A fuel cell stack and a method for handling water flooding faults in its single cells.

Abstract

The present invention discloses a fuel cell stack, comprising a plurality of membrane electrodes and bipolar plates stacked in sequence, wherein each bipolar plate is welded from two single polar plates, a cathode plate and an anode plate, and the membrane electrode respectively forms a single cell with adjacent cathode plates and anode plates; a method for handling a water flooding failure of a single cell is also disclosed, wherein flow channels and bridge hole structures are provided on the cathode plates and anode plates of the single cell to achieve distribution of reaction gas to a gas flow field area and recovery of excess reaction gas, and an inflatable flexible air bag is provided on the opposite side of the bridge hole in the direction of gas flow to form a shielding structure, thereby protecting normal membrane electrodes from being over-dried during the purge process, and forcing the purge gas to flow through the membrane electrode with the water flooding failure, thereby increasing the purge speed.

Description

Technical Field

[0001] The invention belongs to the field of proton exchange membrane fuel cells, and in particular relates to a proton exchange membrane fuel cell stack and a method for processing a water flooding failure of a single cell thereof. Background Art

[0002] A proton exchange membrane hydrogen-oxygen fuel cell is a power generation device that converts hydrogen oxyhydroxide chemical energy into electrical energy. When hydrogen and oxygen react to generate electricity, liquid water is also generated. In general, an excess of reactant gas is introduced, and the unreacted gas will carry away the generated liquid water. However, if there is insufficient gas, water will adhere to the membrane electrode and a flooding failure will occur. If the failure is not resolved after the flooding occurs and the operation continues, the performance and life of the membrane electrode will be affected. As the battery stack develops towards high power, the number of cells in the battery stack gradually increases, and the air intake of each cell becomes more difficult to balance, making it more likely that one or several cells will experience a flooding failure.

[0003] After investigation, it was found that the conventional way to solve flooding is to try to remove liquid water by increasing the gas flow rate. However, due to the characteristics of gas flow, the flow resistance of the flooded cell will be greater than that of other normal cells. During purging, less gas will pass through the flooded cell, making it difficult to quickly resolve the fault.

[0004] After searching the literature on the prior art, it was found that the research on the water flooding failure of proton exchange membrane fuel cells is generally a method for judging the occurrence of water flooding failure (such as patent CN201910407697.7). Occasionally, there are materials mentioning the treatment method of water flooding failure (such as patent CN107565148A), which simply says that nitrogen branch is used for purging. A method to quickly solve the water flooding failure has not yet appeared. Summary of the invention

[0005] One of the purposes of the present invention is to provide a proton exchange membrane fuel cell stack that can promptly handle a single cell flooding failure.

[0006] The technical solution adopted by the present invention to solve its technical problems is: a fuel cell stack, including a plurality of membrane electrodes and bipolar plates stacked in sequence, each bipolar plate is welded by two single-polar plates, a cathode plate and an anode plate, and the membrane electrode and the adjacent cathode plate and anode plate form a single cell; a supporting and blocking structure is respectively arranged between the membrane electrode and the cathode plate and the anode plate, and a gas main pipe and a coolant main pipe are correspondingly opened at the edges of the cathode plate and the anode plate, and flow channels are respectively arranged on the front and back surfaces of the cathode plate and the anode plate, and the weld between the cathode plate and the anode plate and the welding surface A coolant flow field is formed between the flow channels, a gas flow field is formed between the flow channels on the non-welded surfaces of the cathode plate and the anode plate and the membrane electrode, a bridge hole inlet connecting the coolant flow field and the gas main pipe is provided on the side walls of the cathode plate and the anode plate, and a bridge hole outlet connecting the bridge hole inlet and the gas flow field is also provided on the cathode plate and the anode plate. The coolant main pipe and the gas main pipe are isolated and sealed from the coolant flow field and the gas flow field by a sealing ring, and a flexible air bag is also provided outside the bipolar plate at the bridge hole outlet, and the flexible air bag is connected to an external vacuum and inflation device through an inflation hole.

