JPH06267559A - Fuel cell - Google Patents

Abstract

PURPOSE:To obtain a fuel cell which can make even the gas flow distribution at the electromotive member of a single cell, and can improve the power generating property. CONSTITUTION:A gas flowing-in passage 2 to feed the gas to the electromotive member of a single cell, and a gas flowing-out passage 5 to exhaust the gas from the electromotive member are provided. And at least to one side of the gas flowing-in passage 2 or the gas flowing-out passage 5, flow passage resistance members 7, 8, and 9 are provided to make the pressure distribution of the gas almost even, about in the vertical direction to the gas flowing directions 6, at the gas inlet part 3 or the gas outlet part 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell for converting chemical energy into electric energy, and more particularly to a fuel cell for improving the homogenization of gas flow in its gas passage.

[0002]

2. Description of the Related Art A fuel cell is a system for directly converting Gibbs free energy of a difference between a chemical potential of a fuel and an oxidant and a chemical potential of a reactant thereof into electric energy. Then, the reaction of the fuel and the oxidant is performed by the fuel and the two electrodes of the unit cell including the electrolyte and the two electrodes sandwiching the electrolyte, respectively.
An oxidant is brought into contact with the oxidant, and the flow of ions inside the electrolyte is taken out as a current by being promoted by a battery reaction mediated by the movement of ions in the electrolyte.

However, since the voltage obtained from such a unit cell is less than 1 V at the most, a method of stacking the unit cells to increase the output voltage is adopted as the fuel cell system.

Generally, in a fuel cell power generation system, there is a tendency to increase the unit cell area and the number of stacked layers in order to increase the capacity. At present, the unit cell area is 1 m × 1.
About m, and the number of laminated layers is about tens to hundreds.

16 and 17 show an example of a conventional fuel cell in which unit cells are stacked. FIG. 16 is an exploded perspective view showing a state of stacking, and FIG. 17 is a sectional view taken in the direction of arrow A in FIG. In the fuel cell of this conventional example, it is necessary to supply gas in the stacking direction of the unit cells and in the in-plane direction of the unit cells. The manifold ring 213 is in the stacking direction and the gas of the separator 214 is in the in-plane direction of the unit cells. Gas is supplied by the flow path. FIG. 18 shows the state of gas flow in the in-plane direction of the unit cell.

Since the diameter of the manifold ring is smaller than the size of one side of the unit cell, the gas flow path 310 from the gas inflow portion 302 connected to the manifold ring of the separator gas flow path to the unit cell increases in cross-sectional area as the flow proceeds. It becomes an enlarged flow path. Generally, in such an enlarged flow path, even if a uniform flow velocity distribution is obtained in the cross-sectional direction in the inflow portion 302, it is difficult to obtain a uniform flow velocity distribution in the cross-sectional direction downstream of the enlarged portion. Therefore, the flow rate of the gas flowing into the electromotive portion inflow portion 303 of the unit cell is not uniform depending on the position on the side.

In addition, from the electromotive section of the unit cell to the gas outflow section 30
The gas flow paths 311 up to 5 are reduced flow paths whose cross-sectional area decreases with the flow. In general, in such a reduced flow passage, even if a uniform pressure is obtained in the cross-sectional direction at the outflow portion, it is difficult to obtain a uniform flow velocity distribution in the cross-sectional direction upstream of the reduced portion. In addition, the flow rate of the gas flowing out from the electromotive portion outflow portion 304 of the unit cell is not uniform depending on the position on the side.

It is known that the flow state of gas in the electromotive section of a single cell has a great influence on the cell performance.
In the gas inflow portion of the unit cell, where the gas flow rate is smaller than that of the other portion, sufficient current cannot be taken out downstream thereof, and the unit cell cannot be sufficiently cooled by the gas. Therefore, the distribution of the current density or the distribution of the temperature in the plane of the unit cell becomes large, resulting in the deterioration of the performance of the fuel cell.

