A high-speed imaging and particle image velocity measurement method for gas-liquid mass transfer in an inorganic fiber membrane in a gas-liquid flow reactor and its application.

Abstract

A high-speed camera and particle image velocimetry method for monitoring gas-liquid mass transfer in an inorganic fiber membrane in a gas-liquid flow reactor and its application are disclosed. The method involves labeling the gas phase with propylene glycol aerosol generated by atomizing propylene glycol using an atomizer, and labeling the liquid phase with silica microspheres dispersed in an electrolyte. The labeled gas and liquid phases are simultaneously introduced into the reactor under actual photoelectrochemical reaction conditions. A pulsed laser sheet perpendicular to the fiber membrane plane is positioned within the reactor, and a high-speed camera is positioned perpendicular to the laser sheet to synchronously acquire image sequences. Cross-correlation calculations are performed on the image sequences to extract the velocity field and eddy current intensity field at the three-phase interface. The distribution and movement of tracer particles in the gas and liquid phases are observed through the high-speed camera sequence to determine the separation effect of the fiber membrane on the gas and liquid phases and the stability of gas permeation. This method achieves non-contact, in-situ, synchronous, and visual monitoring of the gas and liquid phases, and can be used for evaluating the gas-liquid mass transfer behavior and structural optimization of fiber membranes.

Description

Technical Field

[0001] This invention belongs to the field of in-situ visualization technology of fluid flow and mass transfer, specifically relating to a high-speed imaging and particle image velocity measurement and monitoring method for gas-liquid mass transfer in an inorganic fiber membrane in a gas-liquid flow reactor, and particularly to a non-contact, two-phase, real-time visualization monitoring of the macroscopic mass transfer behavior of the gas-liquid two-phase phases at the three-phase interface of an inorganic fiber membrane under photoelectrochemical flow reaction conditions. Background Technology

[0002] In the photoelectrochemical conversion of poorly soluble gases such as methane and nitrogen, self-supporting inorganic fiber membranes, due to their excellent chemical stability and structural tunability, are often used as core components in gas-liquid flow reactors, serving the dual function of separating the gas and liquid phases while simultaneously providing a gas-liquid-solid three-phase reaction interface. Specifically, the gas phase permeates through the fiber membrane from one side to reach the three-phase interface and participate in the electrochemical reaction, while the liquid electrolyte flows on the other side of the membrane, carrying away reaction products. The continuous and efficient operation of this system largely depends on two key factors: first, whether the gas can stably and continuously permeate through the fiber membrane to reach the reaction interface; and second, whether the gas and liquid phases are effectively separated by the fiber membrane to prevent interpenetration and a decrease in reaction efficiency. Furthermore, whether liquid-phase reaction products or byproducts will gradually deposit on the membrane surface and cause blockage as the reaction proceeds is also a crucial issue directly affecting the system's durability. Therefore, under actual reaction conditions, in-situ observation of the gas-liquid two-phase flow state and mass transfer behavior at the three-phase interface is of great value for evaluating membrane performance and guiding the optimal design of membrane structures.

[0003] Currently, particle image velocimetry (PIV) technology, as an important means of fluid flow measurement, has been widely used in single-phase flow field characterization. However, when this technology is applied to gas-liquid two-phase systems, the conventional approach is to add tracer particles only to the liquid phase, while the gas phase is either unmarked or passively identified based solely on refractive index differences. This approach makes it difficult to clearly distinguish between the gas and liquid phase regions when the flow velocities of the two phases are similar or the interface fluctuations are relatively gentle. Furthermore, it is impossible to determine whether gas phase transmembrane penetration has occurred or whether liquid phase backflow has entered the gas phase side. In other words, conventional single-phase PIV cannot simultaneously provide independent distribution information for both gas and liquid phases, making it difficult to confirm whether the fiber membrane has truly achieved effective separation of the two phases. On the other hand, effective labeling of the gas phase is itself a technical challenge. Due to the low density and rapid diffusion of gases, conventional solid particles or droplets often fail to stably follow the gas phase, easily settling or agglomerating, resulting in unsatisfactory labeling effects. The path and velocity of gas permeation through the fiber membrane, as well as the long-term operational stability, lack intuitive observation methods for verification. Furthermore, even if two-phase flow images can be obtained, without a suitable data processing strategy, the results can only be qualitatively observed, failing to quantitatively provide the velocity field and eddy current intensity field near the three-phase interface. The latter is precisely the key physical quantity reflecting the mixing and mass transfer intensity at the interface. More importantly, the long-term operational reliability of the reactor, especially whether the fiber membrane becomes clogged after the cyclic reaction and whether gas permeability decreases, is difficult to determine directly using existing methods without disassembling the membrane module. Offline testing after disassembly may also disrupt the membrane's true state, causing the evaluation results to deviate from reality.

