb-tooth flow path may be blocked by freezing and may not be able to start below freezing. Therefore, the retained water in the comb channel can be removed without performing a long-time scavenging process for removing all the accumulated water on the gas channel in which the comb channel is formed at the outlet of the gas channel. It was desired to remove. In addition, conventional fuel cells and fuel cell systems have been desired to be reduced in size, reduced in cost, resource-saving, easy to manufacture, and improved in usability.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to one aspect of the present invention, a fuel cell system is provided. The fuel cell system includes a fuel cell having a fuel cell including a separator in which a groove-like gas flow path is formed; a scavenging gas supply unit that supplies a scavenging gas to the gas flow path; and a scavenging gas supply unit. A scavenging control unit that performs the scavenging operation. The gas channel includes a gas outlet channel having a comb-shaped channel connected to the gas channel outlet, and an upstream gas channel connected to the upstream side of the gas outlet channel. The scavenging control unit supplies the scavenging gas from the scavenging gas supply unit at a first scavenging gas flow rate and a first scavenging time when stopping the operation of the fuel cell, thereby A first scavenging operation is performed to discharge water staying in the gas passage to the outside of the gas flow path. The second gas scavenging gas flow rate lower than the first gas scavenging gas flow rate after execution of the first gas scavenging operation, and the gas outlet flow channel with water remaining in the upstream gas flow channel remaining. The scavenging gas is supplied from the scavenging gas supply unit at a second scavenging gas amount for discharging water remaining in the gas outlet passage to the outside and a second scavenging time shorter than the first scavenging time. The second scavenging operation to be supplied is executed. According to the fuel cell system of this aspect, the water staying in the gas outlet channel having the comb-shaped channel connected to the gas channel outlet can be discharged in a shorter time and with less energy compared to the conventional method, so that it stays. It is possible to suppress the blockage of the gas outlet channel due to water freezing.

(2) In the fuel cell system, the second scavenging gas flow rate is a flow rate at which a differential pressure generated in the upstream gas flow path is smaller than a differential pressure required for water movement in the upstream gas flow path. It is good. According to the fuel cell system of this aspect, it is possible to suppress the movement of water staying in the upstream gas flow path to the gas outlet flow path so that the water staying in the upstream gas flow path does not move. is there.

(3) In the fuel cell system according to the above aspect, the gas outlet channel is configured such that a difference in pressure generated in the gas outlet channel due to the second scavenging gas flow rate is required for movement of water in the gas outlet channel. It is good also as a structure which becomes larger than a pressure. According to the fuel cell system of this aspect, it is possible to discharge the water staying in the gas outlet passage to the outside of the gas outlet passage without moving the water staying in the upstream gas passage.

(4) In the fuel cell system according to the above aspect, the structure is configured such that the total cross-sectional area of the groove-shaped flow path included in the gas outlet flow path is a total break of the groove-shaped flow path included in the upstream gas flow path. It is good also as a structure smaller than an area. According to this structure, the differential pressure generated in the gas outlet channel by the second scavenging gas flow rate can be made larger than the differential pressure required for the movement of water in the gas outlet channel.

(5) In the fuel cell system of the above aspect, the structure may be a structure in which the entire width of the gas outlet channel is smaller than the entire width of the upstream gas channel. Also with this structure, it is possible to make the differential pressure generated in the gas outlet channel by the second scavenging gas flow rate larger than the differential pressure required to move water in the gas outlet channel.

  The present invention can be implemented in various forms other than the above. For example, it can be realized in the form of a control method of the fuel cell system, a scavenging operation method of the fuel cell, and the like.

It is explanatory drawing which shows schematic structure of the fuel cell system as one Embodiment of this invention. It is explanatory drawing which shows schematic structure of the anode side separator of a fuel cell. It is explanatory drawing shown about the scavenging operation for the stagnant water removal performed at the time of the driving | operation stop of a fuel cell system. It is explanatory drawing shown about the stagnant water in 2nd scavenging driving | operation.

