CN102944507A - Device and method for measuring drag coefficient of light special-shaped particles - Google Patents

Abstract

The invention discloses a device and method for measuring the drag coefficient of light special-shaped particles. The device disclosed herein comprises a transparent fluidization cavity, an air compressor, an air flow meter, a first image acquisition unit, a second image acquisition unit, a sheet laser source and a processing unit, wherein the supply air outlet of the air compressor is connected with the air inlet at the bottom of the transparent fluidization cavity through a pipeline, the pipeline is provided with a valve and the air flow meter, and the upper portion of the transparent fluidization cavity is provided with a feed inlet; the first image acquisition unit, the second image acquisition unit, and the sheet laser source are arranged outside the transparent fluidization cavity, the central axis of the transparent fluidization cavity is in the light path plane of the sheet laser source, and the connecting line between the first image acquisition unit and the second image acquisition unit is vertical to the light path plane of the sheet laser source; and the image output ends of the first image acquisition unit and the second image acquisition unit are connected with the image input end of the processing unit.

Description

A kind of measurement mechanism and measuring method of lightweight abnormity particle drag coefficient

Technical field

The present invention relates to a kind of measurement mechanism and measuring method of lightweight abnormity particle drag coefficient, belong to the technical field of fluidized bed and multiphase flow measurement.

Background technology

Gas-solid Two-phase Flow is a kind of common phenomena from many process industrials field such as petrochemical industry, metallurgy, cement, and the interaction mechanism of research particle and fluid helps appropriate design, scale amplification and efficiency optimization to relate to industrial system or the process device of Gas-solid Two-phase Flow.Drag coefficient is characterizing particle and fluid interaction intensity, is that announcement particle and fluid are made one of core parameter of mechanism mutually.Its numerical values recited not only is subjected to the Reynolds number effect of airflow field, but also relevant with many factors such as the characteristic of particle itself such as material, shape, size, surfacenesses.

Because the importance of drag coefficient in the gas solid-liquid flows, Chinese scholars has been carried out the work of a large amount of tests, theory and numerical simulation aspect to it at present, obtained for achievements such as the drag coefficient theoretical model of sphere or regular shape (such as disc, ellipse, bar-shaped etc.) particle or experimental formulas, and develop the technology of using sedimentation measurement rules shaped particles drag coefficient, and corresponding commercial testing apparatus is arranged.Final settlement speed when its measuring principle is at the uniform velocity moving when measuring particle and reach in liquid, the stress model of particle in liquid according at the uniform velocity moving calculates the drag coefficient of particle in static flow field.

Yet for the measurement of lightweight (density ratio water is little), abnormity (irregular shape), shaggy particle drag force number, conventional is also inapplicable as the sedimentation equipment of medium take water or oil, and its problem mainly is:

(1) density of the particle of applicable sedimentation need to be greater than the density of liquid, but for biological particles such as crops such as picture millet, stalks, they mostly have fibre structure and quality is light, thereby use gravity settling equipment need to select the fluid media (medium) that density is little and the coefficient of viscosity is high.This relatively wastes time and energy but also will further analyze, determine the Flowing characteristic parameters of this fluid media (medium).In addition, when using liquid medium, fluid can infiltrate particle surface, to such an extent as to be penetrated into granule interior, so also can change the physical property of particle itself, thereby affects the accuracy that drag force is measured;

When (2) particle falls in gas, owing to there being the behaviors such as acceleration and rotation, thereby particle also can be subject to the effects such as caused Mai Genusi (Magnus) power because Bassett (Basset) power, the particle rotation that Particle Acceleration or retarded motion produce moved except the impact that is subject to drag force, gravity, buoyancy and additional mass power.Compare with air dielectric, the coefficient of viscosity of liquid is larger, lightweight, the aerial circling behavior of special-shaped particle are difficult to reappear in liquid medium, so measure the measured value of drag coefficient ratio in liquid medium of lightweight, special-shaped particle more near the real working condition of the Gas-solid Two-phase Flow in industrial system or the equipment in air dielectric, its measured value is more accurately credible;

(3) relevant with the Reynolds number in flow field by the drag coefficient of particle, to compare with liquid flow field, the high reynolds number airflow field is more prone to realize by draught damper.

