Fuel gas supply system

Abstract

To provide a technology that can supply an appropriate amount of fuel gas to a gas supply destination.SOLUTION: A fuel gas supply system includes: a fuel tank that stores fuel gas; a fuel gas supply pipe that connects the fuel tank and a gas supply destination to which the fuel gas is supplied; an upstream strainer that is provided in the fuel gas supply pipe; and a downstream strainer that is entirely mesh-shaped and is provided in the fuel gas supply pipe that is downstream of the upstream strainer. The upstream strainer has a pocket portion having a mesh portion defined by a plurality of first openings, and a wall portion having a plurality of second openings that are larger in size than the first openings. When the upstream strainer is viewed along an axial direction of the upstream strainer, the plurality of first openings and the plurality of second openings do not overlap.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a fuel gas supply system. [Background technology]

[0002] Patent Document 1 discloses a strainer that is connected midway along a refrigerant pipe through which a refrigerant flows, and captures foreign matter flowing inside the refrigerant pipe. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-192152 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a fuel cell system that supplies fuel gas stored in a fuel tank to a gas supply destination. One known fuel cell system includes a fuel gas supply pipe that connects the fuel tank and a fuel cell stack to which the fuel gas is supplied, and a cylindrical mesh-like strainer that is provided on the fuel gas supply pipe. In such a fuel gas supply system, the fuel gas flowing through the fuel gas supply pipe may contain water vapor. In this case, ice crystals are formed at low temperatures and are collected on the strainer. If a large number of ice crystals are collected on the strainer, it becomes difficult for the fuel gas to pass through the strainer. As a result, a sufficient amount of fuel gas is not supplied to the gas supply destination.

[0005] The present specification provides a technique that can supply an appropriate amount of fuel gas to a gas supply destination. [Means for solving the problem]

[0006] In a first aspect disclosed in the present specification, a fuel gas supply system may include a fuel tank that stores fuel gas, a fuel gas supply pipe that connects the fuel tank to a gas supply destination to which the fuel gas is supplied, an upstream strainer provided in the fuel gas supply pipe, and a downstream strainer that is provided in the fuel gas supply pipe downstream of the upstream strainer and has an overall mesh-like structure. The upstream strainer may have a mesh-like pocket portion defined by a plurality of first openings and a wall portion having a plurality of second openings that are larger in size than the first openings. When the upstream strainer is viewed along the axial direction of the upstream strainer, the plurality of first openings and the plurality of second openings may not overlap.

[0007] According to the above configuration, ice crystals flowing through the fuel gas supply pipe are trapped in the pocket portion of the upstream strainer. Because the second openings in the wall portion are larger than the first openings, ice crystals are not trapped in the wall portion. Furthermore, when the upstream strainer is viewed axially, the first openings and the second openings do not overlap. Therefore, even if many ice crystals are trapped in the pocket portion, the wall portion ensures a path through which the fuel gas can pass. Therefore, an appropriate amount of fuel gas can be supplied to the gas supply destination.

[0008] In a second aspect, in the first aspect, the gas supply destination may be a fuel cell stack. The fuel gas supply system may further include an ejector provided in the fuel gas supply piping, and a circulation piping connecting the fuel cell stack and the ejector. The fuel gas supply piping may include an upstream fuel gas supply piping connecting the fuel tank and the ejector, and a downstream fuel gas supply piping connecting the ejector and the fuel cell stack. The upstream strainer and the downstream strainer may be provided in the downstream fuel gas supply piping.

[0009] In the above configuration, unreacted fuel gas that is not used to generate electricity in the fuel cell stack flows into the fuel gas supply pipe via the circulation pipe. Hereinafter, unreacted fuel gas will be referred to as "off gas." Off gas contains water vapor. Therefore, at low temperatures, ice crystals flow through the fuel gas supply pipe as a mixture of fuel gas and off gas flows through the fuel gas supply pipe. Ice crystals are trapped in the pockets of the upstream strainer, but are not trapped on the wall of the upstream strainer, so an appropriate amount of fuel gas can be supplied to the gas supply destination.

[0010] In a third aspect, in the first or second aspect, when the upstream strainer is viewed along the axial direction, the pocket portion may be provided in the center of the upstream strainer, and the wall portion may be provided outside the pocket portion.

[0011] In fuel gas supply piping, ice crystals tend to flow through the center of the fuel gas supply piping. With the above configuration, the amount of ice crystals that can be captured by the upstream pocket can be increased. Therefore, it is possible to prevent a large amount of ice crystals from being captured by the downstream strainer, which makes it difficult for the fuel gas to pass through the downstream strainer.

