Method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow

Abstract

The invention discloses a method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow, which belongs to the technical field of aerodynamic measurement, and comprises the following steps: constructing a measurement system with a fluidization cavity and an image acquisition assembly, and integrating two cameras in the measurement system and a signal acquisition processing unit configured with TEMA software to obtain the aerodynamic characteristic parameters of the non-spherical particles in the gas-solid two-phase flow. And in cooperation with the optimal design of an aerodynamic characteristic parameter calculation formula, the aerodynamic characteristic parameters of the non-spherical particles can be accurately calculated in a mode of obtaining time sequence data of the non-spherical particles in the gas-solid two-phase flow. According to the method, drag force and lift force generated by the non-spherical particles in translational motion and torque force generated by the non-spherical particles in rotational motion due to shape and orientation can be fully considered, the aerodynamic characteristic parameters of the non-spherical particles are accurately calculated, conditions are provided for simulation of the motion trail of the non-spherical particles in gas-solid two-phase flow, and the method is suitable for simulation of the non-spherical particles in the gas-solid two-phase flow. And a theoretical basis is provided for aerodynamic design when the biomass material particles are subjected to blending combustion in a coal-fired boiler.

Description

Technical Field

[0001] The invention belongs to the technical field of pneumatic measurement, and in particular relates to a method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow. Background Art

[0002] At present, the practice of mixing biomass fuels with coal-fired units has become an effective way to reduce greenhouse gas emissions and rationally utilize biomass waste.

[0003] In actual use, biomass materials are mostly crushed into particles for use. The crushed biomass particles, especially straw particles, are highly non-spherical and mostly long cylindrical. Due to the specificity of the particle shape, the aerodynamic behavior of biomass particles is significantly different from that of conventional spherical coal powder particles.

[0004] For traditional spherical particles, their particle dynamics models mostly ignore the complex aerodynamic characteristics brought about by the non-spherical shape of the particles, such as the drag coefficient, lift coefficient and torque coefficient. As a result, conventional particle dynamics models cannot be effectively applied to the aerodynamic parameter measurement of non-spherical particles, nor can they accurately simulate the movement trajectory of particles in the combustion chamber of a coal-fired boiler, and thus cannot effectively predict the combustion behavior of biomass particles.

[0005] Although there have been some studies on the measurement of aerodynamic characteristic parameters of non-spherical particles in the prior art, most of the existing studies use simple two-dimensional models, and the design theory is derived from the measurement principle of spherical particles. It is difficult to accurately simulate the actual motion of non-spherical particles, and it also ignores the influence of the orientation of non-spherical particles (i.e., the angle of incidence) on mechanical properties such as drag and lift in translational motion and torque in rotational motion. It is impossible to accurately measure the aerodynamic characteristic parameters of non-spherical particles, and there are great limitations. Summary of the invention

[0006] In response to one or more of the above-mentioned defects or improvement needs of the prior art, the present invention provides a method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow, which can be effectively applied to the measurement of aerodynamic characteristic parameters of non-spherical biomass particles, accurately realize the calculation of the drag coefficient, lift coefficient and / or torque coefficient of non-spherical biomass particles, and provide a theoretical basis for the blending of biomass fuel in coal-fired units.

