Particulate Characterization of a DISI Research Engine using a Nephelometer and In-Cylinder Visualization

A nephelometer system was developed to characterize engine particulate emissions from DISI engines. Results were correlated with images showing the location and history of particulates in the cylinder of an optical engine. The nephelometer's operation is based upon the dependence of scattered laser light on particulate size from a flow sampled from the exhaust of an engine. The nephelometer simultaneously measured the scattered light from angles of 20° to 160° from the forward scattering direction in 4° increments. The angular scattering measurements were then compared with calculations using a Mie scattering code to infer information regarding particulate size. Measurements of particulate mass were made based upon a correlation developed between the scattered light intensity and particulate mass samples trapped in a 0.2-micron filter.

Measurements were made in a direct injection single-cylinder spark ignition research engine having a transparent quartz cylinder. The engine was operated at a speed of 1000 rpm at partial load with both late and early fuel injection timings.

The nephelometer measurements were complimented with in-cylinder PM visualization using planar Mie scattering imaging. Correlations were attempted between the nephelometer engine-out PM measurements and the in-cylinder visualized PM.