PN emissions were measured using a 2012 1.6L gasoline direct injection (GDI) engine vehicle. The measurements were performed over NEDC using domestic fuel from South Korea and Euro 5 certification fuel, also FTP-75 cycle using domestic fuel and Indolene (official emission test fuel in the US).
Domestic fuel is the most volatile and has the least aromatics, Euro 5 certification fuel is the least volatile and has the most aromatics. Lower volatile gasoline generates more particle emissions due to diffusion combustion of fuel attached on the piston and fuel residues which are burned in its liquid form. Gasoline with more aromatic contents generates more particle emissions, too. Because aromatics have higher boiling point, lower vapor pressure and ring structures.
Fuel specification difference resulted in PN emission difference. In NEDC tests, result using Euro 5 certification fuel was 77.0% higher than the result using domestic fuel. In FTP-75 cycle tests, Indolene resulted in 20.8% higher than domestic fuel.
Mode tests using LPG were performed via the same vehicle. PN results using LPG over NEDC and FTP-75 cycle were 3 orders lower than the results from gasoline tests. This is due to high volatility of LPG.
From the test results, it is confirmed that PN emissions from the DI engine are significantly affected by fuel characteristics. Even if PN regulation is satisfied with one fuel, there is no guarantee that is satisfied with other fuels. But for the LPG direct injection engines, PN regulation could not be a problem.