Fuel cell system

Abstract

To provide a fuel cell system that can discharge fuel exhaust gas to the outside while maintaining a low concentration of fuel in the exhaust gas. [Solution] One aspect of the present disclosure provides a fuel cell system 1 having a hydrogen off-gas dilution section 70 provided at the outlet 33 of a hydrogen off-gas discharge passage 32 for diluting hydrogen off-gas. The hydrogen off-gas dilution section 70, as a dilution section forming a space for diluting hydrogen off-gas, comprises at least a first dilution section 71 that accommodates the outlet 33 of the hydrogen off-gas discharge passage 32, and a second dilution section 72 that accommodates the first dilution section 71. The case 81 forming the first dilution section 71 and the case 82 forming the second dilution section 72 each have hydrogen off-gas discharge holes 91 and 92, respectively, for discharging hydrogen off-gas from the inside to the outside.

Description

[Technical Field]

[0001] The present disclosure relates to a fuel cell system including a fuel cell that generates electric power by being supplied with fuel gas and oxidant gas. [Background Art]

[0002] Patent Document 1 discloses a fuel cell system including: a fuel cell; a fuel exhaust gas passage through which fuel exhaust gas discharged from the fuel cell flows; and an exhaust drain valve provided in the fuel exhaust gas passage that adjusts the discharge of fuel exhaust gas to the outside.

[0003] Further, Patent Document 2 discloses a fuel cell system including an exhaust fuel diluter in a fuel exhaust gas passage (purged hydrogen pipe). [Prior Art Literature] [Patent Literature]

[0004] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2024-130509 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2003-132915 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] As a standard for discharging hydrogen from a fuel cell system, laws and regulations stipulate that "the concentration of hydrogen in hydrogen off-gas discharged to the outside shall be reduced to a predetermined value (for example, 4%) or less". Here, Patent Document 1 does not disclose any method for reducing the concentration of fuel (for example, hydrogen) in fuel exhaust gas such as hydrogen off-gas discharged to the outside.

[0006] Further, the technology disclosed in Patent Document 2 merely dilutes fuel exhaust gas (exhaust fuel) in a single dilution region, and therefore there is a risk that the fuel exhaust gas cannot be sufficiently diluted, and the concentration of fuel in the fuel exhaust gas cannot be sufficiently reduced.

[0007] Therefore, this disclosure has been made to solve the above-mentioned problems, and aims to provide a fuel cell system that can discharge fuel exhaust gas to the outside while keeping the fuel concentration in the fuel exhaust gas low. [Means for solving the problem]

[0008] One embodiment of the present disclosure made to solve the above problems is a fuel cell system having a fuel cell and a fuel exhaust gas passage through which fuel exhaust gas discharged from the fuel cell flows, wherein the fuel exhaust gas passage is provided with a fuel exhaust gas dilution section for diluting the fuel exhaust gas, and the fuel exhaust gas dilution section comprises, as a dilution section that forms a space for diluting the fuel exhaust gas, at least a first dilution section that houses the fuel exhaust gas passage and a second dilution section that houses the first dilution section, and the case forming the first dilution section and the case forming the second dilution section each have fuel exhaust gas discharge holes for discharging the fuel exhaust gas from the inside to the outside.

[0009] According to this embodiment, the fuel exhaust gas discharged from the fuel exhaust gas passage is diffused and diluted in the space formed in the first dilution section of the fuel exhaust gas dilution section, then discharged to the second dilution section through the fuel exhaust gas discharge port, and further diffused and diluted in the space formed in the second dilution section of the fuel exhaust gas dilution section. In this way, the fuel exhaust gas can be sufficiently diluted in at least two dilution sections of the fuel exhaust gas dilution section before being discharged to the outside of the fuel cell system through the fuel exhaust gas discharge port. Therefore, the fuel exhaust gas can be discharged to the outside with a low concentration of fuel in the fuel exhaust gas.

[0010] In the above embodiment, it is preferable that the fuel exhaust gas is hydrogen exhaust gas containing hydrogen, and that the fuel exhaust gas discharge hole is formed at a position in the direction in which gravity acts, rather than at the position of the central axis of the fuel exhaust gas passage.

