Fuel cell system

Abstract

To provide a fuel cell system capable of sufficiently securing a circulation flow rate of a reaction off-gas to a gas supply passage even if an upstream pressure of an injector is high.SOLUTION: In a fuel cell system 1 comprising: an FC stack 11; a hydrogen supply passage 31; a hydrogen discharge passage 32; a hydrogen circulation passage 34; an injector 63 disposed in the hydrogen supply passage 31; an ejector 64 which is disposed at a position in the hydrogen supply passage 31 at a downstream side of the injector 63 and by which a hydrogen gas injected by the injector 63 and a hydrogen off-gas circulated by the hydrogen circulation passage 34 are mixed and ejected; and an exhaustion / drainage valve 72 which is disposed in the hydrogen discharge passage 32 and controls the discharge of the hydrogen off-gas to the outside, included is a control section 12 which controls the injector 63 and the exhaustion / drainage valve 72, and the control section 12 brings the exhaustion / drainage valve 72 into an open state synchronously with timing in which the hydrogen gas is injected from the injector 63.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a fuel cell system having a fuel cell that generates electricity by receiving supplies of a fuel gas and an oxidant gas.

Background Art

[0002] Patent Document 1 discloses a fuel cell system having a supply passage that supplies a reaction gas to a fuel cell, a circulation passage that circulates reaction off-gas discharged from the fuel cell to the supply passage, and an ejector provided at a connection portion between the supply passage and the circulation passage.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the fuel cell system disclosed in Patent Document 1, when the upstream pressure of the injector is low, the pressure difference between the upstream and downstream of the ejector becomes small, the suction pressure of the reaction off-gas in the ejector becomes small, and there is a possibility that the circulation flow rate of the reaction off-gas to the supply passage cannot be sufficiently ensured.

[0005] Therefore, the present disclosure has been made to solve the above-described problems, and an object thereof is to provide a fuel cell system that can sufficiently ensure the circulation flow rate of the reaction off-gas to the gas supply passage even when the upstream pressure of the injector is low.

Means for Solving the Problems

[0006] One aspect of the present disclosure made to solve the above problems includes a fuel cell, a gas supply passage for supplying a reaction gas to the fuel cell, a gas discharge passage for discharging the reaction off-gas discharged from the fuel cell to the outside, a gas circulation passage for circulating at least a part of the reaction off-gas from the gas discharge passage to the gas supply passage, an injector disposed in the gas supply passage for injecting the reaction gas, and an ejector disposed at a position downstream of the injector in the gas supply passage for mixing and discharging the reaction gas injected by the injector and the reaction off-gas circulated by the gas circulation passage. In a fuel cell system having an exhaust drain valve disposed in the gas discharge passage for controlling the discharge of the reaction off-gas to the outside, the fuel cell system has a control unit for controlling the injector and the exhaust drain valve, and the control unit opens the exhaust drain valve in synchronization with the timing of injecting the reaction gas from the injector.

[0007] According to this aspect, when the reaction gas is injected from the injector, at the same time, by opening the exhaust drain valve, a part of the reaction off-gas is discharged from the gas discharge passage to the outside, so that the pressure in the gas discharge passage decreases, and the downstream pressure of the ejector can be reduced. Therefore, even if the upstream pressure of the injector is low, a sufficient pressure difference between the upstream and downstream of the ejector can be ensured. Accordingly, the flow rate of the reaction off-gas sucked from the gas circulation passage to the ejector due to the negative pressure generated in the ejector increases, so that a sufficient circulation flow rate of the reaction off-gas from the gas circulation passage to the gas supply passage can be ensured. And thereby, the discharge of the mixed gas of the reaction gas and the reaction off-gas from the ejector is promoted, and the discharge amount of the ejector can be ensured.

Advantages of the Invention

[0008] According to the fuel cell system of the present disclosure, even if the upstream pressure of the injector is low, a sufficient circulation flow rate of the reaction off-gas to the gas supply passage can be ensured.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0010] An embodiment of the fuel cell system of the present disclosure will be described.