A. Embodiment:
FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel cell system as an embodiment of the present invention. The fuel cell system 100 includes a fuel cell 10 that generates power, a fuel gas system 30 that supplies fuel gas to the fuel cell 10 and discharges the fuel gas from the fuel cell 10, and supplies an oxidizing gas to the fuel cell 10. And an oxidizing gas system 50 for discharging the oxidizing gas from the fuel cell 10, a cooling system 60 for cooling the fuel cell 10, and a control unit 70 for controlling the entire fuel cell system 100. In the present embodiment, the fuel cell system 100 is mounted on a vehicle.

  The fuel cell 10 is a polymer electrolyte fuel cell and has a stack structure in which a plurality of fuel cells 12 are stacked. When the fuel cell 10 is supplied with hydrogen gas as a fuel gas and air as an oxidizing gas, the fuel cell 10 generates power by an electrochemical reaction. The fuel cell 12 includes a membrane electrode assembly (not shown), an anode of the membrane electrode assembly (which is also referred to as a “hydrogen electrode” where hydrogen gas is supplied) and a cathode (which is referred to as “air” which is supplied with oxidizing gas). It is composed of a separator (not shown) that is sandwiched from both sides.

  FIG. 2 is an explanatory diagram showing a schematic configuration of the anode separator of the fuel battery cell. FIG. 2A shows a schematic plan view of the anode separator 20a viewed from the membrane electrode assembly side, and FIG. 2B shows an enlarged range surrounded by a circle in FIG. 2A. As shown in FIG. 2A, a hydrogen gas supply port 21, a hydrogen gas introduction channel 22, and a hydrogen gas channel 24 are provided on the surface of the anode separator 20a on the side in contact with the membrane electrode assembly. In addition, an anode off-gas outlet channel 26 and an anode off-gas outlet 27 are formed.

  The hydrogen gas supply port 21 is a through-hole penetrating in the thickness direction of the anode-side separator 20a. The hydrogen gas supply port 21 is a flow path for flowing hydrogen gas supplied from the outside of the fuel cell 10 through the hydrogen supply pipe 41 in the stacking direction of the fuel cells 12 constituting the fuel cell 10 (hereinafter, “ A hydrogen supply manifold "). The anode off gas discharge port 27 is a through-hole penetrating in the thickness direction of the anode separator 20a. The anode off-gas discharge port 27 is a flow path (hereinafter referred to as “flow”) for flowing the anode off-gas discharged from the anode of the fuel cell 12 constituting the fuel cell 10 in the stacking direction of the fuel cell 12 to the outside of the fuel cell 10. , Also referred to as “hydrogen discharge manifold”).

  The hydrogen gas supply port 21 and the hydrogen gas flow path 24 communicate with each other via the hydrogen gas introduction flow path 22. The hydrogen gas introduction flow path 22 has a plurality of groove-shaped section introduction flow paths 22p arranged at equal intervals in the illustrated gravitational direction.

  Hydrogen gas supplied from the outside of the fuel cell 10 flows into the hydrogen gas passage 24 from the hydrogen gas supply port 21 through the hydrogen gas introduction passage 22.

  The hydrogen gas flow path 24 is a so-called serpentine flow path, and is formed such that a plurality of groove-shaped divided flow paths 24p meander on the surface of the anode separator 20a. The plurality of groove-shaped section flow paths 24p are arranged at equal intervals. The hydrogen gas channel 24 is formed such that hydrogen and the anode off-gas flow from the upper side to the lower side (gravity direction) of the anode-side separator 20a while meandering.

  The hydrogen gas flow path 24 and the anode off gas discharge port 27 communicate with each other via the anode off gas outlet flow path 26. The anode off-gas outlet channel 26 has a structure of a comb-shaped channel (comb channel) in which a plurality of groove-shaped segment outlet channels 26p are arranged at equal intervals in the illustrated gravity direction.