[0011] According to this embodiment, hydrogen exhaust gas discharged from the fuel exhaust gas passage into the dilution section is discharged from the fuel exhaust gas discharge port, thereby suppressing the flow of hydrogen, which has a low specific gravity, in the direction opposite to the direction in which gravity acts and discharges it to the outside. As a result, the hydrogen exhaust gas can be effectively diffused and diluted within the space of the dilution section.

[0012] In the above embodiment, it is preferable that the total area of ​​the fuel exhaust gas discharge holes formed in the second dilution section is larger than the total area of ​​the fuel exhaust gas discharge holes formed in the first dilution section.

[0013] According to this embodiment, the fuel exhaust gas discharged from the first dilution section to the second dilution section is further diluted in the second dilution section and then more easily discharged to the outside of the second dilution section through the fuel exhaust gas discharge holes formed in the second dilution section. As a result, the fuel exhaust gas discharged from the fuel exhaust gas passage is sufficiently diluted in the fuel exhaust gas dilution section and then more easily discharged to the outside of the fuel cell system.

[0014] In the above embodiment, it is preferable to have a fan for diffusing the fuel exhaust gas discharged from the fuel exhaust gas dilution section.

[0015] According to this embodiment, the diluted fuel exhaust gas discharged from the fuel exhaust gas dilution unit can be further diffused and diluted by a fan before being discharged outside the fuel cell system. Therefore, the fuel exhaust gas can be discharged outside the fuel cell system more effectively and sufficiently diluted.

[0016] In the above embodiment, it is preferable that the system includes a passage control valve for opening and closing the fuel exhaust gas passage, a valve control unit for controlling the passage control valve, and a current measuring unit for measuring the current generated by the fuel cell, wherein the valve control unit controls the closing cycle, which is the period from when the passage control valve starts to be closed until it starts to be closed again, according to the current measurement value of the current measured by the current measuring unit.

[0017] According to this embodiment, the current measurement value measured by the current measuring unit changes according to the amount of fuel exhaust gas generated in the fuel cell, so the closing cycle of the exhaust drain valve can be controlled according to the amount of fuel exhaust gas generated in the fuel cell. Therefore, the amount of fuel discharged from the fuel exhaust gas passage to the outside of the fuel cell system can be controlled.

[0018] In the above embodiment, it is preferable that the valve control unit shortens the valve closing period as the measured value of the current increases.

[0019] According to this embodiment, as the amount of fuel exhaust gas generated in the fuel cell increases and the measured current value increases, the cycle in which the passage opening / closing valve closes the fuel exhaust gas passage can be shortened, thereby reducing the flow rate of fuel exhaust gas flowing through the fuel exhaust gas passage. As a result, the amount of hydrogen emitted to the outside of the fuel cell system can be suppressed.

[0020] In the above embodiment, the system includes a passage control valve for opening and closing the fuel exhaust gas passage, and a valve control unit for controlling the passage control valve. Preferably, the valve control unit sets the opening time of the passage control valve to be equal to, or approximately equal to, the ineffective injection time, which is the time from the time from the opening request to the actual opening state to the time from the closing request to the actual closing state.

[0021] According to this embodiment, the opening time of the passage valve can be kept as short as possible, thereby suppressing the discharge of high-concentration fuel exhaust gas with a high fuel concentration to the outside of the fuel cell system.

[0022] In the above embodiment, it is preferable that the surface in the direction in which gravity acts in the first dilution portion and the surface in the direction in which gravity acts in the second dilution portion are formed parallel to the ground.

[0023] According to this embodiment, the fuel exhaust gas diluted in the first dilution section is more easily discharged to the second dilution section from the fuel exhaust gas discharge port on the plane in which gravity acts. In addition, the fuel exhaust gas diluted in the second dilution section is more easily discharged to the outside of the second dilution section from the fuel exhaust gas discharge port on the plane in which gravity acts.

[0024] In the above aspect, it is preferable that the fuel exhaust gas dilution section includes a third dilution section that accommodates the second dilution section, and the fuel exhaust gas discharge hole is formed in a case forming the third dilution section.