Further, in the gas outflow portion of the unit cell, where the gas flow rate is smaller than that of the other area, the gas flow rate upstream thereof decreases, so that sufficient current cannot be taken out.
In addition, because it is not possible to sufficiently cool the unit cell with gas,
As a result, the performance of the fuel cell is degraded. Further, the increase of the current density distribution or the temperature distribution in the plane of the unit cell adversely affects the life of the fuel cell.

[0010]

As described above, in the conventional fuel cell, there is a problem that the performance of the fuel cell deteriorates due to the nonuniform gas flow rate in the cell electromotive section. . The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel cell capable of improving the power generation performance by equalizing the gas flow rate in the unit cell electromotive section.

[0011]

In order to solve the above-mentioned problems, a fuel cell according to a first aspect of the present invention comprises a gas inflow path for supplying gas to an electromotive section of a unit cell, and the electromotive section. A gas outflow passage for discharging gas from the at least one of the gas inflow passage or the gas outflow passage, at a gas inlet portion or an outlet portion of the electromotive section with respect to the flow direction of the gas. The channel resistance is set so that the pressure distribution of the gas is substantially uniform in the vertical direction.

Further, the fuel cell of the second invention comprises a gas flow path for supplying gas to the electromotive part of the unit cell and discharging the gas through the electromotive part, and the gas flow in the electromotive part A flow path resistance is set in the passage so that the pressure distribution of the gas is substantially uniform in a direction substantially perpendicular to the flow direction of the gas.

[0013]

In the fuel cell according to the first aspect of the present invention thus configured, at least one of the gas inflow path (gas inflow section) and the gas outflow path (gas outflow section) has a gas inlet section of the electromotive section. Alternatively, the flow passage resistance is set so as to make the pressure distribution of the gas substantially uniform in the direction substantially perpendicular to the flow direction of the gas at the outlet portion (the flow passage resistance member is provided), so that the enlarged flow passage is formed. The flow rate of the gas flow flowing through is substantially uniform in any cross section, and the flow rate of gas flowing into or out of the unit cell electromotive section is substantially uniform.

As a result, the flow rate of the gas flowing through the unit cell electromotive portion is made substantially uniform at any of the portions, and high performance can be maintained without causing deterioration in fuel cell performance due to uneven flow rate.

Further, in the fuel cell of the second invention,
The flow path resistance was set in the gas flow path in the electromotive section so that the pressure distribution of the gas was substantially uniform in a direction substantially perpendicular to the gas flow direction (a flow path resistance member was provided).
As a result, the flow rate of the gas flowing through the unit cell electromotive section is made substantially uniform at any part, and high performance can be maintained without causing deterioration in fuel cell performance due to non-uniform flow rate.

[0016]

An embodiment of the fuel cell of the present invention will be described below with reference to the drawings. [First Invention] First, first to fourth aspects of the invention are described.
Embodiments and modified examples will be described with reference to FIGS. 1 to 14. (First Embodiment) FIG. 1 is a perspective view showing a schematic configuration of a separator relating to a fuel cell of a first embodiment of the first invention, and FIG. 2 shows a state in which unit cells are stacked using this separator. It is sectional drawing for showing.

In the fuel cell having the structure according to the first embodiment, the gas supplied through the manifold (not shown) is distributed and supplied to each separator 1 through the manifold ring 25 as shown by an arrow 6 in the figure. . Then, the gas supplied to the separator 1 flows through the gas flow path in each separator 1 to the electrode 23 forming the unit cell 27, the gas inflow part 2, the electromotive part inflow part 3, the electromotive part, the electromotive part. The gas is supplied and discharged by flowing in the order of the outflow portion 4 and the gas outflow portion 5.
Here, since the diameter of the manifold ring 25 is set to be considerably smaller than the length of one side of the unit cell 27, the gas flow path 10 from the gas inflow portion 2 to the electromotive portion inflow portion 3 flows. Accordingly, the flow passage becomes an enlarged flow passage whose cross-sectional area gradually increases.

In the fuel cell according to the first embodiment of the first aspect of the invention, trapezoidal fin groups 7, 8 and 9 are arranged in the gas flow passage 10 as an example of the flow passage resistance member. Here, more specifically, the trapezoidal fin groups 7, 8 and 9 are configured as shown in FIG. That is, a large number of plate-shaped trapezoidal fins 31 are arranged in a substantially zigzag manner, and the gas is configured to flow inside the trapezoidal fins 31 and between them.