[0004] Based on the above analysis, there is an urgent need in this field to establish a monitoring method that can simultaneously and effectively label the gas and liquid phases, acquire two-phase flow information in situ under real reaction conditions, and quantitatively characterize the velocity field and eddy field at the three-phase interface. It should also have the ability to directly determine the film blockage and gas permeation stability. Summary of the Invention

[0005] Technical problems to be solved: To address the issues in existing gas-liquid flow reactors where conventional single-phase particle image velocimetry cannot distinguish between gas and liquid phases, where there is a lack of effective marking methods for the gas phase, where it is difficult to quantitatively obtain the velocity field and eddy current field at the three-phase interface, and where it is impossible to determine in situ whether the fiber membrane effectively separates gas and liquid and whether blockage has occurred during long-term operation, this invention provides a high-speed imaging and particle image velocimetry monitoring method for gas-liquid mass transfer using inorganic fiber membranes in gas-liquid flow reactors and its application. This method can separately mark and simultaneously visualize the gas and liquid phases, quantitatively extract the velocity field and eddy current field at the three-phase interface, and simultaneously confirm the separation effect of the fiber membrane on the gas and liquid phases and the stability of gas permeation after the cyclic reaction.

[0006] Technical Solution: A high-speed imaging and particle image velocity measurement monitoring method for gas-liquid mass transfer of inorganic fiber membranes in a gas-liquid flow reactor, comprising the following steps: a. Gas phase labeling: Propylene glycol is added to an atomizer and atomized online in the gas phase path, so that propylene glycol aerosol tracer particles with a particle size of 300nm-800nm ​​are introduced into the reactor along with the gas phase, and the gas phase is labeled; b. Liquid phase labeling: Silica microspheres with a particle size of 200nm-500nm are uniformly dispersed in a 0.1mol / L-1mol / L Na2SO4 electrolyte at a mass fraction of 0.02wt.%-0.10wt.%, and the dispersion is uniformly achieved by ultrasonic treatment, and the liquid phase is labeled; c. Flow loading: A flat-plate gas-liquid flow reactor containing an inorganic fiber membrane is connected to the gas and liquid paths. The reactor is equipped with a quartz optical window. According to the actual working conditions of the photoelectrochemical reaction, the flow rates of both the gas and liquid phases are set to 100 mL / min and simultaneously introduced into the reactor. This allows the gas phase to pass through the fiber membrane from one side to reach the three-phase interface, while the liquid phase flows on the other side of the fiber membrane. d. Sheet illumination: A 532 nm wavelength pulsed laser is arranged, and a sheet laser beam with a single pulse energy of 50 mJ-200 mJ and a thickness of 1 mm-3 mm is formed through a sheet laser mirror group. The sheet laser beam plane is perpendicular to the inorganic fiber membrane plane, illuminating the measurement plane containing tracer particles. e. Synchronous acquisition: A high-speed camera is arranged with its imaging optical axis perpendicular to the laser sheet laser beam. The camera resolution is not less than 1024 × 1024 pixels and the frame rate is not less than 1000 fps. The laser pulse signal is received by a synchronizer and the high-speed camera is triggered synchronously to acquire image sequences of gas and liquid two-phase tracer particles. f. PIV data processing: Cross-correlation operations were performed on the acquired image sequences. The interpretation window was set to 32×32 pixels with a window overlap rate of 50%. The velocity field and eddy current intensity field of the gas phase region and liquid phase region at the three-phase interface of the fiber membrane were extracted respectively. The eddy current intensity was expressed in seconds. -1 Unit: g. High-speed imaging judgment: Acquire and observe the high-speed imaging sequence, and mark the positions of the marked gas phase tracer particles and liquid phase tracer particles with dashed circles. Based on the fact that the gas phase tracer particles are always located on the gas phase side and can pass through the fiber membrane, and the liquid phase tracer particles are always located on the liquid phase side and remain on the liquid phase side, it is determined whether the gas and liquid phases are effectively separated by the fiber membrane. Based on whether the gas phase tracer particles can still continuously pass through the fiber membrane in the high-speed imaging sequence after the cycle reaction, and whether the liquid phase tracer particles accumulate on the membrane surface, it is determined whether the stability of gas permeation and whether the liquid phase products cause blockage.

