Particle emissions have been generally associated to diesel
engines. However, spark-ignition direct injection (SI-DI) engines
have been observed to produce notable amounts of particulate matter
as well. The upcoming Euro 6 legislation for passenger cars
(effective in 2014, stricter limit in 2017) will further limit the
particulate emissions from SI engines by introducing a particle
number emission (PN) limit, and it is not probable that the SI-DI
engines are able to meet this limit without resorting to additional
aftertreatment systems.
In this study, the solid particle emissions of a SI-DI passenger
car with and without an installed Particle Oxidation Catalyst
(POC®) were studied over the New European Driving Cycle (NEDC) on a
chassis dynamometer and over real transient acceleration situations
on road. It was observed that a considerable portion of particle
number emissions occurred during the transient acceleration phases
of the cycle. The application of the POC resulted in a reduction of
those emission peaks and, as a conclusion, the car was able to meet
the 2017 Euro 6 particle number emission limit with the POC.
The on-road measurement confirms the results obtained on the
chassis dynamometer in that the majority of particle number
emissions associated with SI-DI engines arise from transient
acceleration situations. The POC efficiency was verified also on
road by significantly reducing the particle number emission peaks
caused during accelerations.