[0025] According to this aspect, after fuel exhaust gas is sufficiently diluted by the three dilution sections in the fuel exhaust gas dilution section, the fuel exhaust gas can be discharged through the fuel exhaust gas discharge hole and then discharged to the outside of the fuel cell system. Therefore, the fuel exhaust gas can be discharged to the outside in a state where the concentration of fuel in the fuel exhaust gas is lowered. Effects of the Invention

[0026] According to the fuel cell system of the present disclosure, fuel exhaust gas can be discharged to the outside in a state where the concentration of fuel in the fuel exhaust gas is lowered. Brief Description of Drawings

[0027] [Figure 1] FIG. 1 is a configuration diagram of the fuel cell system (open-cathode system) of the present embodiment. [Figure 2] FIG. 2 is a schematic structural diagram of a hydrogen off-gas dilution section. [Figure 3] FIG. 3 is a flowchart showing the content of control performed by a valve control section. [Figure 4] FIG. 4 is a diagram showing an example of a map that defines the relationship between an FC current and a valve closing cycle of an exhaust drain valve. Mode for Carrying Out the Invention

[0028] An embodiment of the fuel cell system of the present disclosure will be described.

[0029] <Configuration of Fuel Cell System> As shown in FIG. 1, the fuel cell system 1 of the present embodiment includes an FC stack 11, a hydrogen system 21, and an air system / cooling system 22. The FC stack 11 is an example of the "fuel cell" in the present disclosure.

[0030] The FC stack 11 generates electricity by receiving a supply of fuel gas and oxidizer gas. In this embodiment, the fuel gas is hydrogen gas and the oxidizer gas is air. That is, the FC stack 11 generates electricity by receiving a supply of hydrogen gas from the hydrogen system 21 and a supply of air from the air system / cooling system 22. The electricity generated by the FC stack 11 is then supplied to a battery (not shown), a motor (not shown), and an inverter (not shown). Note that hydrogen is an example of "fuel" in this disclosure.

[0031] The hydrogen system 21 is located on the anode side of the FC stack 11. This hydrogen system 21 includes a hydrogen gas supply passage 31 and a hydrogen off-gas discharge passage 32.

[0032] The hydrogen gas supply passage 31 is a passage for supplying hydrogen gas from the hydrogen tank 41, which stores hydrogen gas, to the FC stack 11. The hydrogen off-gas discharge passage 32 is a passage through which hydrogen gas (containing hydrogen) discharged from the FC stack 11 (hereinafter referred to as "hydrogen off-gas") flows. The hydrogen off-gas discharge passage 32 is an example of the "fuel exhaust gas passage" in this disclosure. Furthermore, hydrogen off-gas is an example of "fuel exhaust gas" or "hydrogen exhaust gas" in this disclosure.

[0033] Furthermore, the hydrogen system 21 includes an injector 42 in the hydrogen gas supply passage 31 that injects hydrogen gas supplied from the hydrogen tank 41 to the downstream FC stack 11.

[0034] Furthermore, the hydrogen system 21 has an exhaust drain valve 51 in the hydrogen off-gas discharge passage 32. This exhaust drain valve 51 opens and closes the hydrogen off-gas discharge passage 32 to regulate the discharge of hydrogen off-gas and moisture to the outside. Note that the exhaust drain valve 51 is an example of a "passage opening / closing valve" as described herein.

[0035] On the other hand, the air and cooling system 22 is located on the cathode side of the FC stack 11. This air and cooling system 22 includes an air supply passage 61, an air-off gas discharge passage 62, and a fan 63.

[0036] The air supply passage 61 is a passage for supplying air from outside the fuel cell system 1 to the FC stack 11. The air-off gas discharge passage 62 is a passage for discharging air (i.e., air-off gas) discharged from the FC stack 11. The fan 63 supplies air to the FC stack 11 via the air supply passage 61 and discharges air-off gas from the FC stack 11 via the air-off gas discharge passage 62.

[0037] The fuel cell system 1 shown in Figure 1 is an open-cathode system in which the airflow path for supplying air to the FC stack 11 and the airflow path for cooling the FC stack 11 are shared. In other words, in the fuel cell system 1, the air supplied to the FC stack 11 by the fan 63 is used as the cooling gas for the FC stack 11. To put it another way, the fuel cell system 1 is an open-cathode system in which the fan 63 for cooling the FC stack 11 is also used as a means of supplying air to the FC stack 11.