[0007] The aforementioned inorganic fiber membrane is a TiO2 disordered interwoven self-supporting fiber membrane prepared by electrospinning, wherein the fiber diameter is 100nm to 500nm, the membrane thickness is 30μm to 80μm, the porosity is 75% to 90%, and the effective measurement area is 10mm×10mm to 30mm×30mm.

[0008] Preferably, the gas phase in step a is one of CH4, N2 or NH3.

[0009] Preferably, the particle size of the propylene glycol aerosol tracer particles in step a is 500 nm.

[0010] Preferably, the mass fraction of the silica microspheres in the electrolyte in step b is 0.05 wt.%.

[0011] Preferably, the single-pulse energy of the pulsed laser sheet light in step d is 100 mJ / pulse, and the sheet light thickness is 2 mm.

[0012] Preferably, the frame rate of the high-speed camera in step e is 2000fps.

[0013] Preferably, the TiO2 disordered interwoven self-supporting fiber membrane has a thickness of 50 μm, a porosity of 85%, and a measured effective area of ​​20 mm × 20 mm.

[0014] Preferably, the electrolyte in step b is a 0.5 mol / L Na2SO4 aqueous solution.

[0015] The above methods can be used to evaluate the gas-liquid separation performance and gas-liquid mass transfer behavior of inorganic fiber membranes in photoelectrochemical gas-liquid flow reactors, or to screen and optimize fiber membrane structures.

[0016] Beneficial Effects: This invention independently labels the gas and liquid phases with tracer particles that do not mix, simultaneously capturing the flow information of both phases within the same measurement plane. This overcomes the limitation of conventional single-phase particle image velocimetry, which cannot identify phase states. The effective implementation of this dual-phase labeling strategy relies on the stable tracking of propylene glycol aerosol in the gas phase and the uniform dispersion of silica microspheres in the liquid phase. Both do not interfere with each other in the flow field and faithfully reflect the flow state of their respective phases, thus making the gas-liquid distribution at the three-phase interface readily apparent. More importantly, since the gas-phase tracer particles exist only on the gas phase side and the liquid-phase tracer particles exist only on the liquid phase side, if the fiber membrane fails to separate the gas and liquid phases, the particles of the two phases will inevitably cross and overlap. This characteristic can be directly used as an intuitive basis for judging the membrane's separation performance, confirming whether the fiber membrane effectively blocks the interpenetration of gas and liquid without the need for other detection methods. Building upon the acquisition of independent two-phase distribution information, this invention further combines two-phase labeling with high-speed synchronous acquisition and cross-correlation data processing. This allows for the extraction of velocity and eddy current fields not only independently for the gas and liquid phases but also reveals the spatial differences in velocity distribution characteristics and eddy current intensity of each phase near the three-phase interface. This quantitative information on phase separation offers invaluable insights into interfacial mass transfer mechanisms and the diagnosis of local flow anomalies, qualities that single-phase measurements cannot provide. Simultaneously, the continuous recording function of the high-speed camera sequence complements the aforementioned quantitative measurements. On one hand, quantitative data reflects the flow intensity and mixing degree at the interface; on the other hand, long-term video observation provides a direct verification of whether gas can continuously and stably permeate the fiber membrane and whether liquid products accumulate or clog the membrane surface. These two aspects mutually corroborate each other, providing the evaluation results with both quantitative accuracy and long-term reliability. The steps described above are not simply superimposed, but form a complete chain from independent two-phase labeling to synchronous data acquisition, then to phase-separated quantitative calculation and long-term stability assessment. Two-phase labeling provides the prerequisite for subsequent phase identification and phase-separated calculation, while the quantitative calculation results provide numerical support for qualitative observation via high-speed imaging. Conversely, the long-term imaging assessment verifies whether the flow state reflected by the initial quantitative measurements can be sustained. The effect of this multi-pronged approach is something that cannot be achieved by a single labeling, acquisition, or data processing method alone. This is particularly evident in its ability to simultaneously provide evaluation information on three distinct dimensions—whether gas and liquid are effectively separated, the flow characteristics at the interface, and whether blockage occurs during long-term operation—without disassembling the reactor or disturbing the flow field. This provides a reliable basis for comprehensive evaluation of the gas-liquid mass transfer behavior of fiber membranes and targeted optimization of membrane structures. Attached Figure Description

