Fuel Droplet Behavior in a Cylinder under the Difference Co<sub>2</sub> Mole Fraction Conditions Controlled by Simulated-EGR in CI Engine

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Fuel Droplet Behavior in a Cylinder under the Difference Co₂ Mole Fraction Conditions Controlled by Simulated-EGR in CI Engine

Min, Se Hun / Suh, Hyun Kyu

The objective of this numerical study is to investigate the effect of CO₂ mole fraction controlled by simulated-exhaust gas recirculation (EGR) on fuel droplet behavior for simultaneous exhaust emissions reduction in compression ignition engine under early injection conditions. In the simulation, the intake air initial composition was changed to simulate the EGR with changing CO₂ mole fraction. To consider early injection conditions, start of energizing timing was changed. The results were analyzed in terms of spray tip penetration, Sauter mean diameter, evaporated fuel ratio, and fuel mass fraction distributions. When CO₂ mole fraction increased, spray tip penetration was decreased because the kinetic energy of the injected fuel droplet was reduced by the high density of CO₂ and SMD was decreased since the high density of CO₂ disturbed the fuel progress, which induced the fuel droplet to have low kinetic energy. In addition, when the start of energizing timing was before top dead center 23 degree and CO₂ mole fraction was 20 %, exhaust emissions were expected to simultaneously reduce because the rapidly evaporated fuel by the collision effect promoted the combustion, and it made to evaporate the formed liquid wall film, which may absorb the combustion temperature by the latent heat vaporization.