JP7267897B2 - fuel cell system - Google Patents

Description

The present invention relates to fuel cell systems.

An ejector is known that supplies fuel gas injected from an injector and fuel off-gas discharged from the fuel cell to the fuel cell. Liquid water may remain in such an ejector or in a supply pipe communicating between the ejector and the fuel cell. If the stagnant liquid water enters the fuel cell, it may affect the performance of the fuel cell. Moreover, if the retained liquid water freezes after the power generation of the fuel cell is stopped, it may affect the supply of fuel gas when power generation is started. Therefore, it is known to discharge such liquid water to a gas-liquid separator through a discharge pipe having one end connected to an ejector and the other end connected to a gas-liquid separator (Patent Document 1 reference).

Japanese Patent No. 5065866

If such a discharge pipe is connected from the outside of the ejector, the size of the entire system is increased. Further, by arranging such a discharge pipe so that at least part of it passes through the inside of the ejector, it is possible to suppress an increase in size. Liquid water may remain in the discharge pipe without being able to be discharged to the separator. In particular, when the power generation of the fuel cell is stopped, the supply of fuel gas to the fuel cell is also stopped, so the pressure difference between one end and the other end of the discharge pipe is reduced, and liquid water is separated into gas and liquid. It may not be possible to discharge to the vessel.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel cell system capable of discharging liquid water remaining between an ejector and a fuel cell to a gas-liquid separator with a simple configuration.

The object is to provide a fuel cell, an ejector including an inlet for sucking the fuel off-gas discharged from the fuel cell, an outlet for supplying the fuel gas together with the fuel off-gas to the fuel cell, and a gas-liquid separator located on the side of the fuel off-gas before being supplied to the ejector and storing the moisture; a first pipe connecting the discharge port of the ejector and the fuel cell; a second pipe connecting the suction port and the gas-liquid separator; and a discharge channel extending from the first pipe side to the second pipe side through the inside of the ejector, wherein the discharge channel is , having a first open end formed at one end and a second open end formed at the other end, defining a sealed space between the first open end and the second open end; The first opening end opens in the first pipe and is positioned at the lower end of the connecting portion between the first pipe and the ejector , and the first and second opening ends are the first and second opening ends of the discharge channel. This can be achieved by a fuel cell system located on the gravitational direction side of at least a portion of the portion between the first open end and the second open end. The second open end may be located inside the second pipe or inside the gas-liquid separator, and may be located closer to the gravitational direction than the first open end. The discharge channel may be formed by a cutout of a part of the ejector. Hydrophilic treatment may be applied to the inner surface of the discharge channel.

According to the present invention, it is possible to provide a fuel cell system capable of discharging liquid water remaining between an ejector and a fuel cell to a gas-liquid separator with a simple configuration.

FIG. 1 is a configuration diagram of a fuel cell system. FIG. 2 is a schematic diagram showing a cross section of the ejector. FIG. 3 is a schematic diagram showing a cross section of an ejector of a modified example. FIG. 4 is a schematic diagram showing a cross section of an ejector of a modification. 5A is a cross-sectional view of the discharge passage of FIG. 4, and FIGS. 5B and 5C are cross-sectional views of modified discharge passages. 6A-6E are cross-sectional views of modified discharge passages. 7A-7D are cross-sectional views of modified discharge passages.

[Configuration of fuel cell system]
FIG. 1 is a configuration diagram of a fuel cell system 1. As shown in FIG. The fuel cell system 1 is mounted on a vehicle, for example, and supplies electric power to a driving motor. The fuel cell system 1 includes a fuel cell (hereinafter referred to as FC) 4, a fuel gas supply system 20 that supplies fuel gas to the FC 4, an air compressor 14 that supplies oxidant gas to the FC 4, and a cooling system that cools the FC 4. A radiator 7 or the like is provided to promote heat dissipation of water. Although not shown in FIG. 1, the fuel cell system 1 also includes a power control system for controlling the power generated by the FC4. The FC4 is a fuel cell that generates electricity by being supplied with a cathode gas and an anode gas, and is configured in a stack by laminating a plurality of solid polymer electrolyte type single cells.

The air compressor 14 supplies oxygen-containing air, which is an oxidant gas, to the FC 4 from the oxidant gas supply port 43 via the supply pipe 13 . The oxidant gas supplied to the FC 4 is discharged from the oxidant gas outlet 44 to the outside through the oxidant gas discharge pipe 15 and the fuel gas discharge pipe 26 connected to the oxidant gas discharge pipe 15. The oxidant gas discharge pipe 15 is provided with a pressure regulating valve 16 for regulating the back pressure of the FC4. Incidentally, the rotational speed of the air compressor 14 and the opening degree of the pressure regulating valve 16 are controlled by a control unit (not shown) according to the power generated by the FC 4 .

