Fuel cell stack with uniform temperature distribution

Abstract

The invention provides a fuel cell stack with uniform temperature distribution. The fuel cell stack comprises a bipolar plate and runner systems positioned on two sides of the bipolar plate, a cooling liquid flow field of the bipolar plate is divided into a plurality of areas, two communication ports are formed in each area, and a plurality of inner flow channels communicated with the two communication ports are formed between the two communication ports in each area; one communicating port of each area is communicated with the runner system on one side, the other communicating port of each area is communicated with the runner system on the other side, valves for switching flow directions are arranged in the runner systems, and the flow directions in the adjacent areas in the bipolar plate are the same or different by controlling the runner systems on the two sides. According to the invention, the outer layer of the sliding composite end is matched with different cooling runners, so that two heat dissipation strategies can be realized; and the bipolar plates are subjected to partitioned thermal management, so that the temperature distribution of the cooling liquid in the gaps of the bipolar plates is uniform, and the temperature balance of the fuel cell stack can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a fuel cell stack with uniform temperature distribution. Background Art

[0002] As energy and environmental issues become increasingly tense, hydrogen energy, as the ultimate form of energy, is favored by countries around the world. Hydrogen fuel cell technology has become a research hotspot in the world's energy field due to its high conversion efficiency, pollution-free, wide fuel source, low operating temperature, and rapid start and stop. Hydrogen fuel cells are the key carrier for converting hydrogen energy into electrical energy. After the carbon neutrality and carbon peak goals were proposed, they have received new attention at the basic research and industrial application levels.

[0003] However, changes in fuel cell temperature have a huge impact on internal electrochemical reactions, material transfer and other processes. According to research, both high and low temperatures will affect the performance of the fuel cell. When the battery temperature is too high, high temperature will cause the proton exchange membrane (PEM) to become dry, and the conductivity and transfer characteristics of the proton exchange membrane will decrease, resulting in increased ohmic loss and concentration loss, and reduced stack output performance. Low temperature will also affect the efficiency of the fuel cell, resulting in reduced conductivity and increased ohmic polarization. At the same time, the diffusion rate of gas decreases at low temperatures, increasing concentration polarization. This will affect the performance of the stack, so it is very important to reasonably control the temperature range.

[0004] However, based on the existing fuel cells today, most thermal management solutions only consider the amount of heat dissipation, thus ignoring temperature balance. The fuel cell stack requires a small temperature difference during operation, and the temperature difference between the inlet and outlet should not exceed 10°C to ensure consistency. Unreasonable water thermal management may lead to liquid water retention and power loss. Summary of the invention

[0005] In view of the fact that the internal temperature of hydrogen fuel cells is prone to unevenness during operation, the present invention provides a fuel cell stack with uniform temperature distribution. By matching different cooling channels with the outer layer of the sliding composite end, two heat dissipation strategies can be implemented. The bipolar plates are thermally managed in different zones to make the temperature of the coolant in the gap between the bipolar plates evenly distributed, which can effectively improve the temperature balance of the fuel cell stack.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A fuel cell stack with uniform temperature distribution comprises a bipolar plate and a flow channel system located on both sides of the bipolar plate; the coolant flow field of the bipolar plate is divided into a plurality of regions, each region is provided with two connecting ports, and a plurality of internal flow channels connected to the two connecting ports in each region are provided between the two connecting ports; a connecting port in each region is connected to the flow channel system on one side, and another connecting port in each region is connected to the flow channel system on the other side; a valve for switching flow direction is provided in the flow channel system, and the flow directions in adjacent regions of the bipolar plate are made the same or different by controlling the flow channel systems on both sides.

[0008] Furthermore, the flow channel system includes an inner layer of a composite end plate, an outer layer of a composite end plate and a sliding mechanism; the inner layer of the composite end plate is installed on the bipolar plate, and the flow channel of the inner layer of the composite end plate is connected to each area respectively; the outer layer of the composite end plate is installed on the inner layer of the composite end plate through a sliding mechanism, and the flow direction of the coolant in the adjacent area is changed by moving the outer layer of the composite end plate to implement a heat dissipation strategy.

[0009] Furthermore, a first flow channel, a second flow channel and a third flow channel are provided in the outer layer of the composite end plate; the outer layer of the composite end plate is provided with two interfaces for the entry and exit of the cooling liquid; one of the interfaces is connected with one end of the first flow channel and the second flow channel respectively through a three-way control valve, and the other interface is connected with one end of the third flow channel through a two-way control valve; a plurality of inner layer flow channels are provided in the inner layer of the composite end plate, and each inner layer flow channel is connected with a connecting port in an area of ​​the bipolar plate; the second flow channel and the third flow channel are high-power flow channels, and the first flow channel is a low-power flow channel, and a sliding mechanism is provided between the inner layer of the composite end plate and the outer layer of the composite end plate, which slides between the inner layer of the composite end plate and the outer layer of the composite end plate to switch a plurality of inner layer flow channels to be connected with the high-power flow channel or the low-power flow channel.