[0011] (Configuration of Fuel Cell System) As shown in FIG. 1, the fuel cell system 1 of this embodiment has an FC stack 11. Further, the fuel cell system 1 has a hydrogen system 21 and an air system 22. Note that the FC stack 11 is an example of the "fuel cell" of the present disclosure.

[0012] The FC stack 11 generates electricity by receiving the supply of fuel gas and the supply of oxidant gas. In this embodiment, the fuel gas is hydrogen gas and the oxidant gas is air (that is, air). That is, the FC stack 11 generates electricity by receiving the supply of hydrogen gas from the hydrogen system 21 and the supply of air from the air system 22. Then, the electric power generated by the FC stack 11 is supplied to a battery or an inverter (not shown). Note that the fuel gas and the hydrogen gas are examples of the "reaction gas" of the present disclosure.

[0013] The hydrogen system 21 is provided on the anode side of the FC stack 11. This hydrogen system 21 includes a hydrogen supply passage 31, a hydrogen discharge passage 32, a hydrogen filling passage 33, and a hydrogen circulation passage 34. Note that the hydrogen supply passage 31 is an example of the "gas supply passage" of the present disclosure, and the hydrogen discharge passage 32 is an example of the "gas discharge passage" of the present disclosure. Further, the hydrogen filling passage 33 is an example of the "gas filling passage" of the present disclosure, and the hydrogen circulation passage 34 is an example of the "gas circulation passage" of the present disclosure.

[0014] The hydrogen supply passage 31 is a passage for supplying hydrogen gas from a hydrogen tank 41 in which hydrogen gas is stored to the FC stack 11. The hydrogen discharge passage 32 is a passage for discharging hydrogen gas (i.e., hydrogen off-gas) discharged from the FC stack 11 to the outside. Note that the hydrogen off-gas is an example of the "reaction off-gas" of the present disclosure.

[0015] The hydrogen filling passage 33 is a passage for filling the hydrogen tank 41 with hydrogen gas from a filling port 51. The hydrogen circulation passage 34 is a passage connecting the hydrogen discharge passage 32 (specifically, a gas-liquid separator 71) and an ejector 64, and is a passage for circulating at least a part of the hydrogen off-gas from the hydrogen discharge passage 32 to the ejector 64 in the hydrogen supply passage 31 and supplying it.

[0016] Further, the hydrogen system 21 includes a valve 61, a pressure reducing valve 62, an injector 63, and an ejector 64 in this order from the hydrogen tank 41 side in the hydrogen supply passage 31.

[0017] The valve 61 is a valve that switches between supplying and blocking the supply of hydrogen gas from the hydrogen tank 41 to the hydrogen supply passage 31. The pressure reducing valve 62 is a pressure regulating valve for reducing the pressure of hydrogen gas. The injector 63 is a device that injects hydrogen gas led from the hydrogen tank 41 to the downstream side.

[0018] The ejector 64 is disposed at a position downstream of the injector 63 in the hydrogen supply passage 31 (i.e., downstream in the flow direction of the hydrogen gas). This ejector 64 is a device that generates a negative pressure in the hydrogen gas injected from the injector 63, mixes the hydrogen gas injected by the injector 63 with the hydrogen off-gas circulated by the hydrogen circulation passage 34, and discharges the mixture downstream.

[0019] Also, the hydrogen system 21 includes a gas-liquid separator 71 and an exhaust drain valve 72 in the hydrogen discharge passage 32 in order from the FC stack 11 side. The gas-liquid separator 71 is a device that separates moisture in the hydrogen off-gas. The exhaust drain valve 72 is a valve that switches between discharging and blocking the hydrogen off-gas and moisture from the gas-liquid separator 71. That is, the exhaust drain valve 72 is disposed in the hydrogen discharge passage 32 and is a valve that controls the discharge of the hydrogen off-gas to the outside.

[0020] On the other hand, the air system 22 is provided on the cathode side of the FC stack 11. This air system 22 includes an air supply passage 81 and an air discharge passage 82. The air supply passage 81 is a passage for supplying air from the outside of the fuel cell system 1 to the FC stack 11. The air discharge passage 82 is a passage for discharging the air (i.e., air off-gas) discharged from the FC stack 11.

