Particle spreading device, system and particle spreading method

Abstract

The present invention discloses a particle spreading device, a system and a particle spreading method. The particle spreading device includes a box and a particle spreading unit. A particle inlet is provided at the bottom of the box, and the particle inlet is configured to introduce a tracer particle flow into the box. A first particle outlet is provided at the top of the box, and the first particle outlet is configured to allow the tracer particle flow in the box to flow out and then enter the particle spreading unit; the particle spreading unit is connected to the box through the first particle outlet, and is configured to decelerate the tracer particle flow, wherein a second particle outlet is provided in the particle spreading unit, and the second particle outlet is configured to allow the tracer particles in the particle spreading unit to flow out and then flow to a test plate, wherein the direction of the second particle outlet is parallel to the test surface of the test plate.

Description

Technical Field

[0001] The present invention relates to the field of fluid measurement technology, and in particular to a particle spreading device, a system and a particle spreading method. Background Art

[0002] The boundary layer is a thin layer of fluid in the flow where the viscous force close to the surface cannot be ignored. It is also called the flow boundary layer or the boundary layer. The flow near the wall is related to the object's drag coefficient, aerodynamic friction, surface aerodynamic heating, heat transfer and other issues. It is very important to measure and study the flow conditions in the boundary layer.

[0003] With the development of laser and image processing technology, PIV flow display experiments on boundary layer flow fields can obtain flow field information in the near-wall area in a non-contact and intuitive manner. In PIV experiments, due to the lack of sufficient momentum and material exchange between the flow inside the boundary layer and the mainstream flow, the conventional mainstream area tracer particle seeding method is adopted: that is, tracer particles are directly seeded in the upstream flow area. This will cause the tracer particles to have difficulty in uniformly entering the near-wall area, making it impossible to conduct boundary layer PIV experiments. Summary of the invention

[0004] In view of this, the present invention provides a particle scattering device, a system and a particle scattering method to at least partially solve the above technical problems.

[0005] One aspect of an embodiment of the present invention provides a particle spreading device, including a box and a particle spreading unit.

[0006] A particle inlet is provided at the bottom of the box, and the particle inlet is configured to introduce a tracer particle flow into the box. A first particle outlet is provided at the top of the box, and the first particle outlet is configured to allow the tracer particle flow in the box to flow out and enter the particle spreading unit.

[0007] The particle scattering unit is connected to the box through a first particle outlet, and is configured to decelerate the tracer particle flow, wherein a second particle outlet is provided in the particle scattering unit, and the second particle outlet is configured to allow the tracer particles in the particle scattering unit to flow out and then flow to the test plate, wherein the direction of the second particle outlet is parallel to the test surface of the test plate.

[0008] According to an embodiment of the present invention, wherein:

[0009] The particle scattering unit includes a first scattering member, a second scattering member, and a third scattering member;

[0010] In the scattering unit, a first space is formed by a first scattering component, a second space is formed by a second scattering component, and a third space is formed by a third scattering component, wherein the first space is connected to the box through a first particle outlet, the first space is connected to the second space, the second space is connected to the third space, and the third space is connected to the outside through a second particle outlet.

[0011] According to an embodiment of the present invention, wherein:

[0012] A first spreading member, which is enclosed by a surrounding wall structure to form a first space, and a primary particle passage opening is provided in the surrounding wall of the first spreading member;

[0013] A second scattering member is enclosed outside the first scattering member by a surrounding wall structure, the outer wall of the first scattering member and the inner wall of the second scattering member form a second space, the second space is connected to the first space through a primary particle passing port, and a secondary particle passing port is provided in the surrounding wall of the second scattering member;

[0014] The third scattering member forms a third space through the surrounding wall structure and the second scattering member and the outer wall of the first scattering member. The third space and the second space are connected through the secondary particle passing port. The third scattering member is provided with a second particle outlet.

[0015] According to an embodiment of the present invention, wherein:

[0016] The second space includes two second sub-spaces, and the second spreading member includes two sets of surrounding wall structures, which are respectively enclosed on both sides of the first spreading member to form two second sub-spaces;

[0017] The third space includes two third sub-spaces. The inner wall of the third spreading member and the outer wall of the first spreading member are connected via a partition plate, so that the third space is divided into two third sub-spaces via the partition plate.

[0018] According to an embodiment of the present invention, wherein:

[0019] The third spreading member is a flat plate-like structure;

[0020] The top of the second dispersing member is a planar structure, and the secondary particle passage opening is arranged on the top wall surface of the second dispersing member;

[0021] A second particle outlet is formed between the third scattering component and the top of the second scattering component, and the ratio of the height of the second particle outlet to the width of the secondary particle passage opening is in the range of 2-5.

