A tracer particle active recovery and redispersion device and method for PIV experiments

Abstract

The present application belongs to the technical field of particle recovery, and particularly relates to a tracer particle active recovery and redispersion device and method for PIV experiment, aiming at solving the problem that the existing particle recovery device cannot be applied to microgravity environment. The device provided by the present application comprises a particle trapping cabin, and a cyclone pre-separation zone, a deflection trapping unit, an electrostatic trapping unit and a filtration unit are sequentially arranged in the particle trapping cabin along the flow direction of recovery gas. The recovery gas enters the cyclone pre-separation zone through a tangential inlet and forms a cyclone. The deflection trapping unit has a turning channel to change the flow direction of the recovery gas. The electrostatic trapping unit is used for trapping charged particles in the recovery gas, and comprises a dust collecting electrode and a counter electrode opposite to the dust collecting electrode. The filtration unit is used for trapping particles in the recovery gas. The device provided by the present application does not rely on gravity sedimentation, can reduce the influence of residual particles in the experiment on subsequent PIV measurement, and is suitable for microgravity environment.

Description

Technical Field

[0001] This invention belongs to the field of particle recovery technology, specifically relating to an active recovery and redispersion device and method for tracer particles used in PIV experiments. Background Technology

[0002] PIV (Positive Induction Vibration) technology uses laser illumination to illuminate tracer particles in a flow field and records the displacement changes of the particles using images to obtain flow velocity information. The concentration, spatial distribution, and residual state of the tracer particles directly affect the accuracy and repeatability of PIV measurements.

[0003] In normal gravity environments, after a PIV experiment, tracer particles are typically recovered by gradually settling under gravity. However, in microgravity environments such as space stations, the residual gravity level is much lower than Earth's gravity. Tracer particles, lacking effective settling channels, remain suspended for extended periods in sealed experimental chambers, combustion chambers, observation chambers, or recirculation gas paths. This leads to the following problems: First, residual particles raise the initial concentration background for subsequent PIV experiments, making it difficult to distinguish between effective tracer particles and residual particles. Second, suspended particles easily adhere to the surfaces of optical windows, laser incident windows, reflectors, or camera observation windows, resulting in enhanced scattering, decreased transmittance, and reduced image signal-to-noise ratio. Third, particles entering the experimental chamber's ventilation or recirculation gas paths may increase filter load, cause gas path blockage, or increase dust content. Fourth, particle aggregation in nozzles, pipes, and orifice structures can affect the boundary conditions and repeatability of subsequent experiments. However, conventional particle recovery devices are unsuitable for microgravity environments and cannot meet experimental requirements. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, namely the inability of existing particle recovery devices to be used in microgravity environments, this invention provides a device and method for the active recovery and redispersion of tracer particles for PIV experiments.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: An active recovery and redispersion device for tracer particles in PIV experiments includes a particle trapping chamber, which is provided with a tangential inlet and a gas flow outlet. The particle collection chamber is equipped with a swirling pre-separation zone, a baffle collection unit, an electrostatic collection unit, and a filtration unit arranged sequentially along the direction of the recovered gas flow. The recovered gas enters the swirling pre-separation zone through the tangential inlet and forms a swirling flow. The deflection trapping unit has a deflection channel to change the direction of the recovered gas flow; The electrostatic collection unit is used to collect charged particles in the gas and includes a dust collection electrode and a counter electrode opposite to the dust collection electrode. The filtration unit is used to trap particles in the recovered gas; The recovered gas is discharged from the gas outlet after passing through the filter unit.

[0006] Furthermore, the particle trapping chamber is also equipped with a backflush air inlet and a redispersion outlet; In redispersion mode, backflush gas enters the particle collection chamber through the backflush gas inlet and flows through the electrostatic collection unit, thereby carrying the particles collected by the electrostatic collection unit out of the redispersion outlet.

[0007] Furthermore, the particle trapping chamber is also provided with a first trapping tank, which is opened on the inner wall of the particle trapping chamber and located in the swirling pre-separation zone.

[0008] Furthermore, the deflector trapping unit includes a plurality of parallel deflector plates, which are staggered to form the deflection channel.

[0009] Furthermore, a second collection groove is provided on the inner wall of the reversing channel.

[0010] Furthermore, the dust collection electrode is configured as a plate electrode, a comb-shaped electrode, a cylindrical electrode, or a mesh electrode.

[0011] Furthermore, the active recovery and redispersion device for tracer particles used in PIV experiments also includes a desorption unit, which is used to drive the particles captured on the dust collection electrode to detach from the dust collection electrode.

[0012] Furthermore, the desorption unit is configured as a vibrating plate, a piezoelectric plate, or a pulsed airflow generator.

