CN102590054B - Method and device for measuring particle size distribution of discrete-state particles - Google Patents

Abstract

The invention discloses a method and device for measuring particle size distribution of discrete-state particles. The method comprises the following steps of: firstly, arranging a sound field of a departure plane standing-wave sound wave or a traveling plane wave; generating transverse vibration by a discrete-state particle system under the action of sound wave, photographing transverse motion trails of the particle system continuously, and recording images sequentially; calculating an amplitude value x of a particle in the sound field within the time t, obtaining an actual vibration curve of the particle, comparing the actual vibration curve with a vibration curve of the particles with different particle diameters in the sound field under the condition of theoretical calculation, taking the particle diameter with the highest curve approximation degree as the particle diameter of the particle until the particle diameters of all the particles in the particle system are determined completely, and obtaining the particle size distribution of the particle system. According to the method disclosed by the invention, a particle size measurement lower limit which is lower than that obtained by the adoption of an optical image method can be obtained, complete non-contact measurement is realized, the measuring accuracy and the automation degree are high, and fast and accurate measurement can be carried out.

Description

A kind of measuring method of discrete state particle size distribution and device

Technical field

The present invention relates to grain diameter measuring technique, relate in particular to measuring method and the device of particle size distribution under a kind of discrete state.

Background technology

Granule size and concentration to disperse state particle are measured, and have widespread use background relating in the fields such as the power of diphasic flow, chemical industry, medicine, environmental protection, water conservancy, material.Existing measuring method comprises sieve method, microscopic method, holography, electro-induction method, sedimentation etc., and its ultimate principle is particle diameter and the shape characteristic that conversion that the optical imagery based on particle carries out imaging and enlargement ratio obtains particle.

Traditional measuring method has the defect of following aspect:

1,, when sieve method is measured, need measurement mechanism directly to contact with testing sample; When electro-induction method is measured, sample need to be suspended in electrolytic solution and measure; When sedimentation is measured, particulate samples need to be suspended in liquid medium.Above three kinds of measuring methods are in measuring process, and the medium using in surveying instrument or measurement can directly contact with discrete particle, may change the pattern of particle, affects the accuracy of measurement data.

2,, when optical microscopy and holography are measured, obtain outward appearance and the size of material to be checked by optical imagery and laser holographic interference image.But during for particle sizing, the especially measurement of suspended particle in medium, higher for measurement requirement, and also holographic interferometry is from device to the equal more complicated of image processing process; Microscope and optical imagery method are measured needs directly to observe complete granule-morphology, therefore the micro-amplification of surveying instrument is had relatively high expectations, when the particle diameter of discrete particle hour, directly observation and comparison difficulty, although the theory of optical microscope observation lower limit can arrive 0.5 micron, but under actual conditions, in the time that particle diameter is below 1 micron, optical microscope cannot observe directly in fact substantially.

3, in addition, while utilizing optical microscopy and holography to measure, although do not need to detect by an unaided eye, but directly to particle imaging because needs obtain shape characteristic, higher to imaging requirements, institute is during for particle kinetic measurement, observation and comparison difficulty accurately, the probability that occurs erroneous judgement is larger, often can not obtain good measurement result.

4, existing various observation procedure, under observation needs a large amount of manual operations, and automaticity is low.

Summary of the invention

Technical matters to be solved by this invention has been to provide a kind of can carry out non-cpntact measurement and measure the particle diameter of particle being less than 1 micron to the particle size distribution of discrete state, without measuring method and the device dynamic particle accurately observed, automaticity is higher.

The present invention is achieved by the following technical solutions:

A measuring method for discrete state particle size distribution, is characterized in that:

The first step, the sound field of arranging a plane of departure standing wave sound wave or travelling plane wave, sound direction of wave travel is horizontal direction;

Second step, the particle of discrete state ties up under self gravitation or External Force Acting to fall, enter sound field from sound field top, and occurred level transverse vibration under sound wave effect is taken pictures continuously to the transverse movement track of particle system, document image in turn;

The 3rd step is chosen a particle in piece image, and the initial horizontal when establishing this particle and starting to fall in this image is to amplitude x ₀=0, by the image stack of record in turn, obtain this particle transverse vibration curve of t in sound field in time;

The 4th step, by above-mentioned actual curve with under theoretical calculating, the oscillating curve of different-grain diameter particle in identical sound field compare, the particle diameter that to get grain diameter that curve approximation degree is the highest be this particle;

The 5th step, repeats above-mentioned third and fourth step, determines the particle diameter of other particle, until the particle diameter of all particles is determined completely in particle system, obtains the size-grade distribution of particle system.

