Fuel cell stack
Patent Information
- Application Number
- PCT/JP2025/011533
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-03-24
- Publication Date
- 2026-10-01
Smart Images
Figure JP2025011533_01102026_PF_FP_ABST
Abstract
Description
Fuel cell stack
[0001] The present invention relates to a fuel cell stack including a laminate of a plurality of power generation cells.
[0002] In recent years, technological development has been carried out on fuel cells that contribute to energy efficiency, in order to enable more people to secure access to affordable, reliable, sustainable and advanced energy. As a technology related to fuel cell stacks used in this type of fuel cell, there has been conventionally known a fuel cell stack in which a pipe is installed in a fuel gas discharge flow path, and water retained in the fuel gas discharge flow path is discharged through the pipe (see, for example, Patent Document 1).
[0003] Japanese Patent No. 6645765
[0004] However, under situations where the power generation state of the fuel cell varies, merely performing drainage through a pipe as in the fuel cell stack described in Patent Document 1 may be insufficient.
[0005] A fuel cell stack that is one embodiment of the present invention comprises: a cell laminate formed by laminating a plurality of power generation cells each having an electrolyte membrane in a predetermined direction; a plurality of gas flow paths provided along the plurality of power generation cells, through which reaction gas flows; an exhaust gas flow path provided penetrating through the cell laminate in the predetermined direction to discharge reaction gas that has passed through the plurality of gas flow paths; and a communication pipe disposed in the exhaust gas flow path and provided with a pair of openings respectively communicating with an upstream side and a downstream side of the exhaust gas flow path. The exhaust gas flow path has, in a cross-sectional shape thereof, a pair of adjacent sides each provided with a gas outlet through which the reaction gas that has passed through each of the plurality of gas flow paths flows out, and an opposing portion facing the pair of sides. The pair of sides intersect at a predetermined angle such that the reaction gas that has flowed into the exhaust gas flow path through the respective gas outlets of the pair of sides intersect on the opposing portion side relative to the central portion of the cross-sectional shape of the exhaust gas flow path.
[0006] According to the present invention, liquid water can be satisfactorily discharged through the exhaust gas flow path.
[0007] A perspective view schematically showing the overall configuration of a fuel cell stack according to an embodiment of the present invention. A cross-sectional view along line II-II in Figure 1. A perspective view schematically showing the configuration of an integrated electrode assembly incorporated into the fuel cell stack in Figure 1. A front view of a separator incorporated into the fuel cell stack in Figure 1. A cross-sectional view along line VV in Figure 4. A cross-sectional view showing the main components of the fuel cell stack along the oxidant gas discharge channel in Figure 1. An enlarged view of the main components of Figure 4 showing the detailed configuration around the through-hole for oxidant gas discharge. A diagram illustrating the flow of oxidant gas flowing into the through-hole in Figure 7. A diagram showing a reference example of Figure 8A.
[0008] Embodiments of the present invention will be described below with reference to Figures 1 to 8B. The fuel cell stack according to the embodiment of the present invention is the main component of the fuel cell and constitutes the body of the fuel cell. The fuel cell can be mounted on a vehicle, for example, and generate electricity for driving the vehicle. First, the overall configuration of the fuel cell stack will be described in general terms. Note that the fuel cell stack is sometimes simply referred to as a fuel cell.
[0009] Figure 1 is a schematic perspective view showing the overall configuration of the fuel cell stack 100 according to this embodiment. For convenience, the three mutually orthogonal axial directions shown in the figure will be defined as the longitudinal direction, the left-right direction, and the vertical direction, and the configuration of each part will be described according to this definition. The downward direction in the vertical direction corresponds to the direction of gravity or approximately the direction of gravity. The longitudinal direction corresponds to the stacking direction of the fuel cell stack 100. The longitudinal and left-right directions are not necessarily the same as the longitudinal and left-right directions of a vehicle.
[0010] As shown in Figure 1, the fuel cell stack 100 has a cell stack 101 formed by stacking multiple power generation cells 1 in the front-to-back direction, and end units 102 positioned at both ends of the cell stack 101 in the front-to-back direction, and the whole has a substantially rectangular parallelepiped shape. Although not shown in the figure, the cell stack 101 is covered by a substantially rectangular parallelepiped case. The length of the cell stack 101 in the left-to-right direction is longer than the length in the up-to-down direction. Therefore, the left-to-right direction is the long dimension, and the up-to-down direction is the short dimension. For convenience, a single power generation cell 1 is shown in Figure 1.
[0011] The power generation cell 1 includes a unitized electrode assembly 2 (hereinafter referred to as UEA) having a joint containing an electrolyte membrane and an electrode, and separators 3, 3 arranged on both sides of the UEA 2 in the front-rear direction and sandwiching the UEA 2. The UEA 2 and the separators 3 are arranged alternately in the front-rear direction. The UEA 2 can also be called a membrane electrode structure or membrane electrode member.