[0013] In another aspect, the present invention provides a method for active recovery and redispersion of tracer particles for PIV experiments, employing the aforementioned active recovery and redispersion device for PIV experiments, comprising the following steps: Receive recycling command: The control unit generates a recycling mode switching command; Switch to recovery mode: suction is performed through the airflow outlet, and a collection voltage is applied to the electrostatic collection unit; Swirl and deflector pre-capture: The recovered gas enters the particle capture chamber through the tangential inlet, forms a swirling flow in the swirling pre-separation zone, and then flows through the deflector channel; Electrostatic capture and end-of-line filtration: The pre-captured recovered gas enters the electrostatic capture unit, where particles migrate toward the dust collection electrode in the electric field formed by the dust collection electrode and the counter electrode; then the recovered gas passes through the filtration unit, where the remaining particles in the recovered gas are trapped. Determine the recovery status: The control unit determines whether the recovery process has reached the termination condition based on the preset recovery time, external residual particle status signals, or experimental cabinet control commands; Switch to redispersion mode: When the particles captured in the electrostatic collection unit meet the preset reuse conditions and need to be returned, stop applying the collection voltage to the dust collection electrode. In-situ desorption and recirculation: Backflush gas is introduced through the backflush gas inlet, and the backflush gas flows through the electrostatic capture unit to carry the particles captured by the electrostatic capture unit and discharge them from the redispersion outlet to the particle generator or storage unit.

[0014] Furthermore, in the step of determining the recovery status, the external residual particle status signal comes from the concentration monitoring unit or the external image processing unit connected to the PIV camera; the experimental cabinet control command is a stop recovery command issued by the experimental cabinet control system according to the experimental sequence, the start requirements of the next experimental stage, or manual operation. The control unit determines the end of recycling based on any of the following conditions: the cumulative recycling time reaches the preset recycling duration, the effective detection cycle of the external residual particle state signal for a preset number of consecutive times meets the preset cleaning completion condition, or a stop recycling command is received from the experimental cabinet control system.

[0015] In summary, the technical effects achieved by this invention are as follows: The active recovery and redispersion device for tracer particles in PIV experiments provided by this invention includes a particle collection chamber with a tangential inlet and a gas flow outlet. Inside the particle collection chamber, along the direction of the recovered gas flow, a swirling pre-separation zone, a baffled collection unit, an electrostatic collection unit, and a filtration unit are arranged sequentially. The recovered gas enters the swirling pre-separation zone through the tangential inlet and forms a swirling flow. The baffled collection unit has a deflection channel to change the direction of the recovered gas flow. The electrostatic collection unit is used to collect charged particles in the recovered gas and includes a dust collection electrode and a counter electrode opposite to the dust collection electrode. The filtration unit is used to trap particles in the recovered gas. The recovered gas is discharged from the gas flow outlet after passing through the filtration unit.

[0016] This invention establishes a tangential inlet in the particle trapping chamber, allowing the recovered gas to enter the swirling pre-separation zone and form a swirling flow. The gas then sequentially passes through a baffle trapping unit, an electrostatic trapping unit, and a filtration unit along its flow direction. The swirling pre-separation zone induces particles in the recovered gas to migrate towards the walls of the particle trapping chamber under the influence of the swirling flow. The baffle trapping unit uses a deflection channel to alter the flow direction of the recovered gas for pre-trapping. The electrostatic trapping unit uses an electric field formed by the dust collection electrode and the counter electrode to trap charged particles in the recovered gas. The filtration unit traps any remaining particles in the recovered gas, which are then discharged through the air outlet after passing through the filtration unit. Therefore, this invention can establish an active recovery pathway for tracer particles after PIV experiments without relying on natural sedimentation. It achieves multi-stage processing of swirling pre-separation, baffle trapping, electrostatic trapping, and filtration, reducing the impact of residual tracer particles on the PIV experimental area and the initial particle background of subsequent experiments. Furthermore, it eliminates the need for high-flow-rate ventilation, minimizing disturbance to the PIV experimental environment. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the active recovery and redispersion device for PIV experiments provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the flow direction of the recovered gas in the recovery mode; Figure 3 A schematic diagram of an electrostatic trapping unit capturing particles; Figure 4 This is a schematic diagram of particle redispersion in an electrostatic trapping unit. Figure 5 This is a schematic diagram showing the connection between the active recovery and redispersion device for tracer particles used in PIV experiments and the PIV experimental system. Figure 6 This is a schematic flowchart of a method for active recovery and redispersion of tracer particles for PIV experiments provided in an embodiment of the present invention.

[0019] Explanation of reference numerals in the attached drawings: 100, Particle collection chamber; 110, Tangential inlet; 120, Swirl pre-separation zone; 130, First collection tank; 200, Baffle collection unit; 210, Baffle plate; 220, Connecting plate; 201, Second collection tank; 300, Electrostatic collection unit; 310, Dust collection electrode; 320, Counter electrode; 330, High-voltage power supply; 400, Filtration unit; 410, Filter housing; 420, Filter membrane; 500, Desorption unit; 600, Cover; 700, Control unit; 810, Recovery pipe; 820, Suction pipe; 830, Backflush pipe; 840, Redispersion pipe; 850, First switching valve; 860, Second switching valve; 870, Third switching valve; 10, Particle generator; 20, PIV experimental area; 30, PIV camera; 40, Laser; 50, Concentration monitoring unit; 60, Experiment cabinet control system. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0022] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0023] The following combination Figures 1-6 The structure and shape of the active recovery and redispersion device for tracer particles used in PIV experiments provided in this embodiment are described in detail below: The active recovery and redispersion device for tracer particles in PIV experiments provided in this embodiment includes a particle trapping chamber 100, which is provided with a tangential inlet 110 and a gas flow outlet. Inside the particle trapping chamber 100, along the direction of the recovered gas flow, are sequentially arranged a swirling pre-separation zone 120, a baffle trapping unit 200, an electrostatic trapping unit 300, and a filtration unit 400, as follows: Figure 1As shown. The recovered gas enters the swirling pre-separation zone 120 through the tangential inlet 110 and forms a swirling flow. It then sequentially passes through the baffle trapping unit 200, the electrostatic trapping unit 300, and the filter unit 400, and is discharged from the gas outlet after passing through the filter unit 400. Figure 2 As shown.