[0038] Furthermore, the fuel cell system 1 is equipped with a current sensor 12. This current sensor 12 measures the FC current (i.e., the current generated by the FC stack 11). Note that the current sensor 12 is an example of the "current measuring unit" described herein.

[0039] Furthermore, the fuel cell system 1 has a control unit 13. The control unit 13 is a device that includes, for example, an arithmetic processing unit such as a CPU, a storage unit such as a ROM that stores control programs and control data processed by the CPU, and a RAM used as various work areas for control processing, and an input / output interface unit. The control unit 13 then performs various controls on the fuel cell system 1 according to the control program stored in the storage unit.

[0040] In this embodiment, the control unit 13 controls various components of the fuel cell system 1, including the injector 42, exhaust and drain valve 51, and fan 63, as well as performing various calculations. Furthermore, the control unit 13 includes a valve control unit 101 that controls the opening and closing of the exhaust and drain valve 51, as will be described in more detail later.

[0041] <How fuel cell systems work> In the fuel cell system 1 configured as described above, the hydrogen gas supplied to the FC stack 11 from the hydrogen gas supply passage 31 is used for power generation in the FC stack 11, and then discharged from the FC stack 11 as hydrogen off-gas to the outside of the fuel cell system 1 via the hydrogen off-gas discharge passage 32. Similarly, the air supplied to the FC stack 11 from the air supply passage 61 is used for power generation in the FC stack 11, and then discharged from the FC stack 11 as air off-gas to the outside of the fuel cell system 1 via the air off-gas discharge passage 62.

[0042] <Dilution of hydrogen off-gas> As a standard for emitting hydrogen from fuel cell systems, regulations stipulate that "the concentration of hydrogen in the hydrogen off-gas discharged to the outside must be below a specified value (for example, 4%)."

[0043] In this embodiment, when an open cathode system is employed, there is no equipment such as a compressor capable of supplying a large amount of air. Therefore, it is not possible to supply air using equipment such as a compressor to dilute the hydrogen off-gas and lower the hydrogen concentration in the hydrogen off-gas.

[0044] Therefore, in this embodiment, we propose a technique that allows the hydrogen off-gas to be diluted and the hydrogen concentration in the hydrogen off-gas to be lowered, even if the fuel cell system 1 is an open cathode type system.

[0045] Specifically, in the fuel cell system 1 of this embodiment, as shown in Figure 1, a hydrogen off-gas dilution unit 70 for diluting the hydrogen off-gas is provided at a location downstream of the exhaust drain valve 51 in the hydrogen off-gas discharge passage 32 (i.e., downstream in the direction of hydrogen off-gas flow), more precisely at the outlet 33 of the hydrogen off-gas discharge passage 32. The hydrogen off-gas dilution unit 70 is an example of the "fuel exhaust gas dilution unit" of this disclosure.

[0046] As shown in Figures 1 and 2, the hydrogen off-gas dilution section 70 includes a first dilution section 71, a second dilution section 72, and a third dilution section 73, which form a space for diluting the hydrogen off-gas.

[0047] The first dilution section 71 comprises a case 81 that forms the first dilution section 71, and the outlet 33 of the hydrogen off-gas discharge passage 32 is housed inside this case 81. The second dilution section 72 comprises a case 82 that forms the second dilution section 72, and the first dilution section 71 is housed inside this case 82. Furthermore, the third dilution section 73 comprises a case 83 that forms the third dilution section 73, and the second dilution section 72 is housed inside this case 83.

[0048] Cases 81, 82, and 83 are formed in a box shape (for example, a rectangular parallelepiped, a cube, or a cylinder). Inside each of these cases, there is a space for diffusing and diluting the hydrogen off-gas. The volume of case 83 is, for example, 1.5 L (liters).

[0049] Multiple hydrogen off-gas discharge holes 91 are formed on the lower surface 81a of case 81 (i.e., the surface in the direction in which gravity acts (downward in Figure 2)) to discharge hydrogen off-gas from the inside of case 81 to the outside of case 81 (i.e., the inside of case 82).

