Analysis of Soot Particles Emitted from a Modern Light Duty Diesel Engine Running in Different Operating Conditions using Field Flow Fractionation and Granulometric Techniques

摘要

Soot particles emitted from a light duty (LD) Volkswagen diesel engine running at different operating points (speed and torque levels) are analyzed for mean size determination using a laser-based three Wavelength Extinction Method (3-WEM). For this reason, collected soot samples are suspended using an appropriate sample preparation technique with optimized conditions of sonication as it revealed its effect on the soot mean particle size measured by 3-WEM.An online Scanning Mobility Particle Analyzer (SMPS) is also used to measure soot emission at identical engine operating points. Size values obtained from SMPS are lower than those of suspended soot samples obtained from 3-WEM. The size discrepancies are mainly related to the required sample preparation procedure employed for 3-WEM measurements. The engine operating points affect, differently, the size measurements obtained from SMPS and 3-WEM.Sedimentation Field-Flow Fractionation (SdFFF) is used for density determination of soot samples based on size measurements of fractions collected at peak maxima of fractograms using the off-line hyphenation with 3-WEM. It is assumed that a size dependent separation of soot particles occurred with a uniform particle density over the whole size distribution. An average density value is used for the conversion of soot fractograms to size distributions. Discrepancies are also found with size distribution profiles obtained from SMPS for the same engine operating points, due to the sample preparation procedure employed for SdFFF measurements.