In addition, measurement for lightweight abnormity particle drag coefficient, Chinese scholars also has the method that proposes to adopt separate unit high definition high-speed camera, but this method is limit by the visual angle that is subject to the separate unit video camera, can not measure exactly special-shaped the particle angular velocity in the three-dimensional rotation process and the cross section that facings the wind in the flow field, this measuring method is also treated in further studying and improving.

Summary of the invention

The object of the present invention is to provide a kind of measuring method that is applicable to measure the device of lightweight abnormity particle drag coefficient and uses this device, to solve the measuring technique problem of settling methods and the inapplicable the type particle of separate unit High-speed Photography Technology drag coefficient.

In order to realize above purpose, technical scheme of the present invention is as follows: a kind of measurement mechanism of lightweight abnormity particle drag coefficient is characterized in that: comprise transparent fluidisation cavity, air compressor, air flowmeter, the first image acquisition unit, the second image acquisition unit, sheet shape LASER Light Source and processing unit;

The air taking port of described air compressor connects the air intake opening of transparent fluidisation cavity bottom by pipeline, be provided with valve and described air flowmeter on its pipeline, and described transparent fluidisation cavity top is provided with charge door; It is outside that described the first image acquisition unit, the second image acquisition unit and sheet shape LASER Light Source are positioned at described transparent fluidisation cavity, the axis of transparent fluidisation cavity is positioned at the light path plane of sheet shape LASER Light Source, and the line of the first image acquisition unit and the second image acquisition unit is perpendicular to sheet shape LASER Light Source light path plane;

The output end of image of described the first image acquisition unit and the second image acquisition unit links to each other with the image input end of processing unit.

More preferably scheme, described the first image acquisition unit and the second image acquisition unit all are digital cameras, and its resolution is not less than 640 * 480 pixels, sample rate is not less than 25 frame per seconds.

More preferably scheme, the thickness of described shape LASER Light Source is adjustable.

More preferably scheme, described transparent fluidisation cavity is square.

More preferably scheme, described processing unit is the computing machine of being furnished with image pick-up card.

Adopt the measuring method of the measurement mechanism of lightweight abnormity particle drag coefficient of the present invention, comprise the steps:

1), the valve opening on adjusting and the pipeline that air compressor links to each other, make the airflow field in the transparent fluidisation cavity keep stable gas speed;

2), open sheet shape LASER Light Source, open simultaneously two different image acquisition units of sample frequency, tested particle is put into transparent fluidisation cavity by charge door, the video data that image acquisition unit obtains is delivered to processing unit;

3), processor unit is by the picture that comparison two number of units word video cameras obtain, and obtains the distance, delta S of particle in two two field pictures corresponding to two number of units word video cameras _{I-i '}, i=1,2 ..., n; Then particle is through Δ S _{I-i '}Average velocity be: $u_i=\frac{{\mathrm{\ΔS}}_{i-i^{\′}}}{\mathrm{\Δt}}---(1-1);$

Wherein, Δ t is that particle is through Δ S _{I-i '}The time of this segment distance, Δ S _{I-i '}Be distance value poor of the relatively same line of reference of the corresponding pictures of two video cameras; I is picture sequence numbers;

Get the acceleration that particle falls at this segment distance of Si by formula (1-1):

Wherein, S _iIt is distance between i pictures and the i-1 pictures; t _iThat particle passes through S _iThe time of this segment distance;

(1-2) got by formula (1-1),

(i=1,2 ..., n);

Wherein, u _pBe the average velocity of particle, a _pBe the particle average acceleration;

If the long axis direction of particle and the angle theta of horizontal direction in every frame video _iObtain the difference Δ θ of the angle of the long axis direction of particle in two two field pictures corresponding to two number of units word video cameras and transverse axis by comparing picture that two number of units word video cameras obtain _{I-i '}

Then $w_i=\frac{{\mathrm{\Δ\θ}}_{i-i^{\′}}}{\mathrm{\Δt}}---(1-3);$

Get the particle mean angular velocity by formula (1-3):

4) according to the particle stress model: $\stackrel{\→}{F_g}+\stackrel{\→}{F_D}+\stackrel{\→}{F_b}+\stackrel{\→}{F_m}+\stackrel{\→}{F_B}+\stackrel{\→}{F_M}=m_p\stackrel{\→}{a_p}---\left(1\right)$