[0012] In a fourth aspect, in the third aspect, the wall portion may be inclined downstream from the outside toward the inside.

[0013] According to the above configuration, the fuel gas can easily pass through the plurality of second openings.

[0014] In a fifth aspect, in any one of the first to fourth aspects, the mesh portion may be made of a metal material.

[0015] With the above configuration, the temperature of the mesh portion increases more easily than when the mesh portion is made of resin, etc. This makes it easier for ice crystals trapped in the mesh portion to melt, allowing ice crystals trapped in the pockets of the upstream strainer to melt relatively quickly. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram of a fuel cell system 2 according to an embodiment. [Figure 2] FIG. 4 is a cross-sectional view of a third supply pipe 32 according to the embodiment. [Figure 3] FIG. 2 is a perspective view of an upstream strainer 36 according to the embodiment. [Figure 4] 4 is a time chart of the temperature of gas flowing through the third supply pipe 32 in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] A fuel cell system 2 will be described with reference to Fig. 1. The fuel cell system 2 includes a fuel tank 10, an injector 20, an ejector 30, a fuel cell stack 60, a gas-liquid separator 70, and an ECU 100. The fuel cell system 2 is mounted on, for example, a fuel cell vehicle. Hydrogen gas, which is a fuel gas, is stored in the fuel tank 10.

[0018] The fuel cell stack 60 is a device that generates electricity through a chemical reaction between hydrogen and oxygen. Water is produced by the chemical reaction between hydrogen and oxygen. The fuel cell stack 60 includes a plurality of unit cells (not shown). Each unit cell includes a fuel electrode and an air electrode, and generates electricity by supplying fuel gas to the fuel electrode and air containing oxygen to the air electrode. The electricity generated by the fuel cell stack 60 is supplied to, for example, a traction motor of a fuel cell vehicle. Off-gas not used in power generation in the fuel cell stack 60 is discharged from the fuel cell stack 60. The off-gas contains water vapor.

[0019] The upstream end of a first supply pipe 12 is connected to the fuel tank 10. The downstream end of the first supply pipe 12 is connected to the upstream part of the injector 20. A main stop valve 14 and a pressure reducing valve 16 are provided on the first supply pipe 12, in that order from the upstream side to the downstream side. The main stop valve 14 opens and closes the first supply pipe 12. When the main stop valve 14 is opened, fuel gas is supplied from the fuel tank 10 to the fuel cell stack 60. When the main stop valve 14 is closed, the supply of fuel gas from the fuel tank 10 to the fuel cell stack 60 is stopped. The pressure reducing valve 16 adjusts the pressure of the fuel gas flowing through the first supply pipe 12.

[0020] The injector 20 adjusts the pressure and flow rate of the fuel gas supplied to the fuel cell stack 60. The injector 20 is, for example, a solenoid valve. When the injector 20 opens, the fuel gas is supplied to the fuel cell stack 60, and when the injector 20 closes, the supply of the fuel gas to the fuel cell stack 60 is stopped. The pressure and flow rate of the fuel gas are adjusted by adjusting the opening degree and open time of the injector 20. The upstream end of the second supply pipe 22 is connected to the downstream part of the injector 20. The downstream end of the second supply pipe 22 is connected to the ejector 30.

[0021] The ejector 30 is connected to an upstream end of a third supply pipe 32. The downstream end of the third supply pipe 32 is connected to the fuel cell stack 60. The third supply pipe 32 is provided with a pressure sensor 34 that detects the pressure of the mixed gas of fuel gas and off-gas introduced into the fuel cell stack 60.

[0022] As shown in FIG. 2, the third supply pipe 32 is provided with an upstream strainer 36 and a downstream strainer 38, in that order from upstream to downstream. The upstream strainer 36 and the downstream strainer 38 extend along the flow path axis of the third supply pipe 32. The upstream strainer 36 includes a first pocket portion 40 having a first mesh portion 40A (the gray portion in FIGS. 2 and 3) and a gas passage portion 42 having a plurality of slits 42A. The first mesh portion 40A has a plurality of first pocket openings (not shown). The first mesh portion 40A is made of a metal material such as stainless steel. As shown in FIG. 3, the first pocket portion 40 has a cylindrical shape with a bottom. The gas passage portion 42 has a tubular shape. The diameter of the gas passage portion 42 decreases from the upstream side to the downstream side. The diameter of the upstream end of the gas passage portion 42 is the same as the diameter of the third supply pipe 32. The diameter of the downstream end of the gas passage 42 is the same as the diameter of the first pocket 40. The slits 42A are aligned in the circumferential direction. The size of the slits 42A is larger than the size of each of the mesh openings. The size of the slits 42A is set to a size that allows ice crystals to pass through. The slits 42A are positioned radially outward of the pocket 44. Therefore, when the upstream strainer 36 is viewed along the flow path axis of the upstream strainer 36, the slits 42A and the pocket openings do not overlap.

