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

Abstract

The present invention discloses a method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow, belonging to the field of aerodynamic measurement technology. By constructing a measurement system with a fluidization cavity and an image acquisition component, utilizing the integrated setting of two cameras and a signal acquisition and processing unit equipped with TEMA software in the measurement system, and combining it with the optimal design of a calculation formula for aerodynamic characteristic parameters, the aerodynamic characteristic parameters of non-spherical particles can be accurately calculated by obtaining time series data of non-spherical particles in gas-solid two-phase flow. The method of the present invention can fully consider the drag and lift generated by the shape and orientation of non-spherical particles in translational motion and the torque generated in rotational motion, accurately calculate the aerodynamic characteristic parameters of non-spherical particles, provide conditions for simulating the motion trajectory of non-spherical particles in gas-solid two-phase flow, and further provide a theoretical basis for the aerodynamic design of biomass material particles when mixed and burned in coal-fired boilers.

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 into coal-fired units has become an effective way to reduce greenhouse gas emissions and rationally utilize biomass waste.

[0003] In practice, biomass materials are often crushed into pellets. Crushed biomass pellets, especially straw pellets, are highly non-spherical, often appearing as elongated cylinders. This specific shape leads to significant differences in the aerodynamic behavior of biomass pellets compared to conventional spherical coal pulverized 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 motion 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 existing technology, 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. 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 in the prior art, the present invention provides a method for measuring the 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:

[0008] (1) Construct a measurement system including a fluidized cavity and an image acquisition component;

[0009] The fluidization 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 assembly; the image acquisition assembly includes two cameras and a signal acquisition and processing unit respectively connected to the two cameras, and the signal acquisition and processing unit is configured with TEMA software for calculating time series data of the test particles by receiving two sets of images continuously captured by the two cameras;

[0010] (2) Determine the shooting interval on the wall of the fluidized cavity and mark multiple points on the wall of the shooting interval; adjust the shooting field of view of the two cameras so that the shooting field of view of the two cameras can cover all points and keep the image magnification ratio consistent after focusing;

[0011] (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 sets of time series images of the test particles;

[0012] (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 Calculated using the following formula:

[0013]

[0014]

[0015]

[0016] Where, 、 、 are the drag force, lift force and torque force exerted by the fluid on the particle 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; The angle between the incoming 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; 、 They are the particle angular velocity and moment of inertia, respectively. For long cylindrical particles, the moment of inertia , is the semi-minor 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.

[0017] As a further improvement of the present invention, in process (1), the air supply assembly includes a blower and an air storage tank that 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;

[0018] and / or,

[0019] A discharge mechanism is provided at the top of the fluidized cavity, and a particle release sensor is provided corresponding to the discharge mechanism; the discharge mechanism is electrically connected to the signal acquisition and processing unit through the particle release sensor.

[0020] As a further improvement of the present invention, the two cameras are multifunctional high-speed cameras, the exposure time of which is within the range of 80µs to 120µs, and the frame rate of the two cameras is controlled within the range of 2000 to 5000 frames per second.

[0021] 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.

[0022] As a further improvement of the present invention, in process (2), the signal acquisition and processing unit determines the posture of the particle in three-dimensional space by an 8-point method, which includes the following process:

[0023] (2.1) performing point calibration, calibrating 8 position points on the wall surface of the shooting interval of the fluid cavity;

[0024] (2.2) Capture images of the measured area using two cameras, capturing images from different angles, and ensuring that all eight locations are within the field of view of the two cameras.

[0025] (2.3) Using camera imaging principles and geometric projection principles, establish a correspondence between the coordinates of each 2D point in the image and its 3D coordinates in real space;

[0026] (2.4) Perform spatial transformation calculations to 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;

[0027] (2.5) Two cameras are used to continuously capture images of the particles passing through the measured area, and TEMA software is used to capture the motion trajectory of the particles in the three-dimensional coordinate system, and then the time series data of the particles are output.

[0028] 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 position 0.6-0.9 m away from the bottom of the fluidized cavity.

[0029] 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;

[0030] and / or,

[0031] The non-spherical measuring particles are in a horizontal state when being discharged.

[0032] 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 measurement particles at a certain incident angle are obtained by averaging the measured data whose incident angle values ​​do not exceed 2°.

[0033] As a further improvement of the present invention, the non-spherical measurement particles are long cylindrical straw hollow particles.

