Device and method for testing permeability of graphite bipolar plate

Abstract

The invention discloses a permeability testing device and method for a graphite bipolar plate. The testing device comprises a sealing clamping tool which comprises an upper tool and a lower tool which are used for clamping a graphite bipolar plate sample to be tested, a sealed upper cavity is formed between the sample and the upper tool, and a sealed lower cavity is formed between the sample and the lower tool; the liquid injector is used for accommodating liquid and is communicated to one of the upper cavity and the lower cavity so as to fill one of the upper cavity and the lower cavity with the liquid; and a driving mechanism connected to the liquid injector in a power transmission manner to apply power to the liquid in the liquid injector so that the liquid is filled in one of the upper chamber and the lower chamber, and further apply power so that the liquid is kept as a pressurized liquid in the upper chamber or the lower chamber.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cell, in particular to a kind of graphite bipolar plate permeability testing device and method. BACKGROUND

[0002] Graphite bipolar plate is a widely used component in fuel cell stack. As the core component of fuel cell stack, bipolar plate needs to have excellent water and gas isolation function, so it needs to have very good anti-permeability. Currently, graphite bipolar plate on the market is usually a composite material combined with graphite and resin, but due to different types of graphite and resin, different manufacturing processes, the permeability of graphite bipolar plate is different. Currently, the test of permeability mainly detects gas permeability, but due to the compressibility of gas, the actual flow of gas passing through the sample cannot be accurately obtained. In addition, some methods in the prior art, such as using dyeing agent to analyze the leakage position, but it can only qualitatively determine whether there is leakage, and cannot obtain specific permeability parameters.

[0003] Therefore, it is necessary to provide a technical scheme to overcome the deficiencies in the prior art. SUMMARY

[0004] The present application overcomes the defects of the prior art and provides a graphite bipolar plate permeability testing device and method, which can accurately and efficiently measure the permeability of graphite bipolar plate.

[0005] The present application is implemented by the following technical scheme: a graphite bipolar plate permeability testing device, comprising: A sealing clamping tool, comprising an upper tool and a lower tool for clamping the graphite bipolar plate sample to be tested therebetween, so that the sample forms a sealed upper chamber with the upper tool and a sealed lower chamber with the lower tool; A liquid injector for containing liquid and communicating with one of the upper chamber and the lower chamber to fill the liquid into one of the upper chamber and the lower chamber; and A driving mechanism power-transmissively connected to the liquid injector to apply power to the liquid in the liquid injector so that the liquid is filled in one of the upper chamber and the lower chamber, and further apply power to keep the liquid as pressurized liquid in the upper chamber or the lower chamber.

[0006] As a further improved technical scheme, the sealing clamping tool includes an upper pressure gauge for measuring the pressure in the upper chamber and a lower pressure gauge for measuring the pressure in the lower chamber.

[0007] As a further improved technical scheme, the inner side surfaces of the upper tool and the lower tool each include a shunt structure of the same configuration.

[0008] As a further improved technical solution, the liquid injector and the sealing clamping tool are connected through a metal pipe.

[0009] As a further improved technical solution, the driving mechanism comprises a stepper motor and a screw drive assembly driven by the stepper motor, wherein the stepper motor is configured to be driven by a controller 16 times, and the driving distance of each micro-step is 0.1-0.2 μm.

[0010] As a further improved technical solution, the liquid injector comprises a measuring cylinder and a piston, the measuring range of the measuring cylinder is 8-20 ml, and the working pressure of the sealing rubber ring of the piston is 5-10 Mpa.