  Here, the overall width W2 of the anode off-gas outlet channel 26 is set to be smaller than the overall width W1 of the hydrogen gas channel 24. Further, the total cross-sectional area ΣSp2 of the plurality of segment derivation channels 26p of the anode off-gas derivation channel 26 is set smaller than the total cross-sectional area ΣSp1 of the plurality of segment channels 24p of the hydrogen gas channel 24. Simply, if the width of the anode off-gas outlet channel 26 is reduced with the same number of channels, the sectional area Sp2 of the segment outlet channel 26p determined by the width Wp2 and the depth Lp2 of the segment outlet channel 26p is The sectional area Sp1 of the segment channel 24p determined by the width Wp1 and the depth Lp1 of the segment channel 24p is made smaller, and the total sectional area ΣSp2 of the plurality of segment derivation channels 26p is equal to the plurality of segment channels 24p. Is set to be smaller than the total cross-sectional area ΣSp1. Further, by setting the width Wp2 or the depth Lp2 of the section derivation flow path 26p to be smaller so that the cross sectional area Sp2 of the section derivation flow path 26p is smaller than the cross sectional area Sp1 of the section flow path 24p, the anode The total cross-sectional area ΣSp2 of the plurality of segment derivation channels 26p of the off-gas derivation channel 26 may be set to be smaller than the total cross-sectional area ΣSp1 of the plurality of segment channels 24p of the hydrogen gas channel 24. However, the rib between the flow paths is set to a width that can ensure the strength of the flow path structure.

  In this example, the number n of the section derivation channels 26p is made smaller than the number m (m = 7 in this example) of the section channels 24p (n = 7 in this example), and the width Wp2 of the section derivation channels 26p. And the depth Lp2 is made smaller than the width Wp1 and the depth Lp1 of the section channel 24p, and the sectional area Sp2 of the section derivation path 26p is made smaller than the sectional area Sp1 of the section channel 24p, thereby deriving the anode off-gas. The overall width W2 of the flow path 26 and the total cross-sectional area ΣSp2 of the plurality of section derivation flow paths 26p are set smaller than the overall width W1 of the hydrogen gas flow path 24 and the total cross-sectional area ΣSp1 of the plurality of section flow paths 24p. . Thereby, the flow rate of the anode off gas flowing through the anode off gas outlet channel 26 can be made faster than the flow rates of the hydrogen gas and the anode off gas flowing through the hydrogen gas channel 24. In addition, it is possible to secure a flow path structure having a strength that does not lose against the pressure of a seal line (not shown) passing over the anode off-gas outlet flow path 26.

  The anode off-gas outlet channel 26 and the hydrogen gas channel 24 correspond to the gas outlet channel and the upstream channel of the present invention in this embodiment. Further, the total cross-sectional area ΣSp2 of the plurality of section derivation channels 26p of the anode off-gas derivation channel 26 corresponds to the total cross-sectional area of the groove-like channel included in the gas derivation channel of the present invention in the present embodiment. The total cross-sectional area ΣSp1 of the plurality of divided flow paths 24p of the gas flow path 24 corresponds to the total cross-sectional area of the groove-shaped flow path included in the upstream flow path of the present invention in the present embodiment.

  The anode offgas and water (for example, generated water generated by power generation) discharged from the end of the hydrogen gas passage 24 are led to the anode offgas discharge port 27 through the anode offgas leadout passage 26.

  In the present embodiment, in the anode separator 20a, the plurality of segment derivation flow paths 26p of the anode off gas derivation flow path 26 are formed so that the anode off gas flows in the horizontal direction toward the anode off gas discharge port 27. . Accordingly, in the anode-side separator 20a, the flow direction of the anode off-gas and water from the leading end of the anode off-gas outlet channel 26 to the anode off-gas outlet 27 is a horizontal direction.

  A cooling water passage (not shown) is formed on the surface of the anode separator 20a opposite to the surface on which the hydrogen gas passage 24 is formed.

  Although illustration is omitted, air as an oxidizing gas is supplied to the cathode of the membrane electrode assembly on the surface of the cathode side separator that is in contact with the membrane electrode assembly, similarly to the anode separator 20a. A groove-shaped flow path is formed. However, the flow path for supplying the oxidizing gas may be a porous flow path, and is not particularly limited.

  1 includes a hydrogen tank 31, a shut valve 32, a regulator 33, an injector 34, a gas-liquid separator 35, a circulation pump 36, an exhaust valve 37, a drain valve 38, and piping. 41, 42, 43, 44, 45.

  Hydrogen gas stored in the hydrogen tank 31 is supplied as fuel gas to the anode of the fuel cell 10 via a pipe (hereinafter also referred to as “hydrogen supply pipe”) 41. The shut valve 32, the regulator 33, and the injector 34 adjust the pressure of hydrogen gas and the supply amount of hydrogen gas to the fuel cell 10.