$\stackrel{\&RightArrow;}{F_g}=\frac{4}{3}{\mathrm{\&pi;<figure-callout\; id="3"\; label="r\; p"\; filenames="HDA00002335382200011.png"\; state="\{\{state\}\}">r</figure-callout>}}_p^{}{\mathrm{\&rho;}}_{p}g=m_{p}g---\left(2\right)$

$\stackrel{\&RightArrow;}{F_D}=\frac{1}{2}{C}_D{\mathrm{\&rho;}}_f{A}_{\mathrm{proj}}\left|\stackrel{\&RightArrow;}{u_r}\right|\stackrel{\&RightArrow;}{u_r}---\left(3\right)$

$\stackrel{\&RightArrow;}{F_a}=-\frac{4}{3}{\mathrm{\&pi;<figure-callout\; id="3"\; label="r\; p"\; filenames="HDA00002335382200011.png"\; state="\{\{state\}\}">r</figure-callout>}}_p^{}{\mathrm{\&rho;}}_{f}g=-V_p{\mathrm{\&rho;}}_{f}g---\left(4\right)$

$\stackrel{\&RightArrow;}{F_m}=\frac{1}{2}\left(\frac{4}{3}{\mathrm{\&pi;r}}_p^3\right){\mathrm{\&rho;}}_f\frac{d}{\mathrm{dt}}(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})=\frac{2}{3}{\mathrm{\&pi;<figure-callout\; id="3"\; label="r\; p"\; filenames="HDA00002335382200011.png"\; state="\{\{state\}\}">r</figure-callout>}}_p^{}{\mathrm{\&rho;}}_f\frac{d}{\mathrm{dt}}(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})=\frac{1}{2}{V}_p{\mathrm{\&rho;}}_f\frac{d}{\mathrm{dt}}(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})---\left(5\right)$

$\stackrel{\&RightArrow;}{F_B}={6\mathrm{<figure-callout\; id="2"\; label="r\; p"\; filenames="2012104291897100003DEST\_PATH\_IMAGE002.png"\; state="\{\{state\}\}">r</figure-callout>}}_p^{}\sqrt{{\mathrm{\&pi;\&rho;}}_f{\mathrm{\&mu;}}_f}{\&Integral;}_{t_0}^t\frac{\frac{d}{\mathrm{d\&tau;}}(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})}{\sqrt{t-\mathrm{\&tau;}}}\mathrm{d\&tau;}---\left(6\right)$

$\stackrel{\&RightArrow;}{F_M}={\mathrm{\&pi;<figure-callout\; id="3"\; label="r\; p"\; filenames="HDA00002335382200011.png"\; state="\{\{state\}\}">r</figure-callout>}}_p^{}{\mathrm{\&rho;}}_f{\mathrm{\&omega;}}_p\&times;(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})---\left(7\right)$

A _proj＝A ₀cosθ （8）

${\mathrm{\&omega;}}_p=\frac{\mathrm{d\&theta;}}{\mathrm{dt}}---\left(9\right)$

Wherein,

The acceleration of particle,

Respectively gravity, drag force, buoyancy, additional mass power, Basset power and the Magnus power of particle;

Wherein, r _pEquivalent diameter for particle; m _pQuality for individual particle; V _pVolume for individual particle;

Be the relative velocity of particle and fluid, namely

Be the speed of fluid,

Be the speed of individual particle,

For Mould; ρ _pDensity for particle; ρ _fDensity for fluid; μ _fBe the fluid shearing coefficient of viscosity; A _ProjBe the projected area of particle in face of direction of motion; A ₀Maximum secting area for particle; θ is at the major axis of measured zone particle and the mean value of the angle between the horizontal direction;

Can be regarded as to such an extent that the drag coefficient of individual particle is by formula (1) ~ (9):

More preferably scheme, two image acquisition units are triggered synchronously by processing unit, and their frame per second is set and is spaced apart 3～5 frames, to obtain the image sequence in the Millisecond time interval.

Wherein, formula 1 ~ 9 all is known technology, is not described in detail.

