Performance and emission characteristics of reverse reactivity-controlled compression ignition (R-RCCI) engines: A comparative CFD/Chemical kinetics study with standard RCCI configurations

This study examines reverse reactivity-controlled compression ignition (R-RCCI) and compares it to conventional
RCCI using gasoline and diesel. In the R-RCCI mode, traditional reactivity stratification is reversed by utilizing
diesel as the port-fuel injection and gasoline directly injected into the combustion chamber. Through computational fluid dynamics (CFD) simulations coupled with chemical kinetics modeling, the research examines in cylinder pressure, temperature, heat release, and emissions under varying intake temperatures (348 K, 378 K,
and 408 K) and injection strategies (single and split). The results reveal that split injection R-RCCI with 348 K
intake temperature achieves up to a 16.55 % reduction in nitrogen oxide (NO) emissions compared to RCCI,
owing to its more distributed combustion process. Additionally, hydrocarbon (HC) emissions are reduced, driven
by enhanced oxidation in low-temperature regions. Split injection in R-RCCI further improves combustion stability, lowering peak cylinder pressures by approximately 11 % at elevated intake temperatures. In contrast,
while RCCI facilitates faster combustion, it generates higher NO emissions and exhibits a greater tendency toward knock under similar conditions. These findings highlight R-RCCI’s potential to optimize the trade-off between engine performance and emissions, offering a promising low-emission alternative to conventional RCCI
systems.