[0022] According to an embodiment of the present invention, wherein:

[0023] A rectifier plate is arranged in the box body, and a plurality of rectifier holes are arranged in the rectifier plate.

[0024] A second aspect of the present invention provides a particle spreading system, comprising:

[0025] A particle spreading device, comprising:

[0026] A box body, wherein a particle inlet is provided at the bottom of the box body, and the particle inlet is configured to introduce a tracer particle flow into the box body, and a first particle outlet is provided at the top of the box body, and the first particle outlet is configured to allow the tracer particle flow in the box body to flow out and enter the particle spreading unit;

[0027] A particle spreading unit is connected to the box through a first particle outlet and is configured to decelerate the tracer particle flow, wherein a second particle outlet is provided in the particle spreading unit, and the second particle outlet is configured to allow the tracer particles in the particle spreading unit to flow out and then flow toward the test plate, wherein the direction of the second particle outlet is parallel to the test surface of the test plate;

[0028] Liquid particle generator, comprising:

[0029] A liquid storage tank is configured to store a predetermined type of oily liquid, and an air inlet is provided on the top of the liquid storage tank;

[0030] The air intake purge probe adopts a hollow tubular structure and is configured to be vertically installed inside the liquid storage tank. The upper end opening of the air intake purge probe is connected to the air inlet, and the lower end of the air intake purge probe is provided with a plurality of probe holes;

[0031] An air outlet is arranged at the top of the liquid storage tank, and the air outlet is communicated with a particle inlet arranged in the box body;

[0032] Driving air source, including:

[0033] Air compressor;

[0034] The inlet of the gas transmission pipeline is connected with the outlet of the air compressor, and the outlet of the gas transmission pipeline is connected with the air inlet arranged on the top of the liquid storage tank.

[0035] According to an embodiment of the present invention, wherein:

[0036] A circle of secondary air purge holes is provided on the middle and upper pipe wall of the intake purge probe.

[0037] According to an embodiment of the present invention, wherein:

[0038] The tank body of the liquid storage tank is marked with the maximum liquid level line and the minimum liquid level line;

[0039] The position of the probe hole is lower than the lowest liquid level line, and the position of the secondary gas purge hole is higher than the highest liquid level line;

[0040] A liquid discharge port is provided at the bottom of the liquid storage tank.

[0041] A third aspect of the present invention provides a method for particle spreading using the above particle spreading system, comprising:

[0042] The predetermined gas of the preset pressure is delivered to the liquid storage tank of the liquid particle generator by an air compressor, so that the predetermined gas of the preset pressure passes through the air inlet purge probe provided in the liquid storage tank, inflates the oily liquid in the liquid storage tank and breaks the bubbles, and forms a tracer particle flow of the first preset speed at the gas outlet on the top of the liquid storage tank;

[0043] Passing a tracer particle flow of a first preset speed into a box of the particle spreading device through a particle inlet provided in the particle spreading device, so that the tracer particle flow flows out through a first particle outlet provided at the top of the box and then enters a particle spreading unit;

[0044] The tracer particle flow is decelerated by the particle spreading unit so that the tracer particle flow flows out from a second particle outlet provided in the particle spreading unit at a second preset speed and then flows toward the test plate, wherein the direction of the second particle outlet is parallel to the test surface of the test plate;

[0045] Among them, the first preset speed is 10-30 m / s, and the second preset speed is 0-2.0 m / s.

[0046] According to the embodiments of the present disclosure, by setting up a particle spreading unit to decelerate the tracer particle flow, the tracer particle flow can have a lower flow velocity before entering the boundary layer, so that it can smoothly enter the boundary layer without interfering with the flow in the boundary layer, thereby ensuring the effective conduct of the test and improving the test measurement accuracy. By configuring two third subspaces and two particle second outlets for the particle spreading unit, the requirements of conducting two flat plate boundary layer tests at the same time can be met, thereby improving the test convenience and test efficiency.

