Experimental and computational fluid dynamics analysis on the influence of fuel injection pressure on engine's behavior of a gasohol based gasoline direct injection engine

This work examines the impact of fuel injection pressure (FIP) on engine's behavior of a multi cylinder gasoline direct injection (GDI) engine using gasohol (85% gasoline+15% ethanol by mass) as fuel. The FIP was varied from 90r to 120 bar at 10 bar intervals with the fuel injection timing 320° before top dead center (BTDC). experiments were performed at variable power at a constant speed of 2500 rpm. Computational fluid dynamics (CFD) simulations were carried out for the above said conditions to understand engine's behavior. Considering the conventional FIP (i.e.90 bar), increasing the FIP showed improvement in engine's brake thermal efficiency (BTE) up to110 bar. The maximum BTE was observed as 33.5% at the engine power output of 21 kW (where as it was 27.2% with the FIP of 90 bar). CFD results confirmed the improvement in the air-fuel mixing rate and swirl motion due to the increased FIP. The hydrocarbon (HC) and carbon monoxide (CO) emission were reduced with increased FIPs. CFD results on the HC and CO emissions indicated well agreement with the experiments. With the higher injection pressures, oxides of nitrogen (NOx) emissions showed an increase at all loads. The in cylinder pressure was observed to be higher with higher FIPs. It is concluded that increasing the FIP might improve performance and lower HC and CO emissions of a Gasohol based fuel in GDI engine. The optimized FIP of 110 bar could be recommended for the aforementioned engine's greatest performance without any modifications in the engine design while injecting the fuel at 320° BTDC. Increase in NOx emissions at higher injection pressure needs attention. The present study restricted the amount of ethanol as 15% by mass. Higher proportions of ethanol admissions require major modifications in the engine design.