The phase-Doppler technique (PDA) has become one of the most important instrumental methods in two-phase flow research in recent years because of its capability of simultaneously determining the diameter and velocity of spherical particles. However, the shortcomings of this technique with respect to volume flux measurement have become increasingly apparent. In order to study the performance of different PDA instruments, comparative flux measurements in two characteristic sprays using a patternator and three phase-Doppler systems were performed at the Institut für Thermische Strömungsmaschinen of the University of Karlsruhe (ITS) in cooperation with the Lehrstuhl für Strö-mungsmechanik of the University of Erlangen-Nürnberg (LSTM) and DANTEC/invent Measurement Technology GmbH in Erlangen. The results of this study clearly indicate that especially in dense sprays, mass flux determination by the phase-Doppler technique is still critical. Further efforts to improve the reliability of the system and to identify the possible sources of errors are necessary. However, the dual-mode technique shows a significant improvement compared with the other instruments under investigation.

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Measurements of particle size distributions in multi‐phase flows with a phase‐Doppler anemometer yield incorrect results if polydisperse particles are investigated. For weighting biased size distributions, different in situ methods, requiring the size of the detection area, are known, but all of these weighting procedures are restricted to very small measuring volumes if off‐axis instrument configurations are considered. Moreover, the weighting functions have some disadvantages in the case of poor statistics in single size classes or the results are not suitable for determining the size of the detection area for particles which are larger than the beam waist. Therefore, the intention in this work was to measure the size of the detection area for different kinds of monodisperse particles, different instrument configurations and varied instrument sensitivities experimentally and to develop an improved weighting procedure that copes with the above difficulties. The application of the results obtained from the investigations with monodisperse particles to measured particle size distributions and volume flux densities of polydisperse water droplets in a spray cone of an atomizer confirms the applicability of this weighting procedure. It is still restricted to directed flows, perpendicular to the fringes.

In the experimental work reported here, laser Doppler anemometry was used for “point” measurements of bivariate distributions of velocity and drop size (LDVS), and diffraction sizemetry (DSM) was used for line-of-sight measurements of drop size in sprays of water. Laser light sheet photographs were used to determine the spray geometry. The measurement positions were chosen so that the mean axes of the horizontal spray planes containing the LDVS measurement points coincided with the axis of the DSM laser beam. In this case, experimental results of DSM and LDVS are comparable, if one takes into account the laws of the conversion of drop flux (LDVS results) into a drop concentration (DSM results). Mean diameters as well as cumulative distributions obtained by LDVS at different measurement locations are compared with corresponding DSM results. Advantages and disadvantages of both methods with respect to spray analysis are discussed.

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