  Exhaust gas from the anode (hereinafter also referred to as “anode offgas piping”) is led to the gas-liquid separator 35 via a pipe (hereinafter also referred to as “anode offgas piping”) 42. The gas-liquid separator 35 separates water contained in the anode off-gas from hydrogen gas that has not been consumed by power generation. The hydrogen gas separated by the gas-liquid separator 35 is circulated to the fuel cell 10 via a pipe (hereinafter also referred to as “hydrogen circulation pipe”) 43, a circulation pump 36 and a hydrogen supply pipe 41.

  A pipe (hereinafter also referred to as “anode offgas exhaust pipe”) 44 is provided between the gas-liquid separator 35 and the circulation pump 36, and an exhaust valve 37 is provided in the anode offgas exhaust pipe 44. ing. The exhaust valve 37 is normally closed, and the anode off gas described above circulates in the fuel cell 10. However, when the concentration of impurities such as nitrogen gas or water vapor contained in the anode off gas increases, the exhaust valve 37 opens at a predetermined timing, and the anode off gas is guided to the diluter 55 via the anode off gas exhaust pipe 44. Then, the fuel cell system 100 is discharged to the outside. As a result, impurities such as nitrogen gas and water vapor are removed from the anode side, and an increase in the impurity concentration on the anode side is suppressed.

  The gas-liquid separator 35 is provided with a pipe (hereinafter also referred to as “drainage pipe”) 45 for discharging the stored water, and the drainage pipe 45 is provided with a drain valve 38. . The drain valve 38 is normally closed, opened according to the amount of water stored in the gas-liquid separator 35, led to the diluter 55 through the drain pipe, and drained to the outside of the fuel cell system 100. The Further, also when the scavenging operation for discharging the water staying in the fuel cell 10 is completed, the drain valve 38 is opened and drainage is performed.

  The oxidizing gas system 50 includes an air cleaner 51, an air compressor 52, a diluter 55, and pipes 53, 54, and 56. The air sucked from the air cleaner 51 is compressed by the air compressor 52 and supplied as an oxidizing gas to the cathode of the fuel cell 10 via the pipe 53. Exhaust gas from the cathode (hereinafter also referred to as “cathode off-gas”) is introduced to the diluter 55 via the pipe 54.

  The diluter 55 mixes the cathode off gas with the anode off gas introduced into the diluter 55 at the predetermined timing described above. That is, the concentration of hydrogen contained in the anode off gas is diluted by the cathode off gas. The exhaust gas discharged from the diluter 55 is discharged out of the fuel cell system 100 through the pipe 56. Further, the water discharged from the gas-liquid separator 35 through the drain pipe 45 to the diluter 55 is discharged along with the exhaust gas through the pipe 56.

  The cooling system 60 includes a radiator 61, a circulation pump 62, and pipes 63 and 64. The pipes 63 and 64 are connected to the fuel cell 10 and the radiator 61. Cooling water flowing in the pipes 63 and 64 circulates between the fuel cell 10 and the radiator 61 by the pressure of the circulation pump 62. For this reason, the heat generated by the electrochemical reaction of the fuel cell 10 is absorbed by the circulating cooling water, and the heat absorbed by the cooling water is radiated by the radiator 61. As a result, the temperature of the fuel cell 10 is maintained at an appropriate temperature.

  The control unit 70 is configured as a microcomputer having a CPU, RAM, ROM, and the like inside, and controls the operation of the fuel cell system 100 by developing a program stored in the ROM and executing it. Operates as a control unit. And the control unit 70 is based on the output request | requirement from a vehicle and the detection state (not shown) by various sensors, The shut valve 32, the regulator 33, the injector 34, the circulation pump 36, the air compressor 52, the exhaust valve 37, the drain valve By outputting a drive signal to 38 and the like, the operation of the fuel cell system 100 and the scavenging operation at the end of the operation are controlled.

  As will be described below, the fuel cell system 100 of the present embodiment is formed in the anode of each fuel cell 12, specifically, the membrane electrode assembly and the anode-side separator 20a when the operation is stopped. It has a feature in the scavenging operation for removing the remaining water remaining in the groove-like flow paths (hydrogen gas introduction flow path 22, hydrogen gas flow path 24, and anode off-gas discharge flow path 26). The normal operation is the same as that of the conventional fuel cell system, and thus the description thereof is omitted.

