Fuel System Pressure Increase for Enhanced Performance of GDi Multi-Hole Injection Systems

The progressive trend towards the GDi engine downsizing, the focus on better fuel efficiency and performance, and the regulatory requirements with respect to the combustion emissions have brought the focus of attention on strategies for improvement of in-cylinder mixture preparation and identification and elimination of the sources of combustion emissions, in particular the in-cylinder particulate formation. This paper discusses the fuel system components, injector dynamics, spray characteristics and the single cylinder engine combustion investigation of a 40 [MPa] capable conventional GDi inwardly-opening multi-hole fuel injection system. It provides results of a study of the influence of fuel system pressure increase between 5 [MPa] to 40 [MPa], in conjunction with the injector static flow and spray pattern, on the combustion characteristics, specifically the particulate and gaseous emissions and the fuel economy. The combustion data shows the marked effect of fuel pressure increase on reduction of the combustion emissions and improvement of fuel consumption. It also illustrates an influence of the injector specifications that is evident at all system pressures. The data highlights the complex relation of the fuel system pressure, the injector specifications and the combustion characteristics, which must be taken into consideration for GDi homogeneous combustion system optimization.