Fuel battery ejector

Abstract

To provide a technology that suppresses or prevents water generated inside a fuel battery ejector from entering the fuel battery.SOLUTION: An ejector 10 includes an inlet 12 for fuel gas, which is a driving gas, a suction port 14 for off-gas from a fuel battery, and a diffuser 20 having a discharge port for mixing the fuel gas and the off-gas and discharging the mixed gas. The diffuser 20 is provided with a movement promotion mechanism for promoting the movement of water in the diffuser 20 from the discharge port 28 toward the suction port 14 when the mixed gas is not being discharged.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to an ejector for a fuel cell. [Background technology]

[0002] In a fuel cell, fuel gas from a hydrogen source such as a hydrogen tank and off-gas discharged from the fuel cell containing unused hydrogen are sometimes mixed using an ejector and supplied to the fuel cell. For example, a technology for preventing pulsating gas flow when such hydrogen supply is performed has been disclosed (Patent Document 1). According to this technology, pulsating flow is prevented by balancing the force due to the gas flow rate with the water condensed at the outlet of the ejector, which sucks in the off-gas, mixes it with the drive gas, and discharges it. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-164886 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology of Patent Document 1, the outlet of the ejector for the mixed gas is located lower in the direction of gravity than the inlet. Even if the flow of the mixed gas stops, the water vapor remaining in the ejector may condense to produce water. In this case, there is a risk that the condensed water may enter the fuel cell from the ejector. If water enters the fuel cell, it may obstruct the gas flow in the fuel cell.

[0005] The present specification provides a technique for suppressing or preventing water produced inside an ejector of a fuel cell from entering the fuel cell. [Means for solving the problem]

[0006] The disclosure of this specification is embodied in an ejector for a fuel cell. The ejector introduces a mixed gas, which is a mixture of a fuel gas and an off-gas from the fuel cell, into the fuel cell. The ejector includes an inlet for the fuel gas, which is a driving gas, an inlet for the off-gas of the fuel cell, and a diffuser that mixes the fuel gas and the off-gas of the fuel cell and has an outlet for the mixed gas. The ejector further includes a movement promotion mechanism that promotes the movement of water inside the diffuser from the outlet toward the suction port when the mixed gas is not being discharged.

[0007] According to this ejector, a movement promotion mechanism is provided, and when the mixed gas is not being discharged, the movement of water from the mixed gas discharge port to the off-gas suction port is promoted. Therefore, the water is separated from the discharge port, and the intrusion of the water into the fuel cell is suppressed or avoided. The movement promotion mechanism can include, for example, making the interior of the diffuser more hydrophilic upstream than downstream, making the interior of the diffuser more water repellent downstream than upstream, the diffuser having an inclined surface that promotes the movement of water from upstream to downstream, and having fine protrusions inside the diffuser that promote the movement of water from upstream to downstream. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an overview of an example of an ejector disclosed in this specification. [Diagram 2] FIG. 13 is a diagram showing an outline of another example of an ejector disclosed in this specification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the ejector for supplying hydrogen to the fuel cell disclosed in this specification will be described with reference to the drawings as appropriate.

[0010] The ejector 10 of the fuel cell described below can constitute a part of a fuel cell system including a fuel cell having a stack in which many fuel cells are stacked in series. The fuel cell system can include, for example, an off-gas circulation system for circulating and utilizing the off-gas discharged from the fuel cell, a gas-liquid separator for the off-gas, and an injector for discharging fuel gas from a fuel gas tank to the ejector 10 in the ejector 10, as well as elements of a known fuel cell system, such as an oxidant gas supply system for supplying oxidant gas (air), and a cooling system including a cooling water pump, a cooling water flow path, etc.

[0011] The type of fuel cell is not particularly limited, but may be, for example, a polymer electrolyte fuel cell (PEFC). The use of the fuel cell is not particularly limited. For example, the fuel cell may be a mobile fuel cell mounted on a mobile body such as a vehicle or ship, or a stationary fuel cell used in a stationary power generation facility.

[0012] An outline of one example of an ejector 10 for a fuel cell disclosed in this specification is shown in FIG. 1, and another example of the ejector 10 is shown in FIG.

[0013] The ejector 10 includes a fuel gas inlet 12, an off-gas suction port 14, and a diffuser 20. In the ejector 10, the fuel gas inlet 12 and the off-gas suction port 14 are located upstream of the ejector 10, and the diffuser 20 is located downstream of the inlet 12 and the suction port 14.

[0014] The fuel gas inlet 12 is configured by a nozzle portion of a fuel gas injector (not shown), and is provided in a cavity in the upstream portion 10a of the ejector 10. The center line H of the inlet 12 along the axial direction of the nozzle coincides with the central axis of the diffuser 20.

[0015] Fuel gas supplied to the injector at a predetermined flow rate from a fuel gas tank (not shown) is injected as a driving gas into the inside of the ejector 10 from an inlet 12. By injecting the fuel gas into the ejector 10, off-gas is sucked into the ejector 10 from an inlet 14, mixed in the diffuser 20, and introduced into the fuel cell.