Compared with prior art, beneficial effect of the present invention:

(1) non-cpntact measurement, measuring process do not disturb the interaction of fluidisation cavity endoparticle and airflow field;

(2) adopt twin camera difference frequency technique for taking, can take the detailed form (translation, rotation and acceleration) that particle moves in airflow field, and the image sequence in millisecond magnitude time interval of dropping process that can obtain particle in the fluidisation cavity;

(3) this device can be measured acceleration and the angular velocity of particle in operational process, thus just can indirectly measure affect the drag coefficient measuring accuracy owing to Particle Acceleration motion and Bassett (Basset) power and Mai Genusi (Magnus) power that rotatablely move and produce;

(4) compare with the technology that settling methods is measured the particle drag coefficient, because fluid media (medium) is air, the test condition that apparatus of the present invention are simulated is more near the operating mode of actual Dual-Phrase Distribution of Gas olid system, thereby the result who measures is more accurate;

(5) with than liquid medium compare, adopt the gas flowfield medium, test convenient, easily measure the particle drag coefficient of correspondence under the high reynolds number condition.

Description of drawings

Fig. 1 is a specific embodiment system schematic of lightweight abnormity particle drag coefficient measurement mechanism of the present invention;

Wherein, fluidisation cavity 1, particle 2, industrial camera 3, sheet shape lasing light emitter 4, computing machine 7, operation valve 8, air flowmeter 9, air compressor 10.

The measuring principle schematic diagram of Fig. 2 abnormity particle average velocity and average acceleration;

Fig. 3 abnormity particle rotation angular velocity measurement principle schematic.

Embodiment

The below describes the specific embodiment of the present invention in detail with reference to Fig. 1,2 and 3.

A kind of measurement mechanism of lightweight abnormity particle drag coefficient is characterized in that: comprise transparent fluidisation cavity, air compressor, air flowmeter, the first image acquisition unit, the second image acquisition unit, sheet shape LASER Light Source and processing unit;

The air taking port of described air compressor connects the air intake opening of transparent fluidisation cavity bottom by pipeline, be provided with valve and described air flowmeter on its pipeline, and described transparent fluidisation cavity top is provided with charge door; It is outside that described the first image acquisition unit, the second image acquisition unit and sheet shape LASER Light Source are positioned at described transparent fluidisation cavity, the axis of transparent fluidisation cavity is positioned at the light path plane of sheet shape LASER Light Source, and the line of the first image acquisition unit and the second image acquisition unit is perpendicular to sheet shape LASER Light Source light path plane;

The output end of image of described the first image acquisition unit and the second image acquisition unit links to each other with the image input end of processing unit.

More preferably scheme, described the first image acquisition unit and the second image acquisition unit all are digital cameras, and its resolution is not less than 640 * 480 pixels, sample rate is not less than 25 frame per seconds.

More preferably scheme, the thickness of described shape LASER Light Source is adjustable.

More preferably scheme, described transparent fluidisation cavity is square.

More preferably scheme, described processing unit is the computing machine of being furnished with image pick-up card.

Adopt the measuring method of the measurement mechanism of lightweight abnormity particle drag coefficient of the present invention, comprise the steps:

1), the valve opening on adjusting and the pipeline that air compressor links to each other, make the airflow field in the transparent fluidisation cavity keep stable gas speed;

2), open sheet shape LASER Light Source, open simultaneously two different image acquisition units of sample frequency, tested particle is put into transparent fluidisation cavity by charge door, the video data that image acquisition unit obtains is delivered to processing unit;

3), processor unit is by the picture that comparison two number of units word video cameras obtain, and obtains the distance, delta S of particle in two two field pictures corresponding to two number of units word video cameras _{I-i '}, i=1,2 ..., n; Then particle is through Δ S _{I-i '}Average velocity be: $u_i=\frac{{\mathrm{\&Delta;S}}_{i-i^{\&prime;}}}{\mathrm{\&Delta;t}}---(1-1);$

Wherein, Δ t is that particle is through Δ S _{I-i '}The time of this segment distance, Δ S _{I-i '}Be distance value poor of the relatively same line of reference of the corresponding pictures of two video cameras; I is picture sequence numbers, and i=1 represents the first pictures;

Get particle at S by formula (1-1) _iThe acceleration that this segment distance falls:

Wherein, S _iIt is distance between i pictures and the i-1 pictures; t _iThat particle passes through S _iThe time of this segment distance;