[0007] The fuel cell stack has four groups of bridge hole inlets and bridge hole outlets, which are respectively arranged on the reaction gas inlet and outlet sides of the cathode plate and the anode plate.

[0008] In the fuel cell stack, the inflation hole and the sealing ring are integrally formed, thereby ensuring the sealing performance of the sealing ring.

[0009] The sealing ring of the fuel cell stack is made of silicone rubber.

[0010] The support and blocking structure of the fuel cell stack is a structure formed when the bipolar plate is formed, including a support and blocking structure a and a support and blocking structure b located on the front and rear sides of the flexible airbag on one side of the bipolar plate, and a support and blocking structure c located on the other side of the bipolar plate, which has convex strips, convex dots and protruding shapes.

[0011] The gas main pipe of the fuel cell stack comprises a gas main pipe a and a gas main pipe b respectively located on both sides of the coolant main pipe.

[0012] The second purpose of the invention is to provide a method for handling water flooding failure of a proton exchange membrane fuel cell bipolar plate, which blocks the gas passage of a normal single cell in the fuel cell stack through a bridge hole structure, so that the purge gas passes through the flooded fault single cell in a targeted manner, thereby quickly taking away the liquid water attached to the membrane electrode to solve the flooding failure of the single cell; the method comprises the following steps:

[0013] S1, after a flood fault occurs, the location of the single battery where the flood fault occurs is determined based on the voltage signal characteristics recorded by the control system;

[0014] S2, shut down to purge the fuel cell stack and exhaust the internal reaction gas;

[0015] S3, start the air pumping and inflating device to inflate the flexible airbags at the outlets of the bridge holes of all the single cells that are not flooded, and seal the bridge hole structures of all the bridge hole outlets of the single cells that are not flooded;

[0016] S4, using a small flow rate of purge gas to purge the flooded single cell;

[0017] S5, opening the air-exhausting and air-inflating device to exhaust air from the flexible airbag, so as to restore the blocked bridge hole outlet and release all blocked bridge hole structures;

[0018] S6, operate the fuel cell stack after confirming that the flooding fault has been eliminated.

[0019] The beneficial effects of the present invention are as follows: by arranging flow channels and bridge hole structures on the cathode plate and anode plate of a single cell, the reaction gas is distributed to the gas flow field area and excess reaction gas is recovered, so that the purge gas temporarily only enters the cathode and anode reaction flow fields of the single cell with a flooded fault, thereby increasing the purge time of the flooded fault and preventing the normal membrane electrode from being blown too dry to affect the performance; by arranging an inflatable flexible airbag on the side opposite to the gas flow direction of the bridge hole, the flexible airbag can be expanded by inflation to block the gas outlet of the bridge hole, and the ventilation function of the bridge hole can be restored by deflation; by arranging a shielding structure composed of a flexible airbag between the bipolar plate main pipe and the bridge hole in the flow field area, the normal membrane electrode is protected from being too dry during the purge process, and the purge gas is forced to flow through the membrane electrode with a flooded fault, thereby increasing the purge speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the local structure of the bipolar plate in the thickness direction of the present invention;

[0021] Figure 2 It is a partial schematic plan view of the bipolar plate flexible airbag of the present invention when it is in a non-working state;

[0022] Figure 3 It is a partial schematic plan view of the bipolar plate flexible airbag of the present invention in working state;

[0023] Figure 4 A schematic diagram of the inlet and outlet of the bridge hole on the anode plate of the present invention;

[0024] Figure 5 A cross-sectional view of the bipolar plate and membrane electrode after assembly of the present invention;

[0025] Figure 6 It is a schematic diagram of the structure of the inflation hole and the sealing ring of the flexible airbag of the present invention;

[0026] Figure 7This is a flow chart of the method for handling a single battery flooding fault of the present invention.