[0024] In this embodiment, the recovered gas is a particle-containing gas discharged from the PIV experimental area 20. The particles can be TiO2, SiC, Al2O3, hollow glass microspheres, polystyrene fluorescent microspheres, or other solid tracer particles suitable for PIV measurement. The particle trapping chamber 100 can be made of a composite structure of stainless steel, aluminum alloy, transparent pressure-resistant material, or an inner anti-adhesion layer. Among them, transparent ceramic can be selected as the transparent pressure-resistant material. In order to balance the swirling effect and the convenience of processing and maintenance, the position of the swirling pre-separation zone 120 in the particle trapping chamber 100 can be a cylindrical or near-cylindrical cavity to facilitate the flow of the recovered gas along the inner wall of the particle trapping chamber 100 to form a swirling flow; the position of the baffle trapping unit 200, the electrostatic trapping unit 300, and the filter unit 400 in the particle trapping chamber 100 can be a rectangular cavity to simplify the installation, positioning, disassembly, and maintenance of the baffle trapping unit 200, the electrostatic trapping unit 300, and the filter unit 400.

[0025] In this embodiment, the tangential inlet 110 is located on the side wall of the particle trapping chamber 100 and communicates with the residual particle recovery port of the PIV experimental area 20. The centerline of the tangential inlet 110 is offset relative to the radial direction of the particle trapping chamber 100, so that the recovered gas flows tangentially along the chamber wall after entering the particle trapping chamber 100 and forms a swirling flow in the swirling pre-separation zone 120. Since tracer particles lack natural sedimentation channels under microgravity conditions, the confined swirling flow is used to make larger particles or agglomerates migrate towards the inner wall of the particle trapping chamber 100 under centrifugal migration, instead of relying on particles to settle to the bottom of the chamber under gravity.

[0026] In this embodiment, the particle trapping chamber 100 is further provided with a first trapping groove 130, which is formed on the inner wall of the particle trapping chamber 100 and located in the swirling pre-separation zone 120. Specifically, the first trapping groove 130 can be an arc-shaped groove segment that extends circumferentially and is radially recessed on the inner peripheral wall of the particle trapping chamber 100, with the groove opening facing inward. The first trapping groove 130 is located in an area where particles under the influence of swirling currents tend to migrate towards and collide with the peripheral wall, so that larger particles or agglomerates, after entering the first trapping groove 130, are retained by the geometric shielding at the edge of the first trapping groove 130, the local low-velocity zone inside the groove, and the adhesion between the particles and the wall surface. Specifically, multiple first trapping grooves 130 can be provided to fully trap particles.

[0027] In this embodiment, the baffle trapping unit 200 is located downstream of the cyclone pre-separation zone 120 and has a deflection channel to change the flow direction of the recovered gas. Specifically, the baffle trapping unit 200 includes multiple parallel baffles 210, which are staggered to form a deflection channel. The deflection channel can be configured as a continuous S-shaped channel, causing the recovered gas to undergo multiple 180° turns as it passes through the baffle trapping unit 200.

[0028] Furthermore, the baffle trapping unit 200 also includes a connecting plate 220, which forms an annular frame, and the baffles 210 are installed within the annular frame. Depending on the shape of the particle trapping chamber 100, the annular frame can be either circular or rectangular. One end of each baffle 210 is fixed to the connecting plate 220, while the other end has a gap for airflow to change direction. The gaps between adjacent baffles 210 are alternately arranged, allowing the recovered gas to bypass each baffle 210 and form a continuous tortuous path. The baffles 210 are connected as a whole by the connecting plate 220, improving maintainability. During maintenance, the entire baffle trapping unit 200 can be removed for cleaning or replacement. Correspondingly, an inspection port can be opened on the top of the particle trapping chamber 100 for removing and placing the baffle trapping unit 200 and cleaning the first trapping tank 130; a detachable inspection cover is also provided to seal the inspection port and ensure normal operation.

[0029] In this embodiment, the recovered gas containing particles changes direction when it bypasses the baffle 210. Larger particles or agglomerates, due to inertia, cannot completely turn synchronously with the airflow, thus deviating from the airflow streamline and impacting the windward side of the baffle 210. The side directly facing the local incoming flow is the windward side. A second trapping groove 201 is provided on the inner wall of the deflection channel. The second trapping groove 201 can be set on the windward side of the baffle 210 or at the airflow turning point, with its opening facing the incoming flow direction or obliquely set relative to the incoming flow; similarly, the connecting plate 220 is also provided with a second trapping groove 201. After larger particles or agglomerates impact the windward side or enter the second trapping groove 201, they are trapped by geometric shielding, local low velocity, and wall adhesion. Particles not trapped by the second trapping groove 201 continue to enter the downstream electrostatic collection unit 300 with the airflow.

