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Title:
TECHNIQUES FOR THE CHARACTERIZATION OF TRANSPARENT AND NON-TRANSPARENT PARTICLES USING SCATTERED LIGHT SIGNALS
Document Type and Number:
WIPO Patent Application WO/2018/207200
Kind Code:
A2
Inventors:
BAKSHE PRASHANT (IN)
Application Number:
PCT/IN2018/050119
Publication Date:
November 15, 2018
Filing Date:
March 05, 2018
Export Citation:
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Assignee:
BAKSHE PRASHANT (IN)
International Classes:
G01N21/47; H01S3/00
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Claims:
Claims

[Claim 1 ] |A velocity measurement using methods shown in Figure 1 , 2 and 3. A manner and a method and a technique are claimed. A fundamental idea is claimed.

[Claim 2] An acceleration measurement using methods in Figure 3, Figure 5 is claimed. An idea, the method and the manner in which the acceleration is measured along with all beam width methods is claimed.

[Claim 3] A particle size measurement using method shown in Figure 4. The particle sizing here is primarily the function of velocity measurement using above method as long as a velocity measurement is correct using an above mentioned method

[Claim 4] A measurement of refractive index using method shown in Figure 6 is claimed. The

method, manner and idea all are claimed. Claim is made for idea, method and technique in which R. I. is estimated.

[Claim 5] An estimation of spherisity of particles as shown in Figure 7 is claimed. A claim is also for a method, manner and idea behind this estimation.

[Claim 6] A flow direction measurement against the frequency shifted method of direction estimation as shown in Figure 7. Claim is made for method, idea and technique of direction measurement and also for its inclusion in all the recent modified Laser Doppler and Phase Doppler instruments.

[Claim 7] Number of drops per second mass flux, volume flux and number flux of particles can be decided as shown in Figure 7. Technique, idea and method are claimed.

[Claim 8] All the industrial applications enlisted above but not limited to the same are claimed.

They are based on the claimed idea of the patent.j

Description:
Description

Techniques for the characterization of transparent and non-transparent particles using scattered light signals

[0001 ] [The atmospheric phenomena of optical scattering is the very base for this patent application.

Many times the secondary rainbow pattern can be visible on the fountain of running water or on the clouds during or just after the rain. This is due to the occurrence of different scattering orders received from fountains or clouds on optical receivers. In the presentation of idea here, spherical, transparent and non-transparent particles (15, 24, and 25) in motion are illuminated by the coherent light beam at measurement volume (8) of a few microns size using a transmitting optics (5) and beam shaping optics (6), transmitting lenses (7) and probes (5). The light scattered by particles is collected on the optical receiver/s positioned at an angle of 1 51 0 to the horizontal axis or the laser beam. Scattering is visible as optical signals on the receivers (14, 23). The characterization of signal gives several measurement parameters of the particles and multiphase flow. Idea of method of characterization is mentioned in the Figure 2. The following specification particularly describes the invention and the manner in which it is to be performed.

Technical Field

[0002] The patent is in the field of optical characterization of multiphase flow. The multiphase flow is comprised of solid or liquid particles suspended in gaseous or fluid medium. The spray processes and spraying systems can be characterized using the techniques discussed here in this patent. The optical scattering phenomena investigated from the naturally occurring Rainbow Phenomena is the key behind the techniques described in this patent.

[0003] The patent is in the field of optics, laser measurement and signal processing. A laser light sheet of a few microns size is used as a measurement volume at its beam waist. The particles pass through it and create the signals on optical receivers. In terms of received signals, the size, velocity, acceleration, direction, flux density, number density, turbulence can be estimated.

[0004] The patent leads to the industrial applications and instruments such as optical vibration measuring device, weather monitoring device, accelerometer, turbulence measuring device, refractive index measuring device, torsional stress and rpm measuring device, viscosity measuring device, beam scan device, instrument for water quality determination in running streams and canals.

Background Art

[0005] In the background of this invention, there stays the naturally occurring "Rainbow Phenomena".

