Fuel Pressure and Charge Motion Effects on GDi Engine Particulate Emissions

The focus of this study is investigation of the influence of fuel system pressure, intake tumble charge motion and injector seat specification - namely the static flow and the plume pattern - on the GDi engine particulate emissions under the homogenous combustion operation. The paper presents the spray characteristics and the single cylinder engine combustion data for the Delphi Multec® 14 GDi multi-hole fuel injector, capable of 40 [MPa] fuel system pressure. It provides results of a study of the influence of fuel pressure increase between 5 [MPa] to 40 [MPa], for three alternative seat designs, on the combustion characteristics, specifically the particulate and gaseous emissions and the fuel consumption. In conjunction with the fuel system pressure, the effect of enhanced charge motion on the combustion characteristics is investigated. The combustion data shows a systematic effect of fuel pressure increase on reduction of the combustion particulate emissions due to improvement of mixture homogeneity and reduction of tip diffusion flame. The effect of enhanced intake charge motion is a further reduction of particulate emissions for fuel pressures in the range of 20 [MPa] to 40 [MPa]. Injector seat specification exerts an independent influence. The results illustrate a complex relation of the fuel system pressure, the injector specification and the charge motion with the combustion characteristics.