[0030] In this embodiment, the electrostatic collection unit 300 is used to collect charged particles in the recovered gas. It includes a dust collection electrode 310, a counter electrode 320 opposite to the dust collection electrode 310, and a high-voltage power supply 330. The dust collection electrode 310 and the counter electrode 320 can be mounted in the particle collection chamber 100 via insulating supports. An electrostatic collection channel for the recovered gas to pass through is formed between the dust collection electrode 310 and the counter electrode 320. Figure 2As shown. In recycling mode, the high-voltage output terminal of the high-voltage power supply 330 is connected to the dust collection electrode 310 via a high-voltage lead. The loop terminal of the high-voltage power supply 330 is grounded and connected to the counter electrode 320, keeping the counter electrode 320 at ground potential or reference potential. This creates an electrostatic trapping electric field between the dust collection electrode 310 and the counter electrode 320, as shown. Figure 3 As shown, the electrode spacing, applied voltage, collection channel width, and gas flow velocity can be selected based on the charge state, particle size range, dielectric properties, insulation requirements, and allowable voltage drop of the tracer particles. In recovery mode, the already charged tracer particles migrate and adhere to the collection surface of the dust collection electrode 310 under the action of the electric field force; for insulating particles capable of induced polarization, they can also migrate to the collection area under dielectric electrophoresis in a non-uniform electric field. The remaining particles that are not electrostatically collected continue to enter the downstream filtration unit 400. The dust collection electrode 310 forms a collection surface on the side facing the opposing electrode 320. In this embodiment, the dust collecting electrode 310 and the counter electrode 320 can be arranged in a direction perpendicular to the flow direction of the recovery airflow, such as... Figure 2 As shown; it can also be arranged along the direction of the recovered airflow, such as Figure 3 , Figure 4 As shown. Accordingly, the dust collecting electrode 310 and the counter electrode 320 are configured as plate electrodes, comb electrodes, cylindrical electrodes or mesh electrodes to leave channels for particles to pass through.

[0031] In this embodiment, the filtration unit 400 is disposed downstream of the electrostatic collection unit 300 and is used to trap residual particles in the recovered gas. The filtration unit 400 includes a filter housing 410 and a filter membrane 420, the filter membrane 420 being installed inside the filter housing 410, such as... Figure 1 As shown, the gas is filtered through filter membrane 420 to form clean gas. Filter membrane 420 is used to retain tracer particles within the target particle size range. Filter membrane 420 can be a PTFE microporous membrane, porous ceramic membrane, glass fiber filter membrane, electrospun fiber membrane, multilayer composite filter material, or other filter media compatible with the tracer particle material and experimental atmosphere. Micropores refer to the fine pores or equivalent flow channels in filter membrane 420 or other porous filter media, not the openings on the housing of filter unit 400. In this embodiment, filter membrane 420 can be arranged in a flat, pleated, or multilayer stacked manner. When it is necessary to reduce pressure drop or extend maintenance cycle, a pleated filter membrane 420 can be used to increase the effective filtration area. The material, pore structure, and effective filtration area of ​​filter membrane 420 are selected according to the target particle size range, allowable pressure drop, suction flow rate, experimental atmosphere, and maintenance cycle.

[0032] In this embodiment, the particle trapping chamber 100 is provided with a maintenance port for replacing the filter unit 400. Correspondingly, a cover 600 is provided, which is detachably connected to the particle trapping chamber 100 to close the maintenance port and abut against the filter housing 410, thereby ensuring the positioning and fixation of the filter unit 400. Simultaneously, an annular positioning platform is provided on the inner wall of the particle trapping chamber 100. The two positioning platforms cooperate to restrict the vertical movement of the filter unit 400 and form a sealed contact with the filter housing 410 to ensure that airflow only passes through the filter membrane 420. The filter housing 410 can be configured as a frame structure to facilitate the installation of the filter membrane 420 and ensure airflow passage. The cover 600 can be connected to the particle trapping chamber 100 via threaded connection, snap-fit ​​connection, locking connection, or clamp connection, and a sealing element is provided between the cover 600 and the particle trapping chamber 100 to ensure airtightness.

[0033] To facilitate the installation of the filter unit 400, a chamfer can be provided on the filter housing 410 to guide the filter housing 410 into the particle collection chamber 100.

[0034] In this embodiment, a differential pressure sensor is also provided. The differential pressure sensor has two independent pressure ports, which are connected upstream and downstream of the filter unit 400 respectively through pressure tapping pipes. This allows the filtration load and clogging trend of the filter unit 400 to be determined based on the differential pressure, the rate of change of differential pressure, and the current suction status. The range and maintenance conditions of the differential pressure sensor can be determined based on the material of the filter membrane 420, the effective filtration area, the suction flow rate, and the initial differential pressure of the clean filter element. In this embodiment, multiple filter units 400 can be arranged in parallel. When the differential pressure reaches the preset maintenance conditions, the filter unit 400 is replaced or a backup filter unit 400 is switched.

[0035] In this embodiment, the airflow outlet is located downstream of the filter unit 400 and is connected to the suction pipe 820. The suction pipe 820 can be connected to an existing negative pressure pipeline in the experimental cabinet, a miniature vacuum pump, or other low-disturbance suction source to create negative pressure.