[0034] The above-mentioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0035] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0036] (1) The method of 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 cavity 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. By obtaining the time series data of non-spherical particles in gas-solid two-phase flow, the aerodynamic characteristic parameters of non-spherical particles can be accurately calculated. The method fully considers the translational motion and rotational motion of non-spherical particles when moving in the airflow field, greatly improves the acquisition accuracy of non-spherical particle motion data, provides a basis for accurately simulating the motion trajectory of non-spherical particles, and promotes the research and application of non-spherical particles.

[0037] (2) The method of measuring the 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 the experimental data acquisition and further improving the measurement accuracy of the measurement method.

[0038] (3) The method of measuring the 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 and burned in coal-fired boilers. It has good practical value and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. 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 creative work.

[0040] Figure 1 is a flow chart of a method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow according to an embodiment of the present invention;

[0041] 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 according to an embodiment of the present invention;

[0042] In all the drawings, the same reference numerals represent the same technical features, specifically:

[0043] 1. Blower; 2. Flow meter; 3. Gas storage tank; 4. Fluidizing 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

[0044] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate 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 may be combined with each other as long as they do not conflict with each other.

[0045] 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 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 device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0046] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0047] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0048] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0049] Example:

[0050] 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 they are moving in gas-solid two-phase flow, and complete the acquisition of some dynamic parameters based on the relevant processing of TEMA software, and then complete the calculation of the drag coefficient, lift coefficient and / or torque coefficient of non-spherical particles in gas-solid two-phase flow, providing a theoretical basis for the co-firing of non-spherical biomass fuel particles in coal-fired boilers.

[0051] It should be noted that the "TEMA software" used in the preferred embodiment of the present invention is fully called "TEMA Advanced Motion Analysis Tool", which is an advanced motion analysis tool developed by Image Systems AB of Sweden. 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 data information such as position, speed, acceleration, incident angle, angular velocity, and angular acceleration.

[0052] Specifically, if Figure 1 As shown in , a method for measuring aerodynamic characteristic parameters of non-spherical particles in gas-solid two-phase flow in a preferred embodiment preferably includes the following process:

[0053] (1) Constructing a measurement system, which includes a fluidizing cavity 4, a discharge mechanism 6, and an image acquisition component;

[0054] The fluidizing cavity 4 is a vertically arranged, tubular structure made of a transparent material. It is open at the top and connected to an air supply assembly at the bottom. This assembly creates an airflow field within the fluidizing cavity 4 for testing. In a preferred embodiment, the air supply assembly includes a blower 1 and an air tank 3, which are connected in sequence. The bottom of the fluidizing cavity 4 is connected to one end of the air tank 3. A flow meter 2 is provided corresponding to the air tank 3 to monitor the gas flow in the tank 3.

[0055] By combining the blower 1, the gas storage tank 3 and the flow meter 2, a required airflow field can be formed in the fluidizing cavity 4, thereby simulating the working environment of non-spherical biomass particles in actual application scenarios.

[0056] In actual settings, the fluidized cavity 4 is set to a circular tubular structure in order 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.

[0057] More preferably, in an actual setup, the fluidizing cavity 4 is made of transparent acrylic, 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 for the particle image is preferably located 0.6-0.9 m from the bottom of the fluidizing cavity 4. This location is chosen for capturing particle images because, after a period of falling after discharge, the particle state in the image more closely resembles that of real particles. Furthermore, the gas within the cavity can fully develop into turbulence, effectively preventing the potential turbulence at the gas inlet from affecting the measurement results.

[0058] Furthermore, the discharge mechanism 6 is arranged at the top opening of the fluidization 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 fluidization cavity 4, that is, Figure 2 The first camera 8 and the second camera 9 shown in the figure capture the non-spherical particles in the fluidization cavity 4 from different angles. Preferably, the cameras are multifunctional high-speed cameras with a maximum frame rate of no less than 2000 frames per second and a minimum exposure time of no less than 1 μs. Specifically, the exposure time of the two cameras is within the range of 3.9 μs to 1 second, and the frame rate of the two cameras is controlled within the range of 0 to 200,000 frames per second.

[0059] 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.

[0060] In actual setup, exposure time and frame rate are crucial parameters for high-speed cameras. Excessively long exposure times can easily produce smearing, affecting experimental results. Too short exposure times can result in dimmed images, blurring the contrast between particles and background, and increasing the difficulty of image processing. If the frame rate is set too low, too few images are recorded in the measurement area, making it difficult to guarantee the accuracy of experimental results. If the frame rate is set too high, too many images are recorded, increasing the workload for subsequent image processing. Therefore, in a preferred embodiment, the exposure time of both cameras is preferably set between 80µs and 120µs, and the frame rate of both cameras is preferably controlled between 2000 and 5000 frames per second.

