Concurrent Quantitative Laser-Induced Incandescence and SMPS Measurements of EGR Effects on Particulate Emissions from a TDI Diesel Engine

A comparison of scanning mobility particle sizer (SMPS)
and laser-induced incandescence (LII) measurements of
diesel particulate matter (PM) was performed. The results
reveal the significance of the aggregate nature of
diesel PM on interpretation of size and volume fraction
measurements obtained with an SMPS, and the accuracy
of primary particle size measurements by LII. Volume
fraction calculations based on the mobility diameter
measured by the SMPS substantially over-predict the
space-filling volume fraction of the PM. Correction algorithms
for the SMPS measurements, to account for the
fractal nature of the aggregate morphology, result in a
substantial reduction in the reported volume. The behavior
of the particulate volume fraction, mean and standard
deviation of the mobility diameter, and primary particle
size are studied as a function of the EGR for a
range of steady-state engine speeds and loads for a turbocharged
direct-injection diesel engine. Both the
SMPS and LII techniques demonstrate good repeatability
and consistency with each other. Increasing the EGR
results in a sharp rise in the volume fraction of particulates
for all engine speeds and loads. At all speed and
load conditions the primary particle size decreases with
increasing EGR.