[0012] Figure 2 is a cross-sectional view of the main part of the power generation region in the center of the cell stack 101 in the left-right direction (a cross-sectional view along the line II-II in Figure 1). As shown in Figure 2, the separator 3 has a front plate 3F and a rear plate 3R, which are a pair of thin metal plates with a corrugated cross-section. The front plate 3F extends in the vertical, horizontal, and lateral directions and has a front surface 3Fa and a rear surface 3Fb. The rear plate 3R extends in the vertical, horizontal, and lateral directions and has a front surface 3Ra and a rear surface 3Rb. The rear surface 3Fb of the front plate 3F and the front surface 3Ra of the rear plate 3R, which face each other, are joined at their outer edges by welding or the like. This integrally connects the front plate 3F and the rear plate 3R. The separator 3 is made of a conductive material with excellent corrosion resistance, such as stainless steel, titanium, or titanium alloy.
[0013] A cooling channel PAw is formed inside the separator 3, which is enclosed by the front plate 3F and the rear plate 3R, specifically between the rear surface 3Fb of the front plate 3F and the front surface 3Ra of the rear plate 3R, through which a cooling medium flows. The flow of the cooling medium cools the power generation surface of the power generation cell 1. For example, water can be used as the cooling medium. The surfaces of the separator 3 facing the UEA 2 (front surface 3Fa and rear surface 3Rb) are formed to be uneven by press molding or the like so as to form a gas flow channel between them and the UEA 2. More specifically, the separator 3 has a pair of front and rear ribs 31 that protrude toward the UEA 2, and a pair of front and rear recesses 32 that are recessed and connected to the pair of front and rear ribs 31.
[0014] A pair of front and rear ribs 31 abut the rear surface 2b and front surface 2a of the UEA2. A compressive load F is applied to the cell stack 101 in the front-rear direction during the assembly of the fuel cell stack 100, and this compressive load F is maintained after the assembly of the fuel cell stack 100 is completed. Therefore, a predetermined surface pressure due to the compressive load F acts on the UEA2 in the front-rear direction via the ribs 31.
[0015] Between the front surface 2a of the UEA2 and the rear plate 3R of the separator 3 facing the front surface 2a, a recess 32 forms an anode channel PAa through which the fuel gas flows. Between the rear surface 2b of the UEA2 and the front plate 3F of the separator 3 facing the rear surface 2b, a recess 32 forms a cathode channel PAc through which the oxidizer gas flows. The fuel gas is a gas containing hydrogen, for example, hydrogen gas can be used. The oxidizer gas is a gas containing oxygen, for example, air can be used. The fuel gas and oxidizer gas are sometimes referred to collectively as reaction gases without distinction.
[0016] Figure 3 is a perspective view showing the schematic configuration of the UEA2. As shown in Figure 3, the UEA2 has a substantially rectangular membrane electrode assembly (MEA; hereinafter referred to as MEA) 20 and a frame 21 that supports the MEA20. The MEA20 has an electrolyte membrane, an anode electrode provided on the front surface of the electrolyte membrane, and a cathode electrode provided on the rear surface of the electrolyte membrane.
[0017] The electrolyte membrane is, for example, a solid polymer electrolyte membrane, and a thin film of a water-containing perfluorosulfonic acid polymer can be used. Not limited to fluorine-based electrolyte membranes, hydrocarbon-based electrolyte membranes can also be used. The anode electrode has an electrode catalyst layer formed on the front surface of the electrolyte membrane, which serves as the reaction field for the electrode reaction, and a gas diffusion layer provided on the front surface of the electrode catalyst layer, which diffuses and supplies the fuel gas. The cathode electrode has an electrode catalyst layer formed on the rear surface of the electrolyte membrane, which serves as the reaction field for the electrode reaction, and a gas diffusion layer provided on the rear surface of the electrode catalyst layer, which diffuses and supplies the oxidizing gas.
[0018] At the anode electrode, fuel gas (hydrogen) supplied via the anode channel PAa in Figure 2 is ionized by the action of a catalyst and moves to the cathode electrode side through the electrolyte membrane. The electrons generated at this time pass through an external circuit and are extracted as electrical energy. At the cathode electrode, oxidizing gas (oxygen) supplied via the cathode channel PAc in Figure 2 reacts with hydrogen ions introduced from the anode electrode and electrons that have moved from the anode electrode to produce water. The generated water (called generated water) provides appropriate humidity to the electrolyte membrane, and excess water is discharged to the outside of the integrated electrode assembly 2 along the gas flow.
[0019] As shown in Figure 3, the frame 21 is a substantially rectangular frame member and is made of a thin, plate-like film or sheet material such as resin or rubber that has insulating properties. A substantially rectangular opening 21a is provided in the center of the frame 21. The MEA 20 is provided so as to cover the entire opening 21a, and the peripheral edge of the MEA 20 is supported by the frame 21. The frame 21 can also be called a film or a sheet.
[0020] To the left of the opening 21a of the frame 21, three through holes 211 to 213 are opened vertically, penetrating the frame 21 in the front-to-back direction. To the right of the opening 21a, three through holes 214 to 216 are opened vertically, penetrating the frame 21 in the front-to-back direction. For convenience, the through holes 211 to 216 are shown as being approximately rectangular in shape, but the shape and arrangement of the through holes 211 to 216 are not limited to this.
[0021] As shown in Figure 1, through holes 301 to 306 are opened in the front and rear separators 3 of the UEA2 at positions corresponding to the through holes 211 to 216 of the frame 21, respectively, and the through holes 301 to 306 penetrate the separators 3 in the front-rear direction. The through holes 301 to 306 communicate with the through holes 211 to 216 of the frame 21, respectively. The collection of these mutually communicating through holes 211 to 216 and 301 to 306 forms flow paths PA1 to PA6 (indicated by arrows for convenience) that penetrate the cell stack 101 and extend in the front-rear direction. Flow paths PA1 to PA6 are sometimes called manifolds. Flow paths PA1 to PA6 are connected to a manifold outside the fuel cell stack 100.
