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To evaluate the potential of a dedicated LPG direct injection (LPDI) vehicle, we investigated several engine control parameters that are closely related to the characteristics of mixture preparation and nano-particle emissions. Many researches have pointed out that any amount of particle emissions from GDI vehicles were made during the cold start and cold transient phase. Therefore, in the study, four types of engine control strategies for the LPDI vehicle were applied to evaluate particle number (PN) concentration and regulated emissions in the cold start phase and the hot start phase under the FTP-75 cycle. The reduction rate of the PN concentration with LPG application reached approximately over 99% less than that of the GDI vehicle.

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 this study, present level of 2.0L GDI vehicle is measured and it is figured out how to reduce particle emissions against European emission limit(EURO 6) and US emissions standards(LEV 3) through engine test and vehicle test. A cause of PM and PN formation is divided into several reasons. This paper describes the optimization of engine control parameter and hardware change like injector type and injection target position like spray pattern optimization with minimizing side effect. If particle emission limit is getting more strengthen GPF(Gasoline Particle Filter) is a simple solution to meet particle emission limit. But engine performance decreases according to exhaust pressure increase and there is cost problem. This paper have shown that 60% level of euro6c PN limit is accomplished without a GPF at demonstrated vehicle.