The cloud appear to work as an optical receiver, at the same time, it is the human eye without which this natural creation is not visible. The human eye is considered as the optical receiver in several articles (Hulst, 1957). The atmosphere is filled with gases, aerosol particles and the vapours of water or the moisture. The very basic information of cloud formation starts from the creation of small droplets and their growth (Fletcher, 1966). Due to the contribution to the formation of droplet particles of fine size, the aerosol particles in the atmosphere has a role in the formation of condensation nuclei (T. Novakov, 1993). The aerosol particles provide surface for the condensation of atmospheric water vapours. The condensed particles grow in size depending upon the possibility of further condensation growth and the merging of several droplet particles. Some attempts of measurement of cloud condensation nuclei are also made during the experimentation (Timothy M. VanReken, 2003). The sunlight falling on the droplet particles is scattered back to the atmosphere. This scattering is through different modes of scattering and scattering orders. Primarily the modes of scattering are due to diffraction, reflection and refraction of light from the droplet particles. There are several internal reflections of light within the droplet particles, based on it are the different scattering orders visible. The fact is evident through the naturally occurring secondary rainbow patterns in which one rainbow is clearly visible and other one is faint (Raymond L. Lee, 2001 ). This is due to the different scattering orders scattered form the droplets. The observer sitting in a plane can see complete round circle of rainbow appearing on cloud. Depending upon the location of the observer, the angle made by him with the sunrays, location of particle, different scattering orders can be visible. It is the interesting phenomena that the human eye can see two rainbows on cloud. One is brighter and clear whereas other one is observed with difficulty due to less intensity of light wavelengths. Both are available on the cloud if the cloud is considered as a receiver. The interesting fact is how one eye can see both rainbows at a time at one angle. The artificial optical detectors can detect such scattering orders. One scattering order is bright and the other one has less intensity. The separation is through the Alexanders Dark Band (Raymond L. Lee, 2001 ). The droplet particles have fine size of a few microns. The coherent light in the form of a shaped beam can be made to fall on the droplet particle or the solid transparent particle such as glass ball to investigate the scattering patterns and scattering phenomena.

6] When the particles suspended in a moving fluid are a few microns in size, the particles are simply carried away by the fluid. The velocity of the fluid is taken equal to the velocity of the particles. With the increase in size of suspended particles, the relation of equal velocity between particles and fluid is no more in existence. This is due to the flow around the suspended particles and the larger weight and size (G. F. Hewitt, 1997) (Chisholm, 1983). The difference between the velocities is a slip velocity, liquid being a carrier fluid. Slip velocity is more if the carrier phase is gas. The example is the chimney exhaust where small particles are carried a long distance away from chimney due to cross winds, the heavy particles fall nearby. The size and weight matters. The size can be calculated in different ways and different approaches of mathematical modelling of the distribution of this particulate matter in the surrounding can also be studied. In spraying system, the velocity is important as the dynamic forces are responsible for breakup of particles into fine size (Arthur. H. Lefebvre, 2017). More the velocity, the better is the breakup and finer is the size. The particle size can also be approximately estimated in a simple method of sampli ng particles using a shallow pot of liquid filled with immiscible type below the atomizer. The distance of particles from axis of spray contributes to the particle scatter and spray cone angle. In metallurgical spraying systems, the liquid metal spray can be made to fall on shallow pot filled with quenching liquid that solidifies the liquid hot metal. The samples may be obtained in manual way or by the image processing of image of the sampling shallow pot. The increase in level of quenching liquid can be the indicative of mass of spray if vaporization of liquid is ignored (USA Patentnr. 5366206, 1994).

[0007] Other simple techniques of spray characterisation are the forward illumination and background illumination imaging techniques. The front illumination and background illumination and simultaneous photography of spray can create particle images for particle sampling. The processing of images give the size of particles and the particle number density in the measurement volume. The imaging with time difference of few micro seconds creates the multiple impressions of same object (particle) in a single frame (Bakshe, 2015). This is the technique called particle tracking method. Simultaneous velocity and size of particles is also possible here. Laser illumination of droplet particles create images on the optical detectors (CCD). Light interferometry is of interest since 1909 (Ingram Taylor, 1909). It was used for optical characterization of particles later on. The interference pattern can be seen on the detectors. Interferometry can be the tool to measure the size of the particles in terms of relation between the distance between interference fringes and the number of fringes and their size with work at fundamental level was created much earlier (Rizzo, 1975). The aerosol particles illuminated using laser beams may be captured using the CCD receivers in the form of interference pattern. Work by Kaye et. al. is for the particle characteristics from an aerosol or other suspension of particles in a particle stream. (Britain Patentnr. US5471299A, 1993). It would have been obvious for a person of ordinary skill in the art at the time of the invention was made to combine the inventions as disclosed in the present patent to reach the embodiment as disclosed in claims (Saurabh, 2017).

