Particle near-wall aerodynamic force coefficient measuring device and measuring method

Abstract

The application provides a granular near-wall aerodynamic force coefficient measuring device and a measuring method, which comprise an airflow pipeline, a granular injection assembly and an electric field generating assembly. The airflow pipeline is provided with a stable flow direction clean airflow, the granular injection assembly is used for injecting charged particles into the airflow pipeline, and the electric field generating assembly is used for forming a flow direction electric field and a vertical electric field in the airflow pipeline. The flow direction electric field is used for providing an electric field force in the opposite direction of the flow field for the charged particles in the airflow pipeline. The vertical electric field is used for providing an electric field force in the opposite direction of gravity for the charged particles in the airflow pipeline. By controlling the electric field intensity of the flow direction electric field and the vertical electric field, the charged particles can be kept static in the main flow area and the near-wall area, respectively, and the aerodynamic force coefficient of the charged particles in the near-wall area is calculated based on the size of the charged particles and the position of the charged particles in the near-wall area. The application can measure the force characteristics and force rules of the charged particles at different wall positions.

Description

Technical Field

[0001] The present application relates to the field of nuclear power engineering technology, and in particular to a device and method for measuring the aerodynamic coefficient of particles near the wall based on electric field action. Background Art

[0002] In the energy sector, compact heat exchangers such as printed circuit boards (PCBs) have broad application prospects due to their high heat transfer efficiency and compact structure. For example, in the advanced nuclear power sector, PCB heat exchangers have significant potential for application in small modular reactors. However, due to their millimeter-scale flow channels, dust particles carried in the fluid easily deposit on the heat exchanger surface, affecting the thermal resistance. In severe cases, they may even clog the microchannels, thus affecting the heat exchanger's performance. Because dust particles are driven by the coolant airflow, measuring the characteristics of the airflow acting on particles near the wall is crucial.

[0003] Existing research indicates that near-wall airflow forms shear flows with significant velocity gradients. The properties of shear flows on particles differ significantly from those of conventional uniform flows. They not only increase the drag coefficient on the particles but also generate a significant normal lift coefficient component. Furthermore, the force characteristics of particles vary at different wall distances. However, conventional methods for measuring the force exerted by airflow on particles rely primarily on mechanical balance, relying on gravity balance to measure the force exerted on particles in the airflow. However, these methods are unable to quantitatively measure the force patterns on particles at different wall distances. Summary of the Invention

[0004] The present application aims to solve one of the technical problems in the related art at least to a certain extent.

[0005] To this end, the purpose of this application is to propose a device and method for measuring the aerodynamic coefficient of particles near the wall based on the action of an electric field. It can measure the force characteristics and acceptance laws of charged particles at different wall positions through the combined action of particle charging, external electric field and gravity, and combined with fluid mechanics theory, to provide a theoretical basis for studying the movement and deposition of particles in narrow channels.

[0006] To achieve the above-mentioned objectives, the first embodiment of the present application provides a device for measuring the aerodynamic coefficient of a particle near the wall, comprising:

[0007] An airflow duct comprises an inlet end and an outlet end opposite to each other, and a particle injection end arranged between the inlet end and the outlet end; a clean airflow is provided in the airflow duct so as to stably flow along the extension direction of the duct;

[0008] a particle injection assembly connected to the particle injection end and used for injecting charged particles into the air flow duct;

[0009] an electric field generating assembly, comprising a first electrode and a second electrode arranged along the extending direction of the pipeline, and a third electrode and a fourth electrode arranged perpendicular to the extending direction of the pipeline;

[0010] In which, the first electrode and the second electrode form a flow electric field in the airflow duct, and the flow electric field is used to provide the charged particles injected into the airflow duct with an electric field force in the opposite direction of the clean airflow; the third electrode and the fourth electrode form a vertical electric field in the airflow duct, and the vertical electric field is used to provide the charged particles injected into the airflow duct with an electric field force in the opposite direction of gravity.

[0011] Optionally, the particle injection assembly includes a first conduit, and a gas cylinder, an aerosol generator and a rotary impact launcher connected to the first conduit; wherein the aerosol generator is used to inject aerosol particles into the first conduit; the gas cylinder is used to provide a driving force for the directional movement of the aerosol particles in the first conduit and the rotary impact launcher; the rotary impact launcher is used to convert the aerosol particles into the charged particles and inject them into the airflow duct.