[0022] Although not shown in the diagram, the front and rear end units 102 of the cell stack 101 each have multiple plates arranged in a stacked manner in the front-to-back direction. That is, the end unit 102 has a terminal plate arranged adjacent to the cell stack 101, an insulating plate arranged outside the terminal plate in the front-to-back direction, and an end plate arranged outside the insulating plate in the front-to-back direction.
[0023] The rear end unit 102 has multiple through holes 102a to 102f that penetrate the end unit 102 in the front-to-back direction, at positions corresponding to the through holes 211 to 216 and 301 to 306 of the cell laminate 101. For convenience, the through holes 102a to 102f are all shown as roughly rectangular in shape, but the position and shape of the through holes 102a to 102f are not limited to this.
[0024] The through-hole 102a is a fuel gas supply port, and fuel gas is supplied to the fuel cell stack 100 through the through-hole 102a. This fuel gas flows forward along the gas flow path PA1 through the through-holes 211 and 301 and is guided to the anode flow path PAa between the UEA2 and the rear plate 3R of the separator 3. After passing through the anode flow path PAa, the fuel gas flows backward along the gas flow path PA6 through the through-holes 216 and 306 and is discharged from the through-hole 102f.
[0025] The through-hole 102d is an oxidizer gas supply port, and oxidizer gas is supplied to the fuel cell stack 100 through the through-hole 102d. This oxidizer gas flows forward along the gas flow path PA4 through the through-holes 214 and 304 and is guided to the cathode flow path PAc between the UEA2 and the front plate 3F of the separator 3. After passing through the cathode flow path PAc, the oxidizer gas flows backward along the gas flow path PA3 through the through-holes 213 and 303 and is discharged from the through-hole 102c.
[0026] The through-hole 102e is a supply port for the cooling medium, and the cooling medium is supplied to the fuel cell stack 100 through the through-hole 102e. This cooling medium flows forward along the flow path PA5 through the through-holes 215 and 305 and is guided to the cooling flow path PAw between the front plate 3F and the rear plate 3R of the separator 3. After passing through the cooling flow path PAw, the cooling medium flows backward along the flow path PA2 through the through-holes 212 and 302 and is discharged from the through-hole 102b. The above is a schematic configuration of the fuel cell stack 100.
[0027] The configuration of separator 3 will be explained in more detail. Figure 4 is a front view (viewed from the front) of separator 3. That is, Figure 4 shows the front surface 3Fa (Figure 2) of separator 3 facing the cathode electrode on the rear surface 2b of UEA2, and is a view that is inverted horizontally compared to Figure 1.
[0028] In Figure 4, the region of UEA2 facing MEA20, i.e., region AR1 facing the power generation surface, is called the active region of separator 3, and the region AR2 outside the active region AR1 in the left-right direction is called the inactive region. As shown in Figures 2 and 4, in the active region AR1 of separator 3, although some parts are not shown, a plurality of ribs 31 (Figure 2) are provided projecting forward at equal intervals in the vertical direction over almost the entire area. Each of the plurality of ribs 31 extends in the left-right direction, and recesses 32 (Figure 2) are provided between adjacent ribs 31, 31 in the vertical direction. A cathode flow path PAc is formed between the plurality of recesses 32 and the rear surface 2c of MEA20.
[0029] As shown in Figure 4, the front surface 3Fa of the inactive region AR2 of the separator 3 (front plate 3F) is provided with a plurality of sealing bead portions, i.e., metal bead seals, that protrude forward toward the frame 21. The plurality of bead portions include an outer bead portion 331 and a plurality of individual bead portions 332.
[0030] Multiple individual bead portions 332 each individually surround multiple through holes 301 to 306. The outer bead portion 331 extends horizontally along the upper and lower edges of the separator 3 above and below the active region AR1, and also extends in a zigzag pattern via the left and right outer edges of the individual bead portions 332 around the through holes 301, 303, 304, and 306, and via the left and right inner edges of the individual bead portions 332 around the through holes 302 and 305.
[0031] In the inactive region AR2 of the separator 3 (front plate 3F), a guide portion 333 is provided projecting forward from the through hole 304 to the entire inlet at the right end of the cathode flow path PAc, and from the entire outlet at the left end of the cathode flow path PAc to the through hole 303. Between the through hole 304 and the guide portion 333, a plurality of tunnel portions 41 are provided that cross the individual bead portions 332. Between the through hole 303 and the guide portion 333, a plurality of tunnel portions 42 are provided that cross the individual bead portions 332.
[0032] Figure 5 is a cross-sectional view showing the configuration of tunnel sections 41 and 42 (a cross-sectional view along the line V-V in Figure 4). As shown in Figure 5, tunnel sections 41 and 42 are provided on the front plate 3F in a convex shape toward the front, and tunnel sections 41 and 42 are provided on the rear plate 3R in a convex shape toward the rear. The amount of projection of tunnel sections 41 and 42 in the front-rear direction is smaller than the amount of projection of individual bead sections 332 in the front-rear direction. Although not shown in the figure, tunnel sections 41 and 42 have a roughly rectangular or roughly trapezoidal cross-section. A communication channel PA 11 is formed between the front and rear tunnel sections 41 and 41, and a communication channel PA 12 is formed between the front and rear tunnel sections 42 and 42. A sealing material 334 made of resin or rubber is attached to the front and rear ends of the individual bead sections 332, and the space between the separator and the UEA 2 (frame 21) is sealed via the sealing material 334.