[0047] According to the embodiments of the present disclosure, by using the particle spreading device of the embodiments of the present invention to spread particles, a clear velocity field structure diagram can be obtained, which solves the problem that the existing PIV tracer particle spreading method cannot allow the PIV tracer particles to enter the boundary layer or the inside of the supercavitation. Not only can the tracer particles be evenly spread into the large-size wall boundary layer, but the disturbance to the mainstream and the boundary layer can also be minimized, providing good technical support for conducting research on the vortex mechanism inside the boundary layer such as boundary layer transition and boundary layer separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a schematic structural diagram of a particle spreading device according to an embodiment of the present invention;

[0049] Figure 2 is a schematic structural diagram of a tracer particle spreading system according to an embodiment of the present invention;

[0050] Figure 3 is a schematic diagram of the system structure of a driving gas source according to an embodiment of the present invention;

[0051] Figure 4 is a schematic structural diagram of a liquid particle generator according to an embodiment of the present invention;

[0052] Figure 5 Schematic diagram of the flow direction of tracer particles in a particle spreading device according to an embodiment of the present invention.

[0053] Description of reference numerals:

[0054] 1. Driving gas source;

[0055] 11. Air compressor;

[0056] 12. Ball valve;

[0057] 13. Pressure reducing valve;

[0058] 14. Needle valve;

[0059] 2. Liquid particle generator;

[0060] 21. Air inlet;

[0061] 22. Intake purge probe;

[0062] 221, probe hole;

[0063] 222, secondary air purge hole;

[0064] 23. Liquid storage tank;

[0065] 231. Liquid level gauge;

[0066] 232. Mounting flange;

[0067] 233. Liquid discharge port;

[0068] 234. Plug the drain port;

[0069] 24. Liquid storage tank cover;

[0070] 25. Exhaust port;

[0071] 31. Particle import;

[0072] 32. Box body;

[0073] 33. Rectifier plate;

[0074] 34. Particle scattering unit;

[0075] 340, particle first exit;

[0076] 341, a first spreading member;

[0077] 3411, primary particles pass through the port;

[0078] 3412, secondary particles pass through the port;

[0079] 342, second spreading member;

[0080] 343, third spreading member;

[0081] 344, particle second exit;

[0082] 345. Partition plate. DETAILED DESCRIPTION

[0083] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0084] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0085] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0086] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0087] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0088] The boundary layer is a thin layer of fluid in the flow where the viscous force cannot be ignored close to the surface of the object. It is also called the flow boundary layer or the boundary layer. If a fluid with very low viscosity (such as water, air, etc.) contacts an object and moves relative to it at a large Reynolds number, the thin fluid layer close to the surface will reduce its velocity due to the viscous shear stress; the fluid close to the surface adheres to the surface, and its relative velocity to the surface is equal to zero; extending from the surface to the inside of the fluid, the velocity of each layer gradually increases until it is equal to the free flow velocity. This thin layer of fluid deceleration from the surface upward is called the boundary layer. From the surface outward, the velocity increases rapidly to the local free flow velocity. Since the boundary layer is very thin, the velocity gradient in the direction perpendicular to the surface in the boundary layer is very large. Even if the fluid viscosity is not large, such as air, water, etc., the viscous force is still relatively large. When the Reynolds number is less than a certain value, it is a laminar boundary layer. The airflow inside the boundary layer flows smoothly. When the mainstream velocity increases, the laminar boundary layer transitions to the turbulent boundary layer and reaches the turbulent boundary layer state. In nature and engineering, most of the flow on the surface of moving objects (such as aircraft, blades, etc.) is a turbulent boundary layer. Since turbulence is a vortex flow with random pulsation, the flow changes with space and time. Therefore, the internal structure of the turbulent boundary layer is much more complicated than that of the laminar boundary layer. In addition, there is also a flow separation phenomenon in the boundary layer: when the fluid flows over the curved surface, its velocity and pressure change. When the flow rate decreases, the pressure must increase. Since the fluid micro-groups in the boundary layer have momentum loss, if the downstream pressure increases (that is, there is an adverse pressure gradient), the momentum will decrease again until the fluid micro-groups can no longer move forward on the surface of the object and will separate from the surface. Due to the separation of the boundary layer, fluid reflux occurs at the separation point, which intensifies the collision friction between the fluids and between the fluids and the boundary, forming a flow energy loss, which is a situation that engineering designers need to avoid as much as possible. In short, the flow in the near-wall area is related to the object's drag coefficient, aerodynamic friction, surface aerodynamic heating, heat exchange and other issues. It is very important to measure and study the flow conditions in the boundary layer.

[0089] With the development of laser and image processing technology, PIV flow display experiments on boundary layer flow fields can obtain flow field information in the near-wall area in a non-contact and intuitive manner, greatly improving the convenience of the experiment. After taking the image and processing it, detailed information such as velocity vector, vorticity, turbulence structure, and root mean square velocity of the flow field can be obtained with high accuracy. In the PIV test, due to the lack of sufficient momentum and material exchange between the flow inside the boundary layer and the mainstream flow, the conventional mainstream area tracer particle seeding method is adopted: that is, directly seeding tracer particles in the upstream flow area will cause the tracer particles to be difficult to evenly enter the near-wall area, resulting in the inability to conduct boundary layer PIV tests.

