Particle near-wall aerodynamic coefficient measuring device and measuring method

Abstract

The invention provides a device and a method for measuring a near-wall aerodynamic coefficient of particles. The device comprises an airflow pipeline, a particle injection assembly and an electric field generation assembly. Wherein clean airflow with a stable flow direction is arranged in the airflow pipeline, the particle injection assembly is used for injecting charged particles into the airflow pipeline, the electric field generation assembly is used for forming a flow direction electric field and a vertical electric field in the airflow pipeline, and the flow direction electric field is used for providing electric field force opposite to the flow field for the charged particles in the airflow pipeline; a vertical electric field is used for providing electric field force in the direction opposite to the 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 mainstream area and the near wall surface area respectively, and the aerodynamic coefficient of the charged particles in the near wall surface area is calculated based on the size of the charged particles and the position of the charged particles in the near wall surface area. According to the invention, the stress characteristics and stress rules of charged particles at different wall surface positions can be measured.

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 aerodynamic coefficients of particles near the wall based on electric field action. Background Art

[0002] In the energy field, compact heat exchangers such as printed circuit boards have broad application prospects due to their high heat transfer efficiency and compact structure. For example, in the field of advanced nuclear power, printed circuit board heat exchangers have important application potential in small modular reactors. However, since the flow channel size is only millimeter scale, dust particles carried in the fluid are easily deposited on the surface of the heat exchanger, thereby affecting the heat transfer thermal resistance. In severe cases, they may block the micro channels, thereby affecting the performance of the heat exchanger. Since dust particles move under the drive of the coolant airflow, it is crucial to measure the characteristics of the particles in the near-wall area affected by the airflow.

[0003] Existing studies have shown that airflow forms a shear flow with a significant velocity gradient in the near-wall region. The characteristics of the shear flow on particles are significantly different from those of particles in the traditional uniform flow. It not only increases the drag coefficient flowing to the particles, but also produces a significant normal lift coefficient component, and the force characteristics of the particles have different values ​​at different wall distances. However, the traditional method of measuring the force of airflow on particles mainly relies on mechanical balance, relying on gravity balance to measure the force on particles in the airflow, but it is impossible to quantitatively measure the force law of 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 some extent.

[0005] To this end, the purpose of this application is to propose a device and method for measuring the aerodynamic coefficients 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, 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 purpose, the first embodiment of the present application proposes a device for measuring aerodynamic coefficients of particles 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 arranged in the airflow duct and flows stably along the extending direction of the duct;

[0008] a particle injection assembly connected to the particle injection end and used to inject 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] Among them, 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 to the flow 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 to gravity.

[0011] Optionally, the particle injection assembly includes a first conduit, and a gas cylinder, an aerosol generator and a rotary impact emitter 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 emitter; and the rotary impact emitter 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 at 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 whose centers are coaxial with the rotating shaft, and the plurality of friction plates are arranged in sequence and spaced apart 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 a 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 a 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 apart along the axial direction of the cylinder; wherein,

[0014] The outer edge of the annular baffle is fixedly abutted against the inner wall of the cylinder, and a gap is maintained between the inner edge of the annular baffle and the rotating shaft; the center of the rotating orifice plate is fixed to the rotating shaft, and a gap is maintained between the edge of the rotating orifice plate and the inner wall of the cylinder, and each rotating orifice plate is provided with a plurality of through holes.

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

[0016] Optionally, the measuring device further comprises 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] Form 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 electric field and a vertical electric field in the airflow 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 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 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 airflow duct in the second equilibrium state; g is the gravity constant; E f1 is the electric field strength 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;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 by 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 the particle near the wall provided in the present application at least include the following

[0029] Beneficial effects:

[0030] The present application provides a device and method for measuring the aerodynamic coefficient of particles near the wall, including an airflow duct, a particle injection assembly and an electric field generating assembly. Among them, a clean airflow with a stable flow direction is provided in 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 flow direction electric field and a vertical electric field in the airflow duct, and the flow direction electric field is used to provide an electric field force in the opposite direction of the flow field for the charged particles in the airflow duct; the vertical electric field is used to provide an electric field force in the opposite direction of gravity for the charged particles in the airflow duct. By controlling the electric field strength of the flow direction electric field and the vertical electric field, the charged particles can be kept stationary in the mainstream area and the near-wall area respectively, and the aerodynamic 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 charged particles at different wall positions, and improve the measurement accuracy and efficiency of the aerodynamic coefficient of charged particles in the near-wall area.