[0007] To achieve the above object, the present invention provides a method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow, which includes the following process: (1) Construct a measurement system including a fluidization cavity and an image acquisition component; The fluidized cavity is a circular tubular structure made of a transparent material, with an open top and arranged vertically, and the bottom is connected to the air supply component; the image acquisition component includes two cameras and a signal acquisition processing unit respectively connected to the two cameras in communication, and the signal acquisition processing unit is configured with TEMA software for calculating the time series data of the test particles by receiving two groups of images continuously acquired by the two cameras; (2) Determine a shooting interval on the wall of the fluidized cavity and mark a plurality of points on the wall of the shooting interval; adjust the shooting fields of view of the two cameras so that the shooting fields of view of the two cameras can cover all the points and keep the image magnification ratio consistent after focusing; (3) obtaining material parameters of the non-spherical test particles and controlling the air supply assembly to form a stable airflow field in the fluidized cavity; discharging the particles from the top of the fluidized cavity through the discharging mechanism, and controlling two cameras to continuously capture images of the test particles as they pass through a capturing interval, thereby obtaining two groups of time series images of the test particles; (4) The signal acquisition and processing unit obtains time series data of the non-spherical test particles, wherein the time series data includes at least the position, velocity, acceleration, incident angle, angular velocity, and angular acceleration of the particles; and the aerodynamic characteristic parameters of the non-spherical test particles are calculated using the time series data, and the drag coefficient in the aerodynamic characteristic parameters of the non-spherical test particles is calculated. , lift coefficient and torque coefficient Calculate using the following formula:

[0008] In the formula, , , They are drag force, lift force and torque force exerted by fluid on particles respectively; , , , They represent air density, particle density, particle volume and particle mass respectively; Represents the projected area perpendicular to the direction of motion during the particle falling process, where A 0 is the projected area of ​​the particle facing the airflow direction at the beginning of the falling process; and Represent the velocity of fluid and particles respectively; It is the angle between the fluid flow direction and the long axis direction of the particle in the measurement area, that is, the incident angle at different times; is the acceleration of the particle; , are the particle angular velocity and moment of inertia, respectively. For long cylindrical particles, the moment of inertia , is the minor semi-axis length of the particle; is the angular acceleration of the particle; It is the equivalent diameter of a spherical particle with the same volume as the particle being measured.

[0009] As a further improvement of the present invention, in process (1), the air supply assembly includes a blower and an air storage tank which are connected in sequence, the bottom of the fluidizing cavity is connected to the air storage tank, and a flow meter is provided corresponding to the air storage tank; and / or, A discharge mechanism is arranged at the top of the fluidized cavity, and a particle release sensor is arranged corresponding to the discharge mechanism; the discharge mechanism is electrically connected to the signal acquisition and processing unit through the particle release sensor.

[0010] As a further improvement of the present invention, the two cameras are respectively multifunctional high-speed cameras, the exposure time of which is in the range of 80µs to 120µs, and the frame rates of the two cameras are controlled in the range of 2000 to 5000 frames per second.

[0011] As a further improvement of the present invention, light sources are further provided corresponding to the two cameras for providing illumination for the shooting intervals of the two cameras.

[0012] As a further improvement of the present invention, in process (2), the signal acquisition processing unit completes the determination of the posture of the particle in the three-dimensional space by an 8-point method, and the method includes the following process: (2.1) performing point calibration, calibrating 8 position points on the wall surface of the shooting interval of the fluid cavity; (2.2) Collect images of the measured area, use two cameras to capture images at different angles, and make sure that the eight positions are within the field of view of the two cameras; (2.3) Using the principles of camera imaging and geometric projection, establish the correspondence between the coordinates of each 2D point in the image and its 3D coordinates in real space; (2.4) Perform spatial transformation calculations, link the two-dimensional point coordinates in the image with the real spatial coordinates through multi-view geometry calculations, and generate a three-dimensional coordinate system for analysis based on TEMA software; (2.5) The two cameras continuously capture images of the particles passing through the measured area, and the TEMA software is used to capture the movement trajectory of the particles in the three-dimensional coordinate system, and then the time series data of the particles are output.

[0013] As a further improvement of the present invention, the thickness of the tube body of the fluidized cavity is 0.01-0.02 m, the outer diameter of the tube body is 0.10-0.20 m, and the height of the tube body is 1.0-1.5 m; and in process (2), the shooting field of view is located at a distance of 0.6-0.9 m from the bottom of the fluidized cavity.

