The Presence and Differentiation of the Scattering Mechanisms in PDA Systems with Respect to Particle Size and the Position of its Trajectory

Abstract

Phase Doppler anemometry, a popular method of spherical particle sizing, suffers from errors caused by violation of the presumption of refraction-dominated scattering. As an attempt to contribute to the numerous efforts of finding the solution of this problem, in this paper, first the scattering mechanisms in PDA systems are analyzed and then the validation principle differentiating the dominating scattering mechanism is proposed. This mechanism is based on checking the value of the ratio of the phase differences of the signals from two pairs of photodetectors placed at different off-axis scattering angles. A two-component system combining measurement of the scattering mechanism and measurement of the single scattering mechanism is recommended. Finally, the results of simulating measurement, with this system using the proposed validation principle are presented. They show that only 1.5% of particles passing through the measurement volume are not measured, which is a considerable improvement over the standard PDA systems and some reported ameliorations.