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ICLASS 94<br>Proceedings of the Sixth International Conference on Liquid Atomization and Spray Systems

ISBN:
978-1-56700-019-1 (Print)
978-1-56700-445-5 (Online)

THEORETICAL STUDIES ON THE INFLUENCE OF REFRACTIVE INDEX GRADIENTS WITHIN MULTICOMPONENT DROPLETS ON SIZE MEASUREMENTS BY PHASE DOPPLER ANEMOMETRY

Reinhold Kneer
Institute of Heat and Mass Transfer, RWTH Aachen University, Augustinerbach 6, 52056 Aachen, Germany

M. Willmann
Lehrstuhl und Institut fur Thermische Stromungsmaschinen, Universtät Karlsrahe, Germany

M. Schneider
Arizona State University, Tempe AZ, USA

D. Hirleman
Arizona State University, Tempe AZ, USA

Rainer Koch
Lehrstuhl und Institut für Thermische Strömungsmaschinen Unversität Karlsruhe, Karlsruhe, Germany

S. Wittig
Universitat Karlsruhe (TH) Karlsruhe, Germany

Abstract

The response of a phase Doppler instrument has been predicted for the sizing of evaporating multicomponent droplets. This study uses the theoretical model of Schneider and Hirleman [1] and extends its application to droplets consisting of liquid mixtures. The results obtained for binary heptane/dodecane droplets are discussed for different scattering angles. The internal refractive index gradients considerably affect the relation between phase difference and droplet diameter at mean scattering angles of Θ = 30° and Θ = 160°. However, the absolute variations of the calibration curves are smaller compared to those observed for a single component droplet. Additionally a mean scattering angle of Θ = 70° has been investigated. These results clearly demonstrate the insensitivity of the Θ = 70° scattering configuration on internal refractive index variations and thus confirm the recommendation of Pitcher et al. [2] ,who considered minimizing errors due to unknown but homogeneous refractive indices.