The fuel gas supply system 20 supplies hydrogen gas as fuel gas to the FC 4 and includes a tank 21T, a fuel gas supply pipe 21, a connecting pipe 22, a reflux pipe 23, a gas-liquid separator 25, and a fuel gas discharge pipe 26. The tank 21T is connected to the ejector 24 via a pipe, and the ejector 24 is connected to the fuel gas supply port 41 of the FC4 via the fuel gas supply pipe 21. The fuel gas supply pipe 21 is an example of a first pipe. Hydrogen gas, which is anode gas, is stored in the tank 21T. The connecting pipe 22 connects the fuel gas outlet 42 of the FC 4 and the gas-liquid separator 25 . The gas-liquid separator 25 and the ejector 24 are connected by a reflux pipe 23 . The return pipe 23 is an example of a second pipe. The gas-liquid separator 25 is positioned closer to the gravity direction than the ejector 24 . One end of the fuel gas discharge pipe 26 is connected to the gas-liquid separator 25, and the other end of the fuel gas discharge pipe 26 is open to the outside air. Here, a discharge valve (not shown) is provided at the connecting portion between the gas-liquid separator 25 and the fuel gas discharge pipe 26. When the discharge valve is opened, the liquid water stored in the gas-liquid separator 25 is discharged as fuel. The gas is discharged to the outside through the gas discharge pipe 26 . The fuel gas supplied from the tank 21T to the FC 4 via the ejector 24 is discharged from the FC 4 as fuel off-gas. The fuel off-gas discharged from the FC4 is again introduced into the ejector 24 via the connecting pipe 22, the gas-liquid separator 25, and the reflux pipe 23, and is again fed to the FC4 together with the fuel gas supplied from the tank 21T through the ejector 24. supplied to The gas-liquid separator 25 separates and stores moisture from the fuel off-gas.

[Ejector configuration]
FIG. 2 is a schematic diagram showing a cross section of the ejector 24. As shown in FIG. In addition, the direction of gravity G is shown in FIG. The ejector 24 has a nozzle portion 241 , a suction portion 242 , a mixing portion 243 and a diffuser portion 244 . The nozzle portion 241 is connected to an injector (not shown) that injects fuel gas from the tank 21T. The return pipe 23 is connected to the suction portion 242 . The fuel gas injected from the injector passes through the ejector 24 via the nozzle portion 241 , and the fuel off-gas discharged from the FC 4 is sucked into the suction portion 242 . In the mixing section 243, the fuel gas injected from the injector and the fuel off-gas discharged from the FC4 are mixed. The gas mixed in the mixing section 243 flows through the diffuser section 244 . The diffuser portion 244 is formed such that its diameter gradually increases toward the downstream side. The fuel gas newly injected in the mixing section 243 and the fuel off-gas discharged from the FC 4 are mixed, and the hydrogen concentration becomes uniform in the process in which the mixed fuel flows through the diffuser section 244 . As a result, fuel gas having a uniform hydrogen concentration is supplied to the FC4.

Ejector 24 includes an outer wall portion 246 and an inner wall portion 247 . The inner wall portion 247 defines the suction portion 242 , the mixing portion 243 and the diffuser portion 244 inside and is housed in the outer wall portion 246 . A discharge pipe 30 is provided inside the ejector 24 . A part of the discharge pipe 30 is fixed to the lower surface of the diffuser section 244 in the direction of gravity G, and is provided so as not to affect the mixing of the fuel gas and the fuel off-gas in the mixing section 243 . The discharge pipe 30 extends into the fuel gas supply pipe 21 on the downstream side of the ejector 24, and the first open end 31 at one end contacts the liquid water W staying in the fuel gas supply pipe 21. , it is in contact with the bottom surface of the fuel gas supply pipe 21 . The first open end 31 opens inside the fuel gas supply pipe 21 and is positioned at the lower end of the connecting portion between the fuel gas supply pipe 21 and the ejector 24 . Here, the liquid water W stays in the lowest portion of the fuel gas supply pipe 21. Specifically, the end of the fuel gas supply pipe 21 connected to the discharge port of the ejector 24 staying in In other words, the portion where the liquid water W tends to stay is formed in the vicinity of the discharge port of the ejector 24 of the fuel gas supply pipe 21 . The first open end 31 faces the downstream side of the fuel gas supply pipe 21 .

Also, the discharge pipe 30 extends from the ejector 24 through the suction portion 242 into the return pipe 23 , and the second open end 32 at the other end is positioned inside the return pipe 23 . The second open end 32 faces the direction of gravity G and faces the gas-liquid separator 25 . Here, the second open end 32 is positioned in the direction of gravity G relative to the first open end 31 , and the first open end 31 and the second open end 32 are positioned closer to the ejector 24 than the discharge pipe 30 . It is located in the direction of gravity G. The discharge pipe 30 is open at a first open end 31 and a second open end 32 , but defines a sealed space from the first open end 31 to the second open end 32 . The discharge pipe 30 is an example of a discharge channel.

