Comparison of Primary and Secondary Emissions from an Internal Combustion Engine - Novel Combustion Concepts for Sustainable Energy Development - page 409

Fig. 2 Schematic view of soot formation (Adopted from Particulate emissions from vehicles by
Eastwood, 2008 )

signi cantly higher values at a distance from the droplet surface. This leads to

heterogeneous fuel-air mixture inside the combustion chamber. Incomplete com-
bustion is a result of very low local excess air (less oxygen) ratio near the droplet.
The soot formation involves five steps: pyrolysis, nucleation, surface growth,

agglomerates and oxidation. Pyrolysis is largely dependent upon three factors: air-
fuel ratio, combustion chamber pressure and its temperature (Eastwood 2008 ).
Precursor molecules resulting from pyrolysis undergo nucleation process and form