[0090] For example, in the related art, the axis of the particle spreading slit outlet on the thin-walled cover of the tracer particle spreading device is set to form an angle of 15° with the cover surface. However, the tracer particle airflow coming out of the spreading port may cause some degree of interference to the flow in the boundary layer, resulting in a decrease in measurement accuracy.

[0091] For another example, in the related art, the tracer particle airflow is set to flow out only from a smaller injection hole at the top of the cavity. However, the coverage range and area of ​​the particle flow in this method are limited, and it is not suitable for large-scale boundary layer flow display tests such as flat plate boundary layers.

[0092] In view of this, the embodiments of the present invention aim to solve the above technical problems, so as to not only evenly spread the tracer particles into the large-scale wall boundary layer, but also minimize the disturbance to the mainstream and the boundary layer, which is particularly suitable for flat plate flow tests.

[0093] An embodiment of the present invention provides a particle spreading device, Figure 1 is a schematic diagram of the structure of a particle spreading device according to an embodiment of the present invention. Figure 1 A particle spreading device according to an embodiment of the present invention is described.

[0094] like Figure 1 As shown, the particle spreading device includes a box 32 and a particle spreading unit 34 .

[0095] The bottom of the box 32 is provided with a particle inlet 31, which is configured to introduce a tracer particle flow at a certain speed into the box 32. During use, the particle inlet 31 is connected to a liquid particle generator, which is used to generate a tracer particle flow. The top of the box 32 is provided with a first particle outlet 340, which is configured to allow the tracer particle flow in the box 32 to flow out and enter the particle spreading unit 34.

[0096] The particle scattering unit 34 is connected to the box 32 through the first particle outlet 340, and is configured to decelerate the tracer particle flow, wherein a second particle outlet 344 is provided in the particle scattering unit 34, and the second particle outlet 344 is configured to allow the tracer particles in the particle scattering unit 34 to flow out and then flow to the test plate, wherein the direction of the second particle outlet 344 is parallel to the test surface of the test plate.

[0097] According to an embodiment of the present invention, the test plate can be placed horizontally near the second particle outlet 344 of the particle spreading unit 34. At this time, the direction of the second particle outlet 344 is also horizontal. Since the particle flow direction is parallel to the test surface of the test plate, and the particle flow flows along the surface of the plate, the particle flow can enter the wall boundary layer of the test plate in a horizontal direction after flowing out. Compared with the traditional method of sowing particles from the mainstream area, the method of the embodiment of the present disclosure can make it easier for tracer particles to enter the near-wall area because there is no interference from the flow in the mainstream area. Compared with the method in the related art in which the axis of the particle sowing slit outlet is at a certain angle to the cover plate surface, the method of the embodiment of the present disclosure does not interfere with the flow in the boundary layer, and the test measurement results are more reliable.

[0098] According to an embodiment of the present invention, a liquid particle generator is used to generate a tracer particle flow at a certain speed. If it is directly spread, since the particle flow flowing out of the outlet of the liquid particle generator has a high initial velocity, it will cause a relatively strong interference to the flow in the boundary layer of the test plate, seriously affecting the test results. Therefore, the embodiment of the present disclosure decelerates the tracer particle flow by setting a particle spreading unit 34 to meet the test requirements. The particle spreading unit 34 may be provided with one or more deceleration spaces (or channels). After the tracer particle flow enters the particle spreading unit 34 from the first particle outlet 340 at the top of the box 32, the flow rate gradually decreases after each deceleration space, until it reaches the final flow rate required by the test and flows out from the second particle outlet 344.

[0099] According to the embodiments of the present disclosure, by setting up a particle scattering unit 34 to decelerate the tracer particle flow, the tracer particle flow can have a lower flow velocity before entering the boundary layer, which satisfies the premise that it can smoothly enter the boundary layer without interfering with the flow in the boundary layer, thereby ensuring the effective implementation of the test and improving the test measurement accuracy.

[0100] According to the embodiments of the present disclosure, by using the particle spreading device of the embodiments of the present invention to spread particles, a clear velocity field structure diagram can be obtained, which solves the problem that the existing PIV tracer particle spreading method cannot allow the PIV tracer particles to enter the boundary layer or the inside of the supercavitation. Not only can the tracer particles be evenly spread into the large-size wall boundary layer, but the disturbance to the mainstream and the boundary layer can also be minimized, providing good technical support for conducting research on the vortex mechanism inside the boundary layer such as boundary layer transition and boundary layer separation.