Here, while the fuel cell system 1 is in operation, the fuel gas intermittently injected from the injector and the fuel off-gas sucked therein pass through the diffuser portion 244 , while the fuel off-gas flows through the return pipe 23 . passes through. Therefore, the pressure inside the fuel gas supply pipe 21 tends to be higher than the pressure inside the reflux pipe 23 . Based on this pressure difference, the liquid water W can enter from the first open end 31 of the discharge pipe 30 and be discharged from the second open end 32 to the gas-liquid separator 25. Retention of liquid water W can be prevented. As described above, due to the positional relationship between the first opening end 31 and the second opening end 32, when the liquid water W is filled from the first opening end 31 to the second opening end 32 of the discharge pipe 30, the siphon In principle, the liquid water W is sucked through the first open end 31 and discharged through the second open end 32 . The liquid water W discharged from the second open end 32 is stored in the gas-liquid separator 25 . Such a simple configuration can prevent the liquid water W stored in the fuel gas supply pipe 21 from entering the FC 4, and also prevent the liquid water W from freezing in the fuel gas supply pipe 21 after power generation is stopped. can.

Further, when the power generation of the FC 4 is stopped and the fuel gas supply to the FC 4 is stopped, there is almost no pressure difference between the fuel gas supply pipe 21 and the return pipe 23 . However, even in this case, as long as the discharge pipe 30 is filled with the liquid water W, the liquid water W remaining in the fuel gas supply pipe 21 is sucked by the siphon principle and directed to the gas-liquid separator 25. The liquid water W can be discharged with a large amount of water, and the recovery rate of the liquid water W can be improved. Incidentally, while power generation is stopped, scavenging (purge) on the anode side using, for example, air as scavenging gas may be used together.

Thus, the discharge pipe 30 is arranged inside the fuel gas supply pipe 21 , the ejector 24 and the return pipe 23 . For this reason, an increase in size and complication of the structure are suppressed. Also, the diameter of the discharge pipe 30 is formed relatively small. As a result, the inside of the discharge pipe 30 can be filled with a small amount of liquid water W without affecting the flow of the fuel gas and the fuel off-gas, and the liquid water W can be quickly removed from the gas-liquid separator by the siphon principle. 25 can be discharged.

It is desirable that the second open end 32 is away from the suction portion 242 . If the second opening end 32 is close to the suction portion 242, there is a possibility that the liquid water W discharged from the second opening end 32 is sucked to the suction portion 242 side together with the fuel off-gas sucked to the suction portion 242 side. is. In the ejector 24, the mixing section 243 and the diffuser section 244 are installed in a horizontally continuous posture, but the diffuser section 244 may be positioned above or below the mixing section 243. can be located on the side.

Next, a plurality of modified examples will be described. FIG. 3 is a schematic diagram showing a cross section of an ejector 24a of a modified example. A second open end 32 a of the discharge pipe 30 a of the ejector 24 a is located inside the gas-liquid separator 25 . This can prevent the liquid water W discharged from the second opening end 32a from being sucked into the ejector 24a.

FIG. 4 is a schematic diagram showing a cross section of an ejector 24b of a modified example. The discharge passage 30b is a passage formed between the inner wall portion 247b and the outer wall portion 246, unlike the discharge pipes 30 and 30a described above. Specifically, a discharge passage 30b is defined by a bottom surface of the outer wall portion 246 on the side of the gravity direction G and a notch formed in the inner wall portion 247b. It extends to the vessel 25. Like the discharge pipes 30 and 30a, the discharge passage 30b also defines a sealed space from the first open end 31 to the second open end. The discharge passage 30b is an example of a discharge channel. 5A is a cross-sectional view of the discharge passage 30b of FIG. 4. FIG. The cross section of FIG. 5A shows a cross section perpendicular to the direction in which the discharge passage 30b extends. The cross-sectional shape of the discharge passage 30b is square, but is not limited to this, and may be rectangular. The discharge passage may be defined by forming a notch on the outer wall side instead of the inner wall side.

FIG. 5B is a cross-sectional view of a modified discharge passage 30c. The cross-sectional shape of the discharge passage 30c formed in the inner wall portion 247c is an equilateral triangle, but is not limited thereto, and may be an isosceles triangle or other triangles. FIG. 5C is a cross-sectional shape of a discharge passage 30d that is a modification. The cross-sectional shape of the discharge passage 30d formed in the inner wall portion 247d is a true semicircle, but may be a semi-ellipse.