According to the experiments conducted by the present inventor, in such a trapezoidal fin 31, the flow path resistance differs depending on the gas flow direction relative to the arrangement direction, and the gas flow direction angle θ shown in FIG. 3 is 0. When the angle is 60 degrees, the friction coefficient, that is, the flow path resistance is the smallest, and when the angle θ is 60 degrees, the flow path resistance is the largest. Note that FIG. 4 shows the Reynolds number on the horizontal axis and the friction coefficient on the vertical axis, and shows the experimental data by the inventor for each of the angles θ of 0, 30, 45, 60, and 90 degrees. It is a thing.

It can be understood from FIG. 4 that, in the trapezoidal fin 31, the difference in flow path resistance can be greatly changed to about three times when the gas flow direction angle θ is 0 ° and 60 °. That's what it means.

Next, FIG. 5 is a view showing the arrangement of the trapezoidal fin groups 7, 8, 9 respectively. In the gas flow path 10 from the gas inflow portion 2 to the electromotive portion inflow portion 3, arrows in the figure are shown. In the cross section in the direction substantially perpendicular to the gas flow direction shown by 6,
A portion where the trapezoidal fins are arranged and a portion where the trapezoidal fins are not arranged are formed. Further, the angle of the trapezoidal fin array with respect to the direction of the gas flow indicated by the arrow 6 is 0 degrees for the trapezoidal fin group 7, 60 degrees for the trapezoidal fin group 8, and 0 degrees for the trapezoidal fin group 9. The trapezoidal fin group 8 has the largest flow resistance with respect to
Next, the trapezoidal fin groups 7 and 9 and the portion without the trapezoidal fins are the smallest.

The trapezoidal fin group 7 as described above,
Each of the arrangements 8 and 9 is arranged so that the gas pressure is substantially constant at the electromotive portion inlet. As described above, in the present embodiment, the flow path resistance is changed so that the gas pressure becomes substantially constant at the electromotive portion inlet in the direction substantially perpendicular to the gas flow direction indicated by the arrow 6. FIG. 6 shows a result of simulating the state of gas flow in the gas channel 10 using a general-purpose fluid analysis code. For comparison, FIG. 7 shows a simulation result of a conventional example in which the trapezoidal fin groups 7, 8 and 9 are not arranged and the flow path resistance is not changed.

Both figures show isobars in the gas flow path. In the region where the cross-sectional area of the flow path does not change, the isobars are arranged substantially parallel to each other. It shows that there are few. In the case of FIG. 7 of the conventional example in which the flow path resistance is not changed, the isobar 71 near the inflow part of the electromotive part is not parallel to the isobar 72 of the electromotive part, and the gas flow rate at the inflow part of the electromotive part is not increased. It has a distribution in. On the other hand, as shown in FIG. 6, in the case of the present embodiment in which the flow path resistance is changed so that the gas pressure is substantially constant at the electromotive section inlet in the direction substantially perpendicular to the gas flow direction. Surely, the isobar 61 near the inflow part of the electromotive part is almost parallel to the isobar 62 of the electromotive part,
The distribution of the gas flow rate is small in the electromotive part inflow part, and the effect of providing the trapezoidal fin group can be clearly understood.

Further, the difference between the first embodiment and the conventional example is shown by the drift rate defined by normalizing the standard deviation of the flow velocity distribution by the square root of the root mean square in the cross section of the inflow section of the electromotive section. While it is 25%, in this embodiment, it is 5.8%, and the flow rate distribution is suppressed to about 1/5.
From this fact, it is clear that the present invention is extremely effective in making the flow rate distribution uniform. (Second Embodiment) FIG. 8 is a layout view of a trapezoidal fin group arranged in a separator portion according to a second embodiment of the fuel cell of the first invention.