  FIG. 3 is an explanatory diagram showing a scavenging operation for removing stagnant water that is executed when the operation of the fuel cell system is stopped. In the fuel cell system 100, when the operation is stopped, the control unit 70 controls the fuel gas system 30 (the shut valve 32, the regulator 33, the injector 34, the circulation pump 36, and the like) to use hydrogen gas as a scavenging gas. The scavenging operation is executed according to the following procedure. The fuel gas supply system 30 and the control unit 70 correspond to the scavenging gas supply unit and the scavenging control unit in this embodiment.

  First, as the first scavenging operation, the remaining remaining water in the anode of each fuel cell 12 is discharged at the first scavenging gas flow rate Vs [NL / min] and the first scavenging time ts [sec]. The scavenging performed (hereinafter also referred to as “total scavenging”) is executed (step S10). The scavenging gas is hydrogen gas as a fuel gas.

  As the first scavenging gas flow rate Vs, a gas flow rate larger than the normal gas flow rate during power generation is set as follows. First, the water transferable differential pressure ΔPm required to move the remaining water remaining in the anode is obtained by calculation from the size and mass of the remaining water. A flow rate capable of generating a differential pressure ΔP larger than the water transferable differential pressure ΔPm is calculated by calculation based on each location in the anode through which hydrogen gas passes, in particular, the structure of the hydrogen gas flow path 24. The first scavenging gas flow rate Vs is set.

  During the first scavenging time ts, the stagnant water remaining at the inlet of the hydrogen gas flow path of the anode separator 20a of each fuel cell 12 moves through the flow path to the outside of the fuel cell 10 via the hydrogen discharge manifold. Based on the channel length and flow velocity in each of the hydrogen gas introduction channel 22, the hydrogen gas channel 24, and the anode off-gas outlet channel 26, it is calculated and set so as to be discharged.

  The first scavenging gas flow rate Vs is set to, for example, about 0.5 [NL / min] to 1.5 [NL / min], and the first scavenging time ts is, for example, 10 [sec] to It is set to about 60 [sec].

  By the first scavenging operation, most of the remaining water remaining in the anode of each fuel cell 10 of the fuel cell 10 is discharged to the outside of the fuel cell 10. Of the remaining water that has not been completely discharged, the remaining water in the vicinity of the anode off-gas outlet channel 26 is attracted to and moved to each section outlet channel 26p that constitutes the anode off-gas outlet channel 26, and the anode off-gas outlet flow. It becomes the stagnant water of each section derivation channel 26p of channel 26.

  Next, as the second scavenging operation, a scavenging gas flow rate Vsm [NL / min] lower than the first scavenging gas flow rate Vs and a second scavenging time tsm [sec] shorter than the first scavenging time. In the state where the remaining water in the hydrogen gas flow path 24 of each fuel battery cell 12 remains, scavenging (hereinafter referred to as “hereinafter,“ remaining water remaining in the anode off-gas discharge flow path 26) is discharged from the anode off-gas discharge flow path 26. (Also referred to as “leading channel scavenging”) (step S20). The scavenging gas is hydrogen gas as in the first scavenging operation.

  The second scavenging gas flow rate Vsm is set as follows. That is, the differential pressure ΔP1 in each divided flow path 24p (see FIG. 2) of the hydrogen gas flow path 24 of each fuel cell 12 is a flow rate that is smaller than the water transferable differential pressure ΔPm, and the anode off-gas outlet flow path. The flow rate at which the differential pressure ΔP2 in each of the segment outlet channels 26p (see FIG. 2) is larger than the water transferable differential pressure ΔPm is calculated based on the structure of the hydrogen gas channel 24 and the anode off-gas outlet channel 26. The second scavenging gas flow rate Vsm is set. It will be described later that the differential pressure ΔP2 in the anode off-gas outlet channel 26 becomes larger than the water transferable differential pressure ΔPm at the same scavenging gas flow rate Vsm.

  During the second scavenging time tsm, the remaining water remaining at the inlet of the anode off-gas outlet channel 26 of each fuel cell 12 moves through the channel and is discharged from the anode off-gas outlet 26 and discharged from the fuel cell 10 to the outside. As described above, it is obtained and set by calculation based on the flow path length and flow velocity of the anode off-gas outlet flow path 26.