[0011] The present application also realizes the permeability test method of the graphite bipolar plate by the following technical solution: a test device for testing the permeability of a graphite bipolar plate, the test device comprises a sealing clamping tool and a liquid injector, the sealing clamping tool comprises an upper chamber and a lower chamber, and the liquid injector is connected to the upper chamber and the lower chamber of the sealing clamping tool through a metal pipe. S1. One of the upper chamber and the lower chamber of the sealing clamping tool is filled with liquid, and power is further applied to keep the liquid in the chamber as pressurized liquid; S2. After a preset time, the liquid volume passing through the graphite bipolar plate sample to be tested and the pressure difference on both sides of the graphite bipolar plate sample to be tested are obtained, and the permeability is calculated according to the following formula:

[0012] Wherein, K is the permeability, t is the preset time, Q is the liquid volume passing through the graphite bipolar plate sample to be tested within the time t, L is the thickness of the graphite bipolar plate sample to be tested; A is the cross-sectional area of the graphite bipolar plate sample to be tested; ΔP is the pressure difference on both ends of the graphite bipolar plate sample to be tested.

[0013] As a further improved technical solution, the S1 step specifically comprises: S11. Large-flow liquid supply to fill the chamber with liquid and make the pressure in the chamber reach the set target pressure; S12. Small-flow liquid supply to the chamber in a way to keep the pressure in the chamber constant at the target pressure.

[0014] As a further improved technical solution, the target pressure is 200-300 Kpa.

[0015] As a further improved technical solution, the S1 step specifically comprises: S11. Large-flow liquid supply to fill the chamber with liquid and make the pressure in the chamber reach the set target pressure; S12. Small-flow liquid supply to the chamber in a way to keep the pressure in the chamber constant at the target pressure.

[0016] The permeability testing device of the graphite bipolar plate provided by the application uses liquid as the testing medium, and can more accurately reflect the actual flow through the sample due to the incompressibility of the liquid, thereby avoiding the error caused by the compressibility of the gas in the prior art, and obtaining more accurate permeability parameters. At the same time, by accurately controlling the filling and pressurizing process of the liquid and accurately measuring the related parameters, the accuracy of the test is further improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a system structure schematic diagram of the permeability testing device of the graphite bipolar plate of the application.

[0018] Figure 2 is an exploded schematic diagram of the sealing and clamping tool in the permeability testing device of the graphite bipolar plate of the application.

[0019] Figure 3 is a three-dimensional structure diagram of the lower tool in the permeability testing device of the graphite bipolar plate of the application.

[0020] Figure 4 is a flowchart of an embodiment of the permeability testing method of the graphite bipolar plate of the application.

[0021] Figure 5 is a flowchart of another embodiment of the permeability testing method of the graphite bipolar plate of the application.

[0022] Reference signs: 1, driving mechanism; 11, stepper motor; 12, bracket; 13, screw rod; 14, screw rod nut; 15, push rod; 2, liquid injector; 3, metal connecting pipe; 4, sealing and clamping tool; 41, upper tool; 42, lower tool; 421, liquid inlet groove; 422, shunt structure; 43, upper pressure gauge; 44, lower pressure gauge; 45, upper sealing ring; 46, lower sealing ring; 5, graphite bipolar plate sample to be tested. DETAILED DESCRIPTION

[0023] In order to have a clearer understanding of the technical features, objectives and effects of the application, the specific embodiments of the application will be described in detail with reference to the accompanying drawings.

[0024] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments of the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0025] The application relates to the technical field of fuel cells, in particular to a permeability testing device and method for graphite bipolar plates.

[0026] Referring to Figures 1 to 3 As shown in the figure, the application provides a permeability testing device for graphite bipolar plates, which comprises a driving mechanism 1, a liquid injector 2 and a sealing and clamping tool 4. The sealing and clamping tool 4 comprises an upper tool 41 and a lower tool 42 for clamping a graphite bipolar plate sample 5 to be tested therebetween, so that an upper chamber is formed between the sample and the upper tool 41, and a lower chamber is formed between the sample and the lower tool 42. The liquid injector 2 is used for containing liquid and is connected to one of the upper chamber and the lower chamber, so as to fill the liquid into the one of the upper chamber and the lower chamber. The driving mechanism 1 is power-transmissively connected to the liquid injector 2, so as to apply power to the liquid in the liquid injector 2, so that the liquid is filled into the one of the upper chamber and the lower chamber, and further apply power to keep the liquid as pressurized liquid in the upper chamber or the lower chamber.

