Response of Phase Doppler Anemometer systems to nonspherical droplets

Abstract

The Phase Doppler Anemometer (PDA) technique measures particle diameter assuming sphericity. A means for detecting nonsphericity has usually been implemented in commercial PDA systems to avoid sizing errors if the sphericity assumption is not valid. In the present research the response of standard and planar PDA systems is examined experimentally in more detail by passing nonspherical droplets of known shape through the measurement volume. The effectiveness of nonsphericity detection schemes can be evaluated, and furthermore the influence of the droplet oscillations on the frequency and phase evolution of individual signals can be quantified. The light scattering from such particles has been simulated by using geometric optics, and the computed response of standard and planar PDA systems agrees well with the experimental observations. We conclude with some remarks concerning the possibilities of characterizing the nonsphericity with PDA systems.

Phase Doppler Measurements with Compact Monoblock Configurations

“…their shape is no longer spherical but closer to an ellipse. Such an effect has been described and studied previously [16]. This interpretation is confirmed by the fact that the slope distribution is also larger in Figure 15 than in Figure 13.…”

High-speed shadow imagery to characterize the size and velocity of the secondary droplets produced by drop impacts onto a heated surface

“…It has many advantages such as a high acquisition rate or the absence of calibration. However, one of its limitations concerns the reliability of its measurements in the presence of non-spherical droplets (Damaschke et al 1998). Statistical confidence can be a problem if only a limited fraction of the droplets are spherical.…”

Experimental Analysis of the Response of a Laser/Phase Doppler Anemometer System to a Partially Atomized Spray

“…Future work would require simultaneous on-line imaging and PDA data monitoring as discussed in [7] where a detailed analysis of the response of PDA systems to ellipsoidal droplets is presented. The conclusions presented above are in agreement with this earlier work; ellipsoidal droplets are not rejected by conventional three detector PDA systems.…”