Development of pedagogical phase doppler anemometer for measuring velocity and size distribution of water droplets

Abstract

Particle size analysis is an essential analytical task in a large variety of processes of industrial and laboratorial relevance. Phase doppler anemometer (PDA) is one of well-established techniques allowing simultaneous measurement of velocity and size of particles, droplets, or bubbles in two-phase flows including spray atomization. The method is based upon the principle of light scattering interferometry. When a particle passes through the probe volume defined by the intersection of two laser beams, the phase of the light scattered by the particle carries information about the particle size, whereas its frequency provides the information of particle velocity. This research work has been devoted to the development of a one-dimensional PDA instrument by using He-Ne laser with wavelength of 632.8 nm and two detectors for measuring velocity and size distribution of water droplets generated by binary and ultrasonic nozzles. The calibration of the developed PDA with the transparent glass spheres of precisely known size was conducted before investigating the reliability and accuracy of the developed system by comparing the measurement results obtained from the developed with that of the commercial PDA instruments. It was found that the relative difference of the droplet mean velocity and diameter measured by the developed system were less than 15% and 25%, respectively. These results demonstrate the potential of the PDA instrument developed in this work