[0050] Furthermore, multiple hydrogen off-gas discharge holes 92 are formed on the lower surface 82a of case 82 (i.e., the surface in the direction in which gravity acts) to discharge hydrogen off-gas from the inside of case 82 to the outside of case 82 (i.e., the inside of case 83).

[0051] Furthermore, multiple hydrogen off-gas discharge holes 93 are formed on the lower surface 83a of the case 83 (i.e., the surface in the direction in which gravity acts) to discharge hydrogen off-gas from the inside of the case 83 to the outside of the case 83 (i.e., to the outside of the hydrogen off-gas dilution section 70).

[0052] Thus, as shown in Figure 2, the hydrogen off-gas discharge holes 91, 92, and 93 are formed in a direction in which gravity acts (i.e., downward in Figure 2) relative to the position of the passage central axis CA at the outlet 33 of the hydrogen off-gas discharge passage 32. Note that the hydrogen off-gas discharge holes 91, 92, and 93 are examples of the "fuel exhaust gas discharge holes" of this disclosure.

[0053] Furthermore, the total area TS2 of the multiple hydrogen off-gas discharge holes 92 formed in the second dilution section 72 (i.e., the total area of ​​all hydrogen off-gas discharge holes 92) is larger than the total area TS1 of the multiple hydrogen off-gas discharge holes 91 formed in the first dilution section 71 (i.e., the total area of ​​all hydrogen off-gas discharge holes 91).

[0054] Furthermore, the total area TS3 of the multiple hydrogen off-gas discharge holes 93 formed in the third dilution section 73 (i.e., the total area of ​​all hydrogen off-gas discharge holes 93) is larger than the total area TS2 of the multiple hydrogen off-gas discharge holes 92 formed in the second dilution section 72.

[0055] In other words, the sizes of the total areas TS1, TS2, and TS3 are set as shown in [Equation 1] below. [Formula 1] (TS3)>(TS2)>(TS1)

[0056] Furthermore, the lower surfaces 81a, 82a, and 83a are formed parallel to the ground.

[0057] In a fuel cell system 1 equipped with a hydrogen off-gas dilution unit 70 having such a configuration, the valve control unit 101 (see Figure 1) performs the control shown in Figure 3.

[0058] As shown in Figure 3, the valve control unit 101 calculates the closing period of the exhaust drain valve 51 using the one-dimensional map shown in Figure 4, according to the FC current (step S1).

[0059] In this way, the valve control unit 101 controls the closing period of the exhaust and drain valve 51 according to the measured value of the FC current measured by the current sensor 12. Specifically, as shown in Figure 4, for example, the valve control unit 101 shortens the closing period of the exhaust and drain valve 51 as the measured value of the FC current increases. Here, the closing period of the exhaust and drain valve 51 is the period from when the exhaust and drain valve 51 starts to be in a closed state until it starts to be in a closed state again.

[0060] Next, the valve control unit 101 opens the exhaust drain valve 51 for a time equal to the ineffective injection time (e.g., 30 ms), or approximately equal to it (i.e., the shortest time greater than or equal to the ineffective injection time) (e.g., 30 ms) (step S2). Here, the ineffective injection time is shown in the following [Equation 2]. [Formula 2] (Ineffective injection time) = (Time from valve opening request until the exhaust / drain valve is actually open) - (Time from valve closing request until the exhaust / drain valve is actually closed)

[0061] In this way, the valve control unit 101 controls the opening time of the exhaust drain valve 51 so that it is equal to or approximately equal to the ineffective injection time.

[0062] As a modified example, as shown in Figure 2, the fuel cell system 1 may have a diffusion fan 111 for diffusing the hydrogen off-gas discharged from the hydrogen off-gas dilution unit 70.

[0063] According to this embodiment, the fuel cell system 1 has a hydrogen off-gas dilution section 70 provided at the outlet 33 of the hydrogen off-gas discharge passage 32 for diluting the hydrogen off-gas. The hydrogen off-gas dilution section 70 comprises a first dilution section 71, a second dilution section 72, and a third dilution section 73, which form a space for diluting the hydrogen off-gas. The case 81 forming the first dilution section 71, the case 82 forming the second dilution section 72, and the case 83 forming the third dilution section 73 each have hydrogen off-gas discharge holes 91, 92, and 93 formed therein for discharging the hydrogen off-gas from the inside of the cases 81, 82, and 83 to the outside.