[0014] As a further improvement of the present invention, in process (3), the discharge position of the non-spherical particles to be measured is the center position of the top of the fluidization cavity; and / or, The non-spherical measuring particles are in a horizontal state when being discharged. As a further improvement of the present invention, when calculating the time series data in process (4), the time series data of the non-spherical measured particles at a certain incident angle is obtained by averaging the measured data within a numerical change of the incident angle of no more than 2°.

[0015] As a further improvement of the present invention, the non-spherical measurement particles are long cylindrical straw hollow particles.

[0016] The above-mentioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0017] In general, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects: (1) The method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow in the present invention constructs a measurement system with a fluidization chamber and an image acquisition component, utilizes the integrated setting of two cameras and a signal acquisition and processing unit equipped with TEMA software in the measurement system, and combines it with the optimal design of the aerodynamic characteristic parameter calculation formula. The aerodynamic characteristic parameters of non-spherical particles can be accurately calculated by obtaining the time series data of non-spherical particles in the gas-solid two-phase flow, fully considering the translational motion and rotational motion of non-spherical particles when moving in the airflow field, greatly improving the acquisition accuracy of non-spherical particle motion data, providing a basis for accurately simulating the motion trajectory of non-spherical particles, and promoting the research and application of non-spherical particles. (2) The method of measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow in the present invention ensures that the two cameras in the measurement system can accurately collect the motion data of the test particles in three-dimensional space from different angles by optimizing the structural parameters and setting forms of each component in the measurement system, thereby ensuring the accuracy and reliability of experimental data acquisition and further improving the measurement accuracy of the measurement method.

[0018] (3) The method of measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow in the present invention has simple steps and convenient operation. It can accurately obtain the three-dimensional motion data of non-spherical particles in gas-solid two-phase flow, fully consider the translation and rotation of non-spherical particles in motion, and accurately calculate the aerodynamic characteristic parameters of non-spherical particles. It provides conditions for simulating the motion trajectory of non-spherical particles in gas-solid two-phase flow, and further provides conditions for the aerodynamic design of biomass material particles when they are mixed in coal-fired boilers. It has good practical value and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 is a flow chart of a method for measuring aerodynamic characteristic parameters of non-spherical particles in a gas-solid two-phase flow in an embodiment of the present invention; Figure 2 Schematic diagram of a measurement system used in a method for measuring aerodynamic characteristic parameters of non-spherical particles in a gas-solid two-phase flow in an embodiment of the present invention; In all the drawings, the same reference numerals represent the same technical features, specifically: 1. Blower; 2. Flow meter; 3. Gas storage tank; 4. Fluidization cavity; 5. Light source; 6. Discharging mechanism; 7. Particle release sensor; 8. First camera; 9. Second camera; 10. Signal acquisition and processing unit. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] In the description of the present invention, it should be understood that, unless otherwise expressly specified and limited, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0023] 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, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0024] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0026] Example: The method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow in the preferred embodiment of the present invention is intended to simulate the state of non-spherical particles, especially non-spherical biomass straw particles, when moving in gas-solid two-phase flow, and complete the acquisition of some dynamic parameters based on the relevant processing of TEMA software, thereby completing the calculation of the drag coefficient, lift coefficient and / or torque coefficient of the non-spherical particles in the gas-solid two-phase flow, providing a theoretical basis for the blending of non-spherical biomass fuel particles in coal-fired boilers.

[0027] It should be noted that the “TEMA software” used in the preferred embodiment of the present invention is called “TEMA Advanced Motion Analysis Tool”, which is an advanced motion analysis tool developed by Swedish Image Systems AB. It can obtain time series data of the photographed object at high speed and high precision based on images continuously shot in three-dimensional space. The time series data includes position, speed, acceleration, incident angle, angular velocity, angular acceleration and other data information.

