Reconstruction of Real Size Distributions Hidden in Phase‐Doppler Anemometry results obtained form droplets of inhomogeneous liquids

Manasse, Uwe; Wriedt, Thomas; Bauckhage, Klaus

doi:10.1002/ppsc.19940110111

Cited by 12 publications

(6 citation statements)

References 4 publications

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“…This procedure shows, that the application range of PDA can be extended to a wide range of atomization processes, including non homogeneous liquids, with the possibility of correcting distorted size distributions. 5 …”

Section: Resultsmentioning

confidence: 97%

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Evaluation of PDA measuring results obtained from sprays of optically inhomogeneous liquids

Wriedt¹,

Mitschke

Lehmann

1995

SPIE Proceedings

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For control and optimization ofatomization processes measurement techniques are employed beeing able to determine the diameter and the velocity of the generated droplets. The so-called "Phase-Doppler-Anemometry" (FDA) measuring simultaneously both distributions has been successftilly applied to sprays of homogeneous liquids like water, molten metals etc. In a lot of other technical processes liquids contain optical inhomogeneities consisting of suspended superfme particles. In general the measured droplet size distributions of such process fluids appear to be broadened compared to the "real-one". In the following an approximate method for fmding the "real-size" distributions is introduced. A blurring ftinction is obtained by performing FDA measurements on single-sized droplets. An iterative constrained inversion algorithm is applied evaluating the real-size distribution. The precision of the algorithm is checked by companng the calculated distributions with undistorted measuring results of an atomized optically homogeneous liquid.Keywords: p article-sizing, Phase-Doppler-Anemometiy, inhomogeneous process fluids, ill-posed problems, inversion problems, constrained iterative inversion algorithm INFRODUCTIONWith the advance of process automatization, the demand for fast and high precision measuring and automatic control techniques increases. Avoiding or minimizing low-grade product charges, in line measuring techniques which allow in-situ process control are favoured. In a lot ofdifferent areas ofindustrial processes the atomization ofliquids has become an important unit operation. The quality ofthe atomization process defines product's qualities. For control and optimization ofthese processes the diameter and the velocity of the atomized droplets have to be measured continuously. Optical measurement techniques are prefered because they do not affect the formation of droplets and they need short measuring times.A well established method of theses techniques is the so-called "Phase-Doppler-Anemometry" (PDA)"2 allowing simultaneous measurements of droplet and velocity distributions. In this method an interference fringe field is produced by two crossing laser beams. The light-intensity scattered by a passing single particle is detected at two different locations. The frequency of each signal is proportional to the velocity ofthe particle. The particle diameter is related to the phase difference between both signals. The application of Mie-theory enables the evaluation of this relation3. Whereas the measurement of the velocity distribution is normally uncomplicated problems are encountered by determining the correct size distribution.Mie theory is applicable to homogeneous spherical particles with constant refraction index. Therefore FDA has been successfully applied to sprays ofhomogeneous media like water, mineral oil, molten glass, metals and gas bubbles. Difficulties arise when measuring optical inhomogeneous liquids containing compounds -inmost cases suspended superfine particles -in the order of the laser wavelen...

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Section: Resultsmentioning

confidence: 97%

“…Each step ofthe iteration is given by q (n#1) K Tm + (I -K TK) q . (5) where q'is the calculated distribution after n iteration steps. T is the transposed matrix ofK and I describes the Identity matrix.…”

Section: Inversionmentioning

confidence: 99%

Evaluation of PDA measuring results obtained from sprays of optically inhomogeneous liquids

Wriedt¹,

Mitschke

Lehmann

1995

SPIE Proceedings

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“…[17,18] The broadening effect is caused by complicated measuring situations, i.e., when the PDA-signal is extremely noisesuperimposed. This is due to a systematic broadening effect in phase difference and diameter respectively.…”

Section: Resultsmentioning

confidence: 99%

Simulation of Agglomeration in Spray Drying Installations: The EDECAD Project

et al. 2004

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Spray drying is used for the manufacture of many consumer and industrial products such as instant dairy and food products, laundry detergents, pharmaceuticals, ceramics, and agrochemicals. During spray drying, agglomerates of powder particles are formed which determine the instant properties of the powder. Agglomeration during spray drying is considered to be a difficult process to control. The main cause of this is the complex interaction of the process variables: the atomization process, the mixing of spray and hot air, the drying of suspension droplets and the collision of particles which might lead to coalescence or agglomeration. As a consequence, agglomeration during spray drying is operated by trial-anderror. In an EC-sponsored project, named the EDECAD projects, an industrially validated computer model, using CFD technology, to predict agglomeration processes in spray drying machines is developed. An Euler-Lagrange approach with appropriate elementary models for drying, collision, coalescence and agglomeration of the dispersed phase is used. The main result of the EDECAD project is a so-called ''Design Tool,'' which establishes relations between the configuration of the drying installation (geometry, nozzle selection), process conditions, product composition and final powder properties. The Design Tool is being validated on pilot-plant scale and industrial scale. It will provide an advanced tool for improved design and optimization of spray drying and agglomeration equipment, to improve the quality of products and to increase the productivity of such equipment. This article introduces the background and approach of the project and some preliminary results.

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“…In the former case, the influence of the heterogeneity and opacity of the liquid on the light scattering is negligible, while it is considerable in the latter. A method relying on a convolution/ deconvolution process to correct drop size PDFs measured with light refracted from heterogeneous drops, as proposed by Manasse et al (1994), turned out unreliable and does not prevail as an established and recognized procedure.…”

Section: Tablementioning

confidence: 98%

Characterization of spray formation from emulsions by pressure-swirl atomizers for spray drying

Tratnig

Brenn

Strixner

et al. 2009

Journal of Food Engineering

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Reconstruction of Real Size Distributions Hidden in Phase‐Doppler Anemometry results obtained form droplets of inhomogeneous liquids

Cited by 12 publications

References 4 publications

Evaluation of PDA measuring results obtained from sprays of optically inhomogeneous liquids

Evaluation of PDA measuring results obtained from sprays of optically inhomogeneous liquids

Simulation of Agglomeration in Spray Drying Installations: The EDECAD Project

Characterization of spray formation from emulsions by pressure-swirl atomizers for spray drying

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