[0023] As shown in FIG. 2, the downstream strainer 38 includes a second pocket portion 50 having a second mesh portion 50A (the gray portion in FIG. 2). The second mesh portion 50A has a plurality of second pocket openings (not shown). The second pocket portion 50 has a cylindrical shape with a bottom. The second pocket portion 50 has a truncated cone shape whose diameter decreases from the upstream side to the downstream side. The diameter of the upstream end of the second pocket portion 50 is the same as the diameter of the third supply pipe 32. The second mesh portion 50A is provided on the entire side portion and bottom portion of the downstream strainer 38. In this way, the entire downstream strainer 38 can be said to be mesh-like.

[0024] As shown in FIG. 1 , the ejector 30 is further connected to the upstream end of a gas circulation pipe 72. As will be described later, off-gas is supplied to the gas circulation pipe 72. The ejector 30 uses the flow of fuel gas supplied from the second supply pipe 22 to suck in the off-gas flowing through the gas circulation pipe 72, mixes these gases, and discharges them to the third supply pipe 32. The gas discharged to the third supply pipe 32 is then supplied to the fuel cell stack 60. Note that hereinafter, the first supply pipe 12, the second supply pipe 22, and the third supply pipe 32 may be collectively referred to as the "fuel gas supply pipes."

[0025] The downstream end of an air supply pipe 80 is connected to the fuel cell stack 60. The upstream end of the air supply pipe 80 is open to the outside. A compressor 82 is provided in the air supply pipe 80. The compressor 82 compresses and sends the air introduced into the air supply pipe 80 to the fuel cell stack 60. For example, air from outside the fuel cell vehicle is supplied to the fuel cell stack 60 through the air supply pipe 80.

[0026] The upstream end of an exhaust gas pipe 62 is connected to the fuel cell stack 60. The downstream end of the exhaust gas pipe 62 is connected to the gas-liquid separator 70. Off-gas is supplied to the gas-liquid separator 70 through the exhaust gas pipe 62. The upstream end of an air discharge pipe 84 is connected to the fuel cell stack 60. The upstream end of the air discharge pipe 84 is open to the outside. Air not used for power generation in the fuel cell stack 60 passes through the air discharge pipe 84 and is released to the outside.

[0027] The gas-liquid separator 70 separates and stores water contained in the off-gas introduced into the gas-liquid separator 70 from the exhaust gas piping 62. The water vapor contained in the off-gas introduced into the gas-liquid separator 70 is cooled, and condensed water (liquid water) is stored in the gas-liquid separator 70. For example, the water vapor is cooled by outside air, and condensed water (liquid water) is stored in the gas-liquid separator 70.

[0028] The upstream end of a gas circulation pipe 72 is connected to the gas-liquid separator 70. The off-gas in the gas-liquid separator 70 is supplied to the ejector 30 through the gas circulation pipe 72. The off-gas introduced into the ejector 30 contains water vapor that was not stored in the gas-liquid separator 70. The off-gas introduced into the ejector 30 is supplied again to the fuel cell stack 60 through the third supply pipe 32. As a result, the off-gas discharged from the fuel cell stack 60 is supplied again to the fuel cell stack 60 and used for power generation.

[0029] In addition, the upstream end of an exhaust drainage channel 76 is connected to the gas-liquid separator 70. The downstream end of the exhaust drainage channel 76 is open to the outside. An exhaust drainage valve 78 is provided in the exhaust drainage channel 76. When the exhaust drainage valve 78 is opened, unnecessary gas (mainly nitrogen gas) and liquid water in the gas-liquid separator 70 flow to the outside. When the exhaust drainage valve 78 is closed, unnecessary gas (mainly nitrogen gas) and liquid water in the gas-liquid separator 70 do not flow to the outside.

[0030] The ECU 100 includes a CPU and memories such as a ROM and a RAM. The ECU 100 identifies the load (required load) required of the fuel cell system 2, and controls the operation of the injector 20, etc., so as to obtain the required current.

