摘要:

AbstractThis paper describes new progress obtained with an optical technique called V.I.D.E. (Visible Infra‐red Double Extinction) which simultaneously measures mean particle size in the range of 10–120 μm and mean number density in densely laden media (up to 0.1% volume fraction). The underlying theory, taking account of multiple light scattering, is recalled. Simultaneous size and concentration measurements are obtained by simultaneously recording transmittances of the medium at two well chosen wavelengths. Experimental results for suspensions of glass particles in air, are described and discussed. The size of particles given by the technique agrees with that given by optical microscopy and Malvern diffractometry. The V.I.D.E. technique is shown to be very suitable to investigate dense media whose optical thickness is up to nine and for which other techniques

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050201

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractA model for the direct problem of calculating the forward scattering signature of a multiple scattering medium is presented. The new formulation is optimized for integration into schemes for reconstructing the particle size distribution from laser diffraction (forward scattering) signatures obtained from optically thick media. The analysis is valid for media where the particle sizes and interparticle spacings are large (relative to the wavelength and the particle size, respectively) such that Fraunhofer diffraction theory adequately describes the properties of the forward scattered light from individual scattering events. The simulated performance of laser diffraction particle sizing instruments was then studied using predictions of the scattered light signatures which would be measured by laser diffraction instrument under multiple scattering conditions. The results were compared with experimental data and theoretical calculations based on other models.

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050202

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractSimultaneous size and velocity measurements can be obtained by using photodetector positions of different off‐axis‐angles. But not for all of these positions one receives unambiguous results for the correlation between the phase difference and the particle diameter. This can be clearly demonstrated by the plots of the numerical calculations of the complete Mie's scattering equations. These plots show that for transparent particles which exceed the continuous phase in density at special off‐axis‐angles the situation of light refraction changes into a situation of additional light reflection or vice versa. On the other hand for transparent particles which are less dense compared with the continuous phase and for totally absorbing materials these plots confirm the simplified equations for reckoning the particle diameter by the laws of geometrical optics. The good agreement between these results can also be verified for the backscatter mode for measurements of metallic spheres with an imaginary refractiv

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050203

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractPhoton correlation spectroscopy (PCS) has been applied to various systems of particles suspended in a fluid. Computer simulations were used to analyse CONTIN, a program for the numerical inversion of the experimental data. Measurements were performed on a spectrometer equipped with a digital correlator. Various suspensions of polysterene latex spheres differing both in size and size distribution were prepared in double distilled water. Further some samples provided by an external institution without prior specification were analysed. Diffusivity measurements on submicron DES (di‐2‐ethylhexyl sebacate) particles in nitrogen were also performed. The results obtained demonstrate the strengths and the limitations of PCS as a method of determining particle size distributions in particle fluid syst

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050204

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThis paper is based on the development of the Moza‐Austin technique for characterizing thousands of coal particles by approximate analysis of the major inorganic constituents Ca, Al, Si, K, Na, Fe and S in each particle. The technique has sufficient sensitivity to work on small volumes, is fast enough to handle large number of particles within a reasonable period of time, and consists of scanning electron microscopy combined with energy dispersive x‐ray spectrometry (SEM‐EDS). A computerized SEM‐EDS system that allows the automated analysis of hundreds of particles per hour is described. The analysis is based on the location and tracing of exposed areas of particles embedded in a polished specimen, the selection of sampling points on the traced sections, the collection of an x‐ray spectrum from each sampled point for a defined period of time, and the processing of the x‐ray intensity to calculate point composition using ZAF corrections. Procedures for correcting for dead time, spectrum background, x‐ray detector efficiency and spectrum overlap are described. Problems and future work

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050205

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThis note deals with the Fourier representation of particle shape. A frequency distributionpn,n= 1,2, …, expressing the contribution of the different harmonics to the dispersion of the position vector is defined. The Meloy law of morphological coefficients may be derived by optimizing the value of the informational entropy which is attached top

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050206

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractInvestigations are presented on particle separation in impactors, sampling cyclones and other precollectors. These devices are increasingly used for the characterization of particulate matter. Size selective samplers must be characterized by their grade efficiency curves. A new measuring procedure is presented, which permits the determination of the grade efficiency curves of various sampling devices. An optical particle counter and a vibrating orifice generator are used in these measurements. This calibration technique is fast and has a high resolution. Investigations were carried out on the influence of various parameters on the classification efficiency of impactors and sampling cyclones. Using the extensive data measured a better understanding and quantification of impactor and cyclone behaviour is developed which may improve their applications in particle sampling.

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050207

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThis paper attempts to answer the question of whether a measurement of the relative flow rate of a suspension of spheres, flowing under constant pressure drop through gaps of precisely determined geometry, may be utilised to measure the concentration and size distribution of the particles. A positive answer is possible only if several restrictions are imposed on the character of the flow, a maximum ratio of sphere diameter to gap height and a maximum number of captured particles. This answer is based on a model of the filtration process taking place in the gap and the consequent relationship between the flow characteristics of the gap and the number and diameter of the captured particles.

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050208

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050209

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY