Device and method for measuring gas-liquid relative permeability of gas diffusion layer of fuel cell

Abstract

The invention belongs to the technical field of fuel cells, and relates to a device and method for measuring gas-liquid relative permeability of a gas diffusion layer of a fuel cell, and the device comprises a gas source, a liquid flow pump, an upper test box body and a lower test box body, the air source is communicated to the inner cavity of the lower test box body, and the liquid flow pump is communicated to the inner cavity of the upper test box body; the upper test box body is buckled on the lower test box body, a permeation clamp is isolated between an opening of the upper test box body and an opening of the lower test box body, a through hole is formed in the permeation clamp, and a to-be-tested gas diffusion layer mounted in a clamping position transversely isolates a fluid channel in the through hole; a cup opening of the gas receiving cup directly faces an upper opening of the through hole, and a cylinder opening of the water receiving measuring cylinder directly faces a lower opening of the through hole; only one device is used, the absolute permeability of gas and liquid of the gas diffusion layer can be measured, the gas-liquid relative permeability can be measured, the actual working condition of gas-liquid convection of the fuel cell can be simulated, operation is easy and convenient, the measurement cost is saved, and experimental errors are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cells and relates to a device and method for measuring the gas-liquid relative permeability of a fuel cell gas diffusion layer. Background Art

[0002] A fuel cell (FC) is an energy conversion device that converts chemical energy stored in fuel and oxidant directly into electrical energy in an electrochemical manner. Proton exchange membrane fuel cell (PEMFC) is a low-temperature hydrogen fuel cell. Compared with traditional energy devices, it has the advantages of low operating temperature, high energy conversion efficiency and relatively long life. It is one of the most promising devices to replace traditional energy devices. PEMFC is mainly composed of bipolar plates (BP) and membrane electrode assembly (MEA). The bipolar plates are the flow field that transports the reaction gas to the fuel cell and outputs liquid water. The membrane electrode includes a proton exchange membrane (PEM), a cathode and an anode. The proton exchange membrane plays the role of conducting protons and separating the cathode and anode reactions. The cathode and anode are usually porous structures, consisting of a gas diffusion layer (GDL) and a catalyst layer (CL). The gas diffusion layer acts as a bridge between the flow field and the membrane electrode, and plays a key role in material transfer and water management.

[0003] As an important component of proton exchange membrane fuel cells, the gas diffusion layer is usually made of a conductive material with micron-level pores. The gas diffusion layer provides a channel for gas and protons, supports the catalyst layer, and discharges the water generated by the reaction from the inside of the battery. If the hydrophilicity of the gas diffusion layer is too high, liquid water will block the pores, causing the battery to be flooded, hindering the mass transfer of the reaction gas to the reaction site, and affecting the battery performance. Therefore, it is necessary to add hydrophobic agents such as polytetrafluoroethylene during the preparation of the gas diffusion layer to regulate its hydrophobicity. However, the addition of hydrophobic agents will reduce the porosity of the gas diffusion layer, reduce the fluid transmission space, and reduce the gas-liquid permeability. In addition to wettability and porosity, parameters such as pore size and thickness of the gas diffusion layer will also affect its mass transfer performance. Therefore, it is very important to reasonably regulate the structural parameters of the gas diffusion layer for the efficient operation of PEMFC. Permeability is an important indicator for evaluating the mass transfer performance of the gas diffusion layer. Therefore, the development of permeability measurement devices and methods is of great significance for regulating the structure of the gas diffusion layer so that it has a suitable gas-liquid mass transfer capacity.

[0004] The prior art has done some research on the permeability measurement of the gas diffusion layer of fuel cells. For example, in the invention application with application number: CN202010763237.0 and invention name: Method and device for measuring the permeability and diffusion coefficient of the gas diffusion layer for fuel cells, the gas permeability and diffusion coefficient of the gas diffusion layer in the thickness direction and in-plane direction are measured by means of the lateral air flow channels of the upper and lower pressing blocks in a controllable temperature and humidity environment and under the condition of compression of the gas diffusion layer. For another example, in the invention application with application number: CN202311674074.9 and invention name: A gas permeability fixture, test system and test method for the gas diffusion layer of a fuel cell, the gas permeability test is carried out under a state of local rigid extrusion by cooperating the gas flow channel grooves of the upper and lower end plates with the gas flow channel ridges, to achieve the gas diffusion layer permeability test under different extrusion forces, different gas pressures, humidity and flow rates.

