A salt cavern low-position brine liquid-solid two-phase flow particle migration visualization test device

Abstract

The application discloses a salt cave low-position brine liquid-solid two-phase flow particle migration visualization test device, which comprises a closed circulation pipeline system, a particle adding device, a local configuration assembly, a synchronous acquisition system and a particle recovery processing unit.

Description

Technical Field

[0001] This application relates to the field of experimental technology for low-level brine discharge from underground salt caverns, and in particular to a visual experimental device for the two-phase flow and particle transport of brine in low-level brine discharge from salt caverns. Background Technology

[0002] During the cavity construction and low-level brine discharge process in underground salt cavern storage facilities, sediment particles at the bottom of the cavity may enter the discharge pipe under the action of brine pumping. After entering the discharge pipe, the migration state of the particles is jointly controlled by factors such as pipe diameter, average flow velocity, brine density and viscosity, particle density, particle size distribution, solid phase concentration, and local pipe configuration. When the flow velocity is insufficient or the local pressure loss is too large, the particles are prone to forming a moving sand bed or a fixed sedimentary bed at the bottom of the pipe. Further development can lead to local bridging, diameter reduction blockage, and even a decrease in brine discharge efficiency.

[0003] Existing conventional solid-liquid two-phase flow experimental devices are mostly designed for transporting ordinary clean water or slurry. However, their application in the study of particle transport in low-level brine discharge sediment in salt caverns still has the following shortcomings: First, the circulating pumps and flow meters often directly transport sand-containing fluids, which can easily cause pump wear, flow meter fluctuations, and unstable solid concentration control. Second, the experimental sections are mostly single-diameter or opaque pipes, making it difficult to continuously observe the entire process of particles from initiation to deposition, bridging, and blockage. Third, it is inconvenient to change pipe diameters, reduction ratios, and local configurations, making it difficult to conduct multi-factor comparisons on the same platform. Fourth, there is a lack of synchronous acquisition between flow rate, pressure, and image data, resulting in an unclear correspondence between pressure changes and particle motion morphology. Fifth, there is a lack of complete mass balance for discharged particles, residual particles, and particle size composition, making it difficult to accurately calculate sand carrying rate, residual rate, critical sand carrying velocity, and maximum stable sand carrying particle size.

[0004] Therefore, developing a dedicated liquid-solid two-phase flow test device suitable for high-concentration brine environments, capable of quantitative particle addition, visual observation of transparent pipe sections, rapid replacement of multiple pipe diameters and local configurations, simultaneous acquisition of flow and pressure images, and particle filtration and recovery analysis, is an experimental technology requirement that urgently needs to be addressed in the study of particle transport and blockage mechanisms of low-level brine discharge sediment in salt caverns. Summary of the Invention

[0005] This application provides a visualization test device for solid-phase flow and particle migration in low-level brine discharge from salt caverns. By integrating a salt-resistant closed-loop circulation pipeline system, a particle quantitative dosing system, a replaceable transparent observation pipe section, local configuration components, a pressure and flow rate image synchronous acquisition system, and a particle filtration and recovery post-processing system, it can simulate the sediment particle migration process under different brine discharge velocities, pipe diameters, particle size distributions, solid phase concentrations, and local diameter reduction conditions on the same test platform. This allows for the simultaneous observation of particle motion morphology and calculation of quantitative indicators. The technical solution is as follows: The first aspect of this application provides a visualization test device for solid-phase flow and particle migration in low-level brine discharge from a salt cavern, comprising: a closed-loop pipeline system, including a storage tank, a delivery pump, a flow meter, a transparent observation section, and a return pipeline connected in sequence, for continuously circulating brine in the pipeline; a particle dosing device, located downstream of the flow meter and upstream of the transparent observation section, for quantitatively adding solid particles to the pipeline at a set rate; a local configuration component, detachably installed in the middle of the transparent observation section, for simulating at least one pipeline morphology among equal-diameter connection, narrow-diameter transition, and local deposition; a synchronous acquisition system, including the flow meter, pressure measuring points arranged along the transparent observation section, and a high-speed camera device located beside the transparent observation section, for synchronously recording pipeline flow rate, pressure at each measuring point, and images of particle movement within the pipe; and a particle recovery and processing unit, located after the outlet of the transparent observation section, for intercepting and recovering discharged particles. According to the above embodiments, continuous circulation of brine is achieved by constructing a closed-loop pipeline system. The particle dosing device is arranged downstream of the flow meter and upstream of the transparent observation pipe section, enabling direct particle dosing that bypasses the delivery pump and flow meter. This fundamentally avoids wear and measurement disturbance to the pump impeller and flow meter electrodes caused by sand-containing fluid. Compared with conventional methods that directly add particles before or inside the pump, the flow meter always measures single-phase brine rather than a solid-liquid mixture, thus significantly improving the accuracy of flow measurement and the reliability of average velocity conversion. Simultaneously, the particle dosing device is connected in series with the transparent observation pipe section. Combined with local configuration components, a synchronous acquisition system, and a particle recovery unit, this device integrates five major functions on a single platform: closed-loop circulation, quantitative and controllable dosing, multi-configuration simulation, multi-source signal synchronous acquisition, and mass balance recovery. This provides complete experimental conditions for studying the effects of pipe diameter, flow velocity, particle size distribution, solid concentration, and local configuration on particle transport behavior.