[0028] Specifically, Figure 1 As shown in the preferred embodiment, a method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow preferably includes the following process: (1) constructing a measurement system, which includes a fluidizing cavity 4, a discharge mechanism 6, and an image acquisition component; The fluidized cavity 4 is a circular tubular structure made of a transparent material, which is arranged vertically, has an open top, and is connected to a gas supply assembly at the bottom, and the gas supply assembly can form an air flow field for testing in the fluidized cavity 4. In a preferred embodiment, the gas supply assembly includes a blower 1 and a gas storage tank 3 connected in sequence, the bottom of the fluidized cavity 4 is connected to one end of the gas storage tank 3, and a flow meter 2 is provided corresponding to the gas storage tank 3 for monitoring the gas flow in the gas storage tank 3.

[0029] By combining the blower 1, the gas storage tank 3 and the flow meter 2, a required air flow field can be formed in the fluidizing cavity 4, thereby simulating the working environment of the non-spherical biomass particles in actual application scenarios.

[0030] In actual settings, the fluidized cavity 4 is set as a circular tubular structure to prevent the collected particle image from being "distorted", that is, the edges and corners of the real fluidized cavity in the image have a certain degree of influence on the shape and movement process of the particles, thereby fully ensuring the accuracy of particle image collection.

[0031] More preferably, in actual setting, the fluidized cavity 4 is preferably made of transparent acrylic material, with a tube thickness of 0.01-0.02 m, an outer diameter of 0.10-0.20 m, and a height of 1.0-1.5 m. The actual measurement interval of the particle image is preferably located at a position 0.6-0.9 m from the bottom of the fluidized cavity 4. The reason for selecting this position interval to collect the particle image is that after a certain distance of falling after the discharge, the particle state in the image is closer to the particle state in the real situation, and the gas in the cavity here can also fully develop into turbulence, effectively avoiding the turbulence that may exist at the gas inlet from affecting the measurement results.

[0032] Furthermore, the discharge mechanism 6 is arranged at the top opening of the fluidizing cavity 4, and the image acquisition assembly in the preferred embodiment includes two cameras arranged in pairs and a signal acquisition processing unit 10 respectively connected to the two cameras. The two cameras are arranged on one side of the fluidizing cavity 4, that is, Figure 2 The first camera 8 and the second camera 9 shown in the figure respectively shoot the non-spherical particles in the fluidized cavity 4 from different angles, and are further preferably multifunctional high-speed cameras, with a maximum frame rate of not less than 2000 frames / second and a minimum exposure time of not less than 1µs. In more detail, the exposure time of the two cameras is within the range of 3.9µs~1s, and the frame rates of the two cameras are controlled within the range of 0~200000 frames / second.

[0033] For example, in a specific preferred embodiment, the two cameras used are Photron-FastcamMini UX50, with a maximum resolution of 1280×1024, a maximum frame rate of 200,000 frames / second, and a shortest exposure time of 3.9 μs.

[0034] In actual settings, exposure time and frame rate are important parameters of high-speed cameras. If the exposure time is too long, it is easy to produce smears, which will affect the experimental results; if the exposure time is too short, the brightness of the collected image will be too dark, the contrast between the particles and the background will not be obvious, and the difficulty of image processing will increase. If the frame rate is set too low, too few images will be recorded in the measurement area, and the accuracy of the experimental results will be difficult to guarantee; if the frame rate is set too high, too many images will be recorded, and the workload of later image processing will increase. Therefore, in a preferred embodiment, the exposure time of the two cameras is preferably set in the range of 80µs~120µs, and the frame rate of the two cameras is preferably controlled in the range of 2000~5000 frames / second.

[0035] More preferably, in actual setting, in order to make the contrast between the particles and the background more obvious, a light source 5 is preferably arranged on the side of the fluidization cavity 4 away from the two cameras to provide sufficient illumination for the measured area.

[0036] In specific settings, the two cameras may share one light source 5, or light sources 5 may be provided for the two cameras respectively, which will not be described in detail here.