[0036] In this embodiment, the particle trapping chamber 100 is also provided with a backflush air inlet and a redispersion outlet, such as Figure 1 As shown, the backflush gas inlet is used to introduce backflush gas, which can be dry nitrogen, dry air, or other gases compatible with the experimental environment and tracer particles. The redisperm outlet is used to discharge the redisperm gas containing desorbed particles. In redisperm mode, the backflush gas enters the particle collection chamber 100 through the backflush gas inlet and flows through the electrostatic collection unit 300, thereby carrying the particles collected by the electrostatic collection unit 300 out of the redisperm outlet. The redisperm outlet is connected to the redisperm pipe 840, allowing the particles to enter the particle generator 10 or the intermediate storage unit. It should be noted that the remaining particles retained by the filter membrane 420 serve as a final safety guarantee and do not enter the redisperm return path.

[0037] In this embodiment, the backflush gas inlet and the redispersion outlet are located in the area where the electrostatic collection unit 300 is located, and the flow direction of the backflush gas is perpendicular to the flow direction of the recovered gas flowing through the electrostatic collection unit 300, such as... Figure 4 As shown, the dashed arrow indicates the direction of the backflush gas flow, and the solid arrow indicates the direction in which particles leave the dust collection electrode 310.

[0038] The active recovery and redispersion device for tracer particles in PIV experiments provided in this embodiment also includes a desorption unit 500, which is used to cause particles captured on the dust collection electrode 310 to detach from the dust collection electrode 310. The desorption unit 500 can be configured as a vibrating plate, a piezoelectric plate, or a pulsed airflow generator. When the desorption unit 500 is configured as a vibrating plate or a piezoelectric plate, it can be mechanically coupled with the dust collection electrode 310 or its supporting structure to generate low-amplitude vibrations in redispersion mode, causing particles on the collection surface to loosen and detach. When the desorption unit 500 is configured as a pulsed airflow generator, it can output short-term pulsed airflow to the collection surface of the dust collection electrode 310, which, in conjunction with the backflushing airflow, promotes particle desorption.

[0039] For tracer particles with stable charge characteristics, if the polarity, amplitude and duration of the reverse pulse have been determined through ground tests to reduce electrostatic adhesion of particles without causing secondary capture or abnormal discharge, a short-term reverse pulse can be applied to the dust collection electrode 310 before or during backflushing as an auxiliary desorption measure.

[0040] In this embodiment, the active recovery and redispersion device for tracer particles used in PIV experiments further includes a recovery pipe 810 and a backflush pipe 830. The recovery pipe 810 is connected to the tangential inlet 110 for introducing the recovery gas; the backflush pipe 830 is connected to the backflush gas inlet for introducing the backflush gas. A first switching valve 850 is provided on the suction pipe 820 for controlling the opening and closing of the suction pipe 820; a second switching valve 860 is provided on the redispersion pipe 840 for controlling the opening and closing of the redispersion pipe 840; and a third switching valve 870 is provided on the backflush pipe 830 for controlling the opening and closing of the backflush pipe 830.

[0041] In recovery mode, the second switching valve 860 and the third switching valve 870 are closed, the first switching valve 850 is open, and recovery gas is introduced through the recovery pipe 810. Simultaneously, a low-flow suction is introduced through the suction pipe 820 to guide the gas flow. The recovery gas enters through the tangential inlet 110 and flows sequentially through the cyclone pre-separation zone 120, the deflection channel of the baffle collection unit 200, the collection channel of the electrostatic collection unit 300, and the filter unit 400, before being discharged through the suction pipe 820. Figure 2 As shown, a residual particle recovery pathway that does not rely on natural sedimentation is established through low-flow active suction, tangential air intake, and a trapping structure.

[0042] For PIV experiments in microgravity environments, tracer particles are both a necessary medium for measurement and potentially residual particles that can affect subsequent experiments. Using conventional filtration methods can easily increase local flow resistance and cause rapid overloading of the filter media; using high-flow-rate suction or conventional cyclone separation can easily alter the flow field being measured or the atmosphere inside the experimental chamber. The tracer particle active recovery and redispersion device for PIV experiments provided in this embodiment forms a technical chain through physical mechanism switching and multi-stage collaborative classification. This chain includes low-disturbance active recovery, pre-capture of larger particles or agglomerates, electrostatic capture of some small and medium-sized particles, judgment of post-capture reuse conditions, in-situ desorption by fixed electrodes, directional return, and end-filter status monitoring. While ensuring measurement accuracy, it achieves closed-loop, low-disturbance, and high-cleanliness management of tracer particles, enabling efficient capture at low flow rates and low gas velocities. Specifically, the swirling pre-separation and deflector trapping unit 200 utilizes the microgravity environment, eliminating the need for gravity settling. It relies solely on the limited inertial force generated by the confined swirling flow and multiple sharp turns, combined with the geometric shielding and wall adhesion effects of the trapping tank, to effectively deflect and retain larger particles or agglomerates, thus significantly reducing the load on the end-filter. The electrostatic trapping unit 300 makes electric field force replace pneumatic drag force as the dominant driving force. The low air velocity prolongs the residence time of particles in the electric field, enhancing the migration and adhesion effect. In particular, by not employing a high-speed rotating rotor, gravity ash hopper, or large-stroke reciprocating mechanism, it helps reduce mechanical vibration and large-flow aerodynamic disturbances introduced during operation, making it more suitable for the closed, small-volume, and flow-field-sensitive microgravity PIV experimental environment.