[0064] In this way, the hydrogen off-gas discharged from the outlet 33 of the hydrogen off-gas discharge passage 32 is diffused and diluted in the space formed inside the case 81 of the first dilution section 71 of the hydrogen off-gas dilution section 70, and then discharged into the case 82 of the second dilution section 72 via the hydrogen off-gas discharge hole 91.

[0065] Furthermore, the hydrogen off-gas discharged into the case 82 of the second dilution section 72 can be diffused and diluted in the space formed inside the case 82 of the second dilution section 72, and then discharged into the case 83 of the third dilution section 73 via the hydrogen off-gas discharge hole 92.

[0066] Furthermore, the hydrogen off-gas discharged into the case 83 of the third dilution unit 73 can be diffused and diluted in the space formed inside the case 83 of the third dilution unit 73, and then discharged to the outside of the hydrogen off-gas dilution unit 70 through the hydrogen off-gas discharge hole 93.

[0067] In this way, the hydrogen off-gas can be sufficiently diluted in the three dilution sections of the hydrogen off-gas dilution section 70 before being discharged to the outside of the fuel cell system 1.

[0068] In other words, a high-concentration hydrogen off-gas (i.e., a high concentration of hydrogen in the hydrogen off-gas) is diluted in the first dilution section 71. Next, the low-concentration hydrogen off-gas (i.e., a low concentration of hydrogen in the hydrogen off-gas) diluted in the first dilution section 71 is diluted in the second dilution section 72. Next, the even lower-concentration hydrogen off-gas (i.e., an even lower concentration of hydrogen in the hydrogen off-gas) diluted in the second dilution section 72 is diluted in the third dilution section 73.

[0069] This allows the extremely low-concentration hydrogen off-gas (i.e., the hydrogen concentration in the hydrogen off-gas is extremely low) diluted in the third dilution unit 73 to be discharged to the outside of the hydrogen off-gas dilution unit 70 and then to the outside of the fuel cell system 1. Therefore, the hydrogen off-gas can be discharged to the outside with a low hydrogen concentration. Furthermore, even if the vehicle on which the fuel cell system 1 is installed is tilted or vibrates, the hydrogen off-gas can be discharged to the outside with a low hydrogen concentration.

[0070] Furthermore, the hydrogen off-gas discharge holes 91, 92, and 93 are formed in a position in the direction of gravity acting more than the position of the passage central axis CA at the outlet 33 of the hydrogen off-gas discharge passage 32.

[0071] This allows the hydrogen off-gas to be discharged from the hydrogen off-gas discharge holes 91, 92, and 93 in the first dilution section 71, the second dilution section 72, and the third dilution section 73, respectively, thereby suppressing the flow of hydrogen, which has a low specific gravity, in the direction opposite to the direction in which gravity acts and its discharge to the outside. As a result, the hydrogen off-gas can be effectively diffused and diluted in the internal spaces of the first dilution section 71, the second dilution section 72, and the third dilution section 73.

[0072] Furthermore, the total area TS2 of the multiple hydrogen off-gas discharge holes 92 formed in the second dilution section 72 is larger than the total area TS1 of the multiple hydrogen off-gas discharge holes 91 formed in the first dilution section 71. In addition, the total area TS3 of the multiple hydrogen off-gas discharge holes 93 formed in the third dilution section 73 is larger than the total area TS2 of the multiple hydrogen off-gas discharge holes 92 formed in the second dilution section 72.

[0073] As a result, the hydrogen off-gas discharged from the first dilution section 71 to the second dilution section 72 via the hydrogen off-gas discharge hole 91 is diluted in the second dilution section 72 and then discharged from the second dilution section 72 to the third dilution section 73 via the hydrogen off-gas discharge hole 92. Further dilution in the third dilution section 73 makes it easier for the hydrogen off-gas to be discharged to the outside of the third dilution section 73 via the hydrogen off-gas discharge hole 93. In this way, the hydrogen off-gas discharged from the outlet 33 of the hydrogen off-gas discharge passage 32 is diluted in the hydrogen off-gas dilution section 70 and then easily discharged to the outside of the fuel cell system 1.