[0031] 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 the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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:

[0033] Figure 1 It is a schematic structural diagram of a particle aerodynamic coefficient measuring device according to an embodiment of the present application.

[0034] Figure 2 It is a schematic diagram of the structure of a rotating impact launcher according to an embodiment of the present application.

[0035] 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.

[0036] 1 gas cylinder; 2 regulating valve; 3 flow meter; 4 aerosol generator; 5 rotating impact 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 air flow 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

[0037] Embodiments of the present application are described in detail below, and examples of the embodiments 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.

[0038] According to a first aspect of an embodiment of the present application, a device for measuring aerodynamic coefficients of particles near the wall is provided, such as Figure 1 As shown, the device includes a gas flow conduit 18, a particle injection assembly and an electric field generating assembly.

[0039] The airflow duct 18 is an insulating tube, including an inlet end and an outlet end opposite to each other, and a particle injection end disposed between the inlet end and the outlet end. The airflow duct 18 is used to form a clean airflow with a stable flow direction along the extension direction of the duct between the inlet end and the outlet end. The direction in which the duct extends may be referred to as the flow direction. The direction perpendicular to the extension direction of the duct may be referred to as the vertical direction.

[0040] In some embodiments, the outlet end of the airflow duct 18 is provided with an induced draft fan 17, and the inlet end of the airflow duct 18 is provided with a filter 6 and a cold dryer 7. Therefore, by turning on the induced draft fan 17, air in the environment can be introduced into the inlet end of the airflow duct 18, so that the air is filtered by the filter 6 and dried by the cold dryer 7 in sequence, and a clean airflow with a stable flow direction is formed in the airflow duct 18.

[0041] The particle injection assembly is used to form charged particles, and is connected to the particle injection end of the airflow duct 18 to inject the charged particles from the particle injection end into the airflow duct 18. The particle injection end is arranged on one side of the airflow duct 18 close to the inlet end, so that after the charged particles enter the airflow duct 18, they can move to one side of the outlet end under the aerodynamic force of the clean airflow that flows stably in the airflow duct 18.

[0042] In some embodiments, the particle injection assembly includes a first conduit, and a gas cylinder 1, an aerosol generator 4 and a rotary impact emitter 5 connected to the first conduit.

[0043] As an example, the inlet of the gas cylinder 1 is connected to the inlet of the first conduit, so that whenever the gas cylinder 1 and the switch valve are opened, the high-pressure gas filled in the gas cylinder 1 will instantly pass through the first conduit and the rotary impact emitter 5, and then enter the airflow pipeline 18, and flow out from the outlet end of the airflow pipeline 18. In other words, the role of the gas cylinder 1 is to provide a driving force for the subsequent aerosol particles to enter the rotary impact emitter 5 and the airflow pipeline 18 from the first conduit in sequence.

[0044] 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.

[0045] 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 aerosol particles are driven by the airflow in the first conduit to flow toward the rotating impact emitter 5.

[0046] As an example, Figure 2 As shown, the rotary impact launcher 5 may include an inverted cone-shaped cylinder, a barrel cover 50 located at the top of the cylinder, a rotating shaft 52 located at the center of the cylinder and vertically passing through the barrel cover 50 along the axial direction of the cylinder, and a plurality of friction plates located inside the cylinder and coaxial with the rotating shaft 52, wherein the plurality of friction plates are sequentially arranged at intervals along the axial direction of the cylinder, wherein the rotating shaft 52 may rotate under the drive of an external motor. Thus, after the aerosol enters the rotary impact launcher 5 driven by the airflow in the first conduit, it rubs and separates with the plurality of friction plates, and is gradually converted from aerosol particles with no charge properties to charged particles for output.