[0012] Optionally, the rotary impact launcher includes an inverted conical cylinder, a barrel cover located on the top of the cylinder, a rotating shaft located at the center of the cylinder and vertically passing through the barrel cover along the axial direction, and a plurality of friction plates located inside the cylinder and coaxial with the rotating shaft, and the plurality of friction plates are arranged in sequence along the axial direction of the cylinder; the first conduit is connected to the input end of the rotary impact launcher, and the input end is arranged on the side of the cylinder close to the barrel cover; the particle injection end is connected to the output end of the rotary impact launcher, and the output end is arranged on the side of the cylinder away from the barrel cover.

[0013] Optionally, the plurality of friction plates include a plurality of rotating orifice plates and annular baffles sequentially spaced along the axial direction of the cylinder; wherein,

[0014] The outer edge of the annular baffle is fixed in contact with the inner wall of the cylinder, and the inner edge of the annular baffle maintains a gap with the rotating shaft; the center of the rotating orifice plate is fixed to the rotating shaft, and the edge of the rotating orifice plate maintains a gap with the inner wall of the cylinder, and each of the rotating orifice plates is provided with a plurality of through holes.

[0015] Optionally, the measuring device further includes an induced draft fan, a filter and a cold dryer; wherein the filter and the cold dryer are sequentially arranged on one side of the air flow duct close to the inlet end, and the induced draft fan is arranged on one side of the air flow duct close to the outlet end.

[0016] Optionally, the measuring device further includes a particle detection component, and the airflow duct is further provided with a transparent window, and the particle detection component detects size parameters and position parameters of the charged particles in the airflow duct through the transparent window.

[0017] To achieve the above-mentioned purpose, the second embodiment of the present application proposes a method for measuring the aerodynamic coefficient of a particle near the wall, including using any of the measurement devices described above, and the measurement method includes the steps of:

[0018] Forming a clean airflow with a stable flow direction in the air duct;

[0019] forming charged particles in a particle injection assembly and injecting the charged particles into the air flow duct;

[0020] forming a flow-direction electric field and a vertical electric field in the airflow duct, and controlling the electric field intensities of the flow-direction electric field and the vertical electric field respectively, so that the charged particles reach a first equilibrium state in a first predetermined region of the airflow duct;

[0021] Adaptively adjusting the electric field strength of the vertical electric field so that the charged particles in the first equilibrium state reach a second equilibrium state in a second preset area of ​​the airflow duct under the action of the electric field force of the vertical electric field;

[0022] Based on the position parameters of the charged particles in the second preset area and the mechanical equilibrium equivalence relationship between the gravity, aerodynamic force and electric field force of the charged particles in the first equilibrium state and the second equilibrium state, the expression of the aerodynamic force coefficient near the wall is obtained.

[0023] Optionally, the aerodynamic force coefficient of the charged particle in the second equilibrium state satisfies:

[0024]

[0025] Among them, C L is the lift coefficient of the vertical component of the aerodynamic force; C D is the drag coefficient of the streamwise component of the aerodynamic force; ρ p is the density of the charged particles; V p is the volume of the charged particle; A p is the vertical projection area of ​​the charged particle; y is the vertical distance between the charged particle and the inner wall of the air flow duct in the second equilibrium state; g is the gravity constant; E f1 is the electric field intensity of the vertical electric field in the first equilibrium state; E f2 is the electric field strength of the vertical electric field in the second equilibrium state; ρ f is the density of the clean airflow;f is the flow rate of the clean air flow in the first preset area; D is the Darcy friction coefficient; u f is the viscosity coefficient of the clean air flow.

[0026] Optionally, before the adaptive adjustment of the electric field strength of the vertical electric field, the method further includes tracking and locating the charged particles that have reached the first equilibrium state in the first preset area and acquiring size parameters thereof using a particle detection component.

[0027] Optionally, after the step of adaptively adjusting the electric field strength of the vertical electric field, the step also includes using the particle detection component to confirm whether the charged particles in the first equilibrium state move to the second preset area under the action of the electric field force of the vertical electric field, and obtaining the position relationship parameters between the charged particles that reach the second equilibrium state in the second preset area and the inner wall of the airflow duct.