[0031] The gas temperature when the fuel cell system 2 operates at low temperatures will be described with reference to Fig. 4. The gas temperature is the temperature of the mixed gas flowing through the third supply pipe 32. Low temperatures refer to a situation below 0°C, and Fig. 4 will explain the situation at -35°C as an example.

[0032] At time T0 in FIG. 4, when the fuel cell system 2 is activated, the fuel gas stored in the fuel tank 10 is supplied to the fuel cell stack 60 via the injector 20 and the ejector 30. The off-gas is also resupplied to the fuel cell stack 60 via the gas-liquid separator 70 and the ejector 30. At this time, the gas temperature is −35° C. In this case, some of the water vapor contained in the mixed gas turns into fine ice crystals. Most of the ice crystals flowing through the center of the third supply pipe 32 are collected in the first pocket 40 of the upstream strainer 36. Some of the ice crystals flowing outside the center of the third supply pipe 32 pass through the slits 42A of the gas passage 42. This is because the slits 42A are designed to be large enough for the ice crystals to pass through. The ice crystals that pass through the slits 42A are collected in the second pocket 50 of the downstream strainer 38. Thereafter, as long as the gas temperature remains below 0°C, ice crystals are collected in the first pocket 40 and the second pocket 50. In this embodiment, most ice crystals are collected in the first pocket 40, and a relatively small amount of ice crystals is collected in the second pocket 50. This prevents the downstream strainer 38 from being blocked by ice crystals. Furthermore, the gas passage 42 of the upstream strainer 36 does not collect ice crystals. Therefore, even if many ice crystals are collected in the first pocket 40 of the upstream strainer 36, the multiple slits 42A ensure a flow path for the mixed gas. This ensures that the amount of mixed gas supplied to the fuel cell stack 60 is not insufficient.

[0033] Thereafter, slightly before time T1, the temperature of the mixed gas begins to rise. As an example, the interval between time T0 and time T1 is approximately 20 seconds. Then, at time T1, the temperature of the mixed gas reaches 0°C. In this case, ice crystals no longer form, and the ice crystals trapped in the first pocket portion 40 also melt. Thus, in this embodiment, even when the fuel cell system 2 operates at low temperatures, the third supply pipe 32 does not become clogged.

[0034] As described above, the fuel cell system 2 (an example of a "fuel gas supply system") includes a fuel tank 10 that stores fuel gas, a fuel gas supply pipe that connects the fuel tank 10 to a fuel cell stack 60 (a "gas supply destination") to which the fuel gas is supplied, an upstream strainer 36 provided in the fuel gas supply pipe, and a downstream strainer 38 that is entirely mesh-shaped and provided in the fuel gas supply pipe downstream of the upstream strainer 36. The upstream strainer 36 includes a first pocket portion 40 (an example of a "pocket portion") having a first mesh portion 40A (an example of a "mesh portion") defined by a plurality of first openings, and a gas passage portion 42 (a "wall portion") having a plurality of slits 42A (an example of a "plurality of second openings") that are larger in size than the first openings. When the upstream strainer 36 is viewed along the axial direction of the upstream strainer 36, the plurality of first openings and the plurality of slits 42A do not overlap.

[0035] According to the above configuration, ice crystals flowing through the fuel gas supply pipe are collected in the first pocket portion 40 of the upstream strainer 36. Because the slits 42A of the gas passage portion 42 are larger than the first openings, ice crystals are not collected in the gas passage portion 42. Furthermore, when the upstream strainer 36 is viewed axially, the first openings and the slits 42A do not overlap. Therefore, even if many ice crystals are collected in the first pocket portion 40, the gas passage portion 42 ensures a path through which the fuel gas can pass. Therefore, an appropriate amount of fuel gas can be supplied to the gas supply destination.

[0036] The fuel cell system 2 further includes an ejector 30 provided in the fuel gas supply pipe, and an exhaust gas pipe 62 and a gas circulation pipe 72 (an example of a "circulation pipe") that connect the fuel cell stack 60 and the ejector 30. The fuel gas supply pipe includes a first supply pipe 12 and a second supply pipe 22 (an example of an "upstream fuel gas supply pipe") that connect the fuel tank 10 and the ejector 30, and a third supply pipe 32 (an example of a "downstream fuel gas supply pipe") that connects the ejector 30 and the fuel cell stack 60. An upstream strainer 36 and a downstream strainer 38 are provided in the third supply pipe 32.