[0006] For example, in one embodiment of the visualization experimental device for particle transport in the solid-phase flow of brine in a salt cavern, the transparent observation tube is configured as a detachable and replaceable tube with different inner diameter specifications. The transparent observation tubes with different inner diameter specifications are connected using a unified flange connection interface, gasket, and transition joint. The inner wall of each tube joint is ground smooth. According to the above embodiment, by configuring the transparent observation tube as a detachable and replaceable tube with different inner diameter specifications, and using a unified flange connection interface, gasket, and transition joint, and grinding the inner wall of the joint, rapid, sealed, and disturbance-free switching between different tube diameter conditions is achieved. The unified interface avoids the workload of re-piping when replacing tube sections, and the smoothing of the inner wall eliminates the additional disturbance to particle movement caused by steps at the joint—if there are steps at the joint, particles may experience non-physical acceleration, deceleration, or collision when passing over the steps, introducing systematic errors unrelated to the tube diameter effect. This design allows tube diameter effect research to be carried out on the same platform through simple tube section replacement rather than replacing the entire device, ensuring the consistency of other experimental variables under different tube diameter conditions and improving the reliability of comparative experiments.

[0007] For example, in one embodiment of the visualization experimental device for particle transport in the solid-phase flow of low-level brine in a salt cave, the transparent observation tube is made of PMMA material, with length markings on its outer wall and a backlight source. The backlight source is positioned on the opposite side of the high-speed camera to enhance the contrast of the particle motion image. According to the above embodiment, by using highly transparent PMMA material, length markings on the outer wall, and a backlight source on the opposite side of the high-speed camera, high-definition, high-contrast visualization conditions are provided for particle motion observation. The high light transmittance of PMMA material allows for clear capture of particle initiation, rolling, jumping, suspension, deposition, and bridging behaviors within the tube; the length markings directly link the particle position to the pipe coordinates, facilitating the spatial distribution of particles during image analysis; the backlight source illuminates from the opposite side of the camera, making the particles appear as dark silhouettes against a bright background in the image, significantly enhancing the contrast between the particles and the background and avoiding interference from pipe wall reflections during frontal illumination. This combination ensures that the high-speed camera system can record particle motion details at a frame rate of no less than 1000fps, providing high-quality raw data for subsequent image analysis.

[0008] For example, in one embodiment of the visualized experimental device for particle transport in the solid-phase flow of low-level brine in a salt cave, the particle feeding device includes a feeding funnel, a screw conveyor mechanism, a variable frequency speed control mechanism, and a weighing feedback mechanism. The weighing feedback mechanism is used to record changes in the feeding mass in real time, and the screw conveyor mechanism is used to stably convey particles at a target rate. According to the above embodiment, the particle feeding device achieves quantitative, stable, and real-time feedback control of the particle feeding rate. The volumetric conveying characteristics of the screw conveyor mechanism ensure a good linear relationship between the output rate and rotational speed under variable frequency speed control. The weighing feedback mechanism monitors the mass decay of the feeding funnel in real time, which can correct for fluctuations in the instantaneous feeding rate and accumulate the actual total amount fed over any time period, providing reliable input parameters for accurate calculation of solid phase concentration and avoiding the concentration uncertainty caused by relying solely on estimated values ​​or retrospective total amount calculations.

[0009] For example, in the visual experimental device for particle migration in the solid-phase flow of brine in a salt cavern provided in one embodiment, the local configuration component includes a constant diameter connecting section, an abrupt diameter reduction section, a gradually narrowing diameter reduction section, or a local deposition simulation section, wherein the diameter reduction ratio of the diameter reduction section is 0.9D, 0.8D, 0.7D, or 0.6D. According to the above embodiment, the local configuration component provides systematic experimental conditions for studying the impact of abrupt changes in pipeline geometry on particle migration and blockage. The abrupt diameter reduction section simulates the stepped channel contraction caused by deposition or scaling, the gradually narrowing diameter reduction section simulates the conical transition caused by pipe wall erosion or construction deviations, and the local deposition section simulates the change in effective flow area after particles form a bed at the bottom of the pipe. The diameter reduction ratio series from 0.9D to 0.6D covers the common engineering range from slight diameter reduction (10% shrinkage) to severe diameter reduction (40% shrinkage). By systematically measuring pressure loss, particle retention, and blockage time under different diameter reduction ratios, a quantitative relationship curve between diameter reduction ratio and blockage risk can be established, providing an early warning threshold for on-site pipeline maintenance.

[0010] For example, in one embodiment of the visualization test device for solid-phase flow and particle transport in low-level brine discharge from a salt cavern, the pressure measuring points are arranged at at least one of the following locations: the outlet of the delivery pump, the inlet of the transparent observation pipe section, the outlet of the transparent observation pipe section, and the front and rear sides of the local configuration component. According to the above embodiment, a complete pressure gradient monitoring network along the flow direction is established. The pump outlet measuring point monitors the pump's outlet pressure reference and pulsation; the pipe section inlet and outlet measuring points acquire the pressure loss along the pipe; and the measuring points on the front and rear sides of the local configuration component acquire the local pressure loss. This arrangement enables the system to simultaneously obtain pressure loss data for both pipe friction and local resistance. When a sudden change in pressure occurs at a certain measuring point, it can quickly pinpoint whether the change is due to a change in pipe conditions or a change in the local configuration, providing a basis for determining the location and type of blockage.

[0011] For example, in one embodiment of the visualized experimental device for particle transport in the solid-liquid two-phase flow of brine in a salt cave, the particle recovery and processing unit includes a filter, a sedimentation recovery tank, a drying device, a weighing device, and a sieving device, used to intercept, recover, dry, weigh, and sieve the discharged particles and the particles remaining in the pipe, respectively. According to the above embodiment, the particle recovery and processing unit provides hardware support for complete mass balance analysis. The filter intercepts particles from the solid-liquid mixture, the sedimentation recovery tank recovers extremely fine particles carried in the filtered brine, the drying device removes moisture to obtain dry mass, and the weighing device obtains the discharged dry mass m. out and residual dry mass m r The sieving device obtains the particle size distribution of discharged and residual particles. This unit enables the simultaneous acquisition of total discharged mass, total residual mass, mass balance closure, and the discharge ratio of different particle sizes after the experiment, overcoming the problem of incomplete evaluation caused by relying solely on visual inspection or measuring only the total mass.

[0012] For example, in one embodiment of the visualization experimental device for solid-phase flow and particle transport in low-level brine drainage in a salt cave, a transparent protective cover is also included, which covers the outside of the transparent observation tube section. According to the above embodiment, by setting a transparent protective cover to cover the outside of the transparent observation tube section, a physical safety barrier is provided without affecting the visualization observation. The transparent material (PC) ensures that the high-speed camera system can penetrate the protective cover to directly photograph the particle movement inside the tube section, while also blocking the splashing of fragments and high-temperature, high-pressure brine in the event of an accidental rupture or high-pressure leak in the pipeline, protecting operators and precision instruments. This design balances experimental safety (meeting the safety requirements of high-pressure experiments) and the integrity of the observation function (not obstructing the camera and lighting paths).

[0013] The second aspect of this application provides a method for conducting a low-level brine particle transport test using the aforementioned device, comprising the following steps: adding brine to a storage tank and starting a delivery pump to circulate the brine in a closed-loop pipeline system; selecting a transparent observation pipe section with a target inner diameter and installing it in the pipeline, and installing a target local configuration component in the middle of the transparent observation pipe section according to the test requirements; adjusting the operating frequency of the delivery pump to achieve a target average flow velocity in the brine; starting a particle feeding device to quantitatively add solid particles to the brine flow at a set rate, forming a solid-liquid mixed flow that enters the transparent observation pipe section; simultaneously collecting and recording pipeline flow data, pressure data at each pressure measuring point, and particle motion image data captured by a high-speed camera; based on the synchronously collected data, when the pressure loss continuously increases and the flow rate decreases in a short period of time, and the image shows that particles form bridging or a fixed sedimentation bed in a local area, it is determined that a blockage has occurred under this condition. According to the above embodiments, by sequentially executing six steps—establishing circulation with brine, selecting pipe section installation configuration, adjusting flow rate, initiating dosing, synchronous data acquisition, and joint determination of blockage based on multi-source signals—the structural characteristics of the device are transformed into an operable standardized experimental procedure. The key control point in this procedure—establishing a single-phase flow baseline before adding particles for two-phase flow experiments—ensures consistent initial conditions for each experiment. Synchronous acquisition of multi-source signals (flow rate, pressure, and imagery) unifies changes in particle motion morphology with sudden pressure loss and flow rate fluctuations onto the same timeline. The blockage determination criteria combine physical signals (continuous pressure increase, flow rate decrease) and visual evidence (imagery showing bridging or a fixed bed), avoiding misjudgments based solely on a single signal (e.g., a pressure increase might indicate pump fluctuations), and improving the reliability of critical sand-carrying velocity and blockage threshold determination.