[0010] Furthermore, the inner layer of the composite end plate and the outer layer of the composite end plate are connected by a sliding mechanism to form a 2-position 3n-way reversing valve, where n is equal to the number of regions in the bipolar plate. By controlling the reversing valve, the flow directions in adjacent regions of the bipolar plate are switched from the same to different, which is used to switch the cooling mode of the fuel cell under high and low power.

[0011] Furthermore, the coolant flow field of the bipolar plate is divided into n regions, and the corresponding first flow channel outlet is divided into n branches, which are low-power flow channel branches; the second flow channel outlet is divided into n / 2 branches, and the third flow channel outlet is divided into n / 2 branches. The n / 2 branches of the second flow channel outlet and the n / 2 branches of the third flow channel outlet are high-power flow channel branches; by controlling the sliding between the inner layer of the composite end plate and the outer layer of the composite end plate and controlling the switching of the three-way control valve and the two-way control valve, the n region is connected to the high-power flow channel or the low-power flow channel.

[0012] Furthermore, two cooling channel layers are provided in the outer layer of the composite end plate, the first cooling channel layer has a first channel, a second channel and a three-way control valve, and the second cooling channel layer has a third channel and a two-way control valve.

[0013] Furthermore, it also includes a control system and a sensor, wherein the sensor is used to measure the temperature difference on both sides of the bipolar plate or the operating power of the fuel cell stack; the control system selectively controls the switching of the three-way control valve and the two-way control valve in the flow channel system according to the temperature difference on both sides of the bipolar plate fed back by the sensor, and selectively controls the sliding of the inner layer and the outer layer of the composite end plate.

[0014] Furthermore, the sensor is a temperature sensor for measuring the temperature difference on both sides of the bipolar plate; the flow channel systems on both sides of the bipolar plate are respectively an upper flow channel system and a lower flow channel system; the upper flow channel system and the lower flow channel system are respectively provided with an inlet and an outlet

[0015] When the temperature difference Ca on both sides of the bipolar plate is ≤10°C, the control system controls the three-way control valve of the upper flow channel system to connect the inlet of the upper flow channel system with its low-power flow channel, and the control system controls the three-way control valve of the lower flow channel system to connect the outlet of the lower flow channel system with its low-power flow channel, so that a one-way flow channel is formed between the inlet of the upper flow channel system, the low-power flow channel of the upper flow channel system, the bipolar plate, the low-power flow channel of the lower flow channel system and the outlet of the lower flow channel system;

[0016] When the temperature difference Ca on both sides of the bipolar plate is greater than 10°C, the control system controls the three-way control valve of the upper flow channel system to connect the inlet of the upper flow channel system with its second flow channel, the control system controls the two-way control valve of the upper flow channel system to connect the outlet of the upper flow channel system with its third flow channel, the control system controls the three-way control valve of the lower flow channel system to connect the outlet of the lower flow channel system with its second flow channel, the control system controls the two-way control valve of the lower flow channel system to connect the inlet of the lower flow channel system with its third flow channel, and the control system controls the inner layer of the composite end plate and the outer layer of the composite end plate of the upper flow channel system and the lower flow channel system to slide, thereby forming a one-way flow channel between the inlet of the upper flow channel system, the second flow channel of the upper flow channel system, the bipolar plate, the second flow channel of the lower flow channel system and the outlet of the lower flow channel system, and forming a one-way flow channel in another direction between the inlet of the lower flow channel system, the third flow channel of the lower flow channel system, the bipolar plate, the third flow channel of the upper flow channel system and the outlet of the upper flow channel system.

[0017] Furthermore, the sensor is a power sensor for measuring the working power of the fuel cell stack; the flow channel systems on both sides of the bipolar plate are respectively an upper flow channel system and a lower flow channel system; the upper flow channel system and the lower flow channel system are respectively provided with an inlet and an outlet

[0018] When the working power of the fuel cell stack is ≤60% of the rated power, the control system controls the three-way control valve of the upper flow channel system to connect the inlet of the upper flow channel system with its low-power flow channel, and the control system controls the three-way control valve of the lower flow channel system to connect the outlet of the lower flow channel system with its low-power flow channel, so that a one-way flow channel is formed between the inlet of the upper flow channel system, the low-power flow channel of the upper flow channel system, the bipolar plate, the low-power flow channel of the lower flow channel system and the outlet of the lower flow channel system;

[0019] When the operating power of the fuel cell stack is greater than 60% of the rated power, the control system controls the three-way control valve of the upper flow channel system to connect the inlet of the upper flow channel system with its second flow channel, the control system controls the two-way control valve of the upper flow channel system to connect the outlet of the upper flow channel system with its third flow channel, the control system controls the three-way control valve of the lower flow channel system to connect the outlet of the lower flow channel system with its second flow channel, the control system controls the two-way control valve of the lower flow channel system to connect the inlet of the lower flow channel system with its third flow channel, and the control system controls the inner layer of the composite end plate and the outer layer of the composite end plate of the upper flow channel system and the lower flow channel system to slide, thereby forming a one-way flow channel between the inlet of the upper flow channel system, the second flow channel of the upper flow channel system, the bipolar plate, the second flow channel of the lower flow channel system and the outlet of the lower flow channel system, and forming a one-way flow channel in another direction between the inlet of the lower flow channel system, the third flow channel of the lower flow channel system, the bipolar plate, the third flow channel of the upper flow channel system and the outlet of the upper flow channel system.