[0027] The figures are marked as follows: 1—gas main pipe a, 2—sealing ring, 3—bridge hole structure, 3-1—bridge hole entrance, 3-2—bridge hole exit, 3-3—flow channel, 4-1—support and blocking structure a, 4-2—support and blocking structure b, 4-3—support and blocking structure c, 5—inflating hole, 6—flexible airbag, 7—flow field area, 8—gas main pipe b, 9—cooling liquid main pipe, 10—weld, 11—membrane electrode, 12—cathode plate, 13—anode plate. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the examples of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0030] Example 1

[0031] Reference Figure 1 , Figure 2 and Figure 3 As shown, the present invention discloses a fuel cell stack, wherein a plurality of membrane electrodes 11 and a plurality of bipolar plates are stacked and compressed and fixed together by an external mechanical structure (screw structure or strap structure) to form a pressure, wherein each bipolar plate is welded by two single polar plates, namely, a cathode plate 12 and an anode plate 13, and the membrane electrode 11 is respectively combined with the cathode plate 12 of one of the two adjacent bipolar plates and the anode plate 13 of the other to form a single cell; a plurality of membrane electrodes 11 and bipolar plates are stacked to form a stack as shown in FIG. Figure 4 The structure of the cell stack shown is membrane electrode-cathode plate-anode plate-membrane electrode-cathode plate-anode plate-membrane electrode-cathode plate-anode plate.

[0032] The membrane electrode 11 and the cathode plate 12 and the anode plate 13 are provided with supporting and blocking structures respectively. The edges of the cathode plate 12 and the anode plate 13 are provided with gas main pipes and cooling liquid main pipes 9 respectively. Considering the gas and liquid flow in actual use, the gas main pipes include gas main pipes a1 and gas main pipes b8, which are respectively located on both sides of the cooling liquid main pipe 9. The positive and negative surfaces of the cathode plate 12 and the anode plate 13 are provided with flow channels 3-3 respectively. The weld 10 between the cathode plate 12 and the anode plate 13 and the flow channels on the welding surface are connected to the flow channels 3-3. A cooling liquid flow field is formed between the cathode plate 12 and the anode plate 13, and a gas flow field on the outside of the bipolar plate in the thickness direction is formed between the flow channel 3-3 on the non-welded surface of the cathode plate 12 and the anode plate 13 and the membrane electrode 11. A bridge hole inlet 3-1 connecting the cooling liquid flow field and the gas main pipe is provided on the side wall of the cathode plate 12 and the anode plate 13. A bridge hole outlet 3-2 connecting the bridge hole inlet 3-1 and the gas flow field is also provided on the cathode plate 12 and the anode plate 13. The bridge hole inlet 3-1, the bridge hole outlet 3-2 and the flow channel 3-3 constitute Figure 4 The bridge hole structure 3.

[0033] See also Figure 1 The bipolar plate of this embodiment is welded by a cathode plate 12 and an anode plate 13 in the thickness direction, with a coolant flow field in the middle and negative and positive gas flow fields formed by flow channels 3-3 on both sides. Figure 2 The bipolar plate of this embodiment is a centrally symmetrical structure in plane structure, with one side being the inlet and the other side being the outlet.

[0034] The coolant flow field is connected to the external coolant through the coolant main pipe 9, and the gas flow field is connected to the anode and cathode reaction gases of the fuel cell through the gas main pipe a1 and the gas main pipe b8. The coolant main pipe 9 serves as a coolant channel to send the coolant to each bipolar plate, and then takes away the reaction heat of the fuel cell from the inside of the bipolar plate through the bridge hole structure 3. The gas channel sends the anode and cathode reaction gases of the fuel cell to each bipolar plate respectively through the gas main pipe a1 and the gas main pipe b8, and then reaches the flow field area of ​​each bipolar plate through the bridge hole structure 3. The bipolar plate is a centrally symmetrical structure in the plane structure, and the middle area in the plane direction is the flow field. The coolant main pipe 9 and the gas main pipe a1 and the gas main pipe b8 are connected to the coolant flow field and the gas flow field through the sealing ring 2. Figure 4 The edges of the flow field area 7 in the flow field realize the mutual isolation and sealing of each area. The plurality of flow channels 3-3 in the flow field area 7 realize the distribution of the reaction gas and the discharge of the reaction generated water.