[0037] In addition, the signal acquisition and processing unit 10 in the preferred embodiment is configured with TEMA software, which can calculate the time series data of the test particles by receiving two groups of images continuously acquired by two cameras.

[0038] In more detail, in the preferred embodiment, a particle release sensor 7 is also provided corresponding to the discharge mechanism 6. The particle release sensor is electrically connected to the discharge mechanism 6 and the signal acquisition and processing unit 10, respectively, and can accurately implement the discharge control process of the discharge mechanism 6 and clarify the initial time of discharge.

[0039] (2) Conducting preparation before the test, determining a shooting interval on the wall of the fluidization cavity 4, and marking a plurality of points on the wall of the shooting interval; thereafter, adjusting the shooting fields of view of the two cameras so that the shooting fields of view of the two cameras can cover all the points and keep the image magnification ratio consistent after focusing; In actual operation, the camera's shooting field of view setting can be completed by selecting several pairs of points from multiple points and controlling the distances between corresponding points in the shooting fields of view of the two cameras to be equal.

[0040] In more detail, in a preferred embodiment, the number of marking points selected for the shooting field is 8, and the 8-point method of TEMA software is used to complete the determination of the posture of the particles in the three-dimensional space. The method preferably includes the following process: (2.1) Calibrate the points and calibrate 8 known positions in the measured area of ​​the particle fluidization cavity; (2.2) Collect images of the measured area, use two cameras to capture images at different angles, and make sure that the eight positions are within the field of view of the two cameras; (2.3) Using the principles of camera imaging and geometric projection, establish the correspondence between the coordinates of each 2D point in the image and its 3D coordinates in real space; (2.4) Perform spatial transformation calculations, link the two-dimensional point coordinates in the image with the real spatial coordinates through multi-view geometry calculations, and generate a three-dimensional coordinate system for analysis based on TEMA software; (2.5) The two cameras continuously capture images of the particles passing through the measured area, and the TEMA software is used to capture the movement trajectory of the particles in the three-dimensional coordinate system, and then the time series data of the particles are output.

[0041] In a preferred embodiment, the time series data that can be output for the measured particles include the position, velocity, acceleration, incident angle, angular velocity, angular acceleration, etc. of the particles.

[0042] In actual measurement, due to the particularity of non-spherical particles, it is difficult to maintain the falling process under an ideal incident angle. Therefore, in actual calculation, it is necessary to ensure as much as possible that the particles maintain a stable falling trend within the calculation interval (the movement process under a specific incident angle). At this time, it is necessary to ensure that the change in the incident angle value of the particles within the interval is no more than 2°. By averaging the data within the interval that meets the above conditions, the time series data of the measured particles at a certain incident angle can be obtained.

[0043] (3) Determine the material parameters of the test particles, which at least include the size parameters, weight, density, etc. of the test particles; determine the gas flow rate range during the test in the fluidized cavity 4 according to the parameters of the test particles, and complete the control of the flow field environment in the fluidized cavity 4 through the coordinated control of the blower 1 and the gas storage tank 3; thereafter, the discharge mechanism 6 completes the release of the test particles, and the two cameras complete the shooting of the time series images of the test particles, and then the signal acquisition and processing unit 10 completes the acquisition of the time series data of the test particles; In actual operation, it is preferred to control the discharge mechanism 6 so that the particles to be measured are in a horizontal state when discharging the particles, and fall freely from the center position of the top of the fluidizing cavity 4 .