[0005] However, the existing gas diffusion layer permeability measurement technology has two main disadvantages:

[0006] 1. In the actual working conditions of fuel cells, the gas diffusion layer fluid mass transfer mode is gas-liquid two-phase countercurrent. However, most of the current similar permeability measurement devices only focus on the permeability characteristics of single-phase fluids, and the evaluation of the permeability performance of a single fluid is obviously one-sided. At present, there is a lack of devices that can simultaneously and quantitatively measure the relative permeability of gas and liquid under different working temperatures, humidity and pressures at home and abroad, which makes it difficult for the measurement results to fully reflect the mass transfer capacity of the gas diffusion layer under actual working conditions.

[0007] 2. The mass transfer capacity and mass transfer process of the gas diffusion layer are closely related to its porous structure. For example, the porosity, pore size, wettability of the pore wall, etc. can significantly affect the permeability of the gas-liquid two-phase, thereby affecting the performance of PEMFC. For many gas diffusion layer structural parameters, most studies can only conduct ex-situ experiments on one level of one parameter in a single experiment, which has low experimental efficiency and is difficult to intuitively observe the gas-liquid mass transfer capacity of gas diffusion layers with different structural parameters, which also leads to poor comparability and reference value of experimental results.

[0008] Therefore, how to simulate the gas diffusion layer closer to the actual working environment of the fuel cell and realize the measurement of the gas-liquid relative permeability of the gas diffusion layer is of great significance to the design of industrial gas diffusion layer structural parameters. Summary of the invention

[0009] The technical solution adopted by the present invention to solve the technical problem is: a fuel cell gas diffusion layer gas-liquid relative permeability measurement device, including: a gas source, a gas pressure controller, a humidification system, an upper test box, a lower test box, a temperature control system, a liquid level measuring instrument, a liquid flow pump, a state monitoring module and a signal receiving module; the gas source is connected in series with the gas pressure controller and the humidification system in sequence, and the gas is connected to the inner cavity of the lower test box, and the liquid outlet of the liquid flow pump is connected to the inner cavity of the upper test box. The inner cavity of the upper test box is also provided with a temperature control end of the temperature control system and a liquid level measuring part of the liquid level measuring instrument. The state monitoring module and the signal receiving module are electrically connected to the gas pressure controller, the humidification system, the temperature control system, the liquid level measuring instrument, and the liquid flow pump respectively.

[0010] The upper test box is a semi-enclosed cavity with an opening facing downward, and the lower test box is a semi-enclosed cavity with an opening facing upward. The opening of the upper test box is buckled on the opening of the lower test box from top to bottom. A penetration fixture is provided between the opening of the upper test box and the opening of the lower test box. The penetration fixture isolates and seals the semi-enclosed cavity of the upper test box and the semi-enclosed cavity of the lower test box on the upper and lower sides of the penetration fixture, respectively. A through hole is provided on the penetration fixture, and both ends of the through hole are connected to the semi-enclosed cavity of the upper test box and the semi-enclosed cavity of the lower test box.

[0011] The permeation fixture is provided with an upper pressing plate, an upper elastic gasket, a lower elastic gasket, and a lower pressing plate in order from top to bottom. A clamping position is provided between the upper elastic gasket and the lower elastic gasket for clamping the gas diffusion layer to be tested. The gas diffusion layer to be tested installed in the clamping position crosses the fluid channel in the isolation through hole.

[0012] The inner cavity of the upper test box is provided with a gas receiving cup with an opening downward, the cup mouth of the gas receiving cup is directly opposite to the upper opening of the through hole, the cup mouth of the gas receiving cup is larger than the diameter of the upper opening of the through hole, and a gas flow detection device or a gas volume detection device is provided in the gas receiving cup;

[0013] The inner cavity of the lower test box is provided with a water-receiving measuring cylinder with an opening upward, the mouth of the water-receiving measuring cylinder is directly opposite to the lower opening of the through hole, the mouth of the water-receiving measuring cylinder is larger than the diameter of the lower opening of the through hole, and a liquid flow detection device or a liquid volume detection device is arranged in the water-receiving measuring cylinder.