[0028] The device and method for measuring the aerodynamic coefficient of particles near the wall provided by the present application have at least the following beneficial effects:

[0029] The present application provides a device and method for measuring the aerodynamic coefficient of particles near a wall, comprising an airflow duct, a particle injection assembly, and an electric field generating assembly. A clean airflow with a stable flow direction is provided within the airflow duct, the particle injection assembly is used to inject charged particles into the airflow duct, and the electric field generating assembly is used to form a streamwise electric field and a vertical electric field within the airflow duct. The streamwise electric field is used to provide an electric field force in the opposite direction of the flow field to the charged particles within the airflow duct; the vertical electric field is used to provide an electric field force in the opposite direction of gravity to the charged particles within the airflow duct. By controlling the electric field strength of the streamwise electric field and the vertical electric field, the charged particles can be kept stationary in the mainstream area and the near-wall area, respectively. Based on the size of the charged particles and their position in the near-wall area, the aerodynamic coefficient of the charged particles in the near-wall area is calculated. The present application can measure the force characteristics and force patterns of charged particles at different wall locations, thereby improving the measurement accuracy and efficiency of the aerodynamic coefficient of charged particles in the near-wall area.

[0030] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0032] Figure 1 Schematic diagram of the structure of a particle aerodynamic coefficient measuring device according to an embodiment of the present application.

[0033] Figure 2 Schematic diagram of the structure of a rotating impact launcher according to an embodiment of the present application.

[0034] Figure 3 The figure is a flow chart of a method for measuring aerodynamic coefficient of particles according to an embodiment of the present application.

[0035] 1. Gas cylinder; 2. Regulating valve; 3. Flowmeter; 4. Aerosol generator; 5. Rotating impactor emitter; 6. Filter; 7. Cold dryer; 8. First electrode; 9. Lens; 10. Laser; 11. Hot wire anemometer; 12. Third electrode; 13. Fourth electrode; 14. Second electrode; 15. Top-view CCD camera; 16. Side-view CCD camera; 17. Induced draft fan; 18. Airflow duct; 19. Transparent window; 50. Barrel cover; 51. Cavity inlet, 52. Rotating shaft; 53. Rotating orifice plate; 54. Annular baffle; 55. Barrel body; 56. Cavity outlet. DETAILED DESCRIPTION

[0036] The following describes in detail embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0037] According to a first aspect of the embodiment of the present application, a device for measuring the aerodynamic coefficient of a particle near the wall is provided, such as Figure 1 As shown, the device includes an air flow conduit 18, a particle injection assembly and an electric field generating assembly.

[0038] Airflow duct 18 is an insulated tube comprising an inlet and an outlet, and a particle injection port disposed between the inlet and outlet ends. Airflow duct 18 is configured to generate a stable clean airflow along the duct's extension direction between the inlet and outlet ends. The duct's extension direction may be referred to herein as the flow direction. The direction perpendicular to the duct's extension direction may be referred to herein as the vertical direction.

[0039] In some embodiments, an induced draft fan 17 is provided at the outlet end of the airflow duct 18, and a filter 6 and a cold dryer 7 are provided at the inlet end of the airflow duct 18. Thus, turning on the induced draft fan 17 introduces ambient air into the inlet end of the airflow duct 18. After the air is filtered by the filter 6 and dried by the cold dryer 7, a clean airflow with a stable flow direction is formed in the airflow duct 18.

[0040] The particle injection assembly is used to form charged particles. It is connected to the particle injection end of the airflow duct 18 to inject the charged particles into the airflow duct 18 from the particle injection end. The particle injection end is located on the side of the airflow duct 18 near the inlet end, so that after entering the airflow duct 18, the charged particles can move toward the outlet end under the aerodynamic force of the clean airflow flowing steadily in the airflow duct 18.

[0041] In some embodiments, the particle injection assembly includes a first conduit, and a gas cylinder 1 , an aerosol generator 4 , and a rotary impactor emitter 5 connected to the first conduit.

[0042] As an example, the inlet of gas cylinder 1 is connected to the inlet of the first conduit. Thus, whenever gas cylinder 1 and the on-off valve are opened, the high-pressure gas filled in gas cylinder 1 will instantly pass through the first conduit and the rotary impactor 5, then enter the airflow conduit 18 and flow out of the outlet of the airflow conduit 18. In other words, the function of gas cylinder 1 is to provide the driving force for the subsequent aerosol particles to move from the first conduit into the rotary impactor 5 and the airflow conduit 18 in sequence.