[0008] As per the articles in publication, laser Doppler systems are already in use for the estimation of velocity of the multiphase flow systems including solid and liquid particles. The Phase Doppler Systems are described for their ability to measure the size and velocity of multiphase particles through several research articles (Adrian, 1 997).

Summary of Invention

[0009] The optical method and signal processing method is described here in detail to characterize the multiphase flows. This optical method employs the principle of optical scattering phenomena. The scattering orders are gathered on the optical receivers and processed to obtain the key characteristics such as velocity, turbulence, acceleration, mass flux, and number flux, direction of flow without using Bragg cell unit, fluid element stresses, vorticity, and circularity. The applicability of the idea described in the embodiment is in the industrial sector for the measurement of torsional stresses, beam scan apparatus, rpm measurement, weather forecasting devices, marine science applications, instruments for the water quality inspection in flowing dam chutes, rivers and canals tap waters, process industries, powder manufacturing industry

Technical Problem

[001 0] The laser Doppler (LD) and phase Doppler (PDS) systems are the black box systems often portrayed as instrument for the characterization of multiphase flow particles through several research articles including those in SPIE. These different PD systems claim to characterize the particles with the use of phase difference, in terms of their own custom definition of the term called phase. The characterization is said to be possible in the area of estimation of velocity and size of particle. However, due to the unsymmetrical and varying frequency Doppler signals, with an acceleration component in it, correct velocity estimation is not always possible. Some of the so called modern PDSs also work on frequency peak pairing for the size estimation. The transit time analysis of particles in measurement volume need to be reworked for the improvement in accuracies. In case of multiple frequencies in Doppler signals, the exact peak location after the 40MHz shifted bandwidth, is difficult. LD/PD systems are more complicated in terms of their alignment, components. As long as the practical signals are not accurate, the addition of electronic devices and adding weight into the system for the mathematical treatment cannot improve the accuracy of fluid flow measurements. The results of LD/PD system are not accurate as the original signals are not symmetrical in frequency. Mere making mathematical efforts in correcting the signals cannot make the measurements accurate. The burst signals available at the outlet of the Doppler system are corrected signals and they are not in the original form.

Solution to Problem

[001 1 ] The present idea elaborated here describes the method of multiphase flow and spray (25) characterization for obtaining improved accuracy in the measurement. To solve the problem, the independent scattering orders from the laser illuminated droplet particles is gathered on the single optical receiver for transparent droplet particle characterization. Whereas, two optical receivers are used for the characterisation of signals of reflection scattering orders for the non-transparent particles. The relation between the half beam width and Gaussian shaped independent scattering orders and the half signal width is the key for obtaining correct velocities. As long as the velocities are accurate, the size has meaning and the temporal difference between peaks have the meaning. So is the condition for temporal difference between the Doppler signals illustrated in Figure 4.

Advantageous Effects of Invention

[0012] The complete elimination of a costly and difficult to align bragg cell unit which is predominantly used for determination direction of flow calculation of particles using very simple technique. The Brag cell units shift the frequency of one laser beam.

[0013] This bragg cell unit consisting of frequency shifted beams, consumes the bandwidth of the high speed data acquisition system. This is visible on PSD or frequency vs amplitude plot. Any measurement of velocity is indicated on this plot as the summation of bandwidth related to frequency shift and the frequency corresponding to the velocity of particle passing through the optical measurement volume (state what is measurement volume).

[0014] Number density measurement is accurate in the proposed system. Mass flow rate/mass flux, volume flux measurement is also possible with accuracy. Acceleration component of the particulate flow is possible to measure with accuracy. 2D velocity and size measurements of particles are also possible with the proposed technique. Turbulence can also be estimated easily.

[001 5] Accuracy in the measurement of velocity and the size of the particles. Size is a function of how accurate the velocity is measured in terms of signals. The signals received on the optical receivers are the independent scattering order and hence give more accurate results for spherical particle characterisation than the LD/PD systems.

