Fuel cell system

Abstract

This prevents water droplets from flowing back into the bypass piping. [Solution] The fuel cell system includes a connection section 40 connecting a bypass pipe and an exhaust pipe, which comprises a main body 42 having a main flow path 46 extending in a first direction in which the exhaust pipe extends, a joint section 44 extending radially outward from the side of the main body 42 toward the main flow path 46 toward which the bypass pipe is connected, a joint flow path 48 formed inside the joint section 44 and extending in a second direction perpendicular to the main flow path 46, and a plurality of flow straightening ribs 50 that protrude inward from the inner circumferential surface 44a of the joint section 44 forming the joint flow path 48 and extend for a long distance in the second direction.

Description

Technical Field

[0001] The present disclosure relates to a fuel cell system.

Background Art

[0002] In recent years, research and development on fuel cells that contribute to energy efficiency have been carried out in order to enable more people to access affordable, reliable, sustainable, and advanced energy.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the technology related to fuel cells, reliable operation in a low-temperature environment is required. For example, if moisture adheres to a valve included in a fuel cell system and freezes, the valve remains blocked, which hinders the operation of the fuel cell system. Therefore, measures such as arranging various valves at a position higher than the adjacent pipes have been taken (Japanese Patent No. 5140993). However, with respect to a bypass pipe that bypasses an oxidant gas, backflow of water droplets from an exhaust pipe of the oxidant gas easily occurs, and it is difficult to prevent the water droplets from reaching a bypass valve only by the height difference. Therefore, there is a problem that the bypass valve disposed in the bypass pipe may freeze.

[0005] The present application aims to achieve prevention of backflow of water droplets into a bypass pipe in order to solve the above problems. Consequently, it contributes to energy efficiency.

Means for Solving the Problems

[0006] An aspect of the present disclosure is a fuel cell system comprising: a supply pipe for supplying an oxidant gas to a fuel cell; an exhaust pipe for exhausting the oxidant gas from the fuel cell; a bypass pipe connected to the supply pipe and the exhaust pipe, which bypasses the oxidant gas to the fuel cell; and a connecting portion connecting the bypass pipe and the exhaust pipe, wherein the connecting portion comprises: a main body having a main flow path extending in a first direction in which the exhaust pipe extends; a joint portion extending radially outward from the side of the main body and to which the bypass pipe is connected; a joint flow path formed inside the joint portion and extending in a second direction perpendicular to the main flow path; and a plurality of flow-straightening ribs protruding inward from the inner circumferential surface of the joint portion forming the joint flow path and extending long in the second direction. [Effects of the Invention]

[0007] The fuel cell system of this disclosure can prevent water droplets from flowing back into the bypass piping and can prevent the bypass valve located in the bypass piping from freezing. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is an explanatory diagram of the oxidizer gas supply system of the fuel cell system according to the embodiment. [Figure 2] Figure 2 is an explanatory diagram of the piping layout around the humidifier shown in Figure 1. [Figure 3] Figure 3 is a perspective view of the connection point in Figure 2. [Figure 4] Figure 4 is a cross-sectional view along the line IV-IV in Figure 3. [Figure 5] Figure 5 is a cross-sectional view along the VV line in Figure 3. [Figure 6] Figure 6 is a cross-sectional view showing the arrangement of the flow-straightening ribs in the joint channel. Figure 6 follows the line VI-VI in Figure 3. [Figure 7] Figure 7 shows the results of a fluid simulation examination of the range of water droplet backflow into the bypass channel due to the connection points in the first to third design examples. [Modes for carrying out the invention]

[0009] As shown in Figure 1, the fuel cell system 10 of this embodiment includes a fuel cell 12 and an oxidant gas supply system 14. The fuel cell 12 is, for example, a polymer electrolyte fuel cell (PEFC), in which hydrogen is supplied as fuel gas to the anode side and air is supplied as oxidant gas to the cathode side. The oxidant gas supply system 14 supplies oxidant gas adjusted to a predetermined pressure and humidity to the fuel cell 12. The fuel cell system 10 can be used, for example, as a power source for mobile vehicles such as passenger cars, trucks, construction machinery, aircraft, and ships. The fuel cell system 10 can also be used as a stationary power supply system.

