Authors
Cheng, M. D., Storey, M. J., Waiman, T., and Dam, Q. T.
Publication
Journal of Aerosol Science, Volume: 33, Issue: 3 March, 2002, pp. 491-502
Abstract
The purpose of this investigation was to determine if turbulent
mixing created by the ejector causes change in the size distribution
of particles passing through it. The results using dry solid sodium
chloride (NaCl) particles show no discernible difference in the geometric
mean diameter and the geometric standard deviation of particles passing
through the ejector. Similar results were found for the dioctyl-phthalate
(DOP) particles. In other words, there was no apparent shift in the center
and spread (measured by the geometric standard deviation) of the particle
size distributions. The ratio of the total number concentrations before
and after the ejector indicates a dilution ratio of approximately 20
applies equally for both DOP and NaCl particles. The result suggests
the dilution capability of this ejector was not affected by the particle
composition. When the variability of the particle counts (in coefficient
of variation, CV) in individual size ranges was examined, we found that
the bin-to-bin variability was much greater for DOP than for NaCl particles.
Although the first and second moments of a distribution (i.e., the geometric
mean diameter and geometric standard deviation) were not altered significantly
for the DOP particles by the ejector, the skewness measure indicated otherwise.
The ejector may modify the particle size distribution of deformable particles
such as DOP. The results suggest that it may be difficult to precisely
characterize the size distribution of particles using the ejector technique
if the particle is not solid. This result has an implication for the use of
the ejector as a dilution tool, and one needs to know that the particles to
be diluted with such a device are reasonably dry and/or non-deformable under
the turbulent condition inside the ejector.
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