[0020] The beneficial effects of the present invention are:

[0021] 1. The fuel cell stack with uniform temperature distribution described in the present invention divides the entire fuel cell stack into different areas by partitioning the end plate coolant flow channels of the fuel cell bipolar plates and longitudinally partitioning the coolant manifold, and improves the heat dissipation performance by mechanically corresponding thermal management of different areas.

[0022] 2. The fuel cell stack with uniform temperature distribution described in the present invention changes the direction of the coolant in the convection area by splitting the end plate into an upper composite end plate and a lower composite end plate and selecting a balance mode.

[0023] 3. The fuel cell stack with uniform temperature distribution described in the present invention controls the flow channel selection of the outer layer of the composite end plate and the state of the three-way valve according to the temperature through a control system. When the temperature difference is lower than a threshold value, the flow channels in each region of the bipolar plate have a uniform flow direction; when the temperature difference is higher than the threshold value, the coolant flow direction of the flow channels in each region of the bipolar plate has a cross flow direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For ordinary technicians in this field, it is obvious that other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 A three-dimensional diagram of a fuel cell stack with uniform temperature distribution according to the present invention.

[0026] Figure 2 This is a three-dimensional diagram of the outer layer of the composite end plate of the present invention.

[0027] Figure 3 This is a schematic diagram of the low power mode described in the present invention.

[0028] Figure 4 This is a schematic diagram of the high power mode of the present invention.

[0029] Figure 5 This is a cross-sectional view of the outer layer of the upper composite end plate described in the present invention.

[0030] Figure 6 This is a cross-sectional view of the outer layer of the lower composite end plate described in the present invention.

[0031] Figure 7 This is a diagram of the outer interface of the composite end plate described in the present invention.

[0032] Figure 8 Schematic diagram of different cooling layers according to the present invention.

[0033] Fig. 9 This is a simulation diagram of a fuel cell stack with uniform temperature distribution in low power mode as described in the present invention.

[0034] Fig.10 This is a simulation diagram of a fuel cell stack with uniform temperature distribution in high power mode as described in the present invention.

[0035] In the figure:

[0036] 1-upper total coolant inlet; 2-upper total coolant outlet; 3-upper composite end plate outer layer; 3-1-upper coolant flow channel layer; 3-1-1-upper composite end plate first flow channel; 3-1-2-upper composite end plate three-way control valve; 3-1-3-upper composite end plate second flow channel; 3-2-upper coolant flow channel second layer; 3-2-1-upper composite end plate third flow channel; 3-2-2-upper composite end plate two-way control valve; 5-upper composite end plate inner layer; 6-bipolar plate; 7 -inner layer of lower composite end plate; 8-outer layer of lower composite end plate; 8-1-lower coolant flow channel layer; 8-1-1-lower composite end plate first flow channel; 8-1-2-lower composite end plate three-way control valve; 8-1-3-lower composite end plate second flow channel; 8-2-lower coolant flow channel second layer; 8-2-1-lower composite end plate third flow channel; 8-2-2-lower composite end plate two-way control valve; 9-lower total coolant inlet; 10-lower total coolant outlet; 11-sliding track. DETAILED DESCRIPTION

[0037] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0038] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0039] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] like Figure 1 As shown, the fuel cell stack with uniform temperature distribution described in the present invention includes a bipolar plate 6 and a flow channel system located on both sides of the bipolar plate 6; the coolant flow field of the bipolar plate 6 is divided into several areas, each area is provided with two connecting ports, and several manifolds connected to the two connecting ports in each area are provided between the two connecting ports; one connecting port in each area is connected to the flow channel system on one side, and the other connecting port in each area is connected to the flow channel system on the other side. A valve for switching flow direction is provided in the flow channel system, and the flow directions in adjacent areas of the bipolar plate 6 are made the same or different by controlling the flow channel systems on both sides according to the power size. The flow channel system includes a composite end plate inner layer, a composite end plate outer layer and a sliding mechanism; the composite end plate inner layer is installed on the bipolar plate 6, and the flow channel of the composite end plate inner layer is connected to each area respectively; the composite end plate outer layer is installed on the composite end plate inner layer through a sliding mechanism, and the flow direction of the coolant in the adjacent area is changed by moving the composite end plate outer layer, so as to realize the heat dissipation strategy.