[0010] The oxidizer gas supply system 14 includes a supply channel 16, a compressor 18, a heat exchanger 20, a humidifier 22, an exhaust channel 24, and a bypass channel 26. The supply channel 16 is a channel that supplies oxidizer gas (air) to the inlet port 12a of the fuel cell 12. The compressor 18 is connected to the supply channel 16 and takes in air and compresses it.

[0011] The heat exchanger 20 is connected downstream of the compressor 18 in the supply channel 16. The heat exchanger 20 cools the air that has been compressed and heated by the compressor 18.

[0012] The humidifier 22 is connected to the supply channel 16 between the heat exchanger 20 and the introduction port 12a of the fuel cell 12. The humidifier 22 is also connected to the exhaust channel 24. The humidifier 22 humidifies the oxidizer gas supplied to the fuel cell 12 by transferring water vapor from the oxidizer off-gas flowing through the exhaust channel 24 to the oxidizer gas flowing through the supply channel 16.

[0013] The exhaust channel 24 is connected to the exhaust port 12b of the fuel cell 12 and is a channel for discharging oxidant off-gas (cathode off-gas) from the fuel cell 12. One end of the bypass channel 26 is connected to the supply channel 16 upstream of the humidifier 22, and the other end is connected to the exhaust channel 24 downstream of the humidifier 22. The bypass channel 26 allows the oxidant gas from the supply channel 16 to flow to the exhaust channel 24 without passing through the humidifier 22 and the fuel cell 12. The bypass channel 26 suppresses fluctuations in the operating state of the compressor 18 by releasing excess oxidant gas generated due to the difference between the response speed of the compressor 18 and the required amount of oxidant gas from the fuel cell 12.

[0014] A bypass valve 28 is provided in the bypass passage 26. The bypass valve 28 regulates the flow rate of the oxidizer gas flowing through the bypass passage 26. When the bypass valve 28 is opened, the oxidizer gas flows from the supply passage 16 to the exhaust passage 24 due to the pressure difference between the supply passage 16 and the exhaust passage 24.

[0015] The following describes the structure of the piping around the humidifier 22.

[0016] As shown in Figure 2, the humidifier 22 has a main body 22a that includes a membrane module. A supply pipe 30, which forms part of the upstream side (heat exchanger 20 side) of the supply channel 16, is connected to the first side 22b of the main body 22a. Oxidizing gas flows into the humidifier 22 through the supply pipe 30. In addition, a first pipe 32, which forms the downstream side of the supply channel 16 that goes from the humidifier 22 to the introduction port 12a of the fuel cell 12, is connected to the second side 22c of the main body 22a, which is opposite to the first side 22b.

[0017] Furthermore, a second pipe 34 is connected to the upper part of the main body 22a of the humidifier 22. The second pipe 34 is a pipe that guides the oxidizer off-gas from the exhaust port 12b of the fuel cell 12 to the humidifier 22, and constitutes the upstream side of the exhaust passage 24. An exhaust pipe 36 that discharges the oxidizer off-gas from the humidifier 22 is connected to the second side portion 22c near the lower end of the main body 22a. The exhaust pipe 36 constitutes part of the downstream side of the exhaust passage 24.

[0018] The bypass flow path 26 is constituted by a bypass pipe 38. The bypass pipe 38 branches from a supply pipe 30 near the humidifier 22, passes along the side of the main body 22a, and extends in a substantially first direction. The bypass pipe 38 bends toward the exhaust pipe 36 on the downstream side. The downstream side of the bypass pipe 38 is connected to a connection part 40. The connection part 40 is a connection member provided adjacent to the main body 22a and connects the bypass pipe 38 and the exhaust pipe 36. The bypass valve 28 is arranged near the supply pipe 30 away from the exhaust pipe 36 in order to prevent adhesion of water droplets.

[0019] As shown in FIGS. 3 to 6, the connection part 40 is formed in a T shape, and the internal flow path branches into three directions. The connection part 40 includes a main body part 42 and a joint part 44. The main body part 42 is a cylindrical part extending in the first direction. An upstream exhaust pipe 36 is connected to a first end part 42a thereof, and a downstream exhaust pipe 36 is connected to a second end part 42b thereof. A main flow path 46 is formed inside the main body part 42. The main flow path 46 is formed in a substantially straight line so as to allow an oxidant off-gas (oxidant gas to be exhausted) with a large flow rate to flow smoothly. The extending direction of a first center line A of the main flow path 46 extends along the first direction.

