Flow field plate module for fuel cell system

A flow field plate module for a fuel cell system includes at least one flow field plate defining a fuel transporting channel thereon. The fuel transporting channel is divided into a middle converging zone having a group of first flow guiding plates arranged therein, and two diverging zones located at two lateral sides of the middle converging zone and each having a group of second flow guiding plates arranged therein. The second flow guiding plates are symmetrically arranged in the two diverging zones and are directed at respective inner end toward a space between two adjacent first flow guiding plates in the middle converging zone to thereby offset from each of the two adjacent first flow guiding plates by a predetermined distance in a fuel flowing direction, so that a fluid path is formed between any two adjacent first and second flow guiding plates.

FIELD OF THE INVENTION

The present invention relates to a fuel cell, and more particularly, to a flow field plate module for a fuel cell system.

BACKGROUND OF THE INVENTION

A fuel cell system is a power-generating device that generates electrical energy through electrochemical reaction of hydrogen-containing fuel with air. Since it has the advantages of low pollution, low noise, and high efficiency, the fuel cell system is an energy technique meeting nowadays requirements. Among various fuel cell systems, the proton exchange membrane fuel cell (PEMFC) and the direct methanol fuel cell (DMFC) are the two most common fuel cell systems.

Please refer toFIG. 1that shows a conventional flow field plate module1for a fuel cell system. As shown, the flow field plate module1includes a membrane electrode assembly (MEA)11, and an anode flow field plate12and a cathode flow field plate13separately located at two opposite outer sides of the MEA11. The MEA11consists of a proton exchange membrane (PEM), an anode catalyst layer112, a cathode catalyst layer113, an anode gas diffusion layer (GDL)114, and a cathode gas diffusion layer115. The anode flow field plate12and the cathode flow field plate13are normally made of graphite, and are provided on respective inner side surface with flow channels121,131, through which reactants flow.

To pump methanol-water solution through the flow channels121on the anode flow field plate12to react with the anode catalyst layer112in the MEA11, good flow channel design is needed to enable uniform reaction of the methanol-water solution with the anode catalyst layer112. In addition, since anode product, such as carbon dioxide, is produced in the reaction of the methanol-water solution with the anode catalyst, the flow channel of the anode flow field plate designed must also be capable of successfully discharging the anode product.

The conventional flow channels on the anode flow field plate may be differently designed.FIG. 2shows a serpentine flow channel design, andFIG. 3shows a parallel channel design. In the serpentine flow channel design, a continuously winding path, i.e. a serpentine flow channel121a, is provided on the anode flow field plate12. The serpentine flow channel121ais communicably connected at an end to an anode fuel inlet14, and at the other end to an anode fuel outlet15. In the parallel flow channel design, a plurality of parallelly connected paths, or flow channels121b, are provided on the anode flow field plate12. One common end of the plurality of parallel flow channels121bis communicably connected to an anode fuel inlet14, and another common end of the plurality of parallel flow channels121bis communicably connected to an anode fuel outlet15.

Both the serpentine and the parallel flow channel design achieve the purpose of transporting fluid, that is, the methanol-water solution. However, these two types of flow channel design have respective disadvantages. For example, the serpentine flow channel121ais relatively long to cause excessively large pressure loss in the course of transporting the fluid in the direction as indicated by the arrows inFIG. 2. Therefore, a pump providing a relative high pressure is needed to drive the methanol-water solution to flow through the serpentine flow channel121a. Moreover, the methanol-water solution at the upstream of the serpentine flow channel121areacts at the anode catalyst before it flows to the downstream. The methanol-water solution at the downstream of the serpentine flow channel121atherefore has a concentration lower than that of the solution at the upstream. That is, the serpentine flow channel121ahas the problem of changing methanol concentration diminishingly from the upstream to the downstream.