[0035] The bipolar plate is also provided with a flexible airbag 6 with a retractable structure at the bridge hole outlet 3-2, which can have a greater retractable amount in the direction of the bridge hole outlet 3-2. The flexible airbag 6 is connected to an external air pumping and inflating device through an inflation hole 5. The flexible airbag 6 is a hollow folding structure with expansion and contraction functions, and is a bellows-like folding structure along one direction, which can achieve a long distance of expansion. After the medium is passed into the interior, it can cover the bridge hole outlet 3-2. The non-working flexible airbag 6-1 and the working flexible airbag 6-2 are shown in FIG. Figure 3 .

[0036] When the single cell is working normally, the internal air pressure makes the flexible airbag 6-1 in a compressed state, which does not interfere with the gas passing through the bridge hole structure 3. When a single cell is flooded, the flexible airbag 6 is expanded through the inflation hole 5 set on the sealing ring 2, thereby blocking the gas channel of the single cell that is not flooded, and then the purge gas can only purge the faulty single cell. The purge effect is greatly improved, and at the same time, the membrane electrodes of other single cells are protected from being blown dry.

[0037] Furthermore, there are four groups of bridge hole inlets 3-1 and bridge hole outlets 3-2, which are respectively arranged at the inlet and outlet sides of the reaction gas of the cathode plate 12 and the anode plate 13. The support and blocking structure is a structure formed when the bipolar plate is formed, including a support and blocking structure a4-1 and a support and blocking structure b4-2 located at the front and rear sides of the flexible airbag 6 on one side of the bipolar plate, and a support and blocking structure c4-3 located on the other side of the bipolar plate, which has a convex strip shape, a convex point shape and a convex irregular shape. The setting of this structure can realize the blocking positioning of the sealing ring 2, the blocking positioning of the flexible airbag 6 after expansion, and the support of the frame of the membrane electrode 11.

[0038] The support and blocking structure a4-1 is arranged on the outer surface of the bipolar plate to achieve blocking and limiting in two directions when the flexible airbag is expanded, and to achieve support for the membrane electrode. Preferably, the support and blocking structure a4-1 is a raised strip structure. Figure 2 , Figure 3 and Figure 4 As shown, the support and blocking structure b4-2 is arranged on the lower side of the gas flow at the outlet of the bridge hole. Preferably, the support and blocking structure b4-2 is a raised dot-shaped structure, which realizes the blocking and limiting of the flexible airbag after expansion and supports the membrane electrode without blocking the passage of gas.

[0039] like Figure 5 As shown, the support and blocking structure c4-3 is arranged on the opposite side of the flexible airbag in the thickness direction of the bipolar plate. After the flexible airbag expands, it will produce a certain pressure on the membrane electrode, and the support and blocking structure c4-3 can achieve a certain support on the other side of the membrane electrode.

[0040] Furthermore, the inflation hole 5 is integrally formed with the sealing ring 2, thereby ensuring the sealing performance of the sealing ring. Figure 6 The inflation hole 5 is arranged on the sealing ring 2, which can also facilitate the inflation operation after the battery stack is assembled. The sealing ring 2 is made of silicone rubber.

[0041] In this embodiment, the bipolar plate and membrane electrode are assembled in the following manner: Figure 4 As shown in the figure, from top to bottom there are three groups of membrane electrode and bipolar plate combinations. Each single cell consists of a membrane electrode and an anode plate of the upper bipolar plate and a cathode of the lower bipolar plate.

[0042] During normal operation, the positive and negative reaction gases enter the flow field area through two bridge hole structures respectively to react, and the excess gas flows back to the main pipe through the other two bridge hole structures.

[0043] Example 2

[0044] In this embodiment, if a water-flooding fault occurs in one or several cells, the cells that have not been flooded can be shielded and then purged to quickly eliminate the fault. Figure 7 As shown, the specific operations are as follows:

[0045] S1, after a flood fault occurs, the location of the single battery where the flood fault occurs is determined based on the voltage signal characteristics recorded by the control system.

[0046] S2, shut down to purge the fuel cell stack and exhaust the internal reaction gas.