[0017] Figure 1This is a schematic diagram of a PIV (Polymerization Injection Vehicle) and high-speed camera device used for macroscopic gas-liquid mass transfer monitoring in a gas-liquid flow reactor. The gas phase flow is labeled with propylene glycol aerosol particles generated by an atomizer, and the liquid phase flow is labeled with silica nanoparticles. Laser illumination allows the labeled particles to be tracked to analyze macroscopic mass transfer behavior. The left is a photo of the entire device, the middle is a flow reactor equipped with a fiber membrane, and the right is a close-up of the gas phase aerosol labeling device.

[0018] Figure 2 The PIV results show the gas and liquid fluid distribution at the three-phase interface during the reaction process, illustrating the velocity field and vorticity intensity field (color scale: vorticity intensity, unit: s). -1 ). Detailed Implementation

[0019] The following examples further illustrate the invention, but the scope of protection of the present invention is not limited thereto. The inorganic fiber membranes in the following examples are all electrospun TiO2 disordered interwoven self-supporting fiber membranes (fiber diameter about 100–500 nm, membrane thickness about 50 µm, porosity about 85%, effective area 20 mm × 20 mm).

[0020] Example 1

[0021] a. Gas-phase labeling: Propylene glycol was added to an nebulizer (nebulization frequency 1.7 MHz) and nebulized online in a CH4 gas path to generate propylene glycol aerosol tracer particles with a particle size of 500 nm (number density 10). 6 -10 7 1 cm -3 ), and was introduced into the reactor along with CH4.

[0022] b. Liquid-phase labeling: Silica microspheres with a particle size of 200–500 nm were uniformly dispersed at 0.05 wt.% in 0.5 mol·L⁻¹ liquid. -1 In Na2SO4 electrolyte, sonicate (40 kHz, 100 W) for 10 min to disperse it evenly, and let it stand for 5 min to defoam.

[0023] c. Flow loading: A flat-plate gas-liquid flow reactor (flat plate section flow channel 40 mm × 20 mm, gap 1.5 mm, equipped with 30 mm × 30 mm × 2 mm quartz optical window) containing a TiO2 fiber membrane (membrane thickness approximately 50 µm, effective area 20 mm × 20 mm) is connected to the gas and liquid loop. The gas and liquid flow rates are both set to 100 mL·min using a mass flow controller and a peristaltic pump. -1 (Corresponding to an average flow velocity of 5.6 cm·s) -1 The data was collected at a room temperature of 25 ℃, a peristaltic pump pulsation frequency of 1.5 Hz, and after the flow stabilized for 30 s.

[0024] d. Sheet light illumination: A 532 nm pulsed laser is arranged to form a sheet light with a thickness of about 2 mm and a single pulse energy of about 100 mJ through a sheet light mirror group, which illuminates the three-phase interface measurement area perpendicular to the fiber membrane plane; the double pulse time interval Δt is set to 200 µs.

[0025] e. Synchronous acquisition: The imaging optical axis of the high-speed camera (resolution 1024×1024 pixels, frame rate 2000 fps, equipped with a macro lens, field of view of about 8 mm×8 mm, spatial resolution of 7.8 µm / pixel) is perpendicular to the laser sheet light. It is synchronously triggered with the laser pulse by a synchronizer to acquire gas and liquid two-phase tracer particle image sequences. Each working condition acquires 2 s, about 4000 frames of image sequences.

[0026] f. PIV Data Processing: Cross-correlation was performed on image pairs with Δt=200 µs, using a 32×32 pixel reading window and 50% overlap, to obtain a velocity vector field with a vector spacing of approximately 125 µm. The velocity field and vorticity intensity field (vorticity intensity unit: s) of the gas and liquid phases at the three-phase interface were output. -1 ), the results are shown Figure 2 .