[0014] Preferably, the outer edges of the openings of the upper test box and the lower test box are both provided with flanges extending horizontally outward, and bolts are provided on the flanges. After the upper test box and the lower test box are buckled together, the flanges are detachably connected by bolts to seal the upper test box and the lower test box.

[0015] More preferably, the upper test box and the lower test box are made of transparent material, and the bolts are made of polytetrafluoroethylene, nylon or plastic.

[0016] Preferably, the bottom of the water collecting cylinder is connected to the water inlet of the liquid flow pump; the top of the air receiving cup is connected to the air inlet of a rubber tube, and the air outlet of the rubber tube is connected to the outside of the upper test box.

[0017] Preferably, the upper test box is provided with a plurality of air receiving cups, the lower test box is provided with a plurality of water receiving measuring cylinders, the penetration fixture is provided with a plurality of through holes, and the air receiving cups, through holes, and water receiving measuring cylinders correspond to each other and are configured as a set;

[0018] The cross-sectional shapes of the through holes include: square holes, diamond holes, round holes, and elliptical holes.

[0019] Preferably, the vertical distance between the cup mouth of the air receiving cup and the upper opening of the through hole is not greater than the diameter of the upper opening of the through hole, and the diameter of the cup mouth of the air receiving cup is greater than twice the diameter of the upper opening of the through hole.

[0020] The present invention also discloses a method for measuring the gas-liquid relative permeability of a fuel cell gas diffusion layer. The method adopts the above-mentioned measuring device and comprises the following steps:

[0021] Step S1: Before measuring, air with a certain temperature and humidity is introduced to purge the device box for more than 5 minutes;

[0022] Step S2, injecting the measuring liquid with determined flow rate and temperature into the device through the water inlet of the upper test box, observing the liquid level measuring instrument until the specified liquid level is reached, so that the liquid level immerses the outside of the cup mouth of the gas receiving cup, controlling the liquid flow pump to make the liquid level stable, and adjusting the temperature control system to make the liquid temperature in the upper test box constant;

[0023] Step S3, introducing the measuring gas for determining the flow rate, temperature and humidity through the air inlet of the lower test box, passing through the gas diffusion layer to be measured in the through hole and entering the gas receiving cup;

[0024] Step S4, controlling the gas pressure controller to make the inner cavity of the lower test box reach the specified gas pressure, and recording the permeation of the gas in the gas receiving cup and the liquid in the water receiving cylinder after a certain period of time, wherein the gas permeation is the gas content in the gas receiving cup immersed in the liquid of the upper test box, and the liquid permeation is the liquid content in the water receiving cylinder in the lower test box;

[0025] Step S5, calculating the single-phase absolute permeability and the gas-liquid two-phase relative permeability of the gas diffusion layer to be tested according to the Darcy formula of the porous material.

[0026] Preferably, the single-phase absolute permeability is:

[0027]

[0028] Where Q is the fluid flow rate, K D is the single-phase permeability, A is the diffusion layer area, μ is the fluid viscosity, l is the diffusion layer thickness, and ΔP is the pressure drop;

[0029] The relative permeability of the gas-liquid two phases is:

[0030]

[0031] Among them, v i is the fluid flow rate, K is the absolute permeability of the fluid, K r,i is the relative permeability of the fluid, μ i is the fluid viscosity, is the pressure gradient.

[0032] Preferably, in step S4, the gas pressure controller is used to control the gas pressure to gradually increase, increasing by 0.3-0.8 kPa every 3-8 minutes, keeping the gas pressure stable for 3-8 minutes every time it increases by 0.3-0.8 kPa, and recording the gas flow rate when the gas pressure is 3-8 kPa; the liquid height of the upper box is increased by controlling the liquid flow pump to control the liquid pressure, increasing by 0.3-0.8 kPa every 3-8 minutes, keeping the liquid water flow stable for 3-8 minutes every time it increases by 0.3-0.8 kPa, and recording the liquid flow rate when the hydraulic pressure is 3-8 kPa.