[0027] The permeability testing device for graphite bipolar plates provided by the application mainly comprises the sealing and clamping tool 4, the liquid injector 2 and the driving mechanism 1. The working principle is that the sealing and clamping tool 4 is used for fixing and forming the upper chamber and the lower chamber of the graphite bipolar plate sample 5 to be tested, the liquid injector 2 is used for containing liquid and connecting the liquid to one of the upper chamber and the lower chamber, and the driving mechanism 1 is used for applying power to the liquid in the liquid injector 2, so that the liquid is filled into the selected chamber and kept in a pressurized state. The permeability of the graphite bipolar plate is calculated by measuring the liquid volume passing through the sample and the pressure difference on both sides of the sample within a certain time. The testing method adopts liquid as the testing medium. Compared with gas, the liquid is incompressible, can more accurately reflect the actual flow passing through the sample, and thus more accurate permeability parameters are obtained.

[0028] In the embodiment, the sealing clamping tool 4 comprises an upper tool 41 and a lower tool 42, and the graphite bipolar plate sample 5 to be tested is clamped between the upper tool 41 and the lower tool 42. The upper tool 41 and the lower tool 42 are tightly fitted, so that a sealed upper chamber is formed between the sample and the upper tool 41, and a sealed lower chamber is formed between the sample and the lower tool 42. Such a sealing structure can ensure that the liquid does not leak during the test, and ensure the accuracy of the test. In the embodiment, the contact surfaces of the upper tool 41 and the lower tool 42 are designed as high-precision planes, and are provided with sealing materials such as rubber sealing rings and the like to enhance the sealing effect. In the embodiment, the upper tool 41 is provided with an upper sealing ring 45 between the upper tool 41 and the graphite bipolar plate sample 5 to be tested, and the lower tool 42 is provided with a lower sealing ring 46 between the lower tool 42 and the graphite bipolar plate sample 5 to be tested. The sealing ring is made of liquid silicone rubber material or EPDM material with good sealing performance. The upper and lower sealing rings 45, 46 function to isolate the high-pressure water from the outside world, so that the high-pressure water can only pass through the sample to be tested.

[0029] In the embodiment, further, the inner side surfaces of the upper tool 41 and the lower tool 42 each comprise a flow distribution structure 422. The upper tool 41 and the lower tool 42 are both designed with the flow distribution structure 422, so that the high-pressure liquid can quickly and fully cover the surface of the graphite bipolar plate sample 5 to be tested. The flow distribution structures 422 on the upper and lower tools are the same, so that the sample maintains the same external conditions on both sides except for the change in pressure difference. The flow distribution structure 422 functions to quickly and uniformly distribute the liquid on the surface of the sample when the liquid enters the chamber, so as to avoid local concentration of the liquid and cause inaccurate test results. In the embodiment, the flow distribution structure 422 is in the form of densely arranged horizontal grooves and vertical grooves, and the liquid gradually disperses and uniformly covers the entire surface of the sample when passing through the flow distribution structure 422, so as to ensure that the penetration process of the liquid on the entire sample is uniform. Please refer to Figure 3 As shown in the figure, the lower tool 42 is taken as an example, and the inner side surface of the lower tool 42 is provided with a liquid inlet groove 421 extending along the diameter direction thereof. The liquid inlet groove 421 functions to provide a passage for the liquid to enter the lower chamber, so that the liquid can smoothly flow into the chamber and contact the sample. The multiple inlets of the flow distribution structure 422 are in communication with the liquid inlet groove 421.

[0030] In order to monitor the pressure conditions in the upper chamber and the lower chamber in real time, the sealing clamping tool 4 is further provided with an upper pressure gauge 43 and a lower pressure gauge 44. The upper pressure gauge 43 is used to measure the pressure in the upper chamber, and the lower pressure gauge 44 is used to measure the pressure in the lower chamber. Through the two pressure gauges, the operator can intuitively understand the pressure change in the chamber, so as to better control the test process and calculate the results.