[0014] For example, in one embodiment of the visualization test method for solid-phase flow and particle transport in low-level brine discharge from salt caves, the following post-processing steps are also included: After the test, the discharged particles and residual particles in the pipe are collected by a particle recovery processing unit, and then dried, weighed, and sieved to obtain the dry mass m of the discharged particles. out and residual particle dry mass m r The sand carrying rate η is calculated using the following formula: η = m out / m0×100%, where m0 is the initial dry mass of the added particles; the residual rate R is calculated using the following formula: R=m r / m0×100%; By gradually changing the average flow velocity inside the pipe, the lowest flow velocity at which particles can be stably discharged without forming a continuously growing fixed sediment bed inside the pipe is determined as the stable sand-carrying velocity. According to the above embodiment, by limiting the particle recovery, drying, weighing, and sieving steps after the experiment, as well as the calculation formulas for sand carrying rate and residual rate, and by gradually changing the flow velocity to determine the stable sand-carrying velocity, the effect is that: qualitative observation results are transformed into quantifiable engineering evaluation indicators. The sand carrying rate characterizes the proportion of particles carried out of the pipeline by brine, directly reflecting the particle transport efficiency of the pipeline; the residual rate characterizes the proportion of particles deposited inside the pipe, reflecting the scaling trend of the pipeline; the stable sand-carrying velocity is a key parameter in engineering design to determine whether anti-clogging measures need to be taken—when the actual brine discharge velocity is higher than this value, particles can be effectively carried out; when it is lower than this value, the pipe diameter needs to be increased or the discharge rate increased to avoid deposition and blockage. The experimental method of gradually changing the flow rate can obtain the relationship curve between sand carrying rate and flow rate. By interpolating the inflection point of the curve or the threshold, the critical flow rate can be accurately located, providing direct experimental basis for the selection of brine discharge pipe diameter and the design of brine discharge flow rate on site.

[0015] Compared with existing conventional solid-liquid two-phase flow test devices, the visual test device and method for particle transport in the solid-liquid two-phase flow of low-level brine discharge in this application has the following advantages by setting the particle addition device downstream of the flow meter and upstream of the transparent observation pipe section, configuring a replaceable transparent pipe section and local configuration components, and integrating a multi-source synchronous acquisition system and a particle recovery and processing unit: 1. Enables quantitative dosing of particles, bypassing the pump body and flow meter, eliminating equipment wear and measurement disturbances. This application positions the particle dosing device downstream of the flowmeter and upstream of the transparent observation pipe section, allowing solid particles to bypass the delivery pump and flowmeter and enter the pipe section directly. This avoids wear and corrosion of the pump impeller and flowmeter electrodes by sand-containing fluid, while ensuring that the flowmeter always measures single-phase brine rather than a solid-liquid mixture. The flowmeter readings are unaffected by the impact and noise generated by the passing particles, significantly improving the reliability of average flow velocity conversion and solid concentration control, extending the service life of the core measuring equipment, and reducing the maintenance costs of the experimental setup.

[0016] 2. A unified platform for multi-factor comparative experiments was established, enabling rapid switching between pipe diameter and pipeline configuration. This application, through the configuration of transparent observation pipe sections with different inner diameters and a unified flange interface, and detachable local configuration components, allows for rapid replacement of pipe diameters (DN40, DN50, DN65) and reduction ratios (0.9D, 0.8D, 0.7D, 0.6D) on the same platform, and simulation of various pipeline morphologies such as constant diameter, abrupt reduction, gradual reduction, and local deposition. The smoothing of the inner wall at the joint eliminates step disturbances. Pipe diameter effects, flow velocity effects, particle size distribution effects, solid concentration effects, and local configuration effects can be systematically compared on the same device through simple component replacement rather than rebuilding the experimental system. This significantly improves the uniqueness of experimental variable control and the comparability of results, greatly reducing the experimental cycle and cost of multi-factor studies.

[0017] 3. Real-time correlation between particle motion morphology and hydraulic parameters was achieved, and a quantitative correspondence between pressure surges and blockage was established. This application integrates flow rate signals, multi-point pressure signals along the pipe, and high-speed camera image signals onto the same time axis using a synchronous acquisition system. Pressure measurement points are arranged at the pump outlet, pipe inlet and outlet, and before and after local configurations, allowing simultaneous acquisition of pressure loss along the pipe and local pressure loss. When pressure loss increases continuously and flow rate decreases within a short period, and the image shows particles forming bridging or fixed sediment beds in local areas, blockage can be accurately determined and its location precisely pinpointed—whether it occurs in a straight section of the pipe or at a local configuration. Compared to traditional methods that rely solely on pressure fluctuations to guess the blockage location, this application correlates changes in particle motion morphology with sudden pressure changes and flow rate fluctuations in real time, improving the accuracy and reliability of determining critical sand-carrying velocities and blockage thresholds.

[0018] 4. A complete particle mass balance system was constructed, enabling quantitative evaluation of sand carrying capacity and residual rate. This application utilizes a filter, sedimentation and recovery tank, drying device, weighing device, and sieving device to intercept, recover, dry, weigh, and sieve the discharged particles and residual particles in the pipe for analysis. It can simultaneously obtain the dry mass of discharged particles, the dry mass of residual particles, and the discharge ratio of different particle sizes. The sand-carrying rate characterizes the proportion of particles carried out of the pipeline by the brine, directly reflecting the particle transport efficiency of the pipeline; the residual rate characterizes the proportion of particles deposited in the pipe, reflecting the scaling trend of the pipeline; and the mass balance closure can verify the completeness and reliability of the experimental data. This overcomes the problems of incomplete evaluation and lack of data traceability caused by relying solely on visual judgment or measuring only the total mass, providing precise experimental parameters for the design of on-site brine discharge pipelines.

