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It has been reported that particulate emissions from diesel vehicles could be associated with damaging human health, global warming and a reduction in air quality. These particles cover a very large size range, typically 3 to 10 000 nm. Filters in the vehicle exhaust systems can substantially reduce particulate emissions but until very recently it was not possible to directly characterise actual on-road emissions from a vehicle. This paper presents the first study of the effect of filter systems on the particulate emissions of a heavy-duty diesel vehicle during real-world driving. The presence of sulfur in the fuel and in the engine lubricant can lead to significant emissions of sulfate particles < 30 nm in size (nanoparticles).

Particle emissions from four spark ignition engines were measured during steady state and transient chassis dynamometer tests. Transient Unified Drive Cycle tests were conducted at 0 °C and room temperature. Particle number, size distribution, active surface area, and photoelectric activity were determined. The results generally show low emission values for steady state operation of the warm engine. High particle concentrations are emitted in the first phase of the high-speed steady state testing. Once the engine is warmed up high emissions mainly occur during transient operation phases. The formation of nucleation mode particles is favored by the low concentration of carbonaceous soot, which offers volatile material little surface area for condensation.