KR100952451B1 - Passive type fuel cell with pulsator - Google Patents

Abstract

PURPOSE: A passive type fuel battery is provided to improve the power of a fuel cell by facilitating air flow and diffusion within the fuel cell using pure reciprocation flow. CONSTITUTION: A passive type fuel battery(100) comprises a membrane-electrode assembly(4) containing an electrolyte membrane in which an anode and a cathode are equipped at both sides; and blocking plates(8a,8b) which faces the cathode and has an air channel(7) so that the cathode are exposed to the air. The blocking plates have a reciprocation flow unit(30) for reciprocating the air which naturally flows.

Description

Passive fuel cell with reciprocating means {Passive type fuel cell with pulsator}

The present invention relates to a passive fuel cell that is not provided with an air supply means for forcibly supplying air. More particularly, the passive fuel cell may improve the performance of a fuel cell by promoting an inflow and diffusion amount of naturally introduced air. It relates to a type fuel cell.

A fuel cell is a power generation system that directly converts chemical reaction energy of hydrogen and oxidant contained in hydrocarbon-based materials such as methanol, ethanol and natural gas into electrical energy.

Such fuel cell systems can be classified into various types according to the type of electrolyte used. Representatively, a polymer electrolyte fuel cell (PEMFC) system and a direct methanol fuel cell (Direct Methanol Fuel Cell: hereinafter referred to as "DMFC").

The PEMFC system or DMFC system has a membrane electrode assembly (MEA) having a conductive polymer membrane having selective hydrogen ion permeability between the anode electrode and the cathode electrode, and the anode electrode and the cathode electrode have a gas diffusion layer for supplying and diffusing fuel. And a catalyst layer or the like in which an electrode reaction, that is, an oxidation / reduction reaction occurs.

On the other hand, the supply of fuel or air required for reaction in the stack during operation of the fuel cell system has a significant effect on the stack performance. In particular, since the fraction of oxygen in the air is only about 21%, supplying the oxygen necessary for driving the fuel cell properly will be a necessary condition for obtaining the optimum performance of the fuel cell.

In the PEMFC system or DMFC system, depending on whether air is forcibly supplied, it may be classified into an active type and a passive type. An air supply means such as a blower or a fan used in an active fuel cell may be used. Basically, the power consumption is large, especially in the case of blowers, which occupy a large volume, so the size of the fuel cell system is inevitably increased.

In recent years, small fuel cell systems have been developed that are portable and can be applied to mobile devices such as laptops and mobile communication devices. This includes air in the fuel cell stack due to natural convection of air to the cathode electrode exposed to the atmosphere. Passive fuel cell systems for supplying the P are mainly used. However, in the passive fuel cell system, the amount of air supplied to the cathode electrode side is not smooth, and thus the output of the fuel cell system is not stable, and there is a problem in that the discharge of generated water is not smooth.

The problem to be solved by the present invention is to provide a passive fuel cell that can improve the output of the fuel cell by promoting the flow and diffusion of air using pure reciprocating flow.

In order to achieve the above object,

Passive fuel cells that generate electrical energy through electrical reaction with fuel supplied to the anode electrode of the membrane electrode assembly having a cathode electrode and an anode electrode respectively formed on both sides of the electrolyte membrane and supplied to the anode electrode To

The air flow inlet of the naturally introduced air is provided with a passive fuel cell, characterized in that the reciprocating flow means for reciprocating the flow of natural inlet air is provided.

According to another aspect of the present invention,

A passive fuel cell comprising a membrane electrode assembly including an electrolyte membrane having an anode electrode and a cathode electrode disposed on both sides thereof, and a cathode plate disposed to face the cathode electrode and having an air passage penetrating so that the cathode electrode is exposed to the atmosphere. To

The blocking plate is provided with a passive fuel cell, characterized in that the reciprocating flow means for reciprocating the air flowing into the air flow path side.

Here, the reciprocating flow means is preferably configured to adjust at least one or more of the reciprocating flow frequency and reciprocating flow distance.

In addition, the reciprocating flow means may include a vibrating plate mounted on the blocking plate and an exciter having the diaphragm through an elastic support member.

In addition, the diaphragm preferably includes a plurality of protrusions protruding in the cathode electrode direction.

In addition, the diaphragm may further include an air guide member bent toward the cathode electrode along part or all of the circumference thereof.

In addition, the exciter is preferably a vibration motor.

