MULTIDIMENSIONAL, NONHOMOGENEOUS, DENSE SPRAY CONTRIBUTIONS TO DIFFRACTION-BASED PARTICLE-SIZE DISTRIBUTION MEASUREMENTS

The effect of dense sprays on particle size measurement by laser-diffr action based techniques is examined for lag-normal distributions of pa rticles in multidimensional media. A Monte Carlo modeling technique is used to simulate scattering of light by particles, and general scatte ring phenomena are included by using Mie theory. The measurement error s in particle size distribution parameters due to multiple scattering are analyzed and compared to corrections previously presented for homo geneous planar media. The errors for measurements in homogeneous cylin drical media equal those for planar media with the same optical depth, but the cylindrical geometry requires the use of a scaled obscuration . Specifically, the obscuration is dependent on the size of the laser beam relative to the cylinder. Nonhomogeneities are examined in planar media and found to have no effect on the measured size distribution o r obscuration. In nonhomogeneous cylindrical media, measurement errors in particle size distribution parameters due to multiple scattering a re shown to be predicted by planar corrections for line-of-sight measu rements in sprays. Simulations done with wide beams result in measured distributions that are within acceptable accuracy limits of equivalen t homogeneous results, and multiple scattering biases can be corrected as if the medium were homogeneous.