JP6407069B2 - Fuel cell stack - Google Patents

Description

  The technology disclosed by the present specification relates to a fuel cell stack.

  A solid oxide fuel cell (hereinafter also referred to as “SOFC”) is generally used in the form of a fuel cell stack including a plurality of power generation units arranged in a predetermined direction (hereinafter also referred to as “array direction”). Is done. The power generation unit is a minimum unit of power generation, and includes a single cell including an electrolyte layer and an air electrode and a fuel electrode facing each other in the arrangement direction with the electrolyte layer interposed therebetween.

  The fuel cell stack is fastened by a plurality of bolts. The fuel cell stack has a plurality of gas flow paths (also referred to as “manifolds”) extending over a plurality of power generation units. Specifically, the fuel cell stack includes a gas flow path for supplying fuel gas, a gas flow path for discharging fuel gas, a gas flow path for supplying oxidant gas, and a gas flow path for discharging oxidant gas. Has been.

  Here, paying attention to the configuration on the fuel electrode side in each power generation unit, each power generation unit includes a frame member in which a first through-hole forming a fuel chamber facing the fuel electrode is formed. Further, the frame member includes a second through hole that constitutes a part of the above-described fuel gas supply gas flow path, and a communication flow path that connects the fuel chamber and the fuel gas supply gas flow path. Is formed. The fuel gas is supplied from the gas flow path for supplying fuel gas to the fuel chamber through the communication flow path formed by the frame member of each power generation unit, and is used for power generation in each power generation unit (for example, Patent Document 1). reference).

JP 2014-149931 A

  During rated operation of the fuel cell stack, the temperature of each power generation unit rises, and the frame member included in each power generation unit expands thermally. Since the fuel cell stack is fastened with a plurality of bolts, the expansion of the frame member in the outer peripheral direction of the fuel cell stack is restricted. Therefore, the frame member thermally expands inward so that the first through hole and the communication channel formed in the frame member are reduced. When the first through hole formed in the frame member is reduced and the position of the outer periphery of the fuel chamber is moved away from the fuel gas supply gas flow path, the length of the communication flow path along the gas flow direction becomes longer. Further, when the communication flow path formed in the frame member is reduced, the cross-sectional area of the cross section perpendicular to the gas flow direction of the communication flow path is reduced. When the length of the communication channel is increased or the cross-sectional area is decreased, the pressure loss of the communication channel is increased.

  The temperature of each power generation unit during rated operation of the fuel cell stack can be different from each other. For example, a power generation unit located near the center in the arrangement direction of the fuel cell stack tends to have a higher temperature during rated operation than a power generation unit located near both ends in the arrangement direction of the fuel cell stack. When a temperature difference occurs between the power generation units during rated operation of the fuel cell stack, a difference occurs in the amount of thermal expansion of the frame member between the power generation units, and a difference occurs in the cross-sectional area and length of the communication flow path. When there is a difference in the cross-sectional area or length of the communication channel between the power generation units, a difference occurs in the pressure loss of the communication channel, resulting in a difference in the flow rate of the fuel gas supplied to the fuel chamber of each power generation unit. As a result, the power generation performance of the fuel cell stack may be reduced.

  The problem that the pressure loss of the communication flow path of each power generation unit during rated operation is not limited to the communication flow path on the fuel gas supply side, but is also common to the communication flow path on the oxidant gas supply side. is there. Moreover, such a problem is not limited to SOFC, but is common to other types of fuel cells.

  In this specification, the technique which can solve the subject mentioned above is disclosed.

  The technology disclosed in the present specification can be realized as, for example, the following forms.

(1) A fuel cell stack disclosed in the present specification includes a plurality of power generation units arranged side by side in a first direction and a plurality of bolts extending in the first direction, and is fastened by each of the bolts. In the fuel cell stack in which a plurality of gas flow paths extending over the plurality of power generation units are formed, each of the power generation units includes an air electrode and a fuel that face each other in the first direction with the electrolyte layer and the electrolyte layer interposed therebetween. A first through hole that constitutes one of a single cell including an electrode, a fuel chamber that faces the fuel electrode, and an air chamber that faces the air electrode, and a second through hole that constitutes the gas flow path And at least one communication channel that communicates the one of the fuel chamber and the air chamber with the gas channel, and a frame member formed by one or a plurality of the power generation units. The above-mentioned basic unit The thermal expansion coefficient of the frame member is such that the temperature of the fuel cell stack is lower than that of the reference power generation unit. It is characterized by being smaller than the coefficient. According to the present fuel cell stack, the difference in thermal expansion amount of the frame member during rated operation can be reduced between the reference power generation unit and the low-temperature power generation unit. The difference in area and length can be reduced, and the difference in gas flow rate between the reference power generation unit and the low temperature power generation unit due to the difference in cross-sectional area and length of the communication channel can be reduced. A decrease in power generation performance of the fuel cell stack can be suppressed.

(2) In the fuel cell stack, the cross-sectional area of the cross section orthogonal to the gas flow direction of the communication flow path at normal temperature is the cross-sectional area at a specific position of each communication flow path in the reference power generation unit. It is good also as a structure smaller than the cross-sectional area in the position corresponding to the said specific position of each said corresponding communication flow path in a partial power generation unit. According to the fuel cell stack, the cross-sectional area of the communication channel in the reference power generation unit can be brought close to the cross-sectional area of the communication channel in the low-temperature power generation unit during rated operation. Thus, the difference in gas flow rate between the reference power generation unit and the low-temperature power generation unit due to the above can be reduced, and a decrease in the power generation performance of the fuel cell stack can be suppressed.

(3) In the fuel cell stack, for the length along the gas flow direction of the communication channel at normal temperature, the length of each communication channel in the reference power generation unit corresponds to the length in the low-temperature power generation unit. It is good also as a structure longer than the length of each said communicating flow path. According to this fuel cell stack, the length of the communication channel in the reference power generation unit can be brought close to the length of the communication channel in the low-temperature power generation unit during rated operation. Thus, the difference in gas flow rate between the reference power generation unit and the low-temperature power generation unit due to the above can be reduced, and a decrease in the power generation performance of the fuel cell stack can be suppressed.

(4) In the fuel cell stack, the ratio of the length along the gas flow direction of the communication flow path to the cross sectional area of the cross section perpendicular to the gas flow direction at a specific position of the communication flow path is a cross-sectional area length ratio. The absolute value of the difference between the cross-sectional area length ratio of each communication channel of the reference power generation unit and the cross-sectional area length ratio of each communication channel corresponding to the low-temperature power generation unit is rated operation. The absolute value of the difference at the time may be smaller than the absolute value of the difference at normal temperature. According to this fuel cell stack, regarding the cross-sectional area length ratio of the communication flow path, which is an index correlated with the magnitude of the pressure loss of the communication flow path, the cross-sectional area length ratio of each communication flow path of the reference power generation unit and the low temperature part The absolute value of the difference between the cross-sectional area length ratios of the corresponding communication channels in the power generation unit can be made smaller than the absolute value of the difference at normal temperature because the absolute value of the difference during rated operation can be made smaller. The difference in gas flow rate between the reference power generation unit and the low-temperature power generation unit due to the difference in pressure loss can be reduced, and the decrease in power generation performance of the fuel cell stack can be suppressed.

  The technology disclosed in this specification can be realized in various forms, for example, in the form of a fuel cell stack, a power generation module including the fuel cell stack, a fuel cell system including the power generation module, and the like. Is possible.