[0044] (4) Calculate the aerodynamic characteristic parameters of the non-spherical particles based on the time series data of the measured particles. The aerodynamic characteristic parameters include the drag coefficient, lift coefficient and torque coefficient of the non-spherical particles when they move in the gas-solid two-phase flow. The calculation process is as follows: (4.1) Based on the average acceleration of the measured particle at the average incident angle, the drag and lift of the measured particle during translational motion are calculated as follows;

[0045]

[0046] In the formula, , , are drag force, lift force and resultant force of particle translational motion; , , , They represent air density, particle density, particle volume and particle mass respectively; is the dimensionless drag coefficient; Represents the projected area perpendicular to the direction of motion during the particle falling process, where A 0 is the projected area of ​​the particle facing the airflow direction at the beginning of the falling process; and Represent the velocity of fluid and particles respectively; It is the angle between the fluid flow direction and the long axis direction of the particle in the measurement area, that is, the incident angle at different times; is the acceleration of the particle; (4.2) Calculate the torque force on the measured particle during rotational motion. The calculation process is as follows:

[0047] In the formula, , and are the particle angular velocity, moment of inertia, and torque force exerted by the fluid on the particle, respectively; is the angular acceleration of the particle; for long cylindrical particles, the moment of inertia , is the minor semi-axis length of the particle; (4.3) The drag, lift and torque acting on the particle are dimensionless, and the aerodynamic characteristic parameters of the particle are calculated; combined with the formulas in (4.1) and (4.2), the drag coefficient in the aerodynamic characteristic parameters of non-spherical particles is , lift coefficient and torque coefficient The calculation process is as follows:

[0048] In the formula, It is the equivalent diameter of a spherical particle with the same volume as the particle being measured.

[0049] As follows, the method in the preferred embodiment of the present invention is further verified and explained through a specific example.

[0050] In this specific embodiment, the aerodynamic characteristic parameter test of the particle to be tested is first completed by the technical solution in the aforementioned preferred embodiment, and the drag coefficient, lift coefficient and torque coefficient of the particle to be tested are calculated; thereafter, the above-mentioned measurement parameters measured by the experiment are cross-validated with the OpenFOAM direct numerical simulation results.

[0051] In detail, the experimental process in this specific embodiment is as follows: (1) Reference Figure 2 Construct a measurement system for non-spherical particles using the settings in the table and select the particles to be measured; In this embodiment, the particles to be tested are long cylindrical straw hollow particles, and the semi-major axis length of the particles is b is 0.02m, the bottom radius (semi-minor axis length) is 0.002m, and the aspect ratio =10, and the volume of the cylindrical straw biomass pellets is calculated using the cylinder volume calculation formula is 5.026×10 -7 m 3 .

[0052] At the same time, the mass of the particles to be tested is measured by an electronic balance. is 0.08g, using the formula The density of the calculated particles is 159.15Kg / m 3 .

[0053] It should be noted that since the particles to be tested are crushed particles of biomass mixed with combustion in industrial coal-fired boilers, for the same type of biomass, there will be certain differences in density between different particles. Therefore, it is necessary to screen the experimental particles, remove particles with large density differences, and take the average density of the selected particles.

[0054] (2) In this example, the blower 1 is a Roots blower. The flow rate setting of the flow meter 2 is adjusted to set the air flow velocity from bottom to top to 1.03 m / s. At the same time, the air temperature in the fluidizing cavity 4 is measured by a thermometer and is 25°C. By consulting the data, the density of the air is 1.184 Kg / m 3 , the dynamic viscosity of air is 1.849×10 -5 Pa•s.

[0055] In actual operation, the air velocity is measured by a flow meter to measure the air flow in the fluidizing cavity. The circular cross-sectional area of ​​the fluidizing cavity 4 (the inner diameter of the cross section is 0.12m) is known, and the air velocity is calculated using the formula: is 1.023m / s, where is the air flow rate in the fluidizing cavity, which is 41.67Nm 3 / h; The circular area under the representative cavity cross section is 0.0113m 2 .

[0056] (3) Turn on the light source, release the particles to be tested through the discharge mechanism 6 at the center position of the top of the cylindrical fluidized cavity 4, and use two multifunctional high-speed cameras to capture the time series images of the particles to be tested in the tested area (the measurement interval is located at a height of 0.7m~0.8m from the bottom of the fluidized cavity 4).

