Measurement of Sub-23 nm Particles Emitted from PFI/DI SI Engine Fueled with Oxygenated Fuels: A Comparison between Conventional and Novel Methodologies

This study focuses on the measurement of sub-23 nm particles emitted from a small DI/PFI spark ignition engine through conventional techniques and innovative systems. Measurements were performed with well-known systems, such as the EEPS coupled to a PMP-compliant sample conditioning device. Moreover, a novel instrument developed within the European project Sureal-23, the advanced HM-DMA, capable of operating with a simplified conditioning setup was used. The engine was fueled with ethanol, both pure and in blend at 30% v/v. The effects of fuel on the particle emissions were analyzed at different operating conditions. The results highlighted that a larger fraction of emissions consists of particles smaller than 23 nm, and their number changes according to the fuel, injection strategy and operating condition. A significant effect of the sampling system conditions was observed reveling the inception of nucleation mode particles or the condensation of the volatiles onto existing particles depending on the combination fuel/injection strategy. Different trends were noted at certain operating conditions between the results from the EEPS and the advanced HM-DMA ascribable to the different measurement principle and to the dilution system.