M. Schneider et Ed. Hirleman, INFLUENCE OF INTERNAL REFRACTIVE-INDEX GRADIENTS ON SIZE MEASUREMENTSOF SPHERICALLY SYMMETRICAL PARTICLES BY PHASE DOPPLER ANEMOMETRY, Applied optics, 33(12), 1994, pp. 2379-2388
A model based on geometric optics for predicting the response of inter
ferometric (phase Doppler) instruments for size measurements of partic
les with radially symmetric but inhomogeneous internal refractive inde
x profiles is developed. The model and results are important for appli
cations in which heat or mass transfer from the particles or droplets
is significant, for example, in liquid-fuel combustion. To quantify th
e magnitude of potential bias errors introduced by the classical assum
ption of uniform internal properties on phase Doppler measurements, we
compute calibration curves for a sequence of times during the evapora
tion of a decane droplet immersed in an environment of T = 2000 K and
p = 10 bars. The results reveal considerable effects on the relation b
etween phase difference and droplet diameter caused by the refractive
index gradients present. The model provides an important tool to asses
s sizing uncertainties that can be expected when applying conventional
(based on uniform properties) phase Doppler calibration curves in spr
ay combustion and similar processes.