[0033] The beneficial effects of the present invention are:

[0034] 1. The present invention uses only one device, which can not only measure the absolute permeability of gas and liquid in the gas diffusion layer, but also measure the relative permeability of gas and liquid, and can simulate the actual working conditions of the fuel cell. It is easy to operate, saves measurement costs, and reduces experimental errors.

[0035] 2. The present invention can compare the gas-liquid relative permeability of gas diffusion layers of different types and structural parameters by observing the bubble and droplet penetration of the two in a controllable temperature, humidity and pressure environment, and evaluate the mass transfer characteristics of different gas diffusion layers based on the measurement results.

[0036] 3. The present invention can not only measure absolute permeability, but also measure gas-liquid relative permeability. The clamping part in the device adopts a flange clamping method, which can control the air pressure and water pressure on both sides of the gas diffusion layer, simulate the working state of the gas diffusion layer in the fuel cell, and improve the feasibility and accuracy of the measurement data.

[0037] 4. In order to facilitate observation of bubble and droplet dynamics during the measurement process, the upper and lower test boxes are made of transparent quartz glass. However, quartz glass is relatively brittle. In order to prevent stress concentration during assembly from damaging the device, fastening bolt holes are processed around the plane direction of the gas diffusion layer. At the same time, bolts and nuts made of polytetrafluoroethylene are used for assembly to ensure the safety and reliability of the measuring device.

[0038] 5. Since the clamping part of the present invention is provided with a plurality of gas diffusion layer clamping holes, when collecting the permeated gas, the gas diffusion layer is fastened while the gas receiving beaker is fixed, so that the permeated gases of various gas diffusion layers can be collected separately, thereby realizing the simultaneous measurement of the relative permeabilities of gases in various gas diffusion layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the equipment structure of a device and method for measuring gas-liquid relative permeability of a fuel cell gas diffusion layer according to the present invention;

[0040] Figure 2 is a front cross-sectional view of the penetration fixture of the present invention;

[0041] Figure 3 It is a schematic diagram of three-dimensional separation of the upper test box and the lower test box of the present invention.

[0042] In the figure, 1. gas source; 2. gas pressure controller; 3. humidification system; 4. upper test box; 5. lower test box; 6. temperature control system; 7. liquid level measuring instrument; 8. liquid flow pump; 9. status monitoring module and signal receiving module; 10. penetration fixture; 11. through hole; 12. upper pressure plate; 13. upper elastic gasket; 14. lower elastic gasket; 15. lower pressure plate; 16. clamping position; 17. gas diffusion layer to be tested; 18. gas receiving cup; 19. water collecting cylinder; 20. flange; 21. bolts; 22. rubber tube. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the relevant technologies in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] refer to Figures 1 to 3 As shown, this embodiment provides a device and method for measuring gas-liquid relative permeability of a fuel cell gas diffusion layer. Figure 1 It is a schematic diagram of the equipment structure. Figure 3 This is a schematic diagram of the three-dimensional decomposition of the device body.

[0045] The equipment includes a gas source 1, a gas pressure controller 2, a liquid flow pump 8, a liquid level measuring instrument 7, a humidification system 3, a temperature control system 6, a test box (the test box includes an upper test box 4 and a lower test box 5), a clamping part (the clamping part includes a penetration fixture 10, a through hole 11, an upper pressure plate 12, an upper elastic gasket 13, a lower elastic gasket 14, a lower pressure plate 15, and a clamping position 16), an air receiving cup 18, a water receiving measuring cylinder 19, a status monitoring module and a signal receiving module 9.

[0046] The test box is divided into an upper test box 4 and a lower test box 5. The upper test box 4 is provided with two water inlet branches and holes on the top, which are connected to the test devices such as the liquid flow pump 8, the liquid level measuring instrument 7 and the temperature control system 6 respectively. The edge of the air receiving cup 18 is widened, and an exhaust branch is provided at the bottom to connect the rubber tube 22 to exhaust outside the box. The water receiving measuring cylinder 19 is fixed at the bottom of the lower test box 5, and a drainage branch is provided to connect the drainage system of the liquid flow pump 8; the side of the lower test box 5 is provided with an air inlet branch to connect the air path air intake. The edge of the box is processed into a flange and has a flange hole.

