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.
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.
Xiaozhen ChenWu ZhouXiaoshu CaiMingxu SuHailong Liu