[0041] Implementation example Figure 1 As shown, the fuel cell stack with uniform temperature distribution described in the present invention includes a bipolar plate 6, a membrane electrode, an upper composite end plate outer layer 3, an upper composite end plate inner layer 5, a lower composite end plate inner layer 7 and a lower composite end plate outer layer 8; the upper composite end plate inner layer 5 is installed on one side of the bipolar plate 6, and the lower composite end plate inner layer 7 is installed on the other side of the bipolar plate 6, the upper composite end plate inner layer 5 is connected to the upper composite end plate outer layer 3 by a sliding track 11, forming an upper flow channel system; the lower composite end plate inner layer 7 is connected to the upper composite end plate outer layer 8 by a sliding track 11, forming a lower flow channel system.

[0042] The cooling liquid flow channel of the bipolar plate 6 is designed in a zoned manner, and the entire heat dissipation area is evenly divided into 4 cooling areas, which are independent of each other, and each area accounts for about 25% of the entire heat dissipation area. Each cooling area has a connecting port at both ends, and m internal flow channels are arranged between the two connecting ports. The m cooling liquid cooling flow channels are independent of each other, and the number m is based on the area of ​​the cooling liquid flow area. The width of a single cooling liquid flow channel is 1mm-2mm, and m≥4, which is used to make the coolant flow in the cooling area.

[0043] like Figure 3 and Figure 5As shown, the upper flow channel system and the lower flow channel system are symmetrical structures. Taking the upper flow channel system as an example, the upper composite end plate outer layer 3 is provided with an upper total coolant inlet 1 and an upper total coolant outlet 2; the upper composite end plate outer layer 3 is provided with an upper composite end plate first flow channel 3-1-1, an upper composite end plate second flow channel 3-1-3 and an upper composite end plate third flow channel 3-2-1; the upper composite end plate outer layer 3 is installed with an upper composite end plate three-way control valve 3-1-2, the upper composite end plate three-way control valve 3-1-2 inlet is connected with the upper total coolant inlet 1, one outlet of the upper composite end plate three-way control valve 3-1-2 is connected with the upper composite end plate first flow channel 3-1-1, and the other outlet of the upper composite end plate three-way control valve 3-1-2 is connected with the upper composite end plate second flow channel 3-1-3; the upper total coolant outlet 2 is connected with one end of the upper composite end plate third flow channel 3-2-1 through the upper composite end plate two-way control valve 3-2-2;

[0044] Four inner flow channels are provided in the inner layer 5 of the upper composite end plate, and each inner flow channel is connected to a connecting port in an area of ​​the bipolar plate 6; the second flow channel 3-1-3 and the third flow channel 3-2-1 of the upper composite end plate are high-power flow channels, and the first flow channel 3-1-1 of the upper composite end plate is a low-power flow channel. A sliding track 11 is provided between the inner layer 5 of the upper composite end plate and the outer layer 3 of the upper composite end plate, and an external force is used to slide between the inner layer 5 of the upper composite end plate and the outer layer 3 of the upper composite end plate, so as to switch a number of inner flow channels to be connected to the high-power flow channel or the low-power flow channel.

[0045] like Figure 3 As shown, the coolant flow field of the bipolar plate 6 is divided into 4 areas, and the corresponding outlet of the first flow channel 3-1-1 of the upper composite end plate is divided into 4 branches, which are low-power flow channel branches; the outlet of the second flow channel 3-1-3 of the upper composite end plate is divided into 2 branches, and the outlet of the third flow channel 3-2-1 of the upper composite end plate is divided into 2 branches, which are high-power flow channel branches; by controlling the sliding between the inner layer of the composite end plate and the outer layer of the composite end plate and controlling the switching of the three-way control valve and the two-way control valve, the four inner layer flow channels provided in the inner layer 5 of the upper composite end plate are connected to the high-power flow channel or the low-power flow channel, so that the four areas of the bipolar plate 6 are connected to the high-power flow channel or the low-power flow channel.

[0046] In order to reasonably place the three flow channels and their corresponding branches, such as Figure 5As shown, the outer layer 3 of the upper composite end plate is provided with a parallel upper coolant flow channel layer 3-1 and an upper coolant flow channel second layer 3-2; the upper coolant flow channel layer 3-1 is provided with an upper composite end plate first flow channel 3-1-1, an upper composite end plate three-way control valve 3-1-2 and an upper composite end plate second flow channel 3-1-3; the four branch ports of the outlet of the first flow channel 3-1-1 of the upper composite end plate are marked as A, B, C, and D, respectively, and extend to the upper coolant flow channel second layer 3-2; the two branch ports of the outlet of the second flow channel 3-1-3 of the upper composite end plate are marked as E and G, respectively; (the interfaces of the branches F and H in the upper coolant flow channel layer 3-1 in the figure are retained for the convenience of processing technology and may not be required). The upper coolant flow channel second layer 3-2 has an upper composite end plate third flow channel 3-2-1 and an upper composite end plate two-way control valve 3-2-2; the two branch ports of the outlet of the upper composite end plate third flow channel 3-2-1 are marked as F and H respectively.