[0047] S3, start the air pumping and inflating device to inflate the flexible airbags 6 at the bridge hole outlets 3-2 of all the cells that are not flooded, and seal the bridge hole structures of all the bridge hole outlets 3-2 of the cells that are not flooded.

[0048] S4, using a small flow rate of purge gas to purge the flooded single cell.

[0049] S5, the air-exhausting and air-inflating device is turned on to exhaust the air in the flexible airbag 6, so as to restore the blocked bridge hole outlet 3-2 and release all blocked bridge hole structures.

[0050] S6, operate the fuel cell stack after confirming that the flooding fault has been eliminated.

[0051] It is easy for those skilled in the art to understand that the above description is only a preferred use case of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A fuel cell stack, comprising a plurality of membrane electrodes (11) and bipolar plates stacked in sequence, each bipolar plate being welded together by a cathode plate (12) and an anode plate (13), and the membrane electrode (11) and the adjacent cathode plate (12) and anode plate (13) forming a single cell; characterized in that: Supporting and blocking structures are respectively arranged between the membrane electrode (11) and the cathode plate (12) and the anode plate (13); gas main pipes and cooling liquid main pipes (9) are correspondingly provided at the edges of the cathode plate (12) and the anode plate (13); flow channels (3-3) are respectively provided on the front and back sides of the cathode plate (12) and the anode plate (13); a cooling liquid flow field is formed between the weld (10) between the cathode plate (12) and the anode plate (13) and the flow channel (3-3) on the welded surface; and a gas flow field is formed between the flow channel (3-3) on the non-welded surface of the cathode plate (12) and the anode plate (13) and the membrane electrode (11). The cathode plate (12) and the anode plate (13) are provided with a bridge hole inlet (3-1) connecting the coolant flow field and the gas main pipe on the side wall, and the cathode plate (12) and the anode plate (13) are also provided with a bridge hole outlet (3-2) connecting the bridge hole inlet (3-1) and the gas flow field. The coolant main pipe (9) and the gas main pipe are isolated and sealed from the coolant flow field and the gas flow field by a sealing ring (2). A flexible air bag (6) is also provided outside the bipolar plate at the bridge hole outlet (3-2), and the flexible air bag (6) is connected to an external air pumping and charging device through an inflation hole (5).

2. A fuel cell stack according to claim 1, characterized in that: There are four groups of bridge hole inlets (3-1) and bridge hole outlets (3-2), which are respectively arranged on the reaction gas inlet and outlet sides of the cathode plate (12) and the anode plate (13).

3. A fuel cell stack according to claim 1, characterized in that: The inflation hole (5) and the sealing ring (2) are integrally formed.

4. A fuel cell stack according to claim 1, characterized in that: The sealing ring (2) is made of silicone rubber.

5. A fuel cell stack according to claim 1, characterized in that: The support and blocking structure comprises a support and blocking structure a (4-1) and a support and blocking structure b (4-2) located at the front and rear sides of the flexible airbag (6) on one side of the bipolar plate, and a support and blocking structure c (4-3) located on the other side of the bipolar plate.

6. A fuel cell stack according to claim 1, characterized in that: The gas main pipe comprises a gas main pipe a (1) and a gas main pipe b (8) respectively located on both sides of the coolant main pipe (9).

7. A method for handling a single cell flooding fault of a fuel cell stack as claimed in claim 1, characterized in that: The steps include: S1, after a flood fault occurs, the location of the single battery where the flood fault occurs is determined based on the voltage signal characteristics; S2, shut down to purge the fuel cell stack and exhaust the internal reaction gas; S3, starting the air extraction and inflation device to inflate the flexible airbags (6) at the bridge hole outlets (3-2) of all the single cells that are not submerged in water, thereby blocking the bridge hole outlets (3-2); S4, using a small flow rate of purge gas to purge the flooded single cell; S5, opening the air-exhausting and air-inflating device to exhaust air from the flexible airbag (6), thereby restoring the blocked bridge hole outlet (3-2); S6, operate the fuel cell stack after confirming that the flooding fault has been eliminated.

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