In the second embodiment, the trapezoidal fin group 87,
88 and 89 are respectively arranged in the reduced flow path 80 between the electromotive part outflow part 4 and the outflow part 5. These trapezoidal fin groups 8
Reference numerals 7, 88 and 89 are functionally equivalent to the trapezoidal fin groups 7, 8 and 9 shown in the first embodiment, and are trapezoidal fins in a cross section substantially perpendicular to the gas flow direction. And a portion where the trapezoidal fins are not arranged are formed. The angle of the trapezoidal fin array with respect to the gas flow direction is 0 degrees in the trapezoidal fin group 87,
60 degrees for the trapezoidal fin group 88, 0 for the trapezoidal fin group 89
The trapezoidal fin group 88 has the largest flow path resistance to the gas flow, the trapezoidal fin groups 87 and 89, and the portion without the trapezoidal fin have the smallest flow path resistance.

Then, the trapezoidal fin group 87 as described above,
The respective 88 and 89 are arranged so that the gas pressure is substantially constant at the electromotive portion outlet 4. Therefore, by arranging the trapezoidal fin groups 87, 88, 89 in this manner, the gas flow rate upstream of the electromotive portion outflow portion 4 is made uniform. (Third Embodiment) FIG. 9 is a layout view of a trapezoidal fin group arranged in a separator portion according to a third embodiment of the fuel cell of the first invention.

The structure of the third embodiment corresponds to a combination of the first and second embodiments described above, in which the trapezoidal fin groups 7, 8 and 9 are connected to the inflow part 2 and the electromotive part. The trapezoidal fin groups 87, 88, 8 are arranged in the enlarged flow path 10 between the inflow section 3 and
Reference numeral 9 denotes a reduced flow passage 80 between the electromotive portion outflow portion 4 and the outflow portion 5.
It is arranged in each. By arranging such trapezoidal fin groups, the gas flow rates in the downstream of the electromotive portion inflow portion 3 and the upstream of the electromotive portion outflow portion 4 are made uniform, and as a result, the gas flow rates are made uniform in the entire electromotive portion. It

FIG. 10 shows an isobaric diagram as a result of simulating the state of the flow in the gas passage using the general-purpose fluid analysis code for the configuration of the third embodiment. Both the isobars 101 near the electromotive part inflow part and the isobars 103 at the electromotive part outflow part are almost parallel to the isobar line 102 of the electromotive part, and the gas flow rate is provided at the electromotive part inflow part and the electromotive part outflow part. It can be seen that the distribution of is small. Further, when the difference between the third embodiment and the conventional example is shown by the above-mentioned drift ratio, 25% in the conventional example, 4.6% in the electromotive portion inflow portion in the third embodiment, The flow rate distribution is suppressed to about 1/5 to 1/3 in the entire electromotive section, being 8.6% at the outflow section. (Fourth Embodiment) FIG. 11 shows a fourth embodiment of the fuel cell of the first invention.
FIG. 5 is a layout view of a trapezoidal fin group arranged in a separator portion according to an example.

In the configuration of the fourth embodiment, the trapezoidal fin group 11
Reference numeral 7 denotes an enlarged flow path 11 between the inflow part 2 and the electromotive part inflow part 3.
It is placed at 0. In the first to third embodiments, the trapezoidal fin group is divided into three in a direction substantially perpendicular to the gas flow direction, whereas in the fourth embodiment, the trapezoidal fin group 117 is configured so as not to be divided. Are arranged.

The angles of the trapezoidal fin group 117 array with respect to the gas flow direction indicated by arrows 111, 112, and 113 in the figure are about 0 °, 45 °, and 90 °, respectively, and the trapezoidal fin group is divided and arranged as described above. The angular arrangement is substantially the same as in the first to third embodiments. Therefore, the distribution of the flow path resistance in the direction perpendicular to the flow is almost the same as in the case of the first embodiment, so that the gas flow rate in the electromotive part inflow part can be made uniform.