On the other hand, while the parallel flow channel design overcomes the problem of changing methanol concentration between the upstream and the downstream serpentine flow channel, another problem with non-uniformly distributed flow in the parallelly arranged flow channels121bis found. When the produced carbon dioxide accumulates in the flow channels, increased flow resistance is produced in the flow channels. Since the fuel tends to flow toward flow channels121bthat have somewhat lower flow resistance, it is difficult to discharge the produced carbon dioxide.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a flow field plate module for a fuel cell system that includes at least one flow field plate defining a fuel transporting channel thereon. In the fuel transporting channel, a first and two second flow guide groups are provided to form a good flow field, enabling the anode fuel to be uniformly distributed in the fuel transporting channel.

Another object of the present invention is to provide a flow field plate module for a fuel cell system, in which first and second flow guide groups are arranged to enable uniform fuel concentration in different areas of the flow field plate.

A further object of the present invention is to provide a flow field plate module for a fuel cell system, in which a plurality of flow guiding plates are symmetrically arranged to enable fuel flowing through the flow field plate to uniformly distribute in all flow channels formed on the flow field plate.

To achieve the objectives mentioned above, in accordance with an preferred embodiment of the present invention, a flow field plate module for a fuel cell system comprises at least a flow field plate, the flow field plate comprises a main body, a first flow guide group and two second flow guide groups. The main body has a fuel-in wall provided with a fuel inlet, a fuel-out wall provided with a fuel outlet, and two corresponding side walls, which together define a fuel transporting channel in the main body. The fuel transporting channel is divided into a middle converging zone and two diverging zones separately located at two lateral sides of the middle converging zone. The fuel inlet and the fuel outlet are provided in the middle converging zone, such that fuel introduced into the fuel transporting channel via the fuel inlet flows in a first flowing direction before being discharged from the main body via the fuel outlet. The first flow guide group includes a plurality of first flow guiding plates arranged in the middle converging zone to space from one another in the first flowing direction. The two second flow guide groups are arranged in the two diverging zones at two opposite sides of the first flow guide group, each of the second flow guide groups includes at least one second flow guiding plate. Each of the second flow guiding plates is directed at an inner end toward a space between two adjacent first flow guiding plates in the middle converging zone to thereby offset from each of the two adjacent first flow guiding plates by a predetermined distance, allowing a fluid path to be formed between any two adjacent first and second flow guiding plates. When the fuel is introduced into the fuel transporting channel via the fuel inlet, the fuel is repeatedly guided by the first flow guiding plates toward the two diverging zones to form two branch flows, which are then guided by the laterally corresponding second flow guiding plates to flow toward the middle converging zone via the offset distance and form a main flow again; and the diverging and converging of the fuel repeats until the fuel is finally guided to the fuel outlet and discharged from the main body.

The present invention effectively overcomes the problem of an excessively long flow channel existed in the conventional serpentine flow channel design for the fuel cell flow field plate, and accordingly, enables reduced pressure loss in the course of transporting a fluid fuel. The present invention also effectively solves the problem of non-uniform concentration of methanol-water solution existed in the serpentine flow channel by arranging a plurality of flow guiding plates in the flow transporting channel on the flow field plate of the present invention. The present invention also overcomes the problem of non-uniform distribution of fuel flow existed in the conventional parallel flow channel design, and improves the discharge of carbon dioxide, which is the anode reaction product produced in the fuel cell.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Please refer toFIG. 4, according to a first embodiment of the present invention, a flow field plate module for a fuel cell system comprises a flow field plate100. As shown, the flow field plate100includes a main body2, a first flow guide group3, and two second flow guide groups4,5. The main body2has a fuel-in wall21, a fuel-out wall22, and two corresponding side walls23,24, which together define a fuel transporting channel20in the main body2.

The fuel-in wall21is provided with a fuel inlet211, and the fuel-out wall22is provided with a fuel outlet221. In the illustrated first embodiment, a direct methanol fuel cell (DMFC) is exemplified, and a methanol-water solution is used as an anode fuel Fin; and the flow field plate100is an anode flow field plate provided with flow channels for transporting the methanol-water solution.

