Numerical Investigation of the Potential of Late Intake Valve Closing (LIVC) Coupled with Double Diesel Direct-Injection Strategy for Meeting High Fuel Efficiency with Ultra-Low Emissions in a Heavy-Duty Reactivity Controlled Compression Ignition (RCCI) Engine at High Load 2019-01-1166

In this study, the potential of diesel/gasoline RCCI combustion equipped with late intake valve closing (LIVC) combined with double direct injection strategy for meeting high fuel efficiency with ultra-low emissions was investigated. The study was aiming at high load operation based on a heavy-duty diesel engine. The RCCI combustion was realized by port injection of gasoline and in-cylinder direct injection for the formation of stratified reactivity of the in-cylinder charge. Moreover, with the employment of double injection of diesel fuel, the concentration stratification of the high-reactivity fuel was obtained, which is to further realize effective control of the combustion phasing, pressure rise rate. Meanwhile, the employment of LIVC strategy is to control the maximum in-cylinder pressure and NOx emissions. In the numerical optimization, by coupling KIVA-3V code with genetic algorithm (GA), six operating parameters including premix ratio (PR), start of first injection (SOI1), start of second injection (SOI2), mass fraction of the first fuel injection, exhaust gas recirculation (EGR) rate, and intake temperature (Tin) were optimized to realize simultaneous minimization of fuel consumption, NOx and soot emissions. The simulated optimization was performed based on a Caterpillar 2.44 L heavy-duty diesel engine with a stock geometric compression ratio of 16.1. The engine speed was fixed at 1737 r/min, and the IMEP was around 18 bar. The results indicate that the combination of LIVC with double direct injection strategy can realize Euro 6 standard and high thermal efficiency for the heavy-duty RCCI engine at high load. With the comparison to the previous optimization for single injection, the necessity of double direct injection was demonstrated.