[0043] In order to facilitate the monitoring and control of the flow rate of the airflow in the first conduit, a regulating valve 2 and a flow meter 3 can also be set on the first conduit. The regulating valve 2 can be used to adjust the flow rate of the airflow in the first conduit, and the flow meter 3 can be used to monitor the size of the airflow in the first conduit.

[0044] As an example, the aerosol generator 4 is used to generate aerosol particles. By connecting the outlet of the aerosol generator 4 to the first conduit, the aerosol generator 4 can inject aerosol particles into the first conduit, and the airflow in the first conduit drives the aerosol particles to flow toward the rotating impact emitter 5.

[0045] As an example, Figure 2 As shown, the rotary impactor 5 may include an inverted conical cylinder, a lid 50 located at the top of the cylinder, a rotating shaft 52 located at the center of the cylinder and extending perpendicularly through the lid 50 along the cylinder's axial direction, and multiple friction plates located within the cylinder, their centers coaxial with the rotating shaft 52. The multiple friction plates are spaced apart along the axial direction of the cylinder, and the rotating shaft 52 can be rotated by an external motor. Thus, after the aerosol enters the rotary impactor 5 under the influence of the airflow in the first conduit, it rubs against the multiple friction plates and separates, gradually converting the uncharged aerosol particles into charged particles for output.

[0046] The lid 50 and the barrel body 55 are interconnected to form an inverted conical cavity, which includes a cavity inlet 51 connected to the outlet of the first conduit and a cavity outlet 56 connected to the particle injection end of the airflow duct 18. The cavity inlet 51 corresponds to the input end of the rotary impact emitter 5 and is located on the side of the barrel body 55 close to the lid 50. The cavity outlet 56 corresponds to the output end of the rotary impact emitter 5 and is located on the side of the barrel body 55 away from the lid 50, i.e., at the bottom of the inverted conical cavity. The inverted conical cavity provides space for particles to rub against the friction plate and be converted into charged particles.

[0047] The multiple friction plates may include a plurality of rotating orifice plates 53 and annular baffles 54 spaced apart axially along the barrel 55, with the diameters of the rotating orifice plates 53 and the annular baffles 54 increasing from bottom to top. The annular baffle 54 is a circular insulating plate with a central circular hole. The diameter of the central circular hole of the annular baffle 54 is larger than the rotating shaft 52, so that when the outer edge of the annular baffle 54 is abutted and fixed against the inner wall of the barrel 55, a gap is maintained between the inner edge of the annular baffle 54 and the rotating shaft 52. The rotating orifice plate 53 is a circular insulating plate with multiple through-holes on its surface. The center of the rotating orifice plate 53 is fixed to the rotating shaft 52, and the edge of the rotating orifice plate 53 maintains a gap with the inner wall of the barrel 55, allowing the rotating orifice plate 53 to rotate within the cavity along with the rotating shaft 52. By configuring the multiple friction plates as a plurality of rotating orifice plates 53 and annular baffles 54 spaced sequentially along the axial direction of the barrel 55, the path of aerosol particles within the cavity is increased, and the number of friction events between the aerosol particles and the rotating orifice plates 53 and annular baffles 54 is increased. This, in turn, causes uncharged aerosol particles to gradually become charged during the friction process and transform into charged particles. The circular hole at the center of the annular baffle 54, the gap between the edge of the rotating orifice plate 53 and the inner wall of the barrel 55, and the multiple through-holes on the surface of the rotating orifice plate 53 all provide pathways for aerosol particles to move within the cavity. Furthermore, by providing multiple through-holes on the surface of the rotating orifice plate 53, clusters of aerosol particles can be separated, facilitating the subsequent measurement of individual charged particles.

[0048] In some embodiments, an electric field generating assembly is disposed around the airflow duct 18 and includes a first electrode 8 and a second electrode 14 disposed along the direction in which the duct extends, and a third electrode 12 and a fourth electrode 13 disposed perpendicular to the direction in which the duct extends. The first electrode 8 and the second electrode 14 form a flow-direction electric field within the airflow duct 18, which is used to provide an electric field force in the opposite direction of the clean airflow to the charged particles injected into the airflow duct 18; the third electrode 12 and the fourth electrode 13 form a vertical electric field within the airflow duct 18, which is used to provide an electric field force in the opposite direction of gravity to the charged particles injected into the airflow duct 18.