[0021] Also, the air system 22 includes an air compressor 91 and a supply-side air valve 92 in the air supply passage 81. The air compressor 91 is a device that supplies air to the FC stack 11. The supply-side air valve 92 is a valve that switches between supplying and blocking the air from the air supply passage 81 to the FC stack 11.

[0022] Also, the air system 22 has a discharge-side air valve 101 disposed in the air discharge passage 82. The discharge-side air valve 101 is a valve that switches between discharging and blocking the air off-gas from the FC stack 11 to the air discharge passage 82.

[0023] Also, the fuel cell system 1 has a fan 111 for cooling the FC stack 11.

[0024] Furthermore, the fuel cell system 1 includes a control unit 12. The control unit 12 is a device having, for example, an arithmetic processing unit such as a CPU, a storage unit such as a ROM that stores a control program, control data, etc. processed by the CPU, and a RAM used as various work areas for control processing, and an input / output interface unit. Then, the control unit 12 performs various controls of the fuel cell system 1 according to the control program stored in the storage unit.

[0025] In the present embodiment, as various controls of the fuel cell system 1, the control unit 12 controls a valve 61, a pressure reducing valve 62, an injector 63, a gas-liquid separator 71, an exhaust and drain valve 72, an air compressor 91, a supply-side air valve 92, a discharge-side air valve 101, a fan 111, etc.

[0026] (Operation of the fuel cell system) In the fuel cell system 1 configured as described above, the hydrogen gas supplied from the hydrogen supply passage 31 to the FC stack 11 is discharged to the outside of the fuel cell system 1 through the hydrogen discharge passage 32 as hydrogen off-gas after being used for power generation in the FC stack 11. Also, the air supplied from the air supply passage 81 to the FC stack 11 is discharged to the outside of the fuel cell system 1 through the air discharge passage 82 as air off-gas after being used for power generation in the FC stack 11.

[0027] (Regarding the circulation flow rate of hydrogen off-gas) When the upstream pressure of the injector 63 is low, the pressure difference between the upstream and downstream of the ejector 64 becomes small, the suction pressure of the hydrogen off-gas in the ejector 64 becomes small, and the circulation flow rate of the hydrogen off-gas from the hydrogen circulation passage 34 to the hydrogen supply passage 31 may decrease. Then, the discharge amount of the hydrogen gas (specifically, the mixed gas of hydrogen gas and hydrogen off-gas) in the ejector 64 cannot be sufficiently obtained, and there is a possibility that the supply flow rate of the hydrogen gas to the FC stack 11 may be insufficient.

[0028] Therefore, in the present embodiment, as shown in FIG. 2, the control unit 12 opens the exhaust and drainage valve 72 in synchronization with the timing of injecting hydrogen gas from the injector 63 (that is, the timing when the injection of the injector 63 becomes ON in FIG. 2).

[0029] As shown in FIG. 2, in the opening / closing operation of the exhaust and drainage valve 72 and the circulation flow rate, the solid line indicates the present embodiment, and the broken line indicates a comparative example (that is, an example in which the exhaust and drainage valve 72 is opened without synchronization with the timing of injecting hydrogen gas from the injector 63).

[0030] In this way, when hydrogen gas is injected from the injector 63 and supplied to the ejector 64, at the same time, the exhaust and drainage valve 72 is opened. As a result, a part of the hydrogen off-gas is discharged from the hydrogen discharge passage 32 to the outside of the fuel cell system 1, so that the pressure in the hydrogen discharge passage 32 is reduced, and the downstream pressure of the ejector 64 can be lowered. Therefore, even if the upstream pressure of the ejector 64 is low, a sufficient pressure difference between the upstream and downstream of the ejector 64 can be ensured.

[0031] For example, as shown in FIG. 2, by opening the exhaust and drainage valve 72 in synchronization with the timing of injecting hydrogen gas from the injector 63, the downstream pressure of the ejector 64 can be lowered, and the downstream pressure (measured value) of the ejector 64 can be kept between the upper limit target downstream pressure (for example, 150 kPa.abs) and the lower limit target downstream pressure (for example, 130 kPa.abs). Therefore, even when the upstream pressure (measured value) of the injector 63 is low (for example, 200 kpa.abs), a sufficient pressure difference between the upstream and downstream of the ejector 64 can be ensured.

