Experimental Investigation on the Effects of Cooled Low Pressure EGR and Water Injection on Combustion of a Turbocharged GDI Engine 2020-24-0003

This work focuses on the effects of cooled Low Pressure EGR and Water Injection observed by conducting experimental tests consisting mainly of Spark Advance sweeps at different cooled LP-EGR and WI rates. The implications on combustion and main engine performance indexes are then analysed and modelled with a control-oriented approach, showing that combustion duration and phase and exhaust gas temperature are the main affected parameters. Results show that cooled LP-EGR and WI have similar effects, being the associated combustion speed decrease the main cause of exhaust gas temperature reduction. Experimental data is used to identify control-oriented polynomial models able to capture the effects of LP-EGR and WI on both these aspects. The limitations of LP-EGR are also explored, identifying maximum compressor volumetric flow and combustion stability as the main ones. The potential synergy of using both LP-EGR and WI is investigated by performing EGR and WI sweeps both separately and simultaneously, observing that their effects can be mainly considered additive.