Mingxu Su

AN INVESTIGATION ON CHARACTERIZING DENSE COAL-WATER SLURRY WITH ULTRASOUND: THEORETICAL AND EXPERIMENTAL METHOD

Particle size distribution and concentration in particulate two-phase flow are important parameters in a wide variety of industrial areas. For the purpose of online characterization in dense coal-water slurries, ultrasonic methods have many advantages such as avoiding dilution, the capability for being used in real time, and noninvasive testing, while light-based techniques are not capable of providing information because optical methods often require the slurry to be diluted. In this article, the modified Urick equation including temperature modification, which can be used to determine the concentration by means of the measurement of ultrasonic velocity in a coal-water slurry, is evaluated on the basis of theoretical analysis and experimental study. A combination of the coupled-phase model and the Bouguer-Lambert-Beer law is employed in this work, and the attenuation spectrum is measured within the frequency region from 3 to 12 MHz. Particle size distributions of the coal-water slurry at different volume fractions are obtained with the optimum regularization technique. Therefore, the ultrasonic technique presented in this work brings the possibility of using ultrasound for online measurements of dense slurries.

A NEW ALGORITHM OF RELAXATION METHOD FOR PARTICLE ANALYSIS FROM FORWARD SCATTERED LIGHT

A new algorithm of the relaxation method is developed for the inversion of forward scattered light to obtain the size distribution of spherical particles. Numerical tests are performed for a laser particle analyzer using the Mie theory and the diffraction approximation. The algorithm efficiency, in the presence of experimental noises, is studied. The results show that the technique is fast in convergence, stable against random noise and insensitive to the distribution of particles and the initial trial distribution.

Simultaneous measurement of film thickness, temperature, and mass fraction of urea-water-solutions by multi-wavelength laser absorption spectroscopy

Quantitative analysis for thickness, temperature, and mass fraction of liquid film is extremely crucial to the relevant industrial processes, but these parameters cannot be determined simultaneously by conventional measurement techniques. In the present work, a novel measurement method based on laser absorption spectroscopy was developed to measure the film temperature, thickness, and mass fraction of urea-water-solutions simultaneously by combining three wavelengths, 1420 nm, 1488 nm, and 1531 nm. Moreover, measurement accuracy of this method was validated by a calibration tool which provided liquid film with known film thickness, temperature, and mass fraction, respectively. It revealed that the deviation between the measured and known parameters with the developed method was 0.86%, 4.58%, and 3.85%, respectively.

Numerical prediction of ultrasonic attenuation in concentrated emulsions and suspensions using Monte Carlo method

HighlightsMonte Carlo method was proposed to characterized the ultrasound propagation.The method can be used in both single and mixed particle system.The effect of interaction between neighboring particles was probed.Ultrasonic attenuation of concentrated suspensions and emulsions was investigated. ABSTRACT For the study of predicting ultrasonic attenuation of mixed particles and probing the effect of interaction between neighboring particles, the Monte Carlo method was investigated to establish a submicron particle size characterization model in concentrated particulate two‐phase system and serve as a probability and statistics technique to evaluate the underlying ultrasonic events during the ultrasound propagation. The numerical simulation method was proposed to predict the ultrasonic attenuation characteristics in the two‐phase system of silica suspensions and corn oil‐in‐water emulsions with different particle sizes, ultrasonic frequencies and concentrations. Furthermore, an extension of the well‐established single‐particle theory of Epstein‐Carhart and Allegra‐Hawley (ECAH) was carried out, by incorporated in the couple phase model from a hydrodynamic point of view and effective hypothesis both accounted for the ultrasonic wave overlapping effect for the close proximity of particles. The simulation result shows agreement with the results of the ECAH model, the Lloyd & Berry (LB) model and the Waterman model in the dilute limitation, corresponding to glass beads and silica particles respectively. Afterwards, such a method was then applied into mixed particle system, where the mixed iron particles and glass beads with various ratios were set as examples for the purpose of predicting ultrasonic attenuation for the mixed particle systems. After comparing with the experimental results, it is shown that as a function of frequency, the variation of the ultrasonic attenuation coefficient with different mixing ratio manifests a nonlinear tendency. Also noteworthy is that the physical properties of particles play a dramatic impact in influencing ultrasonic attenuation. At higher concentrations, it was validated both in two‐phase system of silica suspensions and corn oil‐in‐water emulsions that the attenuation predicted by Monte Carlo method agreed well with the experimental results of literature, yielding a theoretically increasing but less than linear expected attenuation with particle concentration. Particularly, the critical concentration of deviation from the linear change was obtained and interpreted using the thermal and viscous overlapping theory. The proposed Monte Carlo method presents a novel approach in calculating the attenuation in high particle volume concentration of more than 40% and provides a numerical modeling of particle size measurement in the complex particle‐particle interaction condition.

