Characterization of sub-23 nm particles and their measure for PFI/DI SI engines fueled with gasoline, ethanol and blend.

Particulate matter (PM) pollution in urban area is mainly due to internal combustion engines. PM are linked to hazardous health effects, and it is more dangerous as smaller are the particle size. The current emissions legislation introduced a number limitation only for particle larger than 23 nm. The sampling procedure as indicated by the PMP aims, in fact, to remove volatile particles smaller than 23 nm. There are many evidence on emissions of sub-23 nm particles. The nature of these particles is not well understood and their measurement is very sensitive to dilution conditions. A comprehensive characterization of their nature can help to define a well-consolidated procedure for their measurement. In this paper the effect of the sampling conditions on the emissions of sub-23 nm particles was analyzed. The investigation was performed on a small displacement PFI/DI SI engines fueled with gasoline, ethanol and blend of ethanol and gasoline. Particle size distribution and number concentration were measured on-line with an EEPS and an advanced DMA.