Passive fuel cell system according to the present invention can further improve the performance of the fuel cell by providing a reciprocating flow means on the side of the natural air flow path. In addition, by varying the frequency and the reciprocating flow distance of the reciprocating flow means it is possible to further increase the diffusion amount of air flowing into the fuel cell reaction. Furthermore, such a reciprocating flow means can be applied to a miniaturized fuel cell system because not only the miniaturization can be realized through the diaphragm and the vibration motor but also the parasitic power can be lowered.

Hereinafter, the present invention will be described in more detail with reference to preferred examples. However, these examples are intended to illustrate the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited thereby.

1 is an overall schematic diagram of an experimental apparatus for examining the effect of increasing the diffusion according to reciprocating flow in a passive fuel cell according to an embodiment of the present invention, Figure 2 is a separator and membrane of the fuel cell used in FIG. An exploded view of an electrode assembly.

1 and 2, a passive fuel cell according to an embodiment of the present invention includes an electrolyte membrane 1 and a cathode electrode 2 and an anode electrode 3 formed on both sides of the electrolyte membrane, respectively. A membrane electrode assembly 4, a pair of separation plates 5a and 5b disposed on both sides of the membrane electrode assembly, and a pair of blocking plates 8a and 8b respectively disposed on both sides of the pair of separation plates. These are coupled to each other by the fastener 12 to constitute the unit cell 10. In addition, both sides of the unit cell 10 are provided with a fuel supply unit 9a and a fuel discharge unit 9b for supplying and discharging fuel. Here, the description will be focused on a PEMFC that generates electric energy by using hydrogen as a fuel. However, the fuel cell according to the present invention can also be applied to DMFC which generates electric energy using methanol or ethanol as a direct fuel.

In the present embodiment, the unit cell is configured for the purpose of measuring the performance of the fuel cell, but a plurality of such unit cells may be applied to a fuel cell that is stacked and formed in order.

As shown in FIG. 2, the separator 5a disposed on the surface in contact with the cathode electrode 2 has an air passage 6 formed therein from the top to the bottom thereof. Therefore, by the air flow path formed as described above, air is supplied to the unit cell in which the membrane electrode assembly and the separator plate are coupled to each other through the air flow passage 6 formed from the top to the bottom. In addition, the separator 5b disposed on the surface in contact with the anode electrode 3 has a fuel flow path (not shown) formed in a zigzag-shaped serpentine therein.

On the other hand, the fuel supply hole 13a and the fuel discharge hole 13b and the fastening hole 14 for fastening the fuel cell are formed in both side parts of the separating plates 5a and 5b.

The membrane electrode assembly 4 is formed by stacking an electrolyte membrane 1 between the anode electrode 3 and the cathode electrode 2. The anode electrode 3 and the cathode electrode 2 include a gas diffusion layer for supplying and diffusing fuel, a catalyst layer in which an oxidation / reduction reaction of the fuel occurs, and an electrode support. The anode electrode 3 separates electrons and hydrogen ions from the fuel to be supplied, and the electrolyte membrane 1 moves hydrogen ions to the cathode electrode 2. The cathode electrode 2 generates water by reacting hydrogen and oxygen with electrons supplied from the anode electrode 3. Therefore, the unit cell generates electrical energy through an electrochemical reaction between hydrogen and oxygen.

Diffusion effect due to reciprocating flow

In the experimental apparatus shown in FIG. 1, fuel was used as hydrogen, and fuel was supplied using a mass flow meter. The fuel supplied was a wet bulb temperature controlled using a bubbler type humidifier, and a dry bulb temperature was controlled using a line heater.

In order to realize the reciprocating flow of air naturally introduced into the unit cell, one end of the air manifold 11 is connected to the inlet side air passage, and the other end is connected to the reciprocating flow means 20.

The reciprocating flow means 20 includes a cylinder 21, a piston 22 for linear reciprocating movement in the cylinder, a connecting rod 23 connected to one end of the piston and a disk 24 on which the other end rotates, and a disk ( 24 was configured as an electric motor 25 to rotate.

The aforementioned reciprocating flow means 20 is a means for reciprocating the air A inside the cylinder by linearly reciprocating the piston 22 inside the cylinder 21 through the rotational force of the motor. The reciprocating fluid may flow into the unit cell 10.

The reciprocating flow means 20 changed the angular velocity (frequency) using a motor controller (not shown) to change the reciprocating flow factor, and adjusted the reciprocating flow distance (amplitude) using the disk 24. Since the piston 22 linearly reciprocates while being completely enclosed in the cylinder 21, the air A inside the cylinder 21 may be introduced into the unit cell 10 while being reciprocated by the piston. .