(1-2) got by formula (1-1),

(i=1,2 ..., n);

Wherein, u _pBe the average velocity of particle, a _pBe the particle average acceleration;

If the long axis direction of particle and the angle theta of horizontal direction in every frame video _iObtain the difference Δ θ of the angle of the long axis direction of particle in two two field pictures corresponding to two number of units word video cameras and transverse axis by comparing picture that two number of units word video cameras obtain _{I-i '}

Then $w_i=\frac{{\mathrm{\&Delta;\&theta;}}_{i-i^{\&prime;}}}{\mathrm{\&Delta;t}}---(1-3);$

Get the particle mean angular velocity by formula (1-3):

4) according to the particle stress model: $\stackrel{\&RightArrow;}{F_g}+\stackrel{\&RightArrow;}{F_D}+\stackrel{\&RightArrow;}{F_b}+\stackrel{\&RightArrow;}{F_m}+\stackrel{\&RightArrow;}{F_B}+\stackrel{\&RightArrow;}{F_M}=m_p\stackrel{\&RightArrow;}{a_p}---\left(1\right)$

$\stackrel{\&RightArrow;}{F_g}=\frac{4}{3}{\mathrm{\&pi;<figure-callout\; id="3"\; label="r\; p"\; filenames="HDA00002335382200011.png"\; state="\{\{state\}\}">r</figure-callout>}}_p^{}{\mathrm{\&rho;}}_{p}g=m_{p}g---\left(2\right)$

$\stackrel{\&RightArrow;}{F_D}=\frac{1}{2}{C}_D{\mathrm{\&rho;}}_f{A}_{\mathrm{proj}}\left|\stackrel{\&RightArrow;}{u_r}\right|\stackrel{\&RightArrow;}{u_r}---\left(3\right)$

$\stackrel{\&RightArrow;}{F_a}=-\frac{4}{3}{\mathrm{\&pi;<figure-callout\; id="3"\; label="r\; p"\; filenames="HDA00002335382200011.png"\; state="\{\{state\}\}">r</figure-callout>}}_p^{}{\mathrm{\&rho;}}_{f}g=-V_p{\mathrm{\&rho;}}_{f}g---\left(4\right)$

$\stackrel{\&RightArrow;}{F_m}=\frac{1}{2}\left(\frac{4}{3}{\mathrm{\&pi;r}}_p^3\right){\mathrm{\&rho;}}_f\frac{d}{\mathrm{dt}}(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})=\frac{2}{3}{\mathrm{\&pi;<figure-callout\; id="3"\; label="r\; p"\; filenames="HDA00002335382200011.png"\; state="\{\{state\}\}">r</figure-callout>}}_p^{}{\mathrm{\&rho;}}_f\frac{d}{\mathrm{dt}}(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})=\frac{1}{2}{V}_p{\mathrm{\&rho;}}_f\frac{d}{\mathrm{dt}}(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})---\left(5\right)$

$\stackrel{\&RightArrow;}{F_B}={6\mathrm{<figure-callout\; id="2"\; label="r\; p"\; filenames="2012104291897100003DEST\_PATH\_IMAGE002.png"\; state="\{\{state\}\}">r</figure-callout>}}_p^{}\sqrt{{\mathrm{\&pi;\&rho;}}_f{\mathrm{\&mu;}}_f}{\&Integral;}_{t_0}^t\frac{\frac{d}{\mathrm{d\&tau;}}(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})}{\sqrt{t-\mathrm{\&tau;}}}\mathrm{d\&tau;}---\left(6\right)$

$\stackrel{\&RightArrow;}{F_M}={\mathrm{\&pi;<figure-callout\; id="3"\; label="r\; p"\; filenames="HDA00002335382200011.png"\; state="\{\{state\}\}">r</figure-callout>}}_p^{}{\mathrm{\&rho;}}_f{\mathrm{\&omega;}}_p\&times;(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})---\left(7\right)$

A _proj=A ₀cosθ （8）

${\mathrm{\&omega;}}_p=\frac{\mathrm{d\&theta;}}{\mathrm{dt}}---\left(9\right)$

Wherein,

The acceleration of particle,

Respectively gravity, drag force, buoyancy, additional mass power, Basset power and the Magnus power of particle;