[0047] The clamping part includes a permeation fixture 10, a through hole 11, an upper pressing plate 12, an upper elastic gasket 13, a lower elastic gasket 14, a lower pressing plate 15, and flange holes are opened on the edges, which are aligned and assembled with the flange holes on the edges of the upper test box 4 and the lower test box 5; two symmetrical square through holes 11 are opened inside the upper and lower pressing plates to provide a fluid channel for the fluid to pass through the gas diffusion layer 17 to be tested, and bolt holes are opened around the through holes 11 for fastening the gas diffusion layer 17 to be tested; the gas diffusion layer 17 to be tested is clamped between the upper pressing plate 12 and the lower pressing plate 15, and the upper elastic gasket 13 and the lower elastic gasket 14 are padded between the gas diffusion layer 17 to be tested and the pressing plate. The upper elastic gasket 13 and the lower elastic gasket 14 are made of rubber pads to prevent the fluid from seeping out of the gaps in the pressing plates, and the gas diffusion layer 17 to be tested is fastened by bolts. In order to facilitate real-time reading of gas-liquid flow data during the measurement process, the box body and the pressure plate are both made of highly transparent quartz material. At the same time, in order to reduce the stress concentration generated during the assembly process, bolts 21 and nuts made of polytetrafluoroethylene are used for fastening.

[0048] Measuring gas-liquid relative permeability:

[0049] Before measurement, it is necessary to pass air with specified temperature and humidity to purge the equipment box for more than 5 minutes. Pour liquid water of specified flow rate and temperature into the device through the water inlet of the upper box, observe the liquid level measuring instrument until the specified liquid level is reached, control the liquid flow pump to make the liquid level stable, and adjust the temperature control system to keep the liquid temperature in the upper box constant; the measured gas of specified flow rate, temperature and humidity enters through the air inlet of the lower box, passes through the measured gas diffusion layer and enters the gas receiving beaker inverted on the top, and controls the gas pressure controller to make the lower box reach the specified air pressure. After a certain period of time, the permeation of gas and liquid is recorded respectively. The gas permeation is the gas content in the gas receiving beaker immersed in the liquid of the upper box, and the liquid permeation is the liquid content in the water receiving measuring cylinder of the lower box. According to the Darcy formula of porous materials, the single-phase absolute permeability of the gas diffusion layer and the relative permeability of the gas-liquid two-phase are calculated.

[0050] Example

[0051] Before measurement, the device box needs to be purged with air for more than 5 minutes, and the gas diffusion layer 17 to be measured needs to be kept dry. The gas pressure controller 2 is modified from a gas mass flow meter, with a pressure control range of 80kpa-200kpa and a measurement accuracy of 10Pa. The temperature control system 6 has a control range of room temperature to 80°C, and the humidification system 3 is set to a relative humidity of 60%. The gas to be measured is compressed air.

[0052] 1) Clamp the two gas diffusion layers 17 to be tested, titanium fiber felt and carbon paper, between the upper and lower pressure plates, place a sealing gasket between the pressure plate and the gas diffusion layer 17 to be tested, tighten the fastening bolts around the gas diffusion layer 17 to be tested, clamp the edge of the cup mouth of the gas receiving cup 18 with nuts, fix the gas receiving cup 18 above the gas diffusion layer 17 to be tested, and clamp the rubber tube with a water stop clamp.