[0047] The barrel cover 50 and the barrel body 55 are connected to each other to form an inverted cone-shaped cavity, and the cavity 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 is equivalent to the input end of the rotary impact emitter 5, which is arranged on the side of the barrel body 55 close to the barrel cover 50, and the cavity outlet 56 is equivalent to the output end of the rotary impact emitter 5, which is arranged on the side of the barrel body 55 away from the barrel cover 50, that is, the bottom of the inverted cone-shaped cavity. The inverted cone-shaped cavity can provide space for the particles to rub against the friction plate and be converted into charged particles.

[0048] The plurality of friction plates may include a plurality of rotating orifice plates 53 and annular baffles 54 which are sequentially arranged at intervals along the axial direction of the barrel body 55, and the diameters of the plurality of rotating orifice plates 53 and the plurality of annular baffles 54 increase sequentially from bottom to top. The annular baffle 54 is an annular insulating plate with a circular hole at the center, and 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 body 55, the inner edge of the annular baffle 54 maintains a gap with the rotating shaft 52. The rotating orifice plate 53 is a circular insulating plate with a plurality of through holes on the surface, and 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 body 55, so that the rotating orifice plate 53 can rotate with the rotating shaft 52 in the cavity with the rotating shaft 52. By setting the multiple friction plates as multiple rotating orifice plates 53 and annular baffles 54 that are sequentially spaced along the axial direction of the barrel body 55, the movement path of the aerosol particles in the cavity can be increased, and the number of frictions between the aerosol particles and the rotating orifice plates 53 and the annular baffles 54 can be increased, so that the aerosol particles with no charge properties are gradually charged and converted into charged particles during the friction process, and the circular hole located 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 body 55, and the multiple through holes on the surface of the rotating orifice plate 53 all provide channels for the movement of aerosol particles in the cavity. At the same time, by setting multiple through holes on the surface of the rotating orifice plate 53, multiple aerosol particles in clusters can be separated to facilitate the subsequent measurement of single charged particles.

[0049] In some embodiments, the electric field generating assembly is arranged on the peripheral side of the airflow duct 18, including a first electrode 8 and a second electrode 14 arranged along the extension direction of the duct, and a third electrode 12 and a fourth electrode 13 arranged perpendicular to the extension direction of the duct. The first electrode 8 and the second electrode 14 form a flow direction electric field in the airflow duct 18, and the flow direction electric field 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 in the airflow duct 18, and the vertical electric field is used to provide an electric field force in the opposite direction of gravity to the charged particles injected into the airflow duct 18.

[0050] As an example, the charged particles are graphite particles with negative charges after friction, and after entering the airflow duct 18, the negatively charged graphite particles will move to the outlet end of the airflow duct 18 driven by the aerodynamic force. Therefore, by setting a first electrode 8 connected to the positive electrode of the power supply between the inlet end and the particle injection end of the airflow duct 18, and setting a second electrode 14 connected to the negative electrode of the power supply between the outlet end and the particle injection end of the airflow duct 18, a flow direction electric field can be formed between the first electrode 8 and the second electrode 14, and the direction of the first electric field force to which the negatively charged graphite particles are subjected in the flow direction 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 field force to which the graphite particles are subjected, for example, by gradually reducing the electric field strength of the first electric field, the speed of the graphite particles in the airflow duct 18 in the flow direction can be gradually reduced, so that after the graphite particles move to the first preset area along the flow direction in the airflow duct 18, they can remain stationary in the flow direction of the airflow duct 18, that is, reach a first equilibrium state. At this time, the aerodynamic force and the first electric field force exerted on the graphite particles in the flow direction of the airflow duct 18 are equal in magnitude and opposite in direction.

[0051] At the same time, by setting a vertical electric field on the circumference of the airflow duct 18 corresponding to the first preset area, and setting the third electrode 12 connected to the positive electrode of the power supply directly above the airflow duct 18 in the vertical direction, and setting the fourth electrode 13 connected to the negative electrode of the power supply directly below the airflow duct 18 in the vertical direction, the vertical electric field can provide the graphite particles moving into the first preset area with a second electric field force equal to the gravity of the graphite particles and opposite in direction. In other words, the movement state of the graphite particles in the first equilibrium state in the first preset area of ​​the airflow duct 18 is kept relatively static in both the flow direction and the vertical direction.