Wherein, r _pEquivalent diameter for particle; m _pQuality for individual particle; V _pVolume for individual particle;

Be the relative velocity of particle and fluid, namely

Be the speed of fluid,

Be the speed of individual particle,

For

Mould; ρ _pDensity for particle; ρ _fDensity for fluid; μ _fBe the fluid shearing coefficient of viscosity; A _ProjBe the projected area of particle in face of direction of motion; A ₀Maximum secting area for particle; θ is at the major axis of measured zone particle and the mean value of the angle between the horizontal direction;

Can be regarded as to such an extent that the drag coefficient of individual particle is by formula (1) ~ (9):

More preferably scheme, two image acquisition units are triggered synchronously by processing unit, and their frame per second is set and is spaced apart 3～5 frames, to obtain the image sequence in the Millisecond time interval.

The present invention is just for the existing problem of the assay method of existing particle drag coefficient, propose to use the digital camera of two different frame per second, use the difference frequency technique for taking, record simultaneously the process that lightweight, special-shaped particle are moved in airflow field, can obtain the sequence of video images in the Millisecond time interval.By the method that image is processed, measure shift position and the anglec of rotation of particle in airflow field, calculate translational velocity, translatory acceleration and the angular velocity of rotation of particle.Then according to the force bearing formulae of particle in airflow field, calculate the drag coefficient of particle.

Target of the present invention is achieved in that in Dual-Phrase Distribution of Gas olid, and the drag force of particle in fluid is the citation form of particle and fluid interphase interaction, when particle speed is different from fluid velocity, will produce interaction force between particle and the fluid.To a fast side, the side's that the speed that is subject to is low resistance; A side low to speed will be subject to a fast side's drag force.Resistance and drag force equal and opposite in direction, opposite direction.Usually fluid velocity is greater than particle speed, is the drag force of fluid to such an extent as to particle is subject to.The drag coefficient of particle is that fluid acts on drag force on the particle to the projected area of particle on its direction of motion and the ratio of hydrodynamic pressure product, and the factor that affects the particle drag coefficient has: the factors such as particle Reynolds number, form factor, front face area, surfaceness and wall impact.Measurement parameter corresponding to influence factor comprises: particle translational velocity, particle translatory acceleration, particle long axis direction and horizontal direction angle, particle angular velocity and front face area.Adopt gas medium, the liquid mediums such as oil, water are more near the realization operating mode in the Dual-Phrase Distribution of Gas olid system or equipment relatively.

In order to realize target of the present invention: made up and comprise video acquisition, Video processing and the assisted parts measurement mechanism that grades: wherein the video acquisition part is comprised of two number of units word video cameras, computing machine and a sheet shape LASER Light Source, by twin camera difference frequency technique for taking, the running status of record particle; The machine video processing part is a computing machine of being furnished with image pick-up card, the Applied Digital image processing techniques is processed the video that obtains, analysing particulates is the position on every two field picture, major axis footpath and the angle of horizontal direction and the time interval of frame and interframe in video, calculate the endocorpuscular average area of section that facings the wind of translational velocity, translatory acceleration, angular velocity of rotation and swing circle of particle, so just can calculate according to the gas-solid rolling particles force bearing formulae drag coefficient of tested particle; Measure slave part and comprise that transparent square fluidisation cavity, draught damper, flow take into account each one of air compressor.By changing the aperture of valve, can regulate the gas pushing quantity by air compressor during measurement, thereby regulate the speed of airflow field in the fluidisation cavity, total airshed is measured by air flowmeter.

Concrete implementation step is:

1, container is adjusted to plumbness, choose zone to be measured, the vertical height L of measured zone is 1.2m greater than the height of 0.5m(container), particle whereabouts initial position should be avoided the impact of wall and import during measurement, the frame per second of setting two number of units word video cameras is respectively 30fps, 27fps, adjust the height of two number of units word video cameras and the position of laser instrument, make digital camera and laser alignment measured zone, measured zone is the light path plane lap by the coverage of camera and sheet shape LASER Light Source, the axis of transparent fluidisation cavity is positioned at the measured zone plane, the upper end of measured zone is apart from fluidisation cavity open upper end 5cm, make simultaneously two number of units word video cameras at the same level height, relatively be placed in the centre of measured zone.