[0047] like Figure 3 As shown, the upper composite end plate inner layer 5 is connected to the upper composite end plate outer layer 3 by a sliding mechanism, forming a 2-position 12-way reversing valve, wherein 12-way represents 8 inlets and 4 outlets, the 8 inlets are connected to ports A, B, C, D, E, F, G, and H, respectively, and the 4 outlets are connected to 4 regions, respectively. The manual reversing valve is used to switch the flow directions in adjacent regions of the bipolar plate 6 from the same to different, which is used to switch the cooling mode of the fuel cell under high and low power. The lower composite end plate inner layer 7 is connected to the lower composite end plate outer layer 8 by a sliding mechanism, also forming a 2-position 12-way reversing valve, with the same structural principle.

[0048] Since the upper composite end plate inner layer 5 and the upper composite end plate outer layer 3 are symmetrical with the composite end plate inner layer 7 and the lower composite end plate outer layer 8, as shown in FIG. Figure 3 and Figure 6 As shown, a lower total coolant inlet 9 and a lower total coolant outlet 10 are provided on the outer layer 8 of the lower composite end plate; a lower composite end plate first flow channel 8-1-1, a lower composite end plate second flow channel 8-1-3 and a lower composite end plate third flow channel 8-2-1 are provided in the outer layer 8 of the lower composite end plate; a lower composite end plate three-way control valve 8-1-2 is installed in the outer layer 8 of the lower composite end plate, and the outlet of the lower composite end plate three-way control valve 8-1-2 is connected with the lower total coolant outlet 10, one inlet of the lower composite end plate three-way control valve 8-1-2 is connected with the first flow channel 8-1-1 of the lower composite end plate, and the other inlet of the lower composite end plate three-way control valve 8-1-2 is connected with the second flow channel 8-1-3 of the lower composite end plate; the lower total coolant inlet 9 is connected with one end of the third flow channel 8-2-1 of the lower composite end plate through the lower composite end plate two-way control valve 8-2-2.

[0049] In order to reasonably place the three flow channels and their corresponding branches, the outer layer 8 of the lower composite end plate is similarly Figure 6 As shown, the outer layer 8 of the lower composite end plate is provided with a first layer 8-1 and a second layer 8-2 of lower coolant flow channels in parallel; the first layer 8-1 of the lower coolant flow channel is provided with a first channel 8-1-1 of the lower composite end plate, a three-way control valve 8-1-2 of the lower composite end plate and a second channel 8-1-3 of the lower composite end plate; the four branch ports at the outlet of the first channel 8-1-1 of the lower composite end plate are marked as a, b, c and d respectively; the two branch ports at the outlet of the second channel 8-1-3 of the lower composite end plate are marked as e and g respectively; (the interfaces of branches f and g in the first layer 8-1 of the lower coolant flow channel in the figure are retained for the convenience of processing technology and may not be required). The second layer 8-2 of the lower coolant flow channel is provided with a third channel 8-2-1 of the lower composite end plate and a two-way control valve 8-2-2 of the lower composite end plate; the two branch ports at the outlet of the third channel 8-2-1 of the lower composite end plate are marked as f and g respectively. As shown Figure 3 As shown, the lower composite end plate inner layer 7 and the lower composite end plate outer layer 8 are connected by a sliding mechanism to form a 2-position 12-way reversing valve, wherein the 12-way represents 8 inlets and 4 outlets, the 8 inlets are respectively connected to ports a, b, c, d, e, f, g, and h, and the 4 outlets are respectively connected to 4 regions. The manual reversing valve switches the flow directions in adjacent regions of the bipolar plate 6 from the same to different, which is used to switch the cooling mode of the fuel cell under high and low power.

[0050] like Figure 2 As shown, the XY surface of the outer layer of the composite end plate is equipped with a total coolant inlet and a total coolant outlet, the diameters of the total coolant inlet and the total coolant outlet are 15mm-30mm, and the total coolant inlet is connected to the external deionized water tank for providing coolant. Taking the outer layer 3 of the composite end plate as an example, the upper coolant flow channel layer 3-1 is 10-15mm away from the XY surface of the upper composite end plate outer layer 3, and the flow channel widths of the upper composite end plate first flow channel 3-1-1 and the upper composite end plate second flow channel 3-1-3 in the upper coolant flow channel layer 3-1 are both 1-3mm; the upper coolant flow channel second layer 3-2 is 20-25mm away from the XY surface of the upper composite end plate outer layer 3, and the flow channel width of the upper composite end plate third flow channel 3-2-1 in the upper coolant flow channel second layer 3-2 is 1-3mm; the coolant interfaces of the upper composite end plate inner layer 5 and the composite end plate outer layer 3 are the same size and are connected to each other in different modes. The inner flow channel of the inner layer 5 of the upper composite end plate is connected to the corresponding area of ​​the bipolar plate 6, and the coolant is introduced into the coolant flow area of ​​the bipolar plate 6. Figure 7 As shown, the moving distance of the sliding track 12 of the outer layer 3 of the upper composite end plate is 0-Ymm, where Y is less than or equal to 20mm.