[0027] g. High-speed camera determination: High-speed camera sequences are acquired at 10,000 fps, and the positions of gas and liquid tracer particles are marked with dashed circles to track the process of bubbles passing through the fiber membrane.

[0028] The specific method of in-situ determination is as follows: images are acquired in real time and calculated online during the flow reaction process. The following quantifiable criteria are used to determine the gas-liquid separation and permeability status in real time: (i) Separation criterion: the proportion of tracer particles mixed into the membrane is counted in real time. If it is consistently less than a set threshold (e.g., 1%), the gas and liquid are determined to be effectively separated; (ii) Permeability criterion: the number of permeate bubbles per unit time (permeability frequency) and bubble size are counted in real time by high-speed camera. If the permeability frequency is stable and there is no attenuation, the permeability is determined to be stable; (iii) Blockage criterion: the proportion of silica particle retention area on the membrane surface and the local eddy current intensity are monitored in real time. If the retention spot expands or the local eddy current continuously decreases, the liquid phase product blockage is determined to have occurred. The three criteria can be continuously output during the reaction process to realize in-situ and real-time determination of the gas-liquid mass transfer status.

[0029] Results: Silica particles remained on the liquid phase side, while propylene glycol aerosol particles remained on the gas phase side. Statistics from 500 images showed that tracer particles mixed across the membrane accounted for less than 0.5%, confirming that the TiO2 fiber membrane effectively separated the gas and liquid phases. PIV results showed that the mainstream liquid velocity at the three-phase interface was 4–6 cm·s. -1 An ordered local vortex structure exists near the interface, with peak vorticity intensity of 80–120 s. -1The gas concentration rapidly decreases as it moves away from the interface. After 50 cycles of reaction, high-speed imaging showed that the gas still permeated the fiber membrane stably and continuously in the form of microbubbles at a frequency of 5–15 Hz, with a single bubble diameter of 100–300 µm. No accumulation or blockage of liquid products was observed on the membrane surface, indicating that the membrane has good gas-liquid separation and stable permeability under the test conditions.

[0030] Example 2

[0031] Following steps a–g in Example 1, two TiO2 membranes (labeled membrane A and membrane B) with different fiber orientations / areal densities were tested separately, with gas and liquid phase labeling and flow rates (both 100 mL·min). -1 The laser and camera parameters, as well as the PIV parameters (32×32 pixels, 50% overlap, Δt=200 µs), are all consistent. The film surface density is 8 g·m³. -2 Thickness 35 µm, porosity 88% (relatively loose); B-surface density 16 g·m³ -2 Thickness 55 µm, porosity 80% (relatively dense, with tighter interweaving).

[0032] Results: Both membranes achieved gas-liquid separation and gas permeation; at the three-phase interface, the peak eddy current intensity of membrane A was 150 s⁻¹. -1 The standard deviation of the interface velocity field is 1.8 cm·s. -1 ; Peak eddy current intensity of membrane B: 90 s -1 The standard deviation of the velocity field is 0.9 cm·s. -1 Membrane B exhibits a 40% reduction in eddy current intensity and a 100% improvement in velocity field uniformity compared to membrane A. Regarding permeability stability, membrane B shows more uniform bubble size (100–200 µm), and after 50 cycles, the percentage of transmembrane particles remains <0.5%, with no clogging; membrane A, at 100 mL·min -1 The lower interface exhibits higher eddy current intensity, and localized liquid phase retention occurs after cycling (the eddy current intensity in this region decreases by approximately 30%, and silica particle retention spots are observed). These quantitative results demonstrate that this method can effectively distinguish gas-liquid mass transfer differences in fiber membranes with different structures. Membrane B, with its more compact structure, demonstrates superior gas-liquid separation and permeability stability, and can be used for structural screening and optimization.

[0033] Example 3

[0034] Following steps a, b, d–g of Example 1, step c is divided into two groups: the experimental group is assembled with an intact TiO2 fiber membrane; the control group has its fiber membrane removed (or a damaged membrane is used), with all other conditions being the same, and the proportion of cross-membrane tracer particles is used as the quantitative criterion.