Wherein, the theoretical value of particle amplitude obtains by solving following formula:

$F_x=\frac{d^{2}x}{{\mathrm{<figure-callout\; id="2"\; label="dt"\; filenames="HDA0000141629350000011.png,HDA0000141629350000021.png"\; state="\{\{state\}\}">dt</figure-callout>}}^2}=F_p+F_v$

In above-mentioned formula:

1, Fv is Stokes stickiness power, according to following formula substitution:

F _v＝-3πμd _p(V _x-u)

Wherein: μ is hydrodynamic force viscosity, be constant,

D _pfor grain diameter, t is the time, is independent variable,

V _xfor particle instant movement velocity in the horizontal direction, V _x=dx/dt;

2, F _pfor the acting force of acoustic pressure to particle, according to following formula substitution:

$F_p=[p(x-\frac{\sqrt{2}}{4}{d}_p,t)-p(x+\frac{\sqrt{2}}{4}{d}_p,t)]\mathrm{\&pi;}{\left(\frac{d_p}{2}\right)}^2$

For travelling plane wave, the acoustic pressure of diverse location and time provides according to the following formula:

p(x，t)＝p ₀+p _mcos[2πf(t-x/c)]

For standing-wave sound field, the acoustic pressure of diverse location and time provides according to the following formula:

$p(x,t)={\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="HDA0000141629350000031.png"\; state="\{\{state\}\}">p</figure-callout>}}_0+p_m\sin \left(2\mathrm{\&pi;}\frac{x}{\mathrm{\&lambda;}}\right)\cos \left(2\mathrm{\&pi;ft}\right)$

Wherein: p ₀for continuous medium static pressure, in calculating, can divide out,

P _mfor sound pressure amplitude, c is the velocity of sound, and f is frequency of sound wave, and λ is wave length of sound, is constant.

According to 4 rank Runge-Kutta methods, the above-mentioned ordinary differential equation about x is solved the particle displacement x t change curve in time that can draw out different-grain diameter.

A measurement mechanism for discrete state particle size distribution, is characterized in that:

Sound source generator is arranged in microscler one end, detection cabin, the baffle plate of one end covering activity, and baffle plate inner side covers one deck sound wave baffle-board or one deck abatvoix,

Detection ceiling board is transparent roof panels, and top center is offered particulate charge mouth,

Base plate is openable dianegative,

Detect top, cabin and arrange the light source irradiating downwards, detect cabin arranged beneath optical photography instrument, the camera lens of optical photography instrument is straight up just to detecting Cang center, and optical photography instrument is connected with Computer signal.

In detection cabin, arrange sound wave baffle-board on sound source generator opposite, form plane standing-wave sound field, or arrange abatvoix, or be an openend, form cavity on sound source generator opposite, form travelling plane wave sound field.

Further, the weight of considering particle system is quite low, in sound field, suspension time is longer, may affect measurement efficiency, therefore can on particulate charge mouth, configure Venturi nozzle, particle system ejects from Venturi nozzle, not only can make particle system more discrete, avoid phase mutual interference, and can accelerate the speed that moves downward of particle system.

Further again, consider that optical photography instrument sample rate is faster, just more accurate to movement of particles state description, therefore the shooting frequency of optical photography instrument was generally greater than for 3000 width/seconds.

Further again, sound source generator is transducer, and its sound source emissive power is adjustable.By changing sound source emissive power, can change the amplitude of particle vibration.In the time that grain diameter is larger, its vibration is more not obvious, and amplitude is less, therefore can suitably adjust sound source emissive power, thereby reduces the error of curve plotting.