[0049] As an example, the charged particles are graphite particles that have become negatively charged after friction. After entering the airflow duct 18, the negatively charged graphite particles are driven by the aerodynamic force to move toward the outlet of the airflow duct 18. Thus, by disposing a first electrode 8 connected to the positive electrode of a power source between the inlet of the airflow duct 18 and the particle injection end, and a second electrode 14 connected to the negative electrode of a power source between the outlet of the airflow duct 18 and the particle injection end, a flow-directed electric field can be formed between the first electrode 8 and the second electrode 14. The direction of the first electric force experienced by the negatively charged graphite particles in the flow-directed electric field is opposite to the direction of the aerodynamic force. In other words, by adaptively adjusting the electric field strength of the first electric field to adjust the magnitude of the first electric force experienced by the graphite particles, for example, by gradually reducing the electric field strength of the first electric field, the flow-directed velocity of the graphite particles within the airflow duct 18 can be gradually reduced, so that after the graphite particles move along the flow direction within the airflow duct 18 to a first predetermined region, they remain stationary in the flow direction of the airflow duct 18, i.e., reach a first equilibrium state. At this time, the aerodynamic force and the first electric field force acting on the graphite particles in the flow direction of the airflow duct 18 are equal in magnitude and opposite in direction.

[0050] At the same time, by establishing a vertical electric field around the airflow duct 18 corresponding to the first predetermined region, positioning the third electrode 12 connected to the positive electrode of the power source vertically above the airflow duct 18, and positioning the fourth electrode 13 connected to the negative electrode of the power source vertically below the airflow duct 18, the vertical electric field can provide a second electric force equal in magnitude to, and opposite in direction to, the weight of the graphite particles moving into the first predetermined region. In other words, the graphite particles in the first equilibrium state remain relatively stationary in the first predetermined region of the airflow duct 18 both in the flow direction and in the vertical direction.

[0051] Because the clean airflow flowing through the first predetermined region of the airflow duct 18 can be considered to flow uniformly and stably, the aerodynamic force in the first predetermined region is almost negligible in the vertical direction, and the charged particles can be considered to be unaffected by the aerodynamic force of the clean airflow in the vertical direction. Therefore, in the first equilibrium state, the vertical force state of the charged particles in the first predetermined region can satisfy:

[0052] mg=ρ p V p g=qE f1 (1)

[0053] Among them, ρ p Density of charged particles, V p is the volume of the charged particle, g is the gravitational constant; q is the charge of the charged particle, E f1 is the vertical electric field strength in the first equilibrium state. The charge q of the charged particle can be calculated based on this formula.

[0054] Furthermore, after the graphite particles reach the first equilibrium state in the first preset area, the electric field strength of the vertical electric field is adaptively adjusted to adjust the magnitude of the second electric field force acting on the graphite particles, for example, by increasing the electric field strength of the vertical electric field, so that the charged particles can move toward the side close to the inner wall of the air flow duct 18 until they move into the second preset area and reach the second equilibrium state.

[0055] The second preset region is the near-wall region near the inner wall of the airflow duct 18. The vertical width of the near-wall region is typically 10 times the diameter of the charged particle. After entering the near-wall region, the charged particle will be affected by the combined effects of the vertical component of the aerodynamic force (i.e., lift) and the streamwise component (i.e., drag). Correspondingly, the near-wall aerodynamic coefficient of the particle also includes the streamwise drag coefficient and the vertical lift coefficient. Therefore, in the second equilibrium state, the graphite particle remains stationary in the vertical direction of the airflow duct 18. The sum of the vertical components of the gravity and aerodynamic force on the graphite particle should be equal in magnitude to the second electric field force, but opposite in direction.

[0056] Therefore, in the second equilibrium state, the force state of the vertically charged particles in the second preset area can satisfy:

[0057] ρ p V p g+F L =qE f2 (2)

[0058] Among them, E f2 is the vertical electric field strength in the second equilibrium state, F L is the vertical component of the aerodynamic force, i.e., the lift. Based on this formula, the lift force F on the charged particles near the wall can be calculated. L .

