A Laser-Based Technique for Particle Sizing to Study Two-Phase Expansion in Turbines

Abstract

Efficiency of binary power cycles can be improved by expanding the hydrocarbon working fluids through two-phase region in a turbine and exiting at saturated or superheated condition. This improvement can be achieved if there is no condensation during the expansion or if there is condensation, the droplet size is extremely small. In order to verify this, a particle sizing technique for extremely small particles in flow is needed. In this study, a laser-based technique is developed by which it is possible to detect particles as small at ten angstroms in size. The basis of the technique is that particles of size less than one third of the wavelength of the incident radiation will scatter according to Rayleigh scattering theory. According to this theory, the intensity of the scattered light will be the same in the forward as well as in the backward directions. Therefore, measurement of the scattered intensity at two or three different angles will confirm the presence of Rayleigh scattering. The size of the particles can, then, be calculated from the measured scattered intensity according to the Rayleigh scattering equation.