A novel method for plastic particle sizing in suspension based on acoustic impedance spectrum

&NA; The objective of this paper is to explore the relationship between the characteristics of plastic particles in suspension and acoustic impedance spectrum and to present a novel non‐invasive methodology for both spherical and non‐spherical particle sizing. By modifying the ultrasonic attenuation spectral model, theories relating acoustic impedance spectrum to particle characteristics have been established to implement quite a few numerical simulations for the first time, revealing that the acoustic impedance of plastic particles is sensitive to changes in particle concentration and size. Afterwards, experiments were carried out on polystyrene suspensions made by particles with different sizes. On the basis of the theoretical analysis, different transducers were employed over a frequency varied from 10 MHz to 100 MHz for different particle sizes respectively. Not only were spherical particles chosen for the experiment, but also non‐spherical particles with three different size distributions considering the fact that practical particles have irregular shapes. All the samples were verified by optical microscope technique and their comparisons with the experimental results show that the plastic particles with different sizes are distinguishable by using acoustic impedance spectrum. HighlightsA plastic particle sizing method based on ultrasonic impedance is proposed.The transducer is located in the bottom of the sample cell.Concentration can barely exert influence on particle size characterization.The method can be applied to both spherical and non‐spherical particles.

Measuring Particle Size and Concentration of Dense Slurry By Ultrasonic Method

Two independent ultrasonic methods for particle size and concentration of dense slurry are presented in this paper. The concentration can be obtained by ultrasonic multiple echo reflection method, which utilize the multiple reflections within the stainless steel wall to determine the acoustic impedance, velocity, density of the slurry. The particle size distribution is determined by ultrasonic attenuation spectrum method. The relationship between the particle size and ultrasonic spectra is established through a combination of a scattering model and the couple-phase model. An inversion algorithm based on optimum regularization factor is also discussed. For the purpose of on-line characterizing dense Coal-water slurry, with the set-up developed in IPTFM, the concentration and particle size distribution of coal-water slurry are measured by these two methods. The ultrasonic technique presented in this work brings the possibility of using ultrasound for on-line measurement of dense slurry.

Measurement of Particle Size Distribution and Volume Concentration based on Ultrasonic Attenuation Spectrum in Fat Emulsion

The determination of particle size distribution in concentrated polydisperse fat emulsions measured by ultrasonic attenuation spectrum is studied in this paper. Based on theoretical analysis, ultrasonic attenuation spectrum of fat emulsion samples containing different droplet concentrations (1∼20%) is measured over the range of 2∼13MHz. Then the droplet size and distribution are determined by processing the experiment data with inversion arithmetic. The particle size distribution of original sample determined by ultrasonic spectrum gives excellent agreement with that of diluted sample measured by an optical instrument TSM(Totally Scattering Measurement). This indicates that ultrasonic spectrum is capable of determining the particle size distribution and dispersed‐phase volume fraction of concentrated fat emulsions in a non‐destructive approach.