The active area of the unit cell used in this experiment was 61.3 cm ² and the electrolyte membrane was Dupont's Nafion 112 membrane. Carbon paper was used for the gas diffusion layer of the cathode and anode, and the amount of catalyst was 0.4mg / cm ² for the cathode and anode, respectively.

In addition, the channel shape of the cathode is a parallel type formed with 27 air passages from the top to the bottom, the channel width is 2mm, the channel depth is 2.5mm, the channel length is 78.8mm. On the other hand, the channel shape of the anode is a serpentine in which one channel is zigzag-long and has a channel width of 1.3 mm, a channel depth of 0.8 mm, and a channel length of 2114.2 mm.

The temperature of the unit cell stack was controlled by mounting a heater on the blocking plate, and each experiment was performed when the temperature was in a certain temperature range during operation. Experimental temperature range was measured between 30 ~ 40 ℃.

Reciprocating flow test results

Changing the air flow rate means that the total flux of the air changes. In areas where convection is dominant, this change in flow will affect the change in total flux. In areas where diffusion is dominant, the increase or decrease in the amount of diffusion affects the change in the total flux. In this experiment, the reciprocating flow was applied to increase the diffusion of the naturally introduced air, and the effects of the diffusion increase effect by the reciprocating flow on the fuel cell performance were examined.

Figure 3 is a graph showing the experimental results when the angular velocity is 57.2 ~ 742.3rpm when the reciprocating flow distance is 0.0595m. 3, the in 57.2rpm 28.9mW / cm ^2, in 742.3rpm could be obtained an output of 100.0mW / cm ^2. That is, it can be seen that increasing the frequency at a constant reciprocating flow distance improves the performance of the fuel cell.

In addition to the frequency, the reciprocating flow distance, in addition to the frequency, is an important variable in the variation of the diffusion amount. Reciprocating flow increases the amount of diffusion in the stack's channels, which makes the fuel cell stack even better.

4 is a graph showing the performance change of the fuel cell according to the reciprocating flow distance change. The experiment was carried out while changing the reciprocating flow distance to 0.0116m (angular velocity 270.1rpm), 0.0298m (angular velocity 302.5rpm), and 0.0595m (angular velocity 267.4rpm). As shown in FIG. 4, it can be seen that the output of the stack increases as the reciprocating flow distance increases.

Theoretical interpretation of the experiment

Round-trip flow promotes diffusion by many physical factors besides frequency. The theoretical interpretation of the diffusion enhancement effect can be expressed as follows.

Where R is the diffusion increase amount, D _e is the effective diffusion coefficient, and D is the diffusion coefficient. The diffusion increase R can be defined as follows according to Wontson:

Here, the function fs is a value depending on the shape of the flow channel and the Womersly number (α) and Schmidt number (Sc) defined by the following equation, and V / (Ad) is a dimensionless number indicating the magnitude of the reciprocating flow ( V is the volume of fluid reciprocating, A is the cross-sectional area of the channel, and d is the diameter of the channel). Womersly number α is defined as follows.

Where ν = μ / ρ (ν is kinetic viscosity, μ is viscosity, ρ is density).

As can be seen from the above equation, once the shape of the channel and the material flowing through the channel are determined, the diffusion increase amount R depends on the Womersly number and V / (Ad). That is, there are two main dimensionless numbers that increase the spread in the channel, both of which are the Womersly number associated with the frequency and the V / (Ad) which represents the reciprocating flow size.

Therefore, the increase in diffusion in the reciprocating flow can be improved by increasing the frequency and the reciprocating flow size (or reciprocating flow distance).

Application to Passive Fuel Cells

The above experimental results can be applied to the passive fuel cell in which the cathode electrode is exposed to the atmosphere. That is, by applying the above-mentioned reciprocating flow means to a small passive fuel cell that can be used in a mobile device or the like, it is possible to solve the problem of the conventional fuel cell in which the output of the fuel cell is unstable.

FIG. 5 is a schematic diagram of a passive fuel cell 100 according to the present invention in which a reciprocating flow means 30 is provided in a so-called planar type passive fuel cell in which a cathode electrode is exposed to the atmosphere. 6 is a side view thereof.