[0101] According to an embodiment of the present invention, further, the particle scattering unit 34 includes a first scattering member 341 , a second scattering member 342 and a third scattering member 343 .

[0102] In the scattering unit, a first space is formed by a first scattering member 341, a second space is formed by a second scattering member 342, and a third space is formed by a third scattering member 343, wherein the first space is connected to the box body 32 through a first particle outlet 340, the first space is connected to the second space, the second space is connected to the third space, and the third space is connected to the outside through a second particle outlet 344.

[0103] Specifically, Figure 1 As shown, the first scattering member 341 is surrounded by a wall structure to form a first space, and a primary particle passage opening 3411 is provided in the wall of the first scattering member 341; the second scattering member 342 is surrounded by a wall structure on the outside of the first scattering member 341, and a second space is formed between the outer wall of the first scattering member 341 and the inner wall of the second scattering member 342, the second space is connected to the first space through the primary particle passage opening 3411, and a secondary particle passage opening 3412 is provided in the wall of the second scattering member 342; the third scattering member 343 is formed by the wall structure and the outer walls of the second scattering member 342 and the first scattering member 341, the third space is connected to the second space through the secondary particle passage opening 3412, and a second particle outlet 344 is provided in the third scattering member 343.

[0104] According to an embodiment of the present invention, in the scattering unit, three-stage deceleration spaces (or channels) are formed by the above-mentioned three scattering components, and the tracer particle flow enters the first space from the particle first outlet 340 at the top of the box body 32, enters the second space through the first-stage particle passage 3411 after a first-stage deceleration in the first space, enters the third space through the second-stage particle passage 3412 after a second-stage deceleration in the second space, and flows out from the particle second outlet 344 after reaching the final flow rate required by the test after three-stage deceleration in the third space.

[0105] According to an embodiment of the present invention, further, the third spreading member 343 may be a flat plate structure. The top of the second spreading member 342 is a flat structure, and the secondary particle passage 3412 is disposed on the top wall of the second spreading member 342. Figure 1 As shown, the first scattering member 341 can be formed by a plurality of flat plates enclosing a first space of a cubic or rectangular structure, and a primary particle passage opening 3411 is provided in the side wall of the first scattering member 341. The second scattering member 342 can be formed by an inverted L-shaped plate enclosing the outside of the first scattering member 341, and a slit is formed between the inverted L-shaped plate and the side wall of the first scattering member 341, which is the secondary particle passage opening 3412. The third scattering member 343 is formed by a thin flat plate, and the thin flat plate is supported and fixed in parallel to the top of the first scattering member 341 through a vertical partition plate 345. A second particle outlet 344 is formed between the thin flat plate and the upper surface of the second scattering member 342.

[0106] According to an embodiment of the present invention, the ratio of the height of the second particle outlet 344 to the width of the secondary particle passage 3412 is in the range of 2 to 5. In this way, the outlet flow rate of the tracer particles can be ensured to be within the designed range.

[0107] According to an embodiment of the present invention, further, the second space includes two second sub-spaces, and the second spreading member 342 includes two sets of surrounding wall structures, which are respectively enclosed on both sides of the first spreading member 341 to form two second sub-spaces. The third space includes two third sub-spaces, and the inner wall of the third spreading member 343 and the outer wall of the first spreading member 341 are connected by a partition plate 345 (vertical standing plate), so that the third space is divided into two third sub-spaces by the partition plate 345.

[0108] like Figure 1 As shown, the second scattering member 342 is surrounded by two inverted L-shaped plates on the left and right sides of the first scattering member 341, and two second sub-spaces are formed on both sides of the second scattering member 342. The third scattering member 343 is connected to the upper surface of the first scattering member 341 through a partition plate (vertical plate), and the third space is divided into two left and right third sub-spaces. According to the scale of the flat plate boundary layer flow test, the height of the third scattering member 343 from the top of the second scattering member 342 is set to 5 to 30 mm.

[0109] According to an embodiment of the present invention, two particle second outlets 344 can be formed through the above structure, and the two particle second outlets 344 are respectively located on both sides of the box 32. In this way, two groups of comparative tests can be carried out at the same time. If the particle flows flowing out of the two particle second outlets 344 have exactly the same flow state, it is ensured that in the two groups of comparative tests, the initial state of the particle flow entering the boundary layer is consistent (speed, flow direction), thereby ensuring the accuracy of the test.