[0033] An inlet 410a for oxidizing gas is provided at the right end of the tunnel section 41. The through hole 304 communicates with the communication channel PA 11 via the inlet 410a. The tunnel section 41 intersects with the individual bead section 332 and extends to the left beyond the individual bead section 332. A tapered section 411 is provided at the left end of the tunnel section 41, with the amount of protrusion gradually decreasing. At the left end of the tunnel section 41, the amount of protrusion in the front-rear direction becomes zero, and the communication channel PA 11 is closed. An outlet 410b for oxidizing gas is opened at the front tapered section 411.
[0034] As a result, the through-hole 304 and the cathode channel PAc in front of the front plate 3F are connected via the inlet 410a, the communication channel PA11, and the outlet 410b. Consequently, the oxidizing gas flowing through the through-hole 304 can be guided to the cathode channel PAc via the communication channel PA11, as shown by the arrow in Figure 5.
[0035] An oxidizing gas outlet 420b is provided at the left end of the tunnel section 42. The through hole 303 communicates with the communication channel PA 12 via the outlet 420b. The tunnel section 42 intersects with the individual bead section 332 and extends to the right beyond the individual bead section 332. A tapered section 421 is provided at the right end of the tunnel section 42, with the amount of protrusion gradually decreasing. At the right end of the tunnel section 41, the amount of protrusion in the front-rear direction becomes zero, and the communication channel PA 12 is closed. An oxidizing gas inlet 420a is opened in the front tapered section 421.
[0036] As a result, the through-hole 303 and the cathode channel PAc in front of the front plate 3F are connected via the inlet 420a, the communication channel PA12, and the outlet 420b. Consequently, the oxidizing gas flowing through the cathode channel PAc can be guided to the through-hole 304 via the communication channel PA12, as shown by the arrow in Figure 5. In Figure 5, for convenience, the tunnel sections 41 and 42 are shown to extend in the left-right direction, but the direction in which the tunnel sections 41 and 42 extend is not limited to the left-right direction, as will be described later (see Figure 7).
[0037] Although not shown in the illustration, the tunnel sections 43 and 44 in Figure 4 are configured in the same way as in Figure 5. Specifically, the front plate 3F and the rear plate 3R are projected forward and backward respectively to form a pair of front and rear tunnel sections 43, 43, and a fuel gas outlet is opened in the rear tapered section near the right end of tunnel section 43. Similarly, the front plate 3F and the rear plate 3R are projected forward and backward respectively to form a pair of front and rear tunnel sections 44, 44, and a fuel gas inlet is opened in the rear tapered section near the left end of tunnel section 44. This allows the fuel gas flowing through the through-hole 301 to be guided to the anode channel PAa via the flow path in tunnel section 43, and the fuel gas flowing through the anode channel PAa to be guided to the through-hole 306 via the flow path in tunnel section 44.
[0038] The gas flow paths PA3 and PA6 in Figure 1 are the oxidizer gas discharge path PA3 and the fuel gas discharge path PA6, respectively, and are sometimes referred to as reaction exhaust gas flow paths. The configurations of the oxidizer gas discharge path PA3 and the fuel gas discharge path PA6 are substantially identical. Therefore, the configuration of the reaction exhaust gas flow path will be explained below, focusing on the oxidizer gas discharge path PA3. Figure 6 is a cross-sectional view showing the main components of the fuel cell stack 100 along the oxidizer gas discharge path PA3.
[0039] In Figure 6, the individual illustrations of the power generation cell 1 are omitted. Also, in Figure 6, in order to distinguish the configurations of the front and rear end units 102, the front end unit 102 is represented by a terminal plate 51, an insulating plate 52, and an end plate 53, while the rear end unit 102 is represented by a terminal plate 54, an insulating plate 55, and an end plate 56.
[0040] As shown in Figure 6, the oxidizer gas discharge channel PA3 extends in the front-rear direction through the through-hole 102c of the rear end unit 102, the through-holes 213 and 303 of the cell stack 101, and the through-hole 102c of the front end unit 102. Therefore, the end unit 102 and the cell stack 101 form the oxidizer gas discharge channel PA3 and constitute the channel forming section. The through-hole 102c of the front end unit 102 includes the through-hole 51c of the terminal plate 51 and the through-hole 52c of the insulating plate 52. The front end of the oxidizer gas discharge channel PA3 is closed by the end plate 53. The through-hole 102c of the rear end unit 102 includes the through-hole 54c of the terminal plate 54, the through-hole 55c of the insulating plate 55, and the through-hole 56c of the end plate 56.
