High accuracy optical particle sizing in phase-Doppler anemometry

A novel structure for phase-Doppler anemometry (PDA) is proposed in order t o eliminate the measurement-volume effect (MVE). This new PDA system consis ts of four receiving detectors in an optimized optical orientation. The met hod for the determination of the optimized optical orientation angle is int roduced. In this method the vector sum of refractive and reflective rays is taken into consideration in describing a dual-mechanism-scattering model c aused by a nonuniformly illuminated PDA measurement volume. The constraint of the single-mechanism-scattering model in the conventional PDA is removed . As a result the error caused by MVE, which consists of a Gaussian beam de fect and a slit effect, can be eliminated. Analytical and experimental stud ies were conducted to investigate the accuracy of particle sizing using thi s new system. Both the experimental results and the simulation based on the generalized Lorenz-Mie theory show that the new method can provide a high- accuracy PDA system free of the MVE.