Brief Description of Drawings

[001 6] Figure 1 shows the experimental arrangement for the invention. The optical arrangement consists of two back scattered light receivers (1 ) and (2) arranged at 151 0, symmetrically placed about the optical transmitter-receiver probe (5). The beam shaping optics (6), transmits the light through, achromatic spherical lens (7) and creates minimum size of the measurement volume (8) of a few microns 12-25 urn. The light is bent using a metal optic mirror at 900 using a prism. The metal optic prism is the best suitable for this arrangement. The optical measurement volume (8) is Gaussian in nature that could be visible as a profile (29) on beam scan instrument display. When the particles pass through measurement volume, scattering orders are created on (1 ) and (2). Temporal difference between signal peaks (27) is created for the transparent particles and the temporal difference (28) is created for the non-transparent particles, (9) is contributed by refraction scattering order, reflection scattering order and surface waves, whereas (10) consists of only the reflection scattering order and surface waves. One optical receiver is enough for transparent particle characterization on one dimension. Whereas two receivers are needed for the characterization of non-transparent particles, two receivers are needed (Claim 1 ).

[001 7] Figure 2 (right) part shows the schematic diagram of laser beam profile at its minimum beam width at the measurement volume (8) which is a few microns in size. This is obtained using beam profiler unit that measures the beam width at its focus. The other half (left) part of the Figure 2 is either the refraction peak (9) or reflection peak (10). The ratio (1 1 ) of half beam width (12) (HBW) of Gaussian structure of beam at the measurement volume to the half temporal width (13) (HTW) of the independent scattering order gives velocity of the particle and this ratio contributes the characterization of the droplet particles. (Claim 1 )

[001 8] Figure 3 shows the complete signal (14) consisting of both refraction peak (9) and reflection peak (10). The same relation (1 1 ) of velocity estimation is used for both peaks. It additionally provides acceleration component / characteristics of spherical particles (15). However here the acceleration may be effectively observed at 100 m/s2. (Claim 1 , Claim 2) [001 9] Figure 4 shows the optical probe transmitting two pairs (16) and (17) of light beams intersecting in a single focus point (1 8). Each pair is made of single wavelength. Each pair is contained in independent plane. Both the pairs are such that the containment plane are perpendicular to each other. The optical receiver pairs (1 -3), (2-4) are all arranged perpendicular to each other in a single plane (XZ) (19) including and transmitting-receiving optics. When particles pass through the measurement volume at single point of combined focus, the temporal difference between signal peaks obtained on receiver 1 -3 provides velocity in vertical direction Vz (20) whereas a receiver pair 2-4 provides velocity in horizontal direction Vx (21 ). (Claim 3)

[0020] Figure 5 shows the frequency spectrum (22) of Doppler signals (23) shown in the inset which are created at the detectors (1 ) & (3) or (4) & (2) of Figure 4. Acceleration component of particle can be found using this spectrum as it shows the shift in the frequency peaks. However, here too the acceleration may be effectively observed at 90-100 m/s2. (Claim 2)

[0021 ] Figure 6, shows the graph of optical scattering from spherical transparent particles, when illuminated by the optical measurement volume, and is obtained on a Mie plot. The signals are received on pair (1 -2) in Figure 1 . With the change in the refractive index of particles, peaks of the scattering curves (31 ) show displacement on the plot. From this displacement, the refractive index can be obtained. (Claim 4)

[0022] Figure 7 shows the stable droplet chain (24) of equidistant spherical particles at a high speed of 50000-80000 drops per second. The plot shows the signals obtained on the optical detector pairs. From the auto correlation function of paired signals, the sphericity of particles can be decided (Claim 5), the flow direction can be decided (Claim 6), and the number of drops per second/mass flux/number flux of particles can be decided (Claim 7).

[0023] These arrangements in Figure 1 -4, can also give the turbulence characteristics of the fluid by the Eulerian method of observation. (Claim 8)

Fig.1

[0024] [Fig.1 ] illustrates the architecture for the invention of the product.

Fig.2

[Fig.2] illustrates key idea of the patented work. The Gaussian half beam width and Gaussian half temporal width.

Fig.3

[0025] [Fig.3] illustrates scattered signal pair from a single spherical droplet particle consisting of predominant reflection and refraction scattering orders.

Fig.4 [0026] [Fig.4] shows the Doppler signals with temporal difference used for the estimation of size and acceleration provided the velocity measurements are accurate.

