Particle fluidization system for two-dimensional high-spatial-resolution particle tracking velocity measurement

Abstract

The invention discloses a particle fluidization system for two-dimensional high-spatial-resolution particle tracking velocity measurement, and relates to the technical field of fluid mechanics. A tank body is of a vertically-arranged structure with the thick lower portion and the thin upper portion, the middle of the tank body is in a circular truncated cone shape, an annular air inlet pipe is fixedly arranged on the periphery of the lower portion of the circular truncated cone shape and communicated with the circular truncated cone shape through a plurality of vortex air inlet pipes, the vortex air inlet pipes are communicated with the tank body in the tangential direction, and a cleaning cover plate is detachably and fixedly connected to the lower end of the tank body. A particle flow outlet is formed in the upper end of the tank body and communicated with the inlet end of the particle spraying rod, and a particle filling port is formed in the upper end of the tank body and beside the particle flow outlet; the outlet end of the particle spray rod extends into the wind tunnel to be measured, and a plurality of hollow seams are formed in the periphery of the outlet section; the device has no large bending and complex structure, deposition and blockage of tracer particles are effectively avoided, the particle aggregation probability can be reduced through the hollowed-out seams, the measurement precision and the spatial resolution are improved, and the experiment reliability is enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of fluid mechanics, and in particular to a particle fluidization system for two-dimensional high spatial resolution particle tracking velocity measurement. Background Art

[0002] Two-dimensional high spatial resolution particle tracking velocimetry is based on particle tracking velocimetry (PTV) technology and particle image velocimetry (PIV) technology. PIV / PTV technology evolved from the laser speckle technology used to measure solid displacement in the 1960s and 1970s, and was developed and rapidly applied in the 1980s. Its advantage is that it can obtain the velocity distribution of the turbulent boundary layer with high precision and quantitatively through non-contact full-field measurement technology, and achieve high spatial resolution and accurate velocity vector analysis by using laser illumination and dual-camera alternating coupling technology. It provides quantitative velocity information of the entire flow field while realizing spatial flow visualization, providing detailed data support for fluid mechanics research. Two-dimensional high spatial resolution particle tracking velocimetry breaks through the limitations of single-point velocity measurement of laser Doppler velocimeter (LDV) technology, and also overcomes the interference of hot wires, probes, etc. on the flow field.

[0003] At present, although the two-dimensional high spatial resolution particle tracking velocimetry measurement system is a mature technology, there are still problems in the particle spreading process, such as solid particles often depositing, agglomerating, and clogging, which will affect the uniform distribution of particles and reduce the reliability of experimental results. Therefore, better control of particle spreading from all aspects is crucial for high-precision flow field analysis. Therefore, a particle fluidization system for two-dimensional high spatial resolution particle tracking velocimetry is urgently needed to solve this problem. Summary of the invention

[0004] The object of the present invention is to provide a particle fluidization system for two-dimensional high spatial resolution particle tracking velocity measurement to solve the problems of solid particle deposition, agglomeration and clogging.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a particle fluidization system for two-dimensional high spatial resolution particle tracking velocity measurement, comprising a tank body and a particle spray rod; the tank body is a vertically arranged structure with a coarse bottom and a fine top, the middle part of which is a truncated cone, an annular air inlet pipe is fixedly provided at the outer periphery of the lower part of the truncated cone, and is connected with the annular air inlet pipe through a plurality of vortex air inlet pipes, the vortex air inlet pipe is connected with the tank body along a tangential direction, the annular air inlet pipe is provided with a high-pressure air inlet port for connecting with an air source, a cleaning cover plate is detachably and fixedly connected to the lower end of the tank body, a particle flow outlet is provided at the upper end of the tank body for connecting with the inlet end of the particle spray rod, and a particle filling port is also provided at the upper end of the tank body next to the particle flow outlet for sealingly connecting with the outlet of a pneumatic valve of a nanoparticle delivery device; the outlet end of the particle spray rod extends into the wind tunnel to be tested, and a plurality of hollow slits are provided at the outer periphery of its outlet section.

