Phase‐Doppler Anemometry with the Dual Burst Technique for measurement of refractive index and absorption coefficient simultaneously with size and velocity

Abstract

The principle of the dual burst technique (DBT) based on phase-Doppler anemometry (PDA) is proposed for simultaneous particle refractive index, size and velocity measurements. This technique uses the trajectory effects in PDA systems to separate the two contributions of the different scattering processes. In the case of forward scattering and refracting particles, it is shown that from the phase of the reflected contribution, the particle diameter can be deduced, whereas from the refracted contribution the particle refractive index and velocity can be obtained. Furthermore, the intensity ratio of these two scattering processes can be used for absorption measurements. Simulations based on generalized Lorenz-Mie theory and experimental tests using monodispersed droplets of different refractive indices and absorption coefficients have validated this technique.

Characterization of spray formation from emulsions by pressure-swirl atomizers for spray drying

“…Efforts to determine the refractive index of the drop liquid resulted in extended phase-Doppler anemometry (EPDA) (Pitcher et al, 1990;Naqwi et al, 1991a,b;Brenn and Durst, 1995). An alternative special version of a PDA system developed in the course of that research was the Dual-Burst PDA (D-B PDA) (Onofri et al, 1996). Making best use of the Gaussian intensity distribution of the irradiated light in the probe volume of the PDA system by measuring relatively large drops with a small probe volume, dual bursts were obtained for each individual drop travelling through the probe volume.…”

Phase Doppler Measurements with Compact Monoblock Configurations

“…The analysis of the scattering process is often carried out by using geometrical optics. A refined analysis is better carried out by using the generalized Lorenz-Mie theory (GLMT) [4] as exemplified in [5][6][7]. In the present case, the use of the GLMT appears essential, in particular because the behavior of a backward phase Doppler setup is strongly dependent on the refractive index of the particles.…”

“…This processing gives us the opportunity to track the phase difference behavior during each processed signal, similarly as in the dual-burst technique [7]. When particles are spherical and small enough, phase differences exhibit a top-hat shape, as exemplified in Figure 11.…”

Critical Angle Refractometry for Simultaneous Measurement of Particles in Flow: Size and Relative Refractive Index

“…Onofri et al [11] proposed in 1994 the use a dual burst technique (DBT) to obtain the same parameters with in addition the possibility of measuring the imaginary part of the particle refractive index (i.e. absorption, which may be useful for droplet evaporation studies, and material recognition) [12] or the measurement of coated [13] and heterogeneous particles [14]. These techniques have been applied to particle material recognition [11±14] and the study of spray interaction [9,10].…”

“…The reduction of the sensitivity of this technique owing to the socalled``trajectory effects'' and its applicability for con®ned ows have been greatly improved by the development of dual mode phase Doppler anemometer (DM-PDA) for refractive index measurements [10]. Onofri et al [11] proposed in 1994 the use a dual burst technique (DBT) to obtain the same parameters with in addition the possibility of measuring the imaginary part of the particle refractive index (i.e. absorption, which may be useful for droplet evaporation studies, and material recognition) [12] or the measurement of coated [13] and heterogeneous particles [14].…”