FIG. 6A is a cross-sectional view of a modified discharge passage 30e. The discharge pipe 33 is accommodated in a discharge passage 30e having a square cross section formed in the inner wall portion 247e. The discharge pipe 33 has a circular cross-sectional shape. Although a seal member 34 is filled between the discharge pipe 33 and the discharge passage 30e, the present invention is not limited to this, and the seal member 34 may not be provided. In this case, the liquid water W flows through the discharge pipe 33 and between the discharge pipe 33 and the discharge passage 30e. The discharge pipe 33 is made of metal, but is not limited to this, and may be made of synthetic resin or rubber, for example.

FIG. 6B is a cross-sectional view of a modified discharge passage 30f. A discharge pipe 33f is accommodated in a discharge passage 30f having a rectangular cross section formed in the inner wall portion 247f. The discharge pipe 33f has an elliptical cross section and is press-fitted into the discharge passage 30f. The liquid water W flows through the discharge pipe 33f as well as the four corners between the discharge pipe 33f and the discharge passage 30f. Here, the channel cross-sectional area of this corner is smaller than the channel cross-sectional area of the discharge pipe 33f. Therefore, the amount of liquid water W required to fill from the first opening end to the second opening end of the corner is small, and the liquid water W can be quickly discharged using the siphon principle.

FIG. 6C is a cross-sectional view of a modified discharge passage 30g. A solid pipe 33g is accommodated in a discharge passage 30g having a square cross section formed in the inner wall portion 247g. Therefore, the liquid water W flows through the gap between the solid pipe 33g and the discharge passage 30g.

FIG. 6D is a cross-sectional view of a modified discharge passage 30h. A discharge pipe 33h is accommodated in a discharge passage 30h having a square cross section formed in the inner wall portion 247h. The discharge pipe 33h is made of synthetic resin.

FIG. 6E is a cross-sectional view of a modified discharge passage 30i. A discharge pipe 33i is accommodated in a discharge passage 30i formed in the inner wall portion 247i. The inner surface of the discharge pipe 33i is subjected to hydrophilic treatment to improve hydrophilicity. This makes it easier to introduce the liquid water W into the inner surface of the discharge pipe 33i, suppresses air from entering the discharge pipe 33i, and facilitates suction and discharge of the liquid water W by the above-described siphon principle.

FIG. 7A is a cross-sectional view of a modified discharge passage 30j. The discharge passage 30j is a notch having a square cross section formed in the inner wall portion 247j, and the inner surface of the discharge passage 30j is subjected to hydrophilic treatment. FIG. 7B is a cross-sectional view of a modified discharge passage 30k. The discharge passage 30k is a notch having an equilateral triangular cross-section formed in the inner wall portion 247k, and the inner surface of the discharge passage 30k is subjected to a hydrophilic treatment. FIG. 7C is a cross-sectional view of a modified discharge passage 30l. The discharge passage 30l is formed in the inner wall portion 247l and is a notch having a semi-perfect circular cross section, and the inner surface of the discharge passage 30l is subjected to a hydrophilic treatment.

FIG. 7D is a cross-sectional view of a modified discharge passage 30m. A solid pipe 33m is accommodated in a discharge passage 30m having a square cross section formed in the inner wall portion 247m. The outer surface of the solid tube 33m and the inner surface of the notch are subjected to a hydrophilic treatment. This also facilitates suction and drainage of the liquid water W by the siphon principle.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations can be made within the scope of the gist of the present invention described in the scope of claims. Change is possible.

1 fuel cell system 24 ejector 30 discharge pipe (discharge channel)
30b discharge passage (discharge channel)
31 first open end 32 second open end

Claims (4)

a fuel cell;
an ejector including an inlet for sucking the fuel off-gas discharged from the fuel cell and an outlet for supplying the fuel gas together with the fuel off-gas to the fuel cell;
a gas-liquid separator located on the side of the ejector in the gravitational direction and separating and storing moisture from the fuel off-gas before being supplied to the ejector;
a first pipe connecting the outlet of the ejector and the fuel cell;
a second pipe connecting the suction port of the ejector and the gas-liquid separator;
a discharge passage extending from the first pipe side to the second pipe side through the inside of the ejector,
The discharge channel has a first open end formed at one end and a second open end formed at the other end, and is sealed between the first open end and the second open end. define the space,
The first open end opens in the first pipe and is located at the lower end of the connection portion between the first pipe and the ejector ,
The fuel cell system, wherein the first and second open ends are located on the gravitational direction side of at least part of a portion of the discharge channel between the first open end and the second open end. 2. The fuel cell system according to claim 1, wherein said second open end is located inside said second pipe or inside said gas-liquid separator, and is located closer to the gravitational direction than said first open end. 3. The fuel cell system according to claim 1, wherein said discharge channel is formed by a cutout of said ejector. 4. The fuel cell system according to any one of claims 1 to 3, wherein the inner surface of said discharge channel is subjected to a hydrophilic treatment.

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