JPH09312163A - Solid electrolytic fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict the thermal stress distribution in a plane of a power generation film from being unbalanced. SOLUTION: In a flat plate shaped solid electrolytic fuel cell provided with an inter-connectors 11 and 12 spaced with each other and arranged in parallel and a protruded and recessed power generation film 13 having an air pole arranged between these inter-connectors and formed respectively at a solid electrolyte and on both face sides thereof and a fuel pole and constituted so as to flow an oxidizer 14 on an air pole side of the power generation film 13 and flow a fuel on the foregoing fuel pole side, recessed and protruded pitches of the power generation film 13 become coarse from an inlet from the oxidizer 14 or the fuel toward an exit direction.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a solid oxide fuel cell.

[0002]

2. Description of the Related Art Conventionally, a one-stage parallel flow type solid oxide fuel cell is known as shown in FIGS. Here, FIG. 2A is a cross-sectional view of the battery, and FIG. 2B is a perspective view of the battery.

Reference numerals 1 and 2 in the figure denote interconnectors which are arranged in parallel with each other. Between the interconnectors 1 and 2, there is disposed an uneven power generation membrane 3 composed of an electrolyte and an air electrode and a fuel electrode (not shown) formed on the upper and lower surfaces thereof. This power generation film 3 is
A single raw molded article that has been cast-molded, injection-molded, cold-pressed or the like may be fired to form a structure. Here, the reason why the power generation film 3 is made uneven is to increase the specific surface area for power generation. In the power generation film 3, the in-plane irregularities are regularly arranged at the same pitch P. Regarding this, for example, Mitsubishi Heavy Industries Technical Report Vol. 32 No. 1 (1995), p
35-p37. In the figure, reference numeral 4 (dashed line) indicates an oxidant (for example, air), and reference numeral 5 (dotted line) indicates a fuel (for example, hydrogen).

[0004]

By the way, when the parallel flow type fuel and the oxidizer are arranged as in the solid electrolyte fuel cell of FIG. 2, heat is generated by power generation, so that the fuel flows from the inlet to the outlet. And the temperature of the fluid (fuel and oxidant) rises. By the way, in general, the thermal stress σ _T is (σ _T is EαΔT
Proportional to) has the property. Here, E is Young's modulus, α is the coefficient of thermal expansion, and σ _T is the temperature change from the reference temperature.

Therefore, in the concavo-convex power generation film 3 having the uniform pitch P, the Young's modulus E, α has a constant coefficient of thermal expansion both near the inlet and near the outlet. As a result, for example, assuming room temperature as the reference temperature, the thermal stress σ _T1 at the inlet is
_T2 becomes large, causing an imbalance in the in-plane thermal stress distribution.

The present invention has been made in consideration of such circumstances, and by using a power generation film in which the pitch of the unevenness from the fluid inlet to the outlet is changed, the thermal stress distribution in the power generation film plane is not affected. An object of the present invention is to provide a solid oxide fuel cell which can suppress the occurrence of balance.

[0007]

DISCLOSURE OF THE INVENTION The present invention is directed to interconnectors which are spaced apart from each other and arranged in parallel, and an air electrode which is disposed between the interconnectors and is formed on both sides of the solid electrolyte and the solid electrolyte. A flat-plate type solid electrolyte fuel cell having a concavo-convex power generation membrane having a fuel electrode, wherein an oxidant is flown to the air electrode side of the power generation membrane and a fuel is flowed to the fuel electrode side. The solid electrolyte fuel cell is characterized in that the pitch of the unevenness of the film changes from the inlet of the oxidizer or the fuel toward the outlet.

Next, the operation of the present invention will be described.
In general, the thermal stress σ _T is estimated to be approximately proportional to EαΔT. Therefore, for example, as shown in FIG.
By changing ₁ , P ₂ ... from the entrance to the exit,
The thermal stress σ _T1 at the inlet and the thermal stress σ _T2 at the outlet are set to be approximately the same size, and the thermal stress distribution in the plane is smoothed. For example, if the coefficient of thermal expansion α can be considered to be uniform in spite of the uneven pitch, the uneven pitch may be provided so as to obtain the Young's modulus E such that the value of EΔT is constant.
Alternatively, if the thermal expansion coefficient α changes depending on the uneven pitch, the uneven pitch distribution that gives a combination of the Young's modulus E and the thermal expansion coefficient α such that the value of EαΔT is constant is given.