[0057] (4) The control signal acquisition processing unit 10 receives and processes the images taken by the two cameras. After image processing and Tema motion analysis software, the incident angle of the particle can be obtained. When the temperature is 68℃, the average combined velocity of the particles in three-dimensional falling is 1.991 m / s, and the average combined acceleration is 15.874 m / s 2 , the average angular acceleration changes to 1700 rad / s -2 , the projected area perpendicular to the direction of motion during the particle falling process is 1.826×10-4 m 2 .

[0058] At this time, according to the calculation formula of particle Reynolds number , we can calculate that its Reynolds number is 611, where , the calculated result is 0.00986m. At the same time, the moment of inertia is expressed as The calculated result is 1.6×10 -10 Kg•m 2 .

[0059] Based on these data, the drag coefficient is calculated to be 1.5687, the lift coefficient is 0.5329, and the torque coefficient is 0.5449 using the formula (4.3) in the preferred embodiment.

[0060] (5) Verify the results; The drag coefficient, lift coefficient and torque coefficient calculated experimentally were compared with the direct simulation results of the body-fitting grid method of the fluid dynamics software OpenFOAM. Among them, OpenFOAM directly simulated the fluid force of long cylindrical particles based on the icoFoam solver under the finite volume method, and used standard aerodynamic theory to calculate the theoretical values ​​of the aerodynamic characteristic parameters of the particles to be tested under the same experimental conditions, and compared them with the aforementioned measured values.

[0061] Specifically, the theoretical drag coefficient calculated by direct numerical simulation is 1.631, and the experimental result is 1.5687, with an error of 3.81%; the theoretical lift coefficient calculated by direct numerical simulation is 0.5576, and the experimental result is 0.5329, with an error of 4.43%; the theoretical torque coefficient calculated by direct numerical simulation is 0.5721, and the experimental result is 0.5449, with an error of 4.75%.

[0062] By comparison, it can be seen that the measurement method designed in the preferred embodiment of the present invention is very close to the theoretical calculation results calculated by direct numerical simulation, and the errors are all within a reasonable range (the error does not exceed 5%). This shows that the designed measurement system and measurement method can accurately measure the aerodynamic characteristic parameters (drag coefficient, lift coefficient and torque coefficient) of non-spherical particles.

[0063] The method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow in the present invention has simple steps and convenient operation, can accurately obtain three-dimensional motion data of non-spherical particles in gas-solid two-phase flow, fully considers the translation and rotation of non-spherical particles in motion, accurately calculates the aerodynamic characteristic parameters of non-spherical particles, provides conditions for simulating the motion trajectory of non-spherical particles in gas-solid two-phase flow, and further provides conditions for aerodynamic design of biomass material particles when they are mixed and burned in coal-fired boilers, and has good practical value and application prospects.

[0064] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow, characterized in that: The process includes the following: (1) Construct a measurement system including a fluidization cavity and an image acquisition component; The fluidized cavity is a circular tubular structure made of a transparent material, with an open top and arranged vertically, and the bottom is connected to the air supply component; the image acquisition component includes two cameras and a signal acquisition processing unit respectively connected to the two cameras in communication, and the signal acquisition processing unit is configured with TEMA software for calculating the time series data of the test particles by receiving two groups of images continuously acquired by the two cameras; (2) Determine a shooting interval on the wall of the fluidized cavity and mark a plurality of points on the wall of the shooting interval; adjust the shooting fields of view of the two cameras so that the shooting fields of view of the two cameras can cover all the points and keep the image magnification ratio consistent after focusing; (3) obtaining material parameters of the non-spherical test particles and controlling the air supply component to form a stable airflow field in the fluidized cavity; discharging the material from the top of the fluidized cavity and controlling two cameras to continuously capture images of the test particles as they pass through a capturing interval, thereby obtaining two groups of time series images of the test particles; (4) The signal acquisition and processing unit obtains time series data of the non-spherical test particles, wherein the time series data includes at least the position, velocity, acceleration, incident angle, angular velocity, and angular acceleration of the particles; and the aerodynamic characteristic parameters of the non-spherical test particles are calculated using the time series data, and the drag coefficient in the aerodynamic characteristic parameters of the non-spherical test particles is calculated. , lift coefficient and torque coefficient Calculate using the following formula: In the formula, , , They are drag force, lift force and torque force exerted by fluid on particles respectively; , , , They represent air density, particle density, particle volume and particle mass respectively; Represents the projected area perpendicular to the direction of motion during the particle falling process, where A 0 is the projected area of ​​the particle facing the airflow direction at the beginning of the falling process; and Represent the velocity of fluid and particles respectively; It is the angle between the fluid flow direction and the long axis direction of the particle in the measurement area, that is, the incident angle at different times; is the acceleration of the particle; , are the particle angular velocity and moment of inertia, respectively. For long cylindrical particles, the moment of inertia , is the minor semi-axis length of the particle; is the angular acceleration of the particle; It is the equivalent diameter of a spherical particle with the same volume as the particle being measured.