[0037] In the above configuration, the off-gas flows into the supply gas supply pipe via the exhaust gas pipe 62 and the gas circulation pipe 72. The off-gas contains water vapor. Therefore, at low temperatures, ice crystals flow through the fuel gas supply pipe as the mixed gas of fuel gas and off-gas flows through the fuel gas supply pipe. The ice crystals are collected in the first pocket portion 40 of the upstream strainer 36, but are not collected in the gas passage portion 42 of the upstream strainer 36, so that an appropriate amount of fuel gas can be supplied to the gas supply destination.

[0038] Furthermore, when the upstream strainer 36 is viewed along the axial direction, the first pocket portion 40 is provided in the center of the upstream strainer 36, and the gas passage portion 42 is provided outside the first pocket portion 40.

[0039] In the fuel gas supply pipe, ice crystals may easily flow through the center of the fuel gas supply pipe. With the above configuration, a large amount of ice crystals can be captured by the upstream first pocket portion 40. This prevents a large amount of ice crystals from being captured in the downstream strainer 38, making it difficult for the fuel gas to pass through the downstream strainer 38.

[0040] The gas passage 42 is inclined downstream from the outside to the inside.

[0041] According to the above configuration, the fuel gas can easily pass through the plurality of slits 42A.

[0042] The first mesh portion 40A is made of a metal material.

[0043] With the above configuration, the temperature of the first mesh portion 40A increases more easily than when the first mesh portion 40A is made of resin or the like. This makes it easier for ice crystals trapped in the first mesh portion 40A to melt. This allows ice crystals trapped in the first pocket portion 40 of the upstream strainer 36 to melt relatively quickly.

[0044] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0045] (First Modification) The first pocket portion 40 may have a bottomed prism shape, a pyramid shape, a cone shape, or the like.

[0046] (Second variant) When the upstream strainer 36 is viewed along the axial direction, the gas passage portion 42 may be provided in the center of the upstream strainer 36, and the first pocket portion 40 may be provided outside the gas passage portion 42.

[0047] (Third Modification) The gas passage portion 42 may extend in a direction perpendicular to the axial direction of the upstream strainer 36.

[0048] (Fourth Modification) The first mesh portion 40A may be made of a resin material.

[0049] (Fifth Modification) Three or more strainers may be arranged in the fuel gas supply pipe.

[0050] The technical elements described in this specification or drawings exhibit technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of those objectives is itself technically useful. [Explanation of symbols]

[0051] 2: fuel cell system, 10: fuel tank, 12: first supply pipe, 14: main stop valve, 16: pressure reducing valve, 20: injector, 22: second supply pipe, 30: ejector, 32: third supply pipe, 34: pressure sensor, 36: upstream strainer, 38: downstream strainer, 40: first pocket portion, 40A: first mesh portion, 42: gas passage portion, 42A: slit, 44: pocket portion, 50: second pocket portion, 50A: second mesh portion, 60: fuel cell stack, 62: exhaust gas pipe, 70: gas-liquid separator, 72: gas circulation pipe, 76: exhaust drainage channel, 78: exhaust drainage valve, 80: air supply pipe, 82: compressor, 84: air exhaust pipe, 100: ECU

Claims

1. A fuel gas supply system, comprising: a fuel tank for storing fuel gas; a fuel gas supply pipe connecting the fuel tank and a gas supply destination to which the fuel gas is supplied; an upstream strainer provided in the fuel gas supply pipe; a downstream strainer that is entirely mesh-shaped and is provided in the fuel gas supply pipe downstream of the upstream strainer, The upstream strainer is a pocket having a mesh portion defined by a plurality of first openings; a wall portion having a plurality of second openings larger in size than the first openings; It has When the upstream strainer is viewed along the axial direction of the upstream strainer, the plurality of first openings and the plurality of second openings do not overlap with each other. Fuel gas supply system.

2. the gas supply destination is a fuel cell stack, The fuel gas supply system includes: an ejector provided in the fuel gas supply pipe; a circulation pipe connecting the fuel cell stack and the ejector; Furthermore, the fuel gas supply pipe includes an upstream fuel gas supply pipe that connects the fuel tank and the ejector, and a downstream fuel gas supply pipe that connects the ejector and the fuel cell stack, The fuel gas supply system according to claim 1 , wherein the upstream strainer and the downstream strainer are provided on the downstream fuel gas supply pipe.

3. When the upstream strainer is viewed along the axial direction, The pocket portion is provided in a central portion of the upstream strainer, The fuel gas supply system according to claim 1 , wherein the wall portion is provided outside the pocket portion.

4. The fuel gas supply system according to claim 2 , wherein the wall portion is inclined downstream from the outside toward the inside.

5. The fuel gas supply system according to claim 1 , wherein the mesh portion is made of a metal material.

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