[0035] Results: In the experimental group, silica existed only on the liquid phase side and propylene glycol aerosol only on the gas phase side, with clear separation between the two phases. The percentage of particles crossing the membrane was less than 0.5%, and the gas and liquid velocity fields were located on opposite sides of the membrane with a clear interface. In the control group, there was no membrane separation, and tracer particles from both the gas and liquid phases intersected and mixed with each other. The percentage of particles crossing the membrane was over 35%, and the velocity and eddy current fields showed significant overlap, with the interface disappearing. The intact membrane reduced the mixing ratio between the two phases from 35% in the control group to below 0.5% (a reduction of two orders of magnitude). This control verified the effective separation of the gas and liquid phases by the fiber membrane and also verified the reliability of this method for confirming gas-liquid membrane separation using two-phase tracers.

[0036] Example 4

[0037] Following steps a, c–g of Example 1, only the gas phase was replaced with N2 instead of CH4, and the gas phase was labeled with propylene glycol aerosol at a flow rate of 100 mL·min. -1 The parameters for liquid phase, light, camera, and PIV remained unchanged. The parameters for liquid phase, laser (532 nm, 2 mm, 100 mJ, Δt=200µs), camera (1024×1024, 2000 fps), and PIV (32×32 pixels, 50% overlap) were also unchanged from those in Example 1. 4000 frames were acquired after the flow stabilized for 30 s.

[0038] Results: When N2 was used as the gas phase, aerosol tracer particles existed only on the gas phase side, and silica existed only on the liquid phase side. The proportion of transmembrane particles was less than 0.5%, indicating that the gas and liquid phases were effectively separated by the TiO2 film. The mainstream liquid phase velocity at the three-phase interface was 4–6 cm·s. -1 The local vortex structure at the interface is clear, and the peak vortex intensity is 70 s. -1 High-speed imaging showed that N2 stably and continuously permeated the fiber membrane as microbubbles (100–300 µm in diameter), with no particle retention or blockage after 50 cycles. The results were consistent with those for CH4, indicating that this method is not limited to CH4 and can be applied to gas-liquid mass transfer monitoring of poorly soluble gases such as N2.

[0039] Example 5

[0040] Following the conditions of Example 1, the gas and liquid flow rates were simultaneously measured at 40, 100, and 160 mL·min. -1 Three speed settings (corresponding to average flow velocities of 2.2, 5.6, and 8.9 cm·s) -1 The rest remained unchanged. The laser (532 nm, 2 mm, 100 mJ, Δt=200 µs), camera (1024×1024, 2000 fps, 7.8 µm / pixel), and PIV parameters (32×32 pixels, 50% overlap) were all consistent with those in Example 1. Data was collected after each current level stabilized for 30 s, with 4000 frames collected for each level.

[0041] Results: At all three flow rates, the gas and liquid phases were effectively separated by the TiO2 fiber membrane, and the proportion of tracer particles mixed across the membrane was less than 0.5%. PIV measurements showed that the mainstream liquid velocity at the three-phase interface increased with increasing flow rate at 40, 100, and 160 mL·min. -1 The mainstream velocities were 0–1, 4–6, and 9–14 cm·s, respectively. -1 The peak vorticity intensity of the ordered local vortex structure near the interface also increases with increasing flow rate, with values ​​of 37, 100, and 158 s⁻¹ for the three thresholds. -1 The eddy current decreases rapidly with increasing distance from the interface. High-speed imaging shows that the gas in each flow rate stably and continuously permeates the fiber membrane in the form of microbubbles, with permeation frequencies of 0–7, 5–15, and 24–39 Hz, and bubble diameters of 100–300 µm. After 50 cycles at each flow rate, no silica particle residues or liquid phase product blockages were observed on the membrane surface. In summary, this method effectively analyzes gas-liquid mass transfer behavior under low, medium, and high flow conditions, and can quantitatively reflect how increasing flow rate leads to a simultaneous increase in the mainstream interfacial velocity and eddy current intensity, while maintaining good gas-liquid separation and permeability stability.