[0019] 5. It provides optimal conditions for visual observation, enabling high-definition recording of the entire particle motion process. This application uses PMMA high-transparency material pipe sections with length scale markings on the outer wall and a backlight source on the opposite side of the high-speed camera device. The backlight source illuminates the image from the opposite side of the camera, making the particles appear as dark silhouettes and the background as bright, enhancing the contrast between the particles and the background and avoiding interference from pipe wall reflections during front lighting. The length scale markings directly link the particle position to the pipe coordinates, facilitating the location of the particle's spatial distribution during image analysis. The high light transmittance of PMMA material allows for the clear capture of particle initiation, rolling, jumping, suspension, deposition, and bridging behaviors within the pipe, providing high-quality raw data for subsequent image analysis and motion trajectory tracking.

[0020] In summary, this application addresses four major technical shortcomings of existing conventional solid-liquid two-phase flow test devices in the study of particle transport in low-level brine discharge sediment in salt caverns: "pump damage measurement deviation, inconvenient pipe replacement, image-pressure disconnection, and incomplete balance calculation." These shortcomings are addressed through a systematic technical solution that includes particle bypassing the pump body flow meter for injection, rapid replacement of multiple diameter transparent pipe sections, local configuration simulation, synchronous acquisition of multi-source signals, and complete mass balance recovery. This provides reliable experimental means and quantitative decision-making basis for the parameter design of low-level brine discharge pipelines in salt caverns, safety evaluation of injection and production channels, and optimization of on-site brine discharge processes. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of the overall structure of the experimental device for visualizing particle transport in the solid-phase flow of low-level discharged brine. Figure 2 A schematic diagram illustrating the experimental procedure and evaluation index acquisition for the transport of particles in the low-level brine-solid two-phase system. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0025] I. Overall Structure of the Device like Figure 1 As shown, the visual experimental device for particle transport in low-level brine-solid two-phase flow in salt caverns of this application mainly includes a closed-loop pipeline system, a particle feeding device, a replaceable transparent observation pipe section, local configuration components, a synchronous acquisition system, and a particle recovery and processing unit.

[0026] The closed-loop pipeline system consists of a storage tank 10, a butterfly valve, a variable frequency corrosion-resistant centrifugal pump 20, a steady-flow straight pipe section, an electromagnetic flowmeter 30, a transparent observation pipe section 40, connecting pipes, and a return pipe section 70. Brine is transported from the storage tank 10 via the variable frequency corrosion-resistant centrifugal pump 20, passes through the steady-flow straight pipe section and the electromagnetic flowmeter 30, and then enters the particle addition area. Particles are added by the particle addition device 60 at a set rate, ensuring that solid particles do not pass through the circulation pump and flowmeter. The solid-liquid mixture then enters the transparent observation pipe section 40, where pressure measuring points, a high-speed camera device 80, and a data acquisition system simultaneously record flow rate, pressure loss, and particle motion images. Discharged particles are intercepted by the particle recovery treatment unit 90, and the filtered brine is returned to the storage tank 10 after sedimentation and recovery, forming a closed loop.

[0027] (1) Closed-loop pipeline system like Figure 1As shown, the closed-loop pipeline system includes a storage tank 10, a transfer pump 20 (variable frequency corrosion-resistant centrifugal pump), a flow meter 30 (electromagnetic flow meter), a transparent observation pipe section 40, and a return pipeline 70, all connected in sequence. The storage tank 10 stores saturated or near-saturated NaCl brine. The tank body can be made of PE, FRP, or other salt-resistant materials and is equipped with a level display, a replenishment port, a drain port, and a return interface. The flow-through components of the variable frequency corrosion-resistant centrifugal pump 20 are made of perfluoroplastics, 316L stainless steel, or other salt-resistant and wear-resistant materials. Different flow conditions are achieved through frequency conversion control. Valves are arranged at the storage tank outlet, before and after the pump, before and after the flow meter, and on the return pipeline for start-up, shutdown, maintenance, and safety isolation.

[0028] An electromagnetic flowmeter 30 is positioned upstream of the granule dosing device 60 to acquire the instantaneous flow rate of the pipeline in real time. A steady-flow straight pipe section is installed between the pump and the flowmeter to eliminate flow pulsation at the pump outlet and ensure the stability of the flow measurement. This module enables continuous circulation of brine between the storage tank, pump, flowmeter, transparent observation pipe section, filter collection unit, and sedimentation recovery tank, which reduces brine consumption and maintains relative stability of the density and temperature of the test medium.

[0029] (2) Particle feeding device like Figure 1 As shown, the pellet feeding device 60 is located downstream of the flow meter 30 and upstream of the transparent observation pipe section 40. It mainly includes a feeding funnel, a screw conveyor mechanism, a variable frequency speed control mechanism, a weighing feedback mechanism, and a lateral feeding interface. The weighing feedback mechanism is used to record changes in the feeding mass in real time, the screw conveyor mechanism is used to stably feed the pellets at the target rate, and the lateral feeding interface ensures that the pellets are fully mixed with the brine before entering the transparent pipe section.

[0030] This arrangement avoids the particles passing through the transfer pump and electromagnetic flowmeter, reducing wear on flow components and ensuring that the flowmeter primarily measures single-phase brine, thereby improving the reliability of average velocity conversion and solids concentration control. The experimental particles can be quartz sand, artificially graded particles, or natural sediment particles obtained through on-site sediment screening.