Further, can select by the theoretical maximum amplitude of precalculated particle the focal length of optical photography instrument, thereby guarantee the accuracy of image.If be WD by detecting center, cabin to the operating distance of described optical photography instrument, the CCD wafer linear dimension of optical photography instrument is CCD, the field range of optical photography instrument is FOV, FOV is more than or equal to the theoretical maximum amplitude of particle transverse vibration in sound field, and the focal length FL of optical photography instrument camera lens can be selected by following formula:

$\mathrm{FL}=\frac{\mathrm{CCD}\&times;\mathrm{WD}}{\mathrm{FOV}}$

The present invention has following technique effect:

1, because the particle diameter of particle in sound field is less, the amplitude of its oscillating curve is larger, therefore can select less, the as much as possible theoretical curve sample contrast in particle diameter interval, can obtain the granulometry lower limit lower than optical imagery method, generally can reach below 1 micron, and the accuracy rate of testing result improves greatly;

2, method provided by the invention and device thereof adopt the mode of indirectly measuring, and in testing process, sound wave effect is in sample, and transducer does not contact with particle with expelling plate, and light source does not also directly contact with particle with optical photography instrument, has realized non-cpntact measurement completely;

3, this method and device be by recording particle movement locus or displacement and speed in the horizontal direction under sound field reflecting, and by the contrast of these record data and theoretical curves and acquisition grain diameter.Owing to not needing that dynamic granule-morphology is accurately observed, in experiment, obtain the tracing point of movement of particles by the image of high-speed capture, measuring accuracy is high;

4, this method adopts standing wave or Traveling wave act on and intervene for the particle system of discrete state, and is observed and recorded the motion state of particle by optical camera, compares with theoretical curves the particle diameter and the distribution that obtain particle; Automaticity is high, can measure fast and accurately.

Accompanying drawing explanation

Fig. 1 is apparatus structure schematic diagram of the present invention

Fig. 2～4 are the oscillating curve (frequency of sound wave be in turn 3000Hz, 30Hz and 10000Hz) of different-grain diameter particle in Traveling wave

Fig. 5 is the curve map that in Traveling wave, particle vibrates maximum amplitude and particle size

Fig. 6 is the oscillating curve (acoustic frequency 1000Hz, λ/4 position) of different-grain diameter particle in standing-wave sound field

In Fig. 1: 1 is transducer, 2 is abatvoix, and 3 is light source, and 4 is optical photography instrument, and 5 for detecting cabin, and 6 is particle to be measured, and 7 is computing machine, and 8 is Venturi nozzle.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.

As shown in Figure 1, transducer 1 is launched sound wave and is propagated and form row ripple in detection cabin 5, and act on particle 6 to be measured, particle is left and right horizontal shifting under sound field reflecting, by with sound wave vertical direction on light source 3 and optical photography instrument 4, can observe and record particle moving displacement and speed in the horizontal direction, record data are sent into computing machine 7, draw out the actual vibration curve of particle.By actual vibration curve and theoretical calculated level displacement curve (as Fig. 2), or the amplitude theoretical curve of particle displacement maximum amplitude and horizontal shift contrasts (as Fig. 3) and contrasts the granule size that can obtain a certain particle, analyze for multiple particles, can obtain the size-grade distribution of particle system.

Wherein, Fig. 2～6 can solve acquisition by following formula, according to 4 rank Runge-Kutta methods to solving about the ordinary differential equation of x as follows:

$F_x=\frac{d^{2}x}{{\mathrm{<figure-callout\; id="2"\; label="dt"\; filenames="HDA0000141629350000011.png,HDA0000141629350000021.png"\; state="\{\{state\}\}">dt</figure-callout>}}^2}=F_p+F_v$

In above-mentioned formula:

1, Fv is Stokes stickiness power, according to following formula substitution:

F _v＝-3πμd _p(V _x-u)

Wherein: μ is hydrodynamic force viscosity, be constant,

D _pfor grain diameter, t is the time, is independent variable,

V _xfor particle instant movement velocity in the horizontal direction, V _x=dx/dt;

2, F _pfor the acting force of acoustic pressure to particle, according to following formula substitution:

$F_p=[p(x-\frac{\sqrt{2}}{4}{d}_p,t)-p(x+\frac{\sqrt{2}}{4}{d}_p,t)]\mathrm{\&pi;}{\left(\frac{d_p}{2}\right)}^2$

For travelling plane wave, the acoustic pressure of diverse location and time provides according to the following formula:

p(x，t)＝p ₀+p _mcos[2πf(t-x/c)]

Wherein: p ₀for continuous medium static pressure, in calculating, can divide out,

P _mfor sound pressure amplitude, c is the velocity of sound, and f is frequency of sound wave, is constant.