[0061] 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 provided on the side of the fluidization cavity 4 away from the two cameras to provide sufficient illumination for the measured area.

[0062] In specific settings, the two cameras may share one light source 5 , or separate light sources 5 may be provided for the two cameras, which will not be elaborated here.

[0063] In addition, the signal acquisition and processing unit 10 in the preferred embodiment is equipped with TEMA software, which can calculate the time series data of the test particles by receiving two sets of images continuously acquired by two cameras.

[0064] 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, which can accurately realize the discharge control process of the discharge mechanism 6 and clarify the initial time of discharge.

[0065] (2) Preparing for the experiment, determine the shooting interval on the wall of the fluidized cavity 4 and mark multiple points on the wall of the shooting interval; then adjust the shooting field of view of the two cameras so that the shooting field of view of the two cameras can cover all points and keep the image magnification ratio consistent after focusing;

[0066] 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.

[0067] In more detail, in a preferred embodiment, eight marking points are selected for the shooting field of view, and the eight-point method of TEMA software is used to determine the posture of the particles in three-dimensional space. The method preferably includes the following steps:

[0068] (2.1) Perform point calibration and calibrate 8 known position points in the measured area of ​​the particle fluidization cavity;

[0069] (2.2) Capture images of the measured area using two cameras, capturing images from different angles, and ensuring that all eight locations are within the field of view of the two cameras.

[0070] (2.3) Using camera imaging principles and geometric projection principles, establish a correspondence between the coordinates of each 2D point in the image and its 3D coordinates in real space;

[0071] (2.4) Perform spatial transformation calculations to 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;

[0072] (2.5) Two cameras are used to continuously capture images of the particles passing through the measured area, and TEMA software is used to capture the motion trajectory of the particles in the three-dimensional coordinate system, and then the time series data of the particles are output.

[0073] 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.

[0074] Due to the special characteristics of non-spherical particles, maintaining a falling motion at an ideal angle of incidence is difficult in actual measurements. Therefore, in actual calculations, it is necessary to ensure that the particles maintain a stable falling trend within the calculation interval (the motion process at a specific angle of incidence). In this case, the change in the particle angle of incidence within this interval must not exceed 2°. By averaging the data within the interval that meets these conditions, we can obtain time series data for the measured particles at a specific angle of incidence.

[0075] (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;

[0076] 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 .

[0077] (4) The aerodynamic characteristic parameters of the non-spherical particles are calculated 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 moving in the gas-solid two-phase flow. The calculation process is as follows:

[0078] (4.1) Based on the average acceleration of the particle under test at the average angle of incidence, calculate the drag and lift forces acting on the particle during translational motion. The calculation process is as follows:

[0079]

[0080]

[0081] Where, 、 、 are the drag force, lift force and resultant force acting on the particle during 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; The angle between the incoming 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;

[0082] (4.2) Calculate the torque force on the measured particle during rotational motion. The calculation process is as follows:

[0083]

[0084] Where, 、 and are the particle angular velocity, moment of inertia, and torque 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 semi-minor axis length of the particle;

[0085] (4.3) The drag, lift, and torque acting on the particle are dimensionless, and the aerodynamic parameters of the particle are calculated. Combining the formulas in (4.1) and (4.2), the drag coefficient in the aerodynamic parameters of the non-spherical particle is , lift coefficient and torque coefficient The calculation process is as follows:

[0086]

[0087]

[0088]

[0089] Where, It is the equivalent diameter of a spherical particle with the same volume as the particle being measured.

[0090] As follows, the method in the preferred embodiment of the present invention is further verified and explained through a specific example.

[0091] In this specific embodiment, the aerodynamic characteristic parameter test of the particle to be tested is first completed using 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 in the experiment are cross-validated with the OpenFOAM direct numerical simulation results.

[0092] In detail, the experimental process in this specific embodiment is as follows:

[0093] (1) Reference Figure 2 Use the setup form in to build a measurement system for non-spherical particles and select the particles to be measured;

[0094] In this embodiment, the particles to be tested are long cylindrical straw hollow particles with a semi-major axis length of b is 0.02m, the bottom radius (semi-minor axis length) is 0.002m, and the aspect ratio =10, and the volume of cylindrical straw biomass pellets is calculated using the cylinder volume calculation formula. 5.026×10 -7 m 3 .

[0095] 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 calculated density of the particles is 159.15 kg / m 3 .

[0096] It should be noted that since the particles to be tested are crushed particles of biomass mixed with combustion in industrial coal-fired boilers, there will be certain differences in density between different particles of the same type of biomass. Therefore, it is necessary to screen the experimental particles, remove particles with large density differences, and take the average density of the selected particles.