[0041] A connecting pipe 7 is installed along the bottom surface of the oxidizer gas discharge channel PA3. The connecting pipe 7 is an elongated pipe member with a substantially cylindrical cross-section, having openings (front end opening 71a, rear end opening 72a) at its front end surface 71 and rear end surface 72, respectively, and extends linearly in the front-rear direction through the cell laminate 101. The front end opening 71a of the connecting pipe 7 is located inside the internal space SP1 of the through hole 102c of the front end unit 102, more specifically, inside the through hole 52c of the insulating plate 52. The rear end opening 72a of the connecting pipe 7 is located inside the internal space SP2 of the through hole 102c of the rear end unit 102, more specifically, inside the through hole 55c of the insulating plate 55. Therefore, the internal space SP1 of the front end unit 102 and the internal space SP2 of the rear end unit 102 are in communication via the connecting pipe 7.
[0042] The connecting pipe 7 is formed from materials such as resin, rubber, or glass. However, considering that vibrations and temperature changes occur in the fuel cell stack 100, it is preferable that the connecting pipe 7 be made of flexible resin or rubber. Water flows through the connecting pipe 7 from the front end opening 71a to the rear end opening 72a in accordance with the pressure difference between the internal spaces SP1 and SP2 of the front and rear end units 102, 102. For this reason, the cross-sectional area of the connecting pipe 7 is set to be sufficiently smaller than the cross-sectional area of the fuel gas discharge passage PA6, but to allow for a flow of more than a predetermined amount of water.
[0043] A front end portion of the communication pipe 7 is supported by a front support portion 201 provided on the front end unit 102.
[0044] The front support portion 201 bulges upward in a tunnel shape from the bottom surface of the through hole 52c of the insulating plate 52. A through hole 201a that penetrates the front support portion 201 in the front-rear direction is opened in the front support portion 201, and the front end portion of the communication pipe 7 is inserted into the through hole 201a. Although not shown in the drawings, the peripheral surface of the through hole 201a is formed in a tapered shape such that the cross-sectional area gradually decreases toward the front, thereby regulating the axial position of the front end portion of the communication pipe 7.
[0045] A rear end portion of the communication pipe 7 is supported by a rear support portion 202 provided on the rear end unit 102. The rear support portion 202 bulges upward in a tunnel shape from the bottom surface of the through hole 55c of the insulating plate 55. A through hole 202a that penetrates the rear support portion 202 in the front-rear direction is opened in the rear support portion 202, and the rear end portion of the communication pipe 7 is inserted into the through hole 202a. A stepped portion is provided on the peripheral surface of the through hole 202a. A rear end face 72 of the communication pipe 7 abuts against the stepped portion, thereby regulating the axial position of the rear end portion of the communication pipe 7.
[0046] Although not shown in the drawings, the communication pipe 7 is not only supported by the front and rear end units 102, but also supported by the frame 21 of the UEA 2. That is, a support portion through which the communication pipe 7 penetrates or engages is formed on the peripheral edge of the through hole 216 of the frame 21, and the communication pipe 7 is supported via the support portion. The support portion does not need to be provided on all the frames 21 in the front-rear direction, and may be provided on any arbitrary frame 21.
[0047] This embodiment is characterized by the configuration of the oxidant gas discharge flow path PA3 and the fuel gas discharge flow path PA6 as reactive exhaust gas flow paths, particularly in the cross-sectional shape thereof. The cross-sectional shape of the reactive exhaust gas flow path is represented by the through-holes 303 and 306 of the separator 3. FIG. 7 is an enlarged view of a main part of FIG. 4 showing the detailed configuration of the separator 3 around the through-hole 303. As shown in FIG. 7, the through-hole 303 has a substantially square shape. More specifically, the cross-section of the through-hole 303 is generally constituted by four sides: an upper side S1, a right side S2, a bottom side S3, and a left side S4. The upper side and the right side intersect at a predetermined angle θ larger than 90 degrees.
[0048] The upper side S1 extends obliquely upward to the left from a corner C1 where the upper side S1 and the right side S2 intersect. The bottom side S3 extends obliquely upward to the left from a corner C2 where the bottom side S3 and the right side S2 intersect. Accordingly, the upper side S1 and the bottom side S3 are parallel or substantially parallel. The right side S2 extends obliquely rightward from the corner C1 to the lower corner C2. The left side S4 extends obliquely rightward from a corner C3 where the left side S4 and the upper side S1 intersect to a corner C4 where the left side S4 and the bottom side S3 intersect. Accordingly, the right side S2 and the left side S4 are parallel or substantially parallel.
[0049] Thereby, the entire through-hole 303 has a parallelogram shape or a substantially parallelogram shape. The lengths of the respective sides S1 to S4 of the through-hole 303 are the same or substantially the same. Accordingly, the through-hole 303 is strictly a rhombus or substantially a rhombus. Among the corners C1 to C4, the corner C2 is located at the lowermost part of the through-hole 303, and the corner C3 facing the corner C2 is located at the uppermost part of the through-hole 303.
[0050] On the upper side S1, multiple tunnel sections 42 outlets 420b (Figure 5) are connected at equal intervals over almost the entire upper side S1. The multiple tunnel sections 42 on the upper side S1 are arranged parallel to each other and extend diagonally in a direction perpendicular to the upper side S1, that is, upward and to the right from the upper side S1. On the right side S2, multiple tunnel sections 42 outlets 420b are connected at equal intervals over almost the entire right side S2. The multiple tunnel sections 42 on the right side S2 are arranged parallel to each other and extend diagonally in a direction perpendicular to the right side S2, that is, to the right and upward from the right side S2. The connecting pipe 7 is positioned near the lower end corner C2, more specifically slightly to the left of corner C2, away from the tunnel sections 42 on the right side S2.