[0043] When the particles captured by the electrostatic collection unit 300 meet the preset reuse conditions and need to be returned, the first switching valve 850 is closed, the high-voltage power supply 330 stops applying the collection voltage to the dust collection electrode 310, and the system enters the redispersion mode. Figure 4 As shown. In the redispersion mode, after the dust collection electrode 310 completes the discharge, the second switch valve 860 and the third switch valve 870 are opened. The backflush gas flows along the collection surface of the dust collection electrode 310. At the same time, the desorption unit 500 works briefly to desorb the collected particles in situ. The desorbed particles enter the redispersion pipe 840 from the redispersion outlet with the backflush airflow, and then enter the particle generator 10 or the intermediate storage unit.

[0044] The preset reuse conditions can be determined based on the particle batches and experimental records used in this round of experiments, and must meet the following conditions: the captured particles are the same as or compatible with the particle materials and particle size grades to be used in subsequent experiments; no incompatible combustion products, droplets, condensates, or other particles are mixed in during the experiment; the cumulative number of uses or returns does not exceed the preset upper limit; and the use of recycled particles is permitted in subsequent experiments. The above information can be determined by experimental task parameters, particle batch records, usage records, operator instructions, or instructions from the experimental cabinet control system 60. When the captured particles do not meet the preset reuse conditions, it cannot be confirmed whether the preset reuse conditions are met, or return is not required, the second switch valve 860 and the third switch valve 870 remain closed, and the redispersion and return process is not initiated.

[0045] The PIV experimental system includes a particle generator 10, a PIV experimental area 20, a PIV camera 30, a laser 40, a concentration monitoring unit 50, and an experimental cabinet control system 60. The particle output end of the particle generator 10 is connected to the PIV experimental area 20 to provide tracer particles to the PIV experimental area 20. The residual particle recovery port of the PIV experimental area 20 is connected to the tangential inlet 110 of the particle trapping chamber 100. The gas flow outlet of the particle trapping chamber 100 is connected to the experimental cabinet suction pipeline, a micro vacuum pump, or other low-disturbance suction source via a suction pipe 820. The output path of the particle generator 10 and the redistribution return pipeline use different interfaces and different pipelines to avoid using the same bidirectional pipeline for both release and return, thereby reducing the impact of returned particles on the stability of the particle release end and facilitating independent control of the release and return paths through valves or interface structures. PIV camera 30 is used to acquire images of PIV experimental area 20, laser 40 is used to provide sheet light source illumination for PIV experimental area 20, concentration monitoring unit 50 can be used to provide residual particle state signals, and experimental cabinet control system 60 can be used to provide experimental stage, start, stop or cleanup commands.

[0046] In this embodiment, the tracer particle active recovery and redispersion device for PIV experiments also includes a control unit 700, such as... Figure 5 As shown, the control unit 700 is connected to the PIV camera 30, concentration monitoring unit 50, experimental cabinet control system 60, high-voltage power supply 330, desorption unit 500, first switching valve 850, second switching valve 860, and third switching valve 870 via signal connections, indicated by dashed arrows in the figure. The PIV camera 30, concentration monitoring unit 50, and experimental cabinet control system 60 can send external status or control signals to the control unit 700; the control unit 700 sends execution commands to the high-voltage power supply 330, desorption unit 500, first switching valve 850, second switching valve 860, and third switching valve 870, respectively.

[0047] In recovery mode, particles in the PIV experimental area 20 are captured after entering the particle trapping chamber 100, and the gas is filtered by the filter unit 400 and discharged by the first switching valve 850. In redispersion mode, the particles captured by the electrostatic trapping unit 300 are desorbed and discharged by the second switching valve 860 with the backflushing gas, and then return to the particle generator 10.

[0048] This embodiment proposes a method for active recovery and redispersion of tracer particles in PIV experiments. The active recovery and redispersion device for tracer particles in PIV experiments described above includes the following steps: S100, Receive Recovery Command. When the PIV experiment ends, the residual particle state in the PIV experimental area 20 reaches the preset recovery conditions, or the control unit 700 receives a cleaning command from the experimental cabinet control system 60, the control unit 700 generates a recovery mode switching command. The control unit 700 can simultaneously stop or reduce the particle release of the particle generator 10, so that the subsequent suction process mainly acts on the residual tracer particles after the experiment ends.

[0049] S200, switch to recovery mode. The control unit 700 draws gas through the air outlet and applies a collection voltage to the electrostatic collection unit 300. Specifically, the control unit 700 opens the first switching valve 850 and the low-disturbance suction source, closes the second switching valve 860 and the third switching valve 870, and controls the high-voltage power supply 330 to apply a DC collection voltage or a pulse collection voltage to the dust collection electrode 310, so that the device enters the recovery mode. In the recovery mode, the recovered gas flows sequentially along the tangential inlet 110, the cyclone pre-separation zone 120, the baffle collection unit 200, the electrostatic collection unit 300, the filter unit 400, and the air outlet.