1 is an explanatory diagram schematically showing a configuration of a fuel cell stack 100 in a first embodiment. FIG. 1 is an explanatory diagram schematically showing a configuration of a fuel cell stack 100 in a first embodiment. FIG. 1 is an explanatory diagram schematically showing a configuration of a fuel cell stack 100 in a first embodiment. FIG. 1 is an explanatory diagram schematically showing a configuration of a fuel cell stack 100 in a first embodiment. FIG. 1 is an explanatory diagram schematically showing a configuration of a fuel cell stack 100 in a first embodiment. FIG. 1 is an explanatory diagram schematically showing a configuration of a fuel cell stack 100 in a first embodiment. FIG. 4 is an explanatory diagram showing a detailed configuration of a power generation unit 102. FIG. 4 is an explanatory diagram showing a detailed configuration of a power generation unit 102. FIG. 4 is an explanatory diagram showing a detailed configuration of a power generation unit 102. FIG. 4 is an explanatory diagram showing a detailed configuration of a power generation unit 102. FIG. It is explanatory drawing which shows roughly the planar structure of the upper side of the heat exchange part 103. FIG. 4 is an explanatory diagram showing an example of a temperature distribution during rated operation of the fuel cell stack 100. FIG. FIG. 4 is an explanatory diagram showing a configuration of a fuel electrode side frame 140 in each power generation unit 102. FIG. 4 is an explanatory diagram showing a configuration of a fuel electrode side frame 140 in each power generation unit 102. It is explanatory drawing which shows schematically the structure of the fuel cell stack 100a in 2nd Embodiment. It is explanatory drawing which shows schematically the structure of the fuel cell stack 100a in 2nd Embodiment. It is explanatory drawing which shows an example of the temperature distribution at the time of the rated driving | operation of the fuel cell stack 100a of 2nd Embodiment. It is explanatory drawing which shows an example of the temperature distribution at the time of the rated driving | operation of the fuel cell stack 100b of 3rd Embodiment.

A. First embodiment:
A-1. Constitution:
(Configuration of fuel cell stack 100)
1 to 6 are explanatory views schematically showing the configuration of the fuel cell stack 100 in the first embodiment. FIG. 1 shows an external configuration of the fuel cell stack 100, FIG. 2 shows a planar configuration of the upper side of the fuel cell stack 100, and FIG. FIG. 4 shows a cross-sectional configuration of the fuel cell stack 100 at the position IV-IV in FIGS. 1 to 3, and FIG. 5 shows a plan configuration in FIGS. A cross-sectional configuration of the fuel cell stack 100 at a position VV is shown, and FIG. 6 shows a cross-sectional configuration of the fuel cell stack 100 at a position VI-VI in FIGS. 1 to 3. In each figure, XYZ axes orthogonal to each other for specifying the direction are shown. In this specification, for the sake of convenience, the positive direction of the Z axis is referred to as the upward direction, and the negative direction of the Z axis is referred to as the downward direction. However, the fuel cell stack 100 is actually different from such an orientation. It may be installed. The same applies to FIG.

  The fuel cell stack 100 includes a plurality of (six in this embodiment) power generation units 102, a heat exchange unit 103, and a pair of end plates 104 and 106. The six power generation units 102 are arranged side by side in a predetermined arrangement direction (vertical direction in the present embodiment). However, among the six power generation units 102, the three power generation units 102 are arranged adjacent to each other, and the remaining three power generation units 102 are also arranged adjacent to each other, so that the three power generation units 102 and the remaining power generation units 102 are arranged. A heat exchanging unit 103 is disposed between the three power generation units 102. That is, the heat exchanging unit 103 is arranged near the center in the vertical direction in the assembly composed of the six power generation units 102 and the heat exchanging unit 103. The pair of end plates 104 and 106 are arranged so as to sandwich an assembly composed of the six power generation units 102 and the heat exchange unit 103 from above and below. The arrangement direction (vertical direction) corresponds to the first direction.

  A plurality of (eight in this embodiment) holes penetrating in the vertical direction are formed in the peripheral portions around the Z direction of each layer (power generation unit 102, heat exchange unit 103, end plates 104, 106) constituting the fuel cell stack 100. The corresponding holes formed in each layer communicate with each other in the vertical direction to form a communication hole 108 extending in the vertical direction from one end plate 104 to the other end plate 106.

  Bolts 22 extending in the vertical direction are inserted into the communication holes 108, and the fuel cell stack 100 is fastened by the bolts 22 and nuts 24 fitted on both sides of the bolts 22. 4 to 6, between the nut 24 fitted on one side (upper side) of the bolt 22 and the upper surface of the end plate 104 constituting the upper end of the fuel cell stack 100, and the bolt An insulating sheet 26 is interposed between the nut 24 fitted on the other side (lower side) of 22 and the lower surface of the end plate 106 constituting the lower end of the fuel cell stack 100. However, in a place where a gas passage member 27 described later is provided, an insulating sheet disposed between the nut 24 and the surface of the end plate 106 on the upper and lower sides of the gas passage member 27 and the gas passage member 27, respectively. 26 is interposed. The insulating sheet 26 is made of, for example, a mica sheet, a ceramic fiber sheet, a ceramic powder sheet, a glass sheet, a glass ceramic composite agent, or the like.

  The outer diameter of the shaft portion of each bolt 22 is smaller than the inner diameter of each communication hole 108. Therefore, a space is secured between the outer peripheral surface of the shaft portion of each bolt 22 and the inner peripheral surface of each communication hole 108. As shown in FIGS. 2 to 4, a bolt 22 (bolt 22 </ b> A) is located near one vertex (vertex on the Y-axis negative direction side and X-axis negative direction side) on the outer periphery around the Z direction of the fuel cell stack 100. The formed space functions as an oxidant gas introduction manifold 161 that is a gas flow path into which the oxidant gas OG is introduced from the outside of the fuel cell stack 100, and one side on the outer periphery of the fuel cell stack 100 around the Z direction. The space formed by the bolt 22 (bolt 22C) located near the midpoint of the two sides parallel to the Y-axis (the side on the X-axis positive direction side) is an oxidant discharged from the heat exchange unit 103. It functions as an oxidant gas supply manifold 163 that is a gas flow path that carries the gas OG toward each power generation unit 102. As shown in FIGS. 2, 3, and 5, one side of the outer periphery of the fuel cell stack 100 around the Z direction (the side on the negative X-axis side of the two sides parallel to the Y axis) The space formed by the bolts 22 (bolts 22B) located near the midpoint discharges the oxidant off-gas OOG, which is an unreacted oxidant gas OG discharged from each power generation unit 102, to the outside of the fuel cell stack 100. Functions as an oxidant gas discharge manifold 162. In the present embodiment, for example, air is used as the oxidant gas OG.

  2, 3, and 6, one side of the outer periphery of the fuel cell stack 100 around the Z direction (the side on the Y axis positive direction side of the two sides parallel to the X axis) In the space formed by the bolts 22 (bolts 22D) located near the midpoint, the fuel gas FG is introduced from the outside of the fuel cell stack 100 and the fuel gas FG is supplied to each power generation unit 102. The space formed by the bolt 22 (bolt 22E) located near the midpoint of the opposite side of the side (the side on the Y axis negative direction side of the two sides parallel to the X axis) is The fuel gas discharge manifold 172 discharges the fuel off-gas FOG, which is an unreacted fuel gas FG discharged from each power generation unit 102, to the outside of the fuel cell stack 100. In the present embodiment, for example, hydrogen-rich gas obtained by reforming city gas is used as the fuel gas FG.

  As shown in FIGS. 4 to 6, the fuel cell stack 100 is provided with four gas passage members 27. Each gas passage member 27 has a hollow cylindrical main body portion 28 and a hollow cylindrical branch portion 29 branched from the side surface of the main body portion 28. The hole of the branch part 29 communicates with the hole of the main body part 28. A gas pipe (not shown) is connected to the branch portion 29 of each gas passage member 27. As shown in FIG. 4, the hole of the main body portion 28 of the gas passage member 27 arranged at the position of the bolt 22 </ b> A that forms the oxidant gas introduction manifold 161 communicates with the oxidant gas introduction manifold 161. As shown in FIG. 5, the hole of the main body portion 28 of the gas passage member 27 disposed at the position of the bolt 22 </ b> B that forms the oxidant gas discharge manifold 162 communicates with the oxidant gas discharge manifold 162. Further, as shown in FIG. 6, the hole of the main body portion 28 of the gas passage member 27 arranged at the position of the bolt 22D forming the fuel gas introduction manifold 171 communicates with the fuel gas introduction manifold 171 and the fuel gas The hole of the main body portion 28 of the gas passage member 27 disposed at the position of the bolt 22 </ b> E forming the discharge manifold 172 communicates with the fuel gas discharge manifold 172.