In the fourth embodiment, the trapezoidal fin group 117 is arranged between the inflow part 2 and the electromotive part inflow part 3, but the electromotive part outflow is carried out similarly to the second embodiment. A trapezoid is formed between the part 4 and the outflow part 5, or both between the inflow part 2 and the electromotive part inflow part 3 and between the electromotive part outflow part 4 and the outflow part 5 as in the third embodiment. The fin group may be arranged as in the above-described embodiment. (Additional Effects of First to Fourth Embodiments) In any of the above first to fourth embodiments, the trapezoidal fins arranged in the gas flow passage enhance the rigidity of the gas flow passage and It is also effective to keep the height dimension accurately. Further, the trapezoidal fin is used as a catalyst carrier, and the reforming catalyst for reforming the raw material gas into the fuel gas is held by the trapezoidal fin arranged between the gas inflow portion 2 and the electromotive portion inflow portion 3 to generate electromotive force. The operation and effect of the direct internal reforming fuel cell that can use the completely reformed fuel gas in the partial inflow portion 3 are various. (Modification) Further, in each of the above embodiments, the angle of the trapezoidal fin with respect to the gas flow is changed in order to change the flow path resistance. However, as a method of changing the flow path resistance, However, the present invention is not limited to the above embodiment.

For example, as shown in FIG. 12, a plurality of columnar projections 130 as another example of the flow path resistance member are arranged in the flow path, and the arrangement density (the number or size of the projections per unit area, Alternatively, the same action and effect can be obtained by changing the shape). Further, the shape of the columnar protrusion is not limited to the columnar protrusion 130 shown in FIG. 12, and a prismatic column or other shapes can be applied.

Alternatively, as shown in FIG. 13, first to fourth
Even if a semi-rectangular fin 131 or a semi-cylindrical fin 132 as shown in FIG. 14 is arranged as the flow path resistance member instead of the trapezoidal fin shown in the embodiment, the same action and effect can be obtained. The shape of the fins can be modified in various ways without departing from the scope of the present invention.

Alternatively, although not shown, the flow path resistance can be changed by a method of disposing a felt-like member in a part of the flow path. As an example of this felt-like member, a material having excellent corrosion resistance in a high temperature environment, for example, Ni fibers formed in a felt shape can be applied. It is obvious that various materials can be applied to the felt-shaped member.

Furthermore, in the first to third embodiments, the trapezoidal fin group is arranged in three divisions with respect to the gas flow direction, but the invention is not limited to three divisions, and the electromotive section inlet or the flow section is not limited. The form of division is not limited as long as the gas pressure is arranged to be substantially constant at the outlet. [Second Invention] FIG. 15 is a layout view of trapezoidal fins showing an embodiment of the second invention. Members corresponding to the trapezoidal fins 31 shown in FIG. 3 are provided as current collector plates 209 and 210 in the gas flow path of the electromotive section of the conventional fuel cell shown in FIG. Also for the current collector plate, since the flow path resistance differs depending on the angle between the trapezoidal fin array and the gas flow direction, generally, the flow path resistance is 0 degree with respect to the gas flow so that the flow path resistance is the smallest in the entire electromotive section. Is used.

In the second aspect of the invention, the arrangement corresponding to the trapezoidal fin group as the flow path resistance member is set so as to form an angle of approximately 60 degrees with respect to the gas flow downstream of the electromotive portion inflow portion 3. Of the current collector plate 124a and a second region of the current collector plate 124b set to form an angle of 0 degree with respect to the gas flow.
24 make up.

That is, the flow path resistance is increased in a part of the area downstream of the electromotive part inflow part 3 compared to other areas. With this configuration, the flow path resistance is set so that the flow rate distribution in the electromotive portion inflow portion 3 becomes substantially uniform in the direction substantially perpendicular to the gas flow direction indicated by the arrow 123 in the figure. . Note that, here, the arrangement of members corresponding to the trapezoidal fins is changed in the region of the current collector plate 124a at a part of the downstream side of the electromotive portion inflow portion 3, but the present invention is not limited to this.

That is, upstream of the electromotive portion outflow portion 4 so as to correspond to the second embodiment of the first invention, or downstream of the electromotive portion inflow portion 3 so as to correspond to the third embodiment. May be provided both upstream and upstream of the electromotive section outflow section 4, and in other parts, and further in these plural parts,
The arrangement of the resistance members formed on the collector plate 124 may be changed so as to obtain a uniform gas flow rate distribution.