[0059] Therefore, based on the definition calculation formula of aerodynamic force, the mechanical equilibrium equivalence relationship of charged particles in the first equilibrium state and the second equilibrium state respectively, and the flow rate of the clean airflow at the corresponding position of the charged particles in the airflow duct 18, and combined with the size parameters of the charged particles and the position parameters in the second equilibrium state, it is possible to derive the expression of the flow drag coefficient and the vertical lift coefficient of the charged particles in the near-wall area.

[0060] By definition, the lift force F L and lift coefficient C L The relationship is as follows:

[0061] 2F L =C L ρ f (u f -u p ) 2 A p (3)

[0062] Among them, ρ f is the density of clean air flow, u f is the velocity of the clean airflow at the corresponding position of the charged particles in the second state, u p is the velocity of the charged particle, A p is the projected area of ​​the charged particle.

[0063] Since the particles are at rest in the second equilibrium state, u p =0, thus, combining formulas (1) to (3), we can get the lift coefficient C L The calculation formula is:

[0064]

[0065] Similarly, in the second equilibrium state, the force state of the charged particles in the flow direction in the second preset area can satisfy:

[0066] F D =qE l (5)

[0067] Among them, E l is the electric field strength flowing toward the electric field in the second equilibrium state, F D It is the component of aerodynamic force in the flow direction, that is, drag force.

[0068] By definition, the drag force F D and the drag coefficient C D satisfy:

[0069] 2F D =C D ρ f (u f -u p ) 2 A p (6)

[0070] Since the particles are at rest in the second equilibrium state, u p =0, thus, combining formula (1) and formula (4) to (6), we can get the drag force F D The drag coefficient C d satisfy:

[0071]

[0072] To facilitate acquisition of the size parameters and position parameters of the charged particles in the second equilibrium state, a transparent window is provided at a predetermined position in the airflow duct 18. A particle detection assembly consisting of multiple CCD cameras is also positioned around the circumference of the airflow duct 18 to track and locate target charged particles entering the first and second predetermined areas through the transparent window and measure their size parameters. The multiple CCD cameras include at least a top-view CCD camera 15 and a side-view CCD camera 16. To enhance the performance of the top-view CCD camera 15, a laser 10 and lens 9 can be used in conjunction with the top-view CCD camera 15 to enhance its field of view.

[0073] Here, the target charged particles are charged particles that reach a first equilibrium state in a first preset area and a second equilibrium state in a second preset area. The size parameters of the target charged particles include volume size and vertical projection area. The size parameters of the target charged particles include the vertical distance between the target charged particles and the inner wall of the airflow duct 18 after reaching the second equilibrium state.

[0074] In the above formula, the velocity u of the clean airflow at the location of the charged particles is f It is the key to calculate the drag coefficient and lift coefficient. For the flow velocity in the near-wall area, it can be obtained by the dimensionless velocity and dimensionless distance calculation formula, and it satisfies:

[0075]

[0076] Among them, u + is the dimensionless velocity, y + is the dimensionless distance, μ τ is the friction velocity, y is the vertical distance between the charged particles and the inner wall of the airflow duct 18 in the second equilibrium state, u f is the viscosity coefficient of the clean air flow, is the flow rate of the clean air flow in the first preset area, f D is the Darcy friction coefficient.

[0077] Therefore, based on formula (8), the flow rate u of the clean airflow corresponding to the charged particles at position y can be calculated as f Calculate the flow rate u of the clean air flow f satisfy:

[0078]

[0079] Among them, the flow rate of the clean air flow in the first preset area is The air velocity can be measured and obtained by a hot wire anemometer 11 connected to a preset position of the airflow duct 18 .

[0080] Therefore, based on formula (9), as well as formulas (4) and (7), the aerodynamic coefficient of the near-wall region (lift coefficient C L and the drag coefficient C D ) and the relationship between the charged particles at the y position, namely:

[0081]

[0082] According to the second aspect of the embodiment of the present application, a method for measuring the aerodynamic coefficient of a particle near the wall is also provided. Figure 3 As shown, the method includes using the measuring device described in any of the above embodiments, and includes the following steps:

[0083] S1, forming a clean airflow with a stable flow direction in the air flow duct.

[0084] S2, forming charged particles in the particle injection assembly and injecting the charged particles into the air flow duct.