The fuel transporting channel20is divided into a middle converging zone A1, and two diverging zones A2, A3separately located at two lateral sides of the middle converging zone A1. More specifically, the diverging zone A2is located between the middle converging zone A1and the side wall23, and the diverging zone A3is located between the middle converging zone A1and the side wall24. The fuel inlet211and the fuel outlet221are located at two opposite ends of the middle converging zone A1. The anode fuel is introduced into the fuel transporting channel20via the fuel inlet211to flow toward and be discharged via the fuel outlet221in a first flowing direction I.

The first flow guide group3is arranged within the middle converging zone A1, and comprises a plurality of first flow guiding plates31,32,33,34, which are in the form of flat partition plates and sequentially spaced along the first flowing direction I to be parallel with one another in lengthwise direction and perpendicular to the first flowing direction I.

The second flow guide groups4,5are correspondingly arranged in the two diverging zones A2, A3at two lateral sides of the first flow guide group3. The second flow guide group4comprises at least one left second flow guiding plate, in this embodiment, there are three left second flow guiding plates41,42,43, which are spaced along the first flowing direction I within the diverging zone A2of the fuel transporting channel20. Similarly, the second flow guide group5comprises at least one right second flow guiding plate, in this embodiment, there are three right second flow guiding plates51,52,53, which are spaced along the first flowing direction I within the diverging zone A3of the fuel transporting channel20. The left second flow guiding plates41,42,43and the right second flow guiding plates51,52,53are flat partition plates laterally symmetrically arranged relative to the middle converging zone A1. More specifically, the left second flow guiding plate41is located corresponding to the right second flow guiding plate51, the left second flow guiding plate42is located corresponding to the right second flow guiding plate52, and the left second flow guiding plate43is located corresponding to the right second flow guiding plate53. All the left second flow guiding plates41,42,43in the second flow guide group4and the right second flow guiding plates51,52,53in the second flow guide group5are parallel with one another in the lengthwise direction and perpendicular to the first flowing direction I.

Each of the left second flow guiding plates41,42,43in the second flow guide group4is connected at respective outer end to the side wall23, and with respective inner end offset from two adjacent first flow guiding plates31,32,33,34by a predetermined distance in the first flowing direction I, such as the left second flow guiding plate41is offset from the first flow guiding plates31,32by distances d1, d2, respectively, so that a fluid path20ais formed between any two adjacent first flow guiding plates and left second flow guiding plate. Similarly, each of the right second flow guiding plates51,52,53in the second flow guide group5is connected at respective outer end to the side wall24, and with respective inner end offset from the first flow guiding plates31,32,33,34by a predetermined distance in the first flowing direction I, such as the right second flow guiding plate51is offset from the first flow guiding plates31,32by distances d1, d2, respectively, so that a fluid path20bis formed between any two adjacent first flow guiding plates and right second flow guiding plate.

Please refer toFIG. 5. When the anode fuel Fin is introduced into the fuel transporting channel20via the fuel inlet211to flow in the first flowing direction I and reach the first flow guiding plate31, the anode fuel Fin is caused to flow in two opposite flowing directions II and III toward the two diverging zones A2, A3and forms two branch flows F1, F2, which are respectively guided by the second flow guiding plates41,51to flow through the fluid paths20a,20bto converge in the middle converging zone A1again and form a main flow F12. The main flow F12keeps flowing forward and is repeatedly diverged and converged at subsequent staggered first flow guiding plates32,33,34and second flow guiding plates (42,52) & (43,53). The main flow F12is finally guided through the fuel outlet221and discharged as an anode fuel Fout.

Please refer toFIG. 6, according to a second embodiment of the present invention, a flow field plate module for a fuel cell system comprises an integrated flow field plate200having an outer frame2′, and a plurality of flow field plates100,100a,100barranged in the outer frame2′ of the integrated flow field plate200. The plurality of flow field plates100,100a,100bare arranged side by side to space from one another in a direction perpendicular to the first flowing direction I, and are structurally similar to the flow field plate100in the first embodiment. The integrated flow field plate200internally forms a common fuel transporting channel6, and is provided with a common fuel inlet61and a common fuel outlet62. The common fuel transporting channel6internally includes a fuel-in path63and a fuel-out path64.