[0006] Preferably, a wind tunnel sealing connector is fixedly provided on the outer periphery of the particle spray rod for fixedly connecting with the wind tunnel seal, and a tank body sealing connector and a sealing nut are provided at the inlet end of the particle spray rod. A groove is provided at one end of the wind tunnel sealing connector close to the inlet end of the particle spray rod, and the outer wall of the groove is cylindrical and provided with a thread matching the sealing nut. The shape and size of one end of the tank body sealing connector match the inside of the groove, and the sealing nut presses and fixes the tank body sealing connector and the wind tunnel sealing connector, and the tank body sealing connector is connected to the tank body through a pipeline.

[0007] Preferably, the annular air inlet pipe is coaxial with the truncated cone in the middle of the tank body, and multiple vortex air inlet pipes are distributed in a circular array along the axis of the annular air inlet pipe. The vortex air inlet pipe is straight and coplanar with the annular air inlet pipe; the high-pressure air inlet of the annular air inlet pipe is opened at the upper end away from the vortex air inlet pipe.

[0008] Preferably, the truncated cone in the middle of the tank body is a cylinder with a cleaning port at the bottom for cleaning particles settled to the bottom. The cleaning cover is sealed and connected to the bottom of the cylinder by a plurality of locking screws to block the cleaning port.

[0009] Preferably, the particle spray rod is made of 304 stainless steel.

[0010] Preferably, the tank body and the particle spraying rod are connected via a guide pipe, and the radius of curvature of each part of the guide pipe is greater than 50 mm.

[0011] Preferably, a roller is movable at the bottom of the gas source, which includes an air compressor and a high-pressure gas tank, and the gas source is arranged adjacent to the tank body.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] 1. The particle fluidization system used for two-dimensional high spatial resolution particle tracking velocimetry adopts an innovatively designed simple structure tank and hollow slit nozzle. The overall system has no large bends and complex structures, which effectively avoids the deposition and blockage of tracer particles, ensures the uniform distribution of particles, significantly improves the efficiency of particle fluidization and injection, improves the spatial stability of the measurement system, improves the measurement accuracy and spatial resolution, and enhances the reliability of the experiment. Indirectly, due to the improvement of measurement accuracy, the demand for subsequent processing and adjustment is reduced accordingly, reducing rework costs and material waste.

[0014] 2. The particle fluidization system used for two-dimensional high spatial resolution particle tracking velocimetry adopts a movable gas source, which not only optimizes the construction difficulty and gas source pressure loss problems caused by the long pipeline, solves the problem of insufficient power to drive the particles, but also overcomes the disadvantages of the particle fluidizer being fixed in position and unable to be flexibly moved.

[0015] 3. The particle fluidization system used for two-dimensional high spatial resolution particle tracking velocity measurement has a simple and reasonable structure, is easy to use, reduces labor and material costs, optimizes the test process, and significantly improves production efficiency and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a left-side structural schematic diagram of the tank body of the present invention;

[0017] Figure 2 It is a bottom view structural schematic diagram of the tank body of the present invention;

[0018] Figure 3 It is a schematic diagram of the top view of the tank body of the present invention;

[0019] Figure 4 It is a schematic diagram of the internal structure of the particle spray rod of the present invention;

[0020] Figure 5 It is a schematic diagram of the three-dimensional structure of the particle spray rod of the present invention.

[0021] In the figure: 10, tank body; 11, annular air inlet pipe; 12, vortex air inlet pipe; 13, cleaning cover; 14, particle filling port; 20, particle spray rod; 21, hollow seam; 22, wind tunnel sealing connector; 23, sealing nut; 24, tank body sealing connector. DETAILED DESCRIPTION

