Investigation of High Fuel Pressure and Multiple Injection to Reduce Engine Emission during Catalyst Light-Off

The demand for clean energy efficient transportation is rapidly increasing to meet greenhouse gas emissions reduction and promote sustainability. Gasoline direct injection engines (GDI) have high thermal efficiency thus low greenhouse gas emissions compared with conventional port fueled engines. However, during cold start conditions GDI engines produce harmful emissions, including nitrogen oxides, hydrocarbons, and particulate matter. Thus, high pressure fuel system development for direct injection of gasoline is being conducted to reduce emissions during engine cold start. This paper summarized the effect of high fuel pressure and multiple injections on cold catalyst light-off strategy for rapid heating of the catalyst. Experiments were carried out using light-duty four-cylinder engine at cold catalyst light-off conditions with coolant temperature at 30 °C. Fuel injection strategy optimization was carried out considering (a) 25 MPa - two injections (b) 25 MPa - three injections and (c) 35 MPa - three injections, and engine emission, combustion stability, as well as fuel consumption data analyzed for each case. Experimental results show that 25 MPa and 35 MPa fuel injection pressure with three injection pulse have 60% and 80% reduction of HC and NOx combined relative to 25MPa fuel injection pressure and two injection pulse. It is expected that the improved homogeneous mixing realized by controlling spray penetration with multiple injections as well as the better spray atomization due to high fuel pressure, led to further HC reductions in the presence of high internal residual gases. Moreover, it has been also found that the combustion stability, and fuel consumption were similar for all three cases considered in this study. Experimental results show the benefits of using high pressure fuel injector with multiple injection strategies to realize reductions in engine emissions.