[0110] According to an embodiment of the present invention, further, Figure 1 As shown, a rectifying plate 33 is provided in the box 32, and a plurality of rectifying holes are provided in the rectifying plate 33. The rectifying plate 33 is installed in the middle of the box 32, and the box 32 is divided into two upper and lower cavities. The lower cavity plays a role of stabilizing the pressure, and the upper cavity plays a role of storing liquid tracer particles. In order to ensure that the particles have sufficient particle density when they finally flow into the flat plate, the particle flow entering through the particle inlet 31 needs to have a higher initial velocity. Therefore, the particle inlet 31 is set at the side wall of the box 32 below the rectifying plate 33. The particle flow entering the particle inlet 31 is rectified by the rectifying plate 33. On the one hand, the speed is reduced, and on the other hand, the flow velocity and distribution of the particle flow are more uniform, which ensures the requirements of subsequent experiments.

[0111] A second aspect of the present invention provides a particle spreading system comprising the above-mentioned particle spreading device, Figure 2 is a schematic diagram of the structure of the tracer particle spreading system according to an embodiment of the present invention. Figure 2 , a tracer particle spreading system according to an embodiment of the present invention is described.

[0112] like Figure 2 As shown, the tracer particle spreading system includes the particle spreading device as described above, and also includes a liquid particle generator 2 and a driving gas source 1.

[0113] Figure 3 is a schematic diagram of the system structure of the driving gas source 1 according to an embodiment of the present invention, such as Figure 3 As shown, the driving gas source 1 includes an air compressor 11 and a gas pipeline.

[0114] The inlet of the gas pipeline is connected to the outlet of the air compressor 11, and the outlet of the gas pipeline is connected to the air inlet 21 of the liquid particle generator 2. The gas pipeline is provided with a ball valve 12, a pressure reducing valve 13, and a needle valve 14. The pressure reducing valve 13 can control the gas pressure in the gas tank of the air compressor 11 to 0.1-0.3 MPa, and the needle valve 14 is used to adjust the air flow entering the liquid particle generator 2.

[0115] Figure 4 Schematic diagram of the structure of a liquid particle generator 2 according to an embodiment of the present invention.

[0116] like Figure 4As shown, the liquid particle generator 2 includes a liquid storage tank 23, an air inlet purge probe 22, a top cover of the liquid storage tank 23, and an air outlet 25, wherein the liquid storage tank 23 is configured to store a predetermined type of oily liquid, and an air inlet 21 is provided on the top of the liquid storage tank 23; the air inlet purge probe 22 adopts a hollow tubular structure and is configured to be vertically installed inside the liquid storage tank 23, the upper end opening of the air inlet purge probe 22 is connected to the air inlet 21, and the lower end of the air inlet purge probe 22 is provided with a plurality of probe holes 221 with an aperture of 0.5 to 1 mm for generating bubbles; the air outlet 25 is arranged at the top of the liquid storage tank 23, and the air outlet 25 is connected to the particle inlet 31 provided in the box body 32.

[0117] According to an embodiment of the present invention, a circle of secondary gas purge holes 222 with a diameter of 1 to 2 mm is provided on the middle and upper wall of the air inlet purge probe 22. The secondary gas is used to break up the oil bubbles to make the particle size uniform.

[0118] According to an embodiment of the present invention, the body of the liquid storage tank 23 is marked with a maximum liquid level line and a minimum liquid level line; the position of the probe hole 221 is lower than the minimum liquid level line, and the position of the secondary gas purge hole 222 is higher than the maximum liquid level line; a liquid level gauge 231 is also provided on the liquid storage tank 23 for measuring and calibrating the liquid level.

[0119] According to an embodiment of the present invention, the liquid storage tank 23 is also provided with a mounting flange 232, a liquid discharge port 233 and a liquid discharge port 233 plug, and the liquid storage tank 23 is sealed with the top cover of the liquid storage tank 23 through the mounting flange 232; an air intake purge probe 22 is fixed on the top cover of the liquid storage tank 23, one end of the air intake purge probe 22 is connected to the air inlet 21, and the other end is inserted below the liquid level at the bottom of the liquid storage tank 23, and the air outlet 25 is arranged on the top cover of the liquid storage tank 23.

[0120] According to an embodiment of the present invention, a probe hole 221 is provided at the lower end of the air intake purge probe 22, and an airflow of a certain pressure is introduced from the air inlet 21 of the liquid particle generator 2 and sprayed out through the probe hole 221 at the bottom of the air intake purge probe 22, so that the oily liquid is bubbled and the oily bubbles move upward, and a part of the bubbles burst at the liquid surface; further, the airflow blown out through the secondary air purge hole 222 interferes with the unbroken oily bubbles, and the oily bubbles burst under the shear force of the purge airflow from the secondary air purge hole 222, thereby forming a uniform particle flow and promoting the generation of particle flow.