(Configuration of end plates 104 and 106)
The pair of end plates 104 and 106 are rectangular flat plate-shaped conductive members, and are formed of, for example, stainless steel. One end plate 104 is disposed on the upper side of the power generation unit 102 located on the uppermost side, and the other end plate 106 is disposed on the lower side of the power generation unit 102 located on the lowermost side. The plurality of power generation units 102 and the heat exchange unit 103 are held in a pressed state by a pair of end plates 104 and 106. The upper end plate 104 functions as a positive output terminal of the fuel cell stack 100, and the lower end plate 106 functions as a negative output terminal of the fuel cell stack 100.

(Configuration of power generation unit 102)
7 to 10 are explanatory diagrams showing the detailed configuration of the power generation unit 102. FIG. FIG. 7 shows a cross-sectional configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. 5, and FIG. 8 shows adjacent to each other at the same position as the cross section shown in FIG. 9 shows a cross-sectional configuration of the two power generation units 102. FIG. 9 shows a cross-sectional configuration of the power generation unit 102 at the position IX-IX in FIG. 7, and FIG. A cross-sectional configuration of the power generation unit 102 at the position X is shown.

  As shown in FIGS. 7 and 8, the power generation unit 102 that is the minimum unit of power generation includes a single cell 110, a separator 120, an air electrode side frame 130, an air electrode side current collector 134, and a fuel electrode side frame. 140, a fuel electrode side current collector 144, and a pair of interconnectors 150 constituting the uppermost layer and the lowermost layer of the power generation unit 102. A hole corresponding to the above-described communication hole 108 into which the bolt 22 is inserted is formed in the peripheral portion around the Z direction in the separator 120, the air electrode side frame 130, the fuel electrode side frame 140, and the interconnector 150.

  The interconnector 150 is a rectangular flat plate-shaped conductive member, and is formed of, for example, ferritic stainless steel. The interconnector 150 ensures electrical continuity between the power generation units 102 and prevents reaction gas from being mixed between the power generation units 102. In the present embodiment, when two power generation units 102 are arranged adjacent to each other, one interconnector 150 is shared by two adjacent power generation units 102. That is, the upper interconnector 150 in a power generation unit 102 is the same member as the lower interconnector 150 in another power generation unit 102 adjacent to the upper side of the power generation unit 102. Further, since the fuel cell stack 100 includes the pair of end plates 104 and 106, the power generation unit 102 located at the top in the fuel cell stack 100 does not include the upper interconnector 150 and is located at the bottom. The power generation unit 102 does not include the lower interconnector 150 (see FIGS. 4 to 6).

  The unit cell 110 includes an electrolyte layer 112, and an air electrode (cathode) 114 and a fuel electrode (anode) 116 that face each other in the vertical direction (the arrangement direction in which the power generation units 102 are arranged) with the electrolyte layer 112 interposed therebetween. The single cell 110 of the present embodiment is a fuel electrode-supported single cell that supports the electrolyte layer 112 and the air electrode 114 with the fuel electrode 116.

  The electrolyte layer 112 is a rectangular flat plate-like member, such as YSZ (yttria stabilized zirconia), ScSZ (scandia stabilized zirconia), SDC (samarium doped ceria), GDC (gadolinium doped ceria), perovskite oxide, etc. The solid oxide is formed. The air electrode 114 is a rectangular flat plate-shaped member, and is formed of, for example, a perovskite oxide (for example, LSCF (lanthanum strontium cobalt iron oxide), LSM (lanthanum strontium manganese oxide), LNF (lanthanum nickel iron)). ing. The fuel electrode 116 is a rectangular flat plate-like member, and is formed of, for example, Ni (nickel), cermet made of Ni and ceramic particles, Ni-based alloy, or the like. Thus, the single cell 110 (power generation unit 102) of the present embodiment is a solid oxide fuel cell (SOFC) that uses a solid oxide as an electrolyte.

  The separator 120 is a frame-like member in which a rectangular hole 121 penetrating in the vertical direction is formed near the center, and is made of, for example, metal. The peripheral part of the hole 121 in the separator 120 is opposed to the peripheral part of the surface of the electrolyte layer 112 on the air electrode 114 side. The separator 120 is bonded to the electrolyte layer 112 (single cell 110) by a bonding portion 124 formed of a brazing material (for example, Ag brazing) disposed in the facing portion. The separator 120 divides the air chamber 166 facing the air electrode 114 and the fuel chamber 176 facing the fuel electrode 116, and gas leaks from one electrode side to the other electrode side in the peripheral portion of the single cell 110. It is suppressed. The single cell 110 to which the separator 120 is joined is referred to as a single cell with a separator.

  As shown in FIGS. 7 to 9, the air electrode side frame 130 is a frame-like member in which a rectangular through hole 131 penetrating in the vertical direction is formed near the center. For example, the air electrode side frame 130 is formed of an insulator such as mica. Has been. The air electrode side frame 130 is in contact with the peripheral edge portion of the surface of the separator 120 opposite to the side facing the electrolyte layer 112 and the peripheral edge portion of the surface of the interconnector 150 facing the air electrode 114. . The through hole 131 of the air electrode side frame 130 forms an air chamber 166 that faces the air electrode 114. The pair of interconnectors 150 included in the power generation unit 102 is electrically insulated by the air electrode side frame 130.

  Further, the air electrode side frame 130 includes a first oxidant gas supply communication hole 191 extending from a through hole constituting the oxidant gas supply manifold 163 in the Y-axis positive direction and the Y-axis negative direction, and a first oxidant gas supply. A plurality of second oxidant gas supply communication holes 192 extending in the X-axis direction are formed so as to connect the communication holes 191 and the through holes 131. The first oxidant gas supply communication hole 191 and the second oxidant gas supply communication hole 192 form a plurality of communication channels that connect the oxidant gas supply manifold 163 and the air chamber 166. Similarly, in the air electrode side frame 130, first oxidant gas discharge communication holes 193, 193, and through holes 131 extending from the through holes constituting the oxidant gas discharge manifold 162 in the Y axis positive direction and the Y axis negative direction. A plurality of second oxidant gas discharge communication holes 194 extending in the X-axis direction are formed so as to communicate with each other. The first oxidant gas discharge communication hole 193 and the second oxidant gas discharge communication hole 194 form a plurality of communication channels that connect the oxidant gas discharge manifold 162 and the air chamber 166.

  As shown in FIGS. 7, 8 and 10, the fuel electrode side frame 140 is a frame-like member in which a rectangular through hole 141 penetrating in the vertical direction is formed in the vicinity of the center. ing. The fuel electrode side frame 140 is in contact with the peripheral portion of the surface of the separator 120 facing the electrolyte layer 112 and the peripheral portion of the surface of the interconnector 150 facing the fuel electrode 116. In the present embodiment, the fuel electrode side frame 140 is welded to the separator 120 and the interconnector 150. The through hole 141 of the fuel electrode side frame 140 forms a fuel chamber 176 that faces the fuel electrode 116.

  Further, the fuel electrode side frame 140 includes a first fuel gas supply communication hole 195 extending from the through hole constituting the fuel gas introduction manifold 171 in the X-axis positive direction and the X-axis negative direction, and the first fuel gas supply communication hole 195. A plurality of second fuel gas supply communication holes 196 extending in the Y-axis direction are formed so as to communicate with the through hole 141. The first fuel gas supply communication hole 195 and each second fuel gas supply communication hole 196 form a plurality of communication flow paths that connect the fuel gas introduction manifold 171 and the fuel chamber 176. Similarly, the fuel electrode side frame 140 includes a first fuel gas discharge communication hole 197 extending from the through hole constituting the fuel gas discharge manifold 172 in the X-axis positive direction and the X-axis negative direction, and the first fuel gas discharge communication hole. A plurality of second fuel gas discharge communication holes 198 extending in the Y-axis direction are formed so as to allow communication between 197 and the through holes 141. The first fuel gas discharge communication hole 197 and the respective second fuel gas discharge communication holes 198 form a plurality of communication flow paths that connect the fuel gas discharge manifold 172 and the fuel chamber 176.