  The second scavenging gas flow rate Vsm is set to, for example, about 0.1 [NL / min] to 0.25 [NL / min], and the second scavenging time tsm is, for example, 3 [sec] to It is set to about 8 [sec].

  FIG. 4 is an explanatory diagram showing the stagnant water in the second scavenging operation. The divided scavenging gas flow rate Vsm1 flowing in each of the divided flow channels 24p of the hydrogen gas flow channel 24 is ideally obtained by dividing the set second scavenging gas flow rate Vsm by the number m of the flow channels (see FIG. 2B). (Vsm / m). As described above, the second scavenging gas flow rate Vsm, more specifically, the divided flow channel scavenging gas flow rate Vsm1, is the differential pressure ΔP1 in the divided flow channel 24p so that the remaining water remaining in the divided flow channel 24p does not move. Is set to be smaller than the water transferable differential pressure ΔPm. Accordingly, as shown in FIG. 4A, the remaining water remaining in each of the divided flow paths 24p of the hydrogen gas flow path 24 does not move.

  On the other hand, the segment derivation channel scavenging gas flow rate Vsm2 flowing in each segment derivation channel 26p of the anode off-gas derivation channel 26 is equal to the number of segment channels 24p in the hydrogen gas channel 24. Since the number n (n in this example) is set to be smaller than m (m = 7 in this example) (see FIG. 2), it is ideally larger than the section flow scavenging gas flow rate Vsm1 (Vsm1 · m / n). As a result, the flow rate of the scavenging gas in the segment derivation channel 26p becomes faster than the flow rate in the segment channel 24p, and the differential pressure ΔP2 in the segment derivation channel 26p becomes larger than the differential pressure ΔP1 in the segment channel 24p. Further, since the sectional area Sp2 of the section derivation flow path 26p is set to be smaller than the sectional area Sp1 of the section flow path (see FIG. 2), the difference between the section derivation flow paths 26p even with the same gas flow rate. The pressure ΔP2 is greater than the differential pressure ΔP1 in the segment flow path 24p. Therefore, as shown in FIG. 4B, the differential pressure ΔP2 of the section derivation flow path 26p is set to be larger than ΔPm, and the remaining water remaining in the section derivation flow path 26p moves.

  In the second scavenging operation, the remaining water remaining in the anode off-gas outlet channel 26 is moved and discharged to the outside from the anode off-gas outlet channel 26 while the remaining water remaining in the hydrogen gas channel 24 is not moved. Therefore, it is possible to prevent clogging due to freezing of the remaining water remaining in the anode off-gas outlet channel 26 which is a comb-tooth channel.

  As described above, in the scavenging operation of the present embodiment, much of the remaining water remaining in the anode of each fuel cell 12 of the fuel cell 10 is discharged from the gas flow path in the anode to the outside in the first scavenging operation. Then, in the second scavenging operation, at the end of the first scavenging operation, the remaining water remaining in the anode off-gas outlet channel 26 which is a comb channel, and the anode off-gas outlet channel 26 from the vicinity of the anode off-gas outlet channel 26 In the state where the remaining water that has moved to the hydrogen gas flow path 24 remains so as not to move, the remaining water that remains in the anode off-gas outlet flow path 26 is moved and discharged to the outside of the anode off-gas outlet flow path 26. To do. Accordingly, the remaining water remaining in the anode of each fuel cell 12 of the fuel cell 10 is discharged only by the normal scavenging operation corresponding to the first scavenging operation, so that the remaining water remaining in the anode off-gas outlet channel 26 is discharged. The staying water remaining in the anode off-gas outlet channel 26 can be discharged in a shorter time than the time required for discharging, and blockage of the anode off-gas outlet channel 26 due to freezing can be prevented. Further, since the second scavenging operation is executed with a low scavenging gas flow rate, energy saving can be achieved as compared with the case of only the normal scavenging operation corresponding to the first scavenging operation.