[0053] 2) Set up a humidification system 3, and control the relative humidity of the gas at the outlet of the humidification system 3 to be 60%. The humidified air enters the clamping part through the air inlet branch pipe on the side of the lower box, and collects at the bottom of the gas receiving cup 18 after passing through the gas diffusion layer 17 to be tested. The gas permeation amount is read through the scale of the gas receiving cup 18. Set up a gas pressure controller 2, and control the compressed air pressure of the lower test box 5 to increase by 0.5 kPa every 5 minutes, so that the air pressure of the lower test box 5 is stabilized at 5 kPa. When the experiment is over or the gas fills the gas receiving cup 18, remove the water stop clamp and use the rubber tube 22 to exhaust the gas;

[0054] 3) Slowly pour liquid water into the device through the water inlet of the upper test box 4, observe the reading of the liquid level meter 7 until the liquid level reaches 50cm, control the liquid flow pump 8 to stabilize the liquid level at 50cm, and at this time, the hydraulic pressure on the side of the gas diffusion layer 17 to be tested that contacts the liquid water is 5kpa. The liquid water enters the permeation fixture 10 through the water inlet branch pipe of the upper test box 4, and drips into the water receiving measuring cylinder 19 fixed at the bottom of the lower test box 5 after passing through the gas diffusion layer 17 to be tested. The liquid water permeation amount is read from the scale of the water receiving measuring cylinder 19. When the experiment is over or the liquid water fills the water receiving measuring cylinder 19, open the drainage branch pipe at the bottom of the water receiving measuring cylinder 19 to drain the water;

[0055] 4) Record the gas flow displayed by the gas pressure controller 2 when the air pressure of the lower test box 5 is maintained at 5 kPa, and the liquid water flow when the liquid level of the upper test box 4 is maintained at 50 cm, and calculate the gas and liquid relative permeabilities of the different gas diffusion layers 17 to be tested according to the Darcy formula for two-phase fluid of porous materials;

[0056]

[0057] v i is the fluid flow rate, K is the absolute permeability of the fluid, K r,i is the relative permeability of the fluid, μ i is the fluid viscosity, is the pressure gradient.

[0058] 5) When the gas cup 18 and the water measuring cylinder 19 need to be vented and drained, the timing should be paused and the air pressure and hydraulic pressure should be kept stable, and the volume of gas and liquid in the water measuring cylinder 19 should be recorded; after the gas and liquid are completely discharged and the air pressure and hydraulic pressure are stable, the timing should be restarted. At this time, the volume of gas and liquid in the gas cup 18 and the water measuring cylinder 19 are V1 and V2 respectively. Continue the experiment, and the obtained gas and liquid permeation should be subtracted from V1 and V2 respectively.

[0059] Absolute gas permeability:

[0060] Use gas pressure controller 2 to control the gas pressure to gradually increase by 0.5 kPa every 5 minutes, keep the gas pressure stable for 5 minutes every time it increases by 0.5 kPa, and record the gas flow rate when the gas pressure is 5 kPa. When the experiment ends, the gas pressure should also be slowly reduced in steps of 0.5 kPa.

[0061] Absolute liquid permeability:

[0062] Only liquid water is passed through the device. The liquid height of the upper test box 4 is increased by controlling the liquid flow pump 8 to control the liquid pressure, which is increased by 0.5 kPa every 5 minutes. The liquid water flow is kept stable for 5 minutes every time the pressure is increased by 0.5 kPa. The liquid flow rate when the hydraulic pressure is 5 kPa is recorded.

[0063] The single-phase permeability of both liquid and gas can be calculated using Darcy's law.

[0064]

[0065] Where Q is the fluid flow rate, K D is the single-phase permeability, A is the diffusion layer area, μ is the fluid viscosity, l is the diffusion layer thickness, For pressure drop.

[0066] The device of this embodiment can also be fastened with long bolts around the gas diffusion layer 17 to be tested. While fastening the gas diffusion layer 17 to be tested, the gas receiving cup 18 is fixed so that the permeated gases of the two gas diffusion layers 17 to be tested can be collected separately, and the relative permeabilities of the two gas diffusion layers 17 to be tested can be measured simultaneously. The gas collection method here can also be replaced with the device external drainage collection method, or the gas flow meter can be used for collection and measurement. In addition, in addition to using the liquid level measuring instrument 7 to achieve liquid level measurement, a scale can be drawn on the box to read the liquid level data. At the same time, in the pressure drop measurement method, a pressure sensor can be installed at the bottom of the upper test box 4.