[0031] Please continue to refer to Figure 1As shown, in the embodiment, the liquid injector 2 includes a measuring cylinder and a piston. The measuring cylinder is used to contain the liquid required for testing, and the measuring range is 8-20 ml, which can meet the needs of most graphite bipolar plate permeability tests. The piston is used to control the ejection of the liquid, and the volume of the liquid in the measuring cylinder is changed by the movement of the piston. A sealing rubber ring is provided on the piston, and the working pressure of the sealing rubber ring is 5-10 MPa, which can ensure that the liquid does not leak from the piston under high pressure, and ensure the accuracy of the test. In the embodiment, the material of the measuring cylinder is 304 stainless steel, and the sealing rubber ring of the piston is Viton fluororubber which has good sealing performance and can meet the requirements of high and low temperature use. In the embodiment, the liquid injector 2 and the sealing clamping tool 4 are connected by a metal pipe 3. The metal pipe 3 has good sealing property and pressure resistance, can withstand the pressure generated by the liquid during the test, and the volume remains stable and does not change due to the pressurized liquid, so as to ensure the accuracy of the liquid flow calculation.

[0032] In the embodiment, the driving mechanism 1 includes a bracket 12, a stepping motor 11, and a lead screw transmission assembly driven by the stepping motor 11. The bracket 12 is used to fix the stepping motor 11 and the lead screw transmission assembly, and ensure the stability of the whole driving mechanism 1. In some embodiments, the material of the bracket 12 can be selected from high-strength metal materials such as aluminum alloy, etc., to ensure that the driving mechanism 1 does not deform or displace during the test, affecting the accuracy of the test. In the embodiment, the lead screw transmission assembly includes a lead screw 13, a lead screw nut 14 and a push rod 15. The stepping motor 11 rotates under the control of the controller, drives the rotation of the lead screw 13, and the rotary motion of the lead screw 13 drives the linear movement of the lead screw nut 14 connected with it, thereby driving the movement of the push rod 15 connected with the lead screw nut 14. The push rod 15 is connected with the piston of the liquid injector 2, and the movement of the piston is controlled by the movement of the push rod 15, thereby realizing the application of power to the liquid in the liquid injector 2.

[0033] In the embodiment, the stepper motor 11 is configured to be controlled by the controller 16 with 16 subdivision driving control, and the pushing distance of each micro-step is 0.1-0.2 μm. The stepper motor 11 is configured to be controlled by the controller 16 with 16 subdivision driving control, and the pushing distance of each micro-step is 0.1-0.2 μm. Such fine control method can make the driving mechanism 1 more accurate in applying power to the liquid injector 2, so as to realize accurate control of the liquid filling and pressurizing process. Specifically, the distance of the piston pushed by each micro-step is 0.156 microns, and the minimum linear speed of the stepper motor 11 is 5 microns per minute, so as to accurately control the flow of the liquid pushed by the push rod 15 in the liquid injector 2. For example, in the test process, the pressure and flow of the liquid need to be adjusted according to different test requirements. Through the 16 subdivision driving control, the number of rotation steps of the stepper motor 11 can be accurately controlled, and then the moving distance of the push rod 15 can be accurately controlled through the structure-accurate screw rod transmission assembly, so as to realize accurate adjustment of the liquid pressure and flow.

[0034] The application further provides a permeability test method of a graphite bipolar plate, which is executed by the test device. The test method comprises the following steps: S1. filling the liquid in one of the upper chamber and the lower chamber of the sealing and clamping tool 4 and further applying power to make the liquid in the chamber as pressurized liquid; S2. after maintaining for a preset time, obtaining the liquid volume passing through the graphite bipolar plate sample 5 to be tested and the pressure difference on both sides of the graphite bipolar plate sample 5 to be tested, and calculating the permeability according to the following formula: ; wherein K is the permeability, t is the preset time, Q is the liquid volume passing through the sample within the time t, L is the thickness of the graphite bipolar plate sample 5 to be tested, A is the cross-sectional area of the graphite bipolar plate sample 5 to be tested, and ΔP is the pressure difference on both ends of the graphite bipolar plate sample 5 to be tested. Such test method can obtain accurate graphite bipolar plate permeability by accurately controlling the liquid filling and pressurizing process and accurately measuring the related parameters.