  Note that in the second scavenging operation, focusing on the point that the differential pressure in the section derivation flow path 26p of the anode off-gas derivation flow path 26 is increased to discharge only the remaining water remaining in the section derivation flow path 26p, the anode separator 20a. Assuming that the anode off-gas outlet channel 26 is a comb-tooth channel having an overall width W2 smaller than the overall width W2 of the hydrogen gas channel 24 and having a plurality of segmented outlet channels 26p, the following structure is obtained. You can say. In the case where the second scavenging gas flow rate Vsm is set so that the remaining water remaining in the divided flow path 24p of the hydrogen gas flow path 24 does not move, the differential pressure ΔP2 of the divided discharge flow path 26p of the anode off-gas discharge flow path 26 is the difference in water transferability. The structure is set such that the number n of the section derivation flow paths 26p is set to the number m of the section flow paths 24p so as to be larger than the pressure ΔPm. Further, in the case where the second scavenging gas flow rate Vsm at which the remaining water remaining in the section flow path 24p of the hydrogen gas flow path 24 does not move, the differential pressure ΔP2 of the section discharge flow path 26p of the anode off-gas discharge flow path 26 moves through the water. The sectional area Sp2 of the section derivation flow path 26p with respect to the sectional area Sp1 of the section flow path 24p is set to be larger than the possible differential pressure ΔPm. Further, in the case where the second scavenging gas flow rate Vsm at which the remaining water remaining in the section flow path 24p of the hydrogen gas flow path 24 does not move, the differential pressure ΔP2 of the section discharge flow path 26p of the anode off-gas discharge flow path 26 moves through the water. The total cross-sectional area ΣSp2 of the plurality of section derivation flow paths 26p with respect to the total cross-sectional area ΣSp1 of the plurality of section flow paths 24p is set to be larger than the possible differential pressure ΔPm.

B. Variations:
In the above embodiment, the case where hydrogen gas, which is fuel gas, is used as the scavenging gas has been described as an example. However, when the operation of the fuel cell system is stopped, deterioration of the membrane electrode assembly constituting the fuel cell is prevented. For this purpose, various scavenging gases such as air and various inert gases may be used.

  Moreover, although the case where the hydrogen gas flow path 24 is a serpentine flow path was described as an example in the above embodiment, it may be a straight flow path. However, in the case of a straight flow path, the anode off-gas derivation flow path 26 is larger than the cross-sectional area and the total cross-sectional area of the horizontal flow path for collectively connecting the divided flow paths constituting the straight flow path to the anode off-gas derivation flow path 26. The sectional area of the section derivation flow paths 26p and the total sectional area of the plurality of section derivation flow paths 26p are set small.

  Further, in the above embodiment, on the assumption that the overall width W2 of the anode off-gas outlet flow channel 26 is smaller than the overall width W1 of the hydrogen gas flow channel 24, the number is larger than the number m of the divided flow channels 24p of the hydrogen gas flow channel 24. The number n of the segment outlet channels 26p of the anode off-gas outlet channel 26 is small, the sectional area Sp2 of the segment outlet channel 26p is smaller than the sectional area Sp1 of the segment channel 24p, and the plurality of segment channels 24p. The structure in which the total cross-sectional area ΣSp2 of the plurality of section derivation channels 26p is set smaller than the total cross-sectional area ΣSp1 is described as an example. However, the present invention is not limited to this, and the following various structures are possible.

  When the scavenging gas flow rate Vsm at which the remaining water remaining in the section flow path 24p of the hydrogen gas flow path 24 does not move, the differential pressure ΔP2 of the section discharge flow path 26p of the anode off-gas discharge flow path 26 is greater than the water transferable differential pressure ΔPm. Also, the overall width W2 of the anode off-gas outlet flow channel 26 may be set smaller than the overall width W1 of the hydrogen gas flow channel 24.

  Further, at the above-described scavenging gas flow rate Vsm, the divided flow path 24p of the hydrogen gas flow path 24 is set so that the differential pressure ΔP2 of the divided discharge flow path 26p of the anode off-gas discharge flow path 26 becomes larger than the water transferable differential pressure ΔPm. The number n of the section derivation flow paths 26p of the anode off-gas derivation flow path 26 may be set smaller than the number m of the number. Further, at the above-described scavenging gas flow rate Vsm, the divided flow path 24p of the hydrogen gas flow path 24 is set so that the differential pressure ΔP2 of the divided discharge flow path 26p of the anode off-gas discharge flow path 26 becomes larger than the water transferable differential pressure ΔPm. The sectional area Sp2 of the section outlet flow path 26p of the anode off-gas outlet flow path 26 may be set smaller than the sectional area Sp1 of the above. In addition, at the above scavenging gas flow rate Vsm, the total cross-sectional area of the plurality of divided flow paths 24p is set such that the differential pressure ΔP2 of the divided discharge flow path 26p of the anode off-gas discharge flow path 26 is larger than the water transferable differential pressure ΔPm. It is good also as a structure set to the total cross-sectional area (SIGMA) Sp2 of the some division | segmentation derivation flow paths 26p with respect to (SIGMA) Sp1.