2, the usage data transmission line is connected two number of units word camera review output terminals with the image pick-up card input end, computing machine and digital camera power on successively, use the supporting video acquisition software of image pick-up card, with individual particle from the feed location free-falling, make the maximum cross-section of particle in face of the direction of particle whereabouts, observe the image effect of taking, adjust the position of digital camera and laser instrument, make Ear Mucosa Treated by He Ne Laser Irradiation arrive measured zone, make particle drop on the middle part of picture.

3, be ready to working condition to be measured after, begin to take the flow field video, click and to begin to measure, then two number of units word video camera synchronous workings put down particle in feed location, record the movement of particles video and preserve.The single shot time decides on single-frame images resolution, image acquisition speed, calculator memory size, guarantees that the video size of single shot is no more than the calculator memory available size.

The above only is better embodiment of the present invention; protection scope of the present invention is not limited with above-mentioned embodiment; as long as the equivalence that those of ordinary skills do according to disclosed content is modified or changed, all should include in the protection domain of putting down in writing in claims.

Claims (7)

1. the measurement mechanism of a lightweight abnormity particle drag coefficient is characterized in that: comprise transparent fluidisation cavity, air compressor, air flowmeter, the first image acquisition unit, the second image acquisition unit, sheet shape LASER Light Source and processing unit;

The air taking port of described air compressor connects the air intake opening of transparent fluidisation cavity bottom by pipeline, be provided with valve and described air flowmeter on its pipeline, and described transparent fluidisation cavity top is provided with charge door; It is outside that described the first image acquisition unit, the second image acquisition unit and sheet shape LASER Light Source are positioned at described transparent fluidisation cavity, the axis of transparent fluidisation cavity is positioned at the light path plane of sheet shape LASER Light Source, and the line of the first image acquisition unit and the second image acquisition unit is perpendicular to sheet shape LASER Light Source light path plane;

The output end of image of described the first image acquisition unit and the second image acquisition unit links to each other with the image input end of processing unit.

2. the measurement mechanism of lightweight according to claim 1 abnormity particle drag coefficient, it is characterized in that, described the first image acquisition unit and the second image acquisition unit all are digital cameras, and its resolution is not less than 640 * 480 pixels, sample rate is not less than 25 frame per seconds.

3. the measurement mechanism of lightweight abnormity particle drag coefficient according to claim 1 is characterized in that the thickness of described shape LASER Light Source is adjustable.

4. the measurement mechanism of lightweight abnormity particle drag coefficient according to claim 1 is characterized in that described transparent fluidisation cavity is square.

5. the measurement mechanism of lightweight abnormity particle drag coefficient according to claim 1 is characterized in that described processing unit is the computing machine of being furnished with image pick-up card.

6. the measuring method of the measurement mechanism of a lightweight abnormity particle drag coefficient as claimed in claim 1 is characterized in that, comprises the steps:

1), the valve opening on adjusting and the pipeline that air compressor links to each other, make the airflow field in the transparent fluidisation cavity keep stable gas speed;

2), open sheet shape LASER Light Source, open simultaneously two different image acquisition units of sample frequency, tested particle is put into transparent fluidisation cavity by charge door, the video data that image acquisition unit obtains is delivered to processing unit;

3), processor unit is by the picture that comparison two number of units word video cameras obtain, and obtains the distance, delta S of particle in two two field pictures corresponding to two number of units word video cameras _{I-i '}, i=1,2 ..., n; Then particle is through Δ S _{I-i '}Average velocity be: $u_i=\frac{{\mathrm{\&Delta;S}}_{i-i^{\&prime;}}}{\mathrm{\&Delta;t}}---(1-1);$

Wherein, Δ t is that particle is through Δ S _{I-i '}The time of this segment distance, Δ S _{I-i '}Be distance value poor of the relatively same line of reference of the corresponding pictures of two video cameras; I is picture sequence numbers;

Get particle at S by formula (1-1) _iThe acceleration that this segment distance falls:

Wherein, S _iIt is distance between i pictures and the i-1 pictures; t _iThat particle passes through S _iThe time of this segment distance;

(1-2) got by formula (1-1),

(i=1,2 ..., n);