  The air electrode side current collector 134 is disposed in the air chamber 166 as shown in FIGS. 7 to 9. The air electrode side current collector 134 is composed of a plurality of substantially quadrangular columnar conductive members arranged at predetermined intervals, and is made of, for example, ferritic stainless steel. The air electrode side current collector 134 is brought into contact with the surface of the air electrode 114 opposite to the side facing the electrolyte layer 112 and the surface of the interconnector 150 facing the air electrode 114, whereby the air electrode 114 and the interconnector 150 are electrically connected. The air electrode side current collector 134 and the interconnector 150 may be formed as an integral member.

  The fuel electrode side current collector 144 is disposed in the fuel chamber 176 as shown in FIGS. 7, 8 and 10. The fuel electrode side current collector 144 includes an interconnector facing portion 146, a plurality of electrode facing portions 145, and a connecting portion 147 that connects each electrode facing portion 145 and the interconnector facing portion 146. Or nickel alloy, stainless steel or the like. Specifically, as shown in the partially enlarged view in FIG. 10, the fuel electrode side current collector 144 is manufactured by cutting a rectangular flat plate-shaped member and bending the plurality of rectangular portions. The The bent rectangular portion becomes the electrode facing portion 145, the flat plate portion other than the bent raised portion becomes the interconnector facing portion 146, and the portion connecting the electrode facing portion 145 and the interconnector facing portion 146 is connected. Part 147. In addition, in the partial enlarged view in FIG. 10, in order to show the manufacturing method of the fuel electrode side collector 144, the state before the bending raising process of a part of several rectangular part is shown. Each electrode facing portion 145 contacts the surface of the fuel electrode 116 opposite to the side facing the electrolyte layer 112, and the interconnector facing portion 146 contacts the surface of the interconnector 150 facing the fuel electrode 116. To do. Therefore, the fuel electrode side current collector 144 electrically connects the fuel electrode 116 and the interconnector 150. Note that a spacer 149 made of, for example, mica is disposed between the electrode facing portion 145 and the interconnector facing portion 146. Therefore, the fuel electrode side current collector 144 follows the deformation of the power generation unit 102 due to the temperature cycle or reaction gas pressure fluctuation, and the fuel electrode 116 and the interconnector 150 are electrically connected via the fuel electrode side current collector 144. Maintained well.

(Configuration of heat exchange unit 103)
FIG. 11 is an explanatory diagram schematically showing a planar configuration on the upper side of the heat exchange unit 103. As shown in FIGS. 4 to 6 and FIG. 11, the heat exchanging portion 103 is a rectangular flat plate-like member, and is formed of, for example, ferritic stainless steel. As described above, eight holes constituting the communication hole 108 into which the bolt 22 is inserted are formed in the peripheral portion around the Z direction of the heat exchanging portion 103. Further, a hole 182 penetrating in the vertical direction is formed near the center of the heat exchanging portion 103. Further, the heat exchange unit 103 has a communication hole 184 communicating with the central hole 182 and the communication hole 108 forming the oxidant gas introduction manifold 161, and a communication forming the central hole 182 and the oxidant gas supply manifold 163. A communication hole 186 that communicates with the hole 108 is formed. The heat exchange unit 103 includes a lower interconnector 150 included in the power generation unit 102 adjacent to the upper side of the heat exchange unit 103 and an upper interconnector 150 included in the power generation unit 102 adjacent to the lower side of the heat exchange unit 103. And is sandwiched between. A space formed by the holes 182, the communication holes 184, and the communication holes 186 between these interconnectors 150 functions as a heat exchange channel 188 through which the oxidant gas OG flows for heat exchange described later.

A-2. Operation of the fuel cell stack 100:
As shown in FIG. 4, when the oxidant gas OG is supplied via a gas pipe (not shown) connected to the branch portion 29 of the gas passage member 27 provided at the position of the oxidant gas introduction manifold 161. The oxidant gas OG is supplied to the oxidant gas introduction manifold 161 through the branch portion 29 of the gas passage member 27 and the hole of the main body portion 28. As shown in FIGS. 4 and 11, the oxidant gas OG supplied to the oxidant gas introduction manifold 161 flows into the heat exchange channel 188 formed in the heat exchange unit 103, and the heat exchange channel 188. And is discharged to the oxidant gas supply manifold 163. Since the oxidant gas introduction manifold 161 is not in communication with the air chamber 166 of each power generation unit 102, the oxidant gas OG is supplied from the oxidant gas introduction manifold 161 to the air chamber 166 of each power generation unit 102. There is nothing. The oxidant gas OG discharged to the oxidant gas supply manifold 163 is supplied from the oxidant gas supply manifold 163 to the first oxidant gas of each power generation unit 102 as shown in FIGS. 4, 5, 7 and 9. The air is supplied to the air chamber 166 through the supply communication hole 191 and the second oxidant gas supply communication hole 192.

  Further, as shown in FIGS. 6, 8, and 10, the fuel gas is connected via a gas pipe (not shown) connected to the branch portion 29 of the gas passage member 27 provided at the position of the fuel gas introduction manifold 171. When the FG is supplied, the fuel gas FG is supplied to the fuel gas introduction manifold 171 through the branch portion 29 of the gas passage member 27 and the hole of the main body portion 28, and from the fuel gas introduction manifold 171, The fuel is supplied to the fuel chamber 176 through the first fuel gas supply communication hole 195 and the second fuel gas supply communication hole 196.

  When the oxidant gas OG is supplied to the air chamber 166 of each power generation unit 102 and the fuel gas FG is supplied to the fuel chamber 176, power is generated by an electrochemical reaction between the oxidant gas OG and the fuel gas FG in the single cell 110. Is called. This power generation reaction is an exothermic reaction. In each power generation unit 102, the air electrode 114 of the single cell 110 is electrically connected to one interconnector 150 via the air electrode side current collector 134, and the fuel electrode 116 is connected via the fuel electrode side current collector 144. The other interconnector 150 is electrically connected. In addition, the plurality of power generation units 102 included in the fuel cell stack 100 are electrically connected in series although the heat exchange unit 103 is interposed therebetween. Therefore, electrical energy generated in each power generation unit 102 is taken out from the end plates 104 and 106 that function as output terminals of the fuel cell stack 100. Since SOFC generates power at a relatively high temperature (for example, 700 ° C. to 1000 ° C.), the fuel cell stack 100 is heated by a heater (after the startup until the high temperature can be maintained by heat generated by power generation (Not shown).

  As shown in FIGS. 5, 7, and 9, the oxidant off-gas OOG that is the oxidant gas OG that has not been used for the power generation reaction in each power generation unit 102 is discharged from the air chamber 166 to the second oxidant gas discharge passage 194. And the holes of the main body portion 28 and the branch portion 29 of the gas passage member 27 that are discharged to the oxidant gas discharge manifold 162 through the first oxidant gas discharge communication hole 193 and further provided at the position of the oxidant gas discharge manifold 162. Then, the gas is discharged to the outside of the fuel cell stack 100 through a gas pipe (not shown) connected to the branch portion 29. Further, as shown in FIGS. 6, 8, and 10, the fuel off-gas FOG that is the fuel gas FG that has not been used for the power generation reaction in each power generation unit 102 is supplied from the fuel chamber 176 to the second fuel gas discharge communication hole 198 and It is discharged to the fuel gas discharge manifold 172 through the first fuel gas discharge communication hole 197, and further through the holes of the main body portion 28 and the branch portion 29 of the gas passage member 27 provided at the position of the fuel gas discharge manifold 172. The gas is discharged outside the fuel cell stack 100 through a gas pipe (not shown) connected to the branch portion 29.