5 and 6, the passive fuel cell 100 includes a membrane electrode assembly 4 having an anode electrode 3 and a cathode electrode 2 formed on both sides of an electrolyte membrane 1, and a contacting anode electrode. The board | substrate 5b and a pair of blocking plates 8a and 8b which fix and fix these are comprised. The air passage 7 is formed through the blocking plate 8a positioned on the cathode electrode side, and the cathode electrode 2 is exposed to the atmosphere.

Air flows naturally into the cathode electrode through the air passage 7, and an electrochemical reaction is performed with hydrogen to generate electrical energy.

Although the air flow path 7 shown in FIG. 5 is formed in a quadrangle, the size, shape, and number of the air flow paths 7 are not limited thereto, and may be appropriately changed by those skilled in the art. Of course.

The reciprocating flow means 30 according to the present invention may be provided in the blocking plate 8a in which the air flow path 7 into which air naturally flows is formed. The reciprocating flow means 30 serves to promote the diffusion in the fuel cell by reciprocating the air introduced as described above.

The reciprocating flow means 30 includes a diaphragm 31 and an exciter 32 for exciting the diaphragm. The reciprocating flow means 30 is not limited to the above-described apparatus as long as it can be configured to reciprocate the naturally introduced air.

The diaphragm 31 is attached to the blocking plate 8a by the elastic support member 33. The diaphragm 31 is a plate-like member that causes vibration in the direction of the arrow (shown in FIG. 6) by the input of the exciter 32. The diaphragm 31 may have various shapes, such as a circle and a rectangle. The diaphragm 31 can change the reciprocating flow distance by the same excitation input due to the rigidity of the elastic support member 33. That is, by reducing the rigidity of the elastic support member 33, the reciprocating flow distance can be increased under the same excitation input.

The exciter 32 for applying an input to the diaphragm may be, for example, a vibration motor. The vibration motor may be a coin-type vibration motor generating vibration output to a mobile device such as a mobile phone or an eccentric vibration motor generating vibration by attaching an eccentric to one end of the vibration motor. The reciprocating flow frequency of the reciprocating means 30 can be adjusted by varying the rotational speed of the vibration motor used as the exciter 32.

In this way, by using the vibrator 32 having the diaphragm 31 supported by the elastic support member 33, the diffusion performance of the naturally introduced air through the air passage 7 in the fuel cell can be improved. Can be.

In order to improve diffusion performance due to the reciprocating movement of the diaphragm in the vertical direction, a plurality of protrusions 35 may be formed on the surface of the diaphragm. That is, the protrusion 35 is formed to protrude in the direction of the cathode electrode 2, and the protrusion 35 not only increases the amount of air flowing into the air passage 7 but also the diaphragm 31 and the blocking plate 8a. The fuel cell performance can be improved by further promoting the reciprocating flow of air existing between

In addition, the diaphragm may further include an air guide member 34 bent in the direction of the cathode electrode along the circumference thereof. The air guide member 34 can increase the volume of the reciprocating air by increasing the volume of air reciprocating by sealing the air located between the diaphragm 31 and the blocking plate 8a.

All simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

1 is an overall schematic diagram of an experimental apparatus for examining the effect of increasing the diffusion according to the reciprocating flow.

FIG. 2 is an exploded view of a separator and a membrane electrode assembly of the fuel cell used in FIG. 1.

3 and 4 are graphs illustrating the performance of a fuel cell equipped with a reciprocating flow means.

5 is a schematic view of a passive fuel cell according to one embodiment of the invention with reciprocating flow means.

6 is a schematic side view of a passive fuel cell according to an embodiment of the present invention.

Claims (7)

delete A passive fuel cell comprising a membrane electrode assembly including an electrolyte membrane having an anode electrode and a cathode electrode disposed on both sides thereof, and a cathode plate disposed to face the cathode electrode and having an air passage penetrating so that the cathode electrode is exposed to the atmosphere. To The blocking plate is provided with a reciprocating flow means for reciprocating the air flowing into the air flow path side, The reciprocating flow means includes a diaphragm having an oscillating plate and the diaphragm mounted on the blocking plate via an elastic support member. The method of claim 2, The reciprocating flow means is a passive fuel cell, characterized in that configured to adjust at least one or more of the reciprocating flow frequency and reciprocating flow distance. delete The method of claim 2, Passive fuel cells, characterized in that the diaphragm is formed with a plurality of protrusions protruding toward the cathode electrode. The method of claim 2, The diaphragm further includes an air guide member bent toward the cathode electrode along a part or the whole of the diaphragm. The method of claim 2, The exciter is a passive fuel cell, characterized in that the vibration motor.

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