[0035] Further, in one embodiment, step S1 specifically includes: S11. Supplying liquid at a high flow rate to fill the chamber with liquid and bring the pressure in the chamber to a set target pressure; S12. Supplying liquid to the chamber at a low flow rate to maintain the pressure in the chamber at the target pressure. Specifically, at the start of the test, the drive mechanism 1 pushes the piston of the liquid injector 2 at a relatively fast speed, causing the liquid to quickly enter the chamber, rapidly fill the chamber, and raise the pressure in the chamber to the set target pressure. In some embodiments, the target pressure is between 200 and 300 kPa, a pressure range that can meet the needs of most graphite bipolar plate permeability tests without damaging the sample. Once the pressure in the chamber reaches the target pressure, the drive mechanism 1 adjusts its power output to continue supplying liquid to the chamber at a lower flow rate, ensuring that the pressure in the chamber remains at the target pressure. This is because during the test, the liquid will flow through the sample at a certain rate; if the liquid is not replenished in time, the pressure in the chamber will gradually decrease, affecting the accuracy of the test results. By supplying liquid at a low flow rate, the pressure in the chamber can be precisely controlled, ensuring the stability of the test.

[0036] like Figure 4 The diagram illustrates the specific operating procedure for the constant pressure mode. First, a graphite plate sample is cut and installed into the sealing clamping fixture 4. The liquid injector 2 is installed onto the stepper motor 11. The sealing clamping fixture 4 and the liquid injector 2 are connected, and the rapid flow rate parameters, slow flow rate parameters, and target pressure value of the lower fixture 42 are set. Then, the device is turned on, entering the rapid flow stage, allowing the liquid to fill the lower chamber formed between the lower fixture 42 and the sample, and the pressure value reaches the preset target pressure value. The rapid flow stage ends, and the flow rate is read as Q1. Next, the slow flow stage begins, maintaining a constant target pressure value. If leakage occurs, the pressure will decrease, and the slow flow stage will resume, continuing to increase the pressure to the target value. After maintaining this for 60 minutes, the flow rate value Q2 is measured, and the pressure P1 of the lower fixture 42 and the pressure P2 of the upper fixture 41 are recorded. The experiment concludes, and data analysis is performed.

[0037] Furthermore, in another embodiment, step S1 specifically includes: S11. Supplying liquid at a high flow rate to fill the chamber with liquid and bring the pressure in the chamber to a set target pressure; S12. Supplying liquid to the chamber at a low flow rate while maintaining a constant flow rate. That is, in this embodiment, step S1 also first performs step S11, i.e., supplying liquid at a high flow rate to fill the chamber with liquid and bring the pressure in the chamber to a set target pressure. Then step S12 changes to supplying liquid to the chamber at a low flow rate while maintaining a constant flow rate. The principle of this method is that by maintaining a constant flow rate, the permeability of the graphite bipolar plate can be calculated by measuring the pressure change over time and the volume of liquid passing through the sample. This method is suitable for some testing scenarios with specific research needs regarding pressure changes.

[0038] like Figure 5 The diagram illustrates the specific operating procedure for the constant flow mode. First, a graphite plate sample is cut and installed into the sealing clamping fixture 4. The liquid injector 2 is then mounted onto the stepper motor 11. The sealing clamping fixture 4 and the liquid injector 2 are connected, and the rapid flow parameters, slow flow parameters, and target pressure value of the lower fixture 42 are set. The device is then turned on, entering the rapid flow stage, filling the lower fixture 42 with liquid until the pressure reaches the preset target pressure value. The rapid flow stage ends, and the flow rate is read as Q1. Next, the slow flow stage begins, maintaining a constant slow flow rate for 60 minutes. The flow rate value Q2, pressure P1 in the lower fixture 42, and pressure P2 in the upper fixture 41 are then measured. The experiment concludes, and data analysis is performed.

