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In this work, laser-induced incandescence (LII) and light scattering measurements are explored as means for the quantitative measurement of soot characteristics in a D.I. Diesel engine. Simultaneous, planar LII and light scattering signals from soot in an ethylene diffusion flame were imaged and calibrated against well-established data from laminar diffusion flame studies. The resulting calibration was transferred to results from an optically-accessible D.I. Diesel engine. Application of light scattering theory to the engine data produced planar images of the soot volume fraction, particle size and number density.

A study has been experimentally conducted in an optically-accessible DI Diesel engine operating on 50/50 mixture of iso-octane and tetradecane to evaluate a planar laser light scattering technique for the in-cylinder study of soot. Two simultaneous images, taken with vertically and horizontally polarized scattered light, were used to determine the polarization ratio, CHH/CW. This magnitude of the polarization ratio was employed to distinguish soot particles from fuel droplets. The spatial and temporal variations of soot during the combustion cycle were investigated with images taken at various crank angles and swirl levels at three different planes in the combustion bowl. For the high swirl case, soot was uniformly distributed in the combustion bowl. For the non-swirl case, however, soot was mainly observed near the wall and at the top plane, and was observed to exist later into the expansion stroke.