Another embodiment of the present invention adopts reflecting plate, form standing-wave sound field by adjusting distance, act on particle 6 to be measured, according to 4 rank Runge-Kutta methods to solving about the ordinary differential equation of x as follows, thereby draw theoretical calculated level displacement curve (as Fig. 6):

$F_x=\frac{d^2\mathrm{<figure-callout\; id="2"\; label="x\; dt"\; filenames="HDA0000141629350000011.png,HDA0000141629350000021.png"\; state="\{\{state\}\}">x</figure-callout>}}{{\mathrm{dt}}^{}}=F_p+F_v$

In above-mentioned formula:

1, Fv is Stokes stickiness power, according to following formula substitution:

F _v＝-3πμd _p(V _x-u)

Wherein: μ is hydrodynamic force viscosity, be constant,

D _pfor grain diameter, t is the time, is independent variable,

V _xfor particle instant movement velocity in the horizontal direction, V _x=dx/dt;

2, F _pfor the acting force of acoustic pressure to particle, according to following formula substitution:

$F_p=[p(x-\frac{\sqrt{2}}{4}{d}_p,t)-p(x+\frac{\sqrt{2}}{4}{d}_p,t)]\mathrm{\&pi;}{\left(\frac{d_p}{2}\right)}^2$

The acoustic pressure of diverse location and time provides according to the following formula:

$p(x,t)={\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="HDA0000141629350000031.png"\; state="\{\{state\}\}">p</figure-callout>}}_0+p_m\sin \left(2\mathrm{\&pi;}\frac{x}{\mathrm{\&lambda;}}\right)\cos \left(2\mathrm{\&pi;ft}\right)$

Wherein: p ₀for continuous medium static pressure, in calculating, can divide out,

P _mfor sound pressure amplitude, f is frequency of sound wave, is constant.

Similar with a upper embodiment, optical photography instrument 4 is observed and the movement of particles track that records and speed and theoretical curves contrast the granule size that can obtain a certain particle, analyze for multiple particles, can obtain the size-grade distribution of particle system.

Use this device to measure discrete state particle size distribution, comprise the following steps:

1) transducer 1 plane of departure sound wave, sound wave is propagated in the horizontal direction.Can arrange reflecting plate on sound source opposite, form standing-wave sound field, if do not arrange reflecting plate, opposite is cavity or places abatvoix 2, forms travelling plane wave sound field;

2) particle to be checked 6 that is discrete state falls naturally by Action of Gravity Field, or utilizes Venturi nozzle 8 to adopt pneumatic mode vertically downward and be suspended in continuous gas medium;

3) in the method vertical with acoustic propagation direction, place light source 3 sound field is irradiated particle 6 to be checked, settle optical photography instrument 4 to take on the opposite of light source 3, document image, and send into the computing machine 7 of data processing;

Wherein, the theoretical dominant bit in-migration vibrating in sound field by count particles is determined the field range FOV of video camera, be the linear dimension of visual field, determined again the focal length FL of camera lens to the linear dimension CCD of the operating distance WD of camera lens and selected CCD wafer by measurement zone, as formula:

$\mathrm{FL}=\frac{\mathrm{CCD}\&times;\mathrm{WD}}{\mathrm{FOV}}$

4) by with sound wave vertical direction on light source 3 and optical photography instrument 4, can observe and record particle 6 to be measured moving displacement and speed in the horizontal direction, record data are sent into computing machine 7, by itself and theoretical calculated level displacement curve (as Fig. 6), analyze for multiple particles, can obtain the size-grade distribution of particle system.

5) demonstration of result: result of calculation is directly presented on computer screen with the form of curve and data.

Related description to Fig. 2～4:

1, change sound wave frequency, can change the cycle of particle oscillating curve, this filming frequency that makes to detect high-speed camera also can be different, in the time that frequency of sound wave is higher simultaneously, the frequency of taking also needs to increase accordingly, generally should guarantee that a vibration period has 8～10 to take pictures.

2, change sound wave frequency, can change the scope of sensitive particles granularity equally, for example, adopts approximately 10～200 microns of its sensitive particles of low frequency 30Hz sound wave; Adopt 10000Hz sound wave, approximately 0.1～10 micron of sensitive particles.So raising frequency of sound wave, can make measurement lower limit reduce.

3, change sound wave frequency, in the sound source of equality strength, the amplitude difference of particle vibration, is 140 decibels for the sound intensity in figure, when 30Hz, Oscillation Amplitude can reach 300 microns, and for the sound wave of 10000Hz, Oscillation Amplitude only has 10 microns.Oscillation Amplitude can change by adjusting strength of sound source.