A-3. Detailed configuration of fuel electrode side frame 140:
During the rated operation of the fuel cell stack 100, the temperature Tr of each power generation unit 102 may vary depending on the position of the power generation unit 102 in the fuel cell stack 100. In the fuel cell stack 100 of the present embodiment, the configuration of the fuel electrode side frame 140 in each power generation unit 102 differs depending on the temperature of each power generation unit 102 during rated operation.

  FIG. 12 is an explanatory diagram showing an example of a temperature distribution during rated operation of the fuel cell stack 100. FIG. 12 shows a schematic configuration along the vertical direction (Z-axis direction) of the fuel cell stack 100 and an example of the temperature Tr of each power generation unit 102 during rated operation. Since the power generation reaction in the power generation unit 102 is an exothermic reaction, during rated operation, the temperature Tr tends to be high at locations where the power generation units 102 are arranged at a high density, and conversely, the power generation units 102 are arranged at a low density. The temperature Tr tends to be low at the location. As described above, since the relatively low-temperature oxidant gas introduced from the outside of the fuel cell stack 100 flows into the heat exchange unit 103, the temperature Tr is low in the power generation unit 102 close to the heat exchange unit 103. Prone. Therefore, like the fuel cell stack 100 of the present embodiment, among the six power generation units 102, the three power generation units 102 are arranged adjacent to each other, and the remaining three power generation units 102 are also arranged adjacent to each other. In the configuration in which the heat exchanging unit 103 is disposed between the three power generation units 102 and the remaining three power generation units 102, for example, the two power generation units 102 are disposed so as to be sandwiched between the power generation units 102, respectively. The power generation unit 102 (hereinafter referred to as “high temperature power generation unit 102H”) has the highest temperature, and the two power generation units 102 adjacent to the end plates 104 and 106 (hereinafter referred to as “low temperature power generation unit 102L”) have the lowest temperature. Two power generation units 102 adjacent to the heat exchanging unit 103 (hereinafter referred to as “medium temperature unit power generation unit 102M”) have an intermediate temperature between them. The temperature Tr during the rated operation is, for example, 750 ° C. in the high temperature power generation unit 102H, 680 ° C. in the medium temperature power generation unit 102M, and 620 ° C. in the low temperature power generation unit 102L.

  When the intermediate temperature power generation unit 102M corresponds to the “reference power generation unit” in the claims, the low temperature power generation unit 102L corresponds to the “low temperature power generation unit” in the claims. Further, when the high temperature power generation unit 102H corresponds to the “reference power generation unit” in the claims, the middle temperature power generation unit 102M and the low temperature power generation unit 102L are the “low temperature power generation units” in the claims. Equivalent to.

FIGS. 13 and 14 are explanatory views showing the configuration of the fuel electrode side frame 140 in each power generation unit 102. In the present embodiment, the thermal expansion coefficient C (H) of the fuel electrode side frame 140 included in the high temperature power generation unit 102H, and the thermal expansion coefficient C (M) of the fuel electrode side frame 140 included in the intermediate temperature power generation unit 102M. The relationship with the thermal expansion coefficient C (L) of the fuel electrode side frame 140 included in the low temperature power generation unit 102L is the relationship shown in the following equation (1).
C (H) <C (M) <C (L) (1)

For example, the fuel electrode side frame 140 included in the high temperature power generation unit 102H is formed of SUS430 (thermal expansion coefficient C (H): 12.8 × 10 ⁻⁶ (/ ° C.)) and included in the intermediate temperature power generation unit 102M. The fuel electrode side frame 140 is formed of SUS310 (thermal expansion coefficient C (M): 17.5 × 10 ⁻⁶ (/ ° C.)), and the fuel electrode side frame 140 included in the low temperature part power generation unit 102L is formed of SUS304 (thermal expansion). If formed by the coefficient C (L): 18.7 × 10 ⁻⁶ (/ ° C.), the above formula (1) is satisfied.

  Further, FIG. 13 shows one second fuel gas supply communication hole 196 (see FIG. 10) formed in the fuel electrode side frame 140 of each power generation unit 102 at normal temperature (for example, 25 ° C.) and during rated operation. ) Is a cross section perpendicular to the gas flow direction (cross section at the position of XIII-XIII in the same figure). In the following description, among the cross-sectional area A of the cross section orthogonal to the gas flow direction of the second fuel gas supply communication hole 196, the cross-sectional area A at normal temperature is represented as the cross-sectional area An at normal temperature, and the cross-sectional area A at rated operation. Is represented as a sectional area Ar during rated operation. As shown in FIG. 10, the first fuel gas supply communication hole 195 and the second fuel gas supply communication holes 196 form a plurality of communication flow paths that connect the fuel gas introduction manifold 171 and the fuel chamber 176. Therefore, it can be said that the cross-sectional area A of the second fuel gas supply communication hole 196 is a cross-sectional area at a specific position of the communication flow path.

As shown in FIG. 13, the cross-sectional area An at normal temperature of the second fuel gas supply communication hole 196 is different for each power generation unit 102. Specifically, the room temperature sectional area An (H) of the second fuel gas supply communication hole 196 in the high temperature power generation unit 102H and the room temperature sectional area An of the second fuel gas supply communication hole 196 in the middle temperature power generation unit 102M. The relationship between (M) and the cross-sectional area An (L) at the normal temperature of the second fuel gas supply communication hole 196 in the low temperature power generation unit 102L is a relationship represented by the following equation (2). Note that this equation (2) indicates the relationship with respect to the corresponding second fuel gas supply communication hole 196 (at the same position) in each of the high temperature section power generation unit 102H, the middle temperature section power generation unit 102M, and the low temperature section power generation unit 102L. It is shown. In each of the high temperature section power generation unit 102H, the middle temperature section power generation unit 102M, and the low temperature section power generation unit 102L, the second fuel gas supply communication holes 196 at different positions do not necessarily have to satisfy the relationship of Expression (2). No. The same applies to formula (3) described later.
An (H) <An (M) <An (L) (2)

  FIG. 14 shows a cross section parallel to the gas flow direction of one second fuel gas supply communication hole 196 formed in the fuel electrode side frame 140 of each power generation unit 102 at normal temperature and during rated operation, respectively. The enlarged view of the Px part of FIG. 10 is shown. In the following description, the length L of the second fuel gas supply communication hole 196 in the gas flow direction (the distance from the connection position with the first fuel gas supply communication hole 195 to the connection position with the through hole 141) is within. The length L at normal temperature is expressed as a length Ln at normal temperature, and the length L at rated operation is expressed as a length Lr during rated operation. As described above, the first fuel gas supply communication hole 195 and each of the second fuel gas supply communication holes 196 form a plurality of communication flow paths that connect the fuel gas introduction manifold 171 and the fuel chamber 176. When the length L of the second fuel gas supply communication hole 196 is long, the length of the communication flow path is also long.

As shown in FIG. 14, the normal temperature length Ln of the second fuel gas supply communication hole 196 is different for each power generation unit 102. Specifically, the normal temperature length Ln (H) of the second fuel gas supply communication hole 196 in the high temperature power generation unit 102H and the normal temperature length Ln of the second fuel gas supply communication hole 196 in the medium temperature power generation unit 102M. The relationship between (M) and the length Ln (L) of the second fuel gas supply communication hole 196 in the low temperature power generation unit 102L at normal temperature is a relationship represented by the following expression (3).
Ln (H)> Ln (M)> Ln (L) (3)

  As described above, during the rated operation, the temperature of each power generation unit 102 is higher than the normal temperature, and thus the fuel electrode side frame 140 included in each power generation unit 102 is in a state of thermal expansion as compared with the normal temperature state. Since the fuel cell stack 100 is fastened by the bolts 22, each layer constituting the fuel cell stack 100 is restricted from expanding in the outer peripheral direction. Therefore, during rated operation, the fuel electrode side frame 140 is arranged so that various holes (the second fuel gas supply communication hole 196 and the through hole 141 constituting the fuel chamber 176) formed in the fuel electrode side frame 140 are reduced. Thermal expansion. Therefore, as shown in FIG. 13 and FIG. 14, the rated operating cross-sectional area Ar of the second fuel gas supply communication hole 196 is any of the high temperature power generation unit 102H, the intermediate temperature power generation unit 102M, and the low temperature power generation unit 102L. The sectional area An becomes smaller than the room temperature An at normal temperature, and the length Lr during rated operation becomes longer than the length Ln at normal temperature. 13 and 14 indicate the shape of the second fuel gas supply communication hole 196 at the rated operation.

