Influence of Physical and Chemical Parameters on Characteristics of Nano-scale Particulate in Spark Ignition Engine

This work attempted to correlate the ultra fine particulate count to the flame propagation time, in-cylinder peak pressure, and in-cylinder ageing time (the time the particulates stay inside the cylinder) of a throttle body gasoline injected engine. The engine was tested at different loads and speeds ranging from 20 Nm to 100 Nm and 2000 to 3400 rpm respectively. A fast particle spectrometer, a mass spectrometer, and an in-cylinder pressure measurement system were used to characterize the particulate emission. This work identified the correlation between the nucleation of particulates and rate of burning, the particulate count for particles size greater than 200 nm and the in-cylinder ageing time. It identified that an increase in engine load at constant speed increased the particle number density of the 10 nm diameter particles; the effect was less significant on the particles of diameter greater than 50 nm and almost absent on particles of diameter greater than 200 nm. As the speed increases from 2200 to 3400 rev/min at constant load, the fraction of the ultra fine particles of diameter up to 10 nm to the total particle number increases from 50% to 90%. It also identified the precursors that drive the nucleation of solid particles in spark ignition engines.