[0121] A third aspect of the present invention provides a method for particle spreading using the above particle spreading system, comprising the following operations:

[0122] Operation S1: using the air compressor 11 to deliver a predetermined gas of a preset pressure to the liquid storage tank 23 of the liquid particle generator 2, so that the predetermined gas of the preset pressure passes through the air inlet purge probe 22 provided in the liquid storage tank 23, inflates the oily liquid in the liquid storage tank 23 and breaks the bubbles, and then forms a tracer particle flow of a first preset speed at the gas outlet 25;

[0123] Operation S2: passing the tracer particle flow of the first preset speed into the box 32 of the particle spreading device through the particle inlet 31 provided in the particle spreading device, so that the tracer particle flow flows out through the first particle outlet 340 provided at the top of the box 32 and then enters the particle spreading unit 34;

[0124] Operation S3: decelerating the tracer particle flow through the particle scattering unit 34, so that the tracer particle flow flows out along the second particle outlet 344 provided in the particle scattering unit 34 at a second preset speed and then flows toward the test plate, wherein the direction of the second particle outlet 344 is parallel to the test surface of the test plate.

[0125] Figure 5 Schematic diagram of the flow direction of tracer particles in a particle spreading device according to an embodiment of the present invention.

[0126] like Figure 5 As shown, in the flat plate test, the top wall of the second spreading member 342 is at the same height as the test flat plate.

[0127] The air compressor 11 generates an air flow with a certain pressure which enters from the air inlet 21 of the liquid particle generator 2, and is ejected through the purge holes at the bottom and side walls of the air inlet purge probe 22, generating oily bubbles that move upward. Some of the bubbles burst at the liquid surface interface, and the other part bursts under the shear force of the purge air flow from the secondary air purge hole 222, forming a uniform particle flow, which then flows out from the air outlet 25 on the top cover of the liquid storage tank 23 and enters the particle seeding device.

[0128] The tracer particle flow enters the first space formed by the first scattering component 341 from the first particle outlet 340 at the top of the box 32, enters the second space formed by the second scattering component 342 through the first particle outlet 3411 after a first-stage deceleration in the first space, enters the third space formed by the third scattering component 343 through the second particle outlet 3412 after a second-stage deceleration in the second space, is blocked by the thin plate in the third space, reaches the final flow rate required by the test after three-stage deceleration, flows slowly in the horizontal direction from the second particle outlet 344, and enters the flat plate boundary layer.

[0129] According to an embodiment of the present disclosure, in order to ensure that the particles have sufficient particle density (concentration) when they finally flow into the flat plate, the particle flow entering through the particle inlet 31 needs to have a higher initial velocity. Therefore, the first preset velocity of the tracer particle flow at the air outlet 25 of the liquid storage tank 23 is 10 to 30 m / s.

[0130] According to the embodiments of the present disclosure, in order to ensure that the particle flow that eventually enters the boundary layer can smoothly enter the boundary layer without interfering with the flow in the boundary layer, it is necessary to ensure that the tracer particle flow has a lower flow velocity before entering the boundary layer. Therefore, after the tracer particle flow is decelerated by the scattering unit, the tracer particle flow flowing out from the second particle outlet 344 of the scattering unit flows at a second preset velocity of 0 to 2.0 m / s. In this way, the effective conduct of the test can be guaranteed and the test measurement accuracy can be improved.

[0131] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A particle spreading device, comprising: A box, wherein a particle inlet is provided at the bottom of the box, and the particle inlet is configured to introduce a tracer particle flow into the box, and a first particle outlet is provided at the top of the box, and the first particle outlet is configured to allow the tracer particle flow in the box to flow out and enter a particle spreading unit; A particle spreading unit is connected to the box through the first particle outlet, and is configured to decelerate the tracer particle flow, wherein a second particle outlet is provided in the particle spreading unit, and the second particle outlet is configured to allow the tracer particles in the particle spreading unit to flow out and then flow to the test plate, wherein the direction of the second particle outlet is parallel to the test surface of the test plate.

2. The device according to claim 1, wherein: The particle scattering unit includes a first scattering member, a second scattering member and a third scattering member; In the scattering unit, a first space is formed by the first scattering member, a second space is formed by the second scattering member, and a third space is formed by the third scattering member, wherein the first space is connected to the box through the first particle outlet, the first space is connected to the second space, the second space is connected to the third space, and the third space is connected to the outside through the second particle outlet.