  Here, if the amount of thermal expansion of the fuel electrode side frame 140 during rated operation is relatively large, the reduction amount of the cross-sectional area A and the extension amount of the length L of the second fuel gas supply communication hole 196 are relatively large. Become. In the present embodiment, as shown in the above equation (1), the thermal expansion coefficient C of the fuel electrode side frame 140 is smaller in the power generation unit 102 having a higher temperature during rated operation. Therefore, the difference in the thermal expansion amount of the fuel electrode side frame 140 due to the temperature difference of each power generation unit 102 during rated operation is reduced. As a result, the difference in the reduction amount of the cross-sectional area A of the second fuel gas supply communication hole 196 and the difference in the extension amount of the length L are reduced.

  The thermal expansion coefficient C of the fuel electrode side frame 140 of each power generation unit 102 is specifically determined according to the material used for forming the fuel electrode side frame 140. Further, the temperature Tr of each power generation unit 102 during rated operation is specifically determined according to the configuration and operation method of the fuel cell stack 100. Therefore, the difference in thermal expansion amount due to the difference in the thermal expansion coefficient C of the fuel electrode side frame 140 between the high temperature section power generation unit 102H, the middle temperature section power generation unit 102M, and the low temperature section power generation unit 102L, and the rated operation The difference in the amount of thermal expansion caused by the difference in temperature Tr is not necessarily the same level. For example, in this embodiment, the difference in thermal expansion due to the difference in thermal expansion coefficient C of the fuel electrode side frame 140 is larger than the difference in thermal expansion due to the difference in temperature Tr during rated operation. ing. Therefore, the amount of thermal expansion of the fuel electrode side frame 140 is smaller as the power generation unit 102 has a higher temperature during rated operation. However, in the present embodiment, as shown in the above formula (2), the power generation unit 102 having a higher temperature during rated operation has a smaller cross-sectional area An at normal temperature of the second fuel gas supply communication hole 196 ( As a result, as a result, the rated operation sectional area Ar (H) of the second fuel gas supply communication hole 196 in the high temperature power generation unit 102H and the second fuel gas supply communication hole 196 in the intermediate temperature power generation unit 102M are obtained. The rated operation sectional area Ar (M) and the rated operation sectional area Ar (L) of the second fuel gas supply communication hole 196 in the low temperature power generation unit 102L are substantially equal. Similarly, in the present embodiment, as shown in the above formula (3), the power generation unit 102 having a higher temperature during rated operation has a longer normal temperature length Ln of the second fuel gas supply communication hole 196. (See FIG. 14) As a result, the rated operating length Lr (H) of the second fuel gas supply communication hole 196 in the high temperature power generation unit 102H and the second fuel gas supply communication hole 196 in the intermediate temperature power generation unit 102M are obtained. The rated operating length Lr (M) of the second fuel gas supply communication hole 196 in the low temperature power generation unit 102L is substantially equal to the rated operating length Lr (L).

  If there is a difference in the rated operation length Lr and the rated operation cross-sectional area Ar of the second fuel gas supply communication hole 196 between the power generation units 102, the communication flow path formed by the second fuel gas supply communication hole 196 ( There is a difference in pressure loss between the fuel gas introduction manifold 171 and the flow path connecting the fuel chambers 176, and a difference occurs in the flow rate of the fuel gas supplied to each power generation unit 102, thereby reducing the power generation performance of the fuel cell stack 100. There is a fear. In the fuel cell stack 100 of the present embodiment, the rated operation cross-sectional area Ar (H) of the second fuel gas supply communication hole 196 in the high temperature power generation unit 102H and the second fuel gas supply communication hole 196 of the intermediate temperature power generation unit 102M. The rated operation sectional area Ar (M) is substantially equal to the rated operation sectional area Ar (L) of the second fuel gas supply communication hole 196 in the low temperature power generation unit 102L. Further, the rated operation length Lr (H) of the second fuel gas supply communication hole 196 in the high temperature section power generation unit 102H and the rated operation length Lr (M) of the second fuel gas supply communication hole 196 in the medium temperature section power generation unit 102M. ) And the rated operating length Lr (L) of the second fuel gas supply communication hole 196 in the low temperature power generation unit 102L are substantially equal. Therefore, the pressure loss of the communication flow path formed by the second fuel gas supply communication hole 196 between the power generation units 102 becomes substantially equal, and the flow rate difference of the fuel gas supplied to each power generation unit 102 is suppressed. As a result, a decrease in the power generation performance of the fuel cell stack 100 due to the difference in flow rate of the fuel gas supplied to each power generation unit 102 is suppressed.

  Note that the pressure loss of the communication flow path formed by the second fuel gas supply communication hole 196 increases as the length L of the second fuel gas supply communication hole 196 increases, and the second fuel gas supply communication hole 196 increases. The smaller the cross-sectional area A, the smaller. Therefore, in this specification, as an index correlating with the magnitude of the pressure loss of the communication flow path, the “cross-sectional area length ratio R”, which is the ratio of the length L to the cross-sectional area A of the second fuel gas supply communication hole 196, is used. Use. It can be said that the smaller the absolute value of the difference in the cross-sectional area length ratio R, the smaller the difference in pressure loss of the communication flow path among the high temperature section power generation unit 102H, the middle temperature section power generation unit 102M, and the low temperature section power generation unit 102L. In the fuel cell stack 100 of the present embodiment, since the above formulas (1) to (3) are satisfied, the absolute value of the difference in the cross-sectional area length ratio R during rated operation is the cross-sectional area length at normal temperature. The difference R becomes smaller than the absolute value of the difference, and as a result, the flow rate difference of the fuel gas due to the pressure loss difference of the communication flow path is suppressed, and the power generation performance of the fuel cell stack 100 is prevented from being lowered.

B. Second embodiment:
B-1. Constitution:
15 and 16 are explanatory views schematically showing the configuration of the fuel cell stack 100a in the second embodiment. FIG. 15 shows an external configuration of the fuel cell stack 100a. FIG. 16 shows a position corresponding to the position of the cross section shown in FIG. 5 of the first embodiment (position XVI-XVI in FIG. 15). A cross-sectional configuration of the fuel cell stack 100a is shown. Among the configurations of the fuel cell stack 100a in the second embodiment, the same configurations as those of the fuel cell stack 100 of the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted.

  The fuel cell stack 100a in the second embodiment is different from the fuel cell stack 100 of the first embodiment described above in that the heat exchange unit 103 is not provided. In this regard, the flow path configuration of the oxidant gas OG is also different. That is, in the second embodiment, the bolt located near the midpoint of one side (the X-axis positive direction side of the two sides parallel to the Y-axis) on the outer periphery around the Z-direction of the fuel cell stack 100a. A space formed by 22 (bolt 22A) functions as an oxidant gas introduction manifold 161 that is a gas flow path into which the oxidant gas OG is introduced from the outside of the fuel cell stack 100a.

B-2. Operation of the fuel cell stack 100a:
As in the first embodiment, the oxidant gas OG is supplied to the oxidant gas introduction manifold 161 via the branch part 29 of the gas passage member 27 provided at the position of the oxidant gas introduction manifold 161 and the hole of the main body part 28. Supplied. The oxidant gas OG supplied to the oxidant gas introduction manifold 161 is supplied to the air chamber 166 of each power generation unit 102. The subsequent flow of the oxidant gas OG is the same as in the first embodiment. Further, the flow of the fuel gas FG is the same as in the first embodiment. Also in the fuel cell stack 100a of the second embodiment, similarly to the first embodiment, power generation using the oxidant gas OG and the fuel gas FG is performed in each power generation unit 102, and the oxidant offgas OOG and the fuel offgas FOG are generated. It is discharged outside the fuel cell stack 100a.