2. The method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow according to claim 1, characterized in that: In process (1), the air supply assembly includes a blower and an air storage tank which are connected in sequence, the bottom of the fluidizing cavity is connected to the air storage tank, and a flow meter is provided corresponding to the air storage tank; and / or, A discharge mechanism is arranged at the top of the fluidized cavity, and a particle release sensor is arranged corresponding to the discharge mechanism; the discharge mechanism is electrically connected to the signal acquisition and processing unit through the particle release sensor.

3. The method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow according to claim 1, characterized in that: The two cameras are multifunctional high-speed cameras, and their exposure time is in the range of 80µs~120µs, and the frame rate of the two cameras is controlled in the range of 2000~5000 frames / second.

4. The method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow according to any one of claims 1 to 3, characterized in that: Light sources are also provided corresponding to the two cameras to provide illumination for the shooting intervals of the two cameras.

5. The method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow according to any one of claims 1 to 3, characterized in that: In process (2), the signal acquisition and processing unit determines the posture of the particle in three-dimensional space by an 8-point method. The method includes the following steps: (2.1) performing point calibration, calibrating 8 position points on the wall surface of the shooting interval of the fluidized cavity; (2.2) Collect images of the measured area, use two cameras to capture images at different angles, and make sure that the eight points are within the field of view of the two cameras; (2.3) Using the principles of camera imaging and geometric projection, establish the correspondence between the coordinates of each 2D point in the image and its 3D coordinates in real space; (2.4) Perform spatial transformation calculations, link the two-dimensional point coordinates in the image with the real spatial coordinates through multi-view geometry calculations, and generate a three-dimensional coordinate system for analysis based on TEMA software; (2.5) The two cameras continuously capture images of the particles passing through the measured area, and the TEMA software is used to capture the movement trajectory of the particles in the three-dimensional coordinate system, and then the time series data of the particles are output.

6. The method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow according to any one of claims 1 to 3, characterized in that: The thickness of the tube body of the fluidized cavity is 0.01-0.02 m, the outer diameter of the tube body is 0.10-0.20 m, and the height of the tube body is 1.0-1.5 m; and in process (2), the shooting field of view is located at a distance of 0.6-0.9 m from the bottom of the fluidized cavity.

7. The method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow according to any one of claims 1 to 3, characterized in that: In process (3), the discharge position of the non-spherical particles to be measured is the center position of the top of the fluidization cavity; and / or, The non-spherical measuring particles are in a horizontal state when being discharged.

8. The method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow according to any one of claims 1 to 3, characterized in that: When calculating the time series data in process (4), the time series data of the non-spherical measured particles at a certain incident angle is obtained by averaging the measured data within a numerical change of the incident angle of no more than 2°.

9. The method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow according to any one of claims 1 to 3, characterized in that: The non-spherical measurement particles are long cylindrical straw hollow particles.

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