[0016] The off-gas suction port 14 is provided so that the off-gas can be sucked into the cavity of the upstream portion 10a by the fuel gas ejected into the ejector 10. The off-gas reaches the suction port 14 through a gas-liquid separator in an off-gas circulation system for reusing the off-gas discharged from a fuel cell (not shown). In FIG. 1, the suction port 14 is below the fuel gas inlet 12 and opens at the lowest part on the upstream side of the ejector 10. This allows the off-gas from below in the direction of gravity to be taken into the ejector 10.

[0017] The diffuser 20 is provided downstream of the inlet 12 and the suction port 14. The diffuser 20 is provided in its entirety in a substantially horizontal manner along the center line H of the fuel gas inlet 12. The diffuser 20 is a tubular body including an upstream section 22 located on the most upstream side, a midstream section 24 adjacent to the upstream section 22, and a downstream section 26 located on the most downstream side. The centers of the inner diameters of the upstream section 22, the midstream section 24, and the downstream section 26 are on the center line H.

[0018] The upstream section 22 is an introduction section for fuel gas and off-gas, and has a tapered shape with an inner diameter that decreases toward the downstream side. The midstream section 24 is designed to maintain the reduced inner diameter of the upstream section 22 for a predetermined length. Therefore, in the midstream section 24, the flow rate of the mixed gas increases, and even if water condenses, it is less likely to remain.

[0019] The downstream section 26 has a tapered shape in which the inner diameter of the midstream section 24 expands toward the discharge port 28. The most downstream part of the downstream section 26 forms the discharge port 28 for the mixed gas. The length of the downstream section 26 in the gas flow direction is longer than the upstream section 22 and the midstream section 24. The large internal space of the downstream section 26 prevents condensed water from impeding the gas flow.

[0020] 1, the inner surface 20a of the diffuser 20 is configured so that the upstream side is more hydrophilic than the downstream side. In other words, the downstream side is more water repellent than the upstream side. This makes it possible to prevent water from moving from the discharge port 28 toward the fuel cell even if water accumulates inside the diffuser 20. As a result, it is possible to prevent or avoid water from entering the fuel cell when the mixed gas is not being discharged.

[0021] The hydrophilicity or hydrophobicity of the surface 20a of the diffuser 20 may vary discontinuously or continuously. For example, one or more hydrophilic regions may be formed on the upstream side, one or more hydrophobic regions may be formed on the downstream side, or a combination of these may be used.

[0022] The formation of the hydrophilic and water-repellent regions can be achieved, for example, by surface treatment of the inner surface of the diffuser 20, or by the hydrophilic and water-repellent properties of the materials constituting each part of the diffuser 20. Those skilled in the art can appropriately select the surface treatment materials capable of forming such hydrophilic and / or water-repellent regions.

[0023] Further, for example, the diffuser 20 may have fine protrusions on the inner surface 20a thereof that promote the movement of water from downstream to upstream. Such fine protrusions are known, for example, from International Publication No. 2015 / 163365.

[0024] 1, for example, the suction port 14 is located below the diffuser 20, which promotes the movement of at least the water in the upstream section 22 and the midstream section 24 of the diffuser 20 upstream of the ejector 10. In addition, the water in the downstream section 26 also flows along the upper inner surface of the downstream section 26, which promotes the movement of the water upstream, and ultimately to the suction port 14.

[0025] The mechanism for promoting the movement of water from downstream to upstream when the mixed gas is not being discharged, as described above, is an example of the movement promotion mechanism disclosed in this specification.

[0026] According to the ejector 10 described above, when the mixed gas is not being discharged, the movement of water generated inside the diffuser 20 toward the upstream of the ejector 10 is promoted, and the intrusion of water into the fuel cell can be suppressed or avoided. This makes it possible to suppress or avoid malfunctions of the fuel cell caused by the intrusion of water. In addition, because of the movement promotion mechanism within the diffuser 20, the expansion of the diffuser 20 can be suppressed or avoided due to the promotion of movement. Furthermore, since the retention and freezing of water within the diffuser 20 can be prevented, deterioration of the mixed gas circulation, etc. can be suppressed or avoided.

[0027] The movement promotion mechanism is not limited to the above-described embodiment, and may take various forms. For example, the ejector 10 itself may be configured so that the suction port 14 and the discharge port 28 are located higher in the gravity direction than the suction port 14. For example, as shown in FIG. 2, the ejector 10 may be inclined so that the discharge port 28 is located higher in the weight direction than the suction port 14. In this way, the movement promotion mechanism using gravity can be easily realized. The angle at which the ejector 10 is inclined is not particularly limited, but the ejector 10 may be inclined from several degrees to less than 90 degrees, for example, 60 degrees or less, for example, 30 degrees or less, or for example, 20 degrees or less, so that the discharge port 28 is located higher in the weight direction. [Explanation of symbols]

[0028] 10 fuel cell, 12 fuel gas inlet, 14 off-gas suction port, 20 diffuser, 22 upstream portion, 24 midstream portion, 26 downstream portion, 28 discharge port

Claims

[Claim 1] An ejector for introducing a mixed gas of a fuel gas and an off-gas of the fuel cell into a fuel cell, the inlet for the fuel gas which is a driving gas, a suction port for off-gas of the fuel cell, and a diffuser which mixes the fuel gas and the off-gas of the fuel cell and has a discharge port for the mixed gas, an ejector comprising a movement promoting mechanism that promotes the movement of water in the diffuser from the discharge port toward the suction port when the mixed gas is not being discharged.

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