Analysis of the effect of dual injection on combustion characteristics of Gasoline Direct Injection (Gdi) Engine

Abstract

The production of hydrocarbons (HC), carbon dioxides (CO2) and nitrogen oxides (NOX) are the serious issues of Gasoline Direct Injection (GDI) during stratified lean operation. In attempt to solve these setbacks, this research explores the effect of dual direct injection on air-fuel mixture characteristics, combustion and species transport characteristics after combustion at both early and late fuel injection modes. The researcher used the 2021 ANSYS design modeler for geometry designs and meshing and used the ANSYS Fluent for simulation and numerical analysis. The results revealed that during mixture preparation phase dual injection at early injection results in higher TKE, velocity magnitude, turbulent intensity, dissipation rate but lower turbulent viscosity than when the fuel was injected late. The combustion and species transport results also revealed that at late injection, specific heat capacity (Cp) and its equivalent flame temperature was high enough to initiate dissociation of combustion products into O2, N2, HC and CO as compared to when the fuel was injected early. The turbulent burning velocity of the flame was 2290m/s at late injection while that during the early injection mode was 397m/s. Post combustion mass fraction results showed the presence of O2 and N2 in the combustion chamber in the late injection as against zero O2 and N2 in the early injection mode. Mass fractions of NOX and CO2 production were also high during late injection than in the early injection. The mass fraction of H2O vapour produced in the early injection was higher than that of the late injection mode. The study reveals that dual direct injection engine operated at early injection mode is more efficient in mixture preparation and dissipation, engine cooling effect and reduced exhaust NOX and CO2. It is therefore recommended that automotive companies in Ghana should consider the efficiency of dual direct GDI engine for emission control and fuel economy for incorporation into the Ghana-made vehicles to support Ghana’s industrialization drive.