Fig.5

[0027] [Fig.5] illustrates the frequency plot of two Doppler signals during real time online data

acquisition with dominant two frequency peaks for two signals beyond the frequency shift value of 40 MHz

Fig.6

[0028] [Fig.6] shows the key idea behind the calculation of refractive index of particles

Fig.7

[Fig.7] displays and confirms the method of determination of direction of particle movement.

Description of Embodiments

[0029] The idea is elaborated here to characterize the near spherical to spherical droplet particles.

The particles could be transparent or non-transparent depending upon the fluid used. The optical signal /scattering order received on receiver from the particle illuminated by shaped laser beam is processed in the manner shown in the Figure 2. An exemplary embodiment of the present invention is illustrated by the accompanying drawings, Figure 2, 5, 6 and 7 whereas the necessary experimental arrangements of the inventions are emphasized through drawings 1 , 3, and 4.

Industrial Applicability

[0030] A patent is applicable for the measurement of velocity of particles in fluid flow, thus the instrument for the measurement of velocity can be manufactured

[0031 ] High acceleration values of moving parts can be estimated;

[0032] A Brag cell unit of Phase Doppler and Laser Doppler systems can be replaced by using the simple technique of sequence of signals from the droplet particles. Technic of direction measurement can be incorporated in LD / PD systems

[0033] An instrument for measurement of refractive index of the particles can be manufactured using this technique

[0034] A turbulence measuring instrument can be developed and built

[0035] Flux density of particles can be calculated. An instrument can be developed for the determination of pollution index in ppm.

[0036] A laser beam scan instrument can be developed using this technique

[0037] An instrument for the measurement of torsional stress of the rotating shafts can be developed. [0038] Instrument for the detection of vorticity and circularity of fluid elements can be built

[0039] An instrument for the measurement of RPM of machine components can be built

[0040] An instrument for the estimation of weather pollution and acid content of the moisture particles in clouds can be developed and manufactured

[0041 ] An instrument can be built for the examination of drinking quality of real time running water including the river and canal water.

[0042] A technique is also proposed for the measurement of slip velocity in multiphase flow and can be incorporated in flow measurement device

[0043] An instrument for the measurement of viscosity of liquid can be built.

Non Patent Literature

[0044] NPL1 : Patent publication 20172101 6596 [0045]

Citation List follows

Adrian, . J. (1997). Selected Papers on Laser Doppler Velocimetry. SPIE press. Arthur. H. Lefebvre, V. G. (2017). Atomization and sprays. CRC press.

Chisholm, D. (1983). Two phase flow in pipelines and heat exchangers. Longman Higher Education.

Fletcher, N. H. (1966). The physics of rainclouds. Edinburg: Cambridge University Press.

G. F. Hewitt, G. L. (1997). International encyclopedia of heat and mass transfer. CRC press.

Grant R, F. (1989). Introduction to Modern Optics. NYC: Dover Publications, p6.

Hulst, H. v. (1957). Light scattering by small particles. Dover Publication, Inc. New York.

Ingram Taylor, S. G. (1909). Interference Fringes with Feeble Light. Proc. Cam. Phil. Soc, 15:114.

Magie, W. F. (1963). A Source Book in Physics. Harvard Univ. Press, pp. 335-337.

Paul H. Kaye, K., & Edwin Hirst, H. H. (1993). Britain Patent No. US5471299A.

Raymond L. Lee, A. B. (2001). The rainbow bridge, Rainbows in Art, Myth and Science. Pennsylvania University Press.

Rizzo, J. E. (1975). A laser Doppler interferometer. Journal of Physics E: Scientific Instruments.

Saurabh, P. (2017). First Examination Report. Mumbai: Indian Patent Office.

T. Novakov, J. E. (1993). Large contribution of organic aerosols to cloud condensation nuclei

concentrations. Letters to nature, 365, 5. Thomas F. Sawyer, W. T. (1994). USA Patent No. 5366206.

Timothy M. VanReken, T. A. (2003). Toward aerosol/cloud condensation nuclei (CCN) closure during CRYSTAL-FACE. Journal of geophysical research, 18.

Patent Literature

[0046] PTL1 : USA Patentnr. 5366206, 1994).

[0047] PTL2: Britain Patentnr. US5471299A, 1993 j