[0051] Figure 3 and Figure 4The control principle diagram of the present invention also includes a control system and a sensor. The temperature sensor is installed on both sides of the bipolar plate 6 to measure the temperature difference between the two ends of the bipolar plate 6. The control system selectively controls the actions of the three-way control valve, the two-way control valve and the sliding track according to the temperature difference, so as to effectively improve the temperature uniformity of the fuel cell stack, specifically:

[0052] like Figure 3 As shown, when the temperature difference Ca≤10°C or the working power of the fuel cell stack is <60% of the rated power (low power mode), the control system controls the upper composite end plate three-way control valve 3-1-2 to connect the upper total coolant inlet 1 with the upper composite end plate first flow channel 3-1-1, and the control system controls the upper composite end plate outer layer 3 and the upper composite end plate inner layer 5 to maintain their initial positions, that is, the upper composite end plate outer layer 3 and the upper composite end plate inner layer 5 do not slide; the control system controls the lower composite end plate outer layer 8 and the lower composite end plate inner layer 7 to maintain their initial positions, and the control system controls the lower composite end plate three-way control valve 8-1 -2 makes the lower total coolant outlet 10 connected with the first flow channel 8-1-1 of the lower composite end plate. At this time, the coolant enters the first flow channel 3-1-1 of the upper composite end plate from the upper total coolant inlet 1, and then enters the inner flow channel in the inner layer 5 of the upper composite end plate from A, B, C, and D, and then enters the 4 areas in the bipolar plate 6 respectively, and then enters the a, b, c, and d ports in the outer layer 8 of the lower composite end plate from the inner flow channel in the inner layer 7 of the lower composite end plate, and then passes through the first flow channel 8-1-1 of the lower composite end plate and the three-way control valve 8-1-2 of the lower composite end plate, and flows out from the lower total coolant outlet 10. The flow direction of the coolant in the 4 areas of the bipolar plate 6 is completely consistent at this time.

[0053] like Figure 4As shown, when the temperature difference Ca>10℃ or the stack operating power is ≥60% of the rated power (high power mode), the control system controls the upper composite end plate three-way control valve 3-1-2 to connect the upper total coolant inlet 1 with the upper composite end plate second flow channel 3-1-3, and the control system controls the upper composite end plate outer layer 3 and the upper composite end plate inner layer 5 to slide, that is, the 2-position 12-way reversing valve is reversed; the control system controls the upper composite end plate two-way control valve 3-2-2 to connect the upper total coolant outlet 2 with the upper composite end plate third flow channel 3-2-1; the control system controls the lower composite end plate outer layer 8 and the lower composite end plate inner layer 7 to slide, and the control system controls the lower composite end plate three-way control valve 8-1-2 to connect the lower total coolant outlet 10 with the lower composite end plate second flow channel 8-1-3, and the control system controls the lower The two-way control valve 8-2-2 of the composite end plate connects the lower total coolant inlet 9 with the third flow channel 8-2-1 of the lower composite end plate; for the convenience of explanation, the four areas in the bipolar plate 6 are set as Z1, Z2, Z3, and Z4 from top to bottom. At this time, there are two lines in different directions, line one: at this time, the coolant enters the second flow channel 3-1-3 of the upper composite end plate from the upper total coolant inlet 1, and then enters the corresponding inner layer flow channels in the inner layer 5 of the upper composite end plate from E and G, and then enters the two areas Z1 and Z3 in the bipolar plate 6 respectively, and then enters the corresponding e and g ports in the outer layer 8 of the lower composite end plate from the inner layer flow channel in the inner layer 7 of the lower composite end plate, and then passes through the second flow channel 8-1-3 of the lower composite end plate and the three-way control valve 8-1-2 of the lower composite end plate, and flows out from the lower total coolant outlet 10. Route 2: The coolant enters the third flow channel 3-2-1 of the lower composite end plate from the lower total coolant inlet 9, then enters the inner flow channel in the inner layer 7 of the lower composite end plate from f and h, then enters the two areas Z2 and Z4 in the bipolar plate 6 respectively, then enters the F and H ports in the outer layer 8 of the upper composite end plate from the corresponding inner flow channel in the inner layer 5 of the upper composite end plate, then passes through the third flow channel 3-2-1 of the upper composite end plate and the two-way control valve 3-2-2 of the upper composite end plate, and flows out from the upper total coolant outlet 2. The flow directions in the adjacent areas of the four areas Z1, Z2, Z3, and Z4 are opposite.