[0050] S300, Swirl and Baffle Pre-Collection. The recovered gas enters the particle collection chamber 100 through the tangential inlet 110, forming a swirling flow within the swirling pre-separation zone 120. Larger particles or agglomerates migrate towards the inner wall of the particle collection chamber 100 under the influence of the confined swirling flow and may be retained in the first collection tank 130. Subsequently, the recovered gas flows through the deflection channel of the baffle collection unit 200, where the airflow changes direction multiple times within a continuous S-shaped channel or other tortuous channels. Larger particles or agglomerates, due to inertia, cannot completely change direction synchronously with the airflow and instead collide with the baffle plate 210 or enter the second collection tank 201 and are retained.

[0051] S400, electrostatic capture and end-of-line filtration. The pre-captured recovered gas enters the electrostatic capture unit 300. In the electric field formed by the collecting electrode 310 and the counter electrode 320, charged particles migrate towards and adhere to the collecting surface of the collecting electrode 310. After electrostatic capture, the recovered gas continues to pass through the filtration unit 400. The remaining particles in the recovered gas are trapped by the filter membrane 420 of the filtration unit 400, and the clean gas is discharged through the suction pipe 820. Thus, a multi-stage capture path is formed within the particle capture chamber 100, consisting of swirling pre-separation, baffled pre-capture, electrostatic capture, and end-of-line filtration.

[0052] S500, Determine the recovery status. The control unit 700 determines whether the recovery process has reached the end condition based on the preset recovery time, external residual particle status signals, or experimental cabinet control commands. Specifically, the external residual particle status signals may come from the concentration monitoring unit 50 or an external image processing unit connected to the PIV camera 30; the experimental cabinet control commands are stop recovery commands or cleaning completion commands issued by the experimental cabinet control system 60. The control unit 700 can determine the end of recovery based on any of the following situations: the cumulative recovery time reaches the preset recovery duration, the effective detection cycle of the external residual particle status signals for a preset number of consecutive cycles meets the preset cleaning completion condition, or the control unit receives a stop recovery command or cleaning completion command issued by the experimental cabinet control system 60. If the recovery is not completed, return to step S300 to continue the recovery; if the recovery is completed, further determine whether the particles captured in the electrostatic trapping unit 300 meet the preset reuse conditions and whether return is required. The detection results of the differential pressure sensor are used to determine the filter element load and maintenance status of the filter unit 400, and are not used as the basis for determining whether the residual particles in the PIV experimental area 20 have reached the cleaning requirements.

[0053] Among them, the effective detection cycle of the external residual particle state signal for a continuous preset number of times meets the preset cleaning completion condition means that the system will not stop immediately because the particle concentration is detected to be lower than the set value once. Instead, it requires that the results of multiple consecutive detections meet the standard before finally determining that the cleaning is complete.

[0054] S600, switch to redispersion mode. When the particles captured in the electrostatic collection unit 300 meet the preset reuse conditions and need to be returned, the control unit 700 stops applying the collection voltage to the dust collection electrode 310. Specifically, the control unit 700 closes the first switching valve 850, stops the high-voltage power supply 330 from applying the collection voltage to the dust collection electrode 310, and opens the second switching valve 860 and the third switching valve 870 after the discharge is completed, so that the device switches from the recycling mode to the redispersion mode. When the captured particles do not meet the preset reuse conditions, it cannot be confirmed whether the preset reuse conditions are met, or it is not necessary to return them, the control unit 700 keeps the second switching valve 860 and the third switching valve 870 closed, skipping the redispersion process; the particles are removed in the shutdown maintenance state and do not enter the redispersion tube 840 for return.

[0055] S700, in-situ desorption and recirculation. Backflush gas is introduced through the backflush gas inlet, flowing through the electrostatic collection unit 300, carrying the particles collected by the electrostatic collection unit 300 out through the redispersion outlet to the particle generator 10 or the storage unit. Specifically, the backflush gas flows through the collection surface of the dust collection electrode 310 and then flows towards the redispersion outlet, and the desorption unit 500 can be activated simultaneously to desorb the particles on the collection surface in situ; the desorbed particles are carried by the recirculation gas flow through the redispersion outlet and the second switching valve 860 into the particle generator 10 or the intermediate storage unit.

[0056] S800: Redispersion ends and filter element status is processed. After redispersion is complete, control unit 700 closes the second switching valve 860 and the third switching valve 870, restoring the device to standby or recovery state. Control unit 700 reads the detection results from the differential pressure sensor. When the filter element of filter unit 400 reaches the preset maintenance conditions, it prompts to replace filter unit 400 or switch to the spare filter unit 400.

[0057] In this embodiment, the recovery mode and the redispersion mode operate in a time-sharing manner. In the redispersion mode, the first switching valve 850 remains closed, thereby stopping the downstream suction effect from the electrostatic trapping unit 300 to the filtering unit 400, limiting the backflush airflow and desorbed particles from entering the filtering unit 400. Through the above-mentioned time-sharing switching and flow path interlocking, the recovery airflow and the redispersion airflow can be made to run along controlled paths respectively, reducing disturbance to the PIV experimental area 20 and preventing the reintroduction of particles trapped in the filtering unit 400 into the particle generator 10.