[0074] Furthermore, the fuel cell system 1 may have a diffusion fan 111 for diffusing the hydrogen off-gas discharged from the hydrogen off-gas dilution unit 70.

[0075] This allows the hydrogen off-gas, diluted in the hydrogen off-gas dilution unit 70, to be further diluted by diffusion in the air using the diffusion fan 111 before being discharged to the outside of the fuel cell system 1. Therefore, the hydrogen off-gas can be more effectively diluted before being discharged to the outside of the fuel cell system 1.

[0076] Furthermore, the valve control unit 101 controls the closing cycle of the exhaust drain valve 51 according to the measured value of the FC current in the current sensor 12.

[0077] In this way, the closing cycle of the exhaust drain valve 51 can be controlled according to the amount of hydrogen off-gas generated in the FC stack 11. Therefore, the amount of hydrogen discharged from the hydrogen off-gas discharge passage 32 to the outside of the fuel cell system 1 can be controlled.

[0078] Furthermore, as the amount of power generated in the FC stack 11 increases and the measured value of the FC current measured by the current sensor 12 increases, the amount of hydrogen off-gas generated in the FC stack 11 increases. Therefore, the valve control unit 101 shortens the closing cycle of the exhaust drain valve 51 as the measured value of the FC current increases.

[0079] In this way, by shortening the cycle in which the exhaust drain valve 51 closes the hydrogen off-gas discharge passage 32 and increasing the frequency of closing the exhaust drain valve 51, the flow rate of hydrogen off-gas flowing to the outlet 33 of the hydrogen off-gas discharge passage 32 can be reduced. Therefore, the amount of hydrogen emitted from the fuel cell system 1 to the outside can be suppressed.

[0080] Furthermore, the valve control unit 101 sets the opening time of the exhaust drain valve 51 to be equal to or approximately equal to the ineffective injection time.

[0081] This allows the opening time of the exhaust drain valve 51 to be kept as short as possible, thereby suppressing the discharge of high-concentration hydrogen off-gas with a high hydrogen concentration to the outside of the fuel cell system 1.

[0082] Furthermore, the lower surface 81a of the first dilution section 71, the lower surface 82a of the second dilution section 72, and the lower surface 83a of the third dilution section 73 are formed parallel to the ground.

[0083] As a result, the hydrogen off-gas diluted in the internal space of the case 81 of the first dilution section 71 is more easily discharged from the hydrogen off-gas discharge hole 91 on the lower surface 81a into the internal space of the case 82 of the second dilution section 72, which is located outside the case 81. Furthermore, the hydrogen off-gas diluted in the internal space of the case 82 of the second dilution section 72 is more easily discharged from the hydrogen off-gas discharge hole 92 on the lower surface 82a into the internal space of the case 83 of the third dilution section 73, which is located outside the case 82. In addition, the hydrogen off-gas diluted in the internal space of the case 83 of the third dilution section 73 is more easily discharged from the hydrogen off-gas discharge hole 93 on the lower surface 83a into the outside of the hydrogen off-gas dilution section 70, which is located outside the case 83.

[0084] It should be noted that the embodiments described above are merely illustrative examples and do not limit this disclosure in any way. Various improvements and modifications are possible without departing from the gist of the disclosure.

[0085] For example, the hydrogen off-gas dilution unit 70 may have multiple dilution units, and may have two dilution units, a first dilution unit 71 and a second dilution unit 72, or it may have four or more dilution units. In other words, the hydrogen off-gas dilution unit 70 may have at least two dilution units.

[0086] Furthermore, the hydrogen off-gas discharge holes 91, 92, and 93 only need to be formed in a position in the direction in which gravity acts, with reference to the position of the passage central axis CA at the outlet 33 of the hydrogen off-gas discharge passage 32. Therefore, the hydrogen off-gas discharge holes 91, 92, and 93 may be formed in a position in the direction in which gravity acts more than the position of the passage central axis CA on the side surfaces of cases 81, 82, and 83.