  In the above embodiment, the case where the remaining water remaining in the anode of each fuel cell 12 of the fuel cell 10 is discharged is described as an example. However, the case where the remaining water remaining in the cathode of each fuel cell 12 of the fuel cell 10 is discharged. In addition, it is possible to similarly execute air as scavenging gas as the oxidizing gas. Further, the present invention can be applied to the case where the accumulated water of both the anode and the cathode of each fuel cell 12 of the fuel cell 10 is discharged.

  The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the above effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 12 ... Fuel cell 20a ... Anode side separator 21 ... Hydrogen gas supply port 22 ... Hydrogen gas introduction flow path 22p ... Division introduction flow path 24 ... Hydrogen gas flow path 24p ... Division flow path 26 ... Anode off-gas derivation flow Path 26p ... Section derivation flow path 27 ... Anode off-gas outlet 30 ... Fuel gas system 31 ... Hydrogen tank 32 ... Shut valve 33 ... Regulator 34 ... Injector 35 ... Gas-liquid separator 36 ... Circulating pump 37 ... Exhaust valve 38 ... Drain valve DESCRIPTION OF SYMBOLS 41 ... Hydrogen supply piping 42 ... Anode off gas piping 43 ... Hydrogen circulation piping 44 ... Anode off gas exhaust piping 45 ... Drain piping 50 ... Oxidation gas system 51 ... Air cleaner 52 ... Air compressor 53 ... Piping 54 ... Piping 55 ... Diluter 56 ... Piping 60 ... Cooling system 61 ... Radiator 62 ... Circulation pump 63 ... Piping 7 ... control unit 100 ... fuel cell system

Claims (5)

A fuel cell system,
A fuel cell having a fuel cell including a separator in which a groove-like gas flow path is formed;
A scavenging gas supply unit for supplying a scavenging gas to the gas flow path;
A scavenging control unit for performing a scavenging operation by the scavenging gas supply unit;
With
The gas channel includes a gas outlet channel having a comb-shaped channel connected to a gas channel outlet, and an upstream gas channel connected to the upstream side of the gas outlet channel,
The scavenging control unit
When stopping the operation of the fuel cell, the scavenging gas is supplied from the scavenging gas supply unit at a first scavenging gas flow rate and a first scavenging time, so that the water staying in the fuel cell is Performing a first scavenging operation for discharging to the outside of the gas flow path;
The second gas scavenging gas flow rate lower than the first gas scavenging gas flow rate after execution of the first gas scavenging operation, and the gas outlet flow channel with water remaining in the upstream gas flow channel remaining. The scavenging gas is supplied from the scavenging gas supply unit at a second scavenging gas flow rate for discharging water staying in the gas outflow passage and a second scavenging time shorter than the first scavenging time. A second scavenging operation for supplying is executed. A fuel cell system. The fuel cell system according to claim 1,
The fuel gas cell characterized in that the second scavenging gas flow rate is a flow rate at which a differential pressure generated in the upstream gas flow path is smaller than a differential pressure required for water movement in the upstream gas flow path. system. The fuel cell system according to claim 2, wherein
The gas outlet channel has a structure in which a differential pressure generated in the gas outlet channel by the second scavenging gas flow rate is larger than a differential pressure required for water movement in the gas outlet channel. A fuel cell system. The fuel cell system according to claim 3,
In the fuel cell, the total cross-sectional area of the groove-shaped flow path included in the gas outlet flow path is smaller than the total cross-sectional area of the groove-shaped flow path included in the upstream gas flow path. system. The fuel cell system according to claim 3 or 4, wherein
The fuel cell system according to the structure, wherein the entire width of the gas outlet channel is smaller than the entire width of the upstream gas channel.

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