[0067] In summary, the present invention sets a permeation fixture between the upper and lower boxes, sets a gas receiving cup above the through hole of the permeation fixture to collect and measure the permeated gas, and sets a water receiving measuring cylinder below the through hole to collect and measure the permeated liquid; only one device can be used to measure not only the absolute permeability of gas and liquid in the gas diffusion layer, but also the relative permeability of gas and liquid, and can simulate the actual working conditions of gas-liquid convection in fuel cells, which is easy to operate, saves measurement costs, and reduces experimental errors. Therefore, the present invention has broad application prospects in the field of energy storage material technology.

[0068] It should be emphasized that the above are only preferred embodiments of the present invention and do not limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A device for measuring gas-liquid relative permeability of a fuel cell gas diffusion layer, characterized in that: include: A gas source (1), a gas pressure controller (2), a humidification system (3), an upper test box (4), a lower test box (5), a temperature control system (6), a liquid level measuring instrument (7), a liquid flow pump (8), a state monitoring module and a signal receiving module (9); the gas source (1) is connected in series with the gas pressure controller (2) and the humidification system (3) and then connected to the inner cavity of the lower test box (5); the liquid outlet of the liquid flow pump (8) is connected to the inner cavity of the upper test box (4); the inner cavity of the upper test box (4) is also provided with a heating end and a temperature control end of the temperature control system (6) and a liquid level measuring part of the liquid level measuring instrument (7); the state monitoring module and the signal receiving module (9) are respectively electrically connected to the gas pressure controller (2), the humidification system (3), the temperature control system (6), the liquid level measuring instrument (7) and the liquid flow pump (8); The upper test box (4) is a semi-enclosed cavity with an opening facing downward, and the lower test box (5) is a semi-enclosed cavity with an opening facing upward. The opening of the upper test box (4) is buckled onto the opening of the lower test box (5) from top to bottom. A penetration fixture (10) is provided between the opening of the upper test box (4) and the opening of the lower test box (5). The penetration fixture (10) isolates and seals the semi-enclosed cavity of the upper test box (4) and the semi-enclosed cavity of the lower test box (5) at the upper and lower sides of the penetration fixture (10). A through hole (11) is provided on the penetration fixture (10), and two ends of the through hole (11) are connected to the semi-enclosed cavity of the upper test box (4) and the semi-enclosed cavity of the lower test box (5). The permeation fixture (10) is provided with an upper pressing plate (12), an upper elastic gasket (13), a lower elastic gasket (14), and a lower pressing plate (15) in order from top to bottom; a clamping position (16) is provided between the upper elastic gasket (13) and the lower elastic gasket (14) for clamping a gas diffusion layer (17) to be tested; the gas diffusion layer (17) to be tested installed in the clamping position (16) cross-sections and isolates the fluid channel in the through hole (11); The inner cavity of the upper test box (4) is provided with a gas receiving cup (18) with an opening facing downwards, the cup mouth of the gas receiving cup (18) is directly opposite to the upper opening of the through hole (11), the cup mouth of the gas receiving cup (18) is larger than the diameter of the upper opening of the through hole (11), and a gas flow detection device or a gas volume detection device is provided in the gas receiving cup (18); The inner cavity of the lower test box (5) is provided with a water-receiving measuring cylinder (19) with an opening facing upwards, the mouth of the water-receiving measuring cylinder (19) is directly opposite to the lower opening of the through hole (11), the mouth of the water-receiving measuring cylinder (19) is larger than the diameter of the lower opening of the through hole (11), and a liquid flow detection device or a liquid volume detection device is provided inside the water-receiving measuring cylinder (19).

2. A fuel cell gas diffusion layer gas-liquid relative permeability measurement device according to claim 1, characterized in that: The outer edges of the openings of the upper test box (4) and the lower test box (5) are both provided with flanges (20) extending horizontally outwards, and bolts (21) are provided on the flanges (20). After the upper test box (4) and the lower test box (5) are buckled together, the flanges (20) can be detachably connected by the bolts (21), thereby sealingly connecting the upper test box (4) and the lower test box (5).

3. A fuel cell gas diffusion layer gas-liquid relative permeability measuring device according to claim 2, characterized in that: The upper test box (4) and the lower test box (5) are made of transparent material, and the bolts (21) are made of polytetrafluoroethylene, nylon or plastic.