[0097] (2) In this example, blower 1 is a Roots blower. Adjust the flow setting of flowmeter 2 to set the air 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. The density of the air is 1.184 kg / m 3 , the dynamic viscosity of air is 1.849×10 -5 Pa•s.

[0098] In actual operation, the air velocity is measured by a flow meter to measure the air flow in the fluidizing cavity. Given the circular cross-sectional area of ​​the fluidizing cavity 4 (the inner diameter of the cross section is 0.12m), the air velocity is calculated using the formula: is 1.023m / s, where is the air flow rate in the fluidization cavity, which is 41.67Nm 3 / h; The circular area under the cavity cross section is 0.0113m 2 .

[0099] (3) Turn on the light source and release the particles to be tested through the discharge mechanism 6 at the center of the top of the cylindrical fluidized cavity 4. Use two multifunctional high-speed cameras to capture the time series images of the particles to be tested in the measured area (the measurement interval is located at a height of 0.7m~0.8m from the bottom of the fluidized cavity 4).

[0100] (4) The control signal acquisition and processing unit 10 receives and processes the images taken by the two cameras. After image processing and Tema motion analysis software processing, the incident angle of the particle can be obtained. When the temperature is 68℃, the average total velocity of the particles in three dimensions is 1.991 m / s, and the average total 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's fall is 1.826×10 -4 m 2 .

[0101] 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 .

[0102] Based on these data, the drag coefficient is calculated to be 1.5687, the lift coefficient is calculated to be 0.5329, and the torque coefficient is calculated to be 0.5449 using the formula (4.3) in the preferred embodiment.

[0103] (5) Verify the results;

[0104] The experimentally calculated drag, lift, and torque coefficients were compared with direct simulations using the body-fitting mesh method in the fluid dynamics software OpenFOAM. OpenFOAM uses the icoFoam solver within the finite volume method to directly simulate the fluid forces acting on long cylindrical particles. Standard aerodynamic theory was then used to calculate the theoretical values ​​of the aerodynamic parameters of the particles under the same experimental conditions, which were then compared with the measured values.

[0105] 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%.

[0106] Comparison shows that the measurement method designed in the preferred embodiment of the present invention closely matches the theoretical calculation results from direct numerical simulation, with errors within a reasonable range (no more than 5%). This demonstrates that the designed measurement system and method can accurately measure the aerodynamic parameters (drag coefficient, lift coefficient, and torque coefficient) of non-spherical particles.

[0107] 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 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 co-combustion in coal-fired boilers. It has good practical value and application prospects.

[0108] It will be easily understood by those skilled in the art that the above description is merely 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 scope of protection 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 fluidized cavity and an image acquisition component; The fluidization 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 assembly; the image acquisition assembly includes two cameras and a signal acquisition and processing unit respectively connected to the two cameras, and the signal acquisition and processing unit is configured with TEMA software for calculating time series data of the test particles by receiving two sets of images continuously captured by the two cameras; (2) Determine the shooting interval on the wall of the fluidized cavity and mark multiple points on the wall of the shooting interval; adjust the shooting field of view of the two cameras so that the shooting field of view of the two cameras can cover all 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 and controlling two cameras to continuously capture images of the test particles as they pass through a capturing interval, thereby obtaining two sets 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 Calculated using the following formula: Where, 、 、 are the drag force, lift force and torque force exerted by the fluid on the particle 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; The angle between the incoming 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; 、 They are the particle angular velocity and moment of inertia, respectively. For long cylindrical particles, the moment of inertia , is the semi-minor 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 provided at the top of the fluidized cavity, and a particle release sensor is provided 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 with exposure times ranging from 80µs to 120µs, and the frame rates of the two cameras are controlled within the range of 2000 to 5000 frames per 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 lighting 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 using the 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) Capture images of the measured area using two cameras, capturing images from different angles, and ensuring that all eight locations are within the field of view of the two cameras. (2.3) Using camera imaging principles and geometric projection principles, establish a correspondence between the coordinates of each 2D point in the image and its 3D coordinates in real space; (2.4) Perform spatial transformation calculations to 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) Two cameras are used to continuously capture images of the particles passing through the measured area, and TEMA software is used to capture the motion 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 fluidized cavity tube is 0.01-0.02 m, the outer diameter of the tube is 0.10-0.20 m, and the height of the tube is 1.0-1.5 m; and in process (2), the shooting field of view is located at a position 0.6-0.9 m away 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 is the center 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 measurement particles at a certain incident angle are obtained by averaging the measured data within a numerical variation 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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