[0022] In order to effectively inject particles into hypersonic airflow, the key is to ensure that the particle flow maintains high momentum during the transport process. Based on this, Figures 1 to 5As shown, the present invention provides a particle fluidization system for two-dimensional high spatial resolution particle tracking velocity measurement, including a tank body 10 and a particle spray rod 20; the tank body 10 is a vertically arranged structure with a coarse bottom and a fine top, the middle part of which is a truncated cone, an annular air inlet pipe 11 is fixedly provided at the outer periphery of the lower part of the truncated cone, and is connected with the annular air inlet pipe 11 through a plurality of vortex air inlet pipes 12, the vortex air inlet pipe 12 is tangentially connected to the tank body 10, the annular air inlet pipe 11 is provided with a high-pressure air inlet for connecting to an air source, and high-pressure gas enters the tank body tangentially from two inlets of the annular air inlet pipe to form a vortex airflow, the high-pressure vortex efficiently drives the solid particles to fluidize and screens smaller particles to be sent into the hole, and at the same time, larger particles generated by the agglomeration effect are settled to the bottom, thereby optimizing the particle followability;

[0023] The lower end of the tank body 10 is detachably fixedly connected with a cleaning cover plate 13, and the upper end of the tank body 10 is provided with a particle flow outlet for communicating with the inlet end of the particle spray rod 20. For reference, the tank body 10 and the particle spray rod 20 can be connected by a guide pipe, so that the particle spray rod 20 can be extended from the top opening of the wind tunnel module. At this time, the guide pipe should be designed with a large inner diameter and high pressure resistance, and the radius of curvature of each bend is greater than 50mm to prevent particle clogging and agglomeration; the upper end of the tank body 10 is located next to the particle flow outlet and is also provided with a particle filling port 14 for sealing connection with the outlet of the pneumatic valve of the nanoparticle delivery device. The particle filling port 14 can be installed with a high-pressure plug when not in use, and can be conveniently connected with the outlet of the pneumatic valve of the nanoparticle delivery device when in use;

[0024] The outlet end of the particle spray rod 20 extends into the wind tunnel to be tested, and a number of hollow slits 21 are opened on the outer periphery of the outlet section to facilitate the uniform dispersion of particles in the wind tunnel. According to tests, the hollow slits 21 can greatly reduce the probability of particles agglomerating again; in addition, the particle spray rod 20 is preferably made of 304 stainless steel to prevent the spray rod from rusting and falling off, causing damage to the wind tunnel and interfering with the experimental results.

[0025] See also Figure 4 and Figure 5 In a preferred embodiment, a wind tunnel sealing connector 22 is fixedly provided on the periphery of the particle spray rod 20 for fixedly sealingly connecting with the wind tunnel. A tank body sealing connector 24 and a sealing nut 23 are provided at the inlet end of the particle spray rod 20. A groove is provided at one end of the wind tunnel sealing connector 22 close to the inlet end of the particle spray rod 20. The outer wall of the groove is cylindrical and has a thread matching the sealing nut 23. The shape and size of one end of the tank body sealing connector 24 match the inside of the groove. The sealing nut 23 presses and fixes the tank body sealing connector 24 with the wind tunnel sealing connector 22. The tank body sealing connector 24 is connected to the tank body 10 through a pipeline. The particle spray rod 20 can also adopt other connection methods as long as the fixing and sealing requirements are met.

[0026] Optional, such as Figures 1 to 3As shown, the annular air inlet pipe 11 is coaxial with the truncated cone in the middle of the tank body 10, and multiple vortex air inlet pipes 12 (for example, two) are distributed in a circular array along the axis of the annular air inlet pipe 11. The vortex air inlet pipe 12 is straight and coplanar with the annular air inlet pipe 11; the high-pressure air inlet port of the annular air inlet pipe 11 is opened at the upper end away from the vortex air inlet pipe 12.

[0027] The truncated cone-shaped portion in the middle of the tank body 10 may preferably be set as a cylinder, and a cleaning port is provided at the bottom thereof for timely cleaning the settled agglomerated particles out of the tank body 10, see Figure 2 The cleaning cover 13 is sealed and connected to the bottom of the cylinder by a plurality of locking screws to block the cleaning port when cleaning is not required; of course, other shapes may also be used below the truncated cone in the middle of the tank body 10, such as an inverted truncated cone funnel shape, or a curved surface with a diameter that gradually increases or decreases from top to bottom. The shape has little effect on the performance of the device, but it is best designed as the above-mentioned simple cylinder to reduce changes. The same is true for the part above the truncated cone. It is best to be a simple cylinder. If a guide tube is used for connection, the diameter is appropriately reduced at the upper end to guide the fluid to adapt to the guide tube.