[0031] (3) Transparent observation pipe section and pipe diameter replacement structure like Figure 1 As shown, the transparent observation tube section 40 is the core visualization component of the device. It can be made of PMMA acrylic glass or other highly transparent and pressure-resistant materials and is horizontally arranged on an adjustable support. The outer wall is marked with length graduations and equipped with a backlight source, positioned opposite the high-speed camera device 80 to enhance the contrast of the particle motion images. The transparent observation tube section 40 is covered with a transparent PC protective cover to prevent injury from pipe rupture or particle splashing.

[0032] Transparent observation section 40 is configured as a detachable and replaceable section with different inner diameters. To study the impact of overall pipe diameter variations on particle migration, transparent observation sections with different inner diameters, such as DN40, DN50, and DN65, can be configured. Transparent observation sections with different inner diameters are connected using standardized flange connections, gaskets, and transition joints. The inner walls at the joints of each section are ground smooth to avoid steps causing additional disturbance to particle movement. Each section has the same or substantially the same effective observation length.

[0033] (4) Local configuration components like Figure 1 As shown, the local configuration component 50 is detachably installed in the middle of the transparent observation tube section 40 to simulate at least one pipe configuration among constant diameter connection, narrowing transition, and local deposition. Specifically, it includes a constant diameter connection section, an abrupt narrowing section, a gradually narrowing section, or a local deposition simulation section. The narrowing section has a reduction ratio of 0.9D, 0.8D, 0.7D, or 0.6D, used to simulate changes in effective flow area during local channel narrowing, deposition contraction, or the pre-blockage phase. Pressure measuring points are located at both ends of the local configuration component to measure the pressure loss before and after the local configuration.

[0034] (5) Synchronous acquisition system like Figure 1 As shown, the synchronous acquisition system includes an electromagnetic flowmeter 30, pressure measuring points arranged along the transparent observation pipe section 40, and a high-speed camera device 80 set beside the transparent observation pipe section 40, which is used to synchronously record pipeline flow, pressure at each measuring point, and images of particle movement inside the pipe.

[0035] Pressure measurement points are arranged at at least one of the following locations: the outlet of the delivery pump, the inlet of the transparent observation section, the outlet of the transparent observation section, and both sides of the local configuration components, for recording pressure loss along the pipe and local pressure loss. A high-speed camera device is installed on the side of the transparent pipe section, equipped with a backlight source and a movable support, and can continuously record the particle initiation, migration, suspension, deposition, bridging, and blockage processes. The high-speed camera system has a frame rate of not less than 1000fps and a data acquisition frequency of not less than 100Hz.

[0036] The data acquisition system synchronously records flow signals, pressure signals, and image trigger signals. Using a unified timeline, changes in particle motion morphology can be correlated with sudden pressure loss, flow fluctuations, and the timing of blockages.

[0037] (6) Particle recycling and processing unit like Figure 1As shown, the particle recovery and processing unit 90 is located after the outlet of the transparent observation tube section 40. It includes a pipeline filter, a removable filter basket, a sedimentation recovery tank, a drying oven, an electronic balance, and a standard sieve set. It is used to intercept, recover, dry, weigh, and sieve analyze the discharged particles and the particles remaining in the tube. The pipeline filter, located after the outlet of the transparent experimental tube section, intercepts the discharged particles through coarse and fine filter screens. The filtered brine enters the sedimentation recovery tank, undergoes preliminary sedimentation, and then flows back to the storage tank.

[0038] After the experiment, the filtered particles, residual particles in the pipe, and fine particles in the sedimentation tank were recovered, dried, weighed, and sieved to obtain the dry mass of discharged particles, the dry mass of residual particles, and the discharge ratio of particles of different sizes. Then, the sand carrying rate, residual rate, mass balance closure degree, and maximum stable sand carrying particle size were calculated.

[0039] II. Implementation Examples The following is an example: a simulation experiment on the movement and blockage of sediment particles in the horizontal brine discharge pipe during the low-level brine discharge process of a salt cavern storage.

[0040] During the low-level brine discharge stage of a layered salt reservoir, it is necessary to determine whether sediment particles will form continuous deposition or local blockage in the discharge pipe. The purpose of the experiment is to use the liquid-solid two-phase flow particle transport visualization test device of this application to obtain particle motion morphology, pressure loss, sand carrying rate, residual rate, critical sand carrying velocity, and maximum stable sand carrying particle size under different pipe diameters, flow velocities, particle size distributions, and solid phase concentrations.

[0041] (1) Experimental materials and apparatus The test medium is saturated or near-saturated NaCl brine, and the test particles are quartz sand or natural sediment particles obtained by on-site sludge screening and drying. The main equipment includes: a storage tank (500L capacity), a variable frequency corrosion-resistant centrifugal pump (4kW power), an electromagnetic flowmeter (DN50, PTFE lined), a screw-type particle feeding device, PMMA transparent observation pipe sections (configured with three specifications: DN40, DN50, and DN65, each section with an effective length of 5m, consisting of two transparent pipe sections spliced ​​together by flanges), a local diameter reduction module (which can be set with four diameter reduction ratios: 0.9D, 0.8D, 0.7D, and 0.6D), a pressure monitoring system (including several on-site pressure gauges and at least one digital pressure transmitter), a high-speed camera system (frame rate not less than 1000fps), a data acquisition system (acquisition frequency not less than 100Hz), a particle filter, a sedimentation recovery tank, a drying oven, an electronic balance, and standard sieve sets.