[0085] S3, forming a flow electric field and a vertical electric field in the air flow duct, and controlling the electric field strengths of the flow electric field and the vertical electric field respectively, so that the charged particles reach a first equilibrium state in a first preset area of ​​the air flow duct.

[0086] S4, adaptively adjusting the electric field strength of the vertical electric field so that the charged particles in the first equilibrium state reach a second equilibrium state in a second preset area of ​​the airflow duct under the action of the electric field force of the vertical electric field.

[0087] S5, based on the position parameters of the charged particles in the second preset area, combined with the mechanical equilibrium equivalent relationship between the gravity, electric field force and aerodynamic force of the charged particles in the first equilibrium state and the second equilibrium state, obtain the expression of the aerodynamic force coefficient of the near-wall area.

[0088] Wherein, in step S4, before the step of adaptively adjusting the electric field strength of the vertical electric field, the method further includes tracking and locating the charged particles that have reached the first equilibrium state in the first preset area and acquiring size parameters thereof by using a particle detection component.

[0089] In step S4, after the step of adaptively adjusting the electric field strength of the vertical electric field, it also includes using a particle detection component to confirm whether the charged particles in the first equilibrium state move to the second preset area under the action of the electric field force of the vertical electric field, and obtaining the position relationship parameters between the charged particles that reach the second equilibrium state in the second preset area and the inner wall of the airflow duct.

[0090] It should be noted that the details not specifically described in the particle near-wall aerodynamic force coefficient measurement method described in the above embodiments can refer to the details described in the particle near-wall aerodynamic force coefficient measurement device in the above embodiments, which will not be described one by one here.

[0091] In summary, the present application provides a particle near-wall aerodynamic force coefficient measurement device and measurement method, which comprises a gas flow pipeline, a particle injection assembly and an electric field generating assembly. Among them, the gas flow pipeline is provided with a stable flow direction clean gas flow, the particle injection assembly is used to inject charged particles into the gas flow pipeline, and the electric field generating assembly is used to form a flow direction electric field and a vertical electric field in the gas flow pipeline. The flow direction electric field provides an electric field force in the opposite direction of the flow field for the charged particles in the gas flow pipeline; the vertical electric field provides an electric field force in the opposite direction of the gravity for the charged particles in the gas flow pipeline. By controlling the electric field intensity of the flow direction electric field and the vertical electric field, the charged particles can be kept stationary in the main flow area and the near-wall area, respectively, and the aerodynamic force coefficient of the charged particles in the near-wall area is calculated based on the size of the charged particles and the position in the near-wall area. The present application can measure the force characteristics and force laws of the charged particles at different wall positions, and improve the measurement accuracy and efficiency of the aerodynamic force coefficient of the charged particles in the near-wall area.

[0092] In the foregoing embodiment description, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the description, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the skilled in the art can combine and combine the different embodiments or examples described in the description and the features of the different embodiments or examples without contradiction.

[0093] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

Claims

1. A device for measuring the aerodynamic coefficient of particles near the wall, characterized in that: include: An airflow duct comprises an inlet end and an outlet end opposite to each other, and a particle injection end arranged between the inlet end and the outlet end; a clean airflow is provided in the airflow duct so as to stably flow along the extension direction of the duct; a particle injection assembly connected to the particle injection end and used to inject charged particles into the airflow duct; the particle injection assembly includes a first conduit, and a gas cylinder connected to the first conduit, an aerosol generator, and a rotary impact emitter; an electric field generating assembly, comprising a first electrode and a second electrode arranged along the extending direction of the pipeline, and a third electrode and a fourth electrode arranged perpendicular to the extending direction of the pipeline; Wherein, the aerosol generator is used to inject aerosol particles into the first conduit; the gas cylinder is used to provide driving force for the directional movement of the aerosol particles in the first conduit and the rotary impact launcher; the rotary impact launcher is used to convert the aerosol particles into the charged particles and inject them into the airflow duct; the rotary impact launcher includes an inverted conical cylinder, a barrel cover located on the top of the cylinder, a rotating shaft located at the center of the cylinder and vertically passing through the barrel cover along the axial direction, and a plurality of friction plates located inside the cylinder and coaxial with the rotating shaft, and the plurality of friction plates are arranged in sequence along the axial direction of the cylinder; the first conduit is connected to the input end of the rotary impact launcher, and the input end is arranged on the side of the cylinder close to the barrel cover; the particle injection end is connected to the output end of the rotary impact launcher, and the output end is arranged on the side of the cylinder away from the barrel cover; The first electrode and the second electrode form a flow electric field in the airflow duct, and the flow electric field is used to provide the charged particles injected into the airflow duct with an electric field force in the opposite direction of the clean airflow; the third electrode and the fourth electrode form a vertical electric field in the airflow duct, and the vertical electric field is used to provide the charged particles injected into the airflow duct with an electric field force in the opposite direction of gravity.