[0087] Furthermore, the hydrogen off-gas dilution section 70 may be provided at a location other than the outlet 33, downstream of the exhaust drain valve 51 in the hydrogen off-gas discharge passage 32.

[0088] Furthermore, the fuel cell system 1 may be a closed-cathode system in which the air system and the cooling system are provided separately. Here, the air system is a system that supplies air to the FC stack 11 from outside the air system and discharges air-off gas, which is air that was not used for power generation, from the FC stack 11. The cooling system is a system that cools the FC stack 11. [Explanation of symbols]

[0089] 1. Fuel cell system 11 FC stack 12 Current Sensor 13 Control Unit 21 Hydrogen-based systems 32 Hydrogen off-gas emission channel 33 Exit 51 Exhaust drain valve 70 Hydrogen off-gas dilution section 71 First Dilution Part 72 Second Dilution Part 73 Third Dilution Part 81 cases 81a Bottom side 82 cases 82a Bottom side 83 cases 83a Bottom surface 91 Hydrogen off-gas exhaust port 92 Hydrogen off-gas exhaust holes 93 Hydrogen off-gas exhaust port 101 Valve control unit 111 Spreading Fan CA aisle center axis TS1 Total Area TS2 Total Area TS3 Total Area

Claims

1. Fuel cells and A fuel exhaust gas passage through which fuel exhaust gas discharged from the fuel cell flows, has In fuel cell systems, The fuel exhaust gas passage is provided and has a fuel exhaust gas dilution section for diluting the fuel exhaust gas, The fuel exhaust gas dilution section comprises, as a dilution section that forms a space for diluting the fuel exhaust gas, at least a first dilution section that houses the fuel exhaust gas passage, and a second dilution section that houses the first dilution section. The case forming the first dilution section and the case forming the second dilution section each have fuel exhaust gas discharge holes for discharging the fuel exhaust gas from the inside to the outside. A fuel cell system characterized by the following.

2. In the fuel cell system of claim 1, The aforementioned fuel exhaust gas is hydrogen exhaust gas containing hydrogen, The fuel exhaust gas discharge hole is formed in a position in the direction in which gravity acts, rather than at the position of the central axis of the fuel exhaust gas passage. A fuel cell system characterized by the following.

3. In the fuel cell system of claim 1 or 2, The total area of ​​the fuel exhaust gas discharge holes formed in the second dilution section is greater than the total area of ​​the fuel exhaust gas discharge holes formed in the first dilution section. A fuel cell system characterized by the following.

4. In the fuel cell system of claim 1 or 2, The unit has a fan that diffuses the fuel exhaust gas discharged from the fuel exhaust gas dilution unit. A fuel cell system characterized by the following.

5. In the fuel cell system of claim 1 or 2, A passage opening / closing valve for opening and closing the fuel exhaust gas passage, A valve control unit that controls the passage opening and closing valve, It has a current measuring unit for measuring the current generated by the fuel cell, The valve control unit controls the valve closing cycle, which is the period from when the passage valve starts to close until it starts to close again, according to the current measurement value of the current measured by the current measuring unit. A fuel cell system characterized by the following.

6. In the fuel cell system of claim 5, The valve control unit shortens the valve closing period as the measured value of the current increases. A fuel cell system characterized by the following.

7. In the fuel cell system of claim 1 or 2, A passage opening / closing valve for opening and closing the fuel exhaust gas passage, It includes a valve control unit that controls the passage opening and closing valve, The valve control unit sets the opening time of the passage valve to be equal to, or approximately equal to, the ineffective injection time, which is the time from the opening request to the actual opening state minus the time from the closing request to the actual closing state. A fuel cell system characterized by the following.

8. In the fuel cell system of claim 1 or 2, The surface in the direction in which gravity acts in the first dilution portion and the surface in the direction in which gravity acts in the second dilution portion are formed parallel to the ground. A fuel cell system characterized by the following.

9. In the fuel cell system of claim 1 or 2, The fuel exhaust gas dilution section includes a third dilution section that houses the second dilution section. The case forming the third dilution section has the fuel exhaust gas discharge hole formed therein. A fuel cell system characterized by the following.

Images