3. The device according to claim 2, wherein: The first scattering member is enclosed by a surrounding wall structure to form the first space, and a primary particle passage opening is provided in the surrounding wall of the first scattering member; The second scattering member is enclosed outside the first scattering member by a surrounding wall structure, the outer wall of the first scattering member and the inner wall of the second scattering member form a second space, the second space is connected to the first space through the primary particle passage, and the surrounding wall of the second scattering member is provided with a secondary particle passage; The third scattering member forms the third space through the surrounding wall structure and the outer walls of the second scattering member and the first scattering member. The third space and the second space are connected through the secondary particle passage port. The third scattering member is provided with the second particle outlet.

4. The device according to claim 3, wherein: The second space includes two second sub-spaces, and the second scattering member includes two sets of surrounding wall structures, which are respectively enclosed on two sides of the first scattering member to form two second sub-spaces; The third space includes two third sub-spaces, and the inner wall of the third spreading member and the outer wall of the first spreading member are connected via a partition plate, so that the third space is divided into the two third sub-spaces by the partition plate.

5. The device according to claim 3, wherein: The third spreading member is a flat plate structure; The top of the second dispersing member is a planar structure, and the secondary particle passage port is arranged on the top wall surface of the second dispersing member; The second particle outlet is formed between the third scattering member and the top of the second scattering member, and the ratio of the height of the second particle outlet to the width of the secondary particle passage opening is in the range of 2-5.

6. The device according to claim 1, wherein: A rectifying plate is arranged in the box body, and a plurality of rectifying holes are arranged in the rectifying plate.

7. A particle spreading system comprising: A particle spreading device, comprising: A box, wherein a particle inlet is provided at the bottom of the box, and the particle inlet is configured to introduce a tracer particle flow into the box, and a first particle outlet is provided at the top of the box, and the first particle outlet is configured to allow the tracer particle flow in the box to flow out and enter a particle spreading unit; a particle spreading unit, connected to the box through the first particle outlet, configured to decelerate the tracer particle flow, wherein the particle spreading unit is provided with a second particle outlet, and the second particle outlet is configured to allow the tracer particles in the particle spreading unit to flow out and then flow toward the test plate, wherein the direction of the second particle outlet is parallel to the test surface of the test plate; Liquid particle generator, comprising: A liquid storage tank, configured to store a predetermined type of oily liquid, wherein the top of the liquid storage tank is provided with an air inlet; An intake purge probe adopts a hollow tubular structure and is configured to be vertically installed inside the liquid storage tank, the upper end opening of the intake purge probe is connected to the air inlet, and the lower end of the intake purge probe is provided with a plurality of probe holes; An air outlet is arranged at the top of the liquid storage tank, and the air outlet is communicated with the particle inlet arranged in the box body; Driving air source, including: Air compressor; An air pipeline, wherein the inlet of the air pipeline is connected to the outlet of the air compressor, and the outlet of the air pipeline is connected to the air inlet arranged on the top of the liquid storage tank.

8. The system of claim 7, wherein: A circle of secondary air purge holes is arranged at the middle and upper tube wall of the air intake purge probe.

9. The system of claim 8, wherein: The tank body of the liquid storage tank is marked with a maximum liquid level line and a minimum liquid level line; The position of the probe hole is lower than the lowest liquid level line, and the position of the secondary gas purge hole is higher than the highest liquid level line; The bottom of the liquid storage tank is provided with a liquid discharge port.

10. A method for particle spreading using the particle spreading system according to any one of claims 7 to 9, comprising: The predetermined gas of the preset pressure is delivered to the liquid storage tank of the liquid particle generator by an air compressor, so that the predetermined gas of the preset pressure passes through the air inlet purge probe provided in the liquid storage tank, inflates the oily liquid in the liquid storage tank and ruptures the bubbles, and forms a tracer particle flow of the first preset speed at the gas outlet on the top of the liquid storage tank; Passing the tracer particle flow of the first preset speed into the box of the particle spreading device through the particle inlet provided in the particle spreading device, so that the tracer particle flow flows out through the first particle outlet provided at the top of the box and then enters the particle spreading unit; The tracer particle flow is decelerated by the particle spreading unit, so that the tracer particle flow flows out along a second particle outlet provided in the particle spreading unit at a second preset speed and then flows toward the test plate, wherein the direction of the second particle outlet is parallel to the test surface of the test plate; Wherein, the first preset speed is 10-30 m / s, and the second preset speed is 0-2.0 m / s.

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