[0020] The joint part 44 extends obliquely upward and radially outward from a side part of the main body part 42. The joint part 44 is a part to which the bypass pipe 38 is connected. The joint part 44 is formed in a cylindrical shape, and a joint flow path 48 having a substantially circular cross section is formed inside thereof. The joint flow path 48 opens to a side part of the main flow path 46. The direction along a second center line B of the joint flow path 48 is called a second direction. The second center line B of the joint flow path 48 is orthogonal to the first center line A of the main flow path 46.

[0021] When viewed from the first direction, the joint flow path 48 is inclined upward so as to move away from the first center line A of the main flow path 46 (see FIG. 5). Such an upward slope reduces the backflow of water droplets into the bypass pipe 38.

[0022] Connection part 40 (Joint section 44) Furthermore, some of the oxidizer off-gas flowing through the main channel 46 flows into the bypass piping 38 in a swirling manner, and water droplets may be drawn in, causing them to backflow as far as the bypass valve 28, which is relatively far away. Inside the joint channel 48, the flow in the main channel 46 creates a swirling flow along the inner circumferential surface 44a of the joint 44, centered on the second centerline B of the joint 44. Since this swirling flow reaches relatively far from the connection 40 along the extending direction of the joint 44 and the bypass piping 38, it is considered to be a major factor in increasing the range of water droplet backflow. Therefore, backflow of water droplets into the bypass piping 38 cannot be sufficiently prevented by the slope of the joint channel 48 alone.

[0023] Therefore, in this embodiment, a plurality of flow-straightening ribs 50 are provided on the inner circumferential surface 44a of the joint portion 44 that forms the joint flow path 48. The flow-straightening ribs 50 protrude briefly from the inner circumferential surface 44a radially inward from the joint flow path 48 and extend for a longer distance in a second direction. The flow-straightening ribs 50 direct the gas flow along the inner circumferential surface 44a of the joint portion 44. hinder This hinders the growth of the swirling current.

[0024] The rectifying ribs 50 are arranged at equal intervals in the circumferential direction. For example, as shown in the figure, four rectifying ribs 50 may be provided at 90° intervals in the circumferential direction of the joint portion 44. However, the number of rectifying ribs 50 is not limited to four, but may be two to three or five or more.

[0025] The protruding height of the flow straightening rib 50 can be, for example, about 1 / 2 to 1 / 8 of the radius of the joint channel 48. More preferably, the protruding height is about 1 / 4 of the radius of the joint channel 48.

[0026] If the protruding height of the flow straightening rib 50 is too small, it will not be able to prevent the growth of a swirling flow along the inner circumferential surface 44a inside the joint channel 48.

[0027] Figure 6 shows a cross-section of the joint portion 44 cut along a plane perpendicular to the second direction. As shown in the figure, the arrangement of the flow straightening rib 50 can more effectively prevent backflow of water droplets into the bypass pipe 38 if it avoids the first direction portion 52 where the line C extending in the first direction, passing through the second center line B of the joint flow channel 48, intersects with the inner circumferential surface 44a. More preferably, the flow straightening rib 50 may be positioned at a circumferential offset of ±45° relative to the first direction portion 52.

[0028] The following describes the results of a fluid simulation study on the influence of the height and circumferential position of the flow-straightening rib 50 on the backflow range of water droplets, referring to Figure 7.

[0029] (1st design example) In this design example, the connection section 40 does not have a flow-straightening rib 50 on the inner circumferential surface 44a of the joint section 44. In the connection section 40 of the first design example, water droplets flowed back up to the first position 54 of the bypass piping 38.

[0030] (2nd design example) In this design example, the connection portion 40 is provided with four flow-straightening ribs 50 on the inner circumferential surface 44a of the joint portion 44. In this design example, the flow-straightening ribs 50 are positioned at a circumferential position ±45° away from the first direction portion 52. The protruding height of the flow-straightening ribs 50 in this design example is 1 / 2 of the radius of the joint portion 44. According to this design example, the growth of swirling flow is suppressed, and the backflow range is suppressed compared to the first position 54, which is the backflow range of water droplets in the first design example.