[0058] The tracer particle active recovery and redispersion device for PIV experiments provided in this embodiment can be applied to microgravity environments such as space station experimental cabinets, drop tower microgravity experimental devices, parabolic flight experimental platforms, recoverable satellite experimental platforms, and ground microgravity simulation experimental cabinets, achieving low-disturbance capture without relying on gravity settling.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for active recovery and redispersion of tracer particles for PIV experiments, characterized in that, Includes a particle trapping chamber (100), which is provided with a tangential inlet (110) and an airflow outlet; The particle collection chamber (100) is provided with a swirling pre-separation zone (120), a baffle collection unit (200), an electrostatic collection unit (300) and a filter unit (400) arranged sequentially along the direction of the recovered gas flow. The recovered gas enters the swirling pre-separation zone (120) through the tangential inlet (110) and forms a swirling flow; The deflection trapping unit (200) has a deflection channel to change the direction of the recovered gas flow; The electrostatic collection unit (300) is used to collect charged particles in the recovered gas, including a dust collection electrode (310) and a counter electrode (320) opposite to the dust collection electrode (310). The filtration unit (400) is used to trap particles in the recovered gas; The recovered gas is discharged from the gas outlet after passing through the filter unit (400).

2. The active recovery and redispersion device for tracer particles in PIV experiments according to claim 1, characterized in that, The particle trapping chamber (100) is also provided with a backflush air inlet and a redispersion outlet; In redispersion mode, backflush gas enters the particle trapping chamber (100) through the backflush gas inlet and flows through the electrostatic trapping unit (300), thereby carrying the particles trapped by the electrostatic trapping unit (300) out of the redispersion outlet.

3. The active recovery and redispersion device for tracer particles in PIV experiments according to claim 2, characterized in that, The particle trapping chamber (100) is also provided with a first trapping tank (130), which is located on the inner wall of the particle trapping chamber (100) and in the swirling pre-separation zone (120).

4. The active recovery and redispersion device for tracer particles in PIV experiments according to claim 2, characterized in that, The deflection trapping unit (200) includes a plurality of parallel deflection plates (210), which are staggered to form the deflection channel.

5. The active recovery and redispersion device for tracer particles in PIV experiments according to claim 4, characterized in that, A second collection trough (201) is provided on the inner wall of the reversing channel.

6. The active recovery and redispersion device for tracer particles in PIV experiments according to claim 2, characterized in that, The dust collection electrode (310) is configured as a plate electrode, a comb electrode, a cylindrical electrode, or a mesh electrode.

7. The active recovery and redispersion device for tracer particles in PIV experiments according to claim 2, characterized in that, It also includes a desorption unit (500) for driving particles captured on the dust collection electrode (310) to detach from the dust collection electrode (310).

8. The active recovery and redispersion device for tracer particles in PIV experiments according to claim 7, characterized in that, The desorption unit (500) is configured as a vibrating plate, a piezoelectric plate, or a pulse airflow generator.

9. A method for active recovery and redispersion of tracer particles for PIV experiments, comprising the active recovery and redispersion apparatus for PIV experiments as described in any one of claims 2-8, characterized in that, Includes the following steps: Receive recycling command: The control unit (700) generates a recycling mode switching command; Switch to recovery mode: suction is performed through the airflow outlet, and a collection voltage is applied to the electrostatic collection unit (300); Swirl and deflector pre-capture: The recovered gas enters the particle capture chamber (100) through the tangential inlet (110), forms a swirl in the swirl pre-separation zone (120), and then flows through the deflector channel; Electrostatic capture and end filtration: The pre-captured recovered gas enters the electrostatic capture unit (300), and the particles migrate toward the dust collection electrode (310) in the electric field formed by the dust collection electrode (310) and the counter electrode (320); then the recovered gas passes through the filtration unit (400), and the remaining particles in the recovered gas are intercepted by the filtration unit (400). Determine the recovery status: The control unit (700) determines whether the recovery process has reached the end condition based on the preset recovery time, the external residual particle status signal, or the experimental cabinet control command. Switch to redispersion mode: When the particles captured in the electrostatic collection unit (300) meet the preset reuse conditions and need to be returned, stop applying the collection voltage to the dust collection electrode (310); In-situ desorption and reflow: Backflush gas is introduced through the backflush gas inlet, and the backflush gas flows through the electrostatic capture unit (300) to carry the particles captured by the electrostatic capture unit (300) and discharge them from the redispersion outlet to the particle generator (10) or the storage unit.

10. The method for active recovery and redispersion of tracer particles for PIV experiments according to claim 9, characterized in that, In the step of determining the recovery status, the external residual particle status signal comes from the concentration monitoring unit (50) or the external image processing unit connected to the PIV camera (30); the experimental cabinet control command is a stop recovery command issued by the experimental cabinet control system (60) according to the experimental sequence, the start requirement of the next experimental stage, or manual operation. The control unit (700) determines the end of recycling based on any of the following conditions: the cumulative recycling time reaches the preset recycling duration, the effective detection cycle of the external residual particle state signal for a preset number of consecutive times meets the preset cleaning completion condition, or the control system (60) of the experimental cabinet receives a stop recycling command.

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