B-3. Detailed configuration of fuel electrode side frame 140:
In the fuel cell stack 100a of the second embodiment, the temperature Tr of each power generation unit 102 during rated operation is different from that of the first embodiment. FIG. 17 is an explanatory diagram showing an example of a temperature distribution during rated operation of the fuel cell stack 100a of the second embodiment. As shown in FIG. 17, since the fuel cell stack 100a of the second embodiment does not include the heat exchange unit 103, for example, two power generation units 102 (hereinafter referred to as “high temperature”) near the center in the vertical direction (Z-axis direction). The power generation unit 102H ”is the highest temperature, the two power generation units 102 adjacent to the end plates 104 and 106 (hereinafter referred to as“ low temperature power generation unit 102L ”) are the lowest temperature, and the remaining two power generation units 102 ( Hereinafter, “medium temperature power generation unit 102M”) is an intermediate temperature between them.

  The fuel cell stack 100a of the second embodiment differs from the fuel cell stack 100 of the first embodiment in the positions of the high-temperature power generation unit 102H, the intermediate-temperature power generation unit 102M, and the low-temperature power generation unit 102L, but the high-temperature power generation unit 102H. The relationship between the thermal expansion coefficient C of the fuel electrode side frame 140 included in each of the intermediate temperature power generation unit 102M and the low temperature power generation unit 102 and the cross sectional area A and the length L of the second fuel gas supply communication hole 196 The relationship is the same as in the first embodiment. Therefore, also in the fuel cell stack 100a of the second embodiment, the pressure loss of the communication flow path formed by the second fuel gas supply communication hole 196 is substantially equal between the power generation units 102 and is supplied to each power generation unit 102. The difference in the flow rate of the fuel gas is suppressed, and the decrease in the power generation performance of the fuel cell stack 100a due to the difference in the flow rate of the fuel gas supplied to each power generation unit 102 is suppressed.

C. Third embodiment:
FIG. 18 is an explanatory diagram showing an example of a temperature distribution during rated operation of the fuel cell stack 100b of the third embodiment. The configuration of the fuel cell stack 100b in the third embodiment is the same as the configuration of the fuel cell stack 100a of the second embodiment described above. However, in the third embodiment, during rated operation of the fuel cell stack 100b, the fuel cell stack 100b is heated by the heat source HS disposed below the fuel cell stack 100b. Examples of the heat source HS include a gas burner and a combustion device that burns the oxidant off-gas and fuel off-gas discharged from the fuel cell stack 100b. The configuration of these heat sources HS is well known as described in, for example, Japanese Patent Laid-Open No. 2013-175354, and will not be described in detail here. In the third embodiment, since the fuel cell stack 100b is heated by the heat source HS, the temperature Tr of each power generation unit 102 during rated operation is different from that in the second embodiment. As shown in FIG. 18, in the third embodiment, for example, among the six power generation units 102, the third and second power generation units 102 from the bottom (hereinafter referred to as “high temperature power generation unit 102H”) are the most. The first and second power generation units 102 (hereinafter referred to as “low temperature power generation units 102L”) from the top become the lowest temperature, and the remaining two power generation units 102 (hereinafter referred to as “medium temperature power generation units 102M”). Temperature) is intermediate between the two.

  The fuel cell stack 100b of the third embodiment is different from the fuel cell stack 100a of the second embodiment in the positions of the high temperature power generation unit 102H, the intermediate temperature power generation unit 102M, and the low temperature power generation unit 102L, but the high temperature power generation unit 102H. The relationship between the thermal expansion coefficient C of the fuel electrode side frame 140 included in each of the intermediate temperature power generation unit 102M and the low temperature power generation unit 102 and the cross sectional area A and the length L of the second fuel gas supply communication hole 196 The relationship is the same as in the second embodiment. Therefore, also in the fuel cell stack 100b of the third embodiment, the pressure loss of the communication flow path formed by the second fuel gas supply communication hole 196 is substantially equal between the power generation units 102 and is supplied to each power generation unit 102. The difference in the flow rate of the fuel gas is suppressed, and the decrease in the power generation performance of the fuel cell stack 100b due to the difference in the flow rate of the fuel gas supplied to each power generation unit 102 is suppressed.

D. Variation:
In the above-described embodiment, the power generation unit 102 having a higher temperature during rated operation among the plurality of power generation units 102 included in the fuel cell stack 100 is reduced in the normal temperature cross-sectional area An of the second fuel gas supply communication hole 196. However, such a configuration is not necessarily required, and the cross-sectional area An at normal temperature of the second fuel gas supply communication hole 196 can be arbitrarily set regardless of the temperature at the rated operation. Even in such a case, if the power generation unit 102 having a higher temperature during rated operation is configured to have a smaller thermal expansion coefficient C of the fuel electrode side frame 140, the fuel electrode side due to the temperature difference of each power generation unit 102 during rated operation. The difference in thermal expansion amount of the frame 140 is reduced. As a result, the difference in reduction amount of the cross-sectional area A of the second fuel gas supply communication hole 196 is reduced, and the flow rate difference of the fuel gas supplied to each power generation unit 102 is reduced. Be suppressed.

  Similarly, in the above-described embodiment, among the plurality of power generation units 102 included in the fuel cell stack 100, the power generation unit 102 having a higher temperature during rated operation has the second fuel gas supply communication hole 196 at the normal temperature length Ln. Although it is long, it is not always necessary to have such a configuration, and the normal temperature length Ln of the second fuel gas supply communication hole 196 can be arbitrarily set regardless of the temperature during rated operation. Even in such a case, if the power generation unit 102 having a higher temperature during rated operation is configured to have a smaller thermal expansion coefficient C of the fuel electrode side frame 140, the fuel electrode side due to the temperature difference of each power generation unit 102 during rated operation. The difference in the thermal expansion amount of the frame 140 is reduced. As a result, the difference in the extension amount of the length L of the second fuel gas supply communication hole 196 is reduced, and the flow rate difference of the fuel gas supplied to each power generation unit 102 is reduced. It is suppressed.

  Further, in the above embodiment, the plurality of power generation units 102 included in the fuel cell stack 100 are classified into three types (a high temperature part power generation unit 102H, a medium temperature part power generation unit 102M, and a low temperature part power generation unit 102L) according to the temperature Tr during rated operation. However, the plurality of power generation units 102 may be classified into two types or four or more types. In any case, if the power generation unit 102 having a higher temperature during rated operation is configured to have a smaller thermal expansion coefficient C of the fuel electrode side frame 140, the fuel electrode side due to the temperature difference of each power generation unit 102 during rated operation. The difference in the thermal expansion amount of the frame 140 is reduced. As a result, the difference in the reduction amount of the cross-sectional area A and the difference in the extension amount of the length L of the second fuel gas supply communication hole 196 are reduced. The flow rate difference of the supplied fuel gas is suppressed.

  Further, in the above embodiment, the thermal expansion coefficient C of the fuel electrode side frame 140 is smaller for all the power generation units 102 included in the fuel cell stack 100 as the power generation unit 102 has a higher temperature during rated operation. There is no need for such a configuration. Among the plurality of power generation units 102 included in the fuel cell stack 100, the thermal expansion coefficient C of the fuel electrode side frame 140 included in the reference power generation unit which is one or a plurality of power generation units 102 is based on the temperature Tr during rated operation. If the configuration is smaller than the thermal expansion coefficient C of the fuel electrode side frame 140 included in the low-temperature power generation unit that is one or a plurality of power generation units 102 lower than the power generation unit, at least the reference power generation unit and the low-temperature power generation unit The difference in the thermal expansion amount of the fuel electrode side frame 140 due to the temperature difference during rated operation is reduced. As a result, the difference in the reduction amount of the cross-sectional area A of the second fuel gas supply communication hole 196 and the length L The difference in extension amount is reduced, and the flow rate difference of the fuel gas supplied to the power generation units 102 is suppressed.