[0054] Example:

[0055] In this embodiment, the size of the bipolar plate 6 is 500mm*100mm*1mm, the outer layer of the composite end plate and the inner layer of the composite end plate are installed at both ends, the area of ​​the XY plane of the end plate is 600mm*150mm, the diameter of the total water inlet and the total water outlet of the composite end plate is 40mm, and the flow rate of the total water inlet is 1m / s. The bipolar plate 6 is provided with a total of 4 flow areas, each flow area includes a total of 4 flow channels, each flow channel is 600mm long and has a cross section of 1mm*0.8mm.

[0056] The embodiment consists of a 500*100*10 electrode plate and a 500*100*1 MEA membrane, such as Fig. 9As shown in the figure, in high power mode, the coolant medium is water, the material of the plate and MEA membrane is steel, the water inlet flow rate is 3m / s, the water inlet temperature is 20℃, and the calorific value of the MEA membrane is 500w / m 3 , the simulation results show that the temperature difference is 11.7℃.

[0057] like Fig.10 As shown in the figure, in the low power working mode, the cooling liquid medium is controlled to be water, the material of the plate and MEA membrane is steel, the water inlet flow rate is 3m / s, the water inlet temperature is 20℃, and the calorific value of the MEA membrane is 500w / m 3 ,The simulation shows that the temperature difference is 14.1℃, and the heat dissipation effect of the cross flow is improved by 20.51% compared with the unidirectional flow. Therefore, the heat dissipation requirements can be met in high-power working mode or when the temperature difference is greater than 10℃.

[0058] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0059] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A fuel cell stack with uniform temperature distribution, characterized in that: The invention comprises a bipolar plate (6) and a flow channel system located on both sides of the bipolar plate (6); the cooling liquid flow field of the bipolar plate (6) is divided into a plurality of regions, each region is provided with two connecting ports, and a plurality of internal flow channels connected to the two connecting ports in each region are provided between the two connecting ports; a connecting port in each region is connected to the flow channel system on one side, and another connecting port in each region is connected to the flow channel system on the other side; a valve for switching flow direction is provided in the flow channel system, and by controlling the flow channel systems on both sides, the flow directions in adjacent regions of the bipolar plate (6) are made the same or different.

2. The fuel cell stack with uniform temperature distribution according to claim 1, characterized in that: The flow channel system comprises a composite end plate inner layer, a composite end plate outer layer and a sliding mechanism; the composite end plate inner layer is mounted on the bipolar plate (6), and the flow channel of the composite end plate inner layer is connected to each area respectively; the composite end plate outer layer is mounted on the composite end plate inner layer by a sliding mechanism, and the flow direction of the coolant in the adjacent area is changed by moving the composite end plate outer layer, so as to realize the heat dissipation strategy.

3. The fuel cell stack with uniform temperature distribution according to claim 2, characterized in that: The outer layer of the composite end plate is provided with a first flow channel, a second flow channel and a third flow channel; the outer layer of the composite end plate is provided with two interfaces for the entry and exit of cooling liquid; one of the interfaces is connected to one end of the first flow channel and the second flow channel respectively through a three-way control valve, and the other interface is connected to one end of the third flow channel through a two-way control valve; a plurality of inner layer flow channels are provided in the inner layer of the composite end plate, and each inner layer flow channel is connected to a connecting port in an area of ​​the bipolar plate (6); the second flow channel and the third flow channel are high-power flow channels, and the first flow channel is a low-power flow channel; a sliding mechanism is provided between the inner layer of the composite end plate and the outer layer of the composite end plate, and is used to switch a plurality of inner layer flow channels to be connected to the high-power flow channel or the low-power flow channel by sliding between the inner layer of the composite end plate and the outer layer of the composite end plate.

4. The fuel cell stack with uniform temperature distribution according to claim 3, characterized in that: The inner layer of the composite end plate and the outer layer of the composite end plate are connected by a sliding mechanism to form a 2-position 3n-way reversing valve, where n is equal to the number of regions in the bipolar plate (6). By controlling the valve for switching the flow direction, the flow directions in adjacent regions of the bipolar plate (6) are switched from being the same to being different, thereby switching the cooling mode of the fuel cell under high and low power.

5. The fuel cell stack with uniform temperature distribution according to claim 3, characterized in that: The coolant flow field of the bipolar plate (6) is divided into n areas, and the corresponding first flow channel outlet is divided into n branches, which are low-power flow channel branches; the second flow channel outlet is divided into n / 2 branches, and the third flow channel outlet is divided into n / 2 branches. The n / 2 branches of the second flow channel outlet and the n / 2 branches of the third flow channel outlet are high-power flow channel branches; by controlling the sliding between the inner layer of the composite end plate and the outer layer of the composite end plate and controlling the switching of the three-way control valve and the two-way control valve, the n areas are connected to the high-power flow channel or the low-power flow channel.