[0028] The particle fluidization system of the present invention has a simple structure, and avoids the formation of a local low-speed zone due to excessively large design bends or a complex structure, thereby causing solid particle deposition and blockage.

[0029] In addition, traditional particle spreading devices at home and abroad usually use a high-pressure air source connected to a wind tunnel as a power source for driving particles. However, after a large number of experiments, we found that an overly long pipeline will cause a loss of air source pressure, resulting in insufficient power to drive the particles, and the construction of a long pipeline is difficult, and the particle fluidizer is fixed in position and cannot be moved flexibly. Therefore, the particle fluidization system of the present invention can further adopt a movable high-pressure air source. For reference, a roller can be provided at the bottom of the air source. The air source includes an air compressor and a high-pressure gas tank. The air source is arranged adjacent to the tank body 10. This can make the design of the pipeline shorter and the construction difficulty lower. At the same time, the particle fluidizer is not restricted by the air source and can be flexibly moved according to the experimental requirements, which is more convenient.

[0030] In a specific embodiment, the gas source weighs about 45Kg, and the maximum exhaust pressure can reach 30MPa. The high-pressure gas tank is equipped with two pressure gauges and a pressure reducing valve. The pressure in and out of the high-pressure gas tank is controlled by the pressure reducing valve to keep the gas source pressure at 30Mpa and the outlet pressure at 10Mpa. At this time, the pressure of the tank body 10 is 10Mpa, and the tank body 10 is connected to the gas source by a high-pressure stainless steel pipeline.

[0031] To ensure safety and stability, protective wire mesh can be arranged around the high-pressure gas tank and the tank body 10 for protection; all high-pressure equipment, valves, and pipelines should be subjected to water pressure testing to ensure good airtightness.

[0032] The particle fluidization system of the present invention is mainly used for two-dimensional high spatial resolution particle tracking velocimetry. The technical route of its measurement system is divided into four links: experimental preparation (i.e. spatial calibration), particle spreading (including high pressure gas source and particle generation), lighting shooting (including laser and camera) and post-processing (i.e. calculation program). In order to solve the large-scale and small-scale structures in the flow, the flow field data requires a high spatial resolution; and in order to make a meaningful comparison with the numerical simulation results, the density of the experimental data also needs to be high enough, so the number of tracer particles in the unit query area must reach a certain level. To this end, a particle spreading device with sufficient power is required to ensure that a high concentration of tracer particles can be maintained in the measurement volume during high-speed flow. Since the flow velocity is obtained indirectly by measuring the velocity of the tracer particles in the fluid, the tracer particles must faithfully follow the flow of the fluid. This requires the use of very small tracer particles. However, small tracer particles reflect less light, which leads to the third important condition in the research process of this project: a powerful pulsed laser is required to illuminate the flow field. Based on the above three conditions, the specific measurement system includes (1) a laser-image acquisition system, including a pulsed laser system and an imaging system, which is installed near the test chamber; (2) a particle generation and spreading device, including an air source, the particle fluidization system of the present invention and an automatic valve, which is located upstream of the test section; and (3) a measurement and control system, including a computer workstation and a timing controller, which is located near the test chamber or in the control room.

[0033] The key steps of the measurement are as follows: First, the particle fluidization system uses an air source to propel the tracer particles evenly into the flow field to be measured to ensure that the particles are fully dispersed; then, the laser-image acquisition system irradiates the laser light sheet emitted by the laser onto the tracer particles in the incoming flow under the guidance of a light guide device, stimulating the scattered light of the tracer particles, so that the particles form clear light spots in the high-speed flow, and then the imaging system (i.e., double-exposure camera) will capture these images; the collected data will be transmitted to the computer workstation in the measurement and control system, and the calculation program will analyze the image. Through two pictures taken at different times, the speed of the fluid movement is obtained from the change in the particle movement position, and the calculation results are displayed in a visual form.