[0051] Oxidizing gas flows through the through-hole 303 from two directions, via tunnel sections 42 connected to the upper side S1 and tunnel sections 42 connected to the right side S2. Figure 7 shows a reference line L1 that passes through the middle of the multiple tunnel sections 42 on the upper side S1 and extends approximately parallel to the direction in which these tunnel sections 42 extend (approximately perpendicular to the upper side S1), and a reference line L2 that passes through the middle of the multiple tunnel sections 42 on the right side S2 and extends approximately parallel to the direction in which these tunnel sections 42 extend (approximately perpendicular to the right side S2). Reference line L1 can represent the flow of oxidizing gas passing through the upper side S1, and reference line L2 can represent the flow of oxidizing gas passing through the right side S2.
[0052] Compared to the center point P0 located at the center of the through-hole 303, the intersection point P1 of the reference lines L1 and L2 is to the left and below the center point P0, and is located on the corner side C4. The intersection point P1 indicates the point where the oxidizing gas that flowed into the through-hole 303 via the tunnel section 42 on the upper side S1 and the oxidizing gas that flowed into the through-hole 303 via the tunnel section 42 on the right side S2 converge.
[0053] Figure 8A illustrates the flow of oxidizing gas into the through-hole 303. As shown in Figure 8A, the oxidizing gas flowing in via the upper edge S1 (arrow A1) and the oxidizing gas flowing in via the right edge S2 (arrow A2) merge beyond the center point P0 in the region AR10 shown by the dotted line on the corner C4 side. Region AR10 is shown as a circular region centered on the center point P2. The center point P2 coincides, for example, with the intersection point P1 of the reference lines L1 and L2 in Figure 7. The center point P2 only needs to be located near the intersection point P1, at least more so than the center point P0, and does not need to coincide with the intersection point P1.
[0054] The operation of the fuel cell stack 100 according to this embodiment can be summarized as follows: During low-load power generation, when the flow rate of oxidant gas is low, the flow rate of oxidant gas flowing into the through-hole 303 is low and the flow velocity is low. For this reason, it is difficult to discharge the liquid water accumulated in the oxidant gas discharge channel PA3 with the flow of oxidant gas, and the liquid water is mainly discharged through the connecting pipe 7. That is, in this case, the liquid water W in the oxidant gas discharge channel PA3 flows downward along the bottom surface (bottom S3) of the oxidant gas discharge channel PA3, as shown by arrow A3 in Figure 8A.
[0055] As a result, the liquid water W flows toward the lowest connecting pipe 7, making it easy for the liquid water W to flow into the front end opening 71a of the connecting pipe 7. The liquid water that flows into the connecting pipe 7 through the front end opening 71a flows forward inside the connecting pipe 7 due to the pressure difference between the front and rear of the connecting pipe 7, and the liquid water W is discharged to the outside through the rear end opening 72a. As a result, the liquid water accumulated in the oxidizer gas discharge channel PA3 during low-load operation can be effectively discharged.
[0056] On the other hand, during high-load power generation with a large flow rate of oxidant gas, the amount of water generated by power generation increases, and the amount of liquid water W in the oxidant gas discharge channel PA3 also increases. Therefore, it is difficult to smoothly discharge the liquid water W through the small-diameter connecting pipe 7. In this embodiment, however, the oxidant gas that flows into the oxidant gas discharge channel PA3 from two directions through the upper side S1 and right side S2 of the through-hole 303, which intersect at an obtuse angle, merges in region AR10 near the corner C4. As a result, the oxidant gas concentrates in region AR10, pushing it backward and increasing the flow velocity of the oxidant gas in region AR10. This allows the liquid water W to be discharged effectively by the flow of the oxidant gas.
[0057] In particular, region AR10 is located downstream of the center point P0 of the through-hole 303 in the flow direction of the oxidizer gas through the tunnel section 42 (arrows A1, A2). Therefore, the oxidizer gases flowing into the oxidizer gas discharge channel PA3 from two directions merge near the corner C4 without turbulence, maintaining the momentum of the gas flow. As a result, the flow velocity of the oxidizer gas after the merger increases, and the liquid water W in the oxidizer gas discharge channel PA3 can be efficiently discharged without going through the connecting pipe 7.
[0058] Figure 8B is a reference example of Figure 8A. In Figure 8B, the through-hole 303 is approximately pentagonal or hexagonal in shape, and the area of the through-hole 303 is larger than that of Figure 8A. In the reference example, the oxidizing gas (arrows A1, A2) flowing in from two directions via the upper side S1 and the right side S2 merges not near the sides opposite to the upper side S1 and the right side S2, but in a region AR10 in front of those sides, that is, in a region AR10 near the center point P0 of the through-hole 303. This region AR10 is not a region enclosed by two sides (bottom side S3, left side S4) as in this embodiment (Figure 8A). For this reason, the flow of the oxidizing gas cannot be concentrated in region AR10.