6. The fuel cell stack with uniform temperature distribution according to claim 3, characterized in that: Two cooling channel layers are arranged in the outer layer of the composite end plate, the first cooling channel layer has a first channel, a second channel and a three-way control valve, and the second cooling channel layer has a third channel and a two-way control valve.

7. A fuel cell stack with uniform temperature distribution according to any one of claims 3 to 6, characterized in that: It also includes a control system and a sensor, wherein the sensor is used to measure the temperature difference on both sides of the bipolar plate (6) or the operating power of the fuel cell stack; the control system selectively controls the switching of the three-way control valve and the two-way control valve in the flow channel system according to the temperature difference on both sides of the bipolar plate (6) fed back by the sensor, and selectively controls the sliding of the inner layer and the outer layer of the composite end plate.

8. The fuel cell stack with uniform temperature distribution according to claim 7, characterized in that: The sensor is a temperature sensor used to measure the temperature difference on both sides of the bipolar plate (6); the flow channel systems on both sides of the bipolar plate (6) are respectively an upper flow channel system and a lower flow channel system; the upper flow channel system and the lower flow channel system are respectively provided with an inlet and an outlet When the temperature difference Ca on both sides of the bipolar plate (6) is less than or equal to 10° C., the control system controls the three-way control valve of the upper flow channel system so that the inlet of the upper flow channel system is connected to its low-power flow channel, and the control system controls the three-way control valve of the lower flow channel system so that the outlet of the lower flow channel system is connected to its low-power flow channel, so that a one-way flow channel is formed between the inlet of the upper flow channel system, the low-power flow channel of the upper flow channel system, the bipolar plate (6), the low-power flow channel of the lower flow channel system and the outlet of the lower flow channel system; When the temperature difference Ca on both sides of the bipolar plate (6) is greater than 10°C, the control system controls the three-way control valve of the upper flow channel system to connect the inlet of the upper flow channel system with its second flow channel, the control system controls the two-way control valve of the upper flow channel system to connect the outlet of the upper flow channel system with its third flow channel, the control system controls the three-way control valve of the lower flow channel system to connect the outlet of the lower flow channel system with its second flow channel, the control system controls the two-way control valve of the lower flow channel system to connect the inlet of the lower flow channel system with its third flow channel, and the control system controls the composite end plate inner layer and the composite end plate outer layer of the upper flow channel system and the lower flow channel system to slide, thereby forming a one-way flow channel in one direction between the inlet of the upper flow channel system, the second flow channel of the upper flow channel system, the bipolar plate (6), the second flow channel of the lower flow channel system and the outlet of the lower flow channel system, and forming a one-way flow channel in another direction between the inlet of the lower flow channel system, the third flow channel of the lower flow channel system, the bipolar plate (6), the third flow channel of the upper flow channel system and the outlet of the upper flow channel system.

9. The fuel cell stack with uniform temperature distribution according to claim 7, characterized in that: The sensor is a power sensor used to measure the working power of the fuel cell stack; the flow channel systems on both sides of the bipolar plate (6) are respectively an upper flow channel system and a lower flow channel system; the upper flow channel system and the lower flow channel system are respectively provided with an inlet and an outlet When the working power of the fuel cell stack is ≤60% of the rated power, the control system controls the three-way control valve of the upper flow channel system to connect the inlet of the upper flow channel system with its low-power flow channel, and the control system controls the three-way control valve of the lower flow channel system to connect the outlet of the lower flow channel system with its low-power flow channel, so that a one-way flow channel is formed between the inlet of the upper flow channel system, the low-power flow channel of the upper flow channel system, the bipolar plate (6), the low-power flow channel of the lower flow channel system and the outlet of the lower flow channel system; When the working power of the fuel cell stack is greater than 60% of the rated power, the control system controls the three-way control valve of the upper flow channel system to connect the inlet of the upper flow channel system with its second flow channel, the control system controls the two-way control valve of the upper flow channel system to connect the outlet of the upper flow channel system with its third flow channel, the control system controls the three-way control valve of the lower flow channel system to connect the outlet of the lower flow channel system with its second flow channel, the control system controls the two-way control valve of the lower flow channel system to connect the inlet of the lower flow channel system with its third flow channel, and the control system controls the composite end plate inner layer and the composite end plate outer layer of the upper flow channel system and the lower flow channel system to slide, so that a one-way flow channel in one direction is formed between the inlet of the upper flow channel system, the second flow channel of the upper flow channel system, the bipolar plate (6), the second flow channel of the lower flow channel system and the outlet of the lower flow channel system, and a one-way flow channel in another direction is formed between the inlet of the lower flow channel system, the third flow channel of the lower flow channel system, the bipolar plate (6), the third flow channel of the upper flow channel system and the outlet of the upper flow channel system.

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