More specifically, it is considered that E (Young's modulus) depends on the pitch (or is manufactured so as to change depending on the pitch). Regarding α (coefficient of thermal expansion), the degree of pitch dependence is not well known. Therefore, assuming that α does not depend on the pitch, using the pitch dependence of E, for example, using the proportional coefficient C (constant), the thermal stress σ _T is σ _T , CE (pitch) α ΔT = D (constant value) Therefore, D (that is, σ _T ) may be set to be constant, and E = D / (CαΔT) ... α may be set to be constant with respect to the temperature increase ΔT that is a function of the place. If α is pitch dependent, it is assumed that Eα = D / (CΔT) ... α is a variable.

For example, based on the predicted or actually measured value of the temperature distribution in the plane of the power generation membrane, the temperature-dependent physical properties of the power generation membrane constituent materials are used to numerically analyze several pitches such as the homogenization method. By using the method, the correspondence between the uneven pitch and the Young's modulus E and the thermal expansion coefficient α is prepared, and conversely, the pitch that gives a set of E and α such that EαΔT is constant may be determined.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
This will be described with reference to FIG. Reference numerals 11 and 12 in the figure denote interconnectors arranged in parallel with each other. Between the interconnectors 11 and 12, an electrolyte and an air electrode and a fuel electrode (not shown) formed on the upper and lower surfaces thereof, respectively.
The uneven power generation film 13 made of is arranged. This power generation membrane 13 has a step of firing a single raw molded body to form a structure in the conventional power generation membrane forming step, but it may be formed by changing the pitch when forming the raw molded body. . In addition, the number 14 (one-dot chain line) in the figure is an oxidizing agent (for example, air).
The numeral 15 (dotted line) indicates fuel (for example, hydrogen).

The reason why the power generation film 13 is made uneven is to increase the specific surface area for power generation. In the power generation film 13, the pitch P ₁ of the irregularities in the _{plane, P 2, P 3, ...} P 10 is
It is set to become coarse from the inlet of the oxidant or the fuel toward the outlet. That is, the pitch is P ₁ <P ₂ <P ₃
<... <P ₁₀ and the size gradually increases. Here, regarding the distribution of the uneven pitch, if the distribution effect of the thermal expansion coefficient α can be ignored, the aim is that EΔT becomes constant,
Or if the distribution effect of the coefficient of thermal expansion α is important, Eα
The uneven pitch distribution that gives a combined distribution of E and α with which ΔT is constant is set.

As described above, according to the solid oxide fuel cell of the above-mentioned embodiment, the pitch P of the unevenness in the plane of the power generation membrane 13 is set.
_{1, P 2, P 3,} ... toward since P ₁₀ is a set configured to be rough toward the outlet from the inlet of the oxidant or fuel, the Young's modulus E of the power generation film 13 from the inlet to the outlet The temperature rise effect from the inlet to the outlet can be canceled, and the in-plane thermal stress σ _T can be smoothed.

In the above embodiment, the case where the pitch of the unevenness of the power generation film is set to become coarser from the inlet of the oxidizer (or the fuel) toward the outlet has been described, but the present invention is not limited to this. In other words, in the above example, the pitch is gradually increased because it is assumed that the temperature rises from the inlet to the outlet, but if there is a temperature peak at the center, for example, from the inlet to the center. The pitch changes depending on the temperature distribution, such as increasing the pitch and decreasing the pitch from the center toward the exit.

[0015]

As described above in detail, according to the present invention,
By using a power generation membrane whose pitch is changed from the inlet to the outlet of the fluid, the Young's modulus E and / or the coefficient of thermal expansion α which is uniform in the plane due to the temperature distribution Δ resulting from power generation.
Regarding the non-uniformity of in-plane thermal stress of the uneven power generation film with
It is possible to provide a solid electrolyte fuel cell in which the Young's modulus E and / or the thermal expansion coefficient α can be adjusted to smooth the in-plane thermal stress.

[Brief description of drawings]

FIG. 1 is a sectional view of a solid oxide fuel cell according to an embodiment of the present invention.

2 is an explanatory view of a conventional solid oxide fuel cell, and FIG.
2A is a cross-sectional view, and FIG. 2B is a perspective view of FIG.

[Explanation of symbols]

 11, 12 ... Interconnector, 13 ... Power generation membrane, 14 ... Oxidizer (air), 15 ... Fuel (hydrogen).

Claims (1)

[Claims] 1. An interconnector arranged in parallel and spaced apart from each other, and arranged between these interconnectors,
A solid electrolyte and an uneven power generation membrane having an air electrode and a fuel electrode respectively formed on both sides of the solid electrolyte, and flowing an oxidant to the air electrode side of the power generation membrane and to the fuel electrode side. In a flat plate type solid electrolyte fuel cell configured to flow a fuel, the pitch of the irregularities of the power generation film is changed from the inlet of the oxidizer or the fuel toward the outlet thereof.