[0039] During the test run, high-pressure liquid enters the lower fixture 42 through the pipeline. Since a filling process is required for the high-pressure liquid to enter the lower fixture 42, this stage is defined as the rapid flow stage. Simultaneously, the pressure in the lower fixture 42 increases over time; therefore, before the sample test, a constant flow rate is used to obtain the pressure rise curve of the lower fixture 42. The flat inflection point of the curve is defined as the preset pressure for the test. Because samples exhibit varying permeability, ranging from almost completely impermeable to highly permeable materials, a constant flow rate mode is suitable for materials with high permeability, while a constant pressure mode is suitable for materials with very low permeability. The constant time can be 60 minutes, 120 minutes, or longer, depending on the material. The liquid used can be incompressible liquids such as deionized water or coolant. This test apparatus is not limited to measuring bipolar materials; it can also be used to measure other types of materials with porous structures. Additionally, in some embodiments, liquid can be introduced into the upper fixture 41, with the lower fixture 42 serving as a cavity, allowing the liquid to permeate from the upper fixture 41 to the lower fixture 42.

[0040] After keeping for the preset time length, the liquid volume passing through the graphite bipolar plate sample 5 and the pressure difference on both sides of the sample need to be accurately measured. The liquid volume can be measured by setting an accurate scale on the liquid injector 2 or using a high-precision flow meter. The pressure difference can be measured by directly reading the pressures in the upper chamber and the lower chamber through the upper pressure gauge 43 and the lower pressure gauge 44, and then calculating the difference between the two. The measured liquid volume Q, the preset time length t, the sample thickness L, the sample cross-sectional area A, and the pressure difference ΔP are substituted into the permeability calculation formula The permeability of the graphite bipolar plate can be calculated.

[0041] As can be seen from the above description of the specific embodiments, the present application uses liquid as the test medium. Since the liquid is incompressible, it can more accurately reflect the actual flow passing through the sample. Compared with the prior art which uses gas for testing, the error caused by the compressibility of the gas is avoided, so that more accurate permeability parameters are obtained. At the same time, by accurately controlling the filling and pressurizing process of the liquid and accurately measuring the related parameters, the accuracy of the test is further improved.

[0042] The test device of the present application has a reasonable structure, and the connection and operation between the components are simple and easy to understand. The driving mechanism 1 uses a stepper motor 11 and a screw rod transmission assembly, which realizes the automatic operation of the liquid injector 2 through the accurate control of the controller, reduces the error and labor intensity of manual operation. The test method steps are clear, and the operator only needs to operate according to the specified steps to complete the permeability test. Each component of the test device is made of high-strength, pressure-resistant materials such as metal pipes and brackets, which ensures the stability and reliability of the equipment during testing. The 16-subdivision driving control and accurate mechanical transmission structure of the driving mechanism 1 make the power applied to the liquid injector more stable and accurate, avoiding the test error caused by unstable equipment.

[0043] The test device and method of the present application are suitable for permeability testing of graphite bipolar plates of different types and different manufacturing processes. At the same time, by adjusting the test parameters such as target pressure and preset time length, different test requirements and standards can also be met.

[0044] In summary, the permeability test device and method for graphite bipolar plates of the present application have the advantages of high test accuracy, simple operation, wide application range, and good equipment stability, which can effectively solve the problems existing in the prior art and provide a reliable technical solution for permeability testing of graphite bipolar plates. The present application scheme can provide valuable permeability research quantitative data for graphite bipolar plate raw material selection and formula development, and can help enterprises to accelerate the development of graphite bipolar plate materials, shorten the research and development cycle, and provide protection for the reliability of bipolar plates.