[0031] (3rd design example) In this design example, the connection section 40 is provided with four flow-straightening ribs 50 on the inner circumferential surface 44a of the joint section 44. In this design example, the flow-straightening ribs 50 are positioned at a circumferential position ±45° away from the first direction section 52. The protruding height of the flow-straightening ribs 50 in this design example is 1 / 4 of the radius of the joint section 44. According to this design example, the growth of swirling flow is suppressed more effectively, and the backflow range is suppressed even more than in the second design example.

[0032] With regard to the above embodiments, the following additional information is disclosed.

[0033] (Note 1) The fuel cell system (10) of the present disclosure comprises a supply pipe (30) for supplying an oxidant gas to a fuel cell (12), an exhaust pipe (36) for exhausting the oxidant gas from the fuel cell, a bypass pipe (38) connected to the supply pipe and the exhaust pipe and bypassing the oxidant gas to the fuel cell, and a connecting portion (40) connecting the bypass pipe and the exhaust pipe, wherein the connecting portion has a main body (42) having a main flow path (46) extending in a first direction in which the exhaust pipe extends, a joint portion (44) extending radially outward from the side of the main body and to which the bypass pipe is connected, a joint flow path (48) formed inside the joint portion and extending in a second direction perpendicular to the main flow path, and a plurality of flow straightening ribs (50) protruding inward from the inner circumferential surface (44a) of the joint portion forming the joint flow path and extending long in the second direction.

[0034] The fuel cell system described above can suppress the backflow of water droplets from the exhaust pipe to the bypass pipe and prevent the bypass valve from freezing.

[0035] (Note 2) The fuel cell system described in Appendix 1, wherein the plurality of flow-straightening ribs may be arranged at equal intervals in the circumferential direction of the joint flow path. This fuel cell system can suppress the growth of circumferential swirling flow within the joint flow path and prevent backflow of water droplets into the bypass piping.

[0036] (Note 3) The fuel cell system described in Appendix 2, wherein the arrangement positions of the plurality of flow straightening ribs may be offset from the first direction. This fuel cell system can suppress the growth of circumferential swirling flow inside the joint flow path and prevent backflow of water droplets into the bypass piping.

[0037] (Note 4) The fuel cell system described in Appendix 3, wherein the plurality of rectifying ribs may be provided at positions separated by ±45° with respect to the first direction. This fuel cell system can more effectively prevent backflow of water droplets into the bypass piping.

[0038] (Note 5) A fuel cell system according to any one of the appendices 1 to 4, wherein the second direction may be inclined upward as it moves away from the first centerline (A) of the main flow path. This fuel cell system can effectively prevent water droplets from flowing back into the bypass piping.

[0039] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of symbols]

[0040] 10…Fuel cell system 12…Fuel cell 22a...Main unit 30...Supply piping 36... Exhaust piping 38... Bypass piping 40...Connection part 42...Main body 44... Joint section 44a... Inner circumferential surface 46...Main channel 48...Joint channel 50... Flow straightening ribs

Claims

1. A supply pipe for supplying oxidant gas to the fuel cell, An exhaust pipe for exhausting the oxidizer gas from the fuel cell, A bypass pipe connected to the supply pipe and the exhaust pipe, which bypasses the oxidizer gas to the fuel cell, It includes a connecting part that connects the bypass piping and the exhaust piping, The aforementioned connection part is A main body having a main flow path extending in the first direction in which the exhaust piping extends, A joint portion extending radially outward from the side of the main body portion and to which the bypass piping is connected, A joint channel is formed inside the joint portion and extends in a second direction perpendicular to the main channel, It has a plurality of flow-straightening ribs that protrude inward from the inner circumferential surface of the joint portion forming the joint flow channel and that extend elongated in the second direction, A fuel cell system in which the flow-straightening rib is configured to suppress the growth of vortex flow caused by the fluid flowing in from the main channel by obstructing the circumferential flow along the inner surface of the joint portion.

2. A fuel cell system according to claim 1, wherein the plurality of rectifying ribs are arranged at equal intervals in the circumferential direction of the joint flow path.

3. A fuel cell system according to claim 2, wherein the arrangement positions of the plurality of rectifying ribs are provided in a direction offset from the first direction.

4. A fuel cell system according to claim 3, wherein the plurality of rectifying ribs are provided at positions separated by ±45° with respect to the first direction.

5. A fuel cell system according to any one of claims 1 to 4, wherein the second direction is inclined upward as it moves away from the first centerline of the main flow path.

Images