[0042] (2) Experimental procedures Brine preparation and property testing: Add NaCl brine to the storage tank, test and record the brine density ρ and temperature T to ensure that the fluid properties are basically consistent under different working conditions.

[0043] Particle preparation and gradation design: After drying the sludge particles or quartz sand, sieve them and prepare samples according to the target particle size or mixed gradation. Record the initial dry mass of the added particles, m0. For continuous feeding, the screw feeding acceleration rate q can be used as the basis. s Calculate m0=q based on the addition time t. s ×t.

[0044] Pipeline installation and benchmark testing: Select a DN40, DN50, or DN65 transparent observation pipe section according to the experimental purpose, or install the target diameter reduction module in the middle of the DN50 transparent observation pipe section. After completing the flange connection, sealing check, and support leveling, start the delivery pump to circulate the particle-free brine in the pipeline, and record the benchmark flow rate Q0 and benchmark pressure loss Δp0.

[0045] Target flow velocity setting: Adjust the frequency of the delivery pump to achieve the target average flow velocity in the pipe. The average flow velocity is calculated using the formula v = 4Q / (πD). 2 The calculation is performed, where Q is the volumetric flow rate measured by the flow meter, and D is the inner diameter of the transparent observation pipe section.

[0046] Particle addition and synchronous data acquisition: Start the particle addition device and add particles into the pipeline before the inlet of the transparent observation section according to the set addition rate. The solid phase mass concentration can be calculated using formula C. m =q s / (ρ·Q + q s Estimate by 100% (q) s The acceleration rate is the particle mass feed rate. The data acquisition system simultaneously records the flow rate Q and the pressure p at each measuring point. i With the trigger signal of a high-speed camera, the high-speed camera system records the processes of particle initiation, rolling, jumping, suspension, deposition, bridging, and clogging.

[0047] Pressure Loss and Blockage Determination: The pressure loss between the inlet and outlet of the transparent observation pipe section can be determined by Δp=p in -p out The pressure loss before and after a local configuration component can be calculated as Δp. s = p up -p down Calculation. Based on synchronously acquired data, when pressure loss continuously increases and flow rate decreases within a short period of time, and the image shows particles forming bridging or fixed sedimentation beds in local areas, it is determined that blockage has occurred in this operating condition.

[0048] Particle recovery and post-processing: After the experiment, the particle feeding device and delivery pump were turned off. The discharged particles were removed from the filter, and the residual particles in the transparent observation tube were rinsed and recovered. The discharged particles and residual particles were dried, weighed, and sieved to obtain the dry mass m of the discharged particles. out and residual particle dry mass m r .

[0049] Evaluation index calculation: Sand carrying rate is calculated as η=m out Calculated as / m0×100%; residual rate is calculated as R = m r / m0×100%; the mass balance closure degree is calculated according to B= (m out + m r The calculation is based on 100% of the volume of the solid phase (m0). For a given pipe diameter, solid concentration, and experimental duration, the flow rate is gradually varied. When particles can be stably discharged and a continuously growing fixed sedimentary bed does not form inside the pipe, the corresponding flow rate can be taken as the stable sand-carrying velocity. The critical sand-carrying velocity is determined through interpolation or grading tests. For multi-size or mixed-graded particles, the maximum stable sand-carrying particle size can be determined based on the sieving results.

[0050] (3) Analysis of experimental results and plotting of curves like Figure 2 The diagram shows the data acquisition and evaluation process for liquid-solid two-phase particle transport experiments conducted by the device described in this application. Based on the synchronously acquired results, flow velocity-pressure loss curves, flow velocity-sand carrying capacity curves, particle size-residue rate curves, solid phase concentration-clogging time curves, and pipe diameter-maximum stable sand carrying particle size relationship curves can be plotted.

[0051] At low flow rates, particles mainly exhibit rolling and intermittent transitions, easily forming a sedimentary bed at the pipe bottom, resulting in low sand carrying capacity and high residue rate. As flow rates increase, the proportion of particle transitions and suspensions increases, leading to a higher mass of discharged particles and a significantly improved sand carrying capacity. When the flow rate continues to rise to a stable sand-carrying range, the number of residual particles in the pipe decreases, and the pressure loss tends to stabilize. For localized narrowing conditions, particle retention is likely to occur at the leading edge of the narrowing section and the trailing edge of the expansion section. The smaller the narrowing ratio, the greater the local pressure loss and the higher the risk of bridging and blockage.

[0052] The above experimental results can be used to determine the safe sand-carrying capacity of low-level brine discharge pipelines in salt caverns under different pipe diameters and flow rates, and provide experimental parameters for the selection of brine discharge pipe diameter, brine discharge flow control, particle ingress risk assessment, and prevention of local blockages during on-site brine discharge.