Claims

1. A high-speed imaging and particle image velocity measurement and monitoring method for gas-liquid mass transfer in an inorganic fiber membrane in a gas-liquid flow reactor, characterized in that, Includes the following steps: a. Gas phase labeling: Propylene glycol is added to the atomizer and atomized online in the gas phase path, so that propylene glycol aerosol tracer particles with a particle size of 300nm-800nm ​​are introduced into the reactor along with the gas phase to label the gas phase; b. Liquid phase labeling: Silica microspheres with a particle size of 200nm-500nm are uniformly dispersed in 0.1mol / L-1mol / L Na2SO4 electrolyte at a mass fraction of 0.02wt.%-0.10wt.%, and the dispersion is uniformly achieved by ultrasonic treatment. The liquid phase is then labeled. c. Flow loading: Connect the flat-plate gas-liquid flow reactor equipped with an inorganic fiber membrane to the gas path and the liquid path. The reactor is equipped with a quartz optical window. According to the actual working conditions of the photoelectrochemical reaction, the flow rates of both the gas phase and the liquid phase are set to 100 mL / min and simultaneously introduced into the reactor, so that the gas phase passes through the fiber membrane from one side to reach the three-phase interface, and the liquid phase flows on the other side of the fiber membrane. d. Sheet light illumination: A 532nm wavelength pulsed laser is arranged and formed into a single pulsed laser sheet light with a single pulse energy of 50mJ-200mJ and a thickness of 1mm-3mm through a sheet light mirror group. The sheet light plane is perpendicular to the inorganic fiber membrane plane to illuminate the measurement plane containing tracer particles. e. Synchronous acquisition: The high-speed camera is positioned so that its imaging optical axis is perpendicular to the laser sheet light. The camera resolution is not less than 1024×1024 pixels and the frame rate is not less than 1000fps. The laser pulse signal is received by the synchronizer and the high-speed camera is triggered synchronously to acquire the image sequence of gas and liquid two-phase tracer particles. f. PIV Data Processing: Cross-correlation calculations were performed on the acquired image sequences. The interpretation window was set to 32×32 pixels with a 50% overlap rate. The velocity field and eddy current intensity field of the gas and liquid phase regions at the three-phase interface of the fiber membrane were extracted, respectively. The eddy current intensity was expressed in seconds. -1 As a unit; g. High-speed imaging judgment: Acquire and observe high-speed imaging sequences, and mark the positions of the marked gas-phase tracer particles and liquid-phase tracer particles with dashed circles. Based on the fact that the gas-phase tracer particles are always located on the gas phase side and can pass through the fiber membrane, and the liquid-phase tracer particles are always located on the liquid phase side and remain on the liquid phase side, determine whether the gas and liquid phases are effectively separated by the fiber membrane. Based on whether the gas-phase tracer particles can still continuously pass through the fiber membrane in the high-speed imaging sequence after the cycle reaction, and whether the liquid-phase tracer particles accumulate on the membrane surface, determine the stability of gas permeation and whether the liquid-phase products cause blockage.

2. The method according to claim 1, characterized in that, The inorganic fiber membrane is a TiO2 disordered interwoven self-supporting fiber membrane prepared by electrospinning, wherein the fiber diameter is 100nm to 500nm, the membrane thickness is 30μm to 80μm, the porosity is 75% to 90%, and the effective measurement area is 10mm×10mm to 30mm×30mm.

3. The method according to claim 1, characterized in that, The gas phase mentioned in step a is one of CH4, N2 or NH3.

4. The method according to claim 1, characterized in that, The particle size of the propylene glycol aerosol tracer particles mentioned in step a is 500 nm.

5. The method according to claim 1, characterized in that, The mass fraction of the silica microspheres in the electrolyte in step b is 0.05 wt.%.

6. The method according to claim 1, characterized in that, In step d, the single-pulse energy of the pulsed laser sheet light is 100 mJ / pulse, and the sheet light thickness is 2 mm.

7. The method according to claim 1, characterized in that, The frame rate of the high-speed camera mentioned in step e is 2000fps.

8. The method according to claim 2, characterized in that, The inorganic fiber membrane is a TiO2 disordered interwoven self-supporting fiber membrane prepared by electrospinning, with a membrane thickness of 50 μm, a porosity of 85%, and a measured effective area of ​​20 mm × 20 mm.

9. The method according to claim 1, characterized in that, The electrolyte mentioned in step b is a 0.5 mol / L Na2SO4 aqueous solution.

10. The method of any one of claims 1 to 9 is used in evaluating the gas-liquid separation performance and gas-liquid mass transfer behavior of inorganic fiber membranes in photoelectrochemical gas-liquid flow reactors, or in screening and optimizing fiber membrane structures.

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