Claims (7)

1. a measuring method for discrete state particle size distribution, is characterized in that:

The first step, the sound field of arranging a plane of departure standing wave sound wave or travelling plane wave, sound direction of wave travel is horizontal direction;

Second step, the particle of discrete state ties up under self gravitation or External Force Acting to fall, enter sound field from sound field top, and occurred level transverse vibration under sound wave effect is taken pictures continuously to the transverse movement track of particle system, document image in turn;

The 3rd step is chosen a particle in piece image, and the initial horizontal when establishing this particle and starting to fall in this image is to amplitude x ₀=0, by the image stack of record in turn, obtain this particle transverse vibration curve of t in sound field in time;

The 4th step, by above-mentioned transverse vibration curve with under theoretical calculating, the oscillating curve of different-grain diameter particle in identical sound field compare, the particle diameter that to get grain diameter that curve approximation degree is the highest be this particle;

The 5th step, repeats above-mentioned third and fourth step, determines the particle diameter of other particle, until the particle diameter of all particles is determined completely in particle system, obtains the size-grade distribution of particle system;

The amplitude theoretical value of particle obtains by solving following formula:

$F_x=\frac{d^{2}x}{{\mathrm{dt}}^2}=F_p+F_v$

In above-mentioned formula:

1., Fv is Stokes stickiness power, according to following formula substitution:

F _v＝-3πμd _p(V _x-u)

Wherein: μ is hydrodynamic force viscosity, be constant,

D _pfor grain diameter, t is the time, is independent variable,

V _xfor particle instant movement velocity in the horizontal direction, V _x=dx/dt;

2., Fp is the acting force of acoustic pressure to particle, according to following formula substitution:

$F_p=[p(x-\frac{\sqrt{2}}{4}{d}_p,t)-p(x+\frac{\sqrt{2}}{4}{d}_p,t)]\mathrm{\&pi;}{\left(\frac{d_p}{2}\right)}^2$

For travelling plane wave, the acoustic pressure of diverse location and time provides according to the following formula:

p(x,t)＝p ₀+p _mcos[2πf(t-x/c)]

For standing-wave sound field, the acoustic pressure of diverse location and time provides according to the following formula:

$p(x,t)=p_0+p_m\sin \left(2\mathrm{\&pi;}\frac{x}{\mathrm{\&lambda;}}\right)\cos \left(2\mathrm{\&pi;ft}\right)$

Wherein: p ₀for continuous medium static pressure, in calculating, can divide out,

P _mfor sound pressure amplitude, c is the velocity of sound, and f is frequency of sound wave, and λ is wave length of sound, is constant.

2. a discrete state particle size distribution measuring method according to claim 1, the measurement mechanism using in described method is: sound source generator is arranged in microscler one end, detection cabin (5), the baffle plate of one end covering activity, baffle plate inner side covers one deck sound wave baffle-board or one deck abatvoix (2)

Detecting cabin (5) top board is transparent roof panels, and top center is offered particulate charge mouth, and base plate is openable dianegative,

Detect top, cabin (5) and arrange the light source (3) irradiating downwards, detect cabin (5) arranged beneath optical photography instrument (4), the camera lens of optical photography instrument (4) is straight up just to detecting the center in cabin (5), and optical photography instrument (4) is connected with computing machine (7) signal.

3. discrete state particle size distribution measuring method according to claim 2, is characterized in that: on described particulate charge mouth, configure Venturi nozzle (8).

4. discrete state particle size distribution measuring method according to claim 2, is characterized in that: the shooting frequency of described optical photography instrument was greater than for 3000 width/seconds.

5. discrete state particle size distribution measuring method according to claim 2, is characterized in that: described sound source generator is transducer (1).

6. discrete state particle size distribution measuring method according to claim 2, it is characterized in that: establishing by detecting center, cabin (5) is WD to the operating distance of described optical photography instrument, the CCD wafer linear dimension of optical photography instrument (4) is CCD, the field range of optical photography instrument (5) is FOV, FOV is more than or equal to the theoretical maximum amplitude of particle transverse vibration in sound field, and the focal length FL of optical photography instrument camera lens can be selected by following formula:

$\mathrm{FL}=\frac{\mathrm{CCD}\&times;\mathrm{WD}}{\mathrm{FOV}}.$

7. discrete state particle size distribution measuring method according to claim 2, is characterized in that: the sound source emissive power of described sound source generator is adjustable.

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