Each of the flow field plates100,100a,100bforms an independent flow channel structure, and they are arranged side by side to together produce a flow field. The fuel inlets211of the independent flow field plates100,100a,100bare in communication with the fuel-in path63, and the fuel outlets221of the independent flow field plates100,100a,100bare in communication with the fuel-out path64. With these arrangements, an even more uniform flow field distribution is obtained on the integrated flow field plate200, and the difference in the concentrations of the anode catalyst among different areas in the integrated flow field plate200is reduced.

When the anode fuel Fin is supplied into the fuel-in path63of the common fuel transporting channel6via the common fuel inlet61of the integrated flow field plate200, the anode fuel Fin flows into the fuel transporting channels20of the flow field plates100,100a,100bvia the fuel inlets211thereof, and then flows through the fuel transporting channels20and the fuel outlets221into the fuel-out path64of the common fuel transporting channel6, and is finally discharged from the integrated flow field plate200via the common fuel outlet62.

InFIG. 7, according to a third embodiment of the present invention, a flow field plate module for a fuel cell system includes an integrated flow field plate300having an outer frame2″, and a plurality of flow field plates100,100a,100b,100carranged inside the outer frame2″ as a rectangular matrix, such as a 2×2 matrix, so that the flow field plates100,100a,100b,100care spaced in a direction perpendicular to the first flowing direction I. The flow field plates100,100a,100b,100care structurally similar to the flow field plates100in the first embodiment, and each forms an independent flow channel structure. The flow field plates100,100a,100b,100carranged as a rectangular matrix therefore together form an integrated flow field plate300that enables a uniform flow field distribution thereon and reduces the differences of the anode fuel concentration among different areas of the anode catalyst.

FIG. 8shows a flow field plate100dfor a fuel cell system according to a fourth embodiment of the present invention. The fourth embodiment is generally structural similar to the first embodiment. Elements that are the same in the first and the fourth embodiment are denoted with identical reference numerals. The fourth embodiment is different from the first embodiment in that each of the first flow guiding plates in the first flow guide group3is provided with an opening extended in the first flowing direction I. For example, the first flow guiding plate31is provided with an opening311extended in the first flowing direction I. Therefore, when the anode fuel Fin flows to the first flow guiding plate31, part of the anode fuel Fin directly passes through the opening311. The fourth embodiment is also different from the first embodiment in that an opening is provided between the side walls23,24and each of the second flow guiding plates in the second flow guide groups4and5, respectively. For example, an opening411is formed between the side wall23and the flow guiding plate41; and an opening511is formed between the side wall24and the flow guiding plate51. Therefore, when the anode fuel Fin flows to the second flow guiding plates41,51, part of the anode fuel Fin directly passes through the opening411,511. Moreover, the flow field plate100,100a,100b,100cin the second and the third embodiment may also be configured as the flow field plate100din the fourth embodiment.

Please refer toFIG. 9that shows a flow field plate100efor a fuel cell system according to a fifth embodiment of the present invention. As shown, the fifth embodiment is generally structurally similar to the fourth embodiment, except for a plurality of openings311,312that are formed on each of the first flow guiding plates in the first flow guide group3, and a plurality of openings412,512are further formed on each of the second flow guiding plates in the second flow guide groups4,5, respectively, besides the opening411formed between the side wall23and the flow guiding plate41and the opening511between the side wall24and the flow guiding plate51. Again, the flow field plate100,100a,100b,100cin the second and the third embodiment may also be configured as the flow field plate100ein the fifth embodiment.

FIG. 10shows a flow field plate100ffor a fuel cell system according to a sixth embodiment of the present invention. As shown, the sixth embodiment is generally structurally similar to the first embodiment, except that each of the flow guiding plates in the first flow guide group3is provided on one side facing against the first flowing direction I with an arc-curved surface313to further reduce the flow resistance of the fuel flowing through the first flow guiding plates.