[0053] Although the embodiments of this application have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for this application. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, this application is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A visual experimental device for particle transport in solid-phase flow of low-level brine in salt caverns, characterized in that, include: A closed-loop pipeline system includes a storage tank, a transfer pump, a flow meter, a transparent observation section, and a return pipeline that are connected in sequence to allow the brine to circulate continuously in the pipeline. A particle dosing device is installed downstream of the flow meter and upstream of the transparent observation pipe section, and is used to quantitatively add solid particles into the pipeline at a set rate. A local configuration component, detachably mounted in the middle of the transparent observation tube segment, is used to simulate at least one of the following pipe morphologies: equal diameter connection, reduced diameter transition, and local deposition. The synchronous acquisition system includes the flow meter, pressure measuring points arranged along the transparent observation pipe section, and a high-speed camera device set beside the transparent observation pipe section, for synchronously recording pipeline flow, pressure at each measuring point, and images of particle movement inside the pipe; A particle recovery and processing unit is located after the outlet of the transparent observation tube section to intercept and recover discharged particles.

2. The visual experimental device for solid-phase flow and particle transport of low-level brine in salt caverns according to claim 1, characterized in that, The transparent observation tube section is configured to be detachable and replaceable with tube sections of different inner diameters. The transparent observation tube sections of different inner diameters are replaced and connected using a unified flange connection interface, sealing gasket and transition joint. The inner wall of each tube section splice is ground smooth.

3. The visual experimental device for solid-phase flow and particle transport of low-level brine in salt caverns according to claim 2, characterized in that, The transparent observation tube segment is made of PMMA material, with length markings on its outer wall and a backlight source. The backlight source is located on the opposite side of the high-speed camera device to enhance the contrast of the particle motion image.

4. The visual experimental device for solid-phase flow and particle transport of low-level brine in salt caverns according to claim 1, characterized in that, The pellet feeding device includes a feeding hopper, a screw conveyor mechanism, a frequency conversion speed regulation mechanism, and a weighing feedback mechanism. The weighing feedback mechanism is used to record changes in the feeding mass in real time, and the screw conveyor mechanism is used to stably convey pellets at a target rate.

5. The visual experimental device for solid-phase flow and particle transport of low-level brine in salt caverns according to claim 1, characterized in that, The local configuration component includes a constant diameter connecting section, an abrupt diameter reduction section, a gradually narrowing diameter reduction section, or a local deposition simulation section, wherein the diameter reduction ratio of the diameter reduction section is 0.9D, 0.8D, 0.7D, or 0.6D.

6. The visual experimental device for solid-phase flow and particle transport of low-level brine in salt caverns according to claim 1, characterized in that, The pressure measuring points are arranged at least one of the following locations: the outlet of the delivery pump, the inlet of the transparent observation tube section, the outlet of the transparent observation tube section, and the front and rear sides of the partial configuration assembly.

7. The visual experimental device for particle transport in the solid-phase flow of low-level brine in salt caverns according to claim 1, characterized in that, The particle recovery and processing unit includes a filter, a sedimentation and recovery tank, a drying device, a weighing device, and a screening device, which are used to intercept, recover, dry, weigh, and screen the discharged particles and the residual particles in the pipe, respectively.

8. The visual experimental device for solid-phase flow and particle transport of low-level brine in salt caverns according to claim 1, characterized in that, It also includes a transparent protective cover, which covers the outside of the transparent observation tube section.

9. A method for conducting a low-level brine particle transport test in a salt cavern using the apparatus described in any one of claims 1 to 8, characterized in that, Includes the following steps: Add brine to the storage tank and start the delivery pump to circulate the brine in the closed-loop pipeline system; Select a transparent observation tube segment with the target inner diameter and install it in the pipeline. Then, install the target local configuration component in the middle of the transparent observation tube segment according to the test requirements. Adjust the operating frequency of the delivery pump to make the brine in the pipe reach the target average flow rate; Start the particle feeding device to add solid particles quantitatively into the brine stream at a set rate, forming a solid-liquid mixture that enters the transparent observation tube section; Simultaneously collect and record pipeline flow data, pressure data at each pressure measuring point, and particle motion image data captured by a high-speed camera; Based on synchronously acquired data, when the pressure loss increases continuously in a short period of time and the flow rate decreases, and the image shows that particles form bridging or fixed sedimentation beds in local areas, it is determined that a blockage has occurred in this operating condition.

10. The method according to claim 9, characterized in that, It also includes the following post-processing steps: After the experiment, the discharged particles and residual particles in the pipe were collected by the particle recovery and treatment unit, and then dried, weighed, and sieved to obtain the dry mass m of the discharged particles. out and residual particle dry mass m r ; The sand carrying rate η is calculated using the following formula: η = m out / m0×100%, where m0 is the initial dry mass of the added particles; The residual rate R is calculated using the following formula: R = m r / m0×100%; By gradually changing the average flow velocity inside the pipe, the lowest flow velocity at which particles can be stably discharged and a continuously growing fixed sedimentary bed does not form inside the pipe is determined as the stable sand-carrying flow velocity.

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