  In the above-described embodiment, the characteristic configuration of the fuel electrode side frame 140 in which the communication flow path that connects the fuel gas introduction manifold 171 and the fuel chamber 176 is formed has been described. The present invention can be similarly applied to the air electrode side frame 130 in which a communication channel that connects the manifold 163 (the oxidizing gas introduction manifold 161 in the second and third embodiments) and the air chamber 166 is formed. For example, if the thermal expansion coefficient C of the air electrode side frame 130 is smaller for the power generation unit 102 having a higher temperature during rated operation, the thermal expansion of the air electrode side frame 130 due to the temperature difference of each power generation unit 102 during rated operation. As a result, the difference in the extension amount of the length L of the second oxidant gas supply communication hole 192 is reduced, and the difference in the flow rate of the oxidant gas supplied to each power generation unit 102 is suppressed. .

  In the above embodiment, the number of power generation units 102 included in the fuel cell stack 100 is merely an example, and the number of power generation units 102 is appropriately determined according to the output voltage required for the fuel cell stack 100 or the like.

  Moreover, in the said embodiment, the position of the heat exchange part 103 in the arrangement direction of the fuel cell stack 100 is an example to the last, and the position of the heat exchange part 103 can be changed to arbitrary positions. However, the position of the heat exchanging unit 103 is a position adjacent to the power generation unit 102 having a higher temperature among the plurality of power generation units 102 included in the fuel cell stack 100, so that the heat in the arrangement direction of the fuel cell stack 100 is determined. It is preferable for the relaxation of the distribution. For example, when the power generation unit 102 near the center in the arrangement direction of the fuel cell stack 100 is likely to be hotter, the heat exchange unit 103 is provided near the center in the arrangement direction of the fuel cell stack 100 as in the above embodiment. preferable. Further, the fuel cell stack 100 may include two or more heat exchange units 103.

  In the above embodiment, the heat exchange unit 103 is configured to increase the temperature of the oxidant gas OG. However, the heat exchange unit 103 increases the temperature of the fuel gas FG instead of the oxidant gas OG. Alternatively, the temperature of the fuel gas FG may be increased together with the oxidant gas OG.

  In the above embodiment, the end plates 104 and 106 function as output terminals. However, instead of the end plates 104 and 106, separate members (for example, the end plate 104) connected to the end plates 104 and 106, respectively. , 106 and the power generation unit 102) may function as output terminals.

  Moreover, in the said embodiment, although the space between the outer peripheral surface of the axial part of each bolt 22 and the inner peripheral surface of each communicating hole 108 is utilized as each manifold, it replaces with this and the axis | shaft of each bolt 22 is used. An axial hole may be formed in the part, and the hole may be used as each manifold. In either case, each manifold is formed by each bolt 22.

  In the above embodiment, when two power generation units 102 are arranged adjacent to each other, one interconnector 150 is shared by two adjacent power generation units 102. Two power generation units 102 may be provided with respective interconnectors 150. In the above embodiment, the upper interconnector 150 of the uppermost power generation unit 102 in the fuel cell stack 100 and the lower interconnector 150 of the lowermost power generation unit 102 are omitted. These interconnectors 150 may be provided without being omitted.

  Further, in the above embodiment, the fuel electrode side current collector 144 may have the same configuration as the air electrode side current collector 134, and the fuel electrode side current collector 144 and the adjacent interconnector 150 are an integral member. It may be. Further, the fuel electrode side frame 140 instead of the air electrode side frame 130 may be an insulator. The air electrode side frame 130 and the fuel electrode side frame 140 may have a multilayer structure.

  Moreover, the material which forms each member in the said embodiment is an illustration to the last, and each member may be formed with another material.

  In the above embodiment, the city gas is reformed to obtain the hydrogen-rich fuel gas FG, but the fuel gas FG may be obtained from other raw materials such as LP gas, kerosene, methanol, gasoline, Pure hydrogen may be used as the fuel gas FG.

  Further, in the above embodiment, a reaction preventing layer containing, for example, ceria is provided between the electrolyte layer 112 and the air electrode 114 so that zirconium or the like in the electrolyte layer 112 reacts with strontium or the like in the air electrode 114. An increase in electrical resistance between the electrolyte layer 112 and the air electrode 114 may be suppressed.

 In the above embodiment, the solid oxide fuel cell (SOFC) has been described as an example. However, the present invention can be applied to a solid polymer fuel cell (PEFC), a phosphoric acid fuel cell (PAFC), a molten carbonate type. It can be applied to other types of fuel cells such as fuel cells (MCFC). The present invention is a fuel cell of a type such as SOFC or MCFC in which the temperature during rated operation is relatively high and the amount of thermal expansion of the fuel electrode side frame 140 and the air electrode side frame 130 is relatively large. More preferred.

22: Bolt 24: Nut 26: Insulating sheet 27: Gas passage member 28: Body portion 29: Branch portion 100: Fuel cell stack 102: Power generation unit 103: Heat exchange portion 104: End plate 106: End plate 108: Communication hole 110 : Single cell 112: Electrolyte layer 114: Air electrode 116: Fuel electrode 120: Separator 121: Hole 124: Joint part 130: Air electrode side frame 131: Through hole 134: Air electrode side current collector 140: Fuel electrode side frame 141 : Through hole 144: Fuel electrode side current collector 145: Electrode facing portion 146: Interconnector facing portion 147: Connecting portion 149: Spacer 150: Interconnector 161: Oxidant gas introduction manifold 162: Oxidant gas discharge manifold 163: Oxidation Agent gas supply manifold 66: Air chamber 171: Fuel gas introduction manifold 172: Fuel gas discharge manifold 176: Fuel chamber 182: Hole 184: Communication hole 186: Communication hole 188: Heat exchange channel 191: First oxidant gas supply communication hole 192: First Oxidant gas supply communication hole 193: first oxidant gas discharge communication hole 194: second oxidant gas discharge communication hole 195: first fuel gas supply communication hole 196: second fuel gas supply communication hole 197: first fuel Gas discharge communication hole 198: Second fuel gas discharge communication hole

Claims (4)

A plurality of power generation units arranged side by side in a first direction and a plurality of bolts extending in the first direction are formed, and a plurality of gas flow paths are formed that are fastened by the bolts and extend over the plurality of power generation units. Fuel cell stack,
Each said power generation unit is
A single cell including an electrolyte layer and an air electrode and a fuel electrode facing each other in the first direction across the electrolyte layer;
A first through hole constituting one of a fuel chamber facing the fuel electrode and an air chamber facing the air electrode, a second through hole constituting the gas flow path, the fuel chamber and the air A frame member formed with at least one communication channel that communicates the one of the chambers and the gas channel,
The thermal expansion coefficient of the frame member included in the reference power generation unit that is one or more of the power generation units is such that the temperature during rated operation of the fuel cell stack is lower than that of the reference power generation unit. The fuel cell stack is characterized by being smaller than the thermal expansion coefficient of the frame member included in the low-temperature power generation unit as a unit. The fuel cell stack according to claim 1, wherein
Regarding the cross-sectional area of the cross section orthogonal to the gas flow direction of the communication flow path at normal temperature, the cross-sectional area at a specific position of each communication flow path in the reference power generation unit is the corresponding communication in the low-temperature power generation unit. A fuel cell stack, wherein the fuel cell stack is smaller than a cross-sectional area at a position corresponding to the specific position of the flow path. The fuel cell stack according to claim 1 or 2,
Regarding the length along the gas flow direction of the communication channel at normal temperature, the length of each communication channel in the reference power generation unit is longer than the length of the corresponding communication channel in the low temperature power generation unit. A fuel cell stack characterized by that. In the fuel cell stack according to any one of claims 1 to 3,
The ratio of the length along the gas flow direction of the communication flow path to the cross-sectional area of the cross section perpendicular to the gas flow direction at a specific position of the communication flow path is defined as a cross-sectional area length ratio, and each of the reference power generation units Regarding the absolute value of the difference between the cross-sectional area length ratio of the communication flow path and the cross-sectional area length ratio of each of the communication flow paths corresponding to the low-temperature power generation unit, the absolute value of the difference during rated operation is: A fuel cell stack characterized by being smaller than the absolute value of the difference at room temperature.

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