Investigation of sub 23 Nanometer Particles to Overall Count in Gasoline Engines

Gasoline direct injection (GDI) engines are becoming the new standard in engine technology; the reduction in fuel consumption, engine size and increase in power have made it so within the next year, GDI will replace the current port fuel injection (PFI) method with regards to global market share. The benefits that come with GDI are accompanied with some penalties in particulate number (PN) emissions. The relocation of the fuel injector causes a reduction in fuel and air mixing time, leading to a dramatic increase in PN when compared to the previous technology. As of September 2017, GDI powered vehicles have been limited to 6x10^11 Particles/km. Current legislation also limits the size of these particles. Presently, the only size considered are those of 23nm (Nanometers) and above. As the world moves towards a more health conscious and environmentally friendly society, this range in size is thought to be going down to at least 10nm for the next set of regulations. Existent PN measuring instruments are therefore set with a cutoff of 23nm, and homologation tests are carried out in laboratory settings. Multiple GDI and one PFI engines were tested in North American and European facilities. it was found that the fuel is a major contributor to particles larger than 23nm during aggressive transients, accounting for as much as 81% of the total count during these periods. Oil consumption also seems to correlate with particles larger than 23nm , as observed by the increase of this size range throughout the performance of two different drive cycles. Lastly, instruments that used particle charging such as the DMS500 by Cambustion or the ICAD (Induced Current Aerosol Detector) were found to have a difference in percentage as low as 30% when compared to their CPC (Condensation Particle Counter) counterparts.