[0045] The present application is illustrated by way of several specific embodiments, and those skilled in the art will appreciate that various modifications and equivalents can be made without departing from the scope of the present application. In addition, various modifications can be made to the present application for particular situations or specific circumstances without departing from the scope of the present application. Accordingly, the present application is not limited to the specific embodiments disclosed, but should be construed to include all embodiments falling within the scope of the claims of the present application.

Claims

1. A permeability testing device for a graphite bipolar plate, characterized in that, The testing apparatus includes: A sealing clamping fixture includes an upper fixture and a lower fixture for clamping a graphite bipolar plate sample to be tested therein, such that the sample forms a sealed upper chamber with the upper fixture and a sealed lower chamber with the lower fixture. A liquid injector for containing liquid and communicating with one of the upper and lower chambers to fill the upper and lower chambers with liquid; and A drive mechanism, powerably connected to the liquid injector, applies power to the liquid within the liquid injector such that the liquid is filled into one of the upper and lower chambers, and further applies power to maintain the liquid as pressurized liquid in the upper or lower chamber.

2. The permeability testing device for graphite bipolar plates as described in claim 1, characterized in that, The sealing clamping fixture includes an upper pressure gauge for measuring the pressure in the upper chamber and a lower pressure gauge for measuring the pressure in the lower chamber.

3. The permeability testing device for graphite bipolar plates as described in claim 1, characterized in that, The inner surfaces of both the upper and lower tooling include the same flow-diverting structure.

4. The permeability testing device for graphite bipolar plates as described in claim 1, characterized in that, The liquid syringe and the sealing clamping fixture are connected by a metal tube.

5. The permeability testing device for graphite bipolar plates as described in any one of claims 1 to 4, characterized in that, The drive mechanism includes a stepper motor and a lead screw drive assembly driven by the stepper motor, wherein the stepper motor is configured to be driven by a controller in 16 microsteps, and the advance distance of each microstep is 0.1~0.2μm.

6. The permeability testing device for graphite bipolar plates as described in any one of claims 1 to 4, characterized in that, The liquid syringe includes a measuring cylinder and a piston. The measuring cylinder has a volume of 8-20 ml, and the piston's sealing ring has a working pressure of 5-10 MPa.

7. A method for testing the permeability of a graphite bipolar plate, characterized in that, The method is performed by the testing apparatus according to any one of claims 1 to 6, and the testing method includes the following steps: S1. Fill one of the upper and lower chambers of the sealing clamping fixture with liquid and further apply power to keep the liquid pressurized in the chamber; S2. After maintaining the preset time, obtain the liquid volume passing through the graphite bipolar plate sample to be tested, as well as the pressure difference across the graphite bipolar plate sample to be tested, and calculate the permeability according to the following formula: ； Where K is the permeability, t is the preset time, Q is the liquid volume passing through the graphite bipolar plate sample under test within time t, L is the thickness of the graphite bipolar plate sample under test, A is the cross-sectional area of ​​the graphite bipolar plate sample under test, and ΔP is the pressure difference between the two ends of the graphite bipolar plate sample under test.

8. The permeability testing method for graphite bipolar plates as described in claim 7, characterized in that, The S1 step specifically includes: S11. A high-flow-rate liquid supply is used to fill the chamber with liquid and to bring the pressure in the chamber to a set target pressure. S12. Liquid is supplied to the chamber at a low flow rate in a manner that aims to keep the pressure inside the chamber constant.

9. The permeability testing method for a graphite bipolar plate as described in claim 8, characterized in that, The target pressure is between 200 and 300 kPa.

10. The permeability testing method for a graphite bipolar plate as described in claim 7, characterized in that, The S1 step specifically includes: S11. A high-flow-rate liquid supply is used to fill the chamber with liquid and to bring the pressure in the chamber to a set target pressure. S12. Supply liquid to the chamber at a small flow rate in a manner that keeps the liquid supply flow rate constant.

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