[0039]

As described in detail above, according to the present invention,
The flow rate of the gas flowing through the electromotive section of the unit cell is substantially uniformed at any portion, and high performance can be maintained without causing performance deterioration of the fuel cell due to uneven flow rate.

[Brief description of drawings]

FIG. 1 is a perspective view showing a separator according to a first embodiment of the first invention.

FIG. 2 is a sectional view showing a fuel cell according to a first embodiment of the first invention.

FIG. 3 is an enlarged perspective view of an essential part showing a trapezoidal fin according to the first embodiment of the first invention in an enlarged manner.

FIG. 4 is a characteristic diagram showing characteristics of flow path resistance of the trapezoidal fin according to the first embodiment of the first invention.

FIG. 5 is a layout diagram showing a layout of trapezoidal fins according to the first embodiment of the first invention.

FIG. 6 is an isobaric diagram showing a gas flow in a gas channel according to the first embodiment of the first invention.

FIG. 7 is an isobar diagram showing the flow of gas in a gas channel according to a conventional example.

FIG. 8 is a layout drawing showing a layout of trapezoidal fins according to a second embodiment of the first invention.

FIG. 9 is a layout diagram showing a layout of trapezoidal fins according to a third embodiment of the first invention.

FIG. 10 is an isobar diagram showing a gas flow in a gas passage according to a third embodiment of the first invention.

FIG. 11 is a layout view showing a layout of trapezoidal fins according to a fourth embodiment of the first invention.

FIG. 12 is a layout view showing a layout of flow path resistance members according to a modification of the first invention.

FIG. 13 is a layout diagram showing a layout of flow path resistance members according to a modification of the first invention.

FIG. 14 is a layout diagram showing a layout of flow path resistance members according to a modification of the first invention.

FIG. 15 is a layout view showing a layout of flow path resistance members according to a second invention.

FIG. 16 is an exploded perspective view showing a conventional fuel cell.

FIG. 17 is a sectional view showing a conventional fuel cell.

FIG. 18 is a perspective view showing a separator of a conventional fuel cell.

[Explanation of symbols]

 2 gas inflow part (gas inflow path) 3 electromotive part inflow part (gas inlet part of electromotive part) 4 electromotive part outflow part (gas outlet part of electromotive part) 5 gas outflow part (gas outflow path) 6 gas 7 Trapezoidal fin group (flow path resistance member) 8 Trapezoidal fin group (flow path resistance member) 9 Trapezoidal fin group (flow path resistance member) 10 Gas flow path 11 Gas flow direction 21 Spring 22 Electrolyte matrix 23 Cathode 24 Cathode current collector plate 26 Anode 28 Anode current collector plate 31 Trapezoidal fin (flow path resistance member) 87 Trapezoidal fin group (flow path resistance member) 88 Trapezoidal fin group (flow path resistance member) 89 Trapezoidal fin group (flow path resistance member) 117 Trapezoidal fin group (flow path resistance member) 124 Current collector 130 Protrusion (flow path resistance member) 131 Semi-rectangular fin (flow path resistance member) 132 Semi-cylindrical fin (flow path resistance member)

Claims (3)

[Claims] 1. A gas inflow path for supplying gas to an electromotive section of a unit cell, and a gas outflow path for discharging gas from the electromotive section. A flow path resistance is set in at least one of the outflow passages so that the pressure distribution of the gas is substantially uniform in a gas inlet portion or an outlet portion of the electromotive section in a direction substantially perpendicular to the gas flow direction. Is a fuel cell. 2. A gas flow path for supplying gas to an electromotive part of a unit cell and discharging the gas through the electromotive part, wherein the gas flow path in the electromotive part is arranged in a flow direction of the gas. On the other hand, the fuel cell is characterized in that the flow path resistance is set so that the pressure distribution of the gas is substantially uniform in the substantially vertical direction. 3. A flow path resistance member is set in at least one of the gas inflow path, the gas outflow path, and the gas flow path in the electromotive section. The fuel cell according to claim 1 or 2, wherein the fuel cell is set by disposing.