Wherein, u _pBe the average velocity of particle, a _pBe the particle average acceleration;

If the long axis direction of particle and the angle theta of horizontal direction in every frame video _iObtain the difference Δ θ of the angle of the long axis direction of particle in two two field pictures corresponding to two number of units word video cameras and transverse axis by comparing picture that two number of units word video cameras obtain _{I-i '}

Then $w_i=\frac{{\mathrm{\&Delta;\&theta;}}_{i-i^{\&prime;}}}{\mathrm{\&Delta;t}}---(1-3);$

Get the particle mean angular velocity by formula (1-3):

4) according to the particle stress model: $\stackrel{\&RightArrow;}{F_g}+\stackrel{\&RightArrow;}{F_D}+\stackrel{\&RightArrow;}{F_b}+\stackrel{\&RightArrow;}{F_m}+\stackrel{\&RightArrow;}{F_B}+\stackrel{\&RightArrow;}{F_M}=m_p\stackrel{\&RightArrow;}{a_p}---\left(1\right)$

$\stackrel{\&RightArrow;}{F_g}=\frac{4}{3}{\mathrm{\&pi;r}}_p^3{\mathrm{\&rho;}}_{p}g=m_{p}g---\left(2\right)$

$\stackrel{\&RightArrow;}{F_D}=\frac{1}{2}{C}_D{\mathrm{\&rho;}}_f{A}_{\mathrm{proj}}\left|\stackrel{\&RightArrow;}{u_r}\right|\stackrel{\&RightArrow;}{u_r}---\left(3\right)$

$\stackrel{\&RightArrow;}{F_a}=-\frac{4}{3}{\mathrm{\&pi;r}}_p^3{\mathrm{\&rho;}}_{f}g=-V_p{\mathrm{\&rho;}}_{f}g---\left(4\right)$

$\stackrel{\&RightArrow;}{F_m}=\frac{1}{2}\left(\frac{4}{3}{\mathrm{\&pi;r}}_p^3\right){\mathrm{\&rho;}}_f\frac{d}{\mathrm{dt}}(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})=\frac{2}{3}{\mathrm{\&pi;r}}_p^3{\mathrm{\&rho;}}_f\frac{d}{\mathrm{dt}}(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})=\frac{1}{2}{V}_p{\mathrm{\&rho;}}_f\frac{d}{\mathrm{dt}}(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})---\left(5\right)$

$\stackrel{\&RightArrow;}{F_B}={6r}_p^2\sqrt{{\mathrm{\&pi;\&rho;}}_f{\mathrm{\&mu;}}_f}{\&Integral;}_{t_0}^t\frac{\frac{d}{\mathrm{d\&tau;}}(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})}{\sqrt{t-\mathrm{\&tau;}}}\mathrm{d\&tau;}---\left(6\right)$

$\stackrel{\&RightArrow;}{F_M}={\mathrm{\&pi;r}}_p^3{\mathrm{\&rho;}}_f{\mathrm{\&omega;}}_p\&times;(\stackrel{\&RightArrow;}{u}-\stackrel{\&RightArrow;}{v})---\left(7\right)$

A _proj＝A ₀cosθ （8）

${\mathrm{\&omega;}}_p=\frac{\mathrm{d\&theta;}}{\mathrm{dt}}---\left(9\right)$

Wherein, The acceleration of particle,

Respectively gravity, drag force, buoyancy, additional mass power, Basset power and the Magnus power of particle;

Wherein, r _pEquivalent diameter for particle; m _pQuality for individual particle; V _pVolume for individual particle;

Be the relative velocity of particle and fluid, namely

Be the speed of fluid,

Be the speed of individual particle,

For

Mould; ρ _pDensity for particle; ρ _fDensity for fluid; μ _fBe the fluid shearing coefficient of viscosity; A _ProjBe the projected area of particle in face of direction of motion; A ₀Maximum secting area for particle; θ is at the major axis of measured zone particle and the mean value of the angle between the horizontal direction;

Can be regarded as to such an extent that the drag coefficient of individual particle is by formula (1) ~ (9):

7. the measuring method of lightweight abnormity particle drag coefficient measurement mechanism according to claim 6 is characterized in that, two image acquisition units are triggered synchronously by processing unit, and their frame per second is spaced apart 3～5 frames.

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