4. A fuel cell gas diffusion layer gas-liquid relative permeability measurement device according to claim 1, characterized in that: The bottom of the water collecting cylinder (19) is connected to the water inlet of the liquid flow pump (8); the top of the air receiving cup (18) is connected to the air inlet of the rubber tube (22), and the air outlet of the rubber tube (22) is connected to the outside of the upper test box (4).

5. The device for measuring gas-liquid relative permeability of a fuel cell gas diffusion layer according to claim 1, characterized in that: The upper test box (4) is provided with a plurality of air receiving cups (18), the lower test box (5) is provided with a plurality of water receiving measuring cylinders (19), the permeation fixture (10) is provided with a plurality of through holes (11), and the air receiving cups (18), through holes (11), and water receiving measuring cylinders (19) correspond to each other one by one and are configured as a set; The cross-sectional shapes of the through hole (11) include: a square hole, a diamond hole, a round hole, and an elliptical hole.

6. A fuel cell gas diffusion layer gas-liquid relative permeability measurement device according to claim 1, characterized in that: The vertical distance between the mouth of the air receiving cup (18) and the upper mouth of the through hole (11) is not greater than the diameter of the upper mouth of the through hole (11), and the diameter of the mouth of the air receiving cup (18) is greater than twice the diameter of the upper mouth of the through hole (11).

7. A method for measuring gas-liquid relative permeability of a fuel cell gas diffusion layer, characterized in that: The measuring method adopts the measuring device according to any one of claims 1 to 6, and the measuring method comprises the following steps: Step S1: Before measuring, air with a certain temperature and humidity is introduced to purge the equipment box for more than 5 minutes; Step S2, injecting the measuring liquid of determined flow rate and temperature into the device through the water inlet of the upper test box (4), observing the liquid level measuring instrument (7) until the specified liquid level is reached, so that the liquid level immerses the outside of the cup mouth of the air receiving cup (18), controlling the liquid flow pump (8) to make the liquid level stable, and adjusting the temperature control system (6) to make the liquid temperature in the upper test box (4) constant; Step S3, introducing the measuring gas for determining the flow rate and the temperature and humidity through the air inlet of the lower test box (5), passing through the gas diffusion layer (17) to be measured in the through hole (11) and entering the gas receiving cup (18); Step S4, controlling the gas pressure controller (2) to make the inner cavity of the lower test box (5) reach a specified gas pressure, and after a certain period of time, recording the permeation amount of the gas in the gas receiving cup (18) and the liquid in the water receiving measuring cylinder (19); Step S5, calculating the single-phase absolute permeability and the gas-liquid two-phase relative permeability of the gas diffusion layer (17) to be tested according to the Darcy formula of the porous material.

8. A method for measuring gas-liquid relative permeability of a fuel cell gas diffusion layer according to claim 7, characterized in that: The single-phase absolute permeability is: Where Q is the fluid flow rate, KD is the single-phase permeability, A is the diffusion layer area, μ is the fluid viscosity, l is the diffusion layer thickness, and ΔP is the pressure drop; The relative permeability of the gas-liquid two phases is: Among them, v i is the fluid flow rate, K is the absolute permeability of the fluid, K r,i is the relative permeability of the fluid, μ i is the fluid viscosity, is the pressure gradient.

9. A method for measuring gas-liquid relative permeability of a fuel cell gas diffusion layer according to claim 7, characterized in that: In step S4, the gas pressure controller (2) is used to control the gas pressure to gradually increase, increasing by 0.3 to 0.8 kPa every 3 to 8 minutes, keeping the gas pressure stable for 3 to 8 minutes every time it increases by 0.3 to 0.8 kPa, and recording the gas flow rate when the gas pressure is 3 to 8 kPa; the liquid height of the upper box is increased by controlling the liquid flow pump (8), controlling the liquid pressure, increasing by 0.3 to 0.8 kPa every 3 to 8 minutes, keeping the liquid water flow stable for 3 to 8 minutes every time it increases by 0.3 to 0.8 kPa, and recording the liquid flow rate when the hydraulic pressure is 3 to 8 kPa.

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