A method for investigating the orientational behaviour of fibrous particles in gaseous flow

Abstract

A method is described by which the angular orientation distribution of fibrous particles carried in a gaseous stream may be investigated. The method is based upon the interpretation of the spatial intensity distribution or scattering profile of laser light scattered by individual fibres. The scattering instrument used to capture the profiles is described, and the mathematical computation required to ascertain the orientation of each particle at the measurement point is detailed. Illustrative results are given for a study of airborne micromachined silicon particles of 12 pm length and 1.0 pm by 1.5 pm cross-section. The method is currently being employed by the authors to investigate ways of improving the orientation control over nonspherical particles in systems such as aerodynamic particle sizers and particle shape classifiers, since lack of particle orientation control is known to adversely affect the measurement accuracy of both these types of instrument.

Shape Discrimination of Individual Aerosol Particles Using Light Scattering

“…The rod-shaped Silicon dioxide aerosol particles in Figure 7b tend to be distributed in the lower right corner of the ternary phase diagram, indicating that the intensity of scattered light of most rod-shaped Silicon dioxide particles at PMT1 position (corresponding horizontal direction in spatial orientation) is greater than that at PMT2 and PMT3 positions. The results also prove that the orientation of the rod-shaped particles tends to be parallel to the airflow in the injection flow, which is consistent with the conclusion of Hirst et al [32].…”