[0052] Since the clean airflow flowing through the first preset area of ​​the airflow duct 18 can be regarded as flowing evenly and stably, the aerodynamic force in the first preset area is almost negligible in the vertical direction, so that the charged particles can be regarded as not affected by the aerodynamic force of the clean airflow in the vertical direction. Therefore, in the first equilibrium state, the force state of the charged particles in the first preset area in the vertical direction can satisfy:

[0053] m=ρ p V p g=qE f1 (1)

[0054] 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 electric field strength of the vertical electric field in the first equilibrium state. According to this formula, the charge q of the charged particle can be calculated.

[0055] 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 on the graphite particles. For example, the electric field strength of the vertical electric field is increased so that the charged particles can move toward the side close to the inner wall of the airflow duct 18 until they move into the second preset area and reach the second equilibrium state.

[0056] The second preset area is the near-wall area near the inner wall of the airflow duct 18, and the width of the near-wall area in the vertical direction is usually 10 times the diameter of the charged particles. After entering the near-wall area, the charged particles will be affected by the vertical component of the aerodynamic force (i.e., lift) and the flow component (i.e., drag). Correspondingly, the near-wall aerodynamic coefficient of the particles also includes the flow drag coefficient and the vertical lift coefficient. Therefore, in the second equilibrium state, the graphite particles remain stationary in the vertical direction of the airflow duct 18, and the sum of the vertical components of the gravity and aerodynamic force they are subjected to should be equal in magnitude to the second electric field force, but opposite in direction.

[0057] Therefore, in the second equilibrium state, the force state of the vertically charged particles in the second preset area can satisfy:

[0058] ρ p V p g+F L =qE f2 (2)

[0059] Among them, E f2 is the vertical electric field strength in the second equilibrium state, F L is the vertical component of aerodynamic force, i.e. lift. According to this formula, the lift force F on charged particles near the wall can be calculated. L .

[0060] Therefore, based on the definition calculation formula of aerodynamic force, the equivalent relationship of mechanical equilibrium of charged particles in the first equilibrium state and the second equilibrium state respectively, and the flow velocity 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.

[0061] By definition, the lift force F L and lift coefficient C L The relationship is as follows:

[0062] 2F L =C L ρ f (u f -u p ) 2 A p (3)

[0063] 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.

[0064] 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:

[0065]

[0066] Similarly, in the second equilibrium state, the force state of the charged particles in the flow direction in the second preset area can satisfy:

[0067] F D =qE l (5)

[0068] Among them, E l is the electric field strength flowing to the electric field in the second equilibrium state, F D It is the component of aerodynamic force in the flow direction, that is, drag.

[0069] By definition, the drag force F D and the drag coefficient C D satisfy:

[0070] 2F D =C D ρ f (u f -u p ) 2 A p (6)

[0071] 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:

[0072]

[0073] In order to facilitate the acquisition of the size parameters of the charged particles and the position parameters in the second equilibrium state, a transparent window is also provided at the preset position of the airflow duct 18, and a particle detection component composed of multiple CCD cameras is synchronously provided on the peripheral side of the airflow duct 18 to track and locate the target charged particles entering the first preset area and the second preset area through the transparent window and measure the size parameters. The multiple CCD cameras include at least a top-view CCD camera 15 and a side-view CCD camera 16. In order to make the top-view CCD camera 15 work better, a laser 10 and a lens 9 can also be used in combination with the top-view CCD camera 15 to improve the field of view intensity of the top-view CCD camera 15.

[0074] 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.

[0075] 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:

[0076]

[0077] 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, and 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.

[0078] Therefore, based on formula (8), the velocity 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:

[0079]

[0080] Among them, the flow rate of the clean air flow in the first preset area is The value can be obtained by measuring with a hot wire anemometer 11 connected to a preset position of the airflow duct 18 .