[0059] Therefore, within the through-hole 303, the area with the highest velocity of the oxidizer gas does not concentrate in one place, but rather the velocity distribution becomes uneven. As a result, during high-load power generation, the flow of the oxidizer gas cannot smoothly discharge the liquid water in the oxidizer gas discharge channel PA3. Also, in Figure 8B, the bottom S3 of the through-hole 303 is approximately horizontal. Therefore, liquid water W tends to accumulate in the bottom region AR11 of the oxidizer gas discharge channel PA3, making it difficult to drain the liquid water W through the connecting pipe 7 during low-load power generation.
[0060] According to this embodiment, the following effects can be achieved. (1) The fuel cell stack 100 comprises a cell stack 101 formed by stacking a plurality of power generation cells 1 having an electrolyte membrane in the front-to-back direction (a predetermined direction), a plurality of gas channels through which reaction gas flows provided along the plurality of power generation cells 1, namely anode channel PAa and cathode channel PAc, an exhaust gas channel (for example, an oxidizer gas exhaust channel PA3) provided to penetrate the cell stack 101 in the front-to-back direction to discharge the reaction gas that has passed through the plurality of gas channels, and a connecting pipe 7 arranged in the oxidizer gas exhaust channel PA3, with a front end opening 71a and a rear end opening 72a that communicate with the upstream and downstream sides of the oxidizer gas exhaust channel PA3, respectively (Figures 1, 2, 6). The oxidant gas discharge channel PA3 has a cross-sectional shape that includes a pair of adjacent sides, namely the upper side S1 and the right side S2, each provided with an outlet 420b through which the oxidant gas that has passed through multiple cathode channels PAc flows out, and a bottom side S3 and a left side S4 that are opposite to the upper side S1 and the right side S2 (Figure 7). The upper side S1 and the right side S2 intersect at a predetermined angle θ such that the oxidant gas that flows into the oxidant gas discharge channel PA3 (through hole 303) via the respective outlets 420b of the upper side S1 and the right side S2 intersect at a predetermined angle θ in the region AR10 on the bottom side S3 side and the left side S4 side of the center point P0, which is the center of the cross-sectional shape of the oxidant gas discharge channel PA3 (Figure 7).
[0061] Since the connecting pipe 7 is positioned within the oxidizer gas discharge channel PA3 in this manner, during low-load operation when the flow rate of oxidizer gas through the oxidizer gas discharge channel PA3 is low, the liquid water accumulated in the oxidizer gas discharge channel PA3 can be effectively discharged through the connecting pipe 7. Furthermore, because the upper side S1 and the right side S2 of the through hole 303 intersect at a predetermined angle θ, the oxidizer gas flowing in through the upper side S1 and the right side S2 converge beyond the center point P0 of the through hole 303. Therefore, during high-load operation when the flow rate of oxidizer gas through the oxidizer gas discharge channel PA3 is high, the flow velocity of the oxidizer gas can be increased, and the liquid water in the oxidizer gas discharge channel PA3 can be effectively discharged by the flow of the oxidizer gas. For this reason, even under different operating conditions such as low-load operation and high-load operation, the liquid water can be effectively discharged through the oxidizer gas discharge channel PA3.
[0062] (2) The upper side S1 and the right side S2 intersect at a predetermined obtuse angle (Figure 7). This allows the oxidizing gas flowing in from two directions to merge into a single region AR10 enclosed by the two sides (bottom side S3 and left side S4), thereby increasing the flow velocity of the oxidizing gas after the merge.
[0063] (3) The oxidizer gas discharge channel PA3 has a substantially rectangular cross-section, and its cross-sectional shape includes the upper side S1 and the right side S2, and the bottom side S3 and the left side S4 (Figure 7). This makes it possible to reduce the cross-sectional area of the through hole 303, suppressing variations in the flow velocity of the oxidizer gas and making it easy to increase the flow velocity.
[0064] (4) The oxidizer gas discharge channel PA3 has a roughly rhombic cross-sectional shape (Figure 7). This allows the region AR10 where the oxidizer gas flowing in via two sides (top side S1, right side S2) merge to be set near the corner C4 opposite the two sides, and the flow velocity of the oxidizer gas flowing through the oxidizer gas discharge channel PA3 can be efficiently increased.
[0065] (5) The oxidizer gas discharge channel PA3 has a roughly square cross-section and includes a corner C2 located at the bottom and a corner C3 opposite to corner C2 in its cross-sectional shape (Figure 7). The upper side S1 and the right side S2 are provided between corner C2 and corner C3, and the connecting pipe 7 is positioned near corner C2 (Figure 7). This allows the liquid water in the oxidizer gas discharge channel PA3 to flow easily into the connecting pipe 7. Furthermore, since the connecting pipe 7 is not positioned in the region AR10 where the oxidizer gases merge, there is less turbulence in the gas flow when the oxidizer gases merge.
[0066] (6) The connecting pipe 7 is positioned at the bottom of the oxidizer gas discharge channel PA3 (Figure 7). This allows the liquid water flowing downward along the oxidizer gas discharge channel PA3 to be easily guided to the connecting pipe 7.