2. The measuring device according to claim 1, characterized in that The plurality of friction plates include a plurality of rotating orifice plates and annular baffles sequentially spaced along the axial direction of the cylinder; wherein, The outer edge of the annular baffle is fixed in contact with the inner wall of the cylinder, and the inner edge of the annular baffle maintains a gap with the rotating shaft; the center of the rotating orifice plate is fixed to the rotating shaft, and the edge of the rotating orifice plate maintains a gap with the inner wall of the cylinder, and each of the rotating orifice plates is provided with a plurality of through holes.

3. The measuring device according to claim 1, characterized in that The measuring device also includes an induced draft fan, a filter and a cold dryer; wherein the filter and the cold dryer are sequentially arranged on one side of the air flow duct close to the inlet end, and the induced draft fan is arranged on one side of the air flow duct close to the outlet end.

4. The measuring device according to claim 1, characterized in that The measuring device further includes a particle detection component, and the airflow duct is further provided with a transparent window. The particle detection component detects the size parameters and position parameters of the charged particles in the airflow duct through the transparent window.

5. A method for measuring the aerodynamic coefficient of a particle near a wall, comprising using the measuring device according to any one of claims 1 to 4, characterized in that: The measuring method comprises the steps of: Forming a clean airflow with a stable flow direction in the air duct; forming charged particles in a particle injection assembly and injecting the charged particles into the air flow duct; forming a flow-direction electric field and a vertical electric field in the airflow duct, and controlling the electric field intensities of the flow-direction electric field and the vertical electric field respectively, so that the charged particles reach a first equilibrium state in a first predetermined region of the airflow duct; Adaptively adjusting the electric field strength of the vertical electric field so that the charged particles in the first equilibrium state reach a second equilibrium state in a second preset area of ​​the airflow duct under the action of the electric field force of the vertical electric field; Based on the position parameters of the charged particles in the second preset area and the mechanical equilibrium equivalence relationship between the gravity, aerodynamic force and electric field force of the charged particles in the first equilibrium state and the second equilibrium state, the expression of the aerodynamic force coefficient near the wall is obtained.

6. The measuring method according to claim 5, characterized in that The aerodynamic coefficient of the charged particle in the second equilibrium state satisfies: Among them, C L is the lift coefficient of the vertical component of the aerodynamic force; C D is the drag coefficient of the streamwise component of the aerodynamic force; ρ p is the density of the charged particles; V p is the volume of the charged particle; A p is the vertical projection area of ​​the charged particle; y is the vertical distance between the charged particle and the inner wall of the air flow duct in the second equilibrium state; g is the gravity constant; E f1 is the electric field intensity of the vertical electric field in the first equilibrium state; E f2 is the electric field intensity of the vertical electric field in the second equilibrium state; E l is the electric field intensity flowing toward the electric field in the second equilibrium state; ρ f is the density of the clean airflow; f is the flow rate of the clean air flow in the first preset area; D is the Darcy friction coefficient; u f is the viscosity coefficient of the clean air flow.

7. The measuring method according to claim 5, characterized in that Before the adaptive adjustment of the electric field strength of the vertical electric field, the method further includes tracking and locating the charged particles that have reached the first equilibrium state in the first preset area and acquiring size parameters thereof by using a particle detection component.

8. The measuring method according to claim 7, characterized in that: After the step of adaptively adjusting the electric field strength of the vertical electric field, it also includes using the particle detection component to confirm whether the charged particles in the first equilibrium state move to the second preset area under the action of the electric field force of the vertical electric field, and obtaining the position relationship parameters between the charged particles that reach the second equilibrium state in the second preset area and the inner wall of the airflow duct.

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