In-line imaging measurements of particle size,velocity and concentration in a particulate two-phase flow

A novel method is developed for in-line measurements of particle size, velocity and concentration in a dilute, particulate two-phase flow based on trajectory image processing. The measurement system consists of a common industrial CCD camera, an inexpensive LED light and a telecentric lens. In this work, the image pre-processing steps include stitching, illumination correction, binarization, denoising, and the elimination of unreal and defocused particles. A top-hat transformation is found to be very effective for the binarization of images with non-uniform background illumination. Particle trajectories measured within a certain exposure time are used to directly obtain particle size and velocity. The particle concentration is calculated by using the statistics of recognized particles within the field of view. We validate our method by analyzing experiments in a gas-droplet cyclone separator. This in-line image processing method can significantly reduce the measurement cost and avoid the data inversion process involved in the light scattering method.

Particle sizing in dense two-phase droplet systems by ultrasonic attenuation and velocity spectra

Size and size distribution of particles in particulate two-phase flow play an important role in a wide variety of industrial areas,while their measurement still remains a hard task till now.Ultrasonic wave as a mechanical vibration contains plenty of information about medium when it passes through.Thus the size distribution could be extracted from the measured ultrasonic attenuation and velocity spectra by means of well established models and data processing techniques.This paper contributes to the extraction of information of droplet size of a two-phase fat emulsion simultaneously from signals of broad-band ultrasonic attenuation and velocity spectra.According to the formulated single particle scattering model,the relationship between particle size distribution and ultrasonic spectrum is estab-lished.The sensitivities of ultrasonic spectra to the variation of particle size are illustrated.Distin-guishing features for attenuation and velocity spectra are summarized.Demonstration calculations of inversion by optimum regularization factor method are carried out to yield the typical numerical results for discussion.Based on the proposed inversion algorithm and theoretical model,a fat emulsion sam-ple with a volume fraction up to 20% is measured and analyzed.To validate the proposed ultrasonic spectrum particle sizing method,the results are compared to those obtained from optical measure-ment.

Modeling and prediction of ultrasonic attenuations in liquid-solid dispersions containing mixed particles with Monte Carlo method

We develop a theoretical model for predicting the ultrasonic attenuation in the liquid-solid system containing mixed particles. The ultrasonic attenuation coefficient is obtained by counting the number of phonons that reach the receiver. Using the Monte Carlo method (MCM), numerical simulations were performed to predict the ultrasonic attenuations with not only a single particle type but also monodisperse and polydisperse mixed particles. The simulation results for the systems with a single particle type were compared with various standard models. The results show that they agree well at relatively low particle volume concentrations (within 10%). For systems with mixed particles, the particle volume concentrati on was found to in crease to around 10%, and the variation of the ultrasonic attenuation agai nst the mixing ratio yields a nonlinear trend. Moreover, the ultrasonic attenuation is significantly affected by particle properties. The numerical results also show that both the particle type and particle size distribution should be carefully taken into account in the dispersions with polydisperse mixed particles, where the MCM can give a more direct description of the physics of sound propagation compared with the conventional models.

Fast nanoparticle sizing by image dynamic light scattering

In this paper, an image dynamic light scattering method for nanoparticle sizing is introduced. The spatial distribution of the scattered lights from nanoparticles undergoing Brownian motion was captured at a high frame rate by a digital camera within one second, which is considerably faster than the conven- tional photon correlation spectroscopy method. The captured series of photographs were meshed into thousands of small units for calculating the intensity autocorrelation functions in parallel. Experimental results from the measurements of three reference nanoparticle samples （27, 80, and 352 nm in diameters） demonstrated the feasibility of this method.

Three-dimensional positioning method for moving particles based on defocused imaging using single-lens dual-camera system

A method to three-dimensional position moving particles with one lens and two cameras is proposed. Two par- ticle images with different degrees of defocusing are adopted to solve the ambiguous problem of particle positions. A single-lens dual-camera system is developed to simultaneously capture these two images for the moving par- ticles. The measurement principles and theoretical analysis are introduced first, and then simulated investiga- tions and experimental research are discussed. The measurement errors in the simulations and experiments are less than 1% and 4%, respectively, in 20 times the depth of field of the system, which validates the feasibility of this method.

Resonance scattering characteristics of double-layer spherical particles

Based on the principle of ultrasonic resonance scattering, sound-scattering characteristics of double-layer spherical particles in water were numerically studied in this paper. By solving the equations of the scat- tering matrix, the scattering coefficient determined by the boundary conditions can be obtained, thus the expression for the sound-scattering function of a single double-layer spherical particle can be derived. To describe the resonance scattering characteristics of a single particle, the reduced scattering cross section and reduced extinction cross section curves were found through numerical calculation. Similarly, the numerically calculated sound attenuation coefficient curves were used to depict the resonance scattering characteristics of monodisperse and poIydisperse particles. The results of numerical calculation showed that, for monodisperse particles, the strength of the resonance was mainly related to the particle size and the total number of particles; while for polydisperse particles, it was primarily affected by the particle size, the coverage of the particle size distribution and the particle concentration.

Two-dimensional self-adapting fast Fourier transform algorithm for nanoparticle sizing by ultrafast image-based dynamic light scattering

In nanoparticle sizing using the ultrafast image-based dynamic light scattering (UIDLS)method,larger impurities and dark noise from the complementary metal-oxide-semiconductor (CMOS)detector affect measurement accuracy.To solve this problem,a two-dimensional self-adapting fast Fourier transform (2D-SAFFT)algorithm is proposed for UIDLS.Dynamic light scattering images of nanoparticles are processed using 2D fast Fourier transforms,and a high-frequency threshold and a low-frequency threshold are then set using the self-adapting algorithm to eliminate the effects of the dark noise of the CMOS detector and the impurities.The signals caused by the dark noise of the CMOS detector and the impurities are cut off using the high-frequency threshold and the low-frequency threshold.The signals without the high- and low-frequency components are then processed again using an inverse Fourier transform to obtain new images without the dark noise and impurities signals.The mean diameters of the measured nanoparticles can be obtained from images obtained using UIDLS.Five standard latex nanoparticles (46,100, 203,508,994nm)and commercial nanoparticles (antimony-doped tin oxide,indium tin oxide,TWEEN- 80,nano-Fe,and nano-Al2O3)were measured using this new method.Results show that 2D-SAFFT can effectively eliminate the effects of dark noise from the CMOS detector and the impurities.

Real prospects for the development of power technologies based on renewable energy sources in Poland

In Poland more than 40% of the power units have been operating for over 40 years now and more than 10% are over 50 years old, which indicates a high degree of decrease in the value of the energy sector. An analysis of the energy market shows that every year a new power plant should be built with a capacity of 1000 MW to ensure the national energy security. An energy market research indicates that in Poland the structure of energy production is changing in recent years-the share of fossil (solid) fuels in electricity and heat production was approximately 88% in 2009, while in 2004 it reached 93%. According to the analysis of the market, it can be seen that conventional energy, mainly based on coal and lignite, has been the most important segment of the sector for a long time. In this paper the prospects for the development of power technologies based on renewable energy sources (RES) in Poland are presented.