[0081] Therefore, based on formula (9), as well as formulas (4) and (7), the aerodynamic coefficient (lift coefficient C) of the near-wall region can be obtained. L and the drag coefficient C D ) and the charged particle at the y position, namely:

[0082]

[0083] According to a second aspect of the embodiment of the present application, a method for measuring aerodynamic coefficients of particles 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:

[0084] S1, forming a clean airflow with a stable flow direction in the air flow duct.

[0085] S2, forming charged particles in the particle injection assembly, and injecting the charged particles into the air flow duct.

[0086] S3, forming a flow electric field and a vertical electric field in the airflow 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 airflow duct.

[0087] 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.

[0088] S5, based on the position parameters of the charged particles in the second preset area, combined with the mechanical equilibrium equivalence 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 coefficient of the near-wall area.

[0089] 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 by using a particle detection component and acquiring size parameters.

[0090] 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.

[0091] It should be noted that the details not specifically described in the method for measuring the aerodynamic coefficient of the particle near the wall described in the above embodiment can refer to the details described in the device for measuring the aerodynamic coefficient of the particle near the wall in the above embodiment, and will not be described one by one here.

[0092] In summary, the present application provides a device and method for measuring the aerodynamic coefficient of particles near the wall, including an airflow duct, a particle injection assembly and an electric field generating assembly. Among them, a clean airflow with a stable flow direction is provided in 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 flow direction electric field and a vertical electric field in the airflow duct, and the flow direction electric field is used to provide an electric field force in the opposite direction of the flow field for the charged particles in the airflow duct; the vertical electric field is used to provide an electric field force in the opposite direction of gravity for the charged particles in the airflow duct. By controlling the electric field strength of the flow direction electric field and the vertical electric field, the charged particles can be kept stationary in the mainstream area and the near-wall area respectively, and the aerodynamic 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 charged particles at different wall positions, and improve the measurement accuracy and efficiency of the aerodynamic coefficient of charged particles in the near-wall area.

[0093] In the description of the aforementioned embodiments, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0094] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

Claims

1. A device for measuring aerodynamic coefficients 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 arranged in the airflow duct and flows stably along the extending direction of the duct; a particle injection assembly connected to the particle injection end and used to inject charged particles into the air flow duct; 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; Among them, 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 to the flow 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 to gravity.

2. The measuring device according to claim 1, characterized in that The particle injection assembly includes a first conduit, and a gas cylinder, an aerosol generator and a rotary impact emitter 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 emitter; the rotary impact emitter is used to convert the aerosol particles into the charged particles and inject them into the airflow duct.

3. The measuring device according to claim 2, characterized in that The rotary impact launcher comprises an inverted conical cylinder, a barrel cover located at 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 whose centers are coaxial with the rotating shaft, wherein the plurality of friction plates are sequentially spaced 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 a 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 a side of the cylinder away from the barrel cover.

4. The measuring device according to claim 3, characterized in that The plurality of friction plates include a plurality of rotating orifice plates and annular baffles which are sequentially spaced apart along the axial direction of the cylinder; wherein, The outer edge of the annular baffle is fixedly abutted against the inner wall of the cylinder, and a gap is maintained between the inner edge of the annular baffle and the rotating shaft; the center of the rotating orifice plate is fixed to the rotating shaft, and a gap is maintained between the edge of the rotating orifice plate and the inner wall of the cylinder, and each rotating orifice plate is provided with a plurality of through holes.

5. 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 air dryer are sequentially arranged on one side of the airflow duct close to the inlet end, and the induced draft fan is arranged on one side of the airflow duct close to the outlet end.

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

7. A method for measuring aerodynamic coefficients of particles near the wall, comprising using the measuring device according to any one of claims 1 to 6, characterized in that: The measuring method comprises the steps of: Form 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 electric field and a vertical electric field in the airflow 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 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.

8. The measuring method according to claim 7, 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 airflow duct in the second equilibrium state; g is the gravity constant; E f1 is the electric field strength 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; 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.

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

10. The measuring method according to claim 9, characterized in that: After the step of adaptively adjusting the electric field strength of the vertical electric field, the method 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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