[0032] Therefore, since the flow rate of the hydrogen off-gas sucked from the hydrogen circulation passage 34 into the ejector 64 increases due to the negative pressure generated in the ejector 64, the circulation flow rate of the hydrogen off-gas from the hydrogen circulation passage 34 to the ejector 64 can be sufficiently ensured. Thus, the discharge of the mixed gas of hydrogen gas and hydrogen off-gas from the ejector 64 is promoted, and the discharge amount of the ejector 64 can be sufficiently ensured. In this way, even if the upstream pressure of the injector 63 is low, the circulation flow rate of the reaction off-gas to the hydrogen supply passage 31 can be sufficiently ensured. Therefore, the supply flow rate of hydrogen gas to the FC stack 11 can be sufficiently ensured, and stable power generation can be performed in the FC stack 11.

[0033] Also, the water accumulated in the gas-liquid separator 71 can be discharged to the outside, and at the same time, the hydrogen concentration of the hydrogen off-gas circulated from the hydrogen circulation passage 34 to the ejector 64 can be increased. Therefore, the hydrogen concentration of the mixed gas discharged from the ejector 64 can be adjusted to a predetermined concentration.

[0034] Further, as a modification, as shown in FIG. 3, in addition to opening the exhaust and drain valve 72 in synchronization with the timing of injecting hydrogen gas from the injector 63, the control unit 12 may open the exhaust and drain valve 72 at the timing when a predetermined amount or more of water accumulates in the gas-liquid separator 71 or at the timing when the hydrogen concentration of the hydrogen off-gas can be adjusted to a predetermined concentration. Thereby, the water accumulated in the gas-liquid separator 71 can be discharged to the outside from the hydrogen discharge passage 32 at an appropriate timing, so that the function of stably separating the gas and the liquid in the gas-liquid separator 71 can be exhibited. Also, hydrogen off-gas with an appropriate hydrogen concentration can be circulated from the hydrogen circulation passage 34 to the ejector 64.

[0035] Note that the above-described embodiments are merely examples and do not limit the present disclosure in any way. It goes without saying that various improvements and modifications are possible without departing from the gist thereof.

[0036] For example, in the example shown in FIG. 2, the control unit 12 opens the exhaust and drain valve 72 in synchronization with the timing of injecting hydrogen gas from the injector 63 every time at the timing of injecting hydrogen gas from the injector 63. However, the present invention is not limited to this. Among the timings of injecting hydrogen gas from the injector 63, at the timing when a predetermined amount or more of water has accumulated in the gas-liquid separator 71, the exhaust and drain valve 72 may be opened in synchronization with that timing. Thereby, while discharging the water accumulated in the gas-liquid separator 71 to the outside from the hydrogen discharge passage 32 at a more appropriate timing, even if the upstream pressure of the injector 63 is low, a sufficient circulation flow rate of the reaction off-gas to the hydrogen supply passage 31 can be ensured.

Explanation of Reference Numerals

[0037] 1 Fuel cell system 11 FC stack 12 Control unit 21 Hydrogen system 22 Air system 31 Hydrogen supply passage 32 Hydrogen discharge passage 34 Hydrogen circulation passage 41 Hydrogen tank 63 Injector 64 Ejector 72 Exhaust and drain valve

Claims

【Claim 1】 A fuel cell, a gas supply passage for supplying a reaction gas to the fuel cell, a gas discharge passage for discharging reaction off-gas discharged from the fuel cell to the outside, a gas circulation passage for circulating at least a part of the reaction off-gas from the gas discharge passage to the gas supply passage, an injector disposed in the gas supply passage for injecting the reaction gas, an ejector disposed at a position downstream of the injector in the gas supply passage for mixing and discharging the reaction gas injected by the injector and the reaction off-gas circulated by the gas circulation passage, an exhaust and drain valve disposed in the gas discharge passage for controlling the discharge of the reaction off-gas to the outside, in a fuel cell system having: a control unit for controlling the injector and the exhaust and drain valve, the control unit opening the exhaust and drain valve in synchronization with the timing of injecting the reaction gas from the injector, a fuel cell system characterized by the above.

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