[0034] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined by the claims.

[0035] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A particle fluidization system for two-dimensional high spatial resolution particle tracking velocity measurement, characterized in that: The invention comprises a tank body (10) and a particle spraying rod (20); the tank body (10) is a vertically arranged structure with a thick lower part and a thin upper part, wherein the middle part is in the shape of a truncated cone, an annular air inlet pipe (11) is fixedly arranged at the outer periphery of the lower part of the truncated cone, and is connected to the annular air inlet pipe (11) through a plurality of vortex air inlet pipes (12), the vortex air inlet pipes (12) are connected to the tank body (10) in a tangential direction, the annular air inlet pipe (11) is provided with a high-pressure air inlet for connecting to an air source, a cleaning cover plate (13) is detachably and fixedly connected to the lower end of the tank body (10), a particle flow outlet is provided at the upper end of the tank body (10) for connecting to the inlet end of the particle spraying rod (20), and a particle filling port (14) is also provided at the upper end of the tank body (10) next to the particle flow outlet for sealingly connecting to the outlet of a pneumatic valve of a nanoparticle delivery device; the outlet end of the particle spraying rod (20) extends into a wind tunnel to be tested, and a plurality of hollow slits (21) are provided at the outer periphery of the outlet section thereof.

2. A particle fluidization system for two-dimensional high spatial resolution particle tracking velocimetry according to claim 1, characterized in that: The outer periphery of the particle spray rod (20) is fixedly provided with a wind tunnel sealing connector (22) for sealing and fixed connection with the wind tunnel. The inlet end of the particle spray rod (20) is provided with a tank body sealing connector (24) and a sealing nut (23). A groove is provided at one end of the wind tunnel sealing connector (22) close to the inlet end of the particle spray rod (20). The outer wall of the groove is cylindrical and provided with a thread matching the sealing nut (23). The shape and size of one end of the tank body sealing connector (24) match the inside of the groove. The sealing nut (23) presses and fixes the tank body sealing connector (24) and the wind tunnel sealing connector (22). The tank body sealing connector (24) is connected to the tank body (10) through a pipeline.

3. A particle fluidization system for two-dimensional high spatial resolution particle tracking velocimetry according to claim 1, characterized in that: The annular air inlet pipe (11) is coaxial with the truncated cone in the middle of the tank body (10); a plurality of vortex air inlet pipes (12) are distributed in an annular array along the axis of the annular air inlet pipe (11); the vortex air inlet pipes (12) are straight and coplanar with the annular air inlet pipe (11); and a high-pressure air inlet port of the annular air inlet pipe (11) is opened at the upper end away from the vortex air inlet pipe (12).

4. A particle fluidization system for two-dimensional high spatial resolution particle tracking velocimetry according to claim 1, characterized in that: Below the truncated cone in the middle of the tank body (10) is a cylinder, the bottom of which is provided with a cleaning opening for cleaning particles settled to the bottom, and a cleaning cover plate (13) is sealedly connected to the bottom of the cylinder by a plurality of locking screws for blocking the cleaning opening.

5. The particle fluidization system for two-dimensional high spatial resolution particle tracking velocimetry according to claim 1, characterized in that: The particle spray rod (20) is made of 304 stainless steel.

6. A particle fluidization system for two-dimensional high spatial resolution particle tracking velocimetry according to claim 1, characterized in that: The tank body (10) and the particle spraying rod (20) are connected via a guide pipe, and the curvature radius of each part of the guide pipe is greater than 50 mm.

7. The particle fluidization system for two-dimensional high spatial resolution particle tracking velocimetry according to claim 1, characterized in that: The bottom of the gas source is provided with a movable roller, which includes an air compressor and a high-pressure gas tank, and the gas source is arranged adjacent to the tank body (10).

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