[0067] The above embodiment can be modified into various forms. Several modifications will be described below. In the above embodiment, a recess 32 is provided in a plurality of separators 3 to form a plurality of anode passages PAa and a plurality of cathode passages PAc as a plurality of gas passages, but the configuration of the plurality of gas passages is not limited to that described above. In the above embodiment, a connecting pipe 7 having a front end opening 71a and a rear end opening 71b as a pair of openings is provided in the oxidizer gas discharge passage PA3 and the fuel gas discharge passage PA6 (exhaust gas passage), but the exhaust gas passage in which the connecting pipe 7 is provided may be either the oxidizer gas discharge passage PA3 or the fuel gas discharge passage PA6 (for example, the oxidizer gas discharge passage PA3). Therefore, an exhaust gas passage whose cross-sectional shape includes a pair of adjacent sides, each provided with a gas outlet through which the reaction gas that has passed through each of the plurality of gas passages flows out, and a facing portion opposite to the pair of sides, may also be either the oxidizer gas discharge passage PA3 or the fuel gas discharge passage PA6 (for example, the oxidizer gas discharge passage PA3).
[0068] In the above embodiment, the oxidizer gas flows out into the oxidizer gas discharge channel PA3 via the outlet 420b at the exit of the tunnel section 42, but the configuration of the gas outlet is not limited to that described above. In the above embodiment, the reaction gas outlets 420b are provided on the upper side S1 and the right side S2 of the through hole 303, but the pair of adjacent sides on which the gas outlets are provided are not limited to those described above. That is, the pair of sides can be any as long as the reaction gas flowing into the exhaust gas channel through the gas outlets on each side intersects at a predetermined angle θ such that it intersects on the opposite side of the central part (center point P0) of the cross-sectional shape of the exhaust gas channel. In the above embodiment, the pair of sides consisting of the bottom side S3 and the left side S4 (the second pair of sides) is the opposing part opposite the pair of sides consisting of the top side S1 and the right side S2 (the first pair of sides), but the opposing part may be a corner instead of a side.
[0069] In the above embodiment, the upper side S1 and the lower side S3 intersect at a predetermined obtuse angle (predetermined angle θ), but the predetermined angle θ is not obtuse; for example, it may be a right angle. In the above embodiment, the cross-sectional shape of the through hole 303 constituting the exhaust gas passage was a substantially parallelogram shape, more specifically a substantially rhombic shape, but the cross-sectional shape of the exhaust gas passage is not limited to that described above. In the above embodiment, a pair of sides, the upper side S1 and the right side S2, are formed between the corner C2 (first corner) located at the bottom of the through hole 303 and the corner C3 (second corner) opposite to the corner C2, but the exhaust gas passage may have a substantially polygonal cross-section other than a quadrilateral shape. In the above embodiment, the connecting pipe 7 is placed near the corner C2, but the connecting pipe may be placed at other locations as long as it is located at the bottom of the exhaust gas passage.
[0070] In the above embodiment, an example of applying the fuel cell stack 100 to a vehicle was described, but the fuel cell stack having the power generation cell of the present invention can also be applied to mobile bodies other than vehicles such as aircraft and ships, robots, and various industrial machines.
[0071] The above description is merely an example, and the present invention is not limited by the embodiments and modifications described above, as long as the features of the present invention are not impaired. It is also possible to arbitrarily combine one or more of the above embodiments and modifications, and to combine modifications with each other.
[0072] 1 Power generation cell, 7 Connecting pipes, 71a Front end opening, 72a Rear end opening, 100 Fuel cell stack, 101 Cell stack, 420b Outlet, PAa Anode channel, PAc Cathode channel, PA3 Oxidizer gas discharge channel, PA6 Fuel gas discharge channel, S1 Top edge, S2 Right edge, S3 Bottom edge, S4 Left edge, C2, C4 Corners, P Center point
Claims
1. A fuel cell stack comprising: a cell stack formed by stacking a plurality of power generation cells having an electrolyte membrane in a predetermined direction; a plurality of gas channels provided along the plurality of power generation cells through which a reaction gas flows; an exhaust gas channel provided through the cell stack in the predetermined direction to discharge the reaction gas that has passed through the plurality of gas channels; and a communication pipe arranged in the exhaust gas channel and provided with a pair of openings that communicate with the upstream and downstream sides of the exhaust gas channel, wherein the exhaust gas channel has a cross-sectional shape that includes a pair of adjacent sides, each provided with a gas outlet through which the reaction gas that has passed through each of the plurality of gas channels flows out, and a facing portion opposite the pair of sides, and the pair of sides intersect at a predetermined angle such that the reaction gas that flows into the exhaust gas channel through the gas outlets of each of the pair of sides intersects the exhaust gas channel on the facing portion side rather than the central part of the cross-sectional shape of the exhaust gas channel.
2. A fuel cell stack according to claim 1, characterized in that the pair of sides intersect at a predetermined obtuse angle.
3. A fuel cell stack according to claim 1, wherein the exhaust gas flow path has a substantially polygonal cross-sectional shape, and the cross-sectional shape includes a first pair of sides constituting the pair of sides and a second pair of sides constituting the opposing portion.
4. A fuel cell stack according to claim 3, characterized in that the exhaust gas flow path has a substantially rhomboid cross-sectional shape.
5. A fuel cell stack according to claim 3, wherein the exhaust gas passage has a substantially rectangular cross-section and includes a first corner located at the bottom and a second corner opposite the first corner in the cross-sectional shape, the first pair of sides are provided between the first corner and the second corner, and the connecting pipe is arranged near the first corner.
6. A fuel